| LI Qi-xin,BAI Peng-gang,ZHANG Xiu-chun,CHEN Kai-qiang,JIANG Si-si.Angular dose dependency of MatriXX and its calibration[J].Chinese Journal of Radiological Medicine and Protection,2011,31(2):229-232 |
| Angular dose dependency of MatriXX and its calibration |
| Received:April 01, 2010 |
| DOI：10.3760/cma.j.issn.0254-5098.2011.02.030 |
| KeyWords:MatriXX Angular dependency Calibration |
| FundProject: |
| Author Name | Affiliation | | LI Qi-xin | Department of Radiation Oncology, Fujian Tumor Hospital, Fuzhou 350014, China | | BAI Peng-gang | Department of Radiation Oncology, Fujian Tumor Hospital, Fuzhou 350014, China | | ZHANG Xiu-chun | Department of Radiation Oncology, Fujian Tumor Hospital, Fuzhou 350014, China | | CHEN Kai-qiang | Department of Radiation Oncology, Fujian Tumor Hospital, Fuzhou 350014, China | | JIANG Si-si | Department of Radiation Oncology, Fujian Tumor Hospital, Fuzhou 350014, China |
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| Abstract:: |
| Objective To characterize angular dependency of MatriXX and develop a method for its calibration in order to verify treatment plan with original gantry angles. Methods Absolute dose calibration was carried with thimble ionization chamber on the linear accelerator, so as to make sure 1 MU=1 cGy at the depth of maximum dose (dmax). A MatriXX was put into a Mutlicube phantom, and the ionization chamber matrix was calibrated with absolute dose. In order to determine a correction factor CF as a function of gantry angle θ,open beam fields of 10 cm × 10 cm size were irradiated for gantry angles θ=0°-180° (every 5°) and every 1° for lateral angles θ in the range of 85°–95°. CF was defined as the ratio of the dose measured with ionization chamber and the dose from MatriXX. Results Relatively large discrepancies in response to posterior vs. anterior fields for MatriXX detectors (up to 10%) were found during the experiment and relatively large variability of response as a function of gantry angle. The pass rate of treatment plan in lateral beams was lower than that of other beams. The isodose distribution of corrected MatriXX matched well with the outcome from the treatment planning system. Conclusions The angular dose dependency of MatriXX must be considered when it is used to verify the treatment plan with original gantry angles. |
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