Method for removing improved conical bind CT ring shaped false shadow

Abstract

The invention discloses an improved method for eliminating ring artifacts in cone-beam CT reconstruction images. In the method, the read-in CT reconstruction images are converted into straight lines by coordinate transformation, and then the artifacts are parallel to the artifacts. The one-dimensional filter is a mask, and the intermediate image is searched step by step and line by line to obtain the sample space, and at the same time, the variance of the pixel value of each sample space is calculated, and the artifact is identified according to whether the variance is less than a predetermined threshold , the pixel value of each pixel in the sample space is replaced with the average pixel value of the pixel between the point and the vertical axis between the two artifacts to eliminate the ring artifact, and finally the intermediate image after the artifact is eliminated Change back to the original coordinate system to get the corrected image.

Description

technical field [0001] The invention relates to a processing method of medical CT images, in particular to a method for eliminating ring artifacts in cone-beam CT reconstruction images. Background technique [0002] Computed tomography, or CT (Computed Tomography), has been widely used in the field of clinical medicine in the 20th century. Since the birth of CT, its scanning method has developed from a two-dimensional single-detector parallel beam to a multi-detector fan-beam rotary scanning, and a three-dimensional CT has developed from the earliest single-row spiral CT to multi-row detector scanning. -Multislice spiral / helical CT (MSCT) with 32 layers of data. In recent years, cone-beam CT (CBCT) using area array detectors has gradually entered the practical stage. It uses cone-beam scanning to obtain two-dimensional projection data at various viewing angles, and directly obtains three-dimensional volumes after reconstruction. Compared with other geometric structures, th...

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Problems solved by technology

This method defines the filter in the direction of the vertical axis, and uses 2.5 times the sum of the pixel values ​​of the two points at the two ends of the 7 pixels under the filter to subtract the "difference" of the sum of the pixel values ​​​​of the center 5 points. Compare with the upper and lower limits set by the system, and then judge whether there is an artifact in the center pixel of the filter. Therefore, when the width of the artifact line is greater than or equal to the width of 7 pixels, the calculated "difference" will not fall. Within the upper and lower limits set by the system, it will inevitably cause misjudgment

In addition, the patent application scheme whose patent publication number is CN1720861A only uses the average value of the pixel values ​​of 7 points under the filter to correct the pixels of the artifact point, so when the width of the artifact line is greater than or equal to 7 pixel points When the width of , it is obviously equivalent to no replacement

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