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A Method of Using Projection Data to Remove Ring Artifacts Caused by CT Detector Faults

A technology of projection data and ring artifacts, which is applied in the field of medical image processing, can solve problems such as the inability to accurately estimate missing information, and the inability to well remove CT image ring artifacts, etc.

Active Publication Date: 2018-06-19
SOUTHERN MEDICAL UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, when the detection elements on the detector have continuous large-scale "necrosis", the above-mentioned master's degree thesis cannot accurately estimate the missing information by using only the interpolation method, not only cannot remove the ring artifact in the CT image well, And also new artifacts due to misestimation of missing information

Method used

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  • A Method of Using Projection Data to Remove Ring Artifacts Caused by CT Detector Faults
  • A Method of Using Projection Data to Remove Ring Artifacts Caused by CT Detector Faults
  • A Method of Using Projection Data to Remove Ring Artifacts Caused by CT Detector Faults

Examples

Experimental program
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Effect test

example 1

[0030] figure 1 The projected sinusoidal image of a human head with a size of 256×256 obtained for a faulty flat panel detector with 367 CT detection elements, wherein the number of consecutive faulty CT detection elements of the faulty flat panel detector is 21, and located at the Columns 120 to 140 (failure rate 21 / 367=5.7%). figure 1 The image shown is obtained in an orbital CT imaging system, wherein the distance from the focal point of the radiation source of the CT imaging system to the system rotation center is 500 mm, and the distance from the system rotation center to the detector is 500 mm. figure 1 The image shown is the projection data of 720 angles obtained by using the above-mentioned circular orbit CT imaging system to collect once at intervals of 0.5 degrees within a range of 360 degrees. The obtained projection data are directly reconstructed by filtered back projection to obtain the following figure 2 CT image shown. Depend on figure 2 It can be seen th...

example 2

[0053] In order to further verify the technical effect of the ring artifact removal method of the present invention, the inventor has also done the following research:

[0054] 1. Obtain a comparison image

[0055] (A) The projected sinusoidal matrices obtained in the 1st and 2nd iterations of step (5) of Example 1 are respectively subjected to filtered back-projection reconstruction, and the results are as follows Figure 5 shown in a and 5b.

[0056] (B) According to the same method as example 1, deal with it separately Image 6 a and Figure 7 The CT projection data corresponding to a, the reconstruction result is as follows Image 6 c and Figure 7 as shown in c. in, Image 6 a is the CT image obtained when the detectors in the 120th row to the 130th row have continuous failures (failure rate 11 / 367=3%), Figure 7 a is the CT image obtained when the detectors in the 80th row to the 180th row have continuous faults (failure rate 101 / 367=27.52%); Image 6 a and Fig...

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Abstract

The invention relates to a method for using projection data to remove ring artifacts caused by CT detection element failures. The method includes the following steps: (1) Import the projection data to obtain a matrix A, detect the position of the fault area in the matrix A, and use the fault area to The two columns of data other than the left and right columns perform linear interpolation on the columns corresponding to the fault area to obtain the matrix B; (2) Perform filtered back-projection reconstruction on the matrix B and then perform mean filtering and forward projection to obtain the projected sinusoidal matrix C; (3) ) Subtract matrix C from matrix A, and then use the left and right column data outside the column corresponding to the fault area in the difference matrix to linearly interpolate the column corresponding to the fault area to obtain matrix D; (4) Combine matrix C with the matrix Add D to obtain matrix E; (5) Return to step (2), continuously loop steps (2) to (4) until the preset number of iterations is reached, and then perform filtered back-projection reconstruction on the obtained result, and obtain CT image after artifact removal. This method can eliminate ring artifacts caused by continuous large-area failures of CT detection elements.

Description

technical field [0001] The invention relates to a medical image processing, in particular to image enhancement or restoration, in particular to a CT image ring artifact elimination method. Background technique [0002] CT, or computed tomography, is widely used in many fields such as medical diagnosis. However, in the CT system, due to the constraints of the processing precision and service life of the detector, the reconstructed CT image is often accompanied by the appearance of ring artifacts. Ring artifacts can affect subsequent image processing operations, such as image denoising, image segmentation, image measurement, and so on. [0003] CT image ring artifact correction methods are mainly divided into CT image correction method and projection sinogram correction method. The idea of ​​the CT image correction method is to firstly transform the circular artifact in the Cartesian coordinate system to the polar coordinate system, transform the shape of the artifact from a...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06T5/00
CPCG06T2207/10081G06T2207/30004G06T2207/20182G06T5/70
Inventor 周凌宏齐宏亮袁翠云陈梓嘉徐圆吴书裕
Owner SOUTHERN MEDICAL UNIVERSITY
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