闪光照相中源尺寸和散射对成像的影响

 利用Monte Carlo(MC)模拟技术解释实验中心线灰度曲线的各部分波形。结果发现，系统中的散射照射量、光源的尺寸和H-D特征曲线的形状对实验灰度曲线的各部分波形均有影响：散射量越大，中心信号幅度越低;H-D曲线趾部的非线性越严重，中心信号幅度也越低;光源尺寸造成图像越模糊。指出了用实验波形可以半定量确定系统散射程度和光源尺寸。在测量照射量时，应该尽可能避免散射的干扰,用台阶法测量H-D曲线时，应使台阶远离剂量片而前移。

Effects of source spot size and scatter on imaging in radiography

The profile and its detail information of the center projecting line of the radiographic image is interpreted with the results of the Monte Carlo simulation.It is found that the scatter,the source spot size and the shape of H-D characteristic curve all affect the experimental gray curve and its detail information of the center projecting line.The more the scatter exposure is,the lower the amplitude of the center signal is.The severer the non-linearity on the toe of H-D curve is,the lower the amplitude of the center signal is.It is pointed out that comparing the experimental gray curve with the Monte Carlo simulation results can ensure the scatter level and the source spot size half-quantitatively.When the exposure is being measured,the scatter interference should be removed.It is proposed to move the step farther away from the detector when the step method is used to measure the H-D characteristic curve.