US-12620154-B2 - Systems and methods for correcting projection images in computed tomography image reconstruction

US12620154B2US 12620154 B2US12620154 B2US 12620154B2US-12620154-B2

Abstract

A method for correcting projection images in CT image reconstruction is provided. The method may include obtaining a plurality of projection images of a subject. Each of the plurality of projection images may correspond to one of the plurality of gantry angles. The method may further include correcting a first projection image of the plurality of projection images according to a process for generating a corrected projection image. The process may include performing, based on the first projection image and a second projection image of the plurality of projection images, a first correction on the first projection image to generate a preliminary corrected first projection image. The process may also include performing, based on at least part of the preliminary corrected first projection image, a second correction on the preliminary corrected first projection image to generate a corrected first projection image corresponding to the first gantry angle.

Inventors

Hongcheng YANG
Jianwei Zhu
Haining Sun
Jonathan Maltz

Assignees

SHANGHAI UNITED IMAGING HEALTHCARE CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20240115
Priority Date: 20181105

Claims (20)

1 . A system, comprising: a storage device storing a set of instructions; and at least one processor in communication with the storage device, wherein when executing the set of instructions, the at least one processor is configured to cause the system to: obtain a plurality of projection images of a subject, the plurality of projection images being generated according to scan data acquired by a CT scanner at a plurality of gantry angles, each of the plurality of projection images corresponding to one of the plurality of gantry angles; and generate a corrected first projection image by performing a first correction on a first projection image of the plurality of images based on a second projection image of the plurality of projection images, the first projection image and the second projection image corresponding to different gantry angles of the plurality of gantry angles.
2 . The system of claim 1 , wherein the first projection image corresponds to a first gantry angle of the plurality of gantry angles, the second projection image corresponds to a second gantry angle of the plurality of gantry angles, and the second gantry angle is a neighboring gantry angle of the first gantry angle among the plurality of gantry angles.
3 . The system of claim 1 , wherein the performing the first correction on the first projection image comprises: determining, based on a difference between the first projection image and the second projection image, a first correction coefficient of the first projection image; and performing the first correction on the first projection image based on the first correction coefficient.
4 . The system of claim 3 , wherein the difference between the first projection image and the second projection image is a difference between grey information of the first projection image and grey information of the second projection image.
5 . The system of claim 1 , wherein a preliminary corrected first projection image is generated by the first correction, the corrected first projection image is generated by further performing a second correction on the preliminary corrected first projection image, and the second correction comprises: identifying one or more pixels in the preliminary corrected first projection image, the one or more identified pixels corresponding to a middle-channel of the CT scanner at a first gantry angle; for each pixel of the one or more pixels, identifying an opposite pixel corresponding to the pixel of the one or more pixels; and generating the corrected first projection image corresponding to the first gantry angle based on the one or more pixels and the one or more opposite pixels.
6 . The system of claim 5 , wherein the generating the corrected first projection image corresponding to the first gantry angle based on the one or more pixels and the one or more opposite pixels comprises: generating, based on the one or more opposite pixels of the one or more pixels, a reference image of the preliminary corrected first projection image; determining, based on a difference between the one or more pixels and the reference image, a second correction coefficient of the preliminary corrected first projection image; and generating, based on the second correction coefficient and the preliminary corrected first projection image, the corrected first projection image corresponding to the first gantry angle.
7 . The system of claim 1 , the at least one processor is further configured to cause the system to: correct the plurality of projection images to generate a plurality of corrected projection images; and reconstruct, based on the plurality of corrected projection images, a CT image of the subject.
8 . The system of claim 7 , wherein to correct the plurality of projection images, the at least one processor is further configured to cause the system to: perform one or more iterations, each current iteration of the one or more iterations including: correcting the plurality of projection images in the current iteration to generate the plurality of corrected projection images in the current iteration; determining whether the plurality of corrected projection images in the current iteration satisfy a condition; and in response to a result of the determination that the plurality of corrected projection images fail to satisfy the condition, designating the plurality of corrected projection images in the current iteration as the plurality of projection images in a next iteration.
9 . The system of claim 8 , wherein the current iteration of the one or more iterations further includes: in response to a result of the determination that the plurality of corrected projection images satisfy the condition, terminating the one or more iterations.
10 . The system of claim 1 , wherein to generate the corrected first projection image, the at least one processor is further configured to cause the system to: preprocessing the first projection image to generate a preprocessed first projection image, the preprocessing of the first projection image including at least one of a beam hardening correction or a scattering correction; and generating the corrected first projection image by performing the first correction on the preprocessed first projection image.
11 . The system of claim 1 , wherein the at least one processor is further configured to cause the system to: post-processing the corrected first projection image, the post-processing of the corrected first projection image including at least one of a beam hardening correction or a scattering correction.
12 . A method implemented on a computing device having at least one processor and at least one storage device, the method comprising: obtaining a plurality of projection images of a subject, the plurality of projection images being generated according to scan data acquired by a CT scanner at a plurality of gantry angles, each of the plurality of projection images corresponding to one of the plurality of gantry angles; and generating a corrected first projection image by performing a first correction on a first projection image of the plurality of images based on a second projection image of the plurality of projection images, the first projection image and the second projection image corresponding to different gantry angles of the plurality of gantry angles.
13 . The method of claim 12 , wherein the first projection image corresponds to a first gantry angle of the plurality of gantry angles, the second projection image corresponds to a second gantry angle of the plurality of gantry angles, and the second gantry angle is a neighboring gantry angle of the first gantry angle among the plurality of gantry angles.
14 . The method of claim 12 , wherein the performing the first correction on the first projection image comprises: determining, based on a difference between the first projection image and the second projection image, a first correction coefficient of the first projection image; and performing the first correction on the first projection image based on the first correction coefficient.
15 . The method of claim 14 , wherein the difference between the first projection image and the second projection image is a difference between grey information of the first projection image and grey information of the second projection image.
16 . The method of claim 12 , wherein a preliminary corrected first projection image is generated by the first correction, the corrected first projection image is generated by further performing a second correction on the preliminary corrected first projection image, and the second correction comprises: identifying one or more pixels in the preliminary corrected first projection image, the one or more identified pixels corresponding to a middle-channel of the CT scanner at a first gantry angle; for each pixel of the one or more pixels, identifying an opposite pixel corresponding to the pixel of the one or more pixels; and generating the corrected first projection image corresponding to the first gantry angle based on the one or more pixels and the one or more opposite pixels.
17 . The method of claim 16 , wherein the generating the corrected first projection image corresponding to the first gantry angle based on the one or more pixels and the one or more opposite pixels comprises: generating, based on the one or more opposite pixels of the one or more pixels, a reference image of the preliminary corrected first projection image; determining, based on a difference between the one or more pixels and the reference image, a second correction coefficient of the preliminary corrected first projection image; and generating, based on the second correction coefficient and the preliminary corrected first projection image, the corrected first projection image corresponding to the first gantry angle.
18 . The method of claim 12 , the method further includes: correcting the plurality of projection images to generate a plurality of corrected projection images; and reconstructing, based on the plurality of corrected projection images, a CT image of the subject.
19 . The system of claim 18 , wherein the correcting the plurality of projection images includes: perform one or more iterations, each current iteration of the one or more iterations including: correcting the plurality of projection images in the current iteration to generate the plurality of corrected projection images in the current iteration; determining whether the plurality of corrected projection images in the current iteration satisfy a condition; and in response to a result of the determination that the plurality of corrected projection images fail to satisfy the condition, designating the plurality of corrected projection images in the current iteration as the plurality of projection images in a next iteration.
20 . A non-transitory computer readable medium, comprising a set of instructions, wherein when executed by at least one processor, the set of instructions direct the at least one processor to effectuate a method, the method comprising: obtaining a plurality of projection images of a subject, the plurality of projection images being generated according to scan data acquired by a CT scanner at a plurality of gantry angles, each of the plurality of projection images corresponding to one of the plurality of gantry angles; and generating a corrected first projection image by performing a first correction on a first projection image of the plurality of images based on a second projection image of the plurality of projection images, the first projection image and the second projection image corresponding to different gantry angles of the plurality of gantry angles.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation of U.S. patent application Ser. No. 18/062,001, filed on Dec. 5, 2022, which is a continuation of U.S. patent application Ser. No. 17/158,030 (now U.S. Pat. No. 11,521,336), filed on Jan. 26, 2021, which is a continuation of U.S. patent application Ser. No. 16/252,826 (now U.S. Pat. No. 10,922,856), filed on Jan. 21, 2019, which claims priority of Chinese Patent Application No. 201811306943.1, filed on Nov. 5, 2018 and is a continuation of International Application No. PCT/CN2018/087884, filed on May 22, 2018, which is a continuation-in-part of International Application No. PCT/CN2017/110032, filed on Nov. 8, 2017. Each of the above-referenced applications is incorporated herein by reference in its entirety. TECHNICAL FIELD The present disclosure generally relates to computed tomography (CT) techniques, and more particularly, relates to systems and methods for correcting projection images in CT image reconstruction. BACKGROUND CT techniques are widely used in clinical examinations and medical diagnoses in recent years. During a CT scan of a subject, the X-ray imaging source and the detector may rotate with the gantry around the subject to scan the subject at a plurality of gantry angles. Then a plurality of projection images corresponding to the gantry angles may be generated based on the scan data. However, the radiation dose delivered to the subject may fluctuate when the gantry rotates, which may lead to an inconsistency between the projection images. For example, the fluctuations of the radiation dose delivered to the subject may result in a difference between the actual gray values and ideal gray values of the projection images corresponding to the plurality of gantry angles. When a CT image of the subject is reconstructed based on the projection images, the CT image may have a poor imaging quality, which may cause a false medical diagnosis or an inaccurate treatment positioning. Thus, it is desirable to correct and/or normalize the projection images to reduce the effect of the uneven radiation doses at different gantry angles. SUMMARY In one aspect of the present disclosure, a system is provided. The system may include a storage device, and at least one processor in communication with the storage device. The storage device may store a set of instructions. When executing the set of instructions, the at least one processor may be configured to cause the system to obtain a plurality of projection images of a subject. The plurality of projection images may be generated according to scan data acquired by a CT scanner at a plurality of gantry angles. Each of the plurality of projection images may correspond to one of the plurality of gantry angles. The at least one processor may be further configured to cause the system to correct a first projection image of the plurality of projection images according to a process for generating a corrected projection image. The first projection image may correspond to a first gantry angle of the plurality of gantry angles. The process may include performing, based on the first projection image corresponding to the first gantry angle and a second projection image of the plurality of projection images, a first correction on the first projection image to generate a preliminary corrected first projection image. The second projection image may correspond to a second gantry angle of the plurality of gantry angles. The process may further include performing, based on at least part of the preliminary corrected first projection image, a second correction on the preliminary corrected first projection image to generate a corrected first projection image corresponding to the first gantry angle. In some embodiments, the at least one processor may be further configured to cause the system to correct the plurality of projection images to generate a plurality of corrected projection images according to the process for generating a corrected projection image, and reconstruct a CT image of the subject based on the plurality of corrected projection images. In some embodiments, to correct the plurality of projection images, the at least one processor may be further configured to cause the system to perform one or more iterations. Each current iteration of the one or more iterations may include correcting the plurality of projection images in the current iteration to generate a plurality of corrected projection images according to the process for generating a corrected projection image, and determining whether the plurality of corrected projection images in the current iteration satisfy a condition. Each current iteration may also include in response to a result of the determination that the plurality of corrected projection images fail to satisfy the condition, designating the plurality of corrected projection images in the each current iteration as the plurality of projection images in a next iteration. In some embodi