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Knife-edge measuring method of modulation transfer function of digital X-ray imaging system

A modulation transfer function and imaging system technology, applied in biomedical engineering and computer fields, can solve problems such as strict and precise positioning work, difficult operation, non-integer interpolation number, etc.

Inactive Publication Date: 2012-12-05
TIANJIN UNIV
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Problems solved by technology

The oversampling process can be realized by interpolation. The number of interpolation points is determined by the angle of the knife edge. However, since the actual number of pixels can only be an integer value, the interpolation numbers calculated by the angle of the knife edge are generally non-integer.
If you want to place a suitable inclination angle of the knife edge to obtain the integer interpolation number, you must use extremely strict precise positioning work, and the operation is extremely difficult

Method used

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  • Knife-edge measuring method of modulation transfer function of digital X-ray imaging system
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  • Knife-edge measuring method of modulation transfer function of digital X-ray imaging system

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Embodiment Construction

[0027] The present invention will be described in detail below from several aspects in conjunction with the accompanying drawings and embodiments.

[0028] 1 MTF oversampling knife-edge measurement method

[0029] Using oversampling technology to reconstruct ERF, it is necessary to place the knife edge and the detector matrix at a certain inclination angle, and usually keep the inclination angle α between the edge of the instrument and the direction of the digital detector array at 1.5°-7.1° (the corresponding interpolation number is 8-38 bar), the smaller α (the higher the interpolation number), the higher the resolution of the obtained MTF curve.

[0030] The schematic diagram of the knife-edge obtained by the over-sampling knife-edge measurement method is as follows: figure 1 shown. The gray parts in the figure represent the area covered by the brass plate, and the thick black line represents the edge of the knife edge after coaxial alignment and ideal cutting. figure 1 ...

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Abstract

The invention belongs to the fields of biomedical engineering and computers, and relates to a knife-edge measuring method of a modulation transfer function (MTF) of a digital X-ray imaging system. The knife-edge measuring method comprises the following steps of: acquiring a plurality of knife-edge images; performing knife-edge boundary detection to obtain a knife-edge boundary straight line; performing Hough conversion on a knife-edge boundary straight line graph to obtain a knife-edge inclination angle; calculating distance from each point close to the knife-edge boundary to the knife-edge straight line, and ordering from small to large according to the distance to form a non-uniformly sampled ERF (Edge Response Function) curve sequence; acquiring an ERF new sequence of a uniform sampling interpolation position by using a center-of-gravity-based Lagrange interpolation method; acquiring a line spread function; and acquiring a normalized modulation transfer function. According to the knife-edge measuring method, an accurate over-sampling ERF curve is constructed, and finally, a more accurate MTF curve compared with that of the conventional knife-edge measuring method can be obtained.

Description

technical field [0001] The invention belongs to the fields of biomedical engineering and computers, and relates to an accurate measurement method for a modulation transfer function of a digital X-ray imaging system. Background technique [0002] The Modulation Transfer Function (MTF) is the transfer function of the modulation degree, and it is a quantitative description of the spatial frequency transmission characteristics of the linear imaging system, and it 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 radiographers and researchers pay attention to. ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01M99/00
Inventor 周仲兴高峰赵会娟张力新王广印
Owner TIANJIN UNIV
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