CN103679642B - A kind of CT image metal artifact bearing calibration, device and CT equipment - Google Patents

Abstract

The invention provides a kind of CT image metal artifact bearing calibration, device and CT equipment.CT image metal artifact bearing calibration determines, according to the original image that Raw projection data is corresponding, metal shadowing's scope that objects interfered causes；Obtaining the diagnosis Object Projection data after removing objects interfered based on the metal shadowing data in the range of metal shadowing successively, and based on described diagnosis Object Projection data after, Raw projection data is corrected and sets up model image；Data for projection according to model image carries out secondary correction to described Raw projection data, and based on the target projection data after correction according to the scanning used by clinic, build slice part and rebuild, obtain the target image not having metal artifacts, thus reach the purpose of calibration metal artifact.It is using Raw projection data as calibration object, it is ensured that the spatial resolution of the image after process and low contrast ability.And Raw projection data has completely included all of information of objects interfered, it is to avoid the artifact that introducing is new.

Description

A kind of CT image metal artifact bearing calibration, device and CT equipment

Technical field

The present invention relates to CT method for correcting image, particularly relate to a kind of CT image metal artifact bearing calibration, device and CT equipment.

Background technology

Computed tomography (ComputerizedTomography, it is called for short CT) it is a kind of for ray, to there is different attenuation properties based on different material, testee is irradiated from all directions with lonizing radiation, measure the transmitted intensity through object, and calculate the interior of articles each point material linear attenuation coefficient for ray by certain algorithm for reconstructing, thus obtain the radiodiagnostic techniques of the faultage image of testee.The faultage image that CT rebuilds has the advantages such as askiatic overlap, density and spatial resolution are high, thus occurs just receiving much concern as medical harmless diagnostic techniques from one.

Based on CT technology based on different material for the attenuation properties difference of ray and the principle of imaging, in actual mechanical process, some have the trap of high intensity such as highdensity materials such as metals for ray, directly result in CT data for projection and transition occur.Thus be included in and the position containing the high density material such as artificial tooth, artificial limb is scanned, the CT image after reconstruction just has containing light and dark metal artifacts, and these metal artifacts are large number of, and amplitude is high, has a strong impact on CT picture quality.Thus cause clinician cannot carry out clinical diagnosis accurately according to CT image.

Thus using in CT technology clinical diagnostic process, it is required for the CT image of shooting is made correction process, thus reduces the CT image at human diagnosis position.At present, the method that industry uses generally comprises:

1) CT iterative reconstruction approach, view field's data corresponding for metal are considered as missing data by the method, are iterated rebuilding according to a certain criterion.It can effectively remove metal artifacts, and presents metal object structure well, but iterative approximation operand is big, and image reconstruction speed is very slow, and clinical practice feasibility is little.

2) post-processing approach based on image area, the method carries out artifact correction using the image comprising metal artifacts as input picture, the technology of employing post processing of image.Its process includes using the method for image area orthographic projection (line integral) to simulate data for projection, then is filtered the data for projection that metallic region is corresponding processing, thus removes metal artifacts.The method image reconstruction speed, but the image after making process thickens, it is impossible to ensure the original resolution of image；And the method only can be to local correct image, the image that the most non-absolute visual field is rebuild, owing to these images often lost the physical message that metal is relevant, the image after reconstruction often enters new artifact, in turn results in mistaken diagnosis.

3) pre-treating method based on data for projection, the method is that the data for projection collecting detector processes, first have to carry out rim detection and identify the data for projection that metal is corresponding, then use the method for high-order interpolation or image co-registration that the data for projection that metal is corresponding is modified, but during this, the data for projection that metal is corresponding is difficult to be accurately positioned, and the image after the deviations of metal shadowing's part easily makes reconstruction introduces new artifact or changes original image information, again result in mistaken diagnosis, fail to pinpoint a disease in diagnosis.

Thus, the removal of metal artifacts hampers CT technology clinical diagnosis always and develops further, and it is also CT technical research emphasis and difficult point.

Summary of the invention

The invention provides a kind of CT image metal artifact bearing calibration, CT image metal artifact correcting unit and a kind of CT equipment, which overcome in existing CT image metal artifact alignment technique, metal shadowing's data are difficult to position, the defects such as revised image malleable original image information, are effectively improved CT image metal artifact and remove efficiency and accuracy.

For solving the problems referred to above, one CT image metal artifact bearing calibration of the present invention, including:

The Raw projection data being diagnosed object by the CT comprising objects interfered obtains original image, and extracts original metal image from described original image；

Obtain the metal shadowing data corresponding with described original metal image；

Raw projection data described in comparison and metal shadowing's data, obtain the diagnosis Object Projection data of the CT diagnosis object after removing objects interfered, based on Raw projection data described in described diagnosis Object Projection Data correction, obtain preliminary corrections data for projection；

Obtain the original calibration image that described preliminary corrections data for projection is corresponding；

Original image described in comparison and original calibration image, carry out figure correction to image difference region between the two, set up model image, and obtain the model image data that described model image is corresponding；

Again correct described Raw projection data with described model image data, obtain target projection data；

Corresponding target image is set up by described target projection data.

Alternatively, during being obtained original image by described Raw projection data, described preliminary corrections data for projection obtaining original calibration image and set up target image by described target projection data, at least one process uses filtered back-projection method.

Alternatively, the Raw projection data of the CT diagnosis object for comprising objects interfered uses the CT machine maximum scan visual field as rebuilding the visual field when being filtered back projection.

Alternatively, obtain the metal shadowing data corresponding with original metal image to include: described original metal image carries out orthographic projection based on frequency domain and processes, it is thus achieved that described metal shadowing data.

Alternatively, in original metal image carries out orthographic projection processing procedure based on frequency domain, after the resolution improving described original metal image, then carry out two-dimensional Fourier transform and one-dimensional inversefouriertransform successively.

Alternatively, obtain described preliminary corrections data for projection and include: described diagnosis Object Projection data are carried out linear interpolation correction, obtains interpolated projections data；Raw projection data described in comparison and described interpolated projections data, obtain described preliminary corrections data for projection.

Alternatively, described figure correction includes: be smoothed the differential image region of described original image with original calibration image.

Alternatively, in described figure makeover process, the differential image region of described original image Yu original calibration image is carried out repeatedly smoothing processing.

Alternatively, obtain diagnosis Object Projection data to include: after obtaining described metal shadowing data, described metal shadowing data are made orthographic projection, thus extracts metal shadowing region；And in described metal shadowing regional extent, on the basis of Raw projection data each described, eliminate the described metal shadowing data corresponding with described Raw projection data, obtain the diagnosis Object Projection data after removing objects interfered.

Alternatively, obtain target projection data to include: in described metal shadowing region, use Raw projection data described in described model image Data correction.

Alternatively, described image difference region is obtained by following manner: when original image described in comparison and original calibration image, is some corresponding regions by described original image with described original calibration image division respectively；Comparison corresponding region between the two, and extract the described image difference region of composition, corresponding region that cannot overlap between described original image with original calibration image.

Alternatively, described target projection data set up corresponding target image and include: using target projection data described in filtered back projection to set up described target image, wherein, rebuilding the visual field is the reconstruction visual field that clinical interface selects；Convolution kernel is the convolution kernel that clinical interface selects；Building inconocenter is the center that clinical interface is arranged.

Present invention also offers a kind of CT image metal artifact correcting unit, including:

Original image acquiring unit, the CT comprising objects interfered the Raw projection data diagnosing object obtains original image, and extracts original metal image from original image；

Fictitious data acquiring unit, obtains the metal shadowing data corresponding with original metal image；

First data correction unit, Raw projection data described in comparison and metal shadowing's data, obtain the diagnosis Object Projection data of the CT diagnosis object after removing objects interfered, based on Raw projection data described in described diagnosis Object Projection Data correction, obtain preliminary corrections data for projection；

Original calibration image acquisition unit, obtains the original calibration image that described preliminary corrections data for projection is corresponding；

Model image processing unit, original image described in comparison and original calibration image, carry out figure correction to image difference region between the two, set up model image, and obtain the model image data that described model image is corresponding；

Second data correction unit, again corrects described Raw projection data with described model image data, obtains target projection data；

Target image acquiring unit, is set up corresponding target image by described target projection data.

In addition, present invention also offers a kind of CT equipment including above-mentioned CT image metal artifact correcting unit.

Compared with prior art, CT image metal artifact bearing calibration of the present invention, device and CT equipment have the advantage that

CT image metal artifact bearing calibration of the present invention determines the metal shadowing's scope as objects interfered according to the original image that Raw projection data is corresponding；Obtain the diagnosis Object Projection data after removing objects interfered based on the metal shadowing data in the range of metal shadowing the most successively, and based on described diagnosis Object Projection data Raw projection data be corrected and set up model image；And at the data for projection finally according to model image, described Raw projection data is carried out secondary correction, afterwards based on the target projection data after correction according to the scanning used by clinic, build slice part and rebuild, obtain the target image not having metal artifacts, thus reach the purpose of calibration metal artifact.During it is whole, the present invention has abandoned and has obtained the processing mode of apparent image to being obtained the direct moditied processing of reconstruction image by initial data, in the present invention all using Raw projection data as calibration object, thus the spatial resolution of the image obtained by correction data after ensureing to process and low contrast ability.And Raw projection data has completely included all of information of objects interfered and has avoided the artifact situation that introducing is new, while it ensures to get rid of artifact, it is ensured that the resolution of image is not suffered a loss.

In alternative, metal image obtains metal shadowing data based on carrying out orthographic projection based on frequency domain at original metal image, which ensure that and obtains the accuracy of data simultaneously, nor affects on processing speed, add in CT image correction process, the practicality of clinical implementation.

Accompanying drawing explanation

Fig. 1 is a kind of embodiment schematic flow sheet of CT image metal artifact bearing calibration of the present invention；

Fig. 2 is the schematic flow sheet of CT a kind of specific embodiment of image metal artifact bearing calibration of the present invention；

Fig. 3 is the structural representation of CT image metal artifact correcting unit of the present invention.

Detailed description of the invention

Understandable for enabling the above-mentioned purpose of the present invention, feature and advantage to become apparent from, below in conjunction with the accompanying drawings the detailed description of the invention of the present invention is described in detail.

Elaborating a lot of detail in the following description so that fully understanding the present invention, but the present invention can also use other to be different from alternate manner described here to be implemented, therefore the present invention is not limited by following public specific embodiment.

The most as described in the background section, existing in CT image artifacts alignment technique, image resolution ratio after post-processing approach based on image area processes is low, cause after correction is image blurring, and trimming process often lost the physical message that metal is relevant, the image after reconstruction often enters new artifact；And pre-treating method of based on data for projection is in image correction process, the data of objects interfered are difficult to be accurately positioned, and cause the image after reconstruction introduce new artifact or change original image information.CT image after defect based on above-mentioned CT image artifacts alignment technique makes correction causes mistaken diagnosis, rate of missed diagnosis high.

One CT image metal artifact bearing calibration of the present invention overcomes above-mentioned existing CT image artifacts alignment technique defect, determines the metal shadowing's scope as objects interfered using the original image that Raw projection data is corresponding；Obtain the diagnosis Object Projection data after removing objects interfered based on the metal shadowing data in the range of metal shadowing the most successively, and based on described diagnosis Object Projection data Raw projection data be corrected and set up model image；And at the data for projection finally according to model image, described Raw projection data is carried out secondary correction；Afterwards based on the target projection data after correction according to the scanning used by clinic, build slice part and rebuild, obtain the target image not having metal artifacts, thus reach the purpose of calibration metal artifact.

During the present invention is whole to metal artifacts reduction, all using Raw projection data as calibration object, it is ensured that the spatial resolution of the image after process and low contrast ability.And Raw projection data of the present invention has completely included the Raw projection data of all of information of objects interfered as calibration object, it is to avoid the artifact situation that introducing is new.Use the described target image that the present invention obtains, effectively reduce the CT image of the diagnosis object after removing objects interfered, effectively reduce and cause mistaken diagnosis, rate of missed diagnosis.

With reference to shown in accompanying drawing 1, CT image metal artifact bearing calibration detailed process of the present invention includes:

Step S1: the Raw projection data being diagnosed object by the CT comprising objects interfered obtains original image；And from original image, extract original metal image, and obtain the metal shadowing's data corresponding to described original metal image.

Step S2: Raw projection data described in comparison and metal shadowing's data, obtains the diagnosis Object Projection data of the CT diagnosis object after removing objects interfered；Based on Raw projection data described in described diagnosis Object Projection Data correction, obtain preliminary corrections data for projection, and obtain the original calibration image that described preliminary corrections data for projection is corresponding.

Step S3: original image described in comparison and original calibration image, carries out figure correction to image difference region between the two, sets up model image；And obtain the model image data that described model image is corresponding.

Step S4: again correct described Raw projection data with described model image data, obtain target projection data；Thus obtain the target image corresponding with described target projection data.

Wherein, described objects interfered can cause all materials of metal artifacts by the high density material etc. including such as metal.

Below by combining with reference to Fig. 2, by specific embodiment, thus the present invention and advantages of the present invention are explained in more detail.

Step S1: the Raw projection data being diagnosed object by the CT comprising objects interfered obtains original image；And from original image, extract original metal image, and obtain the metal shadowing's data corresponding to described original metal image.

Specifically, first, the Raw projection data filtered back projection of the CT diagnosis object comprising objects interfered original image is obtained, wherein:

The CT comprising interferogram picture is diagnosed the Raw projection data P of object^O _p,n(P^O _p,nThe equidistant data for projection of parallel beam after resetting for isogonism) it is filtered back projection and obtains original image.

In specific implementation process, the parameter setting up described original image includes:

The reconstruction visual field F used_ovMaximum scan visual field F for CT machine_max, i.e. F_ov=F_max,

Convolution kernel used by filtered back projection is the convolution kernel K of standard resolution_std,

And build the center of rotation that inconocenter is CT machine, it may be assumed that and ReconCenter=(0,0).

The most described reconstruction visual field is the maximum scan visual field of CT machine, afterwards in CT original image trimming process, will not omit the CT original image information including metal artifacts image.Thus cause new artifact, and the diagnostic message of disappearance, less mistaken diagnosis, the probability failed to pinpoint a disease in diagnosis at CT image compared with timing.

Defining the reconstruction image obtained by above-mentioned reconstruction parameter is I^O _{X, y}, and size N*N of image array.

Then, from original image, original metal image is extracted: wherein, be I by described original metal image definition^M _xy。

I^M _x,y=I^O _x,y*f(I^O _x,y;t,w)；

Wherein, threshold value t and threshold width w are pre-set metal threshold value and metal threshold width.The two value depends on the filtration system of bulb, i.e. filters (head filtration, body filtration etc.) for difference and has different parameter values.

$f(z;a,b)=\left\{\begin{array}{cc}0,& \mathrm{ifz}<-\frac{b}{2}\\ {\sin }^2(\frac{\mathrm{\&pi;}}{2}\&times;\frac{z-(a-\frac{b}{2})}{b}),& \mathrm{ifa}-\frac{b}{2}\&le;z\&le;a+\frac{b}{2}\\ 1,& \mathrm{ifz}>a+\frac{b}{2}\end{array}\right\};$

Wherein, z is I^M _{X, y}, a be t, b be w.

Then, original metal image is carried out orthographic projection based on frequency domain, obtains metal shadowing's data.

Its orthographic projection process based on frequency domain includes:

The first step, by original metal image I^M _x,yThe CT value of each pixel be converted to the linear attenuation coefficient of correspondence, metal image I after conversion^μ _x,yRepresent；

I^μ _x,y=(I^M _x,y+ 1000)/HU_scale；

Wherein, HU_scaleDepend on the output voltage of X-ray bulb of system, the collimator width of system, filter, convolution kernel.

Second step, afterwards to metal image I obtained^μ _x,yCarrying out numerical values recited adjustment, the result after adjustment is usedRepresent；

${{\tilde{I}}^{\mathrm{\&mu;}}}_{x,y}=\frac{{F_{\max }}^2}{d\&times;N^2}\&times;{I^{\mathrm{\&mu;}}}_{x,y};$

Wherein, d is the physical separation size of equidistant parallel beam projection.

3rd step, the image after adjustingIt is extended；

As, after extension, the size of image is original four times, and the image E of extension represents, extension formula is:

$E_{((x+\mathrm{\&Delta;})\mathrm{mod}2N_I,(y+\mathrm{\&Delta;})\mathrm{mod}2N_I)}={{\tilde{I}}^{\mathrm{\&mu;}}}_{x,y};$

Wherein X=0,1 ..., N-1, Y=0,1 ..., N-1, Δ=(3/2) N, wherein, N is pixel number.

Do not indexed corresponding value by the subscript of E defined in above-mentioned formula and be set to 0.

It should be noted that 4 times that image spreading is original size in the present embodiment, in practical operation, can the most specifically determine extension size.

4th step, to E_x,yCarrying out two-dimensional Fourier transform, its result is usedRepresent；

After the extension of above-mentioned 3rd step image, can be to E_x,yWhen carrying out two-dimensional Fourier transform, implant enough interpolation to image spatial domain signal, thus ensure the precision of two-dimensional Fourier transform, improve the frequency resolution of two-dimensional Fourier transform.

5th step, frequency interpolation, obtainPolar coordinate frequency-domain expression

Wherein, the frequency domain interval of rectangular coordinate is:

${\mathrm{\&Delta;\&omega;}}_I=\frac{1}{2F_{\max }};$

Polar frequency domain interval is:

${\mathrm{\&Delta;\&omega;}}_P=\frac{1}{d\&times;N_{\mathrm{FFT}}};$

Wherein, N_FFTThe length of convolution in rebuilding for filtered back projection in step S1.And for polar each point (p, value n)Value around cubic(cubic polynomial) interpolation.

Wherein for each projection angle:

${\mathrm{\&upsi;}}_p={\mathrm{\&upsi;}}_o+p\&times;\frac{2\mathrm{\&pi;}}{N_{\mathrm{p\&pi;}}};$

Wherein, p=0,1 ..., N_pπ-1, υ_oIt it is the start angle of first projection.

For each frequency indices:

N=0,1 ..., N_FFT-1；

By Interpolation Process above, for each projection angle p, obtain following sequential value:

${\tilde{E}}_{p,0},{\tilde{E}}_{p,1},{\tilde{E}}_{p,2},...{\tilde{E}}_{p,N_{\mathrm{FFT}}-1};$

6th step, for obtainCarry out deconvolution operation, obtain the Fourier transformation of the data for projection of each projection angle, i.e.

${\tilde{E}}_{p,n}=\frac{{\tilde{E}}_{p,n}}{K_{\mathrm{std}}};$

7th step, for obtained aboveCarry out one-dimensional inversefouriertransform, obtain data for projection P corresponding in spatial domain_{P, n}, i.e.

$P_{p,n}={\mathrm{FFT}}_{1D}^{-1}\left({\tilde{E}}_{p,n}\right);$

The metal shadowing's data obtained by above method are P^M _{P, n}。

In above-mentioned steps, metal image obtains metal shadowing data based on carrying out orthographic projection based on frequency domain at original metal image, which ensure that the data accuracy of acquisition simultaneously, it is ensured that processing speed, adds in CT image correction process, the practicality of clinical implementation.

Finally, determining metal shadowing region, it specifically includes:

For metal shadowing's data P^M _{P, n}；

Carry out multiple angle orthographic projection, and find out those successive ranges being not zero, and the successive range that these are not zero is exactly metal shadowing region, metal shadowing region ［ S_i, E_iRepresent.

Wherein, S_iFor the starting point in metal shadowing region, E_iFor the terminal in metal shadowing region, i=1,2 ..., k, wherein, k is the number of the successive range being not zero.

During above-mentioned orthographic projection, the geometric parameter SID(bulb focus used is to the distance of frame center of rotation), the distance of IDD(frame center of rotation to detector), the scan vision of SFOV(CT machine) numerical value be the physical geometry size that CT machine is corresponding, so that the geometric parameter used by orthographic projection is all consistent with the geometric parameter of actual machine scanning, ensure that the concordance of data, thus reach to correct the purpose of Raw projection data.

Step S2: Raw projection data described in comparison and metal shadowing's data, obtains the diagnosis Object Projection data of the CT diagnosis object after removing objects interfered；And based on Raw projection data described in described diagnosis Object Projection Data correction, obtain preliminary corrections data for projection, obtain the original calibration image that described preliminary corrections data for projection is corresponding.

First, if Raw projection data (data for projection corresponding to original image) is P^O _pn,

Raw projection data P^O _pnWith metal shadowing's data P^M _p,nDifference be P^D _p,n, i.e.

P^D _p,n=P^O _pn-P^M _p,n；

For each projection angle, in metallic region, difference data for projection is done linear interpolation, obtain interpolated projections dataThat is:

${\tilde{P}}_{p,k}^D={P^D}_{p,k}\frac{E-k}{E-S}+{P^D}_{p,k}\frac{k-s}{E-S};$

Wherein k ∈ (S, E).

Then, preliminary corrections Raw projection data P^O _{P, n}And obtain preliminary corrections data for projection, its process is as follows:

Each subpoint for each metal shadowing region；

If interpolated dataMore than difference data P^D _p,n, then amendment Raw projection data P^O _p,n, do not revise, i.e. preliminary corrections data for projection,

${{P_R}^O}_{p,k}=\left\{\begin{array}{cc}{P^O}_{p,k}+{{\tilde{P}}^D}_{p,k}-{P^D}_{p,k},& \mathrm{if}{{\tilde{P}}^D}_{p,k}>{P^D}_{p,k}\\ {P^O}_{p,k},& \mathrm{if}{{\tilde{P}}^D}_{p,k}\&le;{P^D}_{p,k}\end{array}\right\};$

Finally, according to the condition setting up original image with Raw projection data in step S1, to described preliminary corrections data for projection P_R ^O _p,kBeing filtered backprojection reconstruction, obtaining preliminary corrections image is I^C _{X, y}。

Step S3: comparison original image I^O _x,yWith preliminary corrections image I^C _x,ySet up and obtain model image:

Including: (1) comparison original image I^O _x,yWith preliminary corrections image I^C _x,yEstablishing target correction region, its process includes:

Pre-set two threshold values T₁And T₂, divide the image into A district, three regions, B district, C district according to the two threshold value.A position is less than T₁Pixel composition region, B district be between pixel composition region, C district is more than T₂Pixel composition region.

By original image I^O _x,yDetermine B district, be defined as goal-selling correcting area, simultaneously original image I described in comparison^O _x,yWith preliminary corrections image I^C _x,yA district and C district, and in the range of described A district and C district, described original image I^O _x,yWith preliminary corrections image I^C _x,yNonoverlapping part, and by these not lap be included into goal-selling correcting area, form target correction region.Now, described target correction region is probably a discontinuous region.

In the present invention, the definition territory T in described B district₁And T₂Described by step S1, the metal shadowing region ［ S established_i, E_i, the most described target correction region is described original image I^O _x,yImage I with preliminary corrections^C _x,yMetal shadowing region.

(2) setting up model image according to target correction region, its process includes:

Target correction region determined by according to, based on original image I^O _x,yAnd preliminary corrections image I^C _{X, y}In belong to the point in described target correction district and carry out repeatedly smoothing processing, rather than the point beyond the district of target correction region does not processes, corrected after original image I^O _x,yIt is model image I^E _x,y。

(3) model image frequency domain orthographic projection acquisition model image data:

By model image I^E _x,yBased on frequency domain orthographic projection, obtain model projection data P^E _x,y.In the method such as step S1 of its projection, (3) carry out orthographic projection based on frequency domain to metal image, thus it is identical to obtain metal shadowing's data method, does not repeats them here.

Step S4: again correct described Raw projection data with described model image data, obtain target projection data；Thus obtain the target image corresponding with described target projection data.

(1) again correct described Raw projection data with described model image data, obtain target projection data:

At described metal shadowing region ［ S_i, E_iIn ］, by model projection data P^E _x,yRevise Raw projection data P^O _{P, n}, obtaining target projection data, its method revised is as follows:

P_R ^O _p,k=P_R ^E _p,k+(P^O _p,Si-P^E _p,Si)*(Ei-k)/(Ei-Si)+(P^O _p,Si-P^E _p,Si)*(k-Ei)/(Ei-Si)

In above process, first, when data for projection subscript value is view field's binary values, i.e. ［ S_i, E_iMinima in ］ and maximum, the revised projection data values of its correspondence is equal to the projection data values before revising, thus can effectively ensure that the seriality being corrected data；Secondly, it is used without the model data (P of artifact^E _x,y) revise the Raw projection data (P with artifact^O _{P, n}), can have and remove the fictitious data producing metal artifacts in described Raw projection data, thus obtain more accurate target projection data.

(2) target image that target projection data are corresponding is obtained:

Carrying out setting up target image by the result of final Modifying model, and described target image is the result through metal artifacts correction, its condition is:

Rebuilding the visual field is the reconstruction visual field that clinical interface selects；

Convolution kernel is the convolution kernel that clinical interface selects；

Building inconocenter is the center that clinical interface is arranged.

Thus obtain the complete image-region that maximum diagnosis object is corresponding, it is ensured that the integrity of target image, in order to Clinical CT operation technician can select these parameters according to the check point scope wished to and image quality requirements.

With reference to shown in Fig. 3, present invention also offers a kind of CT image metal artifact correcting unit realizing above-mentioned CT image metal artifact bearing calibration, comprising:

Original image acquiring unit 10, the CT comprising objects interfered the Raw projection data diagnosing object obtains original image, and extracts original metal image from original image；

Fictitious data acquiring unit 20, connects described original image acquiring unit 10, obtains the metal shadowing data corresponding with original metal image；

First data correction unit 30, connect described fictitious data acquiring unit 20, Raw projection data described in comparison and metal shadowing's data, obtain the diagnosis Object Projection data of the CT diagnosis object after removing objects interfered, based on Raw projection data described in described diagnosis Object Projection Data correction, obtain preliminary corrections data for projection；

Original calibration image acquisition unit 40, connects described first data correction unit 30, obtains the original calibration image that described preliminary corrections data for projection is corresponding；

Model image processing unit 50, connect described original calibration image acquisition unit 40, original image described in comparison and original calibration image, image difference region between the two is carried out figure correction, set up model image, and obtain the model image data that described model image is corresponding；

Second data correction unit 60, connects described model image processing unit 50, again corrects described Raw projection data with described model image data, obtains target projection data；

Target image acquiring unit 70, connects described second data correction unit 60, described target projection data set up corresponding target image.

CT image metal artifact correcting unit of the present invention, after the CT Raw projection data obtaining diagnosis object, determines the metal shadowing's scope as objects interfered using the original image that Raw projection data is corresponding；Obtain the diagnosis Object Projection data after removing objects interfered based on the metal shadowing data in the range of metal shadowing the most successively, and based on described diagnosis Object Projection data Raw projection data be corrected and set up model image；And at the data for projection finally according to model image, described Raw projection data is carried out secondary correction；Afterwards based on the target projection data after correction according to the scanning used by clinic, build slice part and rebuild, obtain the target image not having metal artifacts.Thus, described CT image metal artifact correcting unit is using Raw projection data as calibration object, thus the spatial resolution of the image obtained by correction data after ensureing to process and low contrast ability.And Raw projection data has completely included all of information of objects interfered and has avoided the artifact situation that introducing is new, while it ensures to get rid of artifact, it is ensured that the resolution of image is not suffered a loss.Improve the CT image quality of diagnosis object, obtain the most accurate diagnostic message.

Present invention also offers a kind of CT equipment including above-mentioned CT image metal artifact correcting unit.

Although the present invention is open as above with preferred embodiment; but it is not for limiting the present invention; any those skilled in the art are without departing from the spirit and scope of the present invention; can make possible variation and amendment, therefore protection scope of the present invention should be defined in the range of standard with the claims in the present invention.

Claims (12)

1. a CT image metal artifact bearing calibration, it is characterised in that including:

The Raw projection data being diagnosed object by the CT comprising objects interfered obtains original image, and extracts original metal image from described original image；

Obtain the metal shadowing data corresponding with described original metal image；

Raw projection data described in comparison and metal shadowing's data, obtain the diagnosis Object Projection data of the CT diagnosis object after removing objects interfered, described diagnosis Object Projection data carried out linear interpolation correction, obtains interpolated projections data；Raw projection data described in comparison and described interpolated projections data, obtain preliminary corrections data for projection；

Obtain the original calibration image that described preliminary corrections data for projection is corresponding；

Original image described in comparison and original calibration image, image difference region between the two is carried out figure correction, set up model image, and obtain the model image data that described model image is corresponding, wherein, described figure correction includes: be smoothed the differential image region of described original image with original calibration image；

Again correct described Raw projection data with described model image data, obtain target projection data；

Corresponding target image is set up by described target projection data.

CT image metal artifact bearing calibration the most according to claim 1, it is characterized in that, during being obtained original image by described Raw projection data, described preliminary corrections data for projection obtaining original calibration image and set up target image by described target projection data, at least one process uses filtered back-projection method.

CT image metal artifact bearing calibration the most according to claim 2, it is characterised in that use the CT machine maximum scan visual field as rebuilding the visual field when being filtered back projection for the Raw projection data of the described CT comprising objects interfered diagnosis object.

CT image metal artifact bearing calibration the most according to claim 1, it is characterized in that, obtain the metal shadowing data corresponding with original metal image to include: described original metal image carries out frequency domain orthographic projection based on Fourier's Slice Theorem and processes, it is thus achieved that described metal shadowing data.

CT image metal artifact bearing calibration the most according to claim 4, it is characterized in that, in original metal image carries out orthographic projection processing procedure based on frequency domain, after extending described original metal image, then carry out two-dimensional Fourier transform and one-dimensional inversefouriertransform successively.

CT image metal artifact bearing calibration the most according to claim 1, it is characterised in that in described figure makeover process, carries out repeatedly smoothing processing to the differential image region of described original image Yu original calibration image.

CT image metal artifact bearing calibration the most according to claim 1, it is characterised in that obtain diagnosis Object Projection data and include: after obtaining described metal shadowing data, described metal shadowing data are made orthographic projection, thus extracts metal shadowing region；And in described metal shadowing regional extent, on the basis of Raw projection data each described, eliminate the described metal shadowing data corresponding with described Raw projection data, obtain the diagnosis Object Projection data after removing objects interfered.

CT image metal artifact bearing calibration the most according to claim 7, it is characterised in that obtain target projection data and include: in described metal shadowing region, use Raw projection data described in described model image Data correction.

CT image metal artifact bearing calibration the most according to claim 1, it is characterized in that, described image difference region is obtained by following manner: when original image described in comparison and original calibration image, is some corresponding regions by described original image with described original calibration image division respectively；Comparison corresponding region between the two, and extract the described image difference region of composition, corresponding region that cannot overlap between described original image with original calibration image.

CT image metal artifact bearing calibration the most according to claim 1, it is characterized in that, set up corresponding target image by described target projection data to include: use target projection data described in filtered back projection to set up described target image, wherein, rebuilding the visual field is the reconstruction visual field that clinical interface selects；Convolution kernel is the convolution kernel that clinical interface selects；Building inconocenter is the center that clinical interface is arranged.

11. 1 kinds of CT image metal artifact correcting units, it is characterised in that including:

Original image acquiring unit, the CT comprising objects interfered the Raw projection data diagnosing object obtains original image, and extracts original metal image from original image；

Fictitious data acquiring unit, obtains the metal shadowing data corresponding with original metal image；

First data correction unit, Raw projection data described in comparison and metal shadowing's data, obtain the diagnosis Object Projection data of the CT diagnosis object after removing objects interfered, described diagnosis Object Projection data carried out linear interpolation correction, obtains interpolated projections data；Raw projection data described in comparison and described interpolated projections data, obtain preliminary corrections data for projection；

Original calibration image acquisition unit, obtains the original calibration image that described preliminary corrections data for projection is corresponding；

Model image processing unit, original image described in comparison and original calibration image, image difference region between the two is carried out figure correction, set up model image, and obtain the model image data that described model image is corresponding, wherein, described figure correction includes: be smoothed the differential image region of described original image with original calibration image；

Second data correction unit, again corrects described Raw projection data with described model image data, obtains target projection data；

Target image acquiring unit, is set up corresponding target image by described target projection data.

12. 1 kinds of CT equipment, including CT image metal artifact correcting unit, it is characterised in that described CT image metal artifact correcting unit includes:

Original image acquiring unit, the CT comprising objects interfered the Raw projection data diagnosing object obtains original image, and extracts original metal image from original image；

Fictitious data acquiring unit, obtains the metal shadowing data corresponding with original metal image；

First data correction unit, Raw projection data described in comparison and metal shadowing's data, obtain the diagnosis Object Projection data of the CT diagnosis object after removing objects interfered, described diagnosis Object Projection data carried out linear interpolation correction, obtains interpolated projections data；Raw projection data described in comparison and described interpolated projections data, obtain preliminary corrections data for projection；

Original calibration image acquisition unit, obtains the original calibration image that described preliminary corrections data for projection is corresponding；

Model image processing unit, original image described in comparison and original calibration image, image difference region between the two is carried out figure correction, set up model image, and obtain the model image data that described model image is corresponding, wherein, described figure correction includes: be smoothed the differential image region of described original image with original calibration image；

Second data correction unit, again corrects described Raw projection data with described model image data, obtains target projection data；

Target image acquiring unit, is set up corresponding target image by described target projection data.