研究目的
To develop a novel real-time optical fibre X-Ray dosimeter for monitoring the radiation pulses delivered from a clinical linear accelerator (Linac), capable of measuring low doses of ionising X-ray radiation in real time.
研究成果
The novel optical fibre based sensor is capable of accurate real time dose measurement for a wide range of operating conditions in clinical EBRT. It has demonstrated highly linear measurement (R2 of 0.9995) when calibrated against simultaneous measurements of dose recorded using a co-located IC for a wide range of dose rates (100 to 600 MU/min).
研究不足
The current resolution (lowest detectable level) of the sensor is 1 MU. The limited sampling period (limited by the gate time of the MPPC to 0.1 ms) may contribute to fluctuations in amplitude observed in the micro-pulses.
1：Experimental Design and Method Selection:
The sensor design involves coating the tip of a PMMA fibre with scintillation doped epoxy, modified to allow for improved coupling of the radioluminescence signal. The end of the 1-mm PMMA fibre optic core was micro-machined to create a small hole, filled with a mixture of epoxy and the scintillating material.
2：Sample Selection and Data Sources:
The scintillating material, Gadolinium Oxysulphide activated with Terbium (Gd2O2S:Tb), fluoresces when exposed to ionising radiation (X-Rays).
3：List of Experimental Equipment and Materials:
The visible optical signal generated by the scintillator propagates to the distal end of the optical fibre (30 m from the point of measurement) at which point it was detected using a Hamamatsu Multi-Pixel Photon Counter, MPPC C11208-01, APD array that was thermoelectrically cooled to allow for low light intensity detection.
4：Experimental Procedures and Operational Workflow:
All measurements were recorded on a Varian IX3937 linac at the External Radiation Beam Therapy Clinic of the First Affiliated Hospital of the Harbin Medical University, Harbin, China.
5：Data Analysis Methods:
Special software was written (in C++) to control the device, as the minimum gate time allowed by the manufacturer’s proprietary software was 1 ms, which does not allow adequate time resolution to detect the individual pulses of the linac beam.
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