ABC-Primer of CT Evaluation




ABC-Primer of CT Evaluation


Occasionally, the beginner faces the question to decide whether a finding represents a true lesion or just an artifact. A contralateral comparison or a comparison with adjacent cranial or cauda sections can often be helpful. Furthermore, uncertainty arises when describing a lesion without familiarity with the appropriate vocabulary. This primer aims to remedy these problems.



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General Approach to an Abnormality of the CT Morphology:


Where ?


Location, lateralization, relative position to other organs/vessels


Size ?


Size (diameter in [mm, cm]; important, e.g., monitoring of therapy)


Density ?


Relative to its surrounding: isodense (equal density); hyperdense (denser); or hypodense (less dense)


Structure ?


Homogenous (e.g., fluids) or heterogenous / septate / geographic


Shape ?


Tubular (vessels, muscles, …) or nodular (tumor, lymph nodes)? Reticular (resembling a net), striate or diffuse?


Demarcation ?


Sharply marginated (more likely benign) or indistinctly marginated (infiltration into the surrounding, e.g., inflammation, malignancy) Caution: Partial volume effect can mimic an indistinct margin!


Perfusion ?


No, peripheral, homogenous or heterogenous contrast enhancement


Expansion ?


Space-occupying effect not invariably a sign of malignancy: e.g., large benign cysts can displace adjacent vessels



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Useful Terms, in Alphabetic Order


( Application, Possible Significance)


Air inclusions


Infection with gas-forming bacteria
compound fracture


Ampullary


Dilatation of the renal pelvis
( physiologic variant or obstructive uropathy)


Articular involvement


Evaluation of fractures ( risk of degenerative osteoarthritis)


Bolus CT


Dynamic examination, often without table movement to assess the contrast enhancement pattern


Bullae


Lung ( pulmonary emphysema)


Capping


Periventricular abnormality in the white matter ( transependymal diffusion of CNS; sign of SAE)


Cavity


Intrapulmonary hollow space ( tuberculosis)


Central


In the center of a lesion or close to the hilum of parenchymatous organs


Clubbing


e.g., of a limb of the adrenal gland ( adenoma, metastases)


CM


Contrast medium, given orally, rectally or intravenously


Concentric


Location of intravascular thrombi ( aortic aneurysm)


Course of fracture lines


Evaluation with additional MPR ( surgical planning)


Crescentic


Typical configuration, e.g., subdural hematoma or perihepatic effusion / ascites


Defect


Pathologic phenomenon in opacified vessels / urinary collecting system


Defect


In opacified vessels ( thrombus), in urinary bladder ( tumor, blood clot)


Demarcation


Depending on the vascularization, lesions become visible only after administration of contrast medium


Dense band


Band-like density ( lung, connective tissue: post-inflammatory, scar)


Densitometry


Measuring of density ( differential diagnosis)


Diffuse


Uniform, neither focal nor nodular; e.g., liver: hypodense hepatic steatosis (fatty liver) hyperdense hemochromatosis


Dumbbell-like


Typical calcification pattern of benign hamartomas ( lung)


Eggshell-shaped


Calcification pattern of perihilar lymph nodes (lung silicosis; porcelain gallbladder)


Enhancement


Increased density due to accumulation of contrast medium


Enhancement pattern


Perfusion pattern (homogenous, timely or delayed)


Excentric


Intravascular location of thrombi ( aortic aneurysm)


Fluid Levels


Phenomenon ( sedimented hematoma) or air-fluid levels ( paralytic ileus or intestinal obstruction)


Fractures


Cortical step deformity, displacement, number of fragments, stability, articular surface?


Ground glass density


Diffuse, slight increase density seen in perifocal edema ( fat, lung)


Halo


Confined perifocal edema ( around inflammatory foci and metastases)


Hemorrhagic


Blood-containing ( large infarcts, e.g., cerebral)


Hilar fat


Benign criterion for lymph nodes ( nodal index)


Honeycombing


Typical for vascular rarefaction in the lung ( emphysema)


HRCT


High resolution computed tomography (thin sections) ( lung; also for MPR and 3D)


Hyperdense


Denser than the surrounding tissue
(bright fresh cerebral bleeding or calcification)


Hyperperfusion


Enhancement ( inflammation, hypervascular tumor)


Hypodense


Less dense than the surrounding (dark fluid, fat, air)


Imbibition


Striate to diffuse enhancement ( fatty tissue: scar, inflammation)


Indentation


Blunt convex bulging / displacement of adjacent structures ( tumors)


Indistinct


Outline of a lesion (see marginal indistinctness)


Indistinct margin


Caused by inflammatory and tumorous infiltration of the surrounding tissue (caution: DD partial volume effect)


Induration


Thickened fibrous tissue ( scar, pulmonary fibrosis)


Infiltration


Perifocal extension of an inflammatory or malignant process


Inflow effect


Incomplete mixing of contrast medium, can mimic intravascular thrombi


Intramural


Located in the wall of a hollow viscus ( gas, tumor)


Iris effect


Centripetal enhancement ( hepatic hemangiomas)


Isodense


As dense as … (= isointense)


Jet effect


Inflow of opacified urine from the ureter into the urinary bladder


Lacuna


Lacunar defect ( late stage after cerebral infarct, isointense with CSF)


LN


Lymph node (for size see checklists, hilar fat)


Lymphangiomatosis


Ground glass-density ( pulmonary parenchyma, breast carcinoma)


MPR


Multiplanar reconstruction of various image planes (sagittal, coronal diagnostic evaluation of e.g. fractures)


Multiphase technique


Data acquisition during early arterial, portovenous or late venous passage of the contrast medium bolus ( spiral CT of the liver)


Multislice


New multislice technique consisting of simultaneous acquisitions of several sections in spiral mode


Mural thickness


Single or multiple layers (wall of a hollow viscus: ischemia, inflammation)


Narrowed parenchymal rim


Renal atrophy (degenerative, hydronephrosis)


Necrosis


Central, hypodense or homogenous liquefaction


Nodal index


Longitudinal-transverse diameter ratio (characterization of lymph nodes)


Nodular


Nodular configuration ( lymph nodes, tumors, adenomas), miliary < granular < fine-nodular < large-nodular < confluent ( pulmonary interstitium)


Obliterated


Surface of cerebral gyri ( cerebral edema, DD: child) or pancreas outline ( acute pancreatitis)


Osteolytic


Destruction of bony matrix ( metastases, multiple myeloma)


Osteoproliferative


Osseous apposition ( degenerative), less frequent due to sclerotic metastases


Partial volume effect


Effect of partial volume (causes apparent indistinctness)


Patchy


Parenchymal perfusion pattern in the spleen during the early arterial phase


Perifocal


Circular around a lesion (edematous zone)


Perihilar


Topographic description of an intrapulmonary lesion


Peripheral


Along the periphery, in contrast to central


Pitch


Ratio of table feed per rotation and section thickness ( spiral technique, see p. 8 / 9)


Pixel


Picture element (image formation, see p. 14)


Plaque


Intravascular ( arteriosclerosis), pleura-based ( asbestosis)


Polycyclic


= scalloped, cauliflower-like ( hilar lymph nodes of the lung, e.g., Boeck’s disease)


Popcorn


Typical pattern of benign calcifications ( lung)


Process


Favored term for “I don’t know what is means”


Pseudocysts


chronic pancreatitis


Pulsation


Can induce artifacts along vessels ( aortic aneurysm)


Rarefaction


Less vessels per pulmonary volume ( emphysema, S/P lobectomy)


Respecting soft-tissue planes


Lacking in malignant tumors or advanced inflammations (no longer respecting natural borders => infiltration)


Retention cyst


Convex projection into the paranasal sinus, homogenous


Reticular


Net-like pattern ( fibrosis of the pulmonary interstitium)


Retrocrural


Preferred posterior paravertebral lymph node station


Risk of herniation


Internal herniation of brain stem due to increased intracranial pressure
( quadrigeminal and ambient cisterns)


ROI


Region of interest ( densitometry)


Round lesion


Focal space-occupying lesion (only intrapulmonic)


Scalloped enhancement


Peripheral contrast enhancement ( glioblastoma)


Site of predilection


Preferred site for certain changes ( lymph nodes, metastases)


Sludge


Thickened bile ( cholestasis, cholecystitis)


Space-occupying process


Tumor of unknown nature (ubiquitously applicable)


Spindle-shaped


Biconvex configuration ( aortic aneurysm; epidural hematoma)


Spiral CT


Acquisition of a 3D data set with continuous table feed and any section reconstruction, see p. 7


Stellar


Hypodense star-like figure ( FNH of the liver)


Stellate


Septation ( echinococcal cyst)


Stent


Short tube of various materials to stent vessels, ureter or common bile duct


Step deformity


bony cortex ( fracture diagnosis)


Structure


Non-descriptive term of a lesion, try to use more precise term


Subcarinal


Preferred lymph node station


Timely


Symmetric and timely renal enhancement and excretion of contrast medium = normal


Triangular


Wedge-shaped ( typical infarct pattern, scar residue)


Tumor extension


Renal vein or vena cava ( renal tumor)


Vascular configuration


Normal configuration of the pulmonary hila


Voxel


Volume element (image formation, see page 14)


Wedge-shaped


Triangular configuration ( typical infarct pattern, scar residue)

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Jul 17, 2021 | Posted by in ULTRASONOGRAPHY | Comments Off on ABC-Primer of CT Evaluation
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