CN105469366B - A kind of analytic method of abatement CT image metal artifacts - Google Patents
A kind of analytic method of abatement CT image metal artifacts Download PDFInfo
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- 229910052751 metal Inorganic materials 0.000 title claims abstract description 72
- 239000002184 metal Substances 0.000 title claims abstract description 72
- 238000004458 analytical method Methods 0.000 title claims abstract description 10
- 238000000034 method Methods 0.000 claims abstract description 29
- 238000001228 spectrum Methods 0.000 claims abstract description 19
- 238000004422 calculation algorithm Methods 0.000 claims description 7
- 229910052704 radon Inorganic materials 0.000 claims description 7
- SYUHGPGVQRZVTB-UHFFFAOYSA-N radon atom Chemical group [Rn] SYUHGPGVQRZVTB-UHFFFAOYSA-N 0.000 claims description 7
- 239000011159 matrix material Substances 0.000 claims description 4
- 230000009466 transformation Effects 0.000 claims description 2
- 238000002591 computed tomography Methods 0.000 description 10
- 238000012937 correction Methods 0.000 description 6
- 238000003759 clinical diagnosis Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000003709 image segmentation Methods 0.000 description 3
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- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 238000002513 implantation Methods 0.000 description 2
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- 210000000214 mouth Anatomy 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 241000208340 Araliaceae Species 0.000 description 1
- 229910000645 Hg alloy Inorganic materials 0.000 description 1
- 235000005035 Panax pseudoginseng ssp. pseudoginseng Nutrition 0.000 description 1
- 235000003140 Panax quinquefolius Nutrition 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 235000008434 ginseng Nutrition 0.000 description 1
- 239000007943 implant Substances 0.000 description 1
- 238000001727 in vivo Methods 0.000 description 1
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- 150000002739 metals Chemical class 0.000 description 1
- 238000010606 normalization Methods 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 108010048734 sclerotin Proteins 0.000 description 1
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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
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/10—Image acquisition modality
- G06T2207/10072—Tomographic images
- G06T2207/10081—Computed x-ray tomography [CT]
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Abstract
A kind of analytic method for abatement CT image metal artifacts that the present invention provides, this method avoid interative computations.The present invention includes being partitioned into metal image in the image that data for projection is rebuild in the case of by multi-power spectrum ray, seek its projected image, find the approximation of energy spectrum function, obtain the expression formula of artifact function, artifacts are obtained, it is as shown in the picture that the image after artifacts are corrected is subtracted by original image.It is a feature of the present invention that remaining the structure feature of original information while eliminating banding artifact, and the priori of power spectrum and original data for projection are not needed in bearing calibration, it is fast to rebuild speed.
Description
Technical field
The invention mainly relates to medical X-ray Computed tomographies（Computed Tomography, abbreviation CT）
Field is specifically related in medicine CT detection imaging, when detected human body a part（Such as oral cavity, thoracic cavity etc.）Implantation
When metal object, there are metal artifacts situations for the CT images of reconstruction.
Background technology
CT detects the acquisition object faultage image that imaging technique can be lossless, and being played in medicine auxiliary diagnosis can not replace
In the ideal case, the data for projection that the scanning system of CT equipment measures is substance linear attenuation coefficient to the important function in generation
The reconstructing system of line integral, CT equipment carries out image reconstruction with the line integral data, and acquisition can be used for what clinical diagnosis used
CT images however in practical CT scan, the data for projection that system obtains generally comprises various errors, such as metal object causes
Error, this can lead to occur artifact in reconstruction image, reduce picture quality, seriously affect the metal in diagnostic result human bodies
Implantation material usually has intraoral tooth filling, in vivo operation folder and joint prosthesis etc., these metal objects have highly attenuating property,
When directly reconstructing CT images by data for projection, radial or banding artifact etc. is will appear in reconstruction image, is generally called gold
Belong to artifact
The case where being frequently encountered in actual CT scan comprising metal object, such as oral cavity CT scan is because of metal artifacts
Complex genesis, and the material of metal and geomery can directly result in metal artifacts in image power it is different with distribution,
Although therefore having some data and patent about metal artifacts school removing method at present, still without a kind of more common
Elimination or abatement metal artifacts the metal artifacts reduction softwares for orthopaedics released even for Philip of method,
A variety of situations can not also be provided with satisfactory correction result therefore, research and develop some blanket metal artifacts abatements
Method have very important significance for Medical CT system
Metal artifacts reduction (Metal artifact reduction, MAR) algorithm is broadly divided into interpolation method, projection school
Just, the methods of iterative approximation, the bearing calibration based on prior image and composed correction also have many metal artifacts schools in recent years
The patent of positive aspect, such as：
It is disclosed by the Chinese patent CN103190928A of Siemens application a kind of for reducing CT picture numbers
According to method this method of metal artifacts in group by first CT image data set of the reconstruction through metal artifacts reduction and without gold
Belong to the 2nd CT image data sets of artifact correction, and the such as data weighting method are utilized
The Chinese patent CN103186889A applied by GE companies of the U.S. discloses a kind of for reducing in medical image
Method and apparatus this method of metal artifacts consider same tomography and meanwhile comprising have various sizes of big metal object and
The artifact that small metal object generates handles big metal object and small metal object in same faultage image and generates in different ways
Artifact
Chinese patent CN103679642A discloses a kind of CT image metal artifacts bearing calibration, device and CT equipment, should
Method determines metal shadowing's range caused by objects interfered according to the corresponding original image of Raw projection data, is then based on successively
Metal shadowing's data within the scope of metal shadowing obtain the diagnosis Object Projection data after removing objects interfered and establish illustraton of model
Picture；Secondary correction, reconstruction are carried out to the Raw projection data further according to the data for projection of model image, it is pseudo- to obtain no metal
The target image of shadow
Chinese patent CN103745440A discloses a kind of CT system metal artifacts reduction method, and basis is initial in this method
Change parameter and create the coefficient matrix of the CT system, based on the system matrix computation CT image reconstructions during object decline
Subtract coefficient f, object attenuation coefficient f described in re-optimization realizes the metal artifacts reduction to CT system
Chinese patent CN103440636A discloses a kind of metal artifacts removing method of CT system, and this method passes through a system
Column data processing operation obtains new CT scan data, and then reconstruction image simultaneously becomes high pressure and low pressure CT scan again
It changes, to realize the reduction of calculation amount
Above-mentioned technology has been related to various metals artifact correction method, but all no method and algorithm are related to metal artifacts
Analytical Expression The present invention gives it is a kind of it is effective removal CT image metal artifacts analytic method, avoid iteration meter
It calculates, saves reconstruction time.
Invention content
Present invention is generally directed to metal artifacts problems common in Medical CT, it is proposed that a kind of effective removal metal
The analytic method of artifact
The invention is realized by the following technical scheme：
Cut down CT image metal artifacts analytic method, include mainly：CT scan system obtains detected object firstf (x) data for projection, then by CT reconstructing systems carry out image reconstruction, metal object is partitioned into from reconstruction image, then to metal
Object carries out reprojection, handles the data for projection, then rebuild to obtain artifacts, is finally subtracted from original image
Artifacts obtain target image, that is, the image after correcting while eliminating banding artifact it is characterized in that, remain original
There is the structure feature of information；The priori of X-ray energy spectrum and original data for projection are not needed in bearing calibration
Obtain the data for projection of the detection objectP, this data is obtained in multi-power spectrum ray；
Obtain the CT imagesP, from data for projection CT image reconstructionf E ,EIt is the energy parameter of ray；
The metal object image is obtained, Threshold segmentation is passed through（The threshold value generally used is 3000HU）Or level set side
Method goes out the image of metal object from the CT image segmentations of reconstruction；
The data for projection for obtaining the image of the metal object obtains its data for projection using projection matrix, i.e., it
Radon converts R Ψmetal；
The metal artifacts image is obtained, the approximate function of power spectrum is designedASin (ω (E+)), the artifact table of proposition
Up to formulaK=R -1 (P-Rf E0)=-R -1(ln(π2cosh(ρRΨmetal)/(π2+4ρ2(RΨmetal)2))) to handling data R Ψmetal,
Then it is rebuild, obtains the approximate image of artifactK,f E0It assumes that in some energyE 0Under object function, ρ is parameter,
ΨmetalIt is the characteristic function of metallic region；
It is the image after correcting to obtain the target imagef E0, former reconstruction imagef E Subtract artifactsK(x) obtainf E0.
The present invention relates to a kind of method of new abatement CT image metal artifacts, this method directly obtains image artifacts
Image, compared with previous metal artifacts reduction method, beneficial effects of the present invention have largely effective：（1）Eliminate band-like puppet
The structure feature of original information is remained while shadow；（2）Priori without ray energy spectrum；（3）It is not necessarily in bearing calibration
Original data for projection；（4）Using analytic reconstruction method, it is fast to rebuild speed.
Description of the drawings
Fig. 1 is the improved two-dimentional lower jaw Voxel Phantom used in embodiment；
Fig. 2 is the original image rebuild；
Fig. 3 is the artifacts rebuild；
Fig. 4 is the CT images after correction.
Specific implementation mode
Invention broadly provides a kind of methods of abatement CT image metal artifacts, including obtain data for projection, image weight
It builds, divide metal objects, reprojection, data processing, artifacts are rebuild and the image targets after being corrected are cancellation band
Shape artifact retains the structure feature of original information, obtains high-resolution CT images, more accurate information is provided for clinical diagnosis
Embodiments of the present invention：The data for projection under multi-power spectrum is obtained first and carries out image reconstruction；Then image segmentation is carried out to obtain
To the image of metal objects, and its Radon is asked to convert；Data are converted by the analytic method of proposition to the Radon to handle,
And treated data are rebuild, obtain artifacts；The CT images after artifacts are corrected are subtracted by original image；Finally
Embodiment is provided to be as follows：
(1) original CT image is obtained
The data for projection obtained under multi-power spectrum X-ray is scanned to detected object, with FBP algorithms or BPF algorithms
Reconstructed projection data obtains original CT image, and metal artifacts is contained in the image
(2) data for projection of metal image is obtained
Image segmentation usually is carried out to original image using threshold method, obtains metal image, the threshold generally used herein
Value is 3000HU；Then the data for projection of metal image is obtained again
(3) artifacts are obtained
The approximation for first looking for energy spectrum function provides the approximate expression of artifact function, obtains determining artifact function
Since energy spectrum diagram is unknown in practical CT scan system, therefore approximate function, the approximation energy can only be found according to its common characteristic
The function of spectrum should meet：Integral is 1. for example in energy range：Approximate function can select rectangular function, SIN function,
Cosine function or other approximate function are according to the feature of energy spectrum diagram, and SIN function is close to energy spectrum function by being designed with
Related parameter can obtain the approximate expression of artifact functionK=R -1 (P-Rf E0) by the expression formula to the projection in step 2
Data are handled；Then Radon inverse transformations are asked, are realized here with FBP or BPF algorithms, to obtain artifacts
Wherein there is related parameter that can seek its optimal solution using certain regularization methods
(4) the CT images after being corrected
The CT images after artifacts are corrected in step 3 is subtracted by the original image in step 1
(5) embodiment
The present embodiment selection is improved two-dimentional lower jaw Voxel Phantom, including 512 × 512 pixels, the ruler of each pixel
Very little is 0.5mm × 0.5mm, and sclerotin ingredient and soft tissue in the as shown in Figure 1 body moulds etc. are all in accordance with No. ICRU44 report ginseng
Number setting, their x-ray attenuation coefficient is obtained by XCOM softwares, and implants 3 mercury alloy object
The example is using we used the related systems of multi-power spectrum X-ray in body mould generation artificial projections data emulation
Parameter is as follows：X radiographic sources are 1100mm with rotation center distance, and X radiographic sources and detector distance are 1600mm, detector list
The length of member is the data for projection that 0.87. generates the die body using the equidistant fan beam CT scan pattern of Circular test, wherein detector
Unit number is that 512,360 degree of full scan projection angle numbers are 660.
Image is directly reconstructed by data for projection according to step 1 in embodiment, there are the obviously artifacts such as band-like in figure, seriously
Influence clinical diagnosis, as shown in Figure 2
According to step 2 in above embodiment, selected threshold 3000HU is split the image in Fig. 2, then profit
It is converted with Radon and obtains its data for projection
It is 0.01-1.2Kev to choose voltage range according to step 3 in above embodiment, in the example, and simulation process makes
With normalization energy spectrum diagram choose power spectrum approximate function π sin (π (E-E0+h)/(2h))/(4h), whereinE0 is some energy
Amount, h is an adjustable parameter；In this exampleE0=0.65Kev,h=0.55Kev. is according to artifact expression formula-R -1(ln(π2cosh(ρRΨmetal)/(π2+4ρ2(RΨmetal)2))) to obtain artifacts as shown in Figure 3, it can be seen that the figure is band in Fig. 2
The presentation of shape artifact, wherein the parameter optimized chooses ρ=2.31.
According to step 4 in the above embodiment, original reconstruction image subtracts the image after artifacts are corrected, and such as schemes
Shown in 4.
Claims (3)
1. a kind of analytic method of abatement CT image metal artifacts, which is characterized in that include the following steps：
(1) the data for projection P for obtaining detected object carries out image reconstruction by CT reconstructing systems, obtains original CT image fE, E is
The energy parameter of ray；
(2) it is partitioned into the image of metal object from reconstruction image, reprojection is carried out to the image of metal object, obtains metal object image
Data for projection；
(3) data for projection of metal object image is handled, then is rebuild to obtain artifacts：
With the approximate function that SIN function A sin (ω (E+ ψ)) are X-ray energy spectrum, pass through the approximate expression pair of artifact function
The data for projection of metal object image is handled, and is then rebuild, and the approximate image K of artifact is obtained,
The approximate expression of the artifact function is：
Wherein：R is Radon transformation；R-1It is inverse Radon transform；It assumes that in some ENERGY E0Under object function；Ψmetal
It indicates the characteristic function of metallic region, is 1 in region, other are 0；ρ is the parameter calculated using regularization method；
(4) with step (1) the original CT image fESubtract the approximate image K of step (3) artifact, you can the CT after being corrected
Image.
2. the analytic method of abatement CT image metal artifacts according to claim 1, it is characterised in that：From multi-power spectrum ray
The data for projection of acquisition carries out image reconstruction by FBP algorithms or BPF algorithms, which contains metal artifacts.
3. the analytic method of abatement CT image metal artifacts according to claim 1, it is characterised in that：Utilize threshold method
It is partitioned into metal image from reconstruction image, and finds out the data for projection of metal image using projection matrix.
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| JP2017221339A (en) * | 2016-06-14 | 2017-12-21 | 国立大学法人信州大学 | X-ray CT image reconstruction method and computer program |
| CN106485680B (en) * | 2016-10-13 | 2017-11-28 | 上海联影医疗科技有限公司 | Method for correcting image and device |
| EP3398515B1 (en) * | 2017-05-03 | 2020-06-24 | Siemens Healthcare GmbH | Adaptive method for generating of ct image data with reduced artefacts, as well as image reconstruction unit and corresponding computer program product. |
| EP3582184B1 (en) * | 2018-06-13 | 2021-11-03 | Siemens Healthcare GmbH | Multi-energy metal artefact reduction |
| CN109146994B (en) * | 2018-09-17 | 2023-06-20 | 南京航空航天大学 | Metal artifact correction method for multi-energy spectrum X-ray CT imaging |
| CN111110260B (en) * | 2019-12-24 | 2023-09-26 | 沈阳先进医疗设备技术孵化中心有限公司 | Image reconstruction method and device and terminal equipment |
| CN111415315B (en) * | 2020-03-17 | 2023-09-26 | 无锡鸣石峻致医疗科技有限公司 | Radial acquisition diffusion weighted imaging motion artifact correction method |
| WO2023178527A1 (en) * | 2022-03-22 | 2023-09-28 | 中国科学院深圳先进技术研究院 | Generation method and generation apparatus for tumor radiotherapy region |
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| CN101777177A (en) * | 2009-12-29 | 2010-07-14 | 上海维宏电子科技有限公司 | Attenuation filter-based metal artifact removing mixed reconstruction method for CT images |
| CN102567958A (en) * | 2010-12-31 | 2012-07-11 | 东软飞利浦医疗设备系统有限责任公司 | Image postprocessing method for removing metal artifact from computed tomography (CT) image |
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| US8971605B2 (en) * | 2012-08-23 | 2015-03-03 | General Electric Company | System and method for correcting for metal artifacts using multi-energy computed tomography |
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| CN101777177A (en) * | 2009-12-29 | 2010-07-14 | 上海维宏电子科技有限公司 | Attenuation filter-based metal artifact removing mixed reconstruction method for CT images |
| CN102567958A (en) * | 2010-12-31 | 2012-07-11 | 东软飞利浦医疗设备系统有限责任公司 | Image postprocessing method for removing metal artifact from computed tomography (CT) image |
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