Practice Questions
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Question 1:
a) What is a quick way to assess for reduced lung volumes on a frontal chest radiograph?
Compare width to length for the lungs overall--if the lungs are TALLER than WIDE, the volumes are likely normal. If they are EQUAL, the lung volumes are probably reduced. If they are WIDER than TALL, the lung volumes are definitely reduced.
b) Where is the best place to look to determine if lung volumes are increased on chest radiography?
The lateral view is the best for assessing hyperinflation, as flattening of diaphragms is often seen sooner on the lateral than on the frontal view.
c) How far out on a frontal radiograph can you normally see bronchi?
Bronchi are generally well seen where they overly the mediastinal soft tissues, but are hard to visualize when normal much beyond the hilum. Even in the hilum, they may be hard to see unless they are pointed directly to the front or back, so that they appear as a ring.
d) How far out into the lung can you normally see vascular markings on an upright frontal chest radiograph?
Vascular markings should not be visible generally in the outer 1/3 of the chest, and vessels are larger comparing lower and mid lung zones to upper lungs, due to the effect of gravity.
Question 2:
a) What portions of the lung better seen on the lateral chest radiograph than the frontal?
The lowermost parts of the lower lobes are better seen on the lateral view than the frontal, as they are very deep and are obscured by the diaphragms on the frontal view. The middle lobe is partly overlapping the heart on the frontal view, and is better seen on the lateral view.
b) What pleural structures are better seen on the lateral chest radiograph than the frontal?
The major fissures are better seen on the lateral view than the frontal, as they are oriented to appear as lines. On the frontal view, they are seen en face, so they do not appear linear.
c) Which view (frontal or lateral) is most sensitive for detection of small pleural effusions?
The lateral view shows small pleural effusions best, as the POSTERIOR costophrenic angles are deeper than the LATERAL costophrenic angles (visible on the frontal view). So a very small pleural effusion will be visible on a lateral radiograph, but may not be seen on the frontal radiograph.
Question 3:
a) What structures are present in the center of the secondary pulmonary lobule, and are they normally visible on chest radiography and CT?
A small branch of the pulmonary artery and an accompanying bronchus are present in the center of the secondary pulmonary lobule. Neither are well seen on normal chest radiography, as they are too small and there is too much overlap. On chest CT, you can see the pulmonary artery branch, but in the lung periphery the bronchus is usually too small to see on CT if normal.
b) What structures are present in the periphery of the secondary pulmonary lobule, and are they normally visible on chest radiography and CT?
The connective tissue of the secondary lobule septa (separating adjacent secondary lobules) is not normally visible on radiography or CT. The small branches of the pulmonary veins run in the same region as the lobular septa, and are visible on CT, but not on radiography, as they are too small and there is too much tissue overlap.
c) What is the chest radiographic appearance of thickening of the secondary pulmonary lobular septa?
Thickening of secondary lobular septa in the central parts of the lungs contribute to overall increased density and sometimes produce a reticular pattern of criss-crossing lines. But in the periphery, near the pleura, thickened septa produce Kerley B lines--short horizontal lines that meet the pleura in the outer 1/3 of the lung, where normally no distinct markings are visible.
d) What is the CT appearance of thickening of the secondary pulmonary lobular septa?
Thickening of secondary lobular septa on CT results in a network of thin polygons that can be seen in any part of the lung where thickening is present.
Question 4:
a) What is the normal morphology of bronchi on CT, and how are they related to vascular structures?
Bronchi should be smooth and thin-walled with central air, and should taper to become invisible in the outer 1/3 of the lung. Large bronchi can sometimes be visible in the middle third of the lung, and are generally easy to see in the inner third of the lung. Bronchi are in close association with pulmonary artery branches throughout the lung
b) What are important features of lung abnormality to note on CT?
It is important to decide whether increased lung density is normal (dependent density in the lowest part of the lung, due to effects of gravity), or abnormal, and to characterize it in terms of whether it is linear and well-defined, vs hazy or ill-defined. The distribution of abnormality is also helpful, including central vs peripheral and upper vs lower lung zones.
c) What CT technical parameters are important when assessing lung abnormalities?
If vascular disease is suspected, then IV contrast should be given, with timing to optimize opacification of the pulmonary arteries. For lung disease, no IV contrast is needed. If there is a question of dependent density, prone imaging may be performed, since this should make the density shift to the anterior lungs.
d) What are air bronchograms and what part of the lung do they involve?
Air bronchograms are normal bronchi that are visible farther out into the lung than normal (on both CXR and CT) because the lung surrounding them is ABNORMAL (airspace disease). Normally, the lung is filled with air and so are the bronchi, so the bronchi cannot be seen very far out into the lung. But if the lung becomes opaque (filled with abnormal material, such as pus, blood, fluid or tumor), then the normal bronchi become visible. Air bronchograms are always better seen on CT than CXR.
This completes the Pre-Class material on Normal Imaging of Lungs and Pleura.
You will apply this knowledge in the first In-Class Interactive session. You will get more out of this session if you have reviewed this material before coming to class.
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