Toward Pulse by Pulse Dosimetry Using an SC CVD Diamond Detector

Solid state detectors with nanosecond response times to incoming radiation are increasingly present at the forefront of radiotherapy dosimetry research. The fast response time of materials, such as diamond, allow pulse by pulse dosimetry. There is a trend in radiotherapy to move toward shorter treatments, using fewer but more intense pulses with varying pulse rates and intensities. This makes the possibility of measuring individual pulses very attractive and would allow intervention during the treatment and not just afterwards. Here, an analogue front end has been developed and combined with a chemical vapor deposition diamond detector to provide real time, pulse by pulse beam intensity measurements. The front end design is discussed and the experimental results obtained using a medical linear accelerator are presented. The results show that the device is capable of pulse by pulse beam intensity measurements up to pulse rates well above 1 kHz. The system performs so well that its variations are negligible compared to the pulse to pulse intensity variations. The dosimetric performance of our system was compared to a commercially available, integrating diamond detector, the microDiamond by PTW. The dose and dose-rate linearity of our system is comparable with the one of the microDiamond and has the additional advantage of being able to measure the deposited dose per pulse.