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Sequential Versus Volumetric Computed Tomography in the Follow-up of Chronic Bronchopulmonary Diseases: Comparison of Diagnostic Information and Radiation Dose in 63 Adults

Purpose To compare diagnostic information and radiation dose between volumetric and sequential scanning in the follow-up of chronic and diffuse bronchopulmonary diseases. Materials and Methods Sixty-three consecutive patients, aged 50 years or younger, referred for the follow-up of diffuse infiltrative lung disease (group 1; n=38) or cystic fibrosis (group 2; n=25), underwent a noncontrast high-resolution volumetric computed tomography (CT) examination with individually adapted selection of kilovoltage and 4-dimensional tube current modulation. From each acquisition, 2 sets of lung images were generated, namely the contiguous thin-collimated lung images, further referred to as the volumetric examination and considered as the reference standard, and thin-collimated lung images, spaced 10 mm apart, further referred to as the sequential examination. Several weeks apart, 2 radiologists interpreted by consensus the volumetric and sequential examinations to assess the presence and extent of lung parenchyma and airways abnormalities. The dose-length-product (DLP) value of each volumetric examination was available at the acquisition workstation; the DLP value of the corresponding sequential examination was retrospectively calculated. Results In group 1, the &kgr; values between sequential and volumetric CT examinations ranged between 0.87 and 1 for the detection of individual CT features and between 0.83 and 1 for the regional distribution of the CT features. In group 2, the values of the intraclass correlation coefficients (r) for individual criteria of the scoring system ranged between 0.87 and 1, except for the extent of mucus plugging (r: 0.67); the r value for the patients' Bhalla score was 0.99. The mean DLP of sequential examinations was significantly lower than that of the volumetric examinations (16.1 mGy.cm vs. 77.7 mGy.cm; P<0.0001), enabling a 79.4% dose reduction. Conclusion The magnitude of dose reduction without loss of diagnostic information achievable with sequential scanning suggests reconsidering this scanning mode in the follow-up of chronic diffuse bronchopulmonary diseases in adults 50 years of age and younger.