Rezaee M R, van der Zwet P M, Gerbrands J J, Reiber J H
University Hospital Leiden, Department of Diagnostic Radiology and Nuclear Medicine, The Netherlands.
Invest Radiol. 1996 Mar;31(3):161-72. doi: 10.1097/00004424-199603000-00007.
To derive a theoretical model for the modulation transfer function (MTF) of the complete imaging chain of a cardiovascular x-ray system. A sufficiently accurate MTF model may be used in quantitative coronary arteriographic applications to decrease the systematic overestimation of small coronary vessels. The model could be used to restore blurred images in image restoration applications and also may be used for image quality assurance measurements.
Digital images of a step wedge phantom were acquired at different modes (5-, 7-, and 9-inch) of the image intensifier and at different kilovolt levels of the x-ray generator. From these images the MTFs that were used to estimate the parameters of the model were assessed.
The total MTF of the cardiovascular x-ray imaging chain consisting of image intensifier, video camera, optical elements, and analog/digital converter can be modeled by the simple formula MTF = e-(w/f)R, where w is the frequency in linepairs per millimeter. The constants frequency f and the device index n are parameters that can be derived for an individual x-ray system using the phantom. In this formula, the contribution from the focus of the x-ray source has been excluded. The mean square error (MSE) between the measured values and those assessed from the theoretical model of the MTF for the horizontal direction was found to be equal to 0.00003 for the 5-inch mode of image intensifier, and for the vertical resolution at the 9-inch mode this MSE was equal to 0.00038. In addition, we have demonstrated that the contributions of the video camera and the image intensifier to the total MTF can be replaced by an imaginary electron-optical device.
An accurate representation for the MTF of a cardiovascular x-ray system has been derived. This MTF model can be used in x-ray image quality assurance measurements and in quantitative image processing applications.
推导心血管X射线系统完整成像链调制传递函数（MTF）的理论模型。一个足够精确的MTF模型可用于定量冠状动脉造影应用，以减少对小冠状动脉的系统性高估。该模型可用于图像恢复应用中的模糊图像恢复，也可用于图像质量保证测量。
在图像增强器的不同模式（5英寸、7英寸和9英寸）以及X射线发生器的不同千伏水平下采集阶梯楔形体模的数字图像。从这些图像中评估用于估计模型参数的MTF。
由图像增强器、摄像机、光学元件和模拟/数字转换器组成的心血管X射线成像链的总MTF可以用简单公式MTF = e-(w/f)R建模，其中w是以每毫米线对数为单位的频率。常数频率f和设备指数n是可以使用体模为单个X射线系统推导的参数。在此公式中，已排除X射线源焦点的贡献。对于5英寸模式的图像增强器，测量值与MTF理论模型评估值在水平方向的均方误差（MSE）等于0.00003，对于9英寸模式的垂直分辨率，该MSE等于0.00038。此外，我们已经证明，摄像机和图像增强器对总MTF的贡献可以用一个虚拟的电子光学设备来替代。
已得出心血管X射线系统MTF的准确表示。该MTF模型可用于X射线图像质量保证测量和定量图像处理应用。
