Organ doses for reference adult male and female undergoing computed tomography estimated by Monte Carlo simulations

Abstract

Purpose: To develop a computed tomography ͑CT͒ organ dose estimation method designed to readily provide organ doses in a reference adult male and female for different scan ranges to investigate the degree to which existing commercial programs can reasonably match organ doses defined in these more anatomically realistic adult hybrid phantoms Methods: The x-ray fan beam in the SOMATOM Sensation 16 multidetector CT scanner was simulated within the Monte Carlo radiation transport code MCNPX2.6. The simulated CT scanner model was validated through comparison with experimentally measured lateral free-in-air dose profiles and computed tomography dose index ͑CTDI͒ values. The reference adult male and female hybrid phantoms were coupled with the established CT scanner model following arm removal to simulate clinical head and other body region scans. A set of organ dose matrices were calculated for a series of consecutive axial scans ranging from the top of the head to the bottom of the phantoms with a beam thickness of 10 mm and the tube potentials of 80, 100, and 120 kVp. The organ doses for head, chest, and abdomen/pelvis examinations were calculated based on the organ dose matrices and compared to those obtained from two commercial programs, CT-EXPO and CTDOSIMETRY. Organ dose calculations were repeated for an adult stylized phantom by using the same simulation method used for the adult hybrid phantom. Results: Comparisons of both lateral free-in-air dose profiles and CTDI values through experimental measurement with the Monte Carlo simulations showed good agreement to within 9%. Organ doses for head, chest, and abdomen/pelvis scans reported in the commercial programs exceeded those from the Monte Carlo calculations in both the hybrid and stylized phantoms in this study, sometimes by orders of magnitude. Conclusions: The organ dose estimation method and dose matrices established in this study readily provides organ doses for a reference adult male and female for different CT scan ranges and technical parameters. Organ doses from existing commercial programs do not reasonably match organ doses calculated for the hybrid phantoms due to differences in phantom anatomy, as well as differences in organ dose scaling parameters. The organ dose matrices developed in this study will be extended to cover different technical parameters, CT scanner models, and various age groups.

Dose estimation in reference and non-reference pediatric patients undergoing computed tomography examinations: a Monte Carlo study

“…The simulated doses of this study agreed with the measured ones with maximum error of almost 9% for all tube potentials. These results were comparable with those given in other published studies (Jarry et al, 2003;Staton et al, 2006;Lee et al, 2011Lee et al, , 2012.…”

“…A common way to validate the CT scanner model is through comparisons between experimentally measured and simulated computed tomography dose index (CTDI) values (Jarry et al, 2003;Staton et al, 2006;Gu et al, 2009;Lee et al, 2011Lee et al, , 2012. For this purpose, a set of CTDI data was simulated for head and body CTDI phantoms with diameters of 16 and 32 cm, respectively, and compared with the measured CTDI values reported by Lee et al (2012), under the same radiation exposure condition.…”

“…The second cylinder with a diameter of 10.2 mm defined the chamber wall which is C552 air-equivalent material with a density of 1.76 g.cm −3 . The third cylinder with a diameter of 13.7 mm defined a build-up cap, which was modeled as polyacetal plastic with a density of 1.43 g.cm −3 (Lee et al, 2011).…”

“…It was reported that Monte Carlo simulation is the most reliable way to obtain accurate values of dose 44 P. Akhlaghi et al: Radioprotection 50(1), 43-54 (2015) under CT imaging (Caon et al, 2000;DeMarco et al, 2005;Lee et al, 2011) because the pediatric bodies lying on a CT table and X-ray beam are fully simulated, so that with an appropriate simulation model, the results are solid.…”

In vitro dose measurements in a human cadaver with abdomen/pelvis CT scans

“…With the advances in both computational phantoms and modeling of CT systems, several research groups have worked on more patientspecific CT dose estimation methods. [20][21][22][23][24][25][26] One such software is the VirtualDose (www.virtual-dose.com) that employs a library of adult and pediatric patient phantoms for organ dose reporting.…”