Patient organ doses from megavoltage computed tomography delivery with a helical tomotherapy unit using a general treatment planning system

Abstract The purpose of this study was to quantify actual patient organ doses from megavoltage computed tomography (MVCT) using an MVCT beam model of a helical tomotherapy unit in a general treatment planning system (TPS). Dosimetric parameters (percentage depth dose, lateral beam profile, and longi...

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Bibliographic Details
Published in:Journal of radiation research 2019-05, Vol.60 (3), p.401-411
Main Authors: Nagata, Hironori, Sugimoto, Satoru, Hongo, Hideyuki, Hashimoto, Harumitsu, Sato, Yuki, Kawabata, Toru, Watanabe, Hiroyuki, Inoue, Tatsuya, Usui, Keisuke, Kurokawa, Chie, Sasai, Keisuke
Format: Article
Language:English
Subjects:
CAT scans
Control
Diagnostic imaging
Ghosts
Health planning
Medical research
Methods
Radiation exposure
Regular Paper
Tomography
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Summary:Abstract The purpose of this study was to quantify actual patient organ doses from megavoltage computed tomography (MVCT) using an MVCT beam model of a helical tomotherapy unit in a general treatment planning system (TPS). Dosimetric parameters (percentage depth dose, lateral beam profile, and longitudinal beam profile) of the MVCT beam were measured using Gafchromic EBT3 films (ISP Corporation, Wayne, NJ, USA) and used for beam modeling in a Pinnacle3 TPS (Philips, Amsterdam, Netherlands); this TPS is widely used with linear accelerators. The created beam model was adjusted and validated by assessing point doses in a cylindrical phantom in static and helical beam plans with fine, normal and coarse pitches. Maximum doses delivered to important organs from MVCT delivery for five clinical cases were calculated using the created beam model. The difference (average ± one standard deviation for all evaluation points) between calculated and measured doses was −0.69 ± 1.20% in the static beam plan. In the helical beam plan, the differences were 1.83 ± 2.65%, 1.35 ± 5.94% and −0.66 ± 8.48% for fine, normal and coarse pitches, respectively. The average maximum additional dose to important organs from MVCT in clinical cases was 0.82% of the prescribed dose. In conclusion, we investigated a method for quantifying patient organ dose from MVCT delivery on helical tomotherapy using an MVCT beam model in a general TPS. This technique enables estimation of the patient-specific organ dose from MVCT delivery, without the need for additional equipment.
ISSN:0449-3060
1349-9157
DOI:10.1093/jrr/rrz005