Dosimetric effects of quality assurance-related setup errors in passive proton therapy for prostate cancer with and without a hydrogel spacer

Dosimetric effects of quality assurance-related setup errors in passive proton therapy for prostate cancer with and without a hydrogel spacer

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 spacer...

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Bibliographic Details
Published in:Radiological physics and technology Vol. 14; no. 3; pp. 328 - 335
Main Authors: Omi, Yuta, Yasui, Keisuke, Shimomura, Akira, Muramatsu, Rie, Iwata, Hiromitsu, Ogino, Hiroyuki, Furukawa, Akari, Hayashi, Naoki
Format: Journal Article
Language:English
Published: Singapore Springer Singapore 01-09-2021
Springer Nature B.V
Subjects:
Collimators
Computed tomography
Hydrogels
Imaging
Medical and Radiation Physics
Medicine
Medicine & Public Health
Nuclear Medicine
Position errors
Prostate cancer
Protons
Quality assurance
Quality control
Radiation therapy
Radiology
Radiotherapy
Range errors
Rectum
Setup error
Quality assurance
Proton therapy
Prostate cancer
Spacer
Robust
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Summary: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 ± 1 mm, setup error ± 1 mm for three directions, and multileaf collimator (MLC) position error ± 1 mm. 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 ± 1.3 mm without the spacer and 12.9 ± 2.9 mm with the spacer ( P  < 0.001). The mean rectum V 53.5 GyE , V 50 GyE , and V 34.5 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 V 53.5 GyE , V 50 GyE , and V 34.5 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.
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ISSN:1865-0333
1865-0341
DOI:10.1007/s12194-021-00632-4