In vivo dose assessment of multislice CT in abdominal examinations

Purpose: To assess in vivo doses of multislice computed tomography in abdominal examinations taken by two novel CT scanners. Materials and methods: Abdominal multislice CT (MSCT) examinations were taken with 120 kVp two novel CT scanners, i.e. Siemens Sensation 64 and Philips Brilliance 40. Those two scanners have different detector configurations, i.e. 64 × 0.6 and 40 × 0.625. Surface dose distributions on 20 patients (female: 9, male: 11), undergoing abdominal MSCT examinations, were measured using TLD-100H (LiF:Mg, Cu, P) thermoluminicent dosimeters (TLD), which were calibrated by a 137Cs source in National Tsing-Hwa University. Scaling factors for individual patients were developed according to cross-section area, weight and body mass index. Organ doses were measured using TLDs within an anthropomorphic phantom and then multiplied by tissue weighting factors from ICRP 60 report to calculate effective dose. Patient doses were derived by applying individual scaling factors to phantom's dose. Results: In-plane surface doses are from 16.8 to 50.5 mSv for males and from 13.0 to 61.5 mSv for females. Out-plane surface doses range from 1.1 to 8.0 mSv for males and from 1.4 to 9.6 mSv for females. Effective doses and the standard deviations are 27.3 ± 4.1 mSv for males and 33.9 ± 9.6 mSv for females. Conclusions: Applying scaling factors to evaluate effective dose for individual patients is realistic. Dose calculations from TLD measurements within an anthropomorphic phantom and surface dose monitoring on patients are efficient methods to estimate effective doses for individual patients. In vivo dose assessment for abdominal MSCT examination is useful and practical.