Respiratory system

Chapter 7 Respiratory system



Methods of imaging the respiratory system



1. Plain films

2. Computed tomography (CT)

3. Radionuclide imaging (V/Q scans)

4. Ultrasound (US) – for pleural disease

5. Magnetic resonance imaging (MRI)

6. Positron emission tomography (PET)


Further reading



Hansell D.M., Armstrong P., Lynch D.A., et al. Technical considerations. In Imaging of Diseases of the Chest, 4th edn, London: Elsevier/Mosby; 2005:1-26.


Klein J.S. Interventional chest radiology. Radiol. Clin. North Am.. 38(2), 2000.


Müller N.L. Computed tomography and magnetic resonance imaging: past, present and future. Eur. Resp. J.. 2002;19(35, suppl):3s-12s.



Computed Tomography of the Respiratory System





Indications



1. In the assessment of pulmonary masses

2. To exclude metastatic disease

3. In the assessment of diffuse infiltrative lung disease (high-resolution CT)

4. Arterial assessment (pulmonary emboli, aortic dissection)

5. In the assessment of bronchiectasis and large airway stenosis. Planning for therapeutic procedures to the airways, e.g. bronchial stent insertion.1


Technique



1. Volume scan – usually performed with intravenous contrast enhancement at a rate of 3 ml s−1 with a delay of 25–40 ml s−1 depending on the speed of the CT scanner. However, bolus tracking software can be used to specifically trigger the scan for the assessment of relevant vascular structures, e.g. aorta in suspected aortic dissection or pulmonary artery in suspected pulmonary embolism (see below).

2. High-resolution scan – usually performed without intravenous (i.v.) contrast:
a Patient lies supine but additional prone images2 may be required to confirm reversible dependent change

b On full inspiration, either incremental 1-mm slices at 10-mm to 20-mm intervals OR using multidetector scanner, volume scan with high-resolution reconstruction of 1-mm thick slices at 5–10-mm interval. A volume scan has the potential benefit of post-processing capabilities. Three-dimensional reformatting can help to illustrate the cranio-caudal distribution of pulmonary fibrosis, e.g. distribution of disease on coronal reformats

c Additional expiratory images can be performed in suspected air-trapping and airways disease

d Image reconstruction using ‘bone’ algorithm, i.e. high-resolution algorithm which reduces standard CT image smoothing

e Maximize spatial resolution using smallest field of view possible.


References



1 Boiselle P.M., Ernst A. Recent advances in central airway imaging. Chest. 2002;121(5):1651-1660.


2 Kashiwabara K., Kohshi S. Additional computed tomography scans in the prone position to distinguish early interstitial lung disease from dependent density on helical computed tomography screening patient characteristics. Respirology. 2006;11(4):482-487.



Further reading



Beigelman-Aubry C., Hill C., Guibal A., et al. Multi-detector row CT and postprocessing techniques in the assessment of diffuse lung disease. RadioGraphics.. 2005;25(6):1639-1652.



Computed Tomography-Guided Lung Biopsy





Indications



1. Investigation of a pulmonary opacity when other diagnostic techniques have failed to make a diagnosis

2. Investigation of a new chest lesion in a patient with a known malignancy

3. To obtain material for culture when other techniques have failed to identify the causative organism in a patient with persistent consolidation.

All biopsies should be planned after case discussion at a multidisciplinary meeting with a respiratory physician, radiologist and oncologist where the balance of benefit versus risk can best be assessed. Central lesions are preferably biopsied trans-bronchially either by standard bronchoscopy or transbronchial needle aspirate with endoscopic US guidance.



Contraindications



1. Vascular: bleeding diathesis, concurrent administration of anticoagulants, significant pulmonary arterial or venous hypertension. Vascular lesions such as aneurysms or arterio-venous malformations should have already been suspected at pre-biopsy discussion and should not be subjected to biopsy

2. Respiratory: contralateral pneumonectomy, presence of bullae or seriously impaired respiratory function, such that a pneumothorax could not be tolerated. The procedure should not be performed if the patient plans air travel within 6 weeks of the procedure

3. Suspected hydatid disease

4. Extremely uncooperative patient.


Equipment



1. Biopsy needle – fine needle aspirate can be performed if there is an on-site pathology service. Otherwise a cutting needle biopsy is used, of which there are several types available, e.g. Temno cutting needle or Cook Quick-Core. Coaxial needle biopsy systems can be used as these reduce the number of passes through the pleura. 18 or 20G needles are most often used

2. Full resuscitation equipment including a chest drain.


Patient preparation



1. Premedication with diazepam may be required. However, the patient must remain cooperative so that a consistent breathing pattern can be maintained during the procedure

2. The procedure may be performed on an outpatient basis with observation for 4–6 hours post procedure, but a bed should be available in case of complications

3. Clotting screen

4. Pulmonary function tests (spirometry).


Aftercare



1. Close observation post procedure for at least 1 h in a supervised ward or recovery area, preferentially with the patient lying in a position where the biopsy site is dependent, e.g. right lateral decubitus if right lateral biopsy

2. Chest X-ray in expiration at approximately 1 h post procedure. If a pneumothorax has developed then the further management will depend on the clinical condition of the patient. This may involve further close observation, aspiration or chest drain insertion, depending on the degree of patient dyspnoea and distress

3. High-risk patients such as those with pre-existing impairment of respiratory function are best admitted overnight.


Complications



1. Pneumothorax in 20%. However, a chest drain is necessary in only a small minority (about 3%). The incidence of pneumothorax is increased if:
a the operator is inexperienced

b larger bore needles are used

c there is an increased number of punctures

d small or central lesions are biopsied

e the needle traverses a fissure.

2. Local pulmonary haemorrhage (10%)

3. Haemoptysis (2–5%)

4. Other complications, such as implantation of malignant cells along the needle track, spread of infection and air embolism, are all extremely rare

5. The current documented death rate is 0.15%.


Further reading



Anderson J.M., Murchison J., Patel D. CT-guided lung biopsy: factors influencing diagnostic yield and complication rate. Clin. Radiol.. 2003;58(10):791-797.


Aviram G., Schwartz D.S., Meirsdorf S., et al. Transthoracic needle biopsy of lung masses: a survey of techniques. Clin. Radiol.. 2005;60(3):370-374.


Manhire A., Charig M., Clelland C., et al. BTS Guidelines: Guidelines for radiologically guided lung biopsy. Thorax. 2003;58(11):920-936.


Richardson C.M., Pointon K.S., Manhire A.R., et al. Percutaneous lung biopsies: a survey of UK practice based on 5444 biopsies. Br. J. Radiol.. 2002;75(897):731-735.



Methods of Imaging Pulmonary Embolism



1. Plain film chest radiograph. The initial chest radiograph is often normal. Numerous signs have been described in association with pulmonary embolism but, overall, the chest radiograph is neither specific nor sensitive.

2. Ventilation/perfusion (V/Q) radionuclide scanning. The technique is described later in this chapter. Interpretation of V/Q images is not clear-cut and there are a number of causes for the typical V/Q mismatch. Diagnostic criteria developed divide results into normal, low-probability, intermediate (or indeterminate) and high-risk groups. Specificity and sensitivity are such that, if the criteria place the images in the normal group, pulmonary embolism is virtually excluded and if the images fit the criteria for high risk it is very likely (85–90%). In the intermediate risk group specificity is poor and further imaging may be required.

3. Doppler ultrasound of leg veins to confirm deep vein thromboses.

4. Multidetector CT pulmonary angiography

Related posts:

Default ThumbnailLiver, biliary tract and pancreas Default ThumbnailReproductive system Default ThumbnailBreast General notes Arterial system Bones and joints

Stay updated, free articles. Join our Telegram channel
Tags:
Feb 20, 2016 | Posted by in GENERAL RADIOLOGY | Comments Off on Respiratory system

Full access? Get Clinical Tree
Get Clinical Tree app for offline access