Slit-method measurement method for modulation transfer function of digital X-ray imaging system

Abstract

The invention relates to a slit-method measurement method for a modulation transfer function of a digital X-ray imaging system. The slit-method measurement method comprises the following steps: 1) setting exposure parameters of the digital X-ray imaging system and collecting slit images; 2) carrying out slit position detection through edge detection and obtaining a slit straight line by utilizing line fitting; 3) carrying out Hough transformation on a slit straight line image to obtain slit inclination angle alpha, and constructing an oversampling LSF curve; 4) utilizing an I-spline curve as a regression spline curve f to carry out least square fit on the left and right two parts of the oversampling LSF curve, and meanwhile, meeting constraint conditions, that is, during fitting, guaranteeing that the left part of the LSF curve is a monotone non-decreasing function, and the right part is a monotone non-increasing function, and obtaining a line spread function; and 5) carrying out Fourier transform and then mod operation on the line spread function to obtain a modulation transfer function thereof, and finally, obtaining a normalized modulation transfer function. Compared with the conventional slit measurement method, the method can obtain more accurate MTF curve.

Description

Technical field [0001] The invention belongs to the fields of biomedical engineering and computers, and relates to a new method for accurately measuring the modulation transfer function of a digital X-ray imaging system by a slit method. Background technique [0002] The modulation transfer function (Modulation Transfer Function, MTF) is the transfer function of the modulation degree, which is a quantitative description of the spatial frequency transmission characteristics of the linear image system, and is an important progress in the image evaluation method. Previously, qualitative description indicators, such as image density, contrast, sharpness, resolution, and distortion, were commonly used to evaluate the image quality of imaging systems, but the results were greatly affected by personal subjective factors. In recent years, with the rapid development of digital X-ray imaging technology, MTF as an objective index has become an important image evaluation method that rad...

AI Technical Summary

Problems solved by technology

Aiming at the problem of low signal-to-noise ratio of the LSF tail signal and difficulty in accurate estimation when the slit method is used to obtain the oversampled LSF curve, the invention adopts the I-spline curve fitting method that integrates the prior knowledge of the detector characteristics, so that a more traditional narrow curve can be obtained. More accurate MTF curves by seam measurement method

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