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JOURNAL NAME: International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, Vol.7 No.1, February 13, 2018
ABSTRACT: To measure integral doses in image-guided radiation therapy, we developed a disposable mini-substrate with a 1.0-μF condenser and a silicon X-ray diode (Si-XD). The Si-XD is a high-sensitivity photodiode selected for detecting X-rays. In the substrate with dimensions of 15 × 15 mm2, the initial charging voltage is 3.30 V, and the charging voltage is decreased by photocurrents flowing through the Si-XD during X-ray exposing. The condenser in the substrate is charged by a microcomputer dock, and the charging voltage is also measured using an analog to digital converter in the dock after exposing X-rays. The dock is connected to a personal computer through a USB cable, and integral doses are shown on the PC monitor. The doses were proportional to decreases in the charging voltage, and the calibrated doses corresponded well to those obtained using a readily available ionization chamber.