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

本文尝试计算了CT（Computed Tomography）系统的基本X射线谱。由于初级X射线谱的剂量率很高，我们采用碳散射体降低了剂量率，并使90℃散射谱的测量成为可能。由90℃散射谱的测量数据，通过倒计数，可以计算出初级X射线谱。由于Raylei散射和多重散射可能发生在碳散射体中，因此在反向计算时，我们不仅使用Klein-Nishina系数，而且使用Monte Carlo方法得到的响应函数，结果表明，由Monte Carlo方法得到的响应函数计算的初级X射线能谱与由Klein-Nishina系数计算的初级X射线能谱大致相当。

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.