[Increased transparency in thin-slice computed tomography of lung parenchyma]

Area of Science:

• Radiology
• Pulmonary Medicine
• Medical Imaging

Background:

• Reduced lung density is a common finding on thin-slice computed tomography (CT) of the lung parenchyma.
• These findings can present as diffuse or localized patterns, requiring careful differentiation.

Purpose of the Study:

• To outline the differential diagnosis of reduced lung density on CT.
• To categorize findings into diffuse and localized patterns and discuss their common causes.

Main Methods:

• Review of thin-slice CT findings in lung parenchyma.
• Classification of reduced lung density patterns: diffuse (emphysema, mosaic pattern) and localized (cystic changes).

Main Results:

• Pulmonary emphysema (centrilobular, panlobular, paraseptal) is the most frequent cause of diffuse low density.
• Mosaic patterns indicate mosaic perfusion or air trapping.
• Focal cystic changes, such as those seen in Langerhans cell histiocytosis and lymphangioleiomyomatosis, are differentiated by wall structures.

Conclusions:

• CT allows differentiation between emphysematous changes, mosaic patterns, and focal cystic diseases based on anatomical features.
• Rare causes of reduced lung density include Birt-Hogg-Dubé syndrome, lymphoid interstitial pneumonia, and congenital/childhood diseases.