The aim of this study is to investigate the delivery accuracy of intensity-modulated radiation therapy (IMRT) plans in the two-headed mode of the ViewRay$^{TM}$ system in comparison with that of the normal operation treatment plan of the machine. For this study, a total of eight IMRT plan...
The aim of this study is to investigate the delivery accuracy of intensity-modulated radiation therapy (IMRT) plans in the two-headed mode of the ViewRay$^{TM}$ system in comparison with that of the normal operation treatment plan of the machine. For this study, a total of eight IMRT plans and corresponding verification plans were generated (four head and neck, two liver, and two prostate IMRT plans). The delivered dose distributions were measured using ArcCHECK$^{TM}$ with the insertion of an ionization chamber. We measured the delivered dose distributions in three-headed mode (normal operation of the machine), two-headed mode with head 1 disabled, two-headed mode with head 2 disabled, and two-headed mode with head 3 disabled. Therefore, a total of four measurements were performed for each IMRT plan. The global gamma passing rates (3%/3 mm) in three-headed mode, head 1 disabled, head 2 disabled, and head 3 disabled were $99.9{\pm}0.1%$, $99.8{\pm}0.3%$, $99.6{\pm}0.7%$, and $99.7{\pm}0.4%$, respectively. The difference in the gamma passing rates of the three- and two-headed modes was insignificant. With 2%/2 mm, the rates were $96.6{\pm}3.6%$, $97.2{\pm}3.5%$, $95.7{\pm}6.2%$, and $95.5{\pm}4.3%$, respectively. Between three-headed mode and head 3 disabled, a statistically significant difference was observed with a p-value of 0.02; however, the difference was minimal (1.1%). The chamber readings showed differences of approximately 1% between three- and two-headed modes, which were minimal. Therefore, the treatment plan delivery in the two-headed mode of the ViewRay$^{TM}$ system seems accurate and robust.
The aim of this study is to investigate the delivery accuracy of intensity-modulated radiation therapy (IMRT) plans in the two-headed mode of the ViewRay$^{TM}$ system in comparison with that of the normal operation treatment plan of the machine. For this study, a total of eight IMRT plans and corresponding verification plans were generated (four head and neck, two liver, and two prostate IMRT plans). The delivered dose distributions were measured using ArcCHECK$^{TM}$ with the insertion of an ionization chamber. We measured the delivered dose distributions in three-headed mode (normal operation of the machine), two-headed mode with head 1 disabled, two-headed mode with head 2 disabled, and two-headed mode with head 3 disabled. Therefore, a total of four measurements were performed for each IMRT plan. The global gamma passing rates (3%/3 mm) in three-headed mode, head 1 disabled, head 2 disabled, and head 3 disabled were $99.9{\pm}0.1%$, $99.8{\pm}0.3%$, $99.6{\pm}0.7%$, and $99.7{\pm}0.4%$, respectively. The difference in the gamma passing rates of the three- and two-headed modes was insignificant. With 2%/2 mm, the rates were $96.6{\pm}3.6%$, $97.2{\pm}3.5%$, $95.7{\pm}6.2%$, and $95.5{\pm}4.3%$, respectively. Between three-headed mode and head 3 disabled, a statistically significant difference was observed with a p-value of 0.02; however, the difference was minimal (1.1%). The chamber readings showed differences of approximately 1% between three- and two-headed modes, which were minimal. Therefore, the treatment plan delivery in the two-headed mode of the ViewRay$^{TM}$ system seems accurate and robust.
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제안 방법
, Cleveland, OH, USA). After treatment planning, a verification plan for each treatment plan was generated with the CT image set of the ArcCHECKTM (Sun Nuclear Corporation, Melbourne, FL, USA) in the MRIdianTM system. The reference dose distributions were calculated in the MRIdianTM system.
We verified the IMRT plan delivery accuracy in the two-headed mode of the ViewRayTM system by gamma evaluation with gamma criteria of 2%/2 mm and 3%/3 mm. The results showed highly accurate beam delivery performance of two-headed mode in comparison with three-headed mode.
대상 데이터
In this study, the delivery accuracy of the two-headed mode of the ViewRayTM system was verified with a total of eight IMRT plans. As shown in the results, gamma passing rates were lowest when head 3 was disabled, while the deviation in the chamber measurements from those of normal operation were the highest when head 1 was disabled.
이론/모형
8,10) The grid size of the dose calculation was 3 mm. The dose calculation algorithm was the Monte Carlo algorithm developed by the manufacturer (ViewRay Inc., Cleveland, OH, USA). After treatment planning, a verification plan for each treatment plan was generated with the CT image set of the ArcCHECKTM (Sun Nuclear Corporation, Melbourne, FL, USA) in the MRIdianTM system.
성능/효과
The average values of the gamma passing rates with gamma criteria of 2%/2 mm and 3%/3 mm for the three-headed mode as well as two-headed modes are shown in Table 1. In the case of gamma passing rates with 2%/2 mm, two-headed mode with head 1 disabled showed the highest gamma passing rate (97.2%); however, the difference was minimal, being less than approximately 1%. With the gamma criterion of 3%/3 mm, the gamma passing rate of three-headed mode was the highest (99.
Although these were inconsistent results, the differences in both gamma passing rates and chamber measurements between three- and two-headed modes were minimal. Despite the tight gamma criterion of 2%/2 mm, there was no considerable difference in the gamma passing rates between three-headed mode and two-headed modes, which showed approximately 1% difference. The results of the ionization chamber also showed an accurate delivery of the treatment plan in two-headed mode.
4%. No statistically significant difference was observed in the gamma passing rates between three-headed mode and two-headed mode, except in the gamma passing rates with 2%/2 mm of the two-headed mode with head 3 disabled (96.6% vs. 95.5% with p=0.020). However, the difference in the gamma passing rates between three-headed mode and the head 3 disabled was only 1.
system by gamma evaluation with gamma criteria of 2%/2 mm and 3%/3 mm. The results showed highly accurate beam delivery performance of two-headed mode in comparison with three-headed mode. To guarantee and maintain the delivery accuracy in two-headed mode, periodic quality assurance and verification should be performed.
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