18 Heart and Mediastinum



10.1055/b-0034-75810

18 Heart and Mediastinum

Herzog\, Christopher

Mediastinum describes a space that extends between the thoracic inlet and the diaphragm and may be divided into an anterior, middle, and posterior compartment. Anterior refers to the space between the sternum and ventral pericardium, posterior to the space between the dorsal pericardium and posterior thoracic wall and middle to the remaining space in between, excluding the pericardium and pleural space. Although this subdivision is consistent in the lower mediastinum, it becomes arbitrary in the upper mediastinum (i.e., above the level of the heart), where many pathologic processes involve two or all mediastinal compartments. Tables 18.1 and 18.2 list all pathologic mediastinal processes. Any preferential or typical location is referred to in the comment section.


A typical, though most often nonvisible, mediastinal structure is the thymus, which lies ventrally to the anterior aortic arch. Being isodense to musculature in young children and adolescents, its density becomes fat equivalent after the age of 20 y. Thus, in older patients, the thymus is masked by mediastinal fat. On transverse scans, its maximum size should not exceed 1.8 cm in patients younger than 20 y and 1.3 cm in older patients. Thymic enlargement in adults commonly is observed along with hyperthyroidism, but it may also occur as a rebound phenomenon following steroid treatment and chemotherapy. The right and left lobes may be separate structures or be fused together; thus, the shape of the thymus is highly variable.


The pulmonary hilum is anatomically ill-defined and represents a depression on the mediastinal pulmonary surface where bronchus, blood vessels, and nerves enter the lung. The left and right pulmonary hila are asymmetrical and thus, because of vessel opacification, it is necessary to systematically analyze both to differentiate between vasculature, lymph nodes, and hilar masses.


Differentiation may be difficult, as masses and hilar or mediastinal lymph nodes often coexist. Nonpathologic mediastinal lymph nodes show a large central fat hilum and thus are barely visible on computed tomography (CT) scans. If visible, they appear as small oval structures, with a smallest to longest diameter ratio of < 1. Any cross-sectional diameter > 1 cm, nodal rounding, or diminishing of central fat is suspicious.


If correctly planed and performed, CT usually allows proper assessment of mediastinal and hilar structures. Any multidetector-row CT with ≥ 4 detector rows, ≤ 500 ms rotation time, and ≤ 2.5 mm collimator width is suitable. Sixty to 80 mL of ≥ 350 mg U/mL contrast media, injected at a rate of ≥ 3.5 mL/s and initiation of image acquisition 30 seconds after starting of contrast material injection, usually leads to sufficient vessel opacification. Although this approach usually allows for screening of pulmonary artery embolism, bolus triggering on the pulmonary artery is preferable in these patients.


With these technical requirements, adequate differentiation between nonvascular (Fig. 18.1) and vascular (Table 18.2) mediastinal diseases usually is easily achieved.


Many cardiac diseases may also be visible on conventional CT scans; thus, familiarity with normal cardiac anatomy is necessary for comprehensive assessment of the mediastinum.


Small amounts (> 25 mL) of pericardial fluid are typically observed in the retroaortic pericardial recess as a sickle-shaped, discretely hypodense finding dorsal to the root of the aorta (Fig. 18.1). Pericardial fluid may occasionally also be seen around the right cardiac auricles and in the vicinity of the apex of the heart.


Fluid collections > 50 mL constitute a pericardial effusion. Serous transudates are observed in congestive heart failure, hypoalbuminemia, or after irradiation: Lymph fluid may be secondary to neoplasm, cardiothoracic surgery, or obstruction of the hilum or superior vena cava. Fibrinous exudates occur in the presence of infections, uremia, collagen diseases, and hypersensitivity conditions. Hemorrhagic fluid collections may be iatrogenic following surgery or catheterization, traumatic, secondary to myocardial infarction (MI), metabolic (coagulopathy), or neoplastic (metastatic/primary cardiac neoplasms). CT attenuation values of hemorrhagic fluid approaches blood density (20–40 HU) and may show fluid–fluid levels (i.e., sedimentation of hemoglobin). The latter is indicative of a subacute/chronic state. Differentiation between serous and fibrinous effusions is usually not possible.


The contours of the heart are smoothed by a variable amount of subepicardial fat (Figs. 18.2 , 18.3), which must be differentiated from mediastinal lipomatosis (Fig. 18.23).


Conventional axial CT scans can be used to assess (1) overall size and shape of the heart and its chambers, (2) thickness of the myocardium, (3) presence of cardiac valve and coronary vessel calcifications, (4) topographic relationship between cardiac chambers and large vessels, (5) larger intracavitary masses, and (6) global patency of aortocoronary venous bypasses (ACVBs). Table 18.3 discusses cardiac abnormalities relevant to CT examinations of the chest.


Any further cardiac assessment requires dedicated CT scan protocols, which are beyond the scope of this book and may be found elsewhere in more detail. The most important technical requirement is coregistration of an electrocardiogram (ECG) signal during image acquisition, which can be done either retrospectively (ECG gating) or prospectively (ECG triggering). ECG gating provides continuous spiral CT datasets in combination with continuous ECG traces, and thus allows retrospective image reconstruction from any phase of the cardiac cycle. This strategy not only is robust in relation to cardiac motion artifacts, but also gives way for assessment of myocardial function. ECG triggering—or the step-and-shoot technique—provides prospective single-image acquisition from a predefined heart phase and thus a much lower radiation dose (up to < 1 mSv for a complete CT dataset of the heart) as compared with ECG gating (3–5 mSv). However, in arrhythmic or noncompliant patients, additional scanning may be required.


Coronary artery calcifications may be assessed and quantified with any multidetector-row CT scanner offering ≥ 4 detector rows, ≤ 500 ms rotation time, and ECG-gating or -triggering capability. Semimanual evaluation programs allow the calcium load to be quantified either according to the method described by Agatston or by simply determining total calcium volume. It is important to always consider the normal distribution of calcified plaques in patients of similar age and gender.

Fig. 18.1a–e Normal topography of the upper mediastinum as visualized after intravenous (IV) contrast administration. Structures just above the aortic arch (a). Thymus (b). Structures at the level of the aortic arch (c). Structures at the level of the tracheal bifurcation (d). Structures at the level of the left pulmonary artery, below the tracheal bifurcation (e).
































































AA


aortic arch


AO


aorta


AZ


azygos vein


BA


brachiocephalic artery


BV


brachiocephalic vein


CA


carotid artery


DA


descending aorta


E


esophagus


LAA


left atrial appendage


LPA


left pulmonary artery


PA


pulmonary artery


PCN


precarinal calcified nodes


PCR


pericardial recess


PTS


pretracheal space (with nodes)


RPA


right pulmonary artery


SPV


superior pulmonary vein


SVC


superior vena cava


TH


thymus


TR


trachea

Fig. 18.2 Normal pericardiac fat. The amount of fat (arrow) between the myocardium and pericardium varies.
Fig. 18.3a–e Cardiac anatomy on normal transverse scans. Level of the aortic root (a). Level of the left atrium (b). Level of aortic valve (c). Level of the mitral valve (d). Level of the right diaphragmatic cusp (e).




















































AO


aorta


AOV


aortic valve


IVC


inferior vena cava


LA


left atrium


LCA


left coronary artery


LV


left ventricle


MV


mitral valve


PM


papillary muscle


RA


right atrium


RAA


right atrial appendage


RCA


right coronary artery


RV


right ventricle


RVO


right ventricle outflow tract


SPV


superior pulmonary vein


SVC


superior vena cava



































































































































































































Table 18.1 Mediastinal and hilar lesions

Disease


CT Findings


Comments


Vascular


See Table 18.2 Mediastinal vascular disease


Inflammatory


Pancreatic pseudocyst


Fig. 18.4


Fibrous encapsulated fluid collection of inflammatory pancreatic exudate.


Diagnostic pearls: On precontrast scans, well-defined hypodense mediastinal cystic lesion is seen. Cyst walls may calcify. Low-density intracystic gas bubbles are seen in cases of secondary infection.


Evidence of pancreatitis may be present on abdominal CT in a patient with signs of chronic pancreatitis or following pancreas surgery/interventions.


Usually extends through the esophageal hiatus from the abdomen.


Nonspecific lymph node hyperplasia


Fig. 18.5


Lymph node hyperplasia in association with a variety of pulmonary or generalized infections.


Diagnostic pearls: Slightly enlarged, sharply marginated lymph nodes with homogeneous contrast attenuation.


CT appearance of hilar and mediastinal lymph nodes lacks specific morphologic appearance to serve diagnostic purposes.


Sarcoidosis


Fig. 18.6


Symmetric mediastinal and hilar lympadenopathy in patients with suspected sarcoidosis.


Diagnostic pearls: Enlargement of the paratracheal and preaortic lymph nodes in the upper mediastinum and symmetrical hilar lymphadenopathy are characteristic. Large conglomerates may occur. Calcifications are rare and occur late.


Lympadenopathy may occur with or without micronodular lung opacities, involving preferentially the middle and upper portions of the lung.


Histologically, well-defined granulomas with a rim consisting of fibroblasts and lymphocytes.


In the absence of characteristic pulmonary parenchymal changes, malignant lymphoma is an important differential diagnosis.


Pneumoconiosis


Inflammatory lung disease caused by a variety of organic and chemical antigens.


Diagnostic pearls: Lung manifestations often with associated minor enlargement of hilar and mediastinal lymph nodes. In patients with chronic exposition setting, lymph nodes show centripetal ringlike calcifications.


Lymph node changes are nonspecific, but pulmonary parenchymal findings are usually diagnostic.


Chronic granulomatous or sclerosing mediastinitis


Separate ends of a spectrum of chronic granulomatous inflammation of the mediastinum.


Diagnostic pearls: Lobulated, elongated soft tissue mass may be detected in any part of the mediastinum. Commonly contains calcification and is predominantly right-sided.


Caused by a long-standing inflammation of the mediastinum leading to growth of acellular collagen and fibrous tissue within the chest and around the central vessels and airways. Major airway or superior vena cava compression may be present.


May be associated with tuberculosis (TB), sarcoidosis, or a manifestation of idiopathic fibrosclerosis.


Has a different cause, treatment, and prognosis than acute infectious mediastinitis.


Megaesophagus


Fig. 18.7


Fig. 18.8


Characterized by > 10 cm luminal widening of the esophagus.


Diagnostic pearls: Often contains fluid or air–fluid level. Wall thickness > 3 mm when distended.


Underlying cause of megaesophagus is chronic or recurrent inflammation, such as achalasia, Chagas disease, scleroderma, and candidiasis in immunocompromised patients.


Tracheomalacia


Fig. 18.9


Fig. 18.10


Flaccidity of the tracheal support cartilage leading to focal tracheal collapse and concomitant cranial widening, especially when increased airflow is demanded.


Diagnostic pearls: Focal narrowing of the medial and distal trachea with dilation cranially to it; sometimes thickened walls within dilated tracheal segment.


Tracheomalacia has a variety of etiologies, including polychondritis, complication of tracheal intubation, tumors, foreign bodies, and congenital tracheal stenosis.


Physiologically, the trachea slightly dilates during inspiration and narrows during expiration.


These processes are exaggerated in tracheomalacia, leading to airway collapse on expiration. The usual symptom of tracheomalacia is expiratory stridor or laryngeal crow.


Congenital


Bronchogenic cyst


Fig. 18.11


A usually spherical cyst arising as an embryonic outpouching of the foregut or trachea.


Diagnostic pearls: Round or oval, well-defined, very thin-walled, nonenhancing near-water-density mass. Characteristic location is just below the carina, protruding toward the right. Contour may be affected by contact with more solid structures. Rarely calcifies.


Also referred to as bronchial cyst and usually asymptomatic unless it becomes infected.


Seen in different age groups from infants through adults. Can potentially be life-threatening, as cysts can lead to compression, hemorrhage, rupture, or infection.


Most common in the middle mediastinum; may occur in the posterior and occasionally in the anterior mediastinum. May contain viscous material and have a density up to 60 HU but usually does not enhance.


Pericardial cyst


Fig. 18.12


Usually asymptomatic, rare benign congenital anomaly in the middle mediastinum.


Diagnostic pearls: Round, smooth, thin-walled, nonenhancing mass of near-water density, most commonly located in the right cardiophrenic angle (middle or anterior mediastinum). May change shape when the patient is turned from supine to prone position.


Near-water attenuation differentiates pericardial cysts from lipomas and fat pads.


Incidence rate: 1/100,000. Occurs most frequently in the third or fourth decade of life and equally among men and women.


Pericardial cysts represent 6% of mediastinal masses, 33% of mediastinal cysts. Other cysts in the mediastinum are bronchogenic (34%), enteric (12%), thymic and others (21%). In the middle mediastinum, 61% of presenting masses are cysts. Pericardial and bronchogenic cysts share the second most common etiology after lymphomas.


Neurenteric cyst, gastroenteric cyst


Fig. 18.13


A combination of an endodermal cyst with a vertebral dysplasia.


Diagnostic pearls: Smooth, thin-walled, nonenhancing mass of near-water density in the posterior mediastinum. May contain viscous material and have a density near soft tissue but does not enhance.


Neurenteric cysts, along with Rathke cleft and colloid cysts, are endodermally derived lesions of the central nervous system (CNS). Spine anomalies may be associated.


Thoracic meningocele


Fig. 18.14


A closing disorder of the neural tube with herniation of the meninges through a vertebral column defect.


Diagnostic pearls: Well-defined, solitary or multiple, water-density paravertebral posterior mediastinal lesion. May appear bilateral. No enhancement after intravenous (IV) contrast administration. Enhances only after intrathecal contrast administration.


Most meningoceles occur in the lower lumbar region and manifest after birth. Occult meningoceles manifest later. Widening of the spinal canal and vertebral erosion is often associated.


Lymphangioma


Congenital malformation of lymphatic channels.


Diagnostic pearls: Anterosuperior mediastinal mass usually adjunctive with a larger component in the neck; multiloculated, homogeneous, smooth mass near-water density; often appears cystic. May compress nearby structures. Usually no attenuation on postcontrast scans.


Histologically, lymphatic sacs lined with endothelial cells, cavernous or cystic. Three to 10% of all cervical lymphangiomas extend into the mediastinum.


Classified into three subtypes: simple, cavernous, or cystic. May be asymptomatic in middle-aged persons. More common in male children/infants.


Cystic hygroma occurs in children and may be clinically apparent at birth or within 2 y.


Bochdalek herniation


Herniation through the lumbocostal triangle.


Diagnostic pearls: A low left-sided, rarely bilateral, posterior mediastinal mass is seen at a paravertebral location; enters into the chest between the chest wall and the spleen (see also Fig. 17.20).


May contain fat only, or rarely also bowel loops.


The most common congenital defect of the diaphragm. Bochdalek foramen is a lumbocostal triangle located posterolaterally. A hernia occurs in the presence of an incomplete closure of the pericardioperitoneal canals by the pleuroperitoneal membrane. A large Bochdalek hernia may be a rare cause of acute respiratory distress in neonates.


Traumatic


Pneumomediastinum


Fig. 18.15a, b


Extraluminal/pulmonary air within the mediastinum.


Diagnostic pearls: Mediastinal streaks or bubbles of air, often extending from/to the neck. May be associated with subcutaneous or pulmonary interstitial emphysema and/or pneumothorax.


More often spontaneous than traumatic.


Fracture of vertebra with hematoma


Paravertebral soft tissue mass associated with vertebral fracture (s).


Diagnostic pearls: Similar findings as in mediastinal hemorrhage or hematoma but usually confined to the posterior mediastinum.


Typically high-speed car accidents or falls.


Infectious


Tuberculosis (TB)


Lymph node enlargement due to an infection with mycobacteria tuberculosis.


Diagnostic pearls: Asymmetrically enlarged paratracheal and tracheobronchial lymph nodes in the acute phase. On postcontrast scans, lymph nodes often show peripheral enhancement and central areas of necrosis-related hypodensity. In subacute/chronic TB, lymph nodes may conglomerate and show speckled calcifications.


Characteristic pulmonary parenchymal changes are typically present (see also Fig. 16.39).


Acute mediastinitis, mediastinal abscess


Fig. 18.16


Acute mediastinitis is usually caused by bacterial overgrowth following a rupture of either the trachea or esophagus. It may progress rapidly into a mediastinal abscess.


Diagnostic pearls: Hypoattenuating diffuse, mediastinal widening associated with small gas bubbles. Discrete cavity with a shaggy, slightly enhancing wall represents an abscess.


Esophageal rupture is the most common cause and is associated with larger amounts of mediastinal gas. Any infection in the neck may also spread into the mediastinum.


After sternotomy, gas bubbles and fluid in the anterior mediastinum are indicative of an infection.


Acute anthrax


Acute infection caused by Bacillus anthracis.


Diagnostic pearls: Symmetric widening of the anterior and middle mediastinum resulting from hemorrhagic, diffuse edema of lymph nodes. Patchy pulmonary opacities and pleural effusion are also seen.


B. anthracis is a rod-shaped, gram-positive aerobic bacterium that is about 1 × 9 μm in length. There are 89 known strains of the bacteria. They produce two powerful exotoxins and a lethal toxin. Most common among sorters and combers in the wool industry. Pulmonary changes are more prominent than mediastinal ones.


Spondylitis


Either an inflammation or infection of the vertebrae depending on the underlying cause.


Diagnostic pearls: Fusiform, ill-defined, low-density paravertebral mass. Erosion or destruction of vertebral bodies at the level of the mass; usually in the inferior thoracic spine.


Distinct attenuation on postcontrast scans.


Pyogenic spondylitis usually affects one disk space only. Involvement of multiple disk spaces and large calcified paraspinal masses suggest spinal tuberculosis (Pott disease), marked by stiffness of the vertebral column, pain on motion, tenderness on pressure, prominence of certain vertebral spines, and occasionally abdominal pain, abscess formation, and paralysis.


Ankylosing spondylitis is a human leukocyte antigen (HLA) B27–associated autoimmune inflammation involving the spine and sacroiliac joints.


Neoplastic/thymic tumors


Thymic hyperplasia, thymic rebound hyperplasia


Fig. 18.17


Diffuse symmetric enlargement of the thymic gland.


Diagnostic pearls: Particularly the anteroposterior thickness of the gland is increased with preservation of the normal shape. Attenuation remains unchanged. Differentiation from thymic carcinoma usually not possible.


In adults, normal thymus measures < 1.3 cm. Thymic hyperplasia (i.e., thymoma) may be associated with hyperthyroidism as in Graves disease, acromegaly, Addison disease, and myasthenia gravis. Rebound hyperplasia occurs in children and young adults recovering from severe illness, after treatment for Cushing disease, or chemotherapy. Rebound may simulate recurrence of neoplasm on CT but is actually a transient overgrowth that resolves with time or after steroid treatment.


Lipoma, thymolipoma


Fig. 18.18a, b


Rare benign mediastinal masses.


Diagnostic pearls: Large, smooth, or lobulated fat-density mass within the anterior mediastinum. Usually indistinguishable from lipomas, but may contain components of soft tissue density.


Asymptomatic benign mass predominantly composed of fat (50%–80%). Lipoma may also occur in other parts of the mediastinum.


Thymolipoma is found only in the anterior mediastinum. Liposarcoma of the mediastinum is extremely rare, generally has a higher postcontrast attenuation than fat, and is more commonly found in the posterior mediastinum.


Thymic cyst


Fig. 18.19


Solitary or multiloculated, water-density, thin-walled anterior mediastinum lesion.


Diagnostic pearls: Near-water density attenuation of the cyst. Size ranges from some mm to > 12 cm. Usually no mural enhancement. Thin intracystic septations, hemorrhage and (subsequent), calcifications are observed.


Constitutes 1% of all mediastinal masses. Usually congenital, but may also be inflammatory or neoplastic.


Often found in patients with Hodgkin disease either concomitantly or following radiation therapy. It may persist after therapy and thus usually does not reflect a residue or recurrent lymphoma.


Thymoma


Fig. 18.20


Epithelial thymic neoplasm in the anterior mediastinum.


Diagnostic pearls: Round, oval, or lobulated well-defined mass of thymic density without a visible capsule; 25% show focal calcifications. Contrast uptake may be homogeneous in small lesions and heterogeneous in larger lesions. Convex shape and lobulation favor thymoma over thymic rebound or persistent thymic tissue.


Invasive thymoma (35%) has a muscle-equivalent density and shows a mild enhancement, but can also be heterogeneous and have eggshell calcifications. Pleural or pericardial deposits are indicative of malignancy.


Shows a variable amount of lymphocytes. The most common primary mediastinal tumor (20%) usually seen in adults.


Predominantly in patients 50 to 70 y of age; no gender preponderance.


Fifty percent of patients are asymptomatic, 30% present with myasthenia gravis, 20% with symptoms due to mediastinal infiltration or compression.


Ten to 15% of patients with myasthenia gravis and hypogammaglobulinemia also have a thymoma. Thymic carcinoid is not distinguishable from thymoma. Thymic carcinoma is a poorly defined large anterior mediastinal mass that commonly invades adjacent structures. Thymic Hodgkin lymphoma may be difficult to distinguish from thymoma even histologically. Chest wall invasion and lymphadenopathy suggest lymphoma (nodular sclerosis).


Neoplastic/germ cell tumors (GCTs)


Teratoma


Fig. 18.21


The vast majority (70%) of benign to low-malignant mediastinal GCTs.


Diagnostic pearls: Mature and immature teratomas are well-defined, multiloculated, cystic, middle mediastinal masses with irregular capsular walls and septa, which may enhance. Mature tumors often are completely solid. Ossification, calcification, and fat deposits, often visible as a fat–fluid level, are observed in 50%. Teratoma with additional malignant components (TAMC) typically is an ill-defined, large, thick-capsulated mediastinal mass.


Heterogeneous attenuation is indicative of hemorrhage and necrosis.


Infiltration of mediastinal fat, vessels, and airways is often observed.


Teratoma is a GCT of young adults (20—30 y).


It represents > 70% of all GCTs and occurs as three subtypes. Mature teratoma is a well-differentiated benign tumor and is the most common type. Immature teratoma consists of < 10% mesenchymal and neuroectodermal tissue. TAMC is a very aggressive subtype. Its primary denomination as “malignant teratoma” or “teratocarcinoma” is no longer used. Mature teratomas are usually asymptomatic and have an excellent prognosis. Immature teratoma is equally asymptomatic but may be a little more aggressive. TAMC is a very aggressive neoplasm with poor prognosis due to an insufficient response to chemotherapy. All types are occasionally also found in the anterior and posterior mediastinum.


Seminoma (germinoma)


GCT, histologically consisting of uniform sheets of lymphocytes and round cells.


Diagnostic pearls: Large, well-defined lobulated mass in the middle or anterior mediastinum. May be homogeneous or contain low-attenuation areas. Tends to extend to the left of midline. Calcification, necrosis, or invasion is uncommon. Discrete attenuation on postcontrast scans.


Represents 15% to 20% of all GCTs; has a peak in the third decade of life and is almost exclusively restricted to men. It is the most common malignant mediastinal GCT. Chest pain or respiratory symptoms are typical clinical complaints. Metastases to bone and lungs are common. Highly radiosensitive.


Nonseminomatous germ cell tumor (NSGCT) (embryonal cell carcinoma, choriocarcinoma, mixed cell tumors, etc.)


NSCGT is a nomenclature for all GCTs that are not teratomas or seminomas.


Diagnostic pearls: Large, ill-defined, lobulated anterior mediastinal mass with heterogeneous attenuation depending on predominant soft tissue component. Central hypodensities and calcification may occur with heterogeneous contrast enhancement. May displace or infiltrate mediastinal structures. Often concomitant pleural or pericardial effusion.


GCTs are a mixed group of neoplasms. They have a common histologic origin from the three primitive germ cell layers. Histologic features depend on tumor subtype. About 15% of patients with NSGCTs present clinically with Klinefelter syndrome. Patients often have an elevated serum alpha fetoprotein level. Clinical symptoms include chest pain and dyspnea.


Overall prognosis is poor, particularly in the presence of mediastinal invasion or pleural/pericardial effusion.


Neoplastic/thyroid and parathyroid tumors


Goiter


Fig. 18.22a, b


Also denominated mediastinal or substernal goiter.


Diagnostic pearls: Well-defined heterogeneous mass. May deviate the trachea and displace mediastinal vessels. Focal calcification is common. Precontrast attenuation is over 100 HU; enhances intensely.


Primary goiter due to migration anomaly and thus separate from thyroid gland. Secondary due to diffuse enlargement of thyroid gland and thus contiguous with the organ.


Represents 10% of all mediastinal masses; 75% to 80% in the anterior mediastinum, 20% to 25% in the posterior mediastinum.


Intrathoracic thyroid carcinoma


Substernal/mediastinal expansion of a primary thyroid malignancy.


Diagnostic pearls: Well- to ill-defined anterior mediastinal mass, slightly hyperdense on precontrast scans with a heterogeneous or peripheral postcontrast attenuation. May contain calcifications and hemorrhage (like benign lesions). Necrosis is present in > 50% and lymphadenopathy in 75% of cases.


Papillary thyroid carcinoma is the most common malignancy. It spreads locally via lymphatics. Follicular thyroid carcinoma occurs in adults and metastasizes hematogenously.


Anaplastic thyroid carcinoma represents 4% to 15% of thyroid malignancies in the seventh decade of life. It is a rapidly enlarging mass causing tracheal obstruction and symptoms at an early stage.


Medullary carcinoma of the thyroid


Medullary carcinoma of the thyroid is a distinct thyroid carcinoma originating in the parafollicular C cells of the thyroid gland.


Diagnostic pearls: On postcontrast scans, a low-density mediastinal nodule is seen; visible within strongly enhancing thyroid tissue if the gland extends as far caudally.


C cells produce calcitonin. Often occurs in conjunction with multiple endocrine neoplasia syndrome II (MEN II).


Tumor measures between 2 and 26 mm and may occur anywhere from the neck to the mediastinum.


Ectopic parathyroid gland


Ectopic location of the parathyroid gland.


Diagnostic pearls: Well-defined round and on pre-contrast scans hypodense mass of 1 to 2 cm resembling a lymph node.


On postcontrast scans, homogeneous attenuation between 60 and 70 HU as compared with lymph nodes with either > 90 and attenuation or a clearly visible central fat pad.


Of patients undergoing surgery for hyperparathyroidism, 22% present with an ectopic parathyroid gland. Eighty-one percent of those are localized in the anterior mediastinum. The tumor size usually correlates with the level of hypercalcemia.


Technetium 99m-labeled sestamibi and tetrofosmin tomography are the imaging modalities of choice, but CT may be useful for surgical planning.


Neoplastic/other primary tumors and tumorlike lesions


Lipomatosis


Fig. 18.23


Excessive fat deposition within the mediastinum.


Diagnostic pearls: Diffusely enlarged mediastinum due to smooth, symmetric, sometimes lobulated accumulation of fat in the mediastinum. Pleuropericardial fat pads are commonly enlarged.


Usually associated with Cushing syndrome or long-term corticosteroid therapy, occasionally with simple obesity.


Lymphoma


Fig. 18.24


Fig. 18.25


Mediastinal lymphadenopathy due to Hodgkin (HL) or non–Hodgkin (NHL) lymphoma.


Diagnostic pearls: HL presents as a slightly inhomogeneous bulky mass in the anterior mediastinum. Attenuation on postcontrast scans is discrete. Involvement of multiple nodal groups is characteristic. NHL presents as a bulky mediastinal bilateral hilar mass with predilection of the superior mediastinum. Lymph node enlargement is more prominent in paratracheal, retrocrural, and paravertebral locations. Postcontrast attenuation of enlarged lymph nodes may be normal or decreased.


Mediastinal involvement is more common in HL (> 50%) than in NHL (20%). Cervical and upper anterior lymph nodes are involved more often in HL. Involvement of paracardiac or lower posterior mediastinal nodes in HL is rare.


Leukemia


Comcomitant lymph node enlargement in leukemic patients.


Usually symmetric, modest enlargement of mediastinal and bronchopulmonary lymph nodes.


Diagnostic pearls: Round, homogeneous lymph nodes with slightly increased attenuation on postcontrast scans.


More often observed in lymphocytic than in myelocytic leukemia. Often associated with pleural effusion and pulmonary parenchymal involvement.


Lymph node metastases


Fig. 18.26


Fig. 18.27


Lymph node enlargement due to lymphatic spread of malignant neoplasties.


Diagnostic pearls: Size of lymph nodes not indicative of presence or absence of metastases. Calcifications are observed in metastases from cartilaginous or osseous tumors, mucinous adenocarcinoma, or bronchoalveolar carcinoma. On postcontrast scans, pronounced enhancement is observed in metastatic lymph nodes of renal, thyroid, and choriocarcinoma.


Bronchogenic carcinoma typically shows early spread to mediastinal lymph nodes. Even lymph nodes < 10 mm may contain micrometastases. Skip metastases (e.g., sparing of hilar lymph nodes)/contralateral lymph node metastases are observed. Any (near) round lymph node with a ratio of shortest/longest diameter near 1 and without central fat pad is highly suspicious, particularly if measuring > 10 mm in size. Other common primaries are head and neck tumors, breast cancer, renal carcinoma, and malignant melanoma.


Giant cell lymph node hyperplasia (Castleman disease)


Fig. 18.28


Rare benign lymphoproliferative hyperplasia of lymph nodes.


Diagnostic pearls:


Localized type: Well-defined or lobulated enlarged lymph nodes with strong homogeneous attenuation on postcontrast scans. Inhomogeneous or ring enhancement is indicative of necrosis. No pulmonary involvement.


Multicentric type: Several large, sharply demarcated mediastinal and hilar lymph nodes, with concomitant abdominal and/or cervical lymphadenopathy, with moderate postcontrast enhancement. Lymphogenic pulmonary pattern (i.e., ill-defined centrilobular nodules, nodular septal thickening, ground-glass opacities).


Histologically, hyaline vascular (90%), plasma cell (9%), or mixed types. Observed in middle-aged adults without any gender preponderance. Clinically, differentiation into a localized and multicentric type. Hyaline vascular types are usually localized and asymptomatic; plasma cell types, multicentric and symptomatic. In > 70% of cases, involvement of only the thorax; in 15%, also in the neck and/or abdomen. Localized forms may be treated by surgical resection; multicentric forms may need chemotherapy.


Neurogenic tumors


Fig. 18.29


Well-defined, round to oval posterior mediastinal mass.


Diagnostic pearls:


Nerve sheath tumors: Low-attenuation, well-defined, paravertebral soft tissue mass.


Calcifications and dumbbell appearance with a dilated neural foramen (extension into spinal canal) are observed in 10% to 15% of cases. Neoplasms usually show distinct, homogeneous enhancement, but may also have hypodense areas due to local necrosis. Sympathetic ganglion tumors: Ill-defined, typically longitudinally elongated paravertebral mass. Heterogeneous attenuation due to calcifications (ganglioneuromas/neuroblastomas), necrosis, hemorrhage, and cystic degeneration. Paragangliomas show strong homogeneous enhancement on postcontrast scans.


Histologic differentiation between nerve sheath tumors (neurinoma, neurofibroma, schwannoma, peripheral nerve sheath tumor, etc.) and sympathetic ganglion tumors (paraganglioma, ganglioneuroma, neuroblastoma). Neurofibromas and neurinomas occur in young adults, sympathicoblastomas during early childhood. Except for the rare paragangliomas (localized along the sympathetic chain, vagus nerve, intracardial, etc.), all other neoplasms are found exclusively in the posterior mediastinum.


Paragangliomas are a form of extraadrenal pheochromocytoma and thus may present with a hypertonic crisis.


Bone destruction, invasion of mediastinal structures, and pleural effusion suggest malignancy; otherwise, CT features lack histologic specificity.


Esophageal neoplasm


Fig. 18.30


Fig. 18.31a, b


Localized bulging of the esophagus.


Diagnostic pearls: Short- to long-segment wall thickening and passage obstruction often associated with prestenotic dilation. Any eccentric wall thickening >3 to 5 mm in a distended esophagus is highly suspicious of a neoplasm. Ill-defined periesophageal fat planes suggest spread into surrounding structures. Contrast enhancement often is discrete but may improve the tumor delineation.


Most commonly squamous cell carcinoma. Leiomyoma is located in the submucosa and thus typically appears as a smoothly marginated, homogeneously enhancing focal wall thickening. Inflammatory wall thickening of the esophagus may mimic a neoplasm but is usually more generalized. An esophageal diverticulum can be differentiated from a duplication cyst or necrotic neoplasm by oral contrast administration: a diverticulum is filled, but not a duplication cyst/neoplasm. Exact assessment of localization and longitudinal extension of the tumor, involvement of regional lymph nodes, local invasion (i.e., periesophageal fat stranding), and distant metastases is highly important for planning further therapeutic procedures.


Miscellaneous


Diaphragmatic hernias


Fig. 18.32 a–c


Hernia through either the foramen of Morgagni or Bochdalek hernia.


Morgagni hernia is characterized by a fat-density mass in the right cardiophrenic angle. Contains fine linear densities, which represent omental vessels. Bochdalek hernia typically is left posterolateral (>80%), large, and associated with organs (kidney, spleen, bowel, stomach, liver, etc.).


Uncommon diaphragmatic hernias through the foramen of Morgagni, which is a small triangular sternocostal zone lying between the costal and sternal attachments of the thoracic diaphragm. Demonstration of omental vessels helps in distinguishing Morgagni hernia from a pericardial fat pad. Bochdalek hernia accounts for >80% of all nonhiatal hernias and is caused by a failure of closure of the pleuroperitoneal cavity.


Esophageal hiatal hernia


Protrusion of (part) of the stomach through the esophageal hiatus of the diaphragm.


Diagnostic pearls: Axial hernias often resemble esophageal masses. A second contrast-filled lumen lateral to the distal esophagus is always indicative of paraesophageal hernia. Best visualized on coronal reformations.


Rule out other cystic mediastinal masses (see also Fig. 24.9 , p. 745).


Common in elderly and overweight patients.


Perigastric fat may herniate through the esophageal hiatus without the stomach proper.


Axial (sliding) hernias must be differentiated from paraesophageal hernias. In axial hernias, the gastroesophageal (GE) junction and the cardia are displaced intrathoracically. In paraesophageal hernias, the fundus with or without the GE junction is displaced intrathoracically.


Extramedullary hematopoiesis


Fig. 18.33


Hematopoiesis occurring outside the medulla of the bone.


Diagnostic pearls: Paravertebral soft tissue masses in the lower half of the thorax. May appear as fat-density masses.


More frequently associated with pathologic processes, such as myelofibrosis. Extramedullary hematopoiesis occurs typically with a characteristic purpura (“blueberry muffin” baby) in congenital hemolytic anemias (hereditary spherocytosis, thalassemia, sickle cell anemia, or TORCH [ toxoplasmosis, other agents, rubella, cytomegalovirus, herpes simplex] infections).

Fig. 18.4 Pancreatic pseudocyst in the posterior mediastinum. Cyst mimics mega esophagus but is nonattenuating after oral contrast medium. The esophagus appears as a small, compressed slit ventrally to the pseudocyst (arrow).
Fig. 18.5 Nonspecific enlargement of preaortic lymph nodes in a patient with pleural changes due to asbestos exposure.
Fig. 18.6 Sarcoidosis. Enlarged hilar lymph nodes on the right side with concomitant perilymphatic noduli in the lung parenchyma.
Fig. 18.7 Megaesophagus. Dilated esophageal diameter with thickening of the esophageal wall.
Fig. 18.8 Periesophageal fibrosis. Periesophageal fibrosis due to chronic ulcerating esophagitis appears as a subtle fibrosis in the region of the distal esophagus (arrows). Like varices, it enhances less strongly.
Fig. 18.9 Tracheomalacia. Narrowing of the tracheal lumen and thickened tracheal wall.
Fig. 18.10 Congenital tracheal stenosis simulating vascular ring-induced airway compression. The series of CT images shows no vascular ring but a fixed stenosis of 14 mm2 (arrow).
Fig. 18.11 Bronchogenic cyst. Well-defined, round, very thin-walled, nonenhancing mass of near-water density outpouching ventrally of the trachea.
Fig. 18.12 Pericardial cyst. Round, smooth, thin-walled, nonenhancing mass of near-water density located in the right cardiophrenic angle. Note the large subpleural bronchogenic carcinoma in the right lung.
Fig. 18.13 Neurenteric cyst. Water-density, thin-walled, nonattenuating mass in the upper posterior mediastinum near the neural foramen (arrow).
Fig. 18.14 Thoracic meningocele. Well-defined, solitary, water-density paravertebral lesion on the left. Note a discrete tail extending into the neuroforamen.
Fig. 18.15a, b Pneumomediastinum. Mediastinal streaks of air, extending from/to the neck (a) throughout the complete mediastinum (b).
Fig. 18.16 Acute mediastinitis in a 38-year-old man, as a complication of a peritonsillary abscess. The mediastinum is widened and contains low-density pus. Note bilateral concomitant pleural empyema.
Fig. 18.17 Thymic rebound hyperplasia after chemotherapy. Diffuse symmetric enlargement of the thymic gland. Differentiation from thymic carcinoma is not possible.
Fig. 18.18a, b Mediastinal lipoma. Fatty tumor (arrow) extending from the upper anterior mediastinum (a) along the right side of the pericardium (b). Subtle soft tissue density stranding is seen within the neoplasm.
Fig. 18.19 Thymic cyst. Near-water-density lesion in the anterior mediastinum at the level of the pulmonary artery. No attenuation is evident after IV contrast.
Fig. 18.20 Thymoma. Lobulated well-defined mass of thymic density without a visible capsule and with heterogeneous attenuation after IV contrast.
Fig. 18.21 Teratoma. Well-defined, multiloculated cystic anterior mediastinal mass with irregular heterogeneous attenuation and fat deposits.
Fig. 18.22a, b Retrosternal goiter. Posterior mediastinal mass with intense but inhomogeneous enhancement and the presence of subtle intralesional calcifications (a). Distinct anterior displacement of supra-aortal vessels is seen on coronal multiplanar reconstruction (MPR) (b).
Fig. 18.23 Mediastinal lipomatosis. Smooth, symmetric accumulation of fat within the anterior mediastinum (arrows).
Fig. 18.24 Mediastinal lymphoma. Large cell lymphoma involving the anterior, middle, and posterior mediastinum, as well as the chest wall. Note the inhomogeneous enhancement and massive displacement of blood vessels.
Fig. 18.25 Mediastinal non–Hodgkin lymphoma. A bulky mediastinal bilateral hilar mass with prominent enlargement of paratracheal lymph nodes.
Fig. 18.26 Hilar lymph node metastasis (melanoma). Metastatic left hilar lymph node is well contrasted against the pulmonary artery.
Fig. 18.27 Para-aortal lymph node metastasis (breast cancer).
Fig. 18.28 Castleman disease. Multicentric-type tumor with multiple large but sharply demarcated mediastinal and cervical lymph nodes. Diagnosis was made based on histologic results. CT appearance is indistinguishable from lymphoma or metastatic disease.
Fig. 18.29 Neurinoma. Well-defined, low-attenuation, paravertebral soft tissue mass on the right with distinct homogeneous enhancement.
Fig. 18.30 Esophageal neurilemoma. Radiographically, the tumor is indistinguishable from a leiomyoma.
Fig. 18.31a, b Distal esophagus carcinoma. Marked circular thickening of the distal esophagus and the cardia of the stomach (a). Multiplanar reconstruction (MPR) shows various paraesophageal and right hilar lymph nodes (b).
Fig. 18.32a–c Diaphragmatic hernias. Large fat-density mass ventral to the heart (arrows). Linear densities represent omental vessels (a). Herniated right kidney through large Bochdalek hernia in the left posterolateral angle (b). Sagittal MRI shows defect in the posterior diaphragm (c).
Fig. 18.33 Extramedullary hematopoiesis. Multiple well-defined paravertebral soft tissue masses in a patient with thalassemia major. Note hemachromatosis of the liver and concomitant splenomegaly. Same patient as in Fig. 18.34.














































































































Table 18.2 Mediastinal vessels

Disease


CT Findings


Comments


Vascular


Dilation of the pulmonary artery


Fig. 18.34


Dilated pulmonary artery.


Diagnostic pearls: On precontrast scans, may mimic large hilar masses.


Common causes include congenital pulmonary valvular stenosis and cor pulmonale; > 28 mm pulmonary trunk diameter is indicative of pulmonary hypertension.


Kinking/aneurysm of the innominate artery (right) or the subclavian artery (left)


Unusually wide lumen of the involved vessel.


May be associated with atherosclerosis or coarctation of the aorta.


Superior vena cava (SVC) dilation


Widened SVC in the right middle mediastinum.


Secondary to elevated central venous pressure (heart failure) or compression/obstruction due to a mediastinal mass.


Azygos or hemiazygos dilation


Diagnostic pearls: Unusually large enhancing vessel at the normal posterior mediastinal location of the corresponding vessel.


Usually of no significance, but may be associated with elevated central venous pressure or with azygos continuation of the inferior vena cava (IVC).


Mediastinal varices


Increased dilation, number, and/or tortuosity of mediastinal veins.


Diagnostic pearls:


Paraesophageal varices: Collateral mediastinal vessels adjacent to the esophagus.


Esophageal varices: Collateral mediastinal vessels within the esophagus.


Varices classified as uphill or downhill, depending on underlying pathology. Uphill varices occur due to portal hypertension. Downhill varices mainly occur due to SVC obstruction.


Aortic surgery


Fig. 26.3 , p. 779


History of previous interventional stent or surgical graft placement.


Diagnostic pearls: Initially high attenuation, later (> 2 wk) low-attenuation, homogeneous perigraft mass indicative of hematoma.


Fluid–fluid levels show sedation of hemoglobin in time. Irregular, septated periaortic fluid or gas collection indicates an infected graft. Irregular periaortic fat stranding on nonenhanced CT and moderate attenuation of aortic wall and periaortic fat on postcontrast scans are typical of stent/graft infection. Septated periaortic fluid or gas collection highly suspicious of abscess formation. Lack of luminal contrast enhancement observed in thrombosis. A blood-equivalent mass lesion with rim enhancement with or without septations may be a pseudoaneurysm.


Aortic graft may be end-to-side, end-to-end, or intraaneurysmal. Ascending aorta grafts may include aortic valve replacement. Ventral collections of perigraft gas and fluid shortly after surgery may be a normal postoperative finding.


Differential diagnosis: Seroma, lymphocele.


A common complication of endovascular aneurysm repair (EVAR) is endoleaks, which may continue to perfuse and pressurize the aneurysm sac, thereby conferring an ongoing risk of aneurysm enlargement and/or rupture.


Endoleaks are classified by the source of blood flow and organized into five categories.


I: Attachment site leaks


II: Collateral vessel leaks


III: Graft failure (i.e., midgraft hole, junctional leak, or disconnection)


IV: Graft wall porosity


V: Endotension (with or without endoleak)


Inflammatory


Aortic atherosclerosis


Fig. 18.35a, b


Degenerative arterial disease.


Diagnostic pearls: Semicircular, smooth to irregular aortic wall thickening and hypoattenuation of plaques, which are usually wall adherent and may or may not be partly calcified or not. Calcifications occur as curvilinear hyperdensities on the outer side of the plaque (i.e., within the aortic wall).


Atherosclerotic risk factors (see Framingham risk factors) initiate vascular stress with subsequent local vascular inflammation, progressive intimal thickening, and finally stenosis; may also lead to formation of an intravasal thrombus or an aneurysm. Plaques may be calcified (stable) or noncalcified (more prone to rupture, e.g., atheromas). Eccentric array of calcifications is an important differentiator from aortic dissection (centrally displaced intima).


Aortic aneurysm


Fig. 18.36a, b


Fig. 18.37a, b


Fig. 18.38a, b


Fig. 18.39


Segmental to total saccular or fusiform aortic dilation.


Diagnostic pearls: Fusiform or saccular dilation of the aorta and pear shape of sinus of Valsalva in case of anuloaortic ectasia. Curvilinear calcification of the dilated aortic wall is common. Any thrombus, if present, lies centrally to these calcifications. An intimal flap indicates dissecting aneurysm, which may be present without significant dilation of the aorta. Aneurysm may extend into abdomen and may involve ascending aorta, aortic arch, and/or descending aorta (see Crawford classification). Normal ascending aorta measures < 4 cm in diameter; normal descending aorta measures < 3 cm in diameter.


Signs of an imminent aortic aneurysm rupture are soft tissue stranding of perianeurysmal fat and local lung atelectasis.


Common conditions associated with aortic aneurysm are atherosclerosis, cystic medial necrosis (i ncluding Marfan disease), trauma, and mycotic infection.


An aneurysm just distal to the origin of the left subclavian artery is likely due to closed trauma.


Crawford classification for staging:


Type 1: Aneurysm from left subclavian artery to renal arteries


Type 2: Aneurysm from left subclavian artery to aortic bifurcation


Type 3: Aneurysm from descending aorta to aortic bifurcation


Type 4: Aneurysm from upper abdominal aorta and all or none of the infrarenal aorta


Surgical/interventional repair required for 1 cm/y diameter growth rate or diameters > 5.5 cm (ascending aorta) and > 6.5 cm (descending aorta). Any sign of an imminent aortic aneurysm rupture is an emergency situation.


Aortic dissection


Fig. 18.40a–c


Fig. 18.41a, b


Spontaneous intimal tear with continuous mucosal wall separation.


Diagnostic pearls:


Nonenhanced CT: Calcified intima displaced centrally Contrast-enhanced CT (arterial phase): Contrast-filled double (true and false lumen) channel with an intervening intimal flap spirals down the aorta


Indicators of false lumen:


Usually the larger lumen has delayed contrast.


“Beak” sign: Acute angle between dissected flap and outer wall


Presence of cobwebs: Thin mucosal strands crossing false lumen


Intraluminal thrombus with centrally displaced intima (calcifications)


In general, eccentric array of calcifications is an important differentiator to aortic dissection (centrally displaced intima).


Histologically, a cystic media necrosis from either atherosclerosis or congenital disorders. May be due to collagen disorders (Ehlers–Danlos syndrome, Marfan syndrome, Turner syndrome, osteogenesis imperfecta, etc.), trauma, hypertension, or pregnancy (> 50% of dissections in women).


Stanford classification of dissections:


Type A: Entry of dissection in ascending aorta (70%)


Type B: Entry of distal to left subclavian artery (30%) Intimo-intimo intussusception is observed in case of complete circumferential dissection.


Typical complications include occlusion of aortic side branches and continuation into iliac arteries.


Multiplanar reconstruction (MPR) is useful for assessment of exact dimension of dissection.


Look out for distal reentry.


Typical pitfalls are streaks (i.e., motion artifacts in the ascending aorta). When in doubt, perform electrocardiogram- (ECG-) triggered CT.


Intramural hemorrhage (IMH)


Fig. 18.42a–c


Localized hemorrhage within the aortic media.


Diagnostic pearls: IMH usually presents as focal crescenteric, high-attenuation thickening of the aortic wall with internal displacement of intimal calcifications. Hyperattenuation is usually far better appreciated on unenhanced images.


Protocols for aortic imaging should always begin with noncontrast helical images of the chest.


On postcontrast scan, hypoattenuating as compared with hyperattenuating aortic lumen (“flip-flop” pattern) is common.


Unlike atherosclerotic plaque, IMH generally creates a smooth margin with the contrast-enhanced aortic lumen.


The natural history of IMH is not completely evident. Several causes for the formation of IMH include:


1. Rupture of the vasa vasorum resulting in weakening of the aortic wall


2. Spontaneous thrombosis of the false lumen of an aortic dissection


3. Penetrating atherosclerotic ulcer induced by rupture of an intimal atherosclerotic plaque, allowing blood to gain access to the aortic media (Fig. 18.42c).


It is unclear which mechanism predominates, but most likely all of the above mechanisms play some role in the development of IMH. Pathologically, IMH results in weakening of the aortic wall, which may predispose to dissection or rupture of the aorta.


Takayasu arteritis


Fig. 18.43


Widespread smooth wall thickening and narrowing of the aorta and adjacent major vessels.


Diagnostic pearls: Concentric smooth wall thickening and local aortic and arterial stenosis. Dystrophic wall calcifications may occur, also homogeneous involvement of large supra-aortic arteries. Plaques may enhance on postcontrast scans.


Disease of unknown etiology, which is typically observed in Asian countries/populations. Histologically, the inflammation starts with a mono-nuclear infiltration of the adventitia, followed by granulomatous changes in the media and subsequent fibrosis and thickening of the intima and media.


Type I affects predominantly young adults (< 20–30 y) without any gender preponderance. Complications occur mainly due to stroke and hypertension.


Steroids are the treatment method of choice. Angioplasty may be applied in the presence of stenosis.


Occlusion of superior vena cava (SVC)


Fig. 18.44


Total or near total occlusion of the SVC.


Diagnostic pearls: Diagnosed by visualization of underlying cause and the exact level of the occlusion, as well as display of collateral pathways.


May result from thrombus formation, external compression, IV growth, or a combination of all three. Collateral pathways include the posterior system (azygos-hemiazygos vein/paravertebral veins), the anterolateral system (internal mammary veins/anterior thoracic veins), and the superior system (anterior jugular venous system/external jugular vein/transverse arch).


Congenital


Aortic coarctation


Fig. 18.45


Localized stenosis of the distal aortic arch or descending aorta.


Diagnostic pearls: Narrowing of the distal aortic arch and/or descending aorta. Tortuous intercostal arteries serve as collaterals and thus lead to marked inferior rib notching.


Occurs in < 1% of neonates.


CT may allow diagnosis before clinical symptoms and bone erosions. Occasionally, an incidental finding on CT.


MPRs in parasagittal/para-aortic orientation are useful for diagnosis.


Double aortic arch


Two aortic arches form a complete vascular ring that can compress the trachea and/or esophagus.


Diagnostic pearls: The arches may compress both sides of the trachea, usually more on the right side. Most commonly, there is a larger (dominant) right arch behind and a hypoplastic left aortic arch in front of the trachea/esophagus. The two arches join posteriorly to form the descending aorta which is usually on the left side (but may also be right-sided or in the midline). The right subclavian and common carotid arteries arise from the right arch and the left from the left arch.


A rare congenital abnormality but one of the two most common forms of vascular ring, a class of congenital anomalies of the aortic arch system in which the trachea and esophagus are completely encircled by connected segments of the aortic arch and its branches. Although the double aortic arch has various forms, the common defining feature is that both the left and right aortic arches are present.


Usually asymptomatic, but may cause stridor, dyspnea, or recurrent pneumonia. Seventy-five percent occur in the left descending aorta, and the smaller arch is usually (80%) anterior.


Left aortic arch/aberrant right subclavian artery


The right subclavian artery arises as the last branch of the aortic arch and crosses the mediastinum from left to right behind the trachea and the esophagus.


Diagnostic pearls: Tubular opacity behind the esophagus in contiguity with the aberrant right subclavian artery, which is seen on the right posterior aspect of the trachea.


The most common anomaly of the aortic arch, with an incidence of 0.4% to 2%. Also known as arteria lusoria. Mirror image of right aortic arch (RAA) in Fig. 18.44. May cause dysphagia.


Right aortic arch (RAA)


Fig. 18.46


Two types: RAA with either aberrant left subclavian artery or mirror imaging branching.


Diagnostic pearls: In both types, the aortic arch passes and descends to the right of the trachea. In case of an RAA with aberrant left subclavian artery, there are four supra-aortic vessels (left and right carotid and subclavian artery). The left common carotid artery is the first branch, whereas the left subclavian artery is the last, taking a retropharyngeal course.


In case of RAA with mirror imaging branching, there are only three supra-aortic branches (left innominate, right carotid, and subclavian artery). The left innomi-nate artery originates as the first branch of the aorta, and there is no visible retroesophageal vessel.


RAA is due to a partial regression of the left fourth aortic arch.


In case of an RAA with aberrant left subclavian artery, the left arch is interrupted between the left carotid and subclavian artery. It may form a vascular ring with the left ductus arteriosus. In 5% to 12% of cases, there is an association with congenital heart disease (i.e., tetralogy of Fallot, truncus arteriosus, transposition of great vessels). In some cases, the left subclavian artery may arise from the aortic diverticulum.


In case of an RAA with mirror imaging branching, it is interrupted dorsally to the left subclavian artery. Tetralogy of Fallot is present in 98% of cases.


Circumflex right aortic arch/left descending aorta


A rare anomaly of the aortic arch.


Diagnostic pearls: Transversely oriented right aortic arch causes impression of the posterior trachea and descends on the left side.


May mimic double aortic arch.


Persistent left superior vena cava (SVC)


Fig. 18.47


Persistent left anterior and common cardinal vein that drains via the coronary sinus into the right atrium.


Diagnostic pearls: In 80% of cases, the right SVC is also present.


The most common anomaly of the systemic venous return to the heart, with an incidence of 0.3% in normal patients and 4.4% in patients with congenital heart disease. Increased incidence in asplenia syndrome.


Left superior vena cava (SVC)


Fig. 18.48


Persistence of left common cardinal vein.


Diagnostic pearls: Large mediastinal vein that descends left of the aortic arch and drains into the coronary sinus; absence of SVC on the right side. Often associated with absent left brachiocephalic vein.


No known genetic predisposition.


Higher prevalence in patients with congenital heart disease.


Azygos continuation of the inferior vena cava (IVC)


Congenital anomaly with multiple variants.


Diagnostic pearls: Dilated azygos and hemiazygos veins in their paravertebral course associated with nonvisualization of the intrathoracic IVC.


Systemic venous return to the heart is via azygos and hemiazygos veins.


Hepatic veins drain independently by a venous confluence into the right atrium. Often associated with heart anomaly, abnormal situs, and asplenia or polysplenia.


Traumatic


Mediastinal hemorrhage or hematoma


Diffuse mediastinal widening, commonly in upper mediastinum.


Diagnostic pearls: Ill-defined mediastinal mass with direct relationship to larger vessels. In an acute setting hyperdense, on nonenhanced CT. Hyperdense contrast streaks/pools on postcontrast scans are indicative of an Hb-relevant bleeding.


Subacute hematomas become iso- to hypodense (0–20 HU) within weeks and show no attenuation on postcontrast scans.


Sometimes sedimentation levels are visible.


Associated with trauma, surgery, or dissecting aneurysm of the aorta. May require urgent surgical/interventional repair.


Neoplasms


Hemangioma


Congenital malformation of vascular channels.


Diagnostic pearls: Anterior mediastinal mass sometimes with presence of phleboliths; well-defined mass with heterogeneous attenuation; small ringlike or round calcifications (phleboliths) in one third of cases; on postcontrast scans, heterogeneous (often delayed) attenuation.


Histologically, hemangiomas are endothelial-lined vascular channels with admixed fibrosis and sclerosis. Classified into three subtypes: capillary, cavernous, and venous.


If not asymptomatic, patients usually present with chest pain. More common in children.


May increase in size over time.


Surgery recommended only if lesions become symptomatic.

Fig. 18.34 Pulmonary hypertension. Marked dilation of the pulmonary artery. Same patient as in Fig. 18.33.
Fig. 18.35a, b Aortic atherosclerosis. Semicircular, smooth aortic wall thickening on contrast-enhanced CT angiography (a). Nonenhanced CT shows that calcifications are located on the outer side of the plaque (i.e., within the aortic wall) (b).
Fig. 18.36a, b Saccular aortic aneurysm. Crawford type 3 saccular aortic aneurysm of the descending aorta on transverse CT scan (a) and maximum intensity projection (MIP) (b).
Fig. 18.37a, b Saccular aortic aneurysm of the descending aorta (Crawford type 1). On transverse scan, an intimal flap is seen (a), but sagittal MPR shows true saccular aneurysm with no dissection (b).
Fig. 18.38a, b Fusiform aneurysm. Fusiform aneurysm of the ascending aorta (a) without involvement of the aortic arch or supra-aortic vessels (b).
Fig. 18.39 Imminent rupture of aortic aneurysm. Soft tissue stranding of perianeurysmal fat and local lung atelectasis are highly suspicious of an imminent aortic rupture. This is an emergency situation.
Fig. 18.40a–c Aortic dissection. Calcified intima displaced centrally (a). A contrast-filled double channel spirals down the entire aorta and also involves supra-aortic vessels (Stanford type A) (b). The false lumen is the smaller lumen, recognizable by the beaklike angulation with the aortic wall and presence of intraluminal cobwebs (c).
Fig. 18.41a, b Aortic dissection. Stanford type B aortic dissection (a) with a partly thrombosed larger false lumen (b).
Fig. 18.42a–c Intramural hemorrhage. On nonenhanced CT, focal crescenteric, high-attenuation thickening of the aortic wall with internal displacement of intimal calcifications (a). After IV contrast, typical flip-flop pattern (b). Penetrating atherosclerotic ulcer of the aorta: hypodense atheroma with central ulceration at the flow of the aortic arch (c).
Fig. 18.43 Takayasu arteritis in a 20-year-old female patient. Widespread smooth wall thickening of the aorta, dystrophic wall calcifications in the aortic arch, local stenosis of the distal aorta, and homogeneous involvement of large supra-aortic arteries.
Fig. 18.44 Bronchogenic carcinoma. Near occlusion of the superior vena cava due to infiltration of central bronchogenic carcinoma with collateral flow through an enlarged azygos vein (visible on the left side, just above the left atrial appendage).
Fig. 18.45 Aortic coarctation. Localized stenosis of the distal aortic arch clearly visible on sagittal MPR.
Fig. 18.46 Right aortic arch. The aortic arch passes and descends to the right of the trachea, aberrant left subclavian, taking a retropharyngeal course.
Fig. 18.47 Persistent left superior vena cava. Persistent left anterior and common cardinal vein that drains via the coronary sinus into the right atrium.
Fig. 18.48 Left superior vena cava (SVC). Large left mediastinal vessel that drains into the coronary sinus. Note the absence of the SVC on the right side.

CT coronary angiography is prone to motion artifacts; thus, spatial and temporal resolutions are key. It is advisable to use (ECG-gated/-triggered) CT scanners that provide at least ≥ 40 detector rows, ≤ 0.5 mm collimation width, and ≤ 180 ms rotation time. In addition, proper patient preparation and use of bolus triggering or test bolus calculation at the level of the aortic root are critical for sufficient image quality.


However, even with current state-of the-art CT scanners that fulfill these technical requirements, the best image quality is still achieved at heart rates < 60 bpm and in the presence of maximal distended coronary arteries. Intravenous (IV) beta blockage and sublingual nitro application prior to scanning thus are highly recommended. Motion or reconstruction artifacts and/or vessel calcifications are typical reasons to overcall the degree of coronary artery stenosis. Assessment of CT coronary arteriograms therefore requires not only a thorough understanding of coronary anatomy but also sufficient experience in the interpretation of coronary atherosclerosis. Readers are advised to use center-line multiplanar reconstruction (MPR) stenosis assessment and should be aware that the degree of stenosis on CT scans is usually calculated as area of stenosis, whereas on angiograms, it is determined by diameter of stenosis. Calcified lesions tend to be overcalled by up to 30%. Thus, it is useful to apply near-bone window/level settings for better appreciation of these lesions. According to the American Heart Association (AHA), there are eight different plaque types based on five phases of atherosclerosis, but CT can only reliably differ between calcified and noncalcified plaques. Figure 18.51 is a schematic drawing of coronary artery segments according to the AHA.


Assessment of functional parameters remains a domain of echocardiography or magnetic resonance imaging (MRI) due to their much higher temporal resolution. However, it may be roughly estimated from retrospectively gated CT data sets. New scanner generations, such as dual-source CT, which combines two-scan detectors and x-ray tubes in one gantry, allow for rotation times of < 160 ms (i.e., image acquisition times of < 80 ms) and thus may challenge these established non-CT image modalities. In addition, radiation dose, scan times, and systolic motion artifacts are significantly reduced as compared with single-source CT scanners. Functional assessment is usually done by using short- or long-axis reformations, which are cut perpendicular to each other, the level of atrial valves, and the myocardial septum. Short-axis views also allow segmental allocation of myocardial vascular supply. Figure 18.53 is a schematic drawing of left ventricle (LV) myocardial segments according to the AHA.


Table 18.3 outlines differential diagnoses of cardiac abnormalities that may be visible on conventional CT scans. However, due to didactic reasons, several cases not only derive from ECG-gated/-triggered data sets, but also are shown as volume rendering threshold (VRT) reformations, short-/long-axis views, or center-line MPRs.


Intrathoracic nonvascular calcifications are usually harmless sequelae of bygone processes. They occur in the lung parenchyma, mediastinum, hilar and mediastinal lymph nodes, pleura, and chest wall, or in any combination of these structures. The cause of calcifications may be determined by means of the location and pattern of calcifications, as well as knowledge of associated clinical features. Apart from vascular lesions, the most common cause of thoracic calcifications is a previous infection. Less often they may be due to neoplasms, metabolic disorders, occupational exposure, or previous medical therapy. Small calcifications may be visible on CT or high-resolution CT but not on conventional chest radiographs. Thoracic calcifications are discussed in Table 18.4.





































































































































Table 18.3 Heart

Disease


CT Findings


Comments


Vascular


Coronary artery atherosclerosis


Fig. 18.49a–c


Fig. 18.50


Degenerative arterial disease with intramural accumulation of fatty substance, cholesterol, calcium, and cellular waste products.


Diagnostic pearls: Luminal narrowing of coronary arteries. Usually the plaque is nicely visualized as a hypodense area within hyperdense vessel.


An overall hazy appearance of the lumen indicates total occlusion. Exact stenosis localization may be described in the report according to the AHA classification (Fig. 18.51).


Atherosclerotic risk factors (see Framingham risk factors) initiate vascular stress with subsequent local vascular inflammation, progressive intimal thickening, and finally stenosis.


Presence of contrast material distal to a total occlusion may be due to collateral flow and not indicative of a remaining lumen.


Coronary artery aneurysm


Fig. 18.52a, b


More than 1.5 times dilated coronary artery diameters as compared with adjacent vascular segment.


Diagnostic pearls: May be fusiform or saccular, thrombosed or dissected.


Calcifications occur in the presence of atherosclerosis.


May be congenital, procedural (percutaneous transluminal coronary angioplasty [PTCA], etc.), or due to atherosclerosis, Kawasaki disease, or connective tissue disease (Marfan syndrome, systemic lupus erythematosus [SLE], etc.).


Myocardial ischemia


Fig. 18.54


Myocardial hypoperfusion due to obstructive coronary artery disease.


Diagnostic pearls: Ill-defined hypodensity within subendocardial myocardium. Restricted to myocar-dial segments that are supplied by the near-occluded vessel.


May be visible on non-ECG-gated CT of the chest. Indicative of a > 70% diameter (i.e., > 90% area) stenosis and thus a first sign of imminent MI.


Acute myocardial infarction (MI)


Fig. 18.55


Acute coronary artery occlusion leading to ischemic myocyte damage.


Diagnostic pearls: Vascular filling defect on CT angiograms, ill-defined transmural hypodensity. Restricted to myocardial segments (see Fig. 18.53 , p. 661) that are supplied by the occluded vessel.


Usually due to atherosclerotic plaque rupture followed by thrombosis. May present with typical clinical symptoms such as acute chest pain, elevated cardiac enzymes (troponin, creatine kinase myocardial band fraction [CK-MB]), and ST elevation, but also without any of these findings (non–ST elevation MI).


Chronic myocardial infarction (MI)


Fig. 18.56


Fig. 18.57


Myocardial damage and scar formation due to prolonged ischemia or previous MI.


Diagnostic pearls: Thinning of myocardium with diminished transmural perfusion, often presence of fatty deposits in subendocardial myocardium. Myocardial aneurysm or calcifications may occur.


Restricted to myocardial segments that were supplied by the occluded vessel.


Secondary findings include enlarged left atrium and ventricle with or without findings of pulmonary hypertension. Fast-rotating CT scanners (dual-source CT) may also show myocardial hypokinesis/akinesis/dyskinesis.


On late-enhancement scans, typically intramural/transmural contrast accumulation (contrast material pools within extracellular matrix, which is enlarged due to scar formation).


Myocardial aneurysm


Fig. 18.58


Segmental outward bulging of thinned, fibrotic myocardium.


Diagnostic pearls: Most commonly observed in the region of the cardiac apex. Filling defect on postcontrast scans indicative of thrombus formation. May calcify.


Usually occurs several weeks after transmural MI. Affected segments typically dys- or akinetic.


Inflammation


Dilated cardiomyopathy (DCM)


Fig. 18.59


Left ventricular dilation with systolic dysfunction with or without right ventricular dysfunction.


Diagnostic pearls: Increased left ventricular diameter (> 3 cm/m2 body surface), left ventricular ejection fraction < 45%, and contractile dysfunction.


Etiology includes genetics (familial DCM 2%), neuromuscular disorders, and myocardial ischemia. Medication is treatment of choice, followed by device therapy with ICD or cardiac transplantation. Echo/MRI is imaging modality of choice.


Hypertrophic cardiomyopathy (HCM)


Increased left ventricular mass due to asymmetric myocardial hypertrophy.


Diagnostic pearls: Left ventricular wall thickness > 15 mm; asymmetric septal thickening (basal > apical); obstruction of left ventricular outflow tract (LVOT); normal cardiac shape.


Histologically, a genetic disease (autosomal dominant) of the cardiac sarcomer. No age or gender preference. Patients most often are asymptomatic. Echocardiogram/MRI is imaging modality of choice.


Restrictive cardiomyopathy (HCM)


Diastolic function is abnormal, whereas systolic function is preserved.


Diagnostic pearls: Normal systolic function, normal wall thickness, and small left ventricular cavity; normal pericardium (< 3 mm) excludes constrictive pericarditis.


May be idiopathic without any known cause or secondary due to chemotherapy, radiation therapy, amyloidosis, hemochromatosis, glycogen storage disorders, or sarcoidosis.


Echocardiogram/MRI is imaging modality of choice.


Myocarditis


Myocardial inflammation with subsequent necrosis with or without degeneration of myocytes.


Diagnostic pearls: Delayed imaging may show late enhancement. Characterized by segmental myocar-dial dysfunction. Left ventricle (LV) or global dilation may be observed.


May be idiopathic, viral (Coxsackie B, Epstein–Barr virus, etc.), or due to autoimmune disorders (Takayasu arteritis, SLE, Wegener granulomatosis, etc.).


May be fulminant, acute, chronic, or chronic persistent. Exclude ischemic causes on CT angiography.


Echocardiogram/MRI is imaging modality of choice.


Pericardial effusion/acute pericarditis


Fig. 18.60


Fig. 18.61


Fluid collection in the pericardial space.


Diagnostic pearls: Well-defined water-density fluid collection between the myo- and pericardium along the contour of the heart; small effusions are usually found in the most dorsal part of the heart. Gas bubbles are indicative of an infection.


CT density measurement is useful for assessing the underlying cause (chyle, blood, or serous fluid). Deformed ventricular contour with or without dilated IVC/SVC is indicative of pericardial tamponade.


Usually accidental finding. May be traumatic, postsurgical, neoplastic, infectious, inflammatory following acute MI, or due to collagenosis, uremia, or medication.


Pericardial tamponade describes a situation of impaired diastolic ventricular filling with or without myocardial compression due to < 50 mL of fluid in the pericardial space.


Pneumopericardium is usually posttraumatic.


Chronic pericarditis


Chronic pericardial effusion due to various causes.


Diagnostic pearls: High-attenuation effusion (10–40 HU). Often associated with thickened, attenuating pericardium. Asymmetric accumulation suggests encapsulated effusion.


Typically due to chronic diseases, such as slow infections (e.g., TB), or irradiation.


Chronic constrictive pericarditis


Fig. 18.62


Impaired ventricular filling due to abnormal pericar-dial thickening.


Diagnostic pearls: Pericardial thickening (> 5 mm) with or without calcification.


Pericardial enhancement indicates an active inflammatory process and can be used to distinguish effusion from thickened pericardium.


Any purulent and serofibrinous type of pericarditis may transform into chronic constrictive pericarditis.


Pericarditis calcarea is a chronic constrictive pericarditis that is dominated by myocardial encasement due to a thinned but heavily calcified pericardium.


Takotsubo syndrome


“Broken heart” or stress-induced cardiomyopathy.


Diagnostic pearls: Absence of relevant coronary artery stenosis; systolic ballooning of the left ventricular apex, and normal contraction of the base.


Diffuse coronary microvascular dysfunction is discussed as the underlying pathology. Typically observed in patients with physical or emotional stress. Usually resolves completely over time.


Congenital


Coronary artery anomalies


Fig. 18.63


Anomalous origin of coronary arteries.


Diagnostic pearls: May affect left coronary artery (LCA), left circumflex (LCX), or right coronary artery (RCA).


Anomalous LCA/LCX arises from right sinus of Valsalva, anomalous RCA from left sinus of Valsalva. Benign variants run either anteriorly to the pulmonary artery (PA) or posteriorly to the aorta. Malignant variants are encased between the aorta and PA.


Usually asymptomatic. No gender predilection. Primary congenital anomalies of the coronary arteries occur in 1% to 2% of the general population.


LCX anomaly is the most common variant.


In Bland–White–Garland syndrome, an anomalous LCA arises from the pulmonary artery. Typically observed in children who present with heart failure (> 90%), shortness of breath, angina with or without MI. Rare in adults.


Pericardial defect


Partial or complete absence of pericardial contour on CT scans.


Diagnostic pearls: Most commonly (70%) affects the left side of the pericardium. Increased intrapulmonary protrusion of the left pulmonary artery (PA) and indentation of lung parenchyma between the ascending aorta and PA.


Protrusion of fat or abdominal organs into the pericardium is indicative of a diaphragmatic pericardial defect (17%).


Rare anomaly. In 30% of cases, associated with other congenital abnormalities, including atrial septal defect, patent ductus arteriosus, bronchogenic cyst, pulmonary sequestration, mitral stenosis, and tetralogy of Fallot.


In the absence of concomitant abnormalities, the patient is usually asymptomatic.


Pericardial cyst/diverticulum


Fig. 18.64


Pericardial mass at the right anterior costophrenic angle.


Diagnostic pearls: A pericardial cyst appears as a well-defined, thin-walled, round to oval mass with attenuation values between 0 and 20 HU. Calcification is rare. Diverticula communicate with the pericardium but are otherwise similar in CT appearance.


Rare lesions usually seen in asymptomatic patients. May mimic pulmonary/mediastinal mass on chest radiograph.


Congenital heart disease


Fig. 18.65


Fig. 18.66


Fig. 18.67


Fig. 18.68


Fig. 18.69


Fig. 18.70


A variety of congenital heart anomalies with either right-left or left-right shunting.


Diagnostic pearls: Figure 18.65 lists the most common types, including endocardial cushion defects (atrial [ASDs] and ventricular septal defects [VSDs], common atrioventricular channel), persistent ductus arteriosus Botalli, pulmonary stenosis, tetralogy of Fallot, total anomalous pulmonary venous return, mitral or tricuspid atresia, Ebstein anomaly, coarctation, and transposition of large vessels.


Congenital heart disease is typically observed in newborns and, due to radiation issues, usually assessed with MRI.


MRI allows precise noninvasive flow measurements and functional assessment. CT offers the benefit of significantly shorter examination times, making sedation typically obsolete. Recent introduction of low-dose dual-source technology allows image acquisition at < 1 ms.


Benign neoplasms


Intracardiac thrombus


Fig. 18.58 , p. 663


Nonspecific intraluminal filling defect.


Diagnostic pearls: Thrombus is hypodense (< 50 HU) in comparison to normal myocardium (70–90 HU). Left ventricular (LV) thrombus usually associated with aneurysm.


Left atrial (LA) thrombus usually associated with LA dilation.


Thrombus may calcify.


Underlying causes include deep vein thrombosis, left atrial fibrillation, presence of foreign material (pacemaker wires, etc.), previous heart surgery, and cardiomyopathy.


LV thrombus most common, followed by LA thrombus. Right ventricular (RV) and right atrial (RA) thrombi are rare.


Cardiac myxoma


Fig. 18.71


Most common primary neoplasm of the heart.


Diagnostic pearls: Almost exclusively restricted to the atrium, 83% located in the LA, 12% in the RA; 5% in atypical location. Typically located at LA fossa ovalis. Nonattenuating intra-atrial filling defect seen on postcontrast scans. May contain cystic components.


Very slow-growing gelatinous neoplasm.


May be sporadic or familial (Carney complex). Typically observed in middle-aged patients. Myxoma may obstruct the mitral valve. Surgical resection is treatment of choice in symptomatic patients.


Other benign neoplasms


Diagnostic pearls: Usually non- to slightly hyperattenuating intracardiac filling defects.


Tumor localization is often indicative of tumor entity: fibroelastoma (valves); paraganglioma (LA); lipoma (RA/RV); fibroma (ventricular wall); lymphangioma (ubiquitous); rhabdomyoma (multilocular/intramyocardial).


Accidental finding on CT scans.


MRI imaging is modality of choice.


Combined T1- and T2- weighted MRI allows further differentiation between histologic subtypes.


Malignant neoplasms


Intracardiac metastasis


Fig. 18.72


Diagnostic pearls: Nonspecific intracardiac filling defect at any location.


Most common primaries are bronchial carcinoma, melanoma, and malignant lymphoma.


Other malignant neoplasms


Diagnostic pearls: Usually non- to slightly hyperattenuating intracardiac filling defects: lymphoma (RV); angiosarcoma (atrial septum); malignant fibrous histiocytoma (LA); rhabdomyosarcoma (ubiquitous/intramyocardial).


Primary cardiac sarcomas are rare. Accidental finding on CT scans. MRI is modality of choice. Combined T1- and T2-weighted MRI imaging allows further differentiation between histologic subtypes.


Valvular


Aortic valve


Fig. 18.73a, b


Regurgítation or stenosis of the aortic valve.


Diagnostic pearls: Aortic valve stenosis: Typically associated with thickening, fusion with or without calcification of valve cusps or anulus, as well as with LV hypertrophy and poststenotic dilation of the aorta.


Aortic valve regurgitation: Dilation of aortic roof, aortic valve anulus, and ascending aorta. Valve may also show vegetations.


Calcifications may be better depicted on CT scans. Amount of calcifications correlates with 5-y risk of LV failure.


Functional parameters and valvular movement may be assessed on ECG-gated multiphasic CT scans. Echo/MRI is image modality of choice.


Bicuspid aortic valve is the most common cardiovascular malformation, occurring in 2% of the population. Usually asymptomatic.


Mitral valve


Regurgítation or stenosis of the mitral valve.


Diagnostic pearls:


Mitral valve stenosis: Typically associated with narrowing, thickening, fusion with or without calcification of valve cusps or anulus.


Often LA dilation and thrombi.


Mitral valve regurgitation: LA and LV dilation in chronic regurgitation. Valve vegetation indicates rheumatic or infectious origin of disease.


Calcifications may be better depicted on CT scans. Functional parameters and valvular movement may be assessed on ECG-gated multiphasic CT scans but are usually better depicted by MRI and echo.


Mitral valve prolapse describes midsystolic atrial bulging of thickened leaflets.


Pulmonary valve


Regurgítation or stenosis of the pulmonary valve.


Diagnostic pearls:


Pulmonary valve stenosis: Thickening, fusion with or without calcification of valve cusps or anulus; also, normal-sized heart and dilated pulmonary artery.


Aortic valve regurgitation: Dilated pulmonary artery, RV, azygos vein, and IVC/SVC.


Pulmonary valve stenosis is usually congenital: in 80% solitary, in 20% associated with other congenital heart diseases. Aortic valve regurgitation is a rare condition.


Echo/MRI is image modality of choice.


Tricuspid valve


Regurgítation or stenosis of the tricuspid valve.


Diagnostic pearls:


Tricuspid valve stenosis: Thickening, fusion with or without calcification of valve cusps; RA dilation (> 20 cm2).


Tricuspid valve regurgitation: Valve often not directly visualized; dilated RA, RV, and IVC; systolic contrast reflux into dilated hepatic veins.


Tricuspid valve stenosis is most commonly due to rheumatic heart disease. Tricuspid valve regurgitation may be idiopathic, infectious, traumatic, or due to rheumatic heart disease.


Carcinoid syndrome causes fibrous plaques on the tricuspid and pulmonary valve and is the second most common cause of tricuspid stenosis. Echo/MRI is the image modality of choice.

Fig. 18.49a–c Coronary artery atherosclerosis. On a transverse CT scan, a distinct hypodense area (a) within an otherwise hyperdense proximal right coronary artery (RCA) represents > 50% stenosis (arrow). Three-dimensional overview shows > 50% proximal stenosis (white arrow) and medial total occlusion (break-off; dashed arrow) of the RCA (b). Corresponding CPR shows partly calcified proximal > 50% stenosis (white arrow) and an overall hazy mid-RCA lumen (c), which is pathognomonic for a total occlusion (dashed arrow).
Fig. 18.50 Coronary artery bypass grafting (CABG). Venous graft to the RCA (bottom arrow). Left internal mammary artery (LIMA) graft to the left coronary artery (LCA) (top arrow). Note metal clips on the LIMA graft.
Fig. 18.51 Coronary artery segments according to the American Heart Association (AHA). (With kind permission from Springer Science + Business Media: Diagnostische und Interventionelle Radiologie, Kap. 21, Herz und Gefaesse, 2010, Vogl TJ, Reith W, Rummeny EJ. Figure 21.17.)
Fig. 18.52a, b Coronary artery aneurysm of the right coronary artery (RCA). Saccular, partly thrombosed, and calcified aneurysms in the complete RCA (a). Three-dimensional reconstruction shows additional aneurysms of the left coronary artery (b).
Fig. 18.53 Schematic drawing of left ventricle (LV) myocardial segments according to the AHA. On the short-axis views (a), the anterior wall is at 12 o’clock; the lateral wall is at 3 o’clock; the inferior wall is at 6 o’clock; and the septal wall is at 9 o’clock. Short-axis views are cut perpendicular to the long axis (b): segments 1 to 6 on short-axis views are located near the base of the heart (zone a on long axis drawing); segment 18 represents the apex (zone d). Segments 7 to 12 (zone B9) and 13–16 (zone c) lie within both. (With kind permission from Springer Science+Business Media: Diagnostische und Interventionelle Radiologie, Kap. 21, Herz und Gefaesse, 2010, Vogl TJ, Reith W, Rummeny EJ. Figure 21.24.)
Fig. 18.54 Myocardial ischemia. Ill-defined hypodensity within subendocardial myocardium of AHA segment 4 and 5 due to > 75% stenosis of the left circumflex (LCX).
Fig. 18.55 Acute myocardial infarction (MI). Ill-defined transmural hypodensity in AHA segment 4 and 5 due to total occlusion of the LCX.
Fig. 18.56 Chronic MI. Thinning of the myocardium with diminished transmural perfusion and presence of fatty deposits in subendocardial myocardium in AHA segment 7 to 9 due to middle left anterior descending artery (LAD) total occlusion.
Fig. 18.57 Chronic MI. Septal thinning and calcification due to chronic MI.
Fig. 18.58 Myocardial aneurysm. Partly calcified myocardial aneurysm of the cardiac apex with filling defect due to thrombus formation.
Fig. 18.59 Dilated cardiomyopathy. Increased left and right ventricular and atrial diameter.
Fig. 18.60 Pericardial effusion. Discrete apical fluid collection in a bilateral pneumothorax in a patient suffering from a severe blunt accident.
Fig. 18.61 Pericardial tamponade. Pericardial tamponade with marked fluid collection in the pericardial space and beginning of myocardial compression.
Fig. 18.62 Pericarditis calcarea. A thinned and heavily calcified pericardium. Concomitant pericardial enhancement indicates an active inflammatory process.
Fig. 18.63 Coronary artery anomalies. Common origin of LCA, LCX, and RCA from right sinus of Valsalva. The LCA is encased between the aorta and the pulmonary artery (malignant), whereas the LCX runs posteriorly to the aorta (benign).
Fig. 18.64 Pericardial cyst. Well-defined, waterlike, attenuating, thin-walled lobulated mass at the right anterior costophrenic angle.
Fig. 18.65 Congenital heart disease. Overview of most common types. (With kind permission from Springer Science+Business Media: Diagnostische und Interventionelle Radiologie, Kap. 21, Herz und Gefaesse, 2010, Vogl TJ, Reith W, Rummeny EJ. Figure 21.10.) ASD, atrial septal defect; VSD, ventricular septal defect; d. Botalli, ductus arteriosus Botelli.
Fig. 18.66 Fallot tetralogy. Large ventricular septal defect (VSD) with overriding aorta, stenosis of pulmonary artery (on the left side of the aorta), and right ventricular hypertrophy.
Fig. 18.67 Large apical VSD.
Fig. 18.68 Persistent ductus arteriosus (PDA) Botalli.
Fig. 18.69 Stenosis of the right pulmonary artery.
Fig. 18.70 Total anomalous pulmonary venous return. All four lung veins drain into the right atrium.
Fig. 18.71 Left atrial myxoma. Contrast-filling defect in an enlarged left atrium.
Fig. 18.72 Intracardiac metastasis of breast cancer. The cancer is seen nearly completely occluding the right atrium.
Fig. 18.73a, b Aortic valve stenosis. Aortic valve top view reconstruction shows thickening, fusion, and calcification of valve cusps (a). Left ventricular outflow tract (LVOT) MPR shows LV hypertrophy and poststenotic dilation of the aorta (b).






























































































































































Table 18.4 Thoracic calcifications

Disease


CT Findings


Comments


Focal parenchymal calcifications


Healed tuberculosis or fungal infection


Diffuse or laminated calcification of single or multiple nodules is characteristic.


Calcified ipsilateral hilar lymph nodes in combination with a focal calcification in the lung parenchyma (the primary or Ghon lesion) are called the primary or Ranke complex (see also Fig. 16.40 , p. 613).


Multiple pulmonary parenchymal lesions associated with splenic calcifications suggest histoplasmosis. Viable organisms may hibernate within calcified granulomas. Calcified pulmonary nodules due to previous infection with coccidioidomycosis are rare.


Broncholithiasis


Calcified endobronchial or peribronchial material that erodes, obstructs, or distorts the tracheobronchial tree. Distal mucous plugging and/or air trapping may be seen as a complication.


Uncommon disorder, most likely arising from previously infected (TB, histoplasmosis, etc.), calcified peribronchial lymph nodes that erode into and deform adjacent bronchi.


Hamartoma


Well-circumscribed, lobulated lesion measuring < 4 cm in diameter.


Stippled or scattered calcifications are often seen on CT, although not evident in chest radiographs. Nodules may contain both fat and calcium. The frequency of calcification increases with tumor size.


Benign nodule composed of disorganized, mature mesenchymal and epithelial tissue. Commonly contains both cartilage and adipose tissue. Usually an incidental finding. Endobronchial hamartomas occur infrequently.


Bronchial carcinoid


Well-circumscribed tumor located within lobular, segmental, or large subsegmental bronchi. Calcification occurs in > 25% of cases and is observed slightly more often in centrally located tumors.


Stems from the amine precursor uptake decarboxylase (APUD) group of tumors, arising from the Kulchitsky cells of the respiratory endothelium.


Bronchogenic carcinoma


Eccentric calcification within a soft tissue pulmonary mass, usually bronchus associated.


Bronchogenic carcinoma does not primarily calcify but may engulf a preexisting granuloma. Rarely, dystrophic calcification may develop in areas of tumor necrosis.


Calcified metastases


Solitary or multiple calcified intrapulmonary nodules with a lymphatic (involvement of subpleural space) distribution pattern (see also Fig. 16.88 , p. 629).


Pulmonary metastases of osteosarcoma are common but may not calcify when small.


Other neoplasms that may produce calcified metastases are synovial cell sarcoma, chondrosarcoma, mucinous adenocarcinoma, and thyroid neoplasms.


Parasitic diseases (echinococcosis, paragonimiasis)


A pulmonary hydatid cyst presents as a solitary cystic mass with a right lower lobe predominance (adjacent to liver).


In contrast to hepatic lesions, which commonly calcify, calcification of pulmonary hydatic cysts is rare. Thin-walled cysts, nodular and linear areas of increased opacity, focal air-space consolidation, and pleural effusions have been described in paragonimiasis. Calcification is a late phenomenon.


Echinococcosis is caused by two cestode species: Echinococcus granulosus and, less frequently, Echinococcus multilocularis. Lung involvement is observed in ~15% of cases.


Pulmonary paragonimiasis is caused by the liver fluke Paragonimus westermani, which is usually ingested with raw crayfish or crabs.


Pulmonary calcification due to other parasitic diseases is uncommon.


Bronchogenic cyst


Thin-walled cystic lesion with small curvilinear mural calcifications measuring up to a few centimeters in diameter.


Predominantly found in central parts of the lung or within the mediastinum.


Rare cause of pulmonary or mediastinal calcification. Bronchogenic cysts usually do not calcify.


Pulmonary arteriovenous (AV) fistula


Lobulated, well-defined, enhancing lung lesion. Precontrast scans may be able to identify calcified phleboliths within the lesion.


Most AV fistulas do not calcify. Feeding vessels are often identifiable.


Diffuse parenchymal calcifications


Healed histoplasmosis or varicella


Multiple micronodular pulmonary calcifications. Size and density of the nodules are best appreciated by using high-resolution CT.


If associated with both calcified mediastinal and calcified hepatic and splenic micronodules, histoplasmosis is the preferred diagnosis. Extrapulmonary calcified nodules are not a feature of healed varicella pneumonia.


Silicosis


Several small, randomly distributed nodules with a preference for middle and upper parts of both lungs. Central calcifications occur in 5% to 10% of cases and may be located subpleurally. Hilar and mediastinal lymphadenopathy is frequent. Occasionally, lymph nodes show circumferential calcifications (i.e., “eggshell” calcifications).


Silicosis-associated radiographic abnormalities occur after a latency period of up to 10 to 20 y after silica particle exposure. Complicated silicosis is characterized by development of progressive massive fibrosis (PMF) through coalescence of small nodules. PMF is commonly associated with local emphysema and may aggravate respiratory impairment.


Metastatic pulmonary calcification


Calcified alveolar septa, preferentially in the upper lung zones.


Numerous discrete septal calcium deposits due to combined hypercalcemia and hyperphosphatemia. Can occur with hyperparathyroidism, multiple myeloma, milk–alkali syndrome, hypervitaminosis D, sarcoidosis, and following iatrogenic calcium hyperinfusion.


Pulmonary alveolar microlithiasis


Diffuse ground-glass attenuation throughout both lungs.


An increased number of calcifications can be found along bronchovascular bundles and within the subpleural space. Concomitant interstitial fibrosis and subpleural cysts are found in more advanced cases.


Rare condition of unknown etiology, resulting in calcification of the alveolar space. Patients are usually 20 to 40 y of age at the time of diagnosis, may initially be clinically asymptomatic, and show normal serum calcium and phosphorus levels.


Late complications include respiratory failure and cor pulmonale.


Amyloidosis


Tracheobronchial amyloidosis: Characterized by multiple calcified nodules protruding into the trachea and bronchial wall, causing a bronchial obstruction.


Nodular pulmonary amyloidosis: Characterized by multiple well-defined, round or oval areas of consolidation that calcify in ~50% of cases.


Diffuse parenchymal amyloidosis: Nonspecific interstitial disease; does not calcify.


Extracellular deposition of insoluble fibrillar proteinaceous material. Approximately 10% of cases are primary or inherited.


Most cases of amyloidosis occur concomitantly with other diseases, including multiple myeloma, other plasma cell dyscrasias, and inflammatory processes. The disease occurs in middle-aged and elderly patients.


Respiratory involvement is observed in ~50% of patients.


Mitral stenosis


Two- to 8-mm noduli within alveolar spaces constituting mature bone. Predominance for lower lung zones. Comcomitant mitral valve calcification is common.


Associated with pulmonary venous hypertension and mitral valve disease.


Interstitial pulmonary ossification


Dendriform type: Diffusely branching areas of high attenuation, adjacent to the bronchovascular bundle. May be induced by scar formation or bronchiectasis.


Nodular type: Multiple subpleural micronoduli of increased opacity.


Rare condition observed in association with diffuse lung injury, such as interstitial fibrosis, pulmonary edema, or recurrent bronchopneumonia.


Dense areas in both subtypes are composed of mature bone. Presence of pulmonary ossifications has no prognostic significance.


Sarcoidosis


Speckled, amorphous, or popcorn-like calcifications of mediastinal lymph nodes.


Circumferential or “eggshell” calcifications are uncommon; miliary pulmonary calcifications are extremely rare (see Fig. 16.32 , p. 609).


Mediastinal lymph node calcifications occur in 3% to 10% of patients with sarcoidosis. Only diseased lymph nodes can calcify.


Hodgkin disease after therapy


Enlarged hilar and mediastinal lymph nodes with dense, coarse, or popcorn-like calcifications. Calcifications usually occur 1 to 9 y after radiation therapy, rarely after chemotherapy.


Superior mediastinal and hilar lymph nodes are the most commonly involved sites (> 95% of cases). Calcification in lymphoma before therapy is rare.


Pneumocystis carinii infection


Mediastinal nodal calcifications and calcified granulomas in parenchymal organs.


Has been reported in patients with acquired immunodeficiency syndrome (AIDS) who have P. carinii infection.


Pleural calcification


Healed empyema


Unilateral thickening and fibrosis of the visceral pleura that may contain coarse calcifications. Usually a thick layer of soft tissue is found between calcified visceral pleura and the chest wall.


Typically observed in patients with a known history of chronic pleural inflammation.


In the past, pleural injection of oil, an iatrogenic inflicted pneumothorax and thoracoplasty were used for treatment of TB, typically resulting in calcified pleural callosities.


Prior hemothorax


Unilateral thickening and fibrosis of the visceral pleura that may contain coarse calcifications. Soft tissue is seen between the chest wall and calcified pleura.


Known history of hemothorax must be present. Often posttraumatic rib changes are associated.


Asbestos exposure


Bilateral, sharply marginated linear thickenings and calcifications of the parietal pleura, most prominent along the diaphragmatic surfaces and in the lower half of the thorax (usually between the sixth and ninth ribs) (see Figs. 17.6 [ p. 632 ], 17.7 [ p. 632 ], 18.5 [ p. 641 ]).


May occur 20 y or more after exposure to asbestos or talc. Progresses over time.


Localized fibrous tumor of pleura


Focal thickening of the pleura that may contain calcification.


No relation to asbestos exposure.


Chest wall calcifications


Costochondral calcification


Coarse calcification of the cartilaginous portions of the ribs.


Prevalence increases with age: affects 6% of individuals aged 20 to 29 y and ~50% of patients > 70 y of age.


Posttraumatic calcification


Focal calcification in the soft tissues of the chest wall; not associated with bone.


Occurs after direct soft tissue or muscle injury, with subsequent dystrophic mineral deposition.


Dermatomyositis


Calcifications within the subcutaneous tissue and occasionally in the interfascial muscular planes of the chest wall.


Peak occurrence in the first and sixth decades of life; characterized by symmetric proximal muscle weakness with associated cutaneous rash and vasculitis.


Bone tumor


Calcific or osseous mass adjacent to ribs, vertebral bodies, or sternum (see Fig. 17.16 , p. 635).


Osteochondroma and chondrosarcoma are the most common calcified primary bone tumors affecting the chest wall. Fibrous dysplasia of the rib may be expansile and have a tumorlike appearance on CT.


Cardiovascular calcifications


Arteriosclerosis


Intimal calcification of the aorta and/or anulus. The mitral valve anulus is often calcified as well. Coronary artery calcification is most commonly seen in the proximal LCX artery (see Figs. 16.27a [ p. 607 ], 18.35 [ p. 653 ]).


Increased diameter of the aorta is indicative of an aneurysm. Coronary artery calcifications are associated with coronary artery disease and may be semiquantified according to the method of Agatston by using ECG-triggered CT of the heart.


Also, the amount of hydroxyapatite and the total plaque volume can be accurately measured.


Aortic valve disease


Stippled calcification of the aortic valve. If done without ECG triggering, streak artifacts due to cardiac motion are common (see Figs. 16.27a [ p. 607 ], 18.73a [ p. 668 ]).


Aortic valve calcification under the age of 50 is likely to be of rheumatic origin. Particularly if the aortic wall lacks calcifications, causes other than atherosclerosis are likely.


Irrespective of the underlying pathology, the amount of calcification is directly associated with left heart insufficiency: patients with intense calcification of the leaflets and anulus bear a 75% risk within the next 5 y.


Rheumatoid mitral valve disease


Usually difficult to visualize on chest CT scans due to motion artifacts.


Aortic valve and anulus calcifications are usually concomitant. Left atrial wall may be calcified as well.


Myocardial infarction (MI)


Usually LV wall calcifications, most commonly observed near the apex with or without aneurysmal dilation (see Fig. 18.57 , p. 663).


MI is the predominant cause. Calcified myocardial damage due to trauma, syphilis, myocarditis, rheumatic fever, or hyperparathyroidism is rare.


Pericarditis


Calcifications of the pericardium, most commonly observed near the atrioventricular groove (see Fig. 16.62 , p. 621).


Common causes of pericarditis include TB, rheumatoid fever, bacterial pneumonia, MI, viral infection, syphilis, histoplasmosis, asbestosis, and trauma.


Left atrial myxoma or thrombus


Partly calcified LA soft tissue mass. Motion artifacts may mask atrial myxoma on normal chest CT scans.


A calcified left atrial appendage is highly indicative of a calcified thrombus.


Ductus arteriosus


Calcification and associated motion artifacts at the site of the ductus arteriosus Botalli.


May be difficult to differentiate from aortic calcification; typically represents an occluded ductus.

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Jul 6, 2020 | Posted by in GENERAL RADIOLOGY | Comments Off on 18 Heart and Mediastinum
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