通过屏幕检测获取数字化X射线照片密度的方法

A method of digital X-ray photo density by screen test

目的找到一种在数字化X射线照片打印前预测照片密度的方法,以实现更好的照片质量控制,避免在照片密度调整过程中不必要的浪费。方法通过编写计算机程序检测屏幕上指定位置的输出值。采用适当条件对铝梯进行投照,投照后在工作站上调整图像,使得铝梯各阶对比良好,保存并打印图像。在屏幕上由低到高对铝梯各阶进行采样,获取屏幕上各点输出值。使用密度计对打印后的照片进行测量,获得照片上铝梯各阶对应的照片密度。绘制密度曲线,再与相应的照片密度相关联。结果通过上述方法对100张照片进行检测,将对应点预测值和密度计实际测量值进行比较,误差小于5%。结论该方法是对数字化X射线照片密度预测的一种新的尝试,通过一个小程序跨越了从影像的屏幕显示到照片打印之间的多个设备和程序调试环节,直接将屏幕上的输出值和打印后的照片密度进行关联,通过检测屏幕输出值获得照片密度的预测值。

Objective To control the quality of X-ray film and avoid complicated processes in photo density measurement, and establish a digital technique of X-ray photograph from screen image. Methods A computer program was designed to detect the output value of a specified location on screen image. Under appropriate conditions aluminum ladder was cast upon a screen. The cast image was adjusted on computer workstation to get the best contrast of aluminum ladder at every stage. Then the image was saved and printed. On screen image digital samples were taken from low to high aluminum ladder to get output values of each location. At the same time, on printed photos, the densities were measured by a density meter at each location where digital sample was taken. A density curve was then drawn and related to densities on printed photograph. Results A total of 100 digital images and printed photos were examined. Predicted values were compared with measured values at each corresponding location. The deviations were less than 5 %. Conclusion This technique is a novel trial for density prediction of digital X-ray photo. The newly designed computer program is a shortcut from screen image to photo print and avoids of using multiple devices and software debugging.