Glossary of thoracic imaging terms part 1
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This document defines and describes various thoracic imaging terms related to the lungs. It discusses signs seen on imaging for conditions such as atelectasis, including loss of lung volume demonstrated by shifts in mediastinum, fissures, and hila. Specific types of atelectasis are described, such as absorption, relaxation, adhesive, and compression atelectasis. Other terms defined include bulla, cysts, cavities, pneumatocele, honeycombing, and findings related to diseases like pulmonary fibrosis, sarcoidosis, and lymphadenopathy. Diagrams are provided to illustrate imaging appearances of various conditions.
Glossary of thoracic imaging terms part 1
- 3. Thoracic Imaging Terms By Gamal Rabie Agmy , MD , FCCP Professor of Chest Diseases ,Assiut University ERS National Delegate of Egypt
- 4. Air Bronchogram An air bronchogram is a pattern of air-filled (low-attenuation) bronchi on a background of opaque (high-attenuation) airless lung . The sign implies (a) patency of proximal airways and (b) evacuation of alveolar air by means of absorption (atelectasis) or replacement (eg, pneumonia) or a combination of these processes. (c) In rare cases, the displacement of air is the result of marked interstitial expansion (eg, lymphoma) .
- 6. Air Crescent An air crescent is a collection of air in a crescentic shape that separates the wall of a cavity from an inner mass .The air crescent sign is often considered characteristic of either Aspergillus colonization of preexisting cavities or retraction of infarcted lung in angioinvasive aspergillosis .However, the air crescent sign has also been reported in other conditions, including tuberculosis, Wegener granulomatosis, intracavitary hemorrhage, and lung cancer.
- 7. Air Trapping Air trapping is retention of air in the lung distal to an obstruction (usually partial). Air trapping is seen on end-expiration CT scans as parenchymal areas with less than normal increase in attenuation and lack of volume reduction. Comparison between inspiratory and expiratory CT scans can be helpful when air trapping is subtle or diffuse. Differentiation from areas of decreased attenuation resulting from hypoperfusion as a consequence of an occlusive vascular disorder (eg, chronic thromboembolism) may be problematic , but other findings of airways versus vascular disease are usually present.
- 9. Where is the pathology ??????? in the areas with increased density meaning there is ground glass in the areas with decreased density meaning there is air trapping
- 10. Pathology in black areas Airtrapping: Airway Disease Bronchiolitis obliterans (constrictive bronchiolitis) idiopathic, connective tissue diseases, drug reaction, after transplantation, after infection Hypersensitivity pneumonitis granulomatous inflammation of bronchiolar wall Sarcoidosis granulomatous inflammation of bronchiolar wall Asthma / Bronchiectasis / Airway diseases
- 11. Airway Disease what you see…… In inspiration sharply demarcated areas of seemingly increased density (normal) and decreased density demarcation by interlobular septa In expiration ‘black’ areas remain in volume and density ‘white’ areas decrease in volume and increase in density INCREASE IN CONTRAST DIFFERENCES
- 13. Aortopulmonary Window Focal concavity in the left mediastinal border below the aorta and above the left pulmonary artery can be seen on a frontal radiograph . Its appearance may be modified by tortuosity of the aorta. The aortopulmonary window is a common site of lymphadenopathy in a variety of inflammatory and neoplastic diseases.
- 14. Lymph nodes Enlarged hilar shadow with lobulated outlines Normal
- 15. Lymph nodes Anatomic Considerations Retrosternal Prevascular Retrocaval Aortic window Carinal Subcarinal Hilar Z-esophageal Circm-cardiac 3 3
- 19. Apical Cap The usual appearance is of homogeneous soft-tissue attenuation capping the extreme lung apex (uni- or bilaterally), with a sharp or irregular lower border .Thickness is variable, ranging up to about 30 mm . An apical cap occasionally mimics apical consolidation on transverse CT scans.
- 20. Architectural Distortion Lung anatomy has a distorted appearance and is usually associated with pulmonary fibrosis and accompanied by volume loss.
- 21. Reduced volume is seen, accompanied by increased opacity (chest radiograph) or attenuation (CT scan) in the affected part of the lung . Atelectasis is often associated with abnormal displacement of fissures, bronchi, vessels,diaphragm, heart, or mediastinum .The distribution can be lobar, segmental, or subsegmental. Atelectasis is often qualified by descriptors such as linear,discoid, or platelike. Atelectasis
- 22. The definition of atelectasis is loss of air in the alveoli; alveoli devoid of air (not replaced). A diagnosis of atelectasis requires the following: 1-A density, representing lung devoid of air 2-Signs indicating loss of lung volume Atelectasis
- 23. 1-Absorption Atelectasis When airways are obstructed there is no further ventilation to the lungs and beyond. In the early stages, blood flow continues and gradually the oxygen and nitrogen get absorbed, resulting in atelectasis. Types of Atelectasis:
- 24. 2-Relaxation Atelectasis The lung is held close to the chest wall because of the negative pressure in the pleural space. Once the negative pressure is lost the lung tends to recoil due to elastic properties and becomes atelectatic. This occurs in patients with pneumothorax and pleural effusion. In this instance, the loss of negative pressure in the pleura permits the lung to relax, due to elastic recoil. There is common misconception that atelectasis is due to compression. Types of Atelectasis:
- 25. 3-Adhesive Atelectasis : Surfactant reduces surface tension and keeps the alveoli open. In conditions where there is loss of surfactant, the alveoli collapse and become atelectatic. In ARDS this occurs diffusely to both lungs. In pulmonary embolism due to loss of blood flow and lack of CO2, the integrity of surfactant gets impaired. Types of Atelectasis:
- 26. Types of Atelectasis: 4-Cicatricial Atelectasis –Alveoli gets trapped in scar and becomes atelectatic in fibrotic disorders
- 27. . 5-Round Atelectasis An instance where the lung gets trapped by pleural disease and is devoid of air. Classically encountered in asbestosis. Types of Atelectasis:
- 28. . 6-Compression Atelectasis Types of Atelectasis:
- 29. Generalized 1-Shift of mediastinum: The trachea and heart gets shifted towards the atelectatic lung. 2-Elevation of diaphragm: The diaphragm moves up and the normal relationship between left and right side gets altered. 3-Drooping of shoulder. 4-Crowding of ribs: The interspace between the ribs is narrower compared to the opposite side. Signs of Loss of Lung Volume:
- 30. Movement of Fissures You need a lateral view to appreciate the movement of oblique fissures. Forward movement of oblique fissure in LUL atelectasis. Backward movement in lower lobe atelectasis. Movement of transverse fissure can be recognized in the PA film. Signs of Loss of Lung Volume:
- 31. Movement of Hilum The right hilum is normally slightly lower than the left. This relationship will change with lobar atelectasis. Signs of Loss of Lung Volume:
- 32. Compensatory Hyperinflation Compensatory hyperinflation as evidenced by increased radiolucency and splaying of vessels can be seen with the normal lobe or opposite lung. Signs of Loss of Lung Volume:
- 33. Alterations in Proportion of Left and Right Lung The right lung is approximately 55% and left lung 45%. In atelectasis this apportionment will change and can be a clue to recognition of atelectasis. . Signs of Loss of Lung Volume:
- 34. Hemithorax Asymmetry In normals, the right and left hemithorax are equal in size. The size of the hemithorax will be asymmetrical and smaller on the side of atelectasis Signs of Loss of Lung Volume:
- 35. Signs of Loss of Lung Volume: Generalized Shift of mediastinum: The trachea and heart gets shifted towards the atelectatic lung. Elevation of diaphragm: The diaphragm moves up and the normal relationship between left and right side gets altered. Drooping of shoulder. Crowding of ribs: The interspace between the ribs is narrower compared to the opposite side. Movement of Fissures You need a lateral view to appreciate the movement of oblique fissures. Forward movement of oblique fissure in LUL atelectasis. Backward movement in lower lobe atelectasis. Movement of transverse fissure can be recognized in the PA film. Movement of Hilum The right hilum is normally slightly lower than the left. This relationship will change with lobar atelectasis. Compensatory Hyperinflation Compensatory hyperinflation as evidenced by increased radiolucency and splaying of vessels can be seen with the normal lobe or opposite lung. Alterations in Proportion of Left and Right Lung The right lung is approximately 55% and left lung 45%. In atelectasis this apportionment will change and can be a clue to recognition of atelectasis. Hemithorax Asymmetry In normals, the right and left hemithorax are equal in size. The size of the hemithorax will be asymmetrical and smaller on the side of atelectasis
- 36. Atelectasis Right Lung Homogenous density right hemithorax Mediastinal shift to right Right hemithorax smaller Right heart and diaphragmatic silhouette are not identifiable
- 37. Atelectasis Left Lung Homogenous density left hemithorax Mediastinal shift to left Left hemithorax smaller Diaphragm and heart silhouette are not identifiable
- 38. Left Lower Lobe Atelectasis • Inhomogeneous cardiac density • Left hilum pulled down • Non-visualization of left diaphragm • Triangular retrocardiac atelectatic LLL
- 39. Atelectasis Left Lower Lobe Double density over heart Inhomogenous cardiac density Triangular retrocardiac density Left hilum pulled down Other findings include: Pneumomediastinum
- 40. Atelectasis Left Upper Lobe Mediastinal shift to left Density left upper lung field Loss of aortic knob and left hilar silhouettes Herniation of right lung Atelectatic left upper lobe Forward movement of left oblique fissure "Bowing sign"
- 41. Atelectasis Left Upper Lobe Hazy density over left upper lung field Loss of left heart silhouette Tracheal shift to left Lateral A: Forward movement of oblique fissure B: Herniated right lung C: Atelectatic LUL
- 42. Lateral Movement of oblique and transverse fissures Atelectasis Right Upper Lobe Homogenous density right upper lung field Mediastinal shift to right Loss of silhouette of ascending aorta
- 43. Lateral Movement of oblique and transverse fissures Atelectasis Right Upper Lobe Homogenous density right upper lung field Mediastinal shift to right Loss of silhouette of ascending aorta
- 44. RML Atelectasis Vague density in right lower lung field, almost normal RML atelectasis in lateral view, not evident in PA view
- 45. Vague density in right lower lung field (almost a normal film). Dramatic RML atelectasis in lateral view, not evident in PA view. Movement of transverse fissure. Other findings include: Azygous lobe
- 46. Atelectasis Right Lower Lobe Density in right lower lung field Indistinct right diaphragm Right heart silhouette retained Transverse fissure moved down Right hilum moved down
- 47. Adhesive Atelectasis Alveoli are kept open by the integrity of surfactant. When there is loss of surfactant, alveoli collapse. ARDS is an example of diffuse alveolar atelectasis. Plate-like atelectasis is an example of focal loss of surfactant.
- 48. Relaxation Atelectasis The lung is held in apposition to the chest wall because of negative pressure in the pleura. When the negative pressure is lost, as in pneumothorax or pleural effusion, the lung relaxes to its atelectatic position. The atelectasis is a secondary event. The pleural problem is primary and dictates other radiological findings.
- 49. Round Atelectasis Mass like density Pleural based Base of lungs Blunting of costophrenic angle Pleural thickening Pulmonary vasculature curving into the density Esophageal surgical clips
- 50. Round Atelectasis Mass like density Pleural based Base of lungs Blunting of costophrenic angle, pleural thickening Pulmonary vasculature curving into the density
- 51. RML Lateral Segment Atelectasis
- 53. Atelectasis Segmental Anterior sub-segment of RUL "Bronchial wedge"
- 54. The azygoesophageal recess on a frontal chest radiograph, is seen as a vertically oriented interface between the right lower lobe and the adjacent mediastinum (the medial limit of the recess). Superiorly, the interface is seen as a smooth arc with convexity to the left. Disappearance or distortion of part of the interface suggests disease (eg, subcarinal lymphadenopathy). On CT scans, the recess merits attentionbecause small lesions located in the recess will often be invisible on chest radiographs Azygoesophageal Recess
- 55. Acute interstitial pneumonia, or AIP In the acute phase, patchy bilateral groundglass opacities are seen , often with some sparing of individual lobules, producing a geographic appearance; dense opacification is seen in the dependent lung . In the organizing phase, architectural distortion, traction bronchiectasis, cysts, and reticular opacities are seen .
- 56. Azygos Fissure
- 57. Beaded Septum Sign This sign consists of irregular and nodular thickening of interlobular septa reminiscent of a row of beads . It is frequently seen in lymphangitic spread of cancer and less often in sarcoidosis .
- 58. Bleb Anatomy.—A bleb is a small gas-containing space within the visceral pleura or in the subpleural lung, not larger than 1 cm in diameter . CT scans.—A bleb appears as a thin-walled cystic air space contiguous with the pleura. Because the arbitrary (size) distinction between a bleb andbulla is of little clinical importance, the use of this term by radiologists is discouraged.
- 60. Bulla Definition •Thin-walled–less than 1 mm •Air-filled space •In the lung> 1 cm in size and up to 75% of lung •Walls may be formed by pleura, septa, or compressed lung tissue. •Results from destruction, dilatation and confluence of airspaces distal to terminal bronchioles.
- 61. •Bullous disease may be primary or associated with emphysema or interstitial lung disease. • Primary bullous lung disease may be familial and has been associated with Marfan's, Ehler's Danlos, IV drug users, HIV infection, and vanishing lung syndrome. •Bullae may occasionally become very large and compromise respiratory function. Thus has been referred as vanishing lung syndrome, and may be seen in young men.
- 62. Upper lobe Bulla
- 63. Lower lobe Bulla
- 64. A: Xray shows bilateral bulla. B: CT shows bilateral bulla. C: CT after bullectomy.
- 66. Pneumatocele is a benign air containing cyst of lung, with thin wall < 1mm as bulla but with different mechanism Infection with staph aureus is the commonest cause ( less common causes are, trauma, barotrauma) lead to necrosis and liquefaction followed by air leak and subpleural dissection forming a thin walled cyst.
- 67. •Honeycombing is defined as multiple cysts < 1cm in diameter,with well defined walls, in a background of fibrosis, tend to form clusters and is considered as end stage lung . •It is formed by extensive interstitial fibrosis of lung with residual cystic areas.
- 69. A cyst is a ring shadow > 1 cm in diameter and up to 10 cm with wall thickness from 1-3 mm.
- 71. Thin walled cysts of LAM
- 72. A cavity is > 1cm in diameter, and its wall thickness is more than 3 mm.
- 73. •A central portion necrosis and communicate to bronchus. •The draining bronchus is visible (arrow). CT (2 mm slice thickness) shows discrete air bronchograms in the consolidated area. Mechanism
- 74. 1. Site
- 75. A cavity in apicoposterior segment of left upper lobe
- 76. 2.Number Multiple cavities: 1. Aspiration. 2. TB 3. Fungal. 4. Metastatic. 5. Septic emboli. 6.Wegners granulomatosis
- 77. Multiple cysts of metastasis from squamous cell carcinoma. Multiple thick wall cavities from adenocarcinoma of right lung
- 80. Irregular , nodular inner lining of thick wall abscess Malignant cavity. 3. Thickness and irregularity
- 82. 5. Relation to lymph node enlargement
- 83. 6. Contents
- 84. •Arrow head Crescent sign. •Black arrows Fibrotic bands surrounding cavity (Fibrocavitary TB).
- 86. Morphologic criteria on thin-section CT scans include bronchial dilatation with respect to the accompanying pulmonary artery (signet ring sign), lack of tapering of bronchi, and identification of bronchi within 1 cm of the pleural surface (27) (Fig 11). Bronchiectasis may be classified as cylindric, varicose, or cystic, depending on the appearance of the affected bronchi. It is often accompanied by bronchial wall thickening, mucoid impaction, and small- airways abnormalities Bronchiectasis
- 87. Bronchiolectasis When dilated bronchioles are filled with exudate and are thick walled, they are visible as a tree-in-bud pattern or as centrilobular nodules. In traction bronchiolectasis, the dilated bronchioles are seen as small, cystic, tubular airspaces, associated with CT findings of fibrosis
- 88. bronchocele is a tubular or branching Yor V-shaped structure that may resemble a gloved finger (Fig 13). The CT attenuation of the mucus is generally that of soft tissue but may be modified by its composition (eg, high-attenuation material in allergic bronchopulmonary aspergillosis). In the case of bronchial atresia, the surrounding lung may be of decreased attenuation because of reduced ventilation and, thus, perfusion. Bronchocele
- 89. Bronchiolitis This direct sign of bronchiolar inflammation (eg, infectious cause) is most often seen as the tree-inbud pattern, centrilobular nodules, and bronchiolar wall thickening .
- 90. This descriptor is applied to disease that is conspicuously centered on macroscopic bronchovascular bundles . Examples of diseases with a bronchocentric distribution include sarcoidosis , Kaposi sarcoma , and organizing pneumonia Bronchocentric
- 91. The imaging appearance is of a small calcific focus in or immediately adjacent to anairway (Fig 15), most frequently the right middle lobe bronchus. Broncholiths are readily identified on CT scans . Distal obstructive changes may include atelectasis, mucoid impaction, and bronchiectasis. Broncholith
- 92. An airspace measuring more than 1 cm— usually several centimeters in diameter, sharply demarcated by a thin wall that is no greater than 1 mm in thickness. A bulla is usually accompanied by emphysematous changes in the adjacent lung. Radiographs and CT scans.— A bulla appears as a rounded focal lucency or area of decreased attenuation, 1 cm or more in diameter, bounded by a thin wall . Multiple bullae are often present and are associated with other signs of pulmonary emphysema (centrilobular and paraseptal). Bulla
- 93. A cavity is a gas-filled space, seen as a lucency or low-attenuation area, within pulmonary consolidation, a mass, or a nodule . In the case of cavitating consolidation, the original consolidation may resolve and leave only a thin wall. A cavity is usually produced by the expulsion or drainage of a necrotic part of the lesion via the bronchial tree. It sometimes contains a fluid level. Cavity is not a synonym for abscess. Cavity
- 95. Number: Multiple bilateral cavities would raise suspicion for either bronchiogenous or hematogenous process. You should consider: Aspiration lung abscess Septic emboli Metastatic lesions Vasculitis (Wegener's) Coccidioidomycosis, tuberculosis
- 96. Location: • Classical locations for aspiration lung abscess are superior segment of the lower lobes posterior segments of upper lobes. • Tuberculous cavities are common in superior segments of upper and lower lobes or posterior segments of upper lobes. • When a cavity in anterior segment is encountered, a strong suspicion for lung cancer should be raised. TB and aspiration lung abscess are rare in anterior segments. Cancer lung can occur in any segment.
- 97. Wall Thickness: • Thick walls are seen in: – Lung abscess – Necrotizing squamous cell lung cancer – Wegener's granulomatosis – Blastomycosis
- 98. Wall Thickness: • Thin walled cavities are seen in: • Coccidioidomycosis • Metastatic cavitating squamous cell carcinoma from the cervix • M. Kansasii infection • Congenital or acquired bullae • Post-traumatic cysts • Open negative TB
- 99. Contents: • The most common cause for air fluid level is lung abscess. Air fluid levels can rarely be seen in malignancy and in tuberculous cavities from rupture of Rasmussen's aneurysm. • A fungous ball should make you consider aspergillosis. A blood clot and fibrin ball will have the same appearance. • Floating Water Lily: The collapsed membrane of a ruptured echinococcal cyst, floats giving this appearance.
- 100. Lining of Wall: The wall lining is irregular and nodular in lung cancer or shaggy in lung abscess
- 101. Evolution of Lesion: Many times review of old films to assess the evolution of the radiological appearance of the lesion extremely helpful. Examples • Infected bullae • Aspergilloma • Sub acute necrotizing aspergillosis • Bleeding from Rasmussen's aneurysm in a tuberculous cavity
- 102. Associated Features: Ipsilateral lymph nodes or lytic lesions of the bone is seen with malignancy
- 103. Centrilobular A small dotlike or linear opacity in the center of a normal secondary pulmonary lobule, most obvious within 1 cm of a pleural surface, represents the intralobular artery (approximately1 mm in diameter) . Centrilobular abnormalities include (a) nodules, (b) a tree-in-bud pattern indicating small-airways disease, (c) increased vis-ibility of centrilobular structures due to thickening or infiltration of the adjacent interstitium, or (d) abnormal areas of low attenuation caused by centrilobular emphysema
- 104. CT findings are centrilobular areas of decreased attenuation, usually without visible walls, of nonuniform distribution and predominantly located in upper lung zones . The term centriacinar emphysema is synonymous. Centrilobular Emphysema
- 105. Consolidation appears as a homogeneous increase in pulmonary parenchymal attenuation that obscures the margins of vessels and airway walls .An air bronchogram may be present. The attenuation characteristics of consolidated lung are only rarely helpful in differential diagnosis (eg, decreased attenuation in lipoid pneumonia and increased in amiodarone toxicity Consolidation
- 106. Crazy-paving Pattern This pattern appears as thickened interlobular septa and intralobular lines superimposed on a background of ground- glass opacity , resembling irregularly shaped paving stones. The crazy-paving pattern is often sharply demarcated from more normal lung and may have a geographic outline. It was originally reported in patients with alveolar proteinosis and is also encountered in other diffuse lung diseases that affect both the interstitial and airspace compartments, such as lipoid pneumonia
- 107. Cyst A cyst appears as a round parenchymal lucency or low-attenuating area with a well-defined interface with normal lung. Cysts have variable wall thickness but are usually thin-walled (2 mm) and occur without associated pulmonary emphysema . Cysts in the lung usually contain air but occasionally contain fluid or solid material. The term is often used to describe enlarged thinwalled airspaces in patients with lymphangioleiomyomatosis or Langerhans cell histiocytosis ; thickerwalled honeycomb cysts are seen in patients with end-stage fibrosis .
- 108. Ground-glass opacity is the dominant abnormality and tends to have a basal and peripheral distribution . Microcystic or honeycomb changes in the area of ground- glass opacity are seen in some cases . Desquamative Interstitial Pneumonia or DIP
- 109. Ground-Glass Opacity or GGO it appears as hazy increased opacity of lung, with preservation of bronchial and vascular margins .It is caused by partial filling of airspaces, interstitial thickening (due to fluid, cells, and/or fibrosis), partial collapse of alveoli, increased capillary blood volume, or a combination of these, the common factor being the partial displacement of air .Ground-glass opacity is less opaque than consolidation, in which bronchovascular margins are obscured.
- 110. T h e h a l o s i g n i s a C T f i n d i n g of ground-glass opacity surrounding a n o d u l e o r m a s s . I t w a s f i r s t described as a sign of hemorrhage around foci of invasive aspergillosis . The hal o si gn is nonspecific and may also be caused by hemorrhage associated with other types of nodules o r b y l oc a l p u l m o n a ry i nf i l t r at i o n by neoplasm (eg, adenocarcinoma). Halo Sign
- 111. On chest radiographs, honeycombing appears as closely approximated ring shadows, typically 3–10 mm in diameter with walls 1–3 mm in thickness, that resemble a honeycomb; the finding implies end- stage lung disease. On CT scans, the appearance is of clustered cystic air spaces, typically of comparable diameters on the order of 3–10 mm but occasionally as large as 2.5 cm . Honeycombing is usually subpleural and is characterized by well- defined walls . It is a CT feature of established pulmonary fibrosis . Because honeycombing is often considered specific for pulmonary fibrosis and is an important criterion in the diagnosis of usual interstitial pneumonia (63), the term should be used with care, as it may directly impact patient care. Honeycombing
- 112. The typical imaging findings are reticular opacities and honeycombing, with a predominantly peripheral and basal distribution . Ground-glass opacity, if present, is less extensive than reticular and honeycombing patterns. The typical radiologic findings are also encountered in usual interstitial pneumonia secondary to specific causes, such as asbestos-induced pulmonary fibrosis (asbestosis), and the diagnosis is usually one of exclusion. Idiopathic pulmonary fibrosis
- 113. A pulmonary infarct is typically triangular or dome-shaped, with the base abutting the pleura and the apex directed toward the hilum.The opacity represents local hemorrhage with or without central tissue necrosis Infarction
- 114. Interlobular septal thickening This finding is seen on chest radiographs as thin linear opacities at right angles to and in contact with the lateral pleural surfaces near the lung bases (Kerley B lines); it is seen most frequently in lymphangitic spread of cancer or pulmonary edema. Kerley A lines are predominantly situated in the upper lobes, are 2–6 cm long, and can be seen as fine lines radially oriented toward the hila. In recent years, the anatomically descriptive terms septal lines and septal thickening have gained favor over Kerley lines. On CT scans, disease affecting one of the components of the septa (see interlobular septum) may be responsible for thickening and so render septa visible. On thin-section CT scans, septal thickening may be smooth or nodular , which may help refine the differential diagnosis.
- 115. Interlobular septum Interlobular septa appear as thin linear opacities between lobules ; these septa are to be distinguished from centrilobular structures. They are not usually seen in the healthy lung (normal septa are approximately 0.1 mm thick) but are clearly visible when thickened (eg, by pulmonary edema).
- 116. Interstitial emphysema is rarely recognized radiographically in adults and is infrequently seen on CT scans . It appears as perivascular lucent or lowattenuating halos and small cysts Interstitial emphysema
- 117. Intralobular lines are visible as fine linear opacities in a lobule when the intralobular interstitial tissue is abnormally thickened . When numerous, they may appear as a fine reticular pattern. Intralobular lines may be seen in various conditions, including interstitial fibrosis and alveolar proteinosis Intralobular lines