A fast and efficient method for measuring and reconstructing the megavoltage photon beam spectra of clinical machines used for treating cancer patients is developed using Compton scattering. The construction and characterization of a novel prototype of a Compton spectrometer are performed to measure the pulse height spectra (PHS) of radiotherapy machines in routine clinical practice. In this work, we measured the PHS for a Co-60 radiotherapy machine using our Compton spectrometer. Based on the measured PHS and by employing the response matrix that had been previously constructed for the spectrometry system with a deconvolution method, we recovered the clinical machine photon fluence spectra. First, the characterization of one NaI(Tl) detector was performed to obtain the response functions for the Compton spectrometer with the purpose of constructing the spectrometry system response matrix. Mechanical and radiation tests were performed to ensure and verify the functionality and operation of the spectrometry measurement system. Next, the PHS for an X-ray unit with energies of 70–100 kV was measured at a Compton angle of 90°to obtain the response of the spectrometer at these energies. Finally, the PHS for a Theratron-780 Co-60 clinical machine at different Compton angles was measured, and the corresponding photon fluence spectra were recovered. The results for the fluence spectra of the Theratron-780 show two well-defined peaks of 1173 and 1332 keV corresponding to the Co-60 source. The recovered spectra show good correlation with the spectra obtained by Monte Carlo simulation and with the spectra recovered for a standard Co-60 calibration source used as benchmarks in the corresponding megavoltage range. Our designed and built Compton spectrometer can be used in the clinical routine to measure and reconstruct megavoltage photon beam spectra for clinical machines.

利用康普顿散射技术开发了一种快速有效的方法，用于测量和重建用于治疗癌症患者的临床机器的兆伏光子束光谱。在常规临床实践中，对康普顿光谱仪的新型原型进行了构造和表征，以测量放射治疗机的脉冲高度谱（PHS）。在这项工作中，我们使用康普顿光谱仪测量了Co-60放射治疗机的PHS。基于测得的PHS并通过使用反卷积方法使用先前为光谱系统构建的响应矩阵，我们恢复了临床机器光子注量光谱。第一，为了构造光谱系统响应矩阵，对一个NaI（Tl）检测器进行表征以获得康普顿光谱仪的响应函数。进行了机械和辐射测试，以确保和验证光谱测量系统的功能和操作。接下来，以90°的康普顿角测量能量为70–100 kV的X射线装置的PHS，以获取光谱仪在这些能量下的响应。最后，在不同的康普顿角下对Theratron-780 Co-60临床机器的PHS进行了测量，并回收了相应的光子注量光谱。Theratron-780的注量光谱的结果显示出两个明确定义的峰，分别对应于Co-60源的1173和1332 keV。回收的光谱与通过蒙特卡洛模拟获得的光谱以及与在相应的兆伏范围内用作基准的标准Co-60校准源的光谱显示出良好的相关性。我们设计和制造的康普顿光谱仪可用于临床程序，以测量和重建用于临床机器的兆电压光子束光谱。