Practice Questions
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Question 1:
a) What is the proper term for describing a rounded opacity in the lung on chest radiography with smooth margins measuring 2 cm in diameter?
If a lung opacity is under 3 cm, and has a smooth rounded margin, it can be called a nodule.
b) What is the proper term for describing an irregular, speculated opacity in the lung on chest radiography measuring 2 cm in diameter?
Any lung opacity that is not smooth and rounded in shape should be called a mass, regardless of size. And even rounded opacities should be called masses if they are larger than 3 cm.
c) What are sites of spread of lung cancer that might be seen on chest radiography?
Lung cancer can spread to lymph nodes (hilar or mediastinal), to the pleural surface (producing an effusion), or may directly invade structures such as the trachea or mediastinal vessels and nerves. Invasion of structures indicates a higher stage and poorer prognosis.
Question 2:
a) What is the appearance of adenopathy on chest CT in lung cancer?
Lung cancer often spreads to nodes, hilar or mediastinal, and will produce enlargement that is usually uniform, without calcification.
b) Which nodes on chest CT are often the first site of spread of lung cancer?
The first nodes that are often involved in lung cancer are ipsilateral hilar nodes, so this would indicate a relatively low stage, compared to other nodal sites.
c) Which nodes on chest CT are indicative of higher stage in lung cancer?
After spread to hilar nodes, lung cancer often spreads to ipsilateral mediastinal nodes, then contralateral mediastinal nodes, and then more distant sites. So finding nodes that are on the opposite side from the original lung tumor is particularly important and indicates a higher stage of disease and poorer prognosis.
Question 3:
a) What internal control can be used to determine if pulmonary arteries are enlarged on chest radiography?
Since the volume of blood in the aorta (most easily seen at the arch, outlined by lung and trachea) should be equal to the volume of blood in the two main pulmonary arteries (most easily seen in the hilar regions), this can serve as an internal control for patient size in assessing pulmonary arteries. Each pulmonary artery in the hilum should be approximately half the diameter of the aortic arch.
b) What part of the chest is the causative site of disease in most cases of pulmonary artery hypertension?
The lungs are usually the causative site of disease that leads to pulmonary artery hypertension. Anything that damages the lung capillary bed can raise the pressure in the pulmonary circuit, and result in enlarged pulmonary arteries on chest radiography.
c) What are three possible causes of pulmonary artery hypertension?
Fibrotic lung disease, emphysema, and chronic left to right shunts (like atrial septal defect) can all damage the lung and lead to pulmonary artery hypertension. Multiple or chronic pulmonary embolism can also produce pulmonary artery hypertension. Primary pulmonary artery hypertension is an idiopathic disease that occurs without known predisposing heart or lung abnormalities.
d) What is a cause of enlargement of a distal pulmonary artery on chest radiography?
Enlarged and tortuous peripheral pulmonary vessels are most often caused by arterio-venous malformations (AVM for short), and can be seen in hereditary hemorrhagic telangiectasia (HHT), also called Osler-Weber-Rendu syndrome. This genetic disorder leads to bypassing of the normal lung capillary bed at the site of AVM, and can result in stroke from small blood clots that are not trapped in the lung and make their way to the brain.
Question 4:
a) What is the typical appearance of pleural effusion on upright chest radiography?
Pleural effusion in the upright position layers inferiorly, resulting in a sharply marginated opacity with a meniscus (fluid creeping up the lateral margin of the pleural space due to surface tension).
b) What is a pleural pseudotumor and how does it look on chest radiography?
A pleural pseudotumor is a localized collection of fluid in one of the fissures, most often the minor fissure that can simulate a lung mass. In this situation, the flat plate of fluid (best seen on the lateral view) may appear as a an oval or lens-shaped mass (often with indistinct margins on at least one side) on the frontal view.
c) What is the significance of pockets of air in a pleural effusion on chest radiography or CT?
Air may be introduced into the pleural space by procedures (biopsy, chest tube placement), but if no instrumentation has occurred, pockets of air in a pleural effusion should suggest empyema (infection).
d) What is the typical chest radiographic appearance of mesothelioma?
Mesothelioma, a malignant tumor of the pleura most often associated with asbestos exposure, most often appears as a diffuse thickening or rind around the lung on one side.
e) What is one benign pleural tumor, and can it be identified on CT?
Pleural lipoma is a benign fatty tumor that can occur in the pleura, and may simulate a lung mass on chest radiography, but demonstrates fat density on CT, indicating the proper diagnosis.
This completes the Pre-Class material on Imaging of Lung Cancer, Pulmonary Vascular and Pleural Disease.
You will apply this knowledge in the second 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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