Method of removing metal artifact from CT image

Abstract

The present invention relates to a method of removing metal artifact from a CT image. The method comprises the steps of firstly carrying out the pre-processing via the image adaptive filtering to obtain an original reconstruction image from which the noise and a part of streak artifact are removed; then segmenting the original reconstruction image via a clustering method to obtain the areas of different tissues, establishing a model image, at the same time, carrying out the orthographic projection on a segmented metal area to obtain the position of the metal area in a projection domain; and then carrying out the orthographic projection on the model image to obtain the projection data of the model image, and then using the projection domain data of the model image to substitute for the projection domain data of the original reconstruction image according to the previously obtained position of the metal area in the projection domain; finally carrying out the filtering back projection on the repaired projection domain data to obtain a final corrected image. The method of the present invention reduces a real image accurately, enables the metal artifact to be removed effectively, and helps doctors to judge the states of illnesses accurately.

Description

technical field [0001] The invention relates to enhancement or restoration of CT images, in particular to a method for removing metal artifacts from CT images. Background technique [0002] Medically, metal implants have been used to repair the human body for more than 400 years. In the early days, doctors used pure gold plates to repair skulls and inlays, and then used silver, iron, and iron-based alloys to fix fractures. Joints, cobalt-based alloys were used as human implants in modern times, and stainless steel was also used in large quantities. With the development of the rare metal industry, rare metals such as processed titanium, cast titanium, and niobium were clinically applied to the human body. Today, titanium alloys Because of its high strength, good corrosion resistance, and high heat resistance, it is the first choice for human implants and has been widely used. [0003] MRI is a biological magnetic spin imaging technology. It utilizes the characteristics of nu...

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Problems solved by technology

[0006] 1) Because there is a very strong magnetic field in the MRI machine and MRI examination room, those who have cardiac pacemakers, and those who have left metal clips and metal stents after vascular surgery, or other coronary arteries, esophagus, and prostate 1. It is strictly forbidden to undergo MRI examination for patients undergoing metal stent surgery in the biliary tract. Otherwise, due to the metal being attracted by a strong magnetic field and moving, serious consequences may even be life-threatening.

[0007] 2) For patients with metal implants, a large number of artifacts may appear on the metal implant area of ​​the MRI image during inspection, which affects the image diagnostic performance

[0012] The iterative reconstruction algorithm is theoretically a very good method for removing metal artifacts. This algorithm can effectively remove metal artifacts and suppress noise, and can well present the structure of metal objects. Practical

Removing metal artifacts in the projection domain is a pre-processing method and has certain advantages, because the post-processing method of removing metal artifacts in the image domain needs to go through back-projection algorithms such as FBP, which will increase the impact of metal artifacts on real data , and the reconstructed image containing metal artifacts has been heavily polluted, processing on this basis will inevitably bring large errors

However, most of the current mainstream algorithms are post-processing algorithms based on reconstructed images. The reasons are as follows: 1. Post-processing methods based on reconstructed images do not require original raw data, but only reconstructed images in DICOM format. Can complete the elimination of metal artifacts, data acquisition is relatively simple

2. There are many technical difficulties in the pre-processing method based on the projection domain. First, the amount of projection data is very large. Secondly, it is difficult to have an accurate method to separate the metal part from other human body parts in the projection domain, so it is difficult to accurately restore metal pollution. projection data, so although metal artifact removal from the projection domain has its advantages, its applicability is not as good as post-processing algorithms in the image domain

The difficulty of this method is how to establish an accurate model image to restore the real image, which is the fundamental difference between different model correction algorithms

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