Answer
Answer
CT scanning of the chest, especially high-resolution CT (HRCT), has a much greater sensitivity and specificity than those of plain chest radiography in diagnosing and assessing the severity of emphysema (see the images below). [16] HRCT is useful in the workup of smokers with new-onset or progressive dyspnea. The severity of emphysematous change may be underestimated on conventional radiography, whereas HRCT depicts combined fibrosis and emphysema. [17] Patients with these conditions may have relatively normal lung volumes and spirometric results, but they may have severe dyspnea and a reduced diffusing capacity. In healthy nonsmokers aged 19-40 years, a maximum of 0.35% of the area of emphysema can be detected by means of CT quantification. [18]
CT can depict surgically treatable areas of bullous disease that are not evident on plain chest radiography. CT is also useful in predicting the outcome of surgery. HRCT may be useful in diagnosing subclinical or mild emphysema, and HRCT can be used to differentiate the pathologic types of emphysema. However, CT scanning is not yet used to routinely evaluate patients with COPD. Instead, it is reserved for patients in whom the diagnosis is in doubt, to look for coexistent pathologies, and to assess their suitability for surgical intervention. [6, 19, 20, 21, 22, 23, 24, 25, 26, 27]
High-resolution CT (HRCT) in a patient after viral bronchiolitis obliterans demonstrates areas of airtrapping, which is predominant in the inferior lobes and associated with bronchiectasis in the left lower lobe. Note that the decreased attenuation caused by the airtrapping can simulate emphysema (Corrêa da Silva, 2001).
Pediatric high-resolution CT (HRCT) shows a hyperinflated right lung with large pulmonary bullae due to congenital lobar emphysema (Corrêa da Silva, 2001).
High-resolution CT (HRCT) demonstrates areas of centriacinar emphysema. Note the low attenuation areas without walls due to destruction of the alveoli septae centrally in the acini. Red element shows the size of a normal acinus (Corrêa da Silva, 2001).
High-resolution CT (HRCT) shows large bullae in both inferior lobes due to uniform enlargement and destruction of the alveoli walls causing distortion of the pulmonary architecture (Corrêa da Silva, 2001).
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Media Gallery
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Chest radiograph of an emphysematous patient shows hyperinflated lungs with reduced vascular markings. Pulmonary hila are prominent, suggesting some degree of pulmonary hypertension (Corrêa da Silva, 2001).
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Schematic representation of 1 criterion for defining flattening of the diaphragm on the lateral chest radiograph: drawing a line from the posterior to anterior costophrenic angles and measuring the distance from this line to the apex of the diaphragm. If the height is less than 1.5 cm, the criterion of flattening is fulfilled (Corrêa da Silva, 2001).
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Schematic representation of another criterion for defining flattening of the diaphragm on the lateral chest radiograph. When the angle formed by the contact point between the diaphragm and the anterior thoracic wall is more than or equal to 90°, the criterion is fulfilled (Corrêa da Silva, 2001).
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Schematic representation of another sign of emphysema on the lateral chest radiograph. When the retrosternal space (defined as the space between the posterior border of the sternum and the anterior wall of the mediastinum) is larger than 2.5 cm, it is highly suggestive of overinflated lungs. This radiograph is from a patient with pectus carinatum, an important differential diagnosis to consider when this space is measured (Corrêa da Silva, 2001).
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Close-up image shows emphysematous bullae in the left upper lobe. Note the subpleural, thin-walled, cystlike appearance (Corrêa da Silva, 2001).
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A, Frontal posteroanterior (PA) chest radiograph shows no abnormality of the pulmonary vasculature, with normal intercostal spaces and a diaphragmatic dome between the 6th and 7th anterior ribs on both sides. B, Image in a patient with emphysema demonstrating reduced pulmonary vasculature resulting in hyperlucent lungs. The intercostal spaces are mildly enlarged, and the diaphragmatic domes are straightened and below the extremity of the seventh rib (Corrêa da Silva, 2001).
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A, Lateral radiograph of the chest shows normal pulmonary vasculature, a retrosternal space within normal limits (< 2.5 cm), and a normal angle between the diaphragm and the anterior thoracic wall. B, Lateral view of the chest shows increased pulmonary transparency, increased retrosternal space (>2.5 cm), and an angle between the thoracic wall and the diaphragm >90°. Straightening of the diaphragm can be more evident in this projection than on others (Corrêa da Silva, 2001).
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High-resolution CT (HRCT) in a patient after viral bronchiolitis obliterans demonstrates areas of airtrapping, which is predominant in the inferior lobes and associated with bronchiectasis in the left lower lobe. Note that the decreased attenuation caused by the airtrapping can simulate emphysema (Corrêa da Silva, 2001).
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Pediatric high-resolution CT (HRCT) shows a hyperinflated right lung with large pulmonary bullae due to congenital lobar emphysema (Corrêa da Silva, 2001).
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Algorithmic representation of emphysema that Reid proposed in 1956.
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Pulmonary acinus measures 6-10 mm (red or blue). When normal, the distal terminal bronchiole used to define the acinus cannot be resolved on high-resolution CT (HRCT). Image represents the proportion of acini in relation to the lung image. One lobule, as Reid defined it, can have 3-5 acini (red groups). A secondary pulmonary lobule described by the interstitial septa can have as many as 100 acini (blue groups, the biggest one showing a pulmonary lobule containing about 35 acini) (Corrêa da Silva, 2001).
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High-resolution CT (HRCT) demonstrates areas of centriacinar emphysema. Note the low attenuation areas without walls due to destruction of the alveoli septae centrally in the acini. Red element shows the size of a normal acinus (Corrêa da Silva, 2001).
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High-resolution CT (HRCT) shows large bullae in both inferior lobes due to uniform enlargement and destruction of the alveoli walls causing distortion of the pulmonary architecture (Corrêa da Silva, 2001).
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Panacinar emphysema of the left lung in a patient with a right lung transplant. Note the red element showing the size of a normal acinus and its discrepancy with the destroyed and enlarged airspaces of the left lower lobe (Corrêa da Silva, 2001).
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High-resolution CT (HRCT) shows bullae distributed in the subpleural spaces including the fissures; this is characteristic of paraseptal emphysema (Corrêa da Silva, 2001).
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High-resolution CT (HRCT) shows subpleural bullae consistent with paraseptal emphysema. Red mark shows the size of a normal acinus (Corrêa da Silva, 2001).
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High-resolution CT (HRCT) shows enlarged air-spaces or bullae adjoining pulmonary scars, consistent with paracicatricial emphysema. Red mark shows the size of a normal acinus (Corrêa da Silva, 2001).
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CT densitovolumetry of a nonsmoker, healthy young patient shows normal lungs. Less than 0.35% of lungs have attenuations below -950 HU (Corrêa da Silva, 2001).
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Expiratory CT densitovolumetry shows no areas of airtrapping (Corrêa da Silva, 2001).
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CT densitovolumetry in a heavy smoker with emphysema revealed compromise of about 22% of the lung parenchyma (Corrêa da Silva, 2001).
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CT densitovolumetry in a patient with lung cancer. Three-dimensional (3D) image shows that the cancer is in the portion of the right lung that was less affected by emphysema in a patient with poor pulmonary function (Corrêa da Silva, 2001).
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CT densitovolumetry shows the attenuation mask. Green areas are those with attenuation below the selected threshold (here, -950 HU to evaluate emphysema), and pink areas are those with attenuations above the threshold. Area outside the patient is highlighted in green because of air (Corrêa da Silva, 2001).
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CT densitovolumetry demonstrates irregular distribution of the emphysema, with substantial predominance in the left lung (Corrêa da Silva, 2001).
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