ABSTRACT
PURPOSE: In radiotherapy for cervix cancer, both 3-dimensioal radiotherapy (3D-CRT) and intensity-modulated radiation therapy (IMRT) could reduce the dose to the small bowel (SB), while the small bowel displacement system (SBDS) could reduce the SB volume in the pelvic cavity. To evaluate the effect of the SBDS on the dose to the SB in 3D-CRT and IMRT plans, 3D-CRT and IMRT plans, with or without SBDS, were compared. MATERIALS AND MEHTODS: Ten consecutive uterine cervix cancer patients, receiving curative radiotherapy, were accrued. Ten pairs of computerized tomography (CT) scans were obtained in the prone position, with or without SBDS, which consisted of a Styrofoam compression device and an individualized custom-made abdominal immobilization device. Both 3D-CRT, using the 4-field box technique, and IMRT plans, with 7 portals of 15 MV X-ray, were generated for each CT image, and prescribed 50 Gy (25 fractions) to the isocenter. For the SB, the volume change due to the SBDS and the DVHs of the four different plans were analyzed using paired t-tests. RESULTS: The SBDS significantly reduced the mean SB volume from 522 to 262 cm3 (49.8% reduction). The SB volumes that received a dose of 10~50 Gy were significantly reduced in 3D-CRT (65~80% reduction) and IMRT plans (54~67% reduction) using the SBDS. When the SB volumes that received 20~50 Gy were compared between the 3D-CRT and IMRT plans, those of the IMRT without the SBDS were significantly less, by 6~7%, than those for the 3D-CRT without the SBDS, but the volume difference was less than 1% when using the SBDS. CONCLUSION: The SBDS reduced the radiation dose to the SB in both the 3D-CRT and IMRT plans, so could reduce the radiation injury of the SB.
Subject(s)
Female , Humans , Cervix Uteri , Immobilization , Prone Position , Radiation Injuries , Radiotherapy , Uterine Cervical NeoplasmsABSTRACT
PURPOSE: Authors designed a customized Small Bowel Displacement System (SBDS) to displace the small bowel from the pelvic radiation fields and minimize treatment-related bowel morbidities. METHODS AND MATERIALS: From August 1995 to May 1996, 55 consecutive patients who received pelvic radiation therapy with the SBDS were included in this study. The SBDS consists of a customized styrofoam compression device which can displace the small bowel from the radiation fields and an individualized immobilization abdominal board for easy daily setup in prone position. After opacifying the small bowel with Barium , the patients were laid prone and posterior-anterior (PA) and lateral (LAT) simulation films were taken with and without the SBDS. The areas of the small bowel included in the radiation fields with and without the SBDS were compared. RESULTS: Using the SBDS, the mean small bowel area was reduced by 59% on PA and 51% on LAT films (P=0.0001). In six patients (6/55, 11%), it was possible that no small bowel was included within the treatment fields. The mean upward displacement of the most caudal small bowel was 4.8 cm using the SBDS. Only 15% (8/55) of patients treated with the SBDS manifested diarrhea requiring medication. CONCLUSION: The SBDS is a novel method that can be used to displace the small bowel away from the treatment portal effectively and reduce the radiation therapy morbidities. Compliance with setup is excellent when the SBDS is used.