Development of quality control system of computed tomographic X-ray unit to decrease patient dose in diagnosis

我们试图计算CT（计算机断层扫描）系统的初级x射线谱。由于初级x射线光谱的剂量率很高，因此我们采用碳散射体降低剂量率，并利用CdZnTe探测器实现了90℃散射光谱的测量。利用90℃散射光谱的实测数据，通过倒计数计算出主x射线谱。由于碳散射体中可能存在雷雷散射和多重散射，因此在反向计数时，我们不仅使用Klein-Nishina系数，还使用蒙特卡罗方法得到的响应函数。在我们的结果中，由蒙特卡罗方法得到的响应函数计算的主x射线谱与由Klein-Nishina系数计算的主x射线谱大致等效。

We have attempted to calculate a primary X-ray -spectrum of CT (Computed Tomography) system. Dose rates of primary X-ray spectrum are very high, so we reduced dose rate by using carbon scatterer and enabled to measure 90℃ scattered spectrum with a CdZnTe detector. The primary X-ray spectrum can be calculated from measured data of 90℃ scattered spectrum by counting backwards. In counting backwards, we used not only Klein-Nishina coefficients but also response functions obtained by Monte Carlo methods, because Raylei scattering and multiple scattering maybe occur in carbon scatterer.In our results, the primary X-ray spectrum calculated from response functions obtained by Monte Carlo methods are roughly equivalent to that calculated from Klein-Nishina coefficients.