CN101095165A - Apparatus and method for artifact correction of X-ray projections - Google Patents
Apparatus and method for artifact correction of X-ray projections Download PDFInfo
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- CN101095165A CN101095165A CNA2005800455858A CN200580045585A CN101095165A CN 101095165 A CN101095165 A CN 101095165A CN A2005800455858 A CNA2005800455858 A CN A2005800455858A CN 200580045585 A CN200580045585 A CN 200580045585A CN 101095165 A CN101095165 A CN 101095165A
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- 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
- G06T11/005—Specific pre-processing for tomographic reconstruction, e.g. calibration, source positioning, rebinning, scatter correction, retrospective gating
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- G—PHYSICS
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- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
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- G06T2211/40—Computed tomography
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- G06T2211/00—Image generation
- G06T2211/40—Computed tomography
- G06T2211/432—Truncation
Abstract
The present invention relates to an apparatus for artifact correction of a data set of X-ray projections (10) of an object (1) for generation of a reconstruction image of said object. In particular for correction of artifacts causing cupping or inverse cupping (called capping) shaped spatially slowly varying inhomogeneities caused by e.g. scatter, a wrong truncation extension factor or a wrong gain factor, an apparatus is proposed comprising: an estimation unit (41) for estimating in an X-ray projection (11) the amount of artifact present in said X-ray projection using at least one estimation parameter, a correction unit (41) for correcting said artifact present in the X-ray projection (11) by use of said estimate, - a reconstruction unit (42) for generating an intermediate reconstruction image by use of said data set of X-ray projections (10) including said corrected X-ray projection, and an evaluation unit (43) for evaluating said correction by determining a quantitative measure of inhomogeneity in said intermediate reconstruction image and for optimizing said correction by iteratively repeating said correction using an adjusted estimation parameter determined by use of said quantitative measure until a predetermined stop criterion has been reached.
Description
Technical field
The present invention relates to a kind of being used for for the reconstructed image that produces object equipment that carries out artifact correction and corresponding method to the X ray projection data set of described object.The invention further relates to a kind of equipment and corresponding method that is used for producing reconstructed image from the X ray projection data set of object.The present invention further relates to a kind of computer program that is used for carrying out on computers described method.
Background technology
In cone-beam computed tomography, scattered radiation constitutes one of subject matter.For the system geometries with big cone angle and big irradiated area therefore, for example based on the C shape arm of volume imagery, scattered radiation produces the huge background that spatially slowly changes especially, and it is added on the desirable detectable signal.Thereby the volume of reconstruction suffers deep-draw and streak artifacts, perhaps more generally, suffer to cause by scattering, cause the uneven pseudomorphism that slowly (partly) changes, stop the report of absolute Hounsfield unit.
The backscattering grid of design machinery stops the detection of scattered radiation, but having demonstrated these grids is invalid for the exemplary systems geometry at volume imagery, because they cause the reduction of signal to noise ratio (S/N ratio).Therefore, proposed to be used for experiential, (for example based on the algorithms of different of the scatter compensation of software, at Maher K.P., Malone J.F., " Computerizedscatter correction in diagnostic radiology ", ContemporaryPhysics, vol.38, no.2,131-148 page or leaf, 1997) or at present at these different algorithms of exploitation.Yet, the shape of the space distribution of scattering in the view that these methods might accurately be estimated to be projected, but be difficult to obtain quantitative scatter estimation accurately.Therefore, local scattered quantum absolute in being projected view is often crossed low or too high estimation, causes the reconstructed results of non-the best.
Have other sources of artifacts in the X ray projection, also can cause spatially slowly change in the reconstructed image inhomogeneous, for example this is inhomogeneous for owing to the fragmentary data group that is used to rebuild of having used the detector littler than objects to cause.Wish to finish the appearance that data set is avoided these pseudomorphisms then.Canonical algorithm (for example at " the Processing ofincomplete measurement data in computed tomography " of R.M.Lewitt, Med.Phys., vol.6, no.5, the 412-417 page or leaf, 1979, described in) requirement determines the project extended factor.
Further, in reconstruction, often require to be identified for the normalized gain factor of data for projection before the use data.Sometimes only understand and be used for the global factor that normalized gain image has a unknown.Use comprises that the gain image of the global factor of mistake carries out normalization to measured projection, with the space that in the image of rebuilding, causes the deep-draw shape once more slowly change inhomogeneous.
Summary of the invention
The object of the present invention is to provide a kind of equipment and corresponding method of artifact correction of the X ray projection data set that is used for object, be used in particular for proofreading and correct the space that causes deep-draw (cupping) and anti-deep-draw (being so-called gland (capping)) shape and slowly change uneven pseudomorphism, this inhomogeneous gain factor that blocks spreading factor or mistake by for example scattering, mistake is caused.Further purpose be to provide a kind of be used for producing from the X ray projection data set of object comprise less or do not have the equipment and the corresponding method of the reconstructed image of pseudomorphism.
According to the present invention, reach purpose of the present invention by the equipment described in claim 1, this equipment comprises:
Estimation unit is used for using at least one estimated parameter to estimate the pseudomorphism quantity that exists in described X ray projection in the X ray projection,
Correcting unit is used for by using described estimation to proofread and correct the described pseudomorphism that exists in the X ray projection,
Reconstruction unit is used for comprising that by use the described X ray projection data set of described X ray projection of having proofreaied and correct generates intermediate reconstructed images, and
Evaluation unit, be used for by determining to estimate described correction in the uneven quantitative measurment of described intermediate reconstructed images, and be used for optimizing described correction by using the adjusted estimated parameter of determining by described quantitative measurment to repeat described correction iteratively up to reaching predetermined stopping criterion.
According to the present invention, the reconstructing apparatus that claim limits comprises:
In claim 15 and 16, define corresponding method.Computer program on the be stored in record carrier that the present invention also relates to limit as claim 17.The preferred embodiments of the present invention limit in the dependent claims.
The present invention is based on iteratively the thought of the performance of optimizing (preferably based on software) the arbitrarily method that is used for that artifact estimation, particularly scattering estimate.By defining the uneven quantitative measurment that causes by pseudomorphism, the particularly quantitative measurment of (under the situation of the pseudomorphism that scattering causes) residue deep-draw in the volume of rebuilding, and by using this to measure to repeat to estimate the efficient of artifact correction, the corresponding adjustment of parameter realizes this thought in all handling succeeded by artifact compensation each time.
In order to realize so measuring, the performance rate that it has quantized the compensation method of employing can have different selections.In one embodiment of the invention, volumetric image for human body, the major part of voxel (voxel) shows and the similar pad value of water, therefore, near the pad value of water middle contrast level is the easiest sees that the inhomogeneous of for example deep-draw, this deep-draw mean inhomogeneous this inhomogeneous pseudomorphism of disturbance the most that caused at the center of projected image of slow variation.Therefore, preferred starting point is for selecting to comprise the contrast window interested of deep-draw.Then, carry out the threshold process up and down of the pad value in the reconstruct volume.For the uneven quantification of for example deep-draw, can adopt the statistical property of the voxel that belongs to selected window, for example standard deviation.Replacedly, polynomial expression or another function can at first be fitted to the data in the selected window, maybe can use strong low-pass filtering, succeeded by another step, derive standard deviation or suitable curvature measurement from the profile that obtains.
After having defined the mass measurement that is used for artifact correction, can use the performance that simplex algorithm is optimized any artifact compensation method.Any one inner parameter of the compensation method of being adopted can be used to optimize, perhaps can use the additional factor convert comprehensively this method the result (for example, the space profiles of estimated pseudomorphism in each projection view), it is by so adjustment so that mass measurement are maximized.So then factor will illustrate the error of artifact estimation, and this error can be derived from theory on (physics of bearing calibration is simplified) or the algorithm and (carry out discretize).
The optimizing process of suggestion can not required any user interactions by operation fully automatically.Iterative approximation can be carried out to keep amount of calculation suitably low with coarse resolution.Be not only applicable to the C shape arm based on volume imagery on this methodological principle, also be applicable to multi-thread spiral CT, still, scattering quantity therein is low more and the backscattering grid is just effective more.
In a preferred embodiment, this equipment is particularly suitable for scatter correction, wherein:
Described estimation unit is suitable for using in the X ray projection at least one estimated parameter to estimate the scattering quantity that exists in described X ray projection,
Described correcting unit is suitable for proofreading and correct described X ray projection by deduct estimated scattering from the data for projection of described X ray projection, and
Described evaluation unit is suitable for estimating described correction by the quantitative measurment of determining the residue deep-draw in described intermediate reconstructed images, and be suitable for optimizing described correction by using the adjusted estimated parameter of determining by described quantitative measurment that is used for the scattering estimation to repeat described correction iteratively up to reaching predetermined stopping criterion.
Although noticing mainly to be proposed to be used in improves scatter correction, suggestion is not limited to this application.Replacedly, it can change into and be used for the performance that the optimizing computer beam is strengthened compensation or truncation correction, or optimizes gain normalization, because beam is strengthened, blocked with wrong gain factor and also cause pseudomorphism, for example deep-draw.Therefore, under the situation of a plurality of corrections based on software, should carry out the correction of iteration optimization at last.
Like this, equipment is suitable for proofreading and correct the projection of blocking in a specific embodiment, wherein:
Described estimation unit is suitable for using in the X ray projection at least one estimated parameter to estimate the degree of blocking that exists in described X ray projection,
Described correcting unit is suitable for by adopting spreading factor or another to use the described estimation approach of blocking to expand described X ray projection and proofread and correct described X ray projection, and
Described evaluation unit is suitable for estimating described correction by the quantitative measurment of determining in described intermediate reconstructed images deep-draw or gland, and be suitable for optimizing described correction by using the adjusted estimated parameter of determining by described quantitative measurment that is used to block estimation to repeat described correction iteratively up to reaching predetermined stopping criterion.
Further, equipment is suitable for the gain normalization of corrected projection data in another specific embodiment, wherein:
Described estimation unit is suitable for using in the X ray projection at least one estimated parameter to estimate suitable gain factor,
Described correcting unit is suitable for that described X ray projection is proofreaied and correct in the described X ray projection of normalization by adopting described gain factor,
Described evaluation unit is suitable for by determining that the deep-draw in described intermediate reconstructed images or the quantitative measurment of gland estimate described correction, and be suitable for optimizing described correction by using the adjusted gain factor of determining by described quantitative measurment that is used for gain normalization to repeat described correction iteratively up to reaching predetermined stopping criterion.
Use similar quality factor by quantizing for example to remain the inhomogeneous of deep-draw or pass through, the iteration optimization of the computerized artifact compensation of suggestion has guaranteed as the defined optimum picture quality that is used for reconstruct volume of mass measurement.The solution that proposes will greatly be improved remove the inhomogeneous of for example deep-draw that caused by pseudomorphism, observability when therefore allowing to improve the low contrast object in the volume of rebuilding.
Description of drawings
Embodiment more detailed description the present invention shown in inciting somebody to action in conjunction with the accompanying drawings now, wherein:
Fig. 1 shows the influence of scattering,
Fig. 2 shows the block scheme of the reconstructing apparatus according to the present invention,
Fig. 3 is schematically illustrated according to artifact correction equipment of the present invention,
Fig. 4 to 6 shows the embodiment that is used to estimate the pseudomorphism effect according to of the present invention, and
Fig. 7 shows the result who uses the method according to this invention and obtain.
Embodiment
Before more detailed description the present invention in conjunction with the embodiments, Fig. 1 shows the influence of scattering and by the generation of the radiation-induced deep-draw pseudomorphism of scattering.The photon that the theoretical assumption of rebuilding when computed tomography (CT) is all or be absorbed in detected object perhaps directly arrive detector, and in fact the decay of maximum is not to be caused by absorption, but is caused by scattering.Therefore, as shown in Figure 1a, the photon of a considerable amount of scatterings arrives detector in the non-rectilinear mode.
Shown in Fig. 1 b, even relatively usually by the background signal that scattered radiation causes, promptly change especially lentamente, but its quantity is huge especially.Do not use the backscattering grid, the part that is caused by scattered radiation in the total signal strength can reach 50% or more.Can see from the curve shown in Fig. 1 b, at the middle part of deamplification, be maximum for the resultant signal relative error.Therefore, shown in Fig. 1 c, at the middle part of the object of rebuilding, relative error also is maximum, can see typical deep-draw effect in the bottom.For example, for head, can find to be lower than correct gray-scale value to reach-deviation of 150HU.
Like this, causing the caused problem of pseudomorphism by scattering is that scattering has stoped absolute quantification (HU), has influenced the observability of low contrast structure and next step Flame Image Process has been produced problem.
Fig. 2 schematically shows the total layout according to reconstructing apparatus of the present invention.By Usage data collection unit 2, for example CT or X-ray equipment, acquisition target 1, for example the X ray projected data group of patient's head.The data set of gathering is stored in the storer usually, and for example the storage unit of another type of the hard disk of the clinical webserver or workstation is used for further handling the protected data of gathering.Before producing the super-resolution reconstruction image by reconstruction unit 5, can predict according to the present invention, carry out artifact correction by using artifact correction equipment 4, it will be described in detail below.The X ray projection of Jiao Zhenging is used to rebuild high-resolution reconstructed image then, is used for showing at display unit 6 subsequently.
Fig. 3 schematically shows the layout and the function of the artifact correction equipment that proposes according to the present invention.In the figure, more details in the artifact correction unit 4 shown in Fig. 2 have been described.
The thought of iterative scatter correction is at first to the common ambiguous scatter correction algorithm of the X ray projection application that obtains.Like this, the input of scattering estimation and correcting unit 41 can be the data set of original X ray projection 10, perhaps in order to save the required time of iteration that is used for subsequently, can be data set 11 by the minimizing of original projection 10 being carried out the less X ray projection that space and/or angle double sampling obtain.
Estimation and correction by unit 41 execution are normally incomplete, perhaps the incorrect correction parameter that is provided with when the initialization operation of iteration.For example, in a preferred embodiment, be the base application scatter correction with scattering fraction (SF) with respect to the measured minimum detection value of each projection.Described embodiment can followingly implement:
The minimum measured value (after strong low-pass filtering, selectively carrying out) of each projection of-search;
-supposition fixed percentage (for example initial 50%) is the minimum value of the fixedly scattering background of each projecting direction;
-from the data for projection of projection, deduct the described fixedly scattering background of each projecting direction; And
-above-mentioned the fixed percentage of mentioning is called as scattering fraction (SF), is the parameter of optimised scatter correction embodiment.
The projection of Jiao Zhenging is used to rebuild intermediate reconstructed images then, for example uses the Feldkamp-David-Kress algorithm for the filtered back projection of conical beam in reconstruction unit 42.For very fast execution, described reconstruction can be very coarse, and low-down resolution is arranged.
In evaluation unit 43,, will estimate intermediate reconstructed images with respect to the scattering deep-draw pseudomorphism that will remove.Described evaluation general is described in detail with reference to the figure of back below.Result according to described deep-draw is estimated will adjust one or more parameters (the scattering fraction SF in the example recited above) of scatter correction and begin next iteration.
In iteration, arrive after the stopping criterion, for example, if if moved the iteration of predetermined quantity or further optimization of not realization in the end in service, in reconstruction unit 5, will use the final scatter correction of adjusting parameter (optimized in this embodiment scattering fraction) to be applied in complete high resolving power projection data set at last, and carry out final reconstruction of high resolving power consuming time and finally obtain the full resolution reconstructed image to be presented on the monitor 6.
Now introduce the embodiment of preferred deep-draw evaluation method in detail.The deep-draw evaluation method of preferred suggestion comprises two key steps:
A) select suitable voxel, can be used in measurement/quantification deep-draw, and
B) calculating deep-draw according to described selection measures.
Most of human body is made up of the tissue of water or similar water, so the gray-value variation of the tissue of the similar water that is caused by scattering by use can be estimated deep-draw best.This will realize based on threshold value below.Determine threshold value itself based on histogram.For this purpose, shown in Fig. 4 a, prepared histogram at first about all voxels of reconstruct volume.For this histogram, be enough to select the scope of its value from 50% to 200% of the expectation pad value of for example water.In Fig. 4 b, showing will be by 40 in 64 sections of the coarse volume of the reconstruction that be estimated (showing with HU window relatively tightly).
For the histogram value of determining, fitted Gaussian distribution shown in Fig. 4 a.According to the least square method method of using nonlinear least square method optimized Algorithm (for example Levenberg-Marquardt algorithm), described Gaussian distribution comprises following even distribution.Like this, obtain the mean value and the standard deviation of Gaussian distribution, the scale factor that is used for adjusting range and is used to adjust equally distributed amplitude alternatively.
Based on the result of match, select two pairs of threshold values now:
A) among a small circle: mean value ± 1 standard deviation;
B) on a large scale: mean value ± 2 standard deviation.
Based on these scopes, select the voxel that is used to estimate according to following strategy:
A) directly use among a small circle all pixels;
B) as long as the voxel (preferably in the neighborhood of 6 neighboring voxels) of the direct neighbor of these voxels not have not in described bigger scope, just use large-scale all voxels.
Fig. 5 a shows intermediate result.This figure illustrates the coarse volume of reconstruction once more, wherein for there not being selecteed all voxels, the most black " deceiving " value is carried out assignment.Because the influence of partial volume, still there is the outlier of some at water and bone edge.
For the elimination of outlier, will be to selected voxel polynomial fitting.Preferably, match quadratic polynomial in three coordinates, yet do not have mixed term (xy, xz, yz).Like this, x
2, y
2, z
2, x, y, the coefficient of z and a constant must be determined.Use common linear least square to determine.
Such fitting of a polynomial is illustrated as the example of the curve map shown in Fig. 6 a.In Fig. 6 b, the selecteed voxel of all of about 50.000 voxels (" effectively water ") is replaced by the result of this match.Image is very level and smooth thus; Black zone is not have selecteed voxel.Found this match for same to as if believable and repeatably.
Subsequently, determine the deep-draw measurement.In a preferred embodiment, at the last described fitting of a polynomial result's who estimates of all selected voxels (aforesaid) standard deviation, be used as deep-draw and measure.In another embodiment, can use other deep-draw to measure, for example:
The described fitting of a polynomial result's who estimates on all selected voxels maximal value deducts minimum value separately;
The MSD maximum standard deviation separately of all sections; Or
Maximum difference separately between the minimum and maximum value of all sections.
All available measurements are believable and repeatably thus.
Therefore main thought of the present invention is to use any scatter correction schemes, and it can be simple and imperfect, and adjusts described scatter correction schemes repeatedly and obtain uniform reconstruct volume.Except above-mentioned scatter correction schemes, also can use other scatter correction schemes based on scattering fraction.One class scatter correction schemes is so-called " self-supporting method ".These " self-supporting methods " are to get rid of the method that ground uses the parameter of adjusting by iterative optimization method.These parameters are for example:
Global constant's (for example, from all projections, deducting identical scattering background);
Overall situation scattering fraction (as above describing in detail); Or
Polynomial one or more parameters of scattering in the projection are described usually.
Another kind of scatter correction schemes is so-called " method of complementation of single ".Use a model or coarse voxel is rebuild the suitable available calculating single scattering of effort of cost and promptly only is scattered once quantum.Yet, still lacked repeatedly scattering, its quantity reach total scattering 50% or more.The iterative scatter correction that use is advised according to the present invention can parameters optimization, and it allows to estimate repeatedly scattering from calculated single scattering.
Fig. 7 a and Fig. 7 b illustrate the result of the scatter correction of the present invention's realization.As the reconstructed image in Fig. 7 a as can be seen, the influence of scattering is so strong, so that the major part of head no longer can be identified, because gray-scale value is no longer in visual gray-scale value scope and have a lower gray-scale value.After having used, no longer include such situation according to scatter correction method of the present invention.That realizes thus is reconstituted in shown in Fig. 7 b.In reconstructed image deep-draw hardly as seen, image is uniformly and can sees easily in the gray-scale value scope of hope.Like this, the mean difference with respect to ideal image is less than 20HU in tissue regions.
When the present invention was mainly used in scatter correction, total thought of the present invention can be applied to other.For example, the present invention can be applied to adjust the project extended factor or adjust gain factor.The method that is used to adjust the project extended factor uses as mentioned above same steps as referring to Fig. 3 (to be replaced by " by using spreading factor especially according to the project extended of people such as " " Lewitt (referring to top) " now at this " scattering is estimated and proofreaied and correct " basically.
The adjustment of the global gain factor of projection value equals the adjustment (after adopting logarithm) of the overall summand of line integral value.Like this, in method as shown in Figure 3, be used for " using global constant " that step " scattering is estimated and proofreaied and correct " that gain factor adjusts will be adjusted basically and replace.
Claims (17)
1, be used for comprising for the reconstructed image that produces object carries out the equipment of artifact correction to the data set of the X ray projection (10) of described object:
Estimation unit (41) is used for using at least one estimated parameter to estimate the pseudomorphism quantity that exists in described X ray projection in X ray projection (11),
Correcting unit (41) is used for by using described estimation to proofread and correct the described pseudomorphism that exists in X ray projection (11),
Reconstruction unit (42) is used for comprising that by use the data set of the described X ray projection (10) of described X ray projection of having proofreaied and correct produces intermediate reconstructed images, and
Evaluation unit (43), be used for by determining to estimate described correction in the uneven quantitative measurment of described intermediate reconstructed images, and be used for optimizing described correction by using the adjusted estimated parameter of determining by described quantitative measurment to repeat described correction iteratively up to reaching predetermined stopping criterion.
2, equipment as claimed in claim 1,
Wherein said estimation unit (41) is suitable for using independent estimated parameter to estimate the pseudomorphism quantity that exists individually in a plurality of X ray projections, and
Wherein said correcting unit (41) is suitable for proofreading and correct individually described X ray projection (11).
3, equipment as claimed in claim 1, wherein said evaluation unit (43) are suitable for adjusting the described estimated parameter based on described quantitative measurment.
4, equipment as claimed in claim 1, wherein said evaluation unit (43) is suitable for having in the preset range by selecting in described intermediate reconstructed images, especially near the scope the image value of water, the voxel of image value, determine the uneven quantitative measurment in described intermediate reconstructed images, the image value of described selected voxel is used to determine described quantitative measurment.
5, equipment as claimed in claim 4, wherein said evaluation unit (43) is further adapted for by using about the histogram of all voxels with by the last lower threshold value that adopts image value and selects described voxel, in described intermediate reconstructed images, select voxel, described threshold value obtains from described histogrammic statistical property, especially obtains from the statistical property that is fitted to described histogrammic histogram curve.
6, equipment as claimed in claim 5, wherein said evaluation unit (43) is further adapted for by the voxel curve fitting being arrived the image value of selected voxel and by adopting the statistical property of described voxel curve, determining described quantitative measurment from the image value of selected voxel.
7, equipment as claimed in claim 1, wherein said stopping criterion are the predetermined value of the iteration of predetermined quantity, described quantitative measurment or the minimum value of described quantitative measurment, perhaps are used for the predetermined value in the minimal difference of quantitative measurment described in the iteration subsequently.
8, equipment as claimed in claim 1, wherein said reconstruction unit (42) is suitable for producing the intermediate reconstructed images of low resolution.
9, equipment as claimed in claim 1, wherein said X ray projection (11) are the X ray projections of low resolution, especially by to the original high resolution X ray projection carry out double sampling and obtain.
10, equipment as claimed in claim 1, described equipment is suitable for scatter correction, wherein:
Described estimation unit (41) is suitable for using in X ray projection (11) at least one estimated parameter to estimate the scattering quantity that exists in described X ray projection,
Described correcting unit (41) is suitable for proofreading and correct described X ray projection (11) by deduct estimated scattering from the data for projection of described X ray projection, and
Described evaluation unit (43) is suitable for estimating described correction by the quantitative measurment of determining residue deep-draw in described intermediate reconstructed images, and be suitable for optimizing described correction by using the adjusted estimated parameter of determining by described quantitative measurment that is used for the scattering estimation to repeat described correction iteratively up to reaching predetermined stopping criterion.
11, equipment as claimed in claim 10, wherein said estimation unit (41) are suitable for basis and estimate scattering quantity at the scattering fraction of the minimum detector value of the X-ray detector that obtains described X ray projection.
12, equipment as claimed in claim 1, described equipment is suitable for proofreading and correct the projection of blocking, wherein:
Described estimation unit (41) is suitable for using in X ray projection (11) at least one estimated parameter to estimate the degree of blocking that exists in described X ray projection,
Described correcting unit (41) is suitable for by adopting spreading factor or another to use the described estimation approach of blocking to expand described X ray projection and proofread and correct described X ray projection, and
Described evaluation unit (43) is suitable for estimating described correction by the quantitative measurment of determining in described intermediate reconstructed images deep-draw or gland, and be suitable for optimizing described correction by using the adjusted estimated parameter of determining by described quantitative measurment that is used to block estimation to repeat described correction iteratively up to reaching predetermined stopping criterion.
13, equipment as claimed in claim 1, described equipment is suitable for the gain normalization of corrected projection data, wherein:
Described estimation unit (41) is suitable for using in the X ray projection at least one estimated parameter to estimate suitable gain factor,
Described correcting unit (41) is suitable for that described X ray projection is proofreaied and correct in the described X ray projection of normalization by adopting described gain factor,
Described evaluation unit (41) is suitable for by determining that the deep-draw in described intermediate reconstructed images or the quantitative measurment of gland estimate described correction, and be suitable for optimizing described correction by using the adjusted gain factor of determining by described quantitative measurment that is used for gain normalization to repeat described correction iteratively up to reaching predetermined stopping criterion.
14, be used for producing the reconstructing apparatus of reconstructed image, comprise from the X ray projected data group of object:
Image acquisition units (2) is used for the described data set of the X ray projection (10) of acquisition target (1),
Artifact correction equipment (4) is used for according to claim 1 the described data set of X ray projection is carried out artifact correction, and
Super-resolution reconstruction unit (5) is used for producing from the X ray projection of described correction the super-resolution reconstruction image of described object.
15, be used for may further comprise the steps for the reconstructed image that produces object carries out the method for artifact correction to the X ray projection data set of described object (1):
In X ray projection (11), use at least one estimated parameter to estimate the pseudomorphism quantity that in described X ray projection, exists,
By using described estimation to proofread and correct the described pseudomorphism that in the X ray projection, exists,
The described X ray projection data set that comprises the X ray projection of described correction by use produces intermediate reconstructed images,
By determining that described correction is estimated in uneven quantitative measurment in described intermediate reconstructed images, and
By using the adjusted estimated parameter of determining by described quantitative measurment to repeat described correction iteratively, optimize described correction up to reaching predetermined stopping criterion.
16, be used for producing the method for reconstructing of reconstructed image, may further comprise the steps from the data set of the X ray projection (10) of object (1):
The described data set of the X ray projection (10) of acquisition target,
Method according to claim 15 is carried out artifact correction to the described data set of X ray projection, and
Produce the super-resolution reconstruction image of described object from the X ray projection of described correction.
17, computer program comprises being used to make the computing machine enforcement of rights to require the program code devices of the step of 15 described methods.
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| US4550371A (en) * | 1982-09-27 | 1985-10-29 | General Electric Company | Method and apparatus for compensating CT images for truncated projections |
| US4570224A (en) * | 1982-11-29 | 1986-02-11 | Elscint, Inc. | Combining rebinned and unrebinned parallel ray data with unequal lateral spacing to create tomograph images |
| US6507633B1 (en) * | 2001-02-15 | 2003-01-14 | The Regents Of The University Of Michigan | Method for statistically reconstructing a polyenergetic X-ray computed tomography image and image reconstructor apparatus utilizing the method |
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- 2005-12-21 EP EP05826166A patent/EP1834303A1/en not_active Withdrawn
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Also Published As
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|---|---|
| JP2008525142A (en) | 2008-07-17 |
| WO2006070316A1 (en) | 2006-07-06 |
| EP1834303A1 (en) | 2007-09-19 |
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