What type of CT scan is indicated for the evaluation of interstitial lung disease?
CT scanning has inherently less spatial resolution than standard chest radiography. As interstitial lung diseases are typified by very fine spatial abnormalities, it is necessary to maximize the spatial resolution of CT images by minimizing the slice thickness, usually to 0.5 to 1.5 mm. Modern multislice helical CT scanners are typically set to generate thin-slice images in nearly all chest CT studies and generate so-called high-resolution CT (HRCT) chest CT scans because of the improved spatial resolution that is characteristic of the studies. Thin-section expiratory CT images are also often obtained to detect presence of pulmonary air trapping, which may occur in association with interstitial lung disease. Furthermore, prone CT images may be acquired if posterior peripheral interstitial lung disease is suspected in order to minimize obscuration and confounding by dependent atelectasis present in the supine position.