Dose impact of rectal gas on prostatic IMRT and VMAT

Purpose: In this study, we compared the dose impact of the heterogeneity caused by rectal gas using two methods of treatment planning for intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT).
Materials and Methods: In addition to the structure set used for the standard treatment plan, we created a structure set for evaluation for each patient. The structure sets for evaluation that were created were transferred to the same iso-center as the respective treatment plans for IMRT and VMAT that were to become the standard. The values were then re-calculated.
Results: During the standard prostatic IMRT and VMAT treatment planning, all the subjects met the dose restrictions in place at our hospital. Dose restrictions were fulfilled in the treatment plans for evaluation, excluding those with a clinical target volume (CTV) of V100% and planning target volume (PTV) of D95 when the rectum was excluded. However, in treatment plans for evaluation, IMRT was shown to have a higher concordance rate with standard treatment plans than VMAT.
Conclusion: If rectal gas is present during either IMRT or VMAT, a dose decrease will occur in relation to CTV and PTV, suggesting that a plan does not eliminate adverse effects on organs at risk.

内容要旨・審査要旨・論文本文の公開:
内容要旨・審査要旨 : LID201605311003.pdf
論文本文 : LID201702161001.pdf
著者の申請により要約(2016-05-31公開)に替えて論文本文を公開(2017-02-16)
本論文は, 著者Motoharu Sasakiの学位論文として提出され, 学位審査・授与の対象となっている。
The final publication is available at Springer via https://doi.org/10.1007/s11604-015-0481-7