Investigation on absorbed dose determination at the calibration point of X-rays from electron linear accelerators of 34 hospitals in Tokyo area

Abstract

The method and accuracy of absorbed dose determination have been investigated at 34 hospitals in Tokyo and its neighboring area. The measurement was made for a field of 10 × 10cm^-2 at the calibration point of X-rays (10,6 or 4MV) from a linear accelerator, using the reference dosemeter of each hospital, and the RAMTEC 1000 dosemeter and a water phantom, which were prepared for use in the present investigation. The obtained data were converted to the reference point absorbed dose per dose monitor unit for intercomparison.
The results are given in te r ms of the percentage deviation of absorbed dose determined according to the procedure of each hospital from that obtained with the RAMTEC 1000 dosemeter.
(1) The deviation without the corrections was within ± 1% for 17 hospitals (50%) a nd within ±2% for 30 hospitals (88%).
(2) With the corre ctions for ion recombination and absorbed dose conversion factor according to the JARP protocal,18 hospitals (53%) resulted in a deviation of ± 1% or less and 32 (94%) in ±2%or less.