Opening Round

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Opening Round

1 Which imaging feature of this nodule is of concern for malignancy?

2 Which cell type of lung cancer is most likely?

3 What are the size criteria for a T2a lesion in the recent revision of the TNM (tumor-node-metastases) staging system?

4 Is this lesion better suited to image-guided transthoracic needle biopsy or bronchoscopic biopsy?

1 Spiculated margins.

2 Adenocarcinoma.

3 >3 cm but ≤5 cm in greatest dimension.

4 Transthoracic needle biopsy.

Müller NL, Silva CIS: Nodules and masses. In: Silva CIS, Müller NL, Eds. Imaging of the Chest. Philadelphia, Saunders, 2008, pp 136-157.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 284-286.

A solitary pulmonary nodule is defined as a well-circumscribed round or oval lesion measuring less than 3 cm in diameter. There are only two specific and reliable signs of benignancy on chest radiographs: (1) identification of a benign pattern of calcification or (2) demonstration of absolute absence of growth over a 2-year period. For cases that do not meet one of these criteria, thin-section CT is generally recommended for further evaluation. In comparison with radiography, CT allows a more accurate assessment of the margins of a nodule; moreover, CT is more sensitive for identifying the presence and distribution of calcium and fat within a nodule.

The nodule in this case has spiculated margins, a finding that is highly suspicious for malignancy. Depending on local practice patterns and clinical circumstances, a preoperative biopsy may be requested. The peripheral location of this nodule makes it best suited for a transthoracic needle biopsy.

The most common cell type of lung cancer is adenocarcinoma. It most often presents as a solitary, peripheral nodule with spiculated margins. Based on size criteria outlined in recent revisions to the TNM staging system for lung cancer, this 4.0-cm mass is a T2a lesion. The revisions establish the following size cut-off points for T designations: T1a: tumor ≤2 cm in greatest dimension; T1b: tumor >2 cm but ≤3 cm in greatest dimension; T2a: tumor >3 cm but ≤5 cm in greatest dimension; T2b: tumor >5 cm but ≤7 cm in greatest dimension; T3: tumor >7 cm (see Thoracic Radiology: THE REQUISITES, Table 11-1).

1 What is the cause of this patient’s pleuritic chest pain and dyspnea?

2 Name at least five causes of pneumothorax.

3 Based on the imaging findings in this case, what is the most likely cause for this “spontaneous” pneumothorax?

4 What radiographic finding(s) in this case suggests the possibility of a tension pneumothorax?

Spontaneous Pneumothorax Secondary to Ruptured Bleb

1 Pneumothorax.

2 Spontaneous, chronic obstructive pulmonary disease, chronic infiltrative lung disease (e.g., Langerhans cell histiocytosis and lymphangioleiomyomatosis), malignant neoplasms (e.g., metastatic sarcoma), trauma, catamenial pneumothorax, iatrogenic, barotrauma, and infection (e.g., lung abscess and septic infarcts).

3 Ruptured apical bleb.

4 Depression of the left hemidiaphragm; expansion of the left rib cage.

O’Connor AR, Morgan WE: Radiological review of pneumothorax. BMJ 330:1493-1497, 2005.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 386-389.

Pneumothorax is defined as the presence of air or gas within the pleural space. Although there are a wide variety of causes, spontaneous pneumothorax is the most common etiology. Affected patients are usually in the third or fourth decade of life.

Spontaneous pneumothoraces are almost always secondary to rupture of an apical bleb, which represents a gas pocket within the elastic fibers of the visceral pleura. Note the presence of a small bleb along the visceral pleural margin in this patient, best demonstrated on the coned-down image of the left upper lobe (arrow, second figure). Such blebs have been reported to be detectable on chest radiographs in approximately 15% of cases of spontaneous pneumothorax. However, blebs are rarely evident on chest radiographs following resolution of the pneumothorax. CT is much more sensitive than radiography for detecting blebs and has been shown to detect blebs in approximately 80% of patients following resolution of spontaneous pneumothoraces. The size and number of apical blebs detected on CT have been shown to correlate with the risk of recurrent pneumothoraces and the need for surgical intervention.

Tension pneumothorax is a life-threatening condition. Affected patients present with clinical signs of tachypnea, tachycardia, cyanosis, sweating, and hypotension. Radiographic findings may include contralateral mediastinal shift, diaphragmatic depression, rib cage expansion, and flattening of the contours of the right heart border and/or venae cavae.

1 Where is this central venous catheter located?

2 Should the catheter be repositioned?

3 What is the most common complication of inadvertent placement of a catheter in this location?

4 Is inadvertent azygos vein cannulation more common following a left- or a right-sided vascular insertion approach?

Malpositioned Catheter in the Azygos Vein

3 Venous rupture.

Bankier AA, Reinhold M, Weismayr MN, et al: Azygos arch cannulation by central venous catheters: radiographic detection of malposition and subsequent complications. J Thorac Imaging 12:64-69, 1997.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 140-144.

Inadvertent insertion of a catheter into the azygos vein is a relatively uncommon complication of central venous catheter placement, with an estimated frequency of approximately 1%. Detection of a malpositioned catheter at this site is important, because there is a relatively high frequency of associated venous perforation.

Note the abnormal curve of the catheter at the level of the azygos arch on the posteroanterior (PA) chest radiograph. The precise location is confirmed on the lateral chest radiograph (second figure), which demonstrates the posterior course of the catheter within the azygos arch.

Interestingly, azygos vein cannulation occurs most commonly following left-sided catheter insertion. This association is thought to occur secondary to anterocaudal arching of the left brachiocephalic vein, which may preferentially promote entry of a catheter into the azygos vein rather than the superior vena cava. In contrast, catheters placed from the right side of the thorax have a more direct course to the superior vena cava via the right brachiocephalic vein.

1 Based on the imaging findings in this case, name several likely prior occupational settings for this individual.

2 Are pleural plaques from prior asbestos exposure usually unilateral or bilateral?

3 Are these lesions symptomatic?

4 Are pleural plaques premalignant?

Calcified Pleural Plaques From Prior Asbestos Exposure

1 Mining, insulation manufacturing, textile manufacturing, construction, ship building, and brake lining manufacturing and repair.

McLoud TC: Conventional radiography in the diagnosis of asbestos-related disease. Radiol Clin North Am 30:1177-1189, 1992.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 206-213.

The chest radiograph demonstrates numerous partially calcified lesions bilaterally, several of which are plateau-like in configuration and parallel the inner margin of the lateral thoracic wall and the right hemidiaphragm. CT confirms the pleural location of these lesions and demonstrates the calcification more precisely. The findings are typical of pleural plaques related to prior asbestos exposure.

Pleural plaques are the most common manifestation of asbestos exposure and typically occur after a latency period of approximately 15 to 20 years. They do not cause symptoms and are usually discovered incidentally. Pathologically, pleural plaques are composed of dense bands of avascular collagen and are not considered premalignant lesions.

The radiographic appearance of pleural plaques is dependent on whether the plaques are calcified, and whether they are seen in profile or en face. When observed in profile, a plaque appears as a dense band of soft tissue opacity paralleling the inner margin of the lateral thoracic wall or an adjacent hemidiaphragm. When observed en face, a plaque appears as a veil-like opacity with irregular edges, often described as a “holly leaf” configuration. Plaques are usually bilateral and often symmetric. The lower half of the thorax is most often affected, usually between the sixth and the ninth ribs.

1 Displacement of the paraspinal lines implies an abnormality in which mediastinal compartment?

2 Are thoracic vertebral body fractures commonly associated with mediastinal hematoma?

3 How reliable are portable chest radiographs and thoracolumbar radiographs for detecting spinal fractures?

4 Which portion of the spine is most susceptible to traumatic injury?

Vertebral Body Fracture With Paraspinal Hematoma

3 Not very reliable.

4 The thoracolumbar junction (T12-L2).

Wintermark M, Mouhsine E, Theumann N, et al: Thoracolumbar spine fractures in patients who have sustained severe trauma: depiction with multi-detector row CT. Radiology 227:681-689, 2003.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 162, 165, 166, 375, 377.

Thoracic spine fracture is an infrequent but serious complication of blunt trauma. Unfortunately, the portable trauma chest radiograph is not very reliable in detecting spinal fractures. Moreover, thoracolumbar spine radiographs have been shown to have a sensitivity of only 32% for detecting acute spinal fractures.

Radiographic findings associated with spinal fracture include findings related to mediastinal hemorrhage (such as widening of the paraspinal lines, mediastinal widening, and left apical pleural cap) and vertebral abnormalities. The latter are more specific for spinal injury and include loss of height of the vertebral body and obscuration of the pedicle(s). When you identify a mediastinal hematoma that is confined to the posterior mediastinum, you should diligently search for evidence of a vertebral body fracture. If a spinal fracture is not evident on chest radiography, you should proceed to CT. Multidetector CT (MDCT) has been shown to have a much higher sensitivity than radiographs for detecting fractures and its sensitivity can be further enhanced by coronal and sagittal reformations.

1 What are the two major chest radiographic features of emphysema?

2 What is the best chest radiographic indicator of overinflation of the lungs?

3 Is the chest radiograph a reliable tool for detecting emphysema?

4 What is the most sensitive imaging modality for detecting emphysema?

1 Overinflation of the lungs and reduced vascularity.

2 Flattening of the hemidiaphragms.

4 High-resolution CT (HRCT) of the chest.

Webb WR: Radiology of obstructive pulmonary disease. AJR Am J Roentgenol 169:637-647, 1997.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 242-248.

Emphysema is defined as permanent, abnormal enlargement of airspaces distal to the terminal bronchiole, accompanied by destruction of their walls.

Radiographic abnormalities in patients with emphysema are related to overinflation of the lungs and lung destruction. The latter is characterized by reduced vascularity or the presence of bullae. Overinflation of the lungs may be characterized by a number of findings, most notably flattening of the hemidiaphragms and an increase in the retrosternal airspace diameter.

Chest radiographic abnormalities are usually evident in moderate to severe cases of emphysema, but radiographs are frequently normal in patients with early emphysema. HRCT is superior to chest radiographs in detecting and characterizing emphysema and has a high sensitivity and specificity for establishing the diagnosis.

1 What infection is most commonly associated with this pattern?

2 In cases of miliary tuberculosis (TB), how is the infection disseminated to the lung?

3 What other type of infection commonly presents with a miliary pattern?

4 Name four noninfectious entities that may present with a miliary pattern.

Miliary Tuberculosis

2 Hematogenously.

3 Fungal infection.

4 Pneumoconioses (e.g., silicosis), Langerhans cell histiocytosis, sarcoidosis, and metastases (e.g., thyroid, melanoma).

Reed JC: Diffuse fine nodular opacities. In: Chest Radiology: Plain Film Patterns and Differential Diagnoses, fifth edition. Philadelphia, Mosby, 2003, pp 287-303.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 104, 105.

A miliary pattern refers to the presence of numerous small (approximately 1- to 2-mm-diameter) lung nodules. Such nodules are difficult to detect radiographically because of their small size. It has been suggested that these tiny nodules become visible radiographically because of the effect of summation.

The classic entity associated with this pattern is miliary TB, which refers to the diffuse hematogenous dissemination of TB. This pattern typically occurs in patients with altered host resistance to the primary infection. Affected patients usually present with fever, chills, and night sweats.

Because of the small size of miliary nodules, it is not surprising that CT (particularly HRCT) is more sensitive than radiography for detection. In fact, it has been estimated that it may take up to 6 weeks for miliary nodules to become apparent on chest radiographs! On HRCT, the nodules are shown to be diffuse and random in distribution.

1 Where are the nodular opacities located?

2 What imaging feature on the PA radiograph suggests this location?

3 What is the most common chest wall structure to appear as a nodular opacity on a chest radiograph?

4 How can you confirm a suspected cutaneous site of a nodular opacity using chest radiography?

2 Incomplete, sharp borders.

4 Repeat the radiograph with a small lead marker on the site of the cutaneous abnormality.

Reed JC: Chest wall lesions. In: Chest Radiology: Plain Film Patterns and Differential Diagnoses, fifth edition. Philadelphia, Mosby, 2003, pp 6-24.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 40-41.

When visible on chest radiographs, cutaneous chest wall lesions such as neurofibromas, moles, and nipples demonstrate a characteristic incomplete, sharp border. The sharp border is produced by the interface of the lesion with adjacent air, and it becomes incomplete where the lesion is continuous with the soft tissues of the chest wall. The identification of such a border is helpful for differentiating chest wall lesions from intrapulmonary lesions.

In this particular case, the cutaneous location of the nodules is easily confirmed on the lateral projection. When in doubt about a possible cutaneous location of a focal nodular opacity, one should perform a repeat radiograph with small lead markers for confirmation.

1 What is the diagnosis?

2 Name two primary signs of atelectasis.

3 Name five secondary signs of atelectasis.

4 What is the most common mechanism for complete lobar collapse?

Complete Left Lower Lobe Atelectasis

1 Complete left lower lobe atelectasis.

2 Opacification of the affected lobe and displacement of the interlobar fissures.

3 Elevation of the hemidiaphragm, mediastinal shift, displacement of the hilum, compensatory hyperinflation, and crowded vessels.

4 Obstruction of a central bronchus.

Woodring JH, Reed JC: Radiographic manifestations of lobar atelectasis. J Thorac Imaging 11:109-144, 1996.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 31-40.

Atelectasis is defined as a decrease in volume (i.e., reduced inflation) of all or a portion of the lung. The most common type of atelectasis occurs secondary to obstruction of a central bronchus. It is referred to as resorption atelectasis and usually involves an entire lobe.

The chest radiograph and CT image reveal the classic features of complete left lower lobe atelectasis. On chest radiographs, complete left lower lobe atelectasis appears as a triangular opacity behind the heart. The displaced major fissure is seen as an interface between the opacified atelectatic lobe and the hyperexpanded left upper lobe. Note the presence of several secondary signs of atelectasis in this case, including inferomedial displacement of the left hilum, slight leftward shift of the mediastinum, and compensatory hyperinflation of the left upper lobe.

In an outpatient setting, the presence of lobar collapse is usually indicative of an obstructing central mass. In an adult patient, primary lung cancer and carcinoid are important diagnostic considerations. In a child, an aspirated foreign body is the most likely diagnosis. CT is helpful in identifying the centrally obstructing lesion and for guiding bronchoscopic procedures.

1 What disorder of pulmonary vascularity is evident in this case?

2 What is the difference between primary and secondary pulmonary artery hypertension (PAH)?

3 Is primary PAH more common in men or women?

4 Does a normal chest radiograph exclude the diagnosis of PAH?

Primary Pulmonary Artery Hypertension

2 In secondary PAH, the hypertension has a known cause; in primary PAH, the cause is unknown.

Frazier AA, Galvin JR, Franks TJ, Rosado-de-Christenson, M: From the Archives of the AFIP: Pulmonary vasculature: hypertension and infarction. Radiographics 20:491-524, 2000.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 327-330.

PAH is defined as a condition of sustained elevation of pulmonary artery pressure. PAH may occur secondary to one of three basic mechanisms: (1) increased pulmonary blood flow (e.g., left-to-right shunt), (2) decreased cross-sectional area of the pulmonary vasculature (e.g., chronic pulmonary embolism), and (3) increased resistance to pulmonary venous drainage (e.g., mitral valve disease). Another framework for categorizing causes of PAH is to broadly divide them as either precapillary (changes limited to the arterial pulmonary circulation) or postcapillary (primary abnormalities within the pulmonary venous circulation).

The majority of cases of PAH occur secondary to a known cause. These cases are collectively referred to as secondary PAH. In a minority of cases, the etiology of PAH remains unknown. These cases are referred to as primary PAH. This condition tends to affect women younger than 40 years of age.

Regardless of the type of PAH, the characteristic findings on chest radiographs are similar. There is usually marked enlargement of the main and hilar pulmonary arteries, which rapidly taper as they course distally. The degree of pulmonary artery enlargement varies considerably, and significant PAH can be present in the setting of a normal chest radiograph. CT is more accurate than chest radiography for detecting pulmonary artery enlargement.

1 What is the most likely cause of mediastinal hematoma in this patient?

2 What is the most common complication of central catheter placement?

3 What is the optimal location for a central venous catheter?

4 Name two complications associated with catheter placement in the right atrium.

Mediastinal Hematoma Secondary to Vascular Perforation by a Central Venous Catheter

1 Vascular perforation by central venous catheter.

3 The superior vena cava.

4 Arrhythmia and cardiac perforation.

Kidney DD, Deutsch LS: Misplaced central venous catheters: venous anatomy, clinical significance, and treatment options. Radiologist 5:119-126, 1998.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 140-144.

Published rates of complications of central venous catheter placement vary considerably and are dependent upon both operator experience and anatomic site. The most common complication of central venous catheter placement is malposition, which occurs in up to 40% of cases. Pneumothorax is the second most common complication, occurring in up to 5% of cases. Less common complications include hemothorax, extrapleural hematoma, cardiac arrhythmias, vascular or cardiac perforation, peripheral venous thrombosis, catheter fragmentation, septic emboli, and mycotic aneurysms.

Because of its high flow rate and large volume, the superior vena cava is the ideal location for a central venous catheter. The distal portion of the catheter should lie parallel to the direction of blood flow, and it should not abut the vessel wall.

Catheter malposition is usually evident on a frontal chest radiograph. In some cases, however, a lateral view is necessary to determine the precise location of the catheter tip. In a small minority of cases, a contrast study is necessary to verify catheter location.

In this case, note the unusual medial course of the catheter on the chest radiograph. The CT image confirms an extravascular location.

1 What is the most common cause of bilateral, symmetric hilar lymph node enlargement?

2 What percentage of sarcoid patients with hilar lymphadenopathy also have lung parenchymal disease on chest radiography?

3 What percentage of patients with sarcoidosis are asymptomatic at the initial presentation?

4 Are noncaseating granulomas specific for sarcoidosis?

2 Approximately 50%. May be higher on CT.

3 Approximately 50%.

Miller BH, Rosado-de-Christenson ML, McAdams HP, Fishback NF: Thoracic sarcoidosis: radiologic-pathologic correlation. Radiographics 15:421-437, 1995.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 188-190.

Sarcoidosis is a systemic disorder of unknown etiology that is characterized pathologically by widespread noncaseating granulomas. Because this pathologic finding may also be seen in a variety of other conditions, a diagnosis of sarcoidosis requires consistent radiologic, clinical, laboratory, and pathologic findings, as well as exclusion of other entities (especially granulomatous infections).

The chest radiograph is abnormal in approximately 90% of patients with sarcoidosis. Bilateral, symmetric hilar lymph node enlargement is the most common radiographic abnormality and is frequently accompanied by mediastinal lymph node enlargement. Lung parenchymal disease is usually nodular or reticulonodular in appearance, with a predilection for the upper and mid-lung zones.

On CT examination (particularly HRCT), sarcoid granulomas typically appear as small (1- to 2-mm-diameter) nodules, with a characteristic perilymphatic distribution. This distribution includes the peribronchovascular lymphatics, the interlobular septa, and the subpleural lymphatics (peripherally and along the fissures). Approximately 20% of patients with radiographic evidence of interstitial lung disease develop interstitial fibrosis.

1 What is the most likely cause of parenchymal opacification in this patient who recently sustained a gunshot injury to the right hemithorax?

2 Is contusion an early or late sign of thoracic trauma?

3 When would you expect a contusion to resolve?

4 What other parenchymal injury is evident on the second radiograph of this patient?

Pulmonary Contusion and Laceration

1 Pulmonary contusion.

2 Early (within 6 hours).

3 Within 7 days.

4 Pulmonary laceration.

Kaewlai R, Avery LL, Asrani AV, Novellline RA: Multidetector CT of blunt thoracic trauma. Radiographics 28:1555-1570, 2008.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 168-169.

Thoracic trauma may result in two forms of lung parenchymal injury: pulmonary contusion and pulmonary laceration. Pulmonary contusion is the most common form of lung injury and represents hemorrhage into the alveoli. On radiographs, pulmonary contusion appears as areas of airspace opacification that are usually in close proximity to the site of blunt trauma, but may also less commonly be observed in the opposite portion of the lung (contrecoup lesion). Thus, the identification of consolidation adjacent to sites of rib fractures or bullet fragments should suggest the diagnosis. The consolidation from contusion typically appears on radiographs within 6 hours of the time of injury, and it usually improves within 24 to 72 hours. The consolidation usually completely resolves within 1 week of onset.

CT may detect pulmonary contusion immediately after injury, before abnormalities are visible radiographically. On CT, areas of contusion may sometimes demonstrate characteristic subpleural sparing of the peripheral 1 to 2 mm of the lungs.

Pulmonary laceration refers to a tear in the lung parenchyma. Such injuries may initially be masked by surrounding contusion. On radiographs of patients with pulmonary laceration injury, you may observe an ovoid cystic lucency that represents a posttraumatic pneumatocele. Such cysts are typically small (5 mm to 1 cm), but larger cysts can be seen in some cases. If the cyst fills with blood, a spherical hematoma is observed. In some cases, the cyst contains air and blood, with a resultant air-fluid level.

1 Name the location of the intrathoracic, extraalveolar air collection that is evident on the radiograph and CT image.

2 Is there another intrathoracic, extraalveolar air collection evident on the radiograph?

3 What is the most common mechanism for the development of pneumomediastinum?

4 Would you expect pneumomediastinum to change in configuration on a decubitus radiograph?

Pneumomediastinum

1 Pneumomediastinum.

2 Yes—small apical pneumothoraces.

3 Alveolar rupture.

Bejvan SM, Godwin JD: Pneumomediastinum: old signs and new signs. AJR Am J Roentgenol 166:1041-1048, 1996.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, p 165.

There are a variety of causes of pneumomediastinum. Intrathoracic sources include ruptured alveoli, tracheal perforation, and esophageal rupture. Air may also enter the mediastinum from the neck or retroperitoneum.

Alveolar rupture is the most common mechanism of pneumomediastinum and may occur secondary to elevated intraalveolar pressure or damage to alveolar walls. Causes of elevated intraalveolar pressure include airway obstruction (e.g., asthma, foreign body), mechanical ventilation, blunt thoracic trauma (the cause in this case), coughing, Valsalva maneuver, and vomiting. Disorders associated with alveolar wall damage include pneumonia, adult respiratory distress syndrome, emphysema, and interstitial fibrosis.

On radiographs of patients with pneumomediastinum, you will observe lucent streaks of air that surround the mediastinal structures, elevate the mediastinal pleura, and frequently extend into the soft tissues of the neck. In most cases, pneumomediastinum is readily distinguishable from pneumothorax and pneumopericardium. However, when only a small amount of gas is localized adjacent to the heart border, it may be difficult to distinguish these entities. In such cases, a lateral decubitus view may be helpful: unlike pneumothorax and pneumopericardium, pneumomediastinum will not shift in position.

1 Name four features that are typical of malignant pleural thickening.

2 Which is more common: pleural metastases or malignant mesothelioma?

3 How frequently are pleural calcifications observed on CT scans of patients with malignant mesothelioma?

4 What is the typical latency period between exposure to asbestos and development of malignant mesothelioma?

Malignant Mesothelioma

1 Greater than 1 cm in thickness, nodularity, circumferential growth pattern within the involved hemithorax, and involvement of the mediastinal pleural.

2 Pleural metastases.

3 Approximately 20%.

4 Between 30 and 40 years.

Miller BH, Rosado-de-Christenson ML, Mason AC, et al: Malignant pleural mesothelioma: radiologic-pathologic correlation. Radiographics 16:613-644, 1996.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 392-395.

Malignant mesothelioma is the most common primary neoplasm of the pleura, but it is a relatively rare entity. In approximately 80% of cases, it affects individuals who have been exposed to asbestos. Males are affected more commonly than females. Presenting symptoms include chest pain and dyspnea.

The most common radiographic finding is the presence of diffuse pleural thickening that is typically nodular and irregular in configuration. Diffuse pleural thickening may be accompanied by a reduction in the size of the affected hemithorax, with associated ipsilateral shift of the mediastinum. Pleural effusion is often present.

CT and MR are superior to radiography in assessing the extent of disease. In many cases, CT and MR play complementary roles in determining resectability and may be used to assess transdiaphragmatic extension, diffuse chest wall invasion, invasion of vital mediastinal structures, vertebral body invasion, direct extension of tumor to the contralateral pleura, and the presence of distant metastases. The presence of one or more of these findings precludes surgical resection.

Patients with limited disease may be considered candidates for attempted surgical cure by extrapleural pneumonectomy. Regardless of therapy, however, malignant mesothelioma is almost always fatal.

1 Where is the pleural effusion located in the first figure?

2 What is the most sensitive radiographic projection for detecting a pleural effusion?

3 How much pleural fluid must be present in order to observe blunting of the costophrenic angle on the frontal chest radiograph?

4 Name the two most common causes of an exudative pleural effusion.

Subpulmonic Pleural Effusion

1 Subpulmonic space.

2 Lateral decubitus view.

3 At least 200 ml.

4 Infection and neoplasm.

Stark P: Imaging of pleural effusions in adult. In: Rose BD, Ed. UpToDate. Waltham, MA: UpToDate, 2007.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 166-167, 382.

On an upright chest radiograph, a pleural effusion is usually manifested by the presence of a meniscus sign, which refers to a blunted appearance of the costophrenic angle, with a concave upward slope. In general, it requires approximately 200 ml of fluid to blunt the lateral costophrenic angle but only approximately 75 ml of fluid to blunt the posterior costophrenic angle. A lateral decubitus view can demonstrate as little as 5 ml of fluid.

In some patients, a large amount of free-flowing pleural fluid may collect in the subpulmonic space before spilling into the costophrenic angle. In such cases, you may observe a characteristic appearance on the frontal chest radiograph, including an apparent elevation of the hemidiaphragm, flattening of the diaphragm contour medially, and displacement of the peak of the diaphragm laterally. A suspected subpulmonic effusion can be confirmed by obtaining a lateral decubitus radiograph (second figure).

On the basis of laboratory evaluation, pleural effusions can be classified as exudates or transudates. Causes of exudates include infection, infarction, neoplasm, and inflammatory disorders. Causes of transudates include congestive heart failure, low protein level, myxedema, cirrhosis, nephrotic syndrome, and constrictive pericarditis.

1 What abnormal extraalveolar intrathoracic air collection is evident on this supine chest radiograph?

2 What are the two most common locations of a pneumothorax on a supine radiograph?

3 On a supine radiograph, is an apicolateral visceral pleural line a highly sensitive sign for the diagnosis of pneumothorax?

4 Name at least three radiographic findings associated with a subpulmonic pneumothorax on a supine radiograph.

Pneumothorax on Supine Radiograph

1 Pneumothorax.

2 Anteromedial and subpulmonic.

4 Hyperlucent upper abdominal quadrant, deep sulcus sign, sharp diaphragmatic contour, and double diaphragm sign (this sign refers to visualization of the anterior and posterior surfaces of the diaphragm).

Hill JR, Norner PE, Primack SL: ICU imaging. Clin Chest Med 29:59-76, 2008.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 388-389.

A pneumothorax is usually readily identifiable on an upright chest radiograph as an apicolateral white line (the visceral pleural line) with an absence of vessels beyond it. However, in the supine position, the apicolateral portion of the lung is no longer the most nondependent portion. Rather, air collects preferentially in the anteromedial and subpulmonic portions of the chest. Only when a large volume of air is present in the pleural space will you visualize an apicolateral pleural line on a supine radiograph. Thus, although highly specific for pneumothorax, this is not a highly sensitive sign on supine radiographs.

The chest radiograph in this case shows several signs associated with a subpulmonic pneumothorax, including a hyperlucent appearance of the right upper quadrant of the abdomen, a deep costophrenic sulcus, and a sharp right hemidiaphragm contour. Also note the sharp outline of the right cardiac and mediastinal contours, findings associated with anteromedial pneumothorax.

1 Where are these masses located?

2 Which feature is most helpful for differentiating a pleural mass from an extrapleural (chest wall) mass?

3 What are the two most common causes of an extrapleural mass with associated rib destruction in an adult patient?

4 Name two causes of hypervascular chest wall metastases.

Extrapleural Masses Secondary to Metastatic Thyroid Carcinoma

1 Extrapleural (chest wall).

2 The presence of rib abnormalities such as destruction or remodeling suggests an extrapleural location.

3 Metastatic disease and myeloma.

4 Thyroid carcinoma and renal cell carcinoma.

Reed JC: Chest wall lesions. In: Chest Radiology: Plain Film Patterns and Differential Diagnoses, fifth edition. Philadelphia, Mosby, 2003, pp 6-24.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 40-41.

The chest radiograph shows multiple masses that form obtuse angles with the adjacent chest wall and have incomplete, tapered borders. Such an appearance is typical of an intrathoracic, extrapulmonary location. The identification of rib destruction (best seen on the CT image) confirms that the masses are extrapleural.

In an adult patient, the most common causes of chest wall masses with associated rib destruction are metastatic disease and multiple myeloma. The contrast-enhanced CT image shows intense enhancement of the mass, a finding that is associated with hypervascular metastases. The most common causes for such findings are metastatic thyroid carcinoma and renal cell carcinoma.

1 What is the location of the confluent opacity in the right hemithorax?

2 What feature of this opacity on the PA projection suggests an extraparenchymal location?

3 What features of this opacity suggest a pleural location on the lateral projection?

4 What is the term used to describe a masslike opacity due to loculated pleural fluid within a fissure?

Loculated Pleural Fluid in the Major Fissure

1 Pleura (the major fissure).

2 Incomplete borders (note the sharp margins inferomedially and the lack of a distinct margin superolaterally).

3 Elliptical configuration and an oblique orientation corresponding to the course of the major fissure.

4 Vanishing tumor, phantom tumor, or pseudotumor.

Reed JC: Pleural and subpleural opacities. In: Chest Radiology: Plain Film Patterns and Differential Diagnoses, fifth edition. Philadelphia, Mosby, 2003, pp 25-46.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 381, 382.

The chest radiograph in this case demonstrates the characteristic appearance of a loculated pleural fluid collection within the major fissure. Such loculation occurs most commonly in patients with heart failure. Loculated fluid is seen more often in the right lung than in the left, and the minor fissure is more commonly involved than the major fissure. Because of the transient nature of loculated fluid collections, they have been referred to as “vanishing tumors,” “phantom tumors,” and “pseudotumors.” Such terms should be avoided in radiology reports to avoid possible confusion.

When fluid is loculated within the major fissure, it may appear on the PA projection as either a discrete, masslike opacity with incomplete borders (as demonstrated in the first figure) or as a hazy, veil-like opacity. On the lateral radiograph, such a loculated fluid collection appears as a well-marginated, elliptical opacity coursing along the obliquely oriented axis of the major fissure (as demonstrated in the second figure). The rapid onset and resolution of such fluid collections usually allow one to readily distinguish loculated fluid from a solid pleural mass. When the diagnosis is in doubt, a decubitus view may be helpful, because it will demonstrate the free fluid to shift in distribution. CT can readily differentiate pleural fluid collections from solid masses and may be useful in selected “problem” cases in which there is a lack of shift on decubitus radiographs due to loculation.

1 Name the mediastinal line that is indicated by the arrow labeled 2.

2 How many layers of pleura form this line?

3 Which line extends above the level of the clavicles—the anterior or the posterior junction line?

4 Which line is visualized more frequently—the anterior or the posterior junction line?

1 Anterior junction line.

3 Posterior junction line (arrow labeled 1).

4 Anterior junction line.

Müller NL, Silva CIS: Normal chest radiograph. In: Silva CIS, Müller NL, Eds. Imaging of the Chest. Philadelphia, Saunders, 2008, pp 3-33.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 339, 341.

The coned-down frontal radiograph demonstrates the normal appearance of the anterior junction line (arrow labeled 2) that is formed by the close apposition of the visceral and parietal layers of pleura of both lungs as they approximate anterior to the mediastinum. Similarly, the posterior junction line (arrow labeled 1) represents the apposition of pleural layers of both lungs as they approximate posterior to the mediastinum.

The anterior portion of the thorax begins at the thoracic inlet. Thus, the anterior junction line begins at the undersurface of the clavicles. It typically courses obliquely from right to left, as demonstrated in this case. The posterior portion of the thorax extends more superiorly than the anterior portion. Thus, the posterior junction line may be seen above the level of the clavicles, as in this illustration. It typically appears as a straight vertical line, often visible through the tracheal air column.

The identification of a displaced or obliterated junction line can help to identify and localize a mediastinal mass. Displacement of a junction line is also an indicator of volume loss and may accompany atelectasis of a lobe or of an entire lung.

1 What is the most likely cause of the thickened tracheoesophageal stripe observed on the lateral chest radiograph?

2 What are the major risk factors for developing esophageal carcinoma?

3 What are the two most common cell types of esophageal neoplasm?

4 What is the most common benign esophageal neoplasm?

Esophageal Carcinoma

1 Esophageal carcinoma.

2 Cigarette smoking and alcohol ingestion (additional risk factors include achalasia, preexisting benign stricture, Barrett’s esophagus, tylosis, Plummer-Vinson syndrome, and sprue).

3 Squamous cell carcinoma and adenocarcinoma together account for more than 90% of esophageal cancers.

Kim TJ, Kim HY, Lee KW, Kim MS: Multimodality assessment of esophageal cancer: preoperative staging and monitoring of response to therapy. Radiographics 29:403-421, 2009.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 364-366.

The lateral chest radiograph demonstrates abnormal thickening of the tracheoesophageal stripe and anterior displacement of the trachea. A tracheoesophageal stripe that measures more than 5 mm in width should be considered abnormal and usually signifies the presence of esophageal carcinoma. The CT image confirms the presence of esophageal wall thickening. Images below this level (not shown) demonstrated an obstructing esophageal neoplasm.

In patients with esophageal carcinoma, CT can be helpful for assessing the extent of the primary esophageal lesion, identifying nodal spread, and determining extension of the neoplasm beyond the esophagus. CT is often used in conjunction with endoscopic ultrasound and PET for staging purposes.

Although squamous cell carcinoma once represented greater than 90% of all esophageal neoplasms in the United States, there has been a dramatic increase in the incidence of adenocarcinoma. Adenocarcinoma and squamous cell carcinoma now occur with a similar frequency.

1 Measurements of this nodule show no change in size during the interval between these two radiographs. Is this nodule benign, indeterminate, or malignant?

2 Name at least three benign calcification patterns.

3 Name at least one calcification pattern that is not considered benign.

4 Are follow-up radiographs or CT necessary to further evaluate this nodule?

Benign Calcified Granuloma

2 Diffuse, central, popcorn, and laminar (concentric).

3 Eccentric; stippled.

Erasmus JJ, Connoly JE, McAdams HP, Roggli VL: Solitary pulmonary nodules: part I. Morphologic evaluation for differentiation of benign and malignant lesions. Radiographics 20:43-58, 2000.

Erasmus JJ, McAdams HP, Connoly JE: Solitary pulmonary nodules: part II. Evaluation of the indeterminate nodule. Radiographics 20:59-66, 2000.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 284-286.

The chest radiographs demonstrate stability in size of a small right lower lobe nodule over an 8-year period. Note the presence of laminar calcification, a recognized benign pattern.

There are two accepted radiographic criteria for a benign solitary pulmonary nodule: (1) lack of interval growth for at least 2 years and (2) identification of a benign calcification pattern within a smoothly marginated pulmonary nodule.

Approximately half of all resected solitary pulmonary nodules prove to be benign. Clinical indicators that suggest a benign diagnosis include age younger than 35 years and history of exposure to tuberculosis or residence in an endemic granuloma area. Such indicators are, unfortunately, insufficiently specific to be helpful in most individual cases.

For patients with nodules that do not meet the accepted radiographic criteria for benignancy, noncontrast CT with thin-section imaging is usually the preferred method for further evaluation. CT is more sensitive than conventional radiographs for detecting calcium and fat within a nodule. In certain cases, CT imaging allows a confident diagnosis of a specific benign entity such as granuloma, hamartoma, arteriovenous malformation, pulmonary infarction, mucoid impaction, and pulmonary sequestration.

When CT is nondiagnostic, the method of further evaluation depends on patient characteristics and nodule morphology. Noninvasive imaging modalities include contrast-enhanced CT to assess for abnormal nodule enhancement and 2-[fluorine-18] fluoro-2-deoxy-D-glucose (FDG) PET imaging, which relies on abnormal glucose analogue (FDG) uptake to distinguish benign from malignant nodules.

1 CT density measurements of this nodule revealed areas of low attenuation, measuring approximately −52 Hounsfield units. What type of tissue is associated with this Hounsfield measurement?

2 What is the diagnosis for this solitary pulmonary nodule?

3 Is this a benign or a malignant entity?

4 Are hamartomas always stable in size over time?

Erasmus JJ, Connolly JE, McAdams HP, Roggli VL: Solitary pulmonary nodules: Part I. Morphologic evaluation for differentiation of benign and malignant lesions. Radiographics 20:43-58, 2000.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 253, 254.

The thin-section CT images demonstrate a well-circumscribed, spherical, solitary pulmonary nodule in the right upper lobe. The nodule contains several low-attenuation areas, which represent focal deposits of fat. The identification of fat deposits (−50 to −150 Hounsfield units) within a pulmonary nodule is diagnostic of a hamartoma, the most common benign pulmonary neoplasm.

A hamartoma is an acquired lesion that represents a disorganized growth of tissue normally found within the lung. Pathologically, the tumors contain cartilage, fibrous tissue, and mature fat cells. Other mesenchymal elements such as bone, vessels, and smooth muscle may also be present.

Affected patients range in age from 30 to 70 years, with a peak incidence observed in the sixth decade of life. There is a slight female predominance. The majority of lesions are detected incidentally on routine chest radiographs of asymptomatic patients. An exception is the presence of an endobronchial hamartoma, which may present with symptoms of airway obstruction.

On imaging studies, hamartomas typically appear as well-defined, solitary, spherical nodules or masses. A characteristic “popcorn” pattern of calcification is identified in approximately 10% to 15% of cases on conventional radiographs and in approximately 25% of cases on CT imaging. Hamartomas typically grow slowly and may rarely be multiple.

Thin-section CT evaluation is more accurate than conventional radiography for diagnosing hamartoma. In the majority of cases, CT will demonstrate one of the following patterns: foci of fat attenuation; a combination of fat and calcification; or lobular (“popcorn”) calcification.

1 Name the pattern of lung opacification observed in the left lower lobe of this patient.

2 What is the term used to describe the air-filled, tubular, branching structures that are visible within the left lower lobe?

3 Name at least three substances that may fill the alveolar spaces and produce airspace opacity.

4 Name the organism that is most frequently associated with lobar pneumonia in the normal (non-immunosuppressed) host.

Left Lower Lobe Pneumonia

1 Alveolar consolidation.

2 Air bronchograms.

3 Water (edema), pus (pneumonia), blood (hemorrhage), cells (bronchioalveolar cell carcinoma), and protein (alveolar proteinosis).

4 Streptococcus pneumoniae.

Gharib AM, Stern EJ: Radiology of pneumonia. Med Clin North Am 85:1461-1491, 2001.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 27-28, 80-82.

The chest radiograph demonstrates the presence of confluent opacification in the left lower lobe with prominent air bronchograms, consistent with alveolar consolidation. This pattern may be caused by the accumulation of edema, pus, hemorrhage, cells, or protein within the alveolar spaces.

Once a pattern of alveolar consolidation has been identified, it is important to determine the distribution and chronicity of the process and correlate the imaging findings with the clinical presentation of the patient.

The distribution of alveolar consolidation is often quite helpful in narrowing the differential diagnosis. For example, the presence of a bilateral, perihilar distribution of alveolar consolidation is most suggestive of hydrostatic pulmonary edema. In contrast, this case demonstrates a striking lobar distribution of consolidation, a pattern that is most commonly associated with pneumonia. The most common organism to produce a lobar pneumonia is S. pneumoniae. Other organisms such as Klebsiella pneumoniae, Legionella pneumophila, and Mycoplasma pneumoniae may also produce a lobar consolidation pattern.

With regard to the chronicity of a consolidative pattern, this factor is best determined by comparing the current study with prior chest radiographs. The presence of chronic airspace disease or consolidation is associated with a limited differential diagnosis that includes bronchioloalveolar carcinoma (BAC), alveolar proteinosis, lipoid pneumonia, lymphoma, and the “alveolar” form of sarcoid.

1 In this patient with a history of Hodgkin’s lymphoma, what is the most likely etiology of the paramediastinal lung parenchymal opacification?

2 Is this a common finding in patients who have received mantle radiation therapy for lymphoma?

3 At what time point following completion of radiation therapy is radiation pneumonitis usually detectable by chest radiography?

4 Name the term that is used to describe the presence of dilated bronchi within areas of fibrosis.

Radiation Pneumonitis

1 Radiation pneumonitis.

3 Approximately 6 to 8 weeks.

4 Traction bronchiectasis.

Choi YW, Munden RF, Erasmus JJ, et al: Effects of radiation therapy on the lung: radiologic appearances and differential diagnosis. Radiographics 24:985-997, 2004.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 277-278, 280.

The chest radiograph demonstrates a bilateral, paramediastinal distribution of parenchymal opacification with associated air bronchograms. The geographic margins and geometric shape correspond to the field of irradiation.

Radiation pneumonitis and fibrosis are observed in the majority of patients who have received mantle radiation therapy for lymphoma. Radiation pneumonitis is generally observed on chest radiographs within 6 to 8 weeks following completion of treatment, but CT may detect subtle abnormalities earlier than radiography (within a few weeks after completion of treatment). Such opacities are characteristically sharply demarcated and are not limited by anatomic boundaries such as fissures. Fibrosis usually develops within 6 to 12 months following radiation therapy. With time, the parenchymal opacities generally become more linear in configuration and are usually accompanied by volume loss and traction bronchiectasis.

Several methods have been developed to deliver an adequate dose of radiation to tumors while limiting the amount of exposure to normal lung parenchyma. These techniques include limited radiation portals, tangential beams, conformed therapy, and intensity-modulated radiation therapy. These methods may result in variable patterns of radiation-induced lung injury. Knowledge of the temporal relationship and type of therapy can help to distinguish radiation changes from infection and malignancy.

1 Define the acute respiratory distress syndrome (ARDS).

2 Name at least three common causes.

3 What sign of barotrauma is evident in this patient?

4 What is the distribution of this abnormal, extraalveolar air collection?

Acute Respiratory Distress Syndrome Complicated by Left Anteromedial Pneumothorax From Barotrauma

1 ARDS is a clinical diagnosis of acute respiratory failure characterized by profound hypoxia accompanied by diffuse parenchymal opacification on chest radiography.

2 Sepsis, trauma, severe pneumonia, circulatory shock, aspiration, inhaled toxins, drug overdose, near drowning, and multiple blood transfusions.

3 Pneumothorax.

4 Anteromedial.

Hansen-Flaschen J, Sietel MD: Acute respiratory distress syndrome: definition; epidemiology; diagnosis; and etiology. In: Rose BD, Ed. UpToDate, Waltham, MA, UpToDate, 2008.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 154-155.

The chest radiograph of a patient who attempted suicide by drug overdose reveals diffuse bilateral lung opacification with prominent air bronchograms. Allowing for portable, supine technique, the heart does not appear enlarged. Note the prominent lucency along the left mediastinal contour, corresponding to an anteromedial left pneumothorax.

ARDS is a severe form of acute lung injury that is thought to encompass a variety of distinct disorders that share common pathophysiologic and clinical features. It may be precipitated by a variety of pulmonary and extrapulmonary conditions, including drug overdose (the cause in this patient).

Because of decreased lung compliance and the need for prolonged mechanical ventilation, patients with ARDS frequently develop barotrauma, including subcutaneous emphysema, pneumothorax, pneumomediastinum, and pulmonary interstitial emphysema.

1 Name two radiographic signs of bronchiectasis that are present in this case.

2 What is the most likely cause of bronchiectasis that is most severe in the upper lobes?

3 How is this condition inherited?

4 Does this condition ever initially present in adulthood?

Cystic Fibrosis

1 Bronchial wall thickening forming parallel linear opacities (“tram-tracking”) and ring shadows.

2 Cystic fibrosis (CF).

3 Autosomal recessive.

4 Yes—occasionally mild forms of CF are first diagnosed in adult patients.

Webb WR: Radiology of obstructive lung disease. AJR Am J Roentgenol 169:637-647, 1997.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 318-319.

The chest radiograph and coned-down view in this case demonstrate bronchiectasis, manifested by bronchial wall thickening (tram-tracking) and ring shadows (arrow, first figure). Although the distribution is diffuse, the lung bases are least involved. The findings are typical of CF, a hereditary disorder characterized by abnormal secretions from exocrine glands, including the airways, pancreas, large bowel, and salivary and sweat glands. The major clinical manifestations of this disorder are chronic pulmonary disease due to bronchiectasis and pancreatic insufficiency.

Although CF is usually diagnosed during infancy or childhood, milder forms of the disease are occasionally first diagnosed in adults. Affected patients are at increased risk for pulmonary infections with a variety of organisms, including Staphylococcus aureus, Pseudomonas aeruginosa, Haemophilus influenzae, and Pseudomonas cepacia. The last organism is a major cause of infection late in the course of CF. Presenting symptoms of CF are related to recurrent pulmonary infections and include productive cough, wheezing, dyspnea, and hemoptysis. The diagnosis of CF may be confirmed by an abnormal sweat test or molecular biologic testing (polymerase chain reaction).

Classic chest radiographic findings include bronchial wall thickening, saccular spaces due to dilated airways, hyperinflation, and mucoid impaction. Recurrent foci of consolidation and atelectasis are commonly observed. Hilar enlargement is frequently seen in affected adults and may occur secondary to hilar lymph node enlargement or PAH.

1 Can you reliably distinguish between an infectious and a neoplastic etiology of a cavity based on imaging features alone?

2 Based on the location of this cavity, what is the most important infectious consideration?

3 In addition to infectious and neoplastic causes, what other categories of abnormalities should you consider when a patient presents with one or more cavities?

4 Which cell type of lung cancer is most closely associated with the presence of cavitation?

Cavity Due to Post-primary Tuberculosis

2 Post-primary TB.

3 Vasculitis and granulomatoses.

4 Squamous cell carcinoma.

Reed JC: Solitary localized lucent defect. In: Chest Radiology: Plain Film Patterns and Differential Diagnoses, fifth edition. Philadelphia, Mosby–Year Book, 2003, pp 406-426.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 102-104.

The term cavity refers to a lucency located within a nodule, mass, or focus of consolidation. There are a variety of causes, including infection (pyogenic and granulomatous), neoplasm (usually squamous cell), vasculitides and granulomatoses, and rarely, infarction. The most common causes of a solitary cavity are infections and neoplasms.

Certain features can help you determine the likely cause of a cavity, but they are not specific enough to allow you to make a definitive diagnosis in most cases. Features to consider include wall thickness, presence or absence of a fluid level, location, and presence of adjacent lung parenchymal abnormalities. With regard to wall thickness, very thin-walled (<4-mm-diameter) cavities are often benign. In contrast, neoplasms typically demonstrate very thick walls. There is considerable overlap in this feature, however, and it should not be used as a sole criterion. With regard to the presence of a fluid level, it is most often associated with benign nodules; however, fluid levels may occasionally be observed in cavitary neoplasms that have been complicated by secondary infection or hemorrhage. Regarding the location of a cavity, hematogenous cavities often have a lower lobe predominance, reflecting the gravitational distribution of blood flow. Cavities associated with post-primary TB are most commonly located in the apical and posterior segments of the upper lobes and the superior segments of the lower lobes. Primary lung cancer is most common in the upper lobes, but any lobe may be affected. Regarding the presence of adjacent lung abnormalities, the development of a cavity within a preexisting area of consolidation is typical of a lung abscess.

1 What is the most likely cause for this intracavitary mass?

2 What pleural abnormality frequently accompanies the development of this abnormality?

3 What is the usual treatment for asymptomatic individuals with this finding?

4 Name at least two therapeutic options for patients who develop hemoptysis from this process.

2 Pleural thickening.

4 Bronchial artery embolization and surgical resection are the most common therapeutic options. Other reported treatments include direct instillation of amphotericin B via a percutaneous catheter into the cavity and systemic antifungal therapy (usually as adjunctive therapy in combination with surgery).

Franquet T, Müller NL, Giménez A, et al: Spectrum of pulmonary aspergillosis: histologic, clinical, and radiologic findings. Radiographics 21:825-837, 2001.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 113-114.

The chest radiograph and chest CT images demonstrate the presence of an intracavitary left upper lobe mass and apical pleural thickening. The imaging findings are characteristic of an aspergilloma, the most common radiographic form of aspergillosis.

Aspergilloma (also called mycetoma) refers to a saprophytic infection that occurs within a preexisting cyst, cavity, bulla, or area of bronchiectasis. Pathologically, the fungus ball is shown to represent a combination of Aspergillus hyphae, mucus, and cellular debris.

Patients at risk for aspergilloma formation include those with CF, sarcoidosis, TB, and emphysema. The infection is typically clinically silent for many years. Presenting symptoms may include cough, weight loss, and recurrent hemoptysis. Although hemoptysis is usually minimal, a minority of patients may present with massive, life-threatening hemoptysis. Severe hemoptysis requires therapeutic intervention such as bronchial artery embolization.

Characteristic imaging findings include a round, dependent opacity located within a cavity or thin-walled cyst. The dependent opacity is often heterogeneous due to the presence of multiple linear collections of air, resulting in a “spongelike” appearance. It occurs most commonly in the upper lobes and is frequently accompanied by pleural thickening. In a majority of cases, the fungus ball demonstrates mobility on changes in patient positioning. An aspergilloma is often surrounded by a crescent of air, referred to as the monad sign. In a minority of cases, however, the fungus ball may completely fill the cavity, with no visible air between the cavity and the ball.

1 Name at least four possible causes for a right cardiophrenic angle mass.

2 Which one of these entities is the diagnosis in this case?

3 Are pericardial cysts more common on the right or the left side?

4 Do pericardial cysts usually communicate with the pericardium?

Pericardial Cyst

1 Pericardial fat pad, pericardial cyst, Morgagni’s foramen hernia, lipoma, thymolipoma, and enlarged epicardial lymph nodes.

2 Pericardial cyst.

Fujimoto K, Müller NL: Anterior mediastinal masses. In: Müller NL, Silva CI, Eds. Imaging of the Chest. Philadelphia, Saunders, 2008, p 1517.

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Thoracic Radiology: THE REQUISITES, 2nd ed, p 361.

The chest radiograph demonstrates a well-marginated right cardiophrenic angle mass. The majority of causes of a right cardiophrenic angle mass are benign, as listed in Answer 1.

Although the various causes of a right cardiophrenic angle mass may appear similar radiographically, the CT appearances differ depending on the contents of the lesion. The presence of fluid attenuation within a cardiophrenic angle mass is consistent with a pericardial cyst, the diagnosis in this case. Such cysts are attached to the parietal pericardium, but they do not usually communicate with the pericardial space.

The presence of fat attenuation within a cardiophrenic angle mass can be seen in lipoma, thymolipoma, and Morgagni’s foramen hernia. Lipomas usually demonstrate homogeneous fat attenuation. Thymolipomas, on the other hand, contain a variable mixture of fat and soft tissue elements. Herniated omental fat can be distinguished by the identification of omental vessels, which appear as serpiginous, tubular soft tissue densities. In many cases, herniated omental fat is also accompanied by bowel and/or liver. Occasionally, herniated bowel is visible radiographically, allowing you to make a specific diagnosis of this entity.

A soft tissue attenuation cardiophrenic angle mass is suggestive of enlarged epicardial lymph nodes. Such nodes are a common site of recurrence in patients with Hodgkin’s disease.

1 In which segment of the lung is the consolidation located?

2 What numbered bronchopulmonary segments does this correspond to?

3 Name the order of left lower lobe basilar segmental bronchi from lateral to medial on a frontal radiograph.

4 What is the order on the right side?

Pneumonia of the Anteromedial Basal Segment of the Left Lower Lobe

1 Anteromedial segment of the left lower lobe.

2 Segments 7 and 8.

3 Anteromedial, lateral, and posterior (ALP).

4 Anterior, lateral, posterior, and medial.

Müller NL, Silva CI: Normal chest radiograph. In: Müller NL, Silva CI, Eds. Imaging of the Chest. Philadelphia, Saunders, 2008, pp 13-15.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 80-82.

The frontal radiograph in the first figure demonstrates a subtle focus of parenchymal opacification in the left lower lobe laterally. The focal consolidation is seen in better detail on the lateral radiograph, where it is sharply marginated anteriorly by the major fissure. This location corresponds anatomically to the anteromedial segment of the left lower lobe.

Note the characteristic lateral location of the anteromedial segment on the frontal chest radiograph. The order of the left lower lobe basilar segments on the frontal radiograph (from lateral to medial) is anteromedial, lateral, and posterior (ALP). In the right lower lobe, the order of the basilar segments (from lateral to medial) is anterior, lateral, posterior, and medial.

1 This patient received a course of antibiotics during the 1-month interval between these two radiographs (the first figure preceded the second). What is the likely diagnosis?

2 What organism is most closely associated with a round pneumonia?

3 Are round pneumonias more common in adult or pediatric patients?

4 Based only on the findings in the first figure, what is the most important differential diagnosis to consider?

Round Pneumonia

1 Round pneumonia.

2 S. pneumoniae.

4 Bronchogenic carcinoma.

Wagner AL, Szabunio M, Hazlett KS, Wagner SG: Radiologic manifestations of round pneumonia in adults. AJR Am J Roentgenol 170:723-726, 1998.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 82, 83.

Pneumonia may occasionally manifest as a rounded, masslike opacity with either smooth or irregular margins. Round pneumonia is seen much more frequently in children than adults and is most commonly associated with pneumococcal pneumonia. Round pneumonia has also been associated with a variety of other organisms, including K. pneumoniae, H. influenzae, and Mycobacteriumn tuberculosis, among others. Round pneumonia has also been described as a manifestation of severe acute respiratory syndrome (SARS) coronavirus infection.

When an adult patient presents with a rounded, masslike opacity, bronchogenic carcinoma is the most important diagnosis to consider. Because neoplasms (especially bronchoalveolar cell carcinoma and lymphoma) may occasionally be associated with air bronchograms, the presence or absence of this finding is not helpful in distinguishing infection from neoplasm. Moreover, only a minority of cases of round pneumonia demonstrate air bronchograms radiographically.

A recent chest radiograph with normal findings and a history of infectious symptoms can aid in the diagnosis of round pneumonia. In adult patients with a suspected diagnosis of round pneumonia, follow-up radiographs following appropriate antibiotic therapy are mandatory. Failure of a rounded opacity to completely resolve following antibiotic therapy generally warrants further evaluation with invasive procedures to exclude neoplasm.

1 Name two features of this mass that are suggestive of a mediastinal location.

2 What osseous abnormality is associated with this mass?

3 Does this osseous finding imply a malignant etiology?

4 What is the most common cause of a posterior mediastinal mass?

Neurogenic Tumor (Ganglioneuroma)

1 Smooth, sharp margins and obtuse angle with the adjacent lung.

2 Rib spreading (left fourth and fifth posterior ribs).

4 Neurogenic tumor.

Duwe BV, Sterman DH, Musani AI: Tumors of the mediastinum. Chest 128:2893-2909, 2005.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 362, 363.

Neurogenic tumors are the most common cause of a posterior mediastinal mass. Such lesions can be classified into three groups: (1) those arising from peripheral nerves (schwannoma, neurofibroma); (2) those arising from the sympathetic chain (ganglioneuroma, ganglioneuroblastoma, neuroblastoma); and (3) those arising from the paraganglia (pheochromocytoma, chemodectoma). The majority of lesions (approximately 70%) are benign.

Neurogenic tumors typically affect patients during the first four decades of life. Most lesions are detected incidentally in asymptomatic patients. Symptomatic lesions typically produce neurologic symptoms such as radicular pain and neuresthesias. Intravertebral extension may result in symptoms of cord compression.

Interestingly, tumors arising from peripheral nerves, such as schwannoma, tend to differ in shape from those arising from the sympathetic chain, such as ganglioneuroma. The former lesions are generally round and the latter are usually fusiform, with a vertical orientation. Note the fusiform shape and vertical orientation of the mass in this case, which is typical of a ganglioneuroma.

Rib abnormalities such as rib spreading and rib erosion are commonly associated with neurogenic tumors and do not imply malignancy. In contrast, the presence of bone destruction is suspicious for malignancy. Vertebral body abnormalities are commonly present. Such abnormalities are best demonstrated on CT examinations. Tumors arising from peripheral nerves are often associated with widening of the neural foramen. In contrast, those lesions arising from the sympathetic chain more often result in anterolateral vertebral body erosion.

On cross-sectional imaging studies, benign neurogenic tumors are usually homogeneous in appearance and have well-defined margins. Malignant lesions are more likely to appear heterogeneous and to demonstrate irregular margins.

Foci of calcification are present in a minority of cases. Such calcifications are more often identified on CT than on chest radiographs. Note the presence of focal calcification on the chest radiograph in this case. Calcification is more commonly observed in tumors arising from the sympathetic chain than in those arising from the peripheral nerves.

Once you have identified a suspected neurogenic tumor on chest radiographs, MRI is generally the preferred cross-sectional imaging modality for further evaluation because of its superb ability to demonstrate intraspinal extension of tumor or the presence of an associated spinal cord abnormality.

1 Name six causes of total lung atelectasis.

2 In which direction may large pleural effusions shift the mediastinal structures?

3 List three radiographic findings of total lung atelectasis.

4 Name several causes of hemothorax.

1 Endobronchial tumor, mucus plug, malpositioned endotracheal tube, foreign body, post-traumatic injury, tuberculous stenosis.

2 Toward the contralateral hemithorax.

3 Complete or near-complete opacification of a hemithorax, shift of the mediastinum to the affected side, elevation of the ipsilateral hemidiaphragm (not apparent in acute hemothorax), compensatory overinflation of the contralateral lung, enlargement of retrosternal clear space on lateral radiograph.

4 Trauma (blunt or penetrating), iatrogenic (central venous catheter insertion), complication of surgery, anticoagulation therapy, malignant tumor, catamenial hemothorax.

Woodring JG, Reed JC: Radiographic manifestations of lobar atelectasis. J Thorac Imaging 11:109-144, 1996.

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Thoracic Radiology: THE REQUISITES, 2nd ed, pp 37, 380.

Atelectasis of an entire lung may result from mainstem bronchial obstruction of any cause, including central endobronchial tumors, a mucus plug, or the iatrogenic cause of a malpositioned endotracheal tube into the contralateral mainstem bronchus.

Complete atelectasis of either lung typically manifests as complete opacification of the involved hemithorax with mediastinal shift toward the affected lung and compensatory hyperinflation of the contralateral lung. The findings may be misinterpreted as a massive pleural effusion or pneumonia. Central endobronchial tumors that may cause complete lung atelectasis include lung cancer, carcinoid tumors, hamartoma, adenoidcystic carcinoma, mucoepidermoid carcinoma, and metastatic tumors. On frontal chest radiographs, endobronchial tumors may produce the “cut-off” sign with abrupt termination of the air column at the central, proximal margin of the tumor, often manifesting as a sharply defined interface that may be straight or convex in configuration (left image in figure).

Large pleural effusion is another cause of complete opacification of a hemithorax and may be distinguished by shift of the mediastinal structures away from the affected hemithorax and toward the contralateral side. In this case, the patient was receiving anticoagulation therapy and presented with right shoulder pain.

1 Is loculation of a pleural effusion diagnostic of an empyema?

2 List three CT features of empyema.

3 If an air-fluid level within an opacity measures approximately the same on PA and lateral chest radiographs, is the diagnosis more likely to be an empyema or a lung abscess?

4 What is the most likely cause of an air-fluid level within a pleural fluid collection?

2 Lenticular-shaped fluid collection, obtuse margins at interface with pleural surface, split pleura sign on contrast-enhanced CT, compression of adjacent lung parenchyma.

3 Lung abscess.

4 Bronchopleural fistula.

Kuhlman JE, Singha NK: Complex disease of the pleural space: radiographic and CT evaluation. Radiographics 17:63-79, 1997.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 385-386.

Initially, empyema typically manifests as a classic pleural effusion on chest radiography. As empyema progresses from an exudative to a fibrinopurulent phase, it may manifest as a loculated fluid collection that is typically lenticular in shape, with more defined margins than an uncomplicated pleural effusion, and will often compress the adjacent lung parenchyma. The presence of an air-fluid level within the pleural fluid collection suggests the presence of a bronchopleural fistula. As in this case, the air-fluid levels may demonstrate a disparity in their lengths when compared on PA and lateral (orthogonal) radiographs, in contradistinction to air-fluid levels associated with a spherical lung abscess, which are typically more equal in length on orthogonal radiography. CT demonstrates these features to better advantage and may show smooth thickening and enhancement of visceral and parietal pleura surrounding the abnormal fluid collection (“split pleura” sign), a finding suggestive of empyema. Additional CT features of empyema include a lenticular-shaped fluid collection, typically forming obtuse margins at its interface with pleural surface, and compression of adjacent lung parenchyma. CT may also demonstrate increased extrapleural fat between the empyema space and the chest wall, particularly if the empyema is chronic. The fat may be increased in attenuation because of surrounding edema. In immune-compromised individuals, or if left untreated, an empyema may drain into the subcutaneous tissues of the chest wall and produce empyema necessitans.

1 Name the two most common causes of rib notching.

2 Which anatomic structures lie along the undersurface of the ribs?

3 What are the osseous manifestations of neurofibromatosis?

4 What is the most common cause of osseous destruction of a rib?

1 Aortic coarctation, neurofibromatosis.

2 Intercostal artery, vein and nerve.

3 Widened neural foramina, rib erosion (notching), rib spreading, scoliosis, scalloping of posterior aspects of vertebral bodies (dural ectasia).

4 Metastatic disease.

Boone ML, Swenson BE, Felson B: Rib notching: its many causes. Am J Roentgenol Radium Ther Nucl Med 91:1075-1088, 1964.

Cross-Reference

Thoracic Radiology: THE REQUISITES, 2nd ed, pp 362, 363.

The radiographic finding of rib notching refers to focal erosion along the undersurface of one or more ribs. Rib notching was originally thought to be pathognomonic of coarctation of the aorta. However, it is a recognized manifestation of other abnormalities, most of which are related to an artery, vein, or nerve—the major structures found in the intercostal space.

The leading arterial cause of rib notching is coarctation of the aorta with resultant collateral blood flow through dilated intercostal arteries. Other possible arterial causes include entities associated with decreased pulmonary blood supply (i.e., tetralogy of Fallot, pulmonary atresia, Ebstein’s malformation, and unilateral absence of the pulmonary artery). The venous system is implicated in rib notching that may occur as a result of superior vena caval obstruction or arteriovenous malformations of the pulmonary or intercostal circulations.

The second most common cause of rib notching is growth of an intercostal neurogenic tumor, particularly neurofibroma, as in this case. Also note the biapical paraspinal masses and nodular soft tissues opacities associated with several lower ribs bilaterally—characteristic findings in neurofibromatosis. The mediastinum may appear widened by paraspinal neurofibromas that extend from the thoracic inlet to the diaphragms. Many ribs may be affected by neurofibromatosis, simulating the rib notching seen in coarctation. Frank destructive changes in a rib should prompt suspicion for malignancy, typically caused by a metastatic lesion.

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