Centrilobular Emphysema

value of −960 to −970 HU has been shown to be suitable for quantifying emphysema in continuous volume data sets obtained with multidetector CT [34].

4.Numerous studies have demonstrated a significant correlation between the CT emphysema index (the proportion of the lung affected by emphysema) and pulmonary function test results [35]. However, airflow limitation in COPD is a complicated phenomenon that is related only in part to emphysematous lung destruction; therefore, the extent of emphysema does not always correlate with the severity of airflow limitation [36].

5.Although CT densitometry parameters may be used as rough indicators of the extent of emphysema, they provide no information about the distribution or size of low-attenuation clusters. Therefore, the anatomic distribution of emphysema should be taken into account in quantitative CT analysis of low-attenuation clusters (the size and number of clusters are calculated by grouping adjacent lowattenuation voxels together) [34].

6.Texture-based quantification of emphysema using an automated system shows better correlation with the lung function test results than densitometrybased quantification [37].

7.Quantitative CT analyses can help differentiate COPD phenotypes (emphysema predominant, airway predominant, and mixed) [38, 39].

emphysema are centrilobular areas of decreased attenuation, usually without visible walls, of nonuniform distribution and are predominantly located in the upper lung zones [41] (Fig. 23.7). Areas of lucency often appear to be grouped near the centers of secondary pulmonary lobules, surrounding the centrilobular artery branches. With more severe centrilobular emphysema, areas of destruction can become confluent (Fig. 23.7).

Patient Prognosis

Smoking cessation is the essential part of lung care. Prognosis is usually dependent on the lung function at the time of diagnosis. Bronchodilator therapy is often ineffective.

Paraseptal Emphysema

Pathology and Pathogenesis

Paraseptal emphysema is characterized by predominant involvement of the distal alveoli and their ducts and sacs. It is characteristically bounded by any pleural surface and the interlobular septa [32] (Fig. 23.8).

Symptoms and Signs

Most patients are asymptomatic. Pulmonary function is normal or nearly normal. Sudden chest pain with dyspnea can occur in the cases of pneumothorax.

Centrilobular Emphysema

Pathology and Pathogenesis

Centrilobular emphysema is characterized by destroyed centrilobular alveolar walls and enlargement of respiratory bronchioles and associated alveoli (Fig. 23.7). This is the most common form of emphysema in cigarette smokers [40].

CT Findings

Paraseptal emphysema is characterized by predominant involvement of the distal alveoli and their ducts and sacs. On CT it is characterized by subpleural and peribronchovascular regions of low attenuation separated by intact interlobular septa (Fig. 23.8).

Symptoms and Signs

Depending on the extent of emphysema, clinical manifestations of the patients with centrilobular emphysema are variable. They may be asymptomatic or severely dyspneic even at rest. Tachypnea and barrel chest can be observed in severely dyspneic patients. Cyanosis is rare.

CT Findings

Centrilobular emphysema is characterized by destroyed centrilobular alveolar walls and enlargement of respiratory bronchioles and associated alveoli. CT findings of centrilobular

Patient Prognosis

Unless patients smoke, prognosis is excellent since pulmonary function is normal.

Panacinar Emphysema Associated with α1-Antitrypsin Deficiency

Pathology and Pathogenesis

Panacinar emphysema involves all portions of the acinus and secondary pulmonary lobule more or less uniformly. It predominates in the lower lobes and is the form of emphysema associated with α1-antitrypsin deficiency [40].

Fig. 23.7 Centrilobular emphysema in a 65-year-old smoker man. (a, b) Lung window images of thin-section (1.0-mm section thickness) CT scans obtained at levels of aortic arch (a) and suprahepatic inferior vena cava (b), respectively, show extensive emphysema involving whole lungs. Emphysema is variable in their size and involves both upper and lower lung zones, suggesting extensive centrilobular emphysema than panlobular emphysema (which involves

predominantly lower lung zones). (c) Coronal reformatted image (2.0-mm section thickness) demonstrates emphysema mainly in upper lung zones (arrows), but also lung bases (open arrows). (d) Highmagnification (×200) photomicrograph of surgical biopsy specimen from a different patient discloses emphysematous areas (arrows), destroyed centrilobular alveolar walls, and enlargement of respiratory bronchioles and associated alveoli

The most common manifestation of α1-antitrypsin deficiency is early-onset (patients in their 30s and 40s) emphysema and bronchiectasis [42]. Cough, dyspnea, and wheezing are the frequently described symptoms. Extrapulmonary features of liver disease (chronic hepatitis and cirrhosis), skin disease (panniculitis), and vasculitis can be associated.

Panacinar emphysema involves all portions of the acinus and secondary pulmonary lobule more or less uniformly. It manifests as a generalized decrease in lung parenchymal attenuation with a decrease in the caliber of pulmonary vessels in the affected lungs [43] (Fig. 23.9).

Fig. 23.8 Paraseptal (distal acinar, bullous) emphysema showing evolution in a 50-year-old smoker man. (a, b) Lung window images of thin-section (1.0-mm section thickness) CT scans obtained at levels of aortic arch (a) and right bronchus intermedius (b), respectively, show

paraseptal emphysema (arrows) involving mainly upper lung zones. (c, d) Fifty-month follow-up CT scans obtained at similar levels to a and b, respectively, demonstrate much increased extent of paraseptal emphysema (arrows) in both lungs

Fig. 23.9 Panlobular emphysema in a 55-year-old man. (a, b) Lung window images of thin-section (1.0-mm section thickness) CT scans obtained at levels of right inferior pulmonary vein (a) and liver dome

(b), respectively, show extensive areas of emphysema in lower lung zones. Please note whole secondary pulmonary lobules (arrows) are involved with emphysematous processes