New idea for determining the optimal number of measurements in absorbed dose-to-water measurement of high-energy photon beam

This study presents a new idea for estimating the number of measurements required for determining the uncertainty in obtaining the desired water absorbed dose using the variation obtained from multicenter absorbed dose measurement data. The number of dose measurements depends on the performance of each linear accelerator (Linac) tested and the dosimetry equipment and procedure used. However, optimising the number of data collected for the absorbed dose to water has been inadequately reported. Using the absorbed dose measurement data collected 10 times as a reference value, we will compare the changes in the variation of the measurement results caused by the difference in the number of repeated measurements of the absorbed dose. The number of measurements is determined statistically such that this variation would be smaller than the change in absorbed dose. Thus, we can determine the optimum number of measurements suitable for the variability of each Linac. (authors)