US-12626440-B2 - Correction apparatus, system, method, and program

US12626440B2US 12626440 B2US12626440 B2US 12626440B2US-12626440-B2

Abstract

A system that can reduce the cost for correcting artifacts due to motion in the reconstruction of CT images includes acquiring the temporarily corrected projection image and determining the reference center position correction function and the parameter of the temporary reference center position correction function by calculating a degree of coincidence between the temporarily corrected projection image and the projection image at the imaging angle opposing thereto, and correcting the main imaging data or the projection image based on the main imaging data using the reference center position correction function and the relative motion correction function.

Inventors

Shota Taguchi
Takumi Ota

Assignees

RIGAKU CORPORATION

Dates

Publication Date: 20260512
Application Date: 20230630
Priority Date: 20220630

Claims (12)

1 . A correction apparatus for correcting artifacts due to motion during CT image measurement, comprising: processing circuitry configured to acquire main imaging data scanned by 360° and reference imaging data, convert the main imaging data and the reference imaging data into projection images, align the projection image based on the reference imaging data and the projection image based on the main imaging data corresponding to an imaging angle of the reference imaging data and calculating a relative motion correction value respectively for the imaging angle, generate a relative motion correction function for correcting a relative motion of all the main imaging data or all the projection image based on the main imaging data based on the relative motion correction value, set a temporary reference center position correction function which is a function that assumes a deviation of a sample rotation axis with respect to a central axis in a detector plane of the main imaging data, temporarily correct the projection image based on the main imaging data with the temporary reference center position correction function and the relative motion correction function, acquire the temporarily corrected projection image, calculate a degree of coincidence between the temporarily corrected projection image and the projection image at the imaging angle opposing thereto, determine a reference center position correction function based on parameters of the temporary reference center position correction function, the reference center position correction function is a function representing the deviation of the sample rotation axis with respect to the central axis in the detector plane of the main imaging data, and correct the main imaging data or the projection image based on the main imaging data by using the reference center position correction function and the relative motion correction function.
2 . The correction apparatus according to claim 1 , wherein the processing circuitry is further configured to normalize an X-ray intensity of the main imaging data or the reference imaging data and generate a feature extracted projection image in which a feature is extracted from a projection image based on the normalized main imaging data or reference imaging data, and calculate the relative motion correction value based on the feature extracted projection image of the reference imaging data and the feature extracted projection image of the main imaging data corresponding thereto.
3 . The correction apparatus according to claim 2 , wherein the processing circuitry is further configured to perform noise removal before extracting the feature.
4 . The correction apparatus according to claim 2 , wherein the processing circuitry is further configured to temporarily correct the feature extracted projection image based on the main imaging data, and acquire the temporarily corrected feature extracted projection image and determine a parameter of the temporary reference center position correction function based on a degree of coincidence between the temporarily corrected feature extracted projection image and the feature extracted projection image at an imaging angle opposing thereto.
5 . The correction apparatus according to claim 1 , wherein the relative motion correction function is a polynomial of order determined based on a number of frames of reference imaging data.
6 . The correction apparatus according to claim 5 , wherein the order of the relative motion correction function is less than or equal to ½ of the number of frames of the reference imaging data.
7 . The correction apparatus according to claim 1 , wherein the main imaging data and the reference imaging data are data obtained with a fan beam or a cone beam, wherein the processing circuitry is further configured to acquire conversion data obtained based on fan-parallel conversion on the temporarily corrected projection image and determines a parameter of the temporary reference center position correction function based on a degree of coincidence between the conversion data and the conversion data at an angle opposing thereto.
8 . The correction apparatus according to claim 1 , wherein the calculation of the relative motion correction value or the determination of the parameter of the temporary reference center position correction function is performed based on a partial region of the projection image or the temporarily corrected projection image.
9 . The correction apparatus according to claim 1 , wherein the processing circuitry is further configured to perform reconstruction based on projection images based on the main imaging data corrected or the projection image based on the main imaging data and generate a CT image, and cause a displaying device to display the CT image.
10 . A system comprising, a CT apparatus comprising an X-ray source for generating X-rays, a detector for detecting X-rays and a rotation control unit for controlling the rotation of the X-ray source and the detector or a sample, and the correction apparatus according to claim 1 .
11 . A method for correcting artifacts due to motion during CT image measurement, the method comprising the steps of: acquiring main imaging data scanned by 360° and reference imaging data; converting the main imaging data and the reference imaging data into projection images; aligning the projection image based on the reference imaging data and the projection image based on the main imaging data corresponding to an imaging angle of the reference imaging data and calculating a relative motion correction value respectively for the imaging angle; generating a relative motion correction function for correcting a relative motion of all the main imaging data or all the projection image based on the main imaging data based on the calculated relative motion correction value, setting a temporary reference center position correction function which is a function that assumes a deviation of a sample rotation axis with respect to a central axis in a detector plane of the main imaging data; temporarily correcting the projection image based on the main imaging data with the temporary reference center position correction function and the relative motion correction function; acquiring the temporarily corrected projection image calculating a degree of coincidence between the temporarily corrected projection image and the projection image at the imaging angle opposing thereto; determining a reference center position correction function based on parameters of the temporary reference center position correction function, the reference center position correction function is a function representing the deviation of the sample rotation axis with respect to the central axis in the detector plane of the main imaging data, and correcting the main imaging data or the projection image based on the main imaging data using the reference center position correction function and the relative motion correction function.
12 . A non-transitory computer readable recording medium having recorded thereon a program for correcting artifacts due to motion during CT image measurement, the program causing a computer to execute the processes of: acquiring main imaging data scanned by 360° and reference imaging data; converting the main imaging data and the reference imaging data into projection images; aligning the projection image based on the reference imaging data and the projection image based on the main imaging data corresponding to an imaging angle of the reference imaging data and calculating a relative motion correction value respectively for the imaging angle; generating a relative motion correction function for correcting a relative motion of all the main imaging data or all the projection image based on the main imaging data based on the calculated relative motion correction value; setting a temporary reference center position correction function which is a function that assumes a deviation of a sample rotation axis with respect to a central axis in a detector plane of the main imaging data; temporarily correcting the projection image based on the main imaging data with the temporary reference center position correction function and the relative motion correction function; acquiring the temporarily corrected projection image calculating a degree of coincidence between the temporarily corrected projection image and the projection image at the imaging angle opposing thereto; determining a reference center position correction function based on parameters of the temporary reference center position correction function, the reference center position correction function is a function representing the deviation of the sample rotation axis with respect to the central axis in the detector plane of the main imaging data, and correcting the main imaging data or the projection image based on the main imaging data using the reference center position correction function and the relative motion correction function.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present application claims priority under Japanese Patent Application No. 2022-105801, filed on Jun. 30, 2022, the entire contents of which are incorporated by reference in this application. BACKGROUND Field The present disclosure relates to a correction apparatus, system, method and program for correcting an artifact. Description of the Related Art A CT apparatus reconstructs a CT image from a plurality of acquired imaging data acquired while rotating a sample or a gantry. In a CT apparatus, the movement of a sample or an optical system during a measurement is called motion. When imaging data with the motion are reconstructed without being corrected, blurs and streaky artifacts occur in the reconstructed CT image. Therefore, since the reconstructed image does not accurately reflect the shape of the sample, the quantitativity is lost. In order to reduce such artifacts due to motion, imaging by introducing an apparatus other than a CT apparatus, corrections by devising an imaging method, or software have been conventionally performed. Patent Document 1 discloses a technique of a deviation correction apparatus of an acquired image that corrects a deviation of an acquired image caused by a positional deviation of a imaging mechanism that irradiates a sample with radiation and captures a radiation image including transmitted radiation, wherein a plurality of radiation images obtained by capturing a sample image from a plurality of directions in a state in which a positional deviation of the imaging mechanism can occur are acquired, the radiation image is corrected in a coordinate axis direction of a predetermined coordinate system, a reconstruction calculation is executed based on the corrected radiation images, and an evaluation process for evaluating the quality of the obtained reconstruction information is repeated until the evaluation is highest, a reference image acquisition means that acquires radiation images generated in advance as a plurality of reference images showing a radiation image of a sample in a state in which a positional deviation of the imaging mechanism does not occur, a correction target image acquisition means that acquires a plurality of radiation images obtained as correction target images by capturing a sample in a state in which a positional deviation of the imaging mechanism can occur, and a correction section that corrects a correction target image in a coordinate axis direction of a predetermined coordinate system so that a degree of coincidence between corresponding images of the correction target image and the reference image is maximized. Patent Document 2 discloses a technique of an X-ray tomography apparatus in which a tomographic image obtained by a reconstruction calculation using X-ray projection data in each projection direction acquired by an X-ray detector is forward-projected in the same direction as the projection direction, a deviation between the forward projection data and the acquired projection data is obtained, the projection data acquired based on the deviation is corrected, and a clear tomographic image with little influence can be obtained by performing a new reconstruction calculation regardless of the inaccuracy of the relative rotation between the pair of the X-ray generator and detector and the object. Non-Patent Document 1 discloses a technique for by performing a first normal scan and a second coarse and quick scan, assuming no motion during the second quick scan, using a projection image of the second scan as a reference to correct a projection image obtained by the first measurement. In addition, Non-Patent Document 1 discloses a technique of gradually and precisely estimating a motion in repetition of projection and backprojection. Patent Documents Patent Document 1: JP-Patent No. 6383707Patent Document 2: JP-A-2010-181153 Non-Patent Document Non-patent Document 1: Developments in X-Ray Tomography VI, edited by Stuart R. Stock, Proc. of SPIE Vol. 7078, 70781C, (2008)⋅0277-786X/08/$18⋅doi: 10.1117/12.793212 “Compensation of mechanical inaccuracies in micro-CT and nano-CT” However, in the techniques described in both of Patent Document 1 and Patent Document 2, the correction is performed using reconstructed images, thereby requiring calculation cost. In addition, in the technique of measuring twice among the techniques described in Non-Patent Document 1, some motions still remain even when the measurement is performed quickly, and for example, a motion or the like based on a tolerance error derived from a rotation axis cannot be corrected. Among the techniques described in Non-Patent Document 1, a technique of sequentially estimating a motion requires repetition of projection calculation and backprojection calculation, thereby requiring calculation cost. SUMMARY The present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide a correction apparatus, syst