Feygelman V, Opp D, Javedan K, Saini AJ, Zhang G. Evaluation of a 3D diode array dosimeter for helical tomotherapy delivery QA.
Med Dosim 2010;
35:324-9. [PMID:
20097061 DOI:
10.1016/j.meddos.2009.10.007]
[Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2009] [Revised: 10/12/2009] [Accepted: 10/26/2009] [Indexed: 10/19/2022]
Abstract
The Delta4 biplanar diode array dosimeter was validated for helical tomotherapy delivery QA. The basic detector characteristics were found to be satisfactory in terms of short-term reproducibility (0.1%), linearity (<0.1%), dose rate dependence (0.4%), and absolute calibration accuracy (0.4% in the center of the phantom compared with the independently calibrated diode). Relative calibration of the arrays was verified by comparison with film and by rotating the detector 180°. The dosimeter response to rotational irradiation changed by no more than 0.2% when one of the detector boards was replaced by the homogeneous phantom material. The daily output correction factor can be derived from a Delta4 measurement in a uniform cylindrical field. The γ(3%, 3 mm) passing rate (absolute dose) was above 90% for all 9 evaluated clinical plans, and above 96% for all but one. The mean passing rate was 97 ± 2.7%. The plans varied in modulation factor, pitch, and calculation grid size. For best results, the phantom needs to be aligned carefully, preferably by megavoltage computed tomography imaging.
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