Brief introduction to isocenter deviation detection using MatriXX with improved resolution(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2018年第1期
- Page:
- 19-24
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Brief introduction to isocenter deviation detection using MatriXX with improved resolution
- Author(s):
- YI Haiyun; XIA Bing; YAO Lei; ZHANG Shuo
- Department of Radiation Oncology, the First Hospital of China Medical University, Shenyang 110001, China
- Keywords:
- ; Keywords: isocenter; deviation; MatriXX; quality assurance; dose distribution
- PACS:
- R815.6
- DOI:
- DOI:10.3969/j.issn.1005-202X.2018.01.005
- Abstract:
- Abstract: Objective To introduce a method for detecting the collimator isocenter deviation with high-resolution MatriXX by taking the detection of collimator isocenter deviation in X direction as an example. Methods Firstly, we ensured that the leaf bank of MLC was rotational symmetry by the central axis of collimator and that the distance of MatriXX center to isocenter was known, and then the angles of gantry and collimator were set to 0°. The dose distribution curve in an irradiation field of 5 cm×5 cm, 100 MU, was obtained after the linear accelerator was moved 1 mm at a time along X axis. The treatment couch was moved 7 times and a total of 8 measurements were obtained. All the measurements were superimposed to generate a "finer" profile, and the dose distribution curve with gantry 0°, collimator 0°, irradiation field of 5 cm×5 cm, 100 MU (G0C0) was obtained by MatriXX with an X-direction resolution of 1 mm. The same method was used to measure the dose distribution curve with gantry 180°, collimator 0°, irradiation field of 5 cm×5 cm, 100 MU (G180C0). Finally, we applied OmniPro I’mRT software to compare and analyze the profiles of G0C0 and G180C0 for obtaining the deviation of isocenter in X direction. Results The isocenter deviation was 1.8 mm. Conclusion MatriXX with an improved resolution is able to detect isocenter deviation. The isocenter deviation leads to the deviation of dose to patients, which can be avoided by adjusting the leaf bank of Elekta Synergy MLC to achieve the rotational symmetry by the central axis of gantry, and setting the angle of collimator and couch to 0°. The isocenter deviation results in a large planar dose deviation in irradiation fields with gantry angles closer to 90° and 270°, therefore, it’s not recommended to select the irradiation fields with gantry angles closer to 90° and 270°, and use MatriXX or other planar detectors to validate the patient plan with fields gantry angle centered around 90° and 270°.
Last Update: 2018-01-25