Effects of systemic integrated orientation frame on absorbed dose of target areas in radiotherapy
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《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2018年第7期
- Page:
- 785-789
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Effects of systemic integrated orientation frame on absorbed dose of target areas in radiotherapy
- Author(s):
- HONG Jun; SHAN Husheng; ZHOU Yufeng
- Department of Radiotherapy, the 82nd Hospital of the PLA, Huai’an 223001, China
- Keywords:
- ; Keywords: integrated orientation frame; radiotherapy; attenuation rate; absorbed dose
- PACS:
- R811.1
- DOI:
- DOI:10.3969/j.issn.1005-202X.2018.07.009
- Abstract:
- Abstract: Objective To discuss the effects of YC-TQ-Ⅱ systemic integrated orientation frame on the absorbed dose of target areas in radiotherapy. Methods A solid water phantom of 30 cm×30 cm×15 cm was fixed on the body center axis of systemic integrated orientation frame for CT scanning. Then the obtained CT images were imported into XiO TPS, and the solid water phantom, target areas and the structure of systemic integrated orientation frame were sketched. A 10 cm×10 cm and 100 MU radiation field with different energies at the center of ionization chamber was added at regular angels, which starting at 0°. Considering the effects of the size of high-density material on the angle, a value was measured at every 1° in the following angle ranges, namely 61°-79°, 101°-119°, 241°-259°, 281°-299°, and a value was measured at every 10° in other angle ranges (0°-60°, 80°-100°, 120°-240°, 260°-280°, 300°-350°). According to symmetry, the attenuation rate was calculated when high-energy X-ray went through systemic integrated orientation frame. Then the accuracy of XiO TPS was verified by the measurement of UNDOSE dosimeter under the same conditions on medical linear accelerator. Finally, the changes of absorbed dose in three-dimensional conformal radiotherapy were analyzed on XiO TPS with or without systemic integrated orientation frame. Results The maximum attenuation rate of high-energy X-ray caused by systemic integrated orientation frame were 13.0% (6 MV), 11.4% (15 MV), and the calculated output of XiO TPS was in good agreement with measured value, with a maximum deviation of 0.6% (15 MV). After adding systemic integrated orientation frame, the D95% of target areas decreased from 6 000 cGy to 5 304 cGy (6 MV), 5 484 cGy (15 MV). The homogeneity index of target areas increased from 0.091 (6 MV), 0.104 (15 MV) to 0.195 (6 MV), 0.175 (15 MV). The isodoses lined of 6 000, 5 500 cGy of target areas closing to body frame were shifted up obviously, and the shift of 6 MV was more obviously than that of 15 MV. Conclusion The high-density material of YC-TQ-Ⅱ systemic integrated orientation frame can significantly lower the absorbed dose of target areas in radiotherapy, and the attenuation rate of high-energy X-ray caused by the material must be considered and corrected.
Last Update: 2018-07-24