open access

Vol 25, No 6 (2020)
Original research articles
Published online: 2020-11-01
Submitted: 2020-05-25
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The effect of rectal gas on dose distribution during prostate cancer treatment using full arc and partial arc Volumetric Modulated Arc Therapy (VMAT) treatment plans

Motoharu Sasaki, Hitoshi Ikushima, Akira Tsuzuki, Wataru Sugimoto
DOI: 10.1016/j.rpor.2020.09.013
·
Rep Pract Oncol Radiother 2020;25(6):974-980.

open access

Vol 25, No 6 (2020)
Original research articles
Published online: 2020-11-01
Submitted: 2020-05-25

Abstract

Background/Aim

In this study, we investigated the effect of rectal gas on the dose distribution of prostate cancer using a volumetric modulated arc therapy (VMAT) treatment planning.

Materials and Methods

The first is the original structure set, clinical target volume (CTV), the rectum, and the bladder used clinically. The second is a structure set (simulated gas structure set) in which the overlapping part of the rectum and PTV is overwritten with Hounsfield Unit −950 as gas. Full arc and limited gantry rotation angle with VMAT were the two arcs. The VMAT of the full arc was 181°–179° in the clockwise (CW) direction and 179°–181° in the counterclockwise (CCW) direction. Three partial arcs with a limited gantry rotation angle were created: 200°–160 °CW and 160°–200 °CCW; 220°–140 °CW and 140°–220 °CCW; and finally, 240°–120 °CW and 120°–240 °CCW. The evaluation items were dose difference, distance to agreement, and gamma analysis.

Result

In the CTV, the full arc was the treatment planning technique with the least effect of rectal gas. In the rectum, when the gantry rotation angle range was short, the pass rate tended to reduce for all evaluation indices. The bladder showed no characteristic change between the treatment planning techniques in any of the evaluation indices.

Conclusions

The VMAT treatment planning with the least effect on dose distribution caused by rectal gas was shown to be a full arc.

Abstract

Background/Aim

In this study, we investigated the effect of rectal gas on the dose distribution of prostate cancer using a volumetric modulated arc therapy (VMAT) treatment planning.

Materials and Methods

The first is the original structure set, clinical target volume (CTV), the rectum, and the bladder used clinically. The second is a structure set (simulated gas structure set) in which the overlapping part of the rectum and PTV is overwritten with Hounsfield Unit −950 as gas. Full arc and limited gantry rotation angle with VMAT were the two arcs. The VMAT of the full arc was 181°–179° in the clockwise (CW) direction and 179°–181° in the counterclockwise (CCW) direction. Three partial arcs with a limited gantry rotation angle were created: 200°–160 °CW and 160°–200 °CCW; 220°–140 °CW and 140°–220 °CCW; and finally, 240°–120 °CW and 120°–240 °CCW. The evaluation items were dose difference, distance to agreement, and gamma analysis.

Result

In the CTV, the full arc was the treatment planning technique with the least effect of rectal gas. In the rectum, when the gantry rotation angle range was short, the pass rate tended to reduce for all evaluation indices. The bladder showed no characteristic change between the treatment planning techniques in any of the evaluation indices.

Conclusions

The VMAT treatment planning with the least effect on dose distribution caused by rectal gas was shown to be a full arc.

Get Citation

Keywords

Volumetric modulated arc therapy; Gas; Dose distribution; Prostate cancer

About this article
Title

The effect of rectal gas on dose distribution during prostate cancer treatment using full arc and partial arc Volumetric Modulated Arc Therapy (VMAT) treatment plans

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 25, No 6 (2020)

Pages

974-980

Published online

2020-11-01

DOI

10.1016/j.rpor.2020.09.013

Bibliographic record

Rep Pract Oncol Radiother 2020;25(6):974-980.

Keywords

Volumetric modulated arc therapy
Gas
Dose distribution
Prostate cancer

Authors

Motoharu Sasaki
Hitoshi Ikushima
Akira Tsuzuki
Wataru Sugimoto

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