Comparison of different body size parameters for individual dose adaptation in body CT of adults

PURPOSE: To investigate prospectively which of several body size parameters are suitable for individual dose adaptation in body computed tomography (CT) of adults. MATERIALS AND METHODS: Three body regions (thorax, abdomen, pelvis) were scanned exclusively for clinical reasons, with institutional ethical approval and informed consent. For each of the three regions, 50 men and 50 women (aged 18-87 years) were studied (300 scans total). Individual x-ray properties for each scan were summarized with a water-equivalent diameter (D-w). Different body size parameters, based on weight, height, and shape, were correlated with D-w by using regression analysis. This resulted in D-w estimation errors of different magnitudes, indicated with 95% prediction intervals. The errors from weight were compared with those from each of the other body parameters by using comparison of variance in paired samples (P < .05). In addition, a topogram-based estimate for D-w was studied, which simulated an automated body size measurement. RESULTS: For the thorax, abdomen, and pelvis, mean D-w was 28.0, 29.1, and 29.3 cm, and estimation of D-w from weight enabled 95% prediction intervals of +/- 2.5, +/- 2.4, and +/- 2.6 cm, respectively. Combinations of height and weight were only slightly more or even less exact than were measurements from only weight. Diameter-related parameters such as body circumference were similar to or better than weight. However, the topogram-based estimate was significantly more exact. CONCLUSION: Body weight and circumference enable suitable estimates for individual dose adaptation in body CT of adults if automated dose adaptation is not available. (c) RSNA, 2005.