International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Dec 2001
Dose conformity of gamma knife radiosurgery and risk factors for complications.
To quantitatively evaluate dose conformity achieved using Gamma Knife radiosurgery, compare results with those reported in the literature, and evaluate risk factors for complications. ⋯ Gamma Knife radiosurgery achieves much more conformal dose distributions than those reported for conventional linac radiosurgery and somewhat more conformal dose distributions than sophisticated linac radiosurgery techniques. Larger target, nontarget, or prescription volumes are associated with increased risk of toxicity.
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Int. J. Radiat. Oncol. Biol. Phys. · Dec 2001
The reproducibility of organ position using active breathing control (ABC) during liver radiotherapy.
To evaluate the intrafraction and interfraction reproducibility of liver immobilization using active breathing control (ABC). ⋯ Radiotherapy using ABC for patients with intrahepatic cancer is feasible, with good intrafraction reproducibility of liver position using ABC. However, the interfraction reproducibility of organ position with ABC suggests the need for daily on-line imaging and repositioning if treatment margins smaller than those required for free breathing are a goal.
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Int. J. Radiat. Oncol. Biol. Phys. · Dec 2001
The position and volume of the small bowel during adjuvant radiation therapy for rectal cancer.
The rate of small bowel toxicity from adjuvant pelvic radiation therapy (RT) for rectal cancer has been reported to be lower for patients treated preoperatively (Preop). This was probably due to a lesser volume of irradiated small bowel; however, studies of postoperative treatment reported that patients with an abdominoperineal resection (APR), who likely have the largest volume of small bowel in the pelvis, had less acute and chronic toxicity than those with a low anterior resection (LAR). In this study, three-dimensional treatment planning techniques were used to characterize the position and volume of small bowel in the pelvis and compare these to repeat studies obtained during the typical 5-week course of treatment to attempt to explain the above observations. ⋯ Because treatment planning CT scans can detect small bowel that does not contain contrast, they may be more accurate than the traditional small bowel series. The Preop patients had significantly less pelvic small bowel supporting the clinical observation of better tolerance to therapy. The higher small bowel toxicity reported for LAR vs. APR patients may be explained by the greater variability of both the position and volume of the small bowel in the posterior pelvis for LAR patients. This finding suggests that a single planning study may not be accurate for the block design used for boost treatment of LAR patients. Bladder-filling techniques were useful for Preop and LAR but not APR patients, and decreased in benefit over time. This study suggested that treatment planning CT scans were more useful than a small bowel series and that more than one treatment planning CT may be obtained in any patient receiving > 45 Gy for rectal cancer. However, further research will be necessary to determine the optimal timing and total number of repeat studies.