PULMONARY NODULE DETECTION - LOW-DOSE VERSUS CONVENTIONAL CT

PURPOSE: To quantitate the effectiveness of low-dose computed tomograp hy (CT) in the identification of pulmonary nodules while controlling f or anatomic nodule characteristics and to establish what factors lead to reduced diagnostic sensitivity at low-dose CT. MATERIALS AND METHOD S: Each of six participating radiologists independently rated 200 imag e panels by using a four-point confidence scale. Conventional images w ere obtained at 200 mAs; low-dose images were obtained at 20 mAs. To f ully control their characteristics, nodules were simulated with a give n diameter, shape, and section thickness while preserving the resoluti on, noise level, and reconstruction artifacts of the original images. Panels were matched so that nodules on low-dose and conventional image s had equivalent sizes, locations, and relationships to blood vessels. RESULTS: Among 864 positive panels, 259 (60%) of 432 low-dose panels and 272 (63%) of 432 conventional panels were correctly interpreted (P = .259). Lowering the x-ray dose significantly reduced the detectabil ity of peripheral nodules (P = .019) and nodules separated from blood vessels (P = .044). Surprisingly, 3-mm nodules were detected with appr oximately equal sensitivity (P = .181) at conventional and low-dose CT . The specificity of low-dose images was 88% (148 of 168 panels) versu s 91% (153 of 168 panels) for conventional images (P = .372). CONCLUSI ON: Low-dose CT is acceptable for pulmonary nodule identification, mak ing it suitable for primary screening. These results confirm the stron g effect of size, location, and angiocentricity on the sensitivity of nodule detection with conventional CT.