A reliable, accurate and in-vivo dosimetry system for measuring the radiation dose and profiling the X-ray beam during radiotherapy is reported. Its dynamic range is investigated using an accurately controlled pulsed light emitting diode (LED) system. Highly resolved temporal analog and digital signals were captured from the analog and digital outputs of a multi-pixel photon counter (MPPC) detector when exposed to the LED system. The photon distribution of a low intensity pulsed LED light source was observed and is found to obey a Poisson distribution with changing light intensity. The average number of photons was obtained using the digital MPPC output signals which in turn allowed the appropriate intensity of the light source to be determined for the correct light exposure conditions for the detector. The average analog output voltage over a single 3 μs pulse is determined to indicate the intensity of the detected light. The MPPC detector output analog signal is limited to a narrow range (0.6 V–1.4 V) to ensure adequate signal detection level (the lower limit) and prevention of entry into saturation (the upper limit) which also corresponds to a digital output signal range (in counts). An average photon number range of 3–7 for the digital output signal is established, which leads to the establishment of a unique and constant photon number to average output voltage ratio of 4.64 ± 0.10. Experimental results show that the establishment of this ratio is significant as adherence to it ensures the correct exposure conditions of the MPPC and speeds up the measurement cycle in the clinical setting.

报道了一种可靠，准确和体内的剂量学系统，用于在放射治疗期间测量辐射剂量和对X射线束进行分析。使用精确控制的脉冲发光二极管（LED）系统研究了其动态范围。当暴露于LED系统时，可从多像素光子计数器（MPPC）检测器的模拟和数字输出中捕获高度解析的时间模拟和数字信号。观察到低强度脉冲LED光源的光子分布，发现其随光强度的变化服从泊松分布。使用数字MPPC输出信号可以获得光子的平均数量，该信号又可以为检测器的正确曝光条件确定合适的光源强度。确定单个3μs脉冲上的平均模拟输出电压，以指示检测到的光的强度。MPPC检测器的输出模拟信号被限制在一个狭窄的范围内（0.6 V–1.4 V），以确保足够的信号检测电平（下限）并防止进入饱和状态（上限），这也对应于数字输出信号范围（以计数为单位）。数字输出信号的平均光子数范围为3–7，这导致建立唯一且恒定的光子数与平均输出电压之比为4.64±0.10。实验结果表明，该比率的建立非常重要，因为遵守该比率可确保MPPC的正确暴露条件并在临床环境中加快测量周期。