Abstract
The purpose of this study was to evaluate the effect of quality assurance (QA)-related setup errors in passive proton therapy for prostate cancer with and without a hydrogel spacer. We used 20 typical computed tomography (CT) images of prostate cancer: 10 patients with and 10 patients without spacers. The following 12 model errors were assumed: output error ± 2%, range error ± 1mm, setup error ± 1mm for three directions, and multileaf collimator (MLC) position error ± 1mm. We created verification plans with model errors and compared the prostate-rectal (PR) distance and dose indices with and without the spacer. The mean PR distance at the isocenter was 1.1 ± 1.3mm without the spacer and 12.9 ± 2.9mm with the spacer (P < 0.001). The mean rectum V53.5 GyE, V50 GyE, and V34.5 GyE in the original plan were 2.3%, 4.1%, and 12.1% without the spacer and 0.1%, 0.4%, and 3.3% with the spacer (P = 0.0011, < 0.001, and < 0.001). The effects of the range and lateral setup errors were small; however, the effects of the vertical/long setup and MLC error were significant in the cases without the spacer. The means of the maximum absolute change from original plans across all scenarios in the rectum V53.5 GyE, V50 GyE, and V34.5 GyE were 1.3%, 1.5%, and 2.3% without the spacer, and 0.2%, 0.4%, and 1.3% with the spacer (P < 0.001, < 0.001, and = 0.0019). This study indicated that spacer injections were also effective in reducing the change in the rectal dose due to setup errors.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.