Impact of changes in body contours on radiation therapy dose distribution after uterine cervical cancer surgery
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ORIGINAL ARTICLE
Impact of changes in body contours on radiation therapy dose distribution after uterine cervical cancer surgery Motoharu Sasaki1 · Hitoshi Ikushima1 Received: 15 April 2020 / Accepted: 21 June 2020 © Japan Radiological Society 2020
Abstract Purpose Patients receiving postoperative irradiation for uterine cervical cancer might not be able to eat during radiation therapy because of the effects of concurrent chemo-radiotherapy; this may lead to changes in the patient’s body shape during treatment. When performing image-guided radiotherapy, it is necessary to determine immediately whether treatment can be performed on the day or whether re-planning is required. The purpose of this study was to determine indicators for re-planning by examining the effects of changing body contours on radiation therapy dose. Materials and methods The original body contour was reduced by 1 cm in the front portion (structure-set 1). Based on the original dose distribution, the dose recalculation was performed with a structure set created using the body contour of structure-set 1. The difference between the original and recalculated dose distributions of structure-set 1 was evaluated through gamma analysis (GA). Result In the GA results for dose distribution obtained via recalculation with structure-set 1, a pass rate of 90% or more was obtained for a criterion of 2 mm/2% in all cases. Conclusions The results suggest that dose re-planning is rarely required when the body shape is reduced by only 1 cm in the front. Keywords Body shape change · After uterine cervical cancer surgery · VMAT
Introduction In recent years, high-precision radiation therapy techniques such as intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) have been widely used as alternatives to three-dimensional conformal radiation therapy (3D-CRT) [1–6]. Furthermore, compared to IMRT, the use of VMAT has increased even further because of its advantages. Specifically, when compared with IMRT, VMAT yields equal or better dose distribution accuracy in addition to achieving shorter irradiation times and requiring fewer monitor units (MUs) [7–9]. VMAT is increasingly being used in actual clinical settings because of its short irradiation time and low MU requirement. In VMAT, the shape of the aperture of the * Motoharu Sasaki msasaki@tokushima‑u.ac.jp 1
Department of Therapeutic Radiology, Institute of Biomedical Sciences, Tokushima University Graduate School, 3‑18‑15 Kuramoto‑cho, Tokushima 770‑8503, Japan
multi-leaf collimator (MLC), the gantry speed, and the dose rate during irradiation are dynamically changed to achieve a three-dimensional conformal dose distribution [10]. Despite its advantages for cancer treatment, postoperative irradiation for uterine cervical cancer causes bowel obstruction (BO), which is a severe side effect of this treatment approach. In the past, studies have investigated the potential impact of IMRT on the BO rate in patients with gynecological malignancies who underwent pelvic radiati
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