Measurement Method of Modulation Transfer Function Based on Detector Characteristic of X-ray Imaging System

Abstract

The invention belongs to the field of biomedical engineering and a computer and relates to a modulation transfer function measurement method on the basis of the characteristics of a detector of an X-ray imaging system. The modulation transfer function measurement method comprises the following steps of: placing a knife edge testing instrument to enable the knife edge testing instrument to be clung to the detector, enabling an inclination angle to be formed between a knife edge and the sampling direction of the detector and continuously acquiring a plurality of images; carrying out superposition averaging on a plurality of knife edge images, reducing system noise and then carrying out knife edge boundary detection on an averaged knife edge image to obtain a knife edge boundary line; carrying out Hough transform on a knife edge boundary line graph to obtain a knife edge inclination angle alpha and establishing an oversampling ESF (Extended Superframe Format) curve; using a C spline as a regression spline f for carrying out segmentation fitting on the oversampling ESF curve; carrying out differential operation to obtain a line spread function; carrying out Fourier transform on the line spread function and then carrying out modulus acquisition to obtain a modulation transfer function; and carrying out normalization processing. The modulation transfer function measurement method solves the problem of fitting error generated when the oversampling ESF curve is acquired by a knife edge method; and compared with a conventional knife edge measurement method, the modulation transfer function measurement method can obtain a more accurate MTF (Modulation Transfer Function) curve.

Description

Technical field [0001] The invention belongs to the fields of biomedical engineering and computer, and relates to a new method for accurately measuring the modulation transfer function of a digital X-ray imaging system. Background technique [0002] Modulation Transfer Function (MTF) is the transfer function of modulation degree, a quantitative description of the spatial frequency transmission characteristics of linear image systems, and an important development in image evaluation methods. Previously, qualitative descriptive indicators, such as image density, contrast, sharpness, resolution, and distortion, were generally 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 indicator has become an important image evaluation method that radiography workers and researchers pay attention to. At the same time, M...

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Problems solved by technology

But so far, because the above methods do not make full use of the prior knowledge of the nature of the detector itself, there are still major deficiencies in the accuracy and robustness of MTF evaluation

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