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Verification of a novel method for tube voltage constancy measurement of orthovoltage x‐ray irradiators
Author(s) -
Wang Chu,
Belley Matthew D.,
Chao Nelson J.,
Dewhirst Mark W.,
Yoshizumi Terry
Publication year - 2014
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4889778
Subject(s) - voltage , quality assurance , calibration , high voltage , nuclear engineering , dosimetry , beam (structure) , materials science , filtration (mathematics) , nuclear medicine , optics , physics , electrical engineering , engineering , mathematics , medicine , operations management , external quality assessment , statistics , quantum mechanics
Purpose: For orthovoltage x‐ray irradiators, the tube voltage is one of the most fundamental system parameters as this directly relates to the dosimetry in radiation biology studies; however, to the best of our knowledge, there is no commercial portable quality assurance (QA) tool to directly test the constancy of the tube voltage greater than 160 kV. The purpose of this study is to establish the Beam Quality Index (BQI), a quantity strongly correlated to the tube voltage, as an alternative parameter for the verification of the tube voltage as part of the QA program of orthovoltage x‐ray irradiators. Methods: A multipurpose QA meter and its associated data acquisition software were used to customize the measurement parameters to measure the BQI and collect its time‐plot. BQI measurements were performed at 320 kV with four filtration levels on three orthovoltage x‐ray irradiators of the same model, one of which had been recently energy‐calibrated at the factory. Results: For each of the four filtration levels, the measured BQI values were in good agreement (<5%) between the three irradiators. BQI showed filtration‐specificity, possibly due to the difference in beam quality. Conclusions: The BQI has been verified as a feasible alternative for monitoring the constancy of the tube voltage for orthovoltage irradiators. The time‐plot of BQI offers information on the behavior of beam energy at different phases of the irradiation time line. In addition, this would provide power supply performance characteristics from initial ramp‐up to plateau, and finally, the sharp drop‐off at the end of the exposure.