CN110310346A - A kind of metal artifacts reduction method in CT and CBCT image - Google Patents
A kind of metal artifacts reduction method in CT and CBCT image Download PDFInfo
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- 239000002184 metal Substances 0.000 title claims abstract description 101
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 98
- 238000000034 method Methods 0.000 title claims abstract description 27
- 238000007408 cone-beam computed tomography Methods 0.000 title claims abstract description 25
- 230000009467 reduction Effects 0.000 title abstract description 4
- 238000012937 correction Methods 0.000 claims abstract description 24
- 230000004927 fusion Effects 0.000 claims description 11
- 238000003384 imaging method Methods 0.000 claims description 9
- 238000002474 experimental method Methods 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 3
- 238000013507 mapping Methods 0.000 claims description 3
- 238000010606 normalization Methods 0.000 claims description 3
- 238000004321 preservation Methods 0.000 claims description 3
- 238000007499 fusion processing Methods 0.000 claims description 2
- 230000008569 process Effects 0.000 claims description 2
- 238000002591 computed tomography Methods 0.000 description 18
- 239000007943 implant Substances 0.000 description 3
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 238000007500 overflow downdraw method Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
Classifications
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T5/00—Image enhancement or restoration
- G06T5/50—Image enhancement or restoration by the use of more than one image, e.g. averaging, subtraction
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T11/00—2D [Two Dimensional] image generation
- G06T11/003—Reconstruction from projections, e.g. tomography
- G06T11/008—Specific post-processing after tomographic reconstruction, e.g. voxelisation, metal artifact correction
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
- Y02P90/30—Computing systems specially adapted for manufacturing
Abstract
The present invention provides a kind of metal artifacts reduction methods in CT and CBCT image, comprising: remove from reconstruction image after rebuilding and dividing metallic region to Raw projection data, not corrected and metal-free original image；Linear interpolation correction is carried out to original projection, obtains linear interpolation correction image；The original image for removing metal and linear interpolation correction image co-registration are obtained into prior image, and forward projection is carried out to prior image and obtains priori perspective view；Priori perspective view is obtained on graph cut to original projection figure to correction perspective view in metallic region；Rebuild to obtain the image after the metallic region that metal-free correction image will be partitioned into again backfills to obtain metal artifacts reduction to correction perspective view.The present invention had both reduced the metal artifacts in CT and CBCT image, continuity of the sinogram after in turn ensuring correction in metal boundary region, it is possible to reduce the secondary artifact in reconstruction image.
Description
Technical Field
The invention belongs to the technical field of computer image processing, relates to an X-ray Computed Tomography (CT) technology and a Cone Beam Computed Tomography (CBCT) technology, and particularly relates to a correction method for a reconstructed CT or CBCT image under the condition of metal artifacts when a detected object contains metal implants in CT and CBCT detection imaging.
Background
CT and CBCT scanning are currently important examination methods, but when high-density metal objects exist in an object to be detected, X-rays passing through the metal objects are sharply attenuated, and corresponding measured data are subjected to amplitude jump, and an ideal CT/CBCT image can be reconstructed only by a conventional Filtered Back Projection (FBP)/FDK (named by Feldkamp-Davis-Kress) algorithm under the condition that Projection data are complete and continuous. Therefore, there is a metal artifact in the reconstructed image when metal is present in the object to be examined.
There are many Metal Artifact Reduction (MAR) methods, and the mainstream methods can be roughly classified into three major categories: projection data correction methods, iterative reconstruction methods, and hybrid methods. The projection data correction method is simple in principle, easy to implement, high in calculation speed and high in application value. However, the method is easy to introduce secondary artifacts, and particularly, the discontinuity of the boundary information of the metal region in the projection map can be caused by adopting an interpolation patching strategy to correct the missing information in the projection map, so that the secondary artifacts are aggravated.
Disclosure of Invention
Aiming at the problem that secondary artifacts are easily introduced by a projection data correction method in a metal artifact elimination method, the invention provides a method for correcting the metal artifacts in CT and CBCT images, which solves the problem that the discontinuity of a corrected projection image is caused by the conventional scheme and reduces the secondary artifacts.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for correcting metal artifacts in CT and CBCT images comprises the following steps:
step 1, original projection data PorginReconstructing and segmenting a metal region omega in an imageI_metalRemoving the metal region from the reconstructed image to obtain an uncorrected and metal-free original image Ia；
Step 2, the original projection P is processedorginPerforming linear interpolation correction to obtain a linear interpolation corrected image Ipre_LI；
Step 3, removing the original image I of the metal obtained in the step 1aAnd the linear interpolation correction image I obtained in step 2pre_LIThe prior image I is obtained by fusionpriorAnd forward projecting the prior image to obtain a prior projection image Pprior；
Step 4, the prior projection image PpriorIn the projected metal region omegap_metalInterpoisson fusion to original projection PorginTo obtain a corrected projection view Pcorrect；
Step 5, reconstructing the corrected projection drawing obtained in the step 4 to obtain a corrected image I without metalcorrect_no_metalThe metal region omega divided in step 1 is dividedI_metalFill back to image Icorrect_no_metalObtaining a metal artifact corrected image Icorrect。
Further, the step 2 specifically includes the following steps:
area range omega of metal in image spaceI_metalMapping to a projection space to obtain a metal range omega in the projection spacep_metal；
Raw projection data PorginAt omegap_metalThe images within the range are replaced by linear interpolation data to obtain metal-free projection data PLI_MAR；
To PLI_MARReconstructing to obtain an image ILI_MARThen to ILI_MARCarrying out mean value filtering with edge preservation to obtain a linear interpolation correction image Ipre_LI：
Wherein v represents the size of the selected neighborhood, N represents the number of non-zero pixels in I, and I is defined as follows:
wherein T is a threshold value.
Further, the fusion in step 3 comprises the following processes:
after sample learning, the following fusion mode is selected:
Iprior(i，j)＝w(i，j)×Ia(i，j)+[1-w(i，j)]×Ipre_LI(i，j)
in the formula, w (i, j) is a weight coefficient and is expressed as follows:
whereinnor (. cndot.) represents normalization; the value of d is selected by experiments.
Further, the poisson fusion process in the step 4 is to solve the following equation:
wherein,denotes the gradient of f, V is the metal region omegap_metalInner prior projection map PpriorThe omega is the metal area omegap_metal。
Further, the reconstruction method is as follows:
if the imaging mode is CT, performing FBP reconstruction on the original projection data; and if the imaging mode is CBCT, performing FDK reconstruction on the original projection data.
Compared with the prior art, the invention has the following advantages and beneficial effects:
the invention is different from the conventional method that the value of the original projection image in the metal area is replaced by the prior projection image, and the prior projection image is Poisson fused into the original projection image in the metal area, thereby not only reducing the metal artifact in the CT and CBCT images, but also ensuring the continuity of the fused sinogram in the metal boundary area and reducing the secondary artifact in the reconstructed image.
Drawings
Fig. 1 is a schematic flow chart of a method for correcting metal artifacts in CT and CBCT images according to the present invention.
Detailed Description
The technical solutions provided by the present invention will be described in detail below with reference to specific examples, and it should be understood that the following specific embodiments are only illustrative of the present invention and are not intended to limit the scope of the present invention.
The invention provides a method for correcting metal artifacts in CT and CBCT images, the flow of which is shown in figure 1, and the method comprises the following steps:
step 101, for the original projection data PorginReconstructing and segmenting a metal region omega in an imageI_metalAnd removing the metal region from the reconstructed image to obtain an uncorrected metal-free original image Ia。
In the step, if the imaging mode is CT, FBP reconstruction is carried out on the original projection data; if the imaging mode is cone beam CT, namely CBCT, FDK reconstruction is carried out on the original projection data. The reconstructed image is Iinit。
When the metal area is divided, according to a set threshold DmetalFrom IinitIn which a metal image I is dividedmetalObtaining the metal region omega in the imageI_metalRemoving the metal area image from the reconstructed image to obtain an uncorrected original image Ia(ii) a The threshold value for segmenting the metal region is a value obtained through sample learning and experiments. For example, after learning through a certain set of samples, the value may be 2000HU, etc.
102, projecting P onto the original projectionorginPerforming linear interpolation correction to obtain a linear interpolation corrected image Ipre_LI。
In this step, the step of linear interpolation correction includes:
area range omega of metal in image spaceI_metalMapping to a projection space to obtain a metal range omega in the projection spacep_metal；
Raw projection data PorginAt omegap_metalThe images within the range are replaced by linear interpolation data to obtain metal-free projection data PLI_MAR；
To PLI_MARPerforming FBP (corresponding to CT) or FDK (corresponding to CBCT) reconstruction to obtain image ILI_MARThen to ILI_MARCarrying out mean value filtering with edge preservation to obtain a linear interpolation correction image Ipre_LI：
Wherein v represents the size of the selected neighborhood, N represents the number of non-zero pixels in I, and I is defined as follows:
wherein T is a threshold value.
The values of v and T are values obtained through sample learning and experiments. For example, after learning through a certain set of samples, the values may be: v is 30, T is 300HU, etc.
Step 103, fusing the original reconstructed image without metal obtained in the step 101 and the linear interpolation correction image obtained in the step 102 to obtain a prior image IpriorAnd forward projecting to obtain a priori projection image Pprior。
In this step, the image fusion mode can be selected through sample learning and experiments. For example, after sample learning, the following fusion method is selected:
Iprior(i，j)＝w(i，j)×Ia(i，j)+[1-w(i，j)]×Ipre_LI(i，j)
in the formula, w (i, j) is a weight coefficient and is expressed as follows:
whereinnor (. cndot.) represents normalization; the value of d is selected by experiments, for example: in the case that the metal implant in the detected object is small, d takes the value of a small value, such as 0.1; under the condition that the metal implant in the detected object is relatively large, the value of d is a larger value, such as 0.45;
step 104, a priori projection map PpriorIn the projected metal region omegap_metalInterpoisson fusion to original projection PorginTo obtain a corrected projection view Pcorrect。
In this step, the poisson fusion rule is to solve the following equation:
wherein,denotes the gradient of f, V is the metal region omegap_metalInner prior projection map PpriorThe omega is the metal area omegap_metal。
Step 105, reconstructing the corrected projection image to obtain a corrected image I without metalcorrect_no_metalThe metal region Ω divided in step 101 is dividedI_metalFill back to image Icorrect_no_metalObtaining a metal artifact corrected image Icorrect。
In the step, if the imaging mode is CT, FBP reconstruction is carried out on the original projection data; if the imaging mode is cone beam CT, namely CBCT, FDK reconstruction is carried out on the original projection data.
And the metal region backfill mode selects a linear fusion mode, a Poisson fusion mode and other fusion modes according to sample learning.
The technical means disclosed in the invention scheme are not limited to the technical means disclosed in the above embodiments, but also include the technical scheme formed by any combination of the above technical features. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and such improvements and modifications are also considered to be within the scope of the present invention.
Claims (5)
1. A method for correcting metal artifacts in CT and CBCT images is characterized by comprising the following steps:
step 1, original projection data PorginReconstructing and segmenting a metal region omega in an imageI_metalRemoving the metal region from the reconstructed image to obtain an uncorrected and metal-free original image Ia；
Step 2, the original projection P is processedorginPerforming linear interpolation correction to obtain a linear interpolation corrected image Ipre_LI；
Step 3, removing the original image I of the metal obtained in the step 1aAnd the linear interpolation correction image I obtained in step 2pre_LIThe prior image I is obtained by fusionpriorAnd forward projecting the prior image to obtain a prior projection image Pprior；
Step 4, the prior projection image PpriorIn the projected metal region omegap_metalInterpoisson fusion to original projection PorginTo obtain a corrected projection view Pcorrect；
Step 5, reconstructing the corrected projection drawing obtained in the step 4 to obtain a corrected image I without metalcorrect_nometalThe metal region omega divided in step 1 is dividedI_metalFill back to image Icorrect_nometalObtaining a metal artifact corrected image Icorrect。
2. The method for metal artifact correction in CT and CBCT images as claimed in claim 1, wherein said step 2 specifically comprises the following process:
area range omega of metal in image spaceI_metalMapping to a projection space to obtain a metal range omega in the projection spacep_metal；
Raw projection data PorginAt omegap_metalThe images within the range are replaced by linear interpolation data to obtain gold-free imagesProjection data P of genusLI_MAR；
To PLI_MARReconstructing to obtain an image ILI_MARThen to ILI_MARCarrying out mean value filtering with edge preservation to obtain a linear interpolation correction image Ipre_LI：
Wherein v represents the size of the selected neighborhood, N represents the number of non-zero pixels in I, and I is defined as follows:
wherein T is a threshold value.
3. The method for metal artifact correction in CT and CBCT images as claimed in claim 1, wherein said step 3 of fusing comprises the following steps:
after sample learning, the following fusion mode is selected:
Iprior(i，j)＝w(i，j)×Ia(i，j)+[1-w(i，j)]×Ipre_LI(i，j)
in the formula, w (i, j) is a weight coefficient and is expressed as follows:
wherein nor (. cndot.) represents normalization; the value of d is selected by experiments.
4. The method for correcting metal artifacts in CT and CBCT images according to claim 1, wherein the poisson fusion process in step 4 is to solve the following equation:
wherein ,denotes the gradient of f, V is the metal region omegap_metalInner prior projection map PpriorThe omega is the metal area omegap_metal。
5. The method for metal artifact correction in CT and CBCT images according to claim 1 or 2, wherein said reconstruction means is:
if the imaging mode is CT, performing FBP reconstruction on the original projection data; and if the imaging mode is CBCT, performing FDK reconstruction on the original projection data.
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Cited By (4)
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| CN111815521A (en) * | 2020-05-27 | 2020-10-23 | 南京国科医工科技发展有限公司 | Cone beam CT metal artifact correction algorithm based on prior image |
| CN113643393A (en) * | 2021-06-28 | 2021-11-12 | 南京邮电大学 | CBCT image metal artifact correction method based on guide map filtering |
| CN113781595A (en) * | 2021-08-26 | 2021-12-10 | 深圳市菲森科技有限公司 | Metal artifact removing method and system for oral cavity cone beam CT image |
| CN117830456A (en) * | 2024-03-04 | 2024-04-05 | 中国科学技术大学 | Method and device for correcting image metal artifact and electronic equipment |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111815521A (en) * | 2020-05-27 | 2020-10-23 | 南京国科医工科技发展有限公司 | Cone beam CT metal artifact correction algorithm based on prior image |
| CN111815521B (en) * | 2020-05-27 | 2024-02-13 | 南京国科精准医学科技有限公司 | Cone beam CT metal artifact correction algorithm based on priori image |
| CN113643393A (en) * | 2021-06-28 | 2021-11-12 | 南京邮电大学 | CBCT image metal artifact correction method based on guide map filtering |
| CN113643393B (en) * | 2021-06-28 | 2023-06-16 | 南京邮电大学 | CBCT image metal artifact correction method based on guide image filtering |
| CN113781595A (en) * | 2021-08-26 | 2021-12-10 | 深圳市菲森科技有限公司 | Metal artifact removing method and system for oral cavity cone beam CT image |
| CN113781595B (en) * | 2021-08-26 | 2024-03-08 | 深圳市菲森科技有限公司 | Method and system for removing metal artifact of oral cone beam CT image |
| CN117830456A (en) * | 2024-03-04 | 2024-04-05 | 中国科学技术大学 | Method and device for correcting image metal artifact and electronic equipment |
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