Le Heron J C, Poletti J L
National Radiation Laboratory, Christchurch, New Zealand.
Phys Med Biol. 1988 Jan;33(1):93-104. doi: 10.1088/0031-9155/33/1/009.
A method is presented for determining the modulation transfer function (MTF) of an image intensifier as it is found in the x-ray department. The image of an edge input into the image intensifier tube is photographed at the television camera port with a high quality camera and the photographic image scanned with a microdensitometer. Densitometric conversion enables the determination of the edge spread function and further calculation produces the line spread function and the MTF. A correction is made for the camera/lens/film/developer response function. Results from the use of the technique on over 25 x-ray image intensifiers in New Zealand hospital x-ray departments are presented and discussed. Most of the image intensifiers had been in use for more than 7 years. The low-frequency drop values were similar to reported values with an average value of 22%, but modulation values at 1 cycle/mm (the average value was 29%) were generally lower than values previously reported, indicating that the sharpness performance in the clinical environment is inferior to claims for new or state-of-the-art intensifiers.
本文介绍了一种测定X射线科中图像增强器调制传递函数（MTF）的方法。将边缘图像输入图像增强器管，在电视摄像机端口用高质量相机拍摄，并使用微密度计扫描照片图像。密度测量转换可确定边缘扩展函数，进一步计算可得出线扩展函数和MTF。对相机/镜头/胶片/显影剂响应函数进行了校正。展示并讨论了在新西兰医院X射线科对25台以上X射线图像增强器使用该技术的结果。大多数图像增强器已使用超过7年。低频下降值与报告值相似，平均值为22%，但在1周期/毫米处的调制值（平均值为29%）通常低于先前报告的值，这表明临床环境中的清晰度性能不如新型或最先进增强器的宣称。
