Low-dose computed tomography of the thorax. Experimental and clinical investigations

Computed tomography is a significant source of medical radiation exposure for populations in Europe. Reduced radiation exposure may be possible with modern CT scanners with an image quality that while less good than before remains acceptable for clinical puposes. The lung appears particularly well suited to investigation with low-dose CT owing to the high contrast between normal and diseased pulmonary parenchyma. We analysed the diagnostic accuracy of different low-dose CT protocols for the detection of pulmonary nodules using inflationfixed isolated postmortem lung specimens in a chest phantom. In a comparative patient study diagnostic accuracies of standard-dose CT (120 kV, 250 mAs; slice thickness 10 mm, pitch 1) and low-dose CT (120 or 140 kV, 50 mAs; slice thickness 5 or 10 mm, pitch 1 or 2) were assessed. Preliminary results suggest that low-dose CT protocols with radiation exposure of 10-20% of that with standard-dose CT can reliably depict soft tissue density pulmonary nodules with a diameter of more than 5 mm and can also demonstrate smaller nodules equally well in many cases. Low-dose CT may frequently be an adequate imaging procedure in a given clinical setting, particularly in young patients with benign disease. (orig.)