CN102670230A - Method for reducing motion artifact in dect - Google Patents

Method for reducing motion artifact in dect Download PDF

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CN102670230A
CN102670230A CN2012100593173A CN201210059317A CN102670230A CN 102670230 A CN102670230 A CN 102670230A CN 2012100593173 A CN2012100593173 A CN 2012100593173A CN 201210059317 A CN201210059317 A CN 201210059317A CN 102670230 A CN102670230 A CN 102670230A
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image
projection
layer
ground floor
layer position
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CN102670230B (en
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H.布鲁德
B.克劳斯
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Siemens AG
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Siemens AG
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/02—Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03—Computerised tomographs
    • A61B6/032—Transmission computed tomography [CT]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/40—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for generating radiation specially adapted for radiation diagnosis
    • A61B6/4007—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for generating radiation specially adapted for radiation diagnosis characterised by using a plurality of source units
    • A61B6/4014—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for generating radiation specially adapted for radiation diagnosis characterised by using a plurality of source units arranged in multiple source-detector units
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/48—Diagnostic techniques
    • A61B6/482—Diagnostic techniques involving multiple energy imaging
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/50—Clinical applications
    • A61B6/503—Clinical applications involving diagnosis of heart
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
    • A61B6/5258—Devices using data or image processing specially adapted for radiation diagnosis involving detection or reduction of artifacts or noise
    • A61B6/5264—Devices using data or image processing specially adapted for radiation diagnosis involving detection or reduction of artifacts or noise due to motion
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
    • A61B6/5288—Devices using data or image processing specially adapted for radiation diagnosis involving retrospective matching to a physiological signal

Abstract

The present invention relates to a method for reducing motion artifact in DECT (Dual-Energy Computed Tomography). The method comprises the steps of: performing image recording by utilizing a pitch, wherein, the pitch allows that multiple layer images are re-established at each layer position; preferably, re-establishing multiple first layer images at the each layer position from comprehensive measuring data of two X-ray image shooting systems (1-4); calculating motion vectors from the first layer images at the each layer position, wherein, the motion vector represents a motion measurement from a layer image to a layer image; interpolating the motion vectors into a time grid of a projection; selecting the projection recorded in a weak motion stage; and performing dual-energy image re-establishing only based on the selected projection. In this way, a dual-energy image photo having reduced motion artifact can be obtained.

Description

Be used for reducing the method for motion artifacts at dual energy computed tomography
Technical field
The present invention relates to a kind of method of utilizing computer tomograph in dual energy computed tomography, to reduce motion artifacts, this computer tomograph has two radioscopic image camera systems that separate, and is also referred to as the double source computer tomograph.
Background technology
Through respectively by X-ray tube and two radioscopic image camera systems that separate forming with the X-ray detector of X-ray tube positioned opposite; Can utilize two different X ray energy to write down radioscopic image simultaneously and take, method is with two X-ray tubes of different voltages with different operation.Dual intensity is taken for example can distinguish different histological types in radioscopic image.For example, known dual intensity (DE) the pulmonary perfusion CT that is used to check pulmonary, it can the detecting breathing defective or loses through the perfusion that thrombosis (Thromben) causes.But the image artifacts that causes through heart movement under the situation of this application, can occur, these image artifacts critically influence perfusion analysis.
Summary of the invention
The technical problem that the present invention will solve is, a kind of method is provided, and can in dual energy computed tomography (DECT), reduce motion artifacts through this method.
Above-mentioned technical problem is through solving according to method of the present invention.The favourable embodiment of this method is the content of dependent claims or can from following description and embodiment, draws.
In the method for being advised, implement image recording through two radioscopic image camera systems that separate with pitch, utilize this pitch for each layer position z 0Obtain n projection of quantity, these projections allow to rebuild a plurality of tomographic images in each layer position.This in known manner pitch be understood that the ratio of bed thickness of bed feeding and the imaging layer of the computer tomograph that rotation causes about each frame.Preferably, in the method for being advised, select 0.5 or less than 0.5 pitch.Implement through the different x-ray voltage of two X-ray tubes according to common mode image recording itself, so that utilize the interesting areas of different X ray energy acquisition inspection objects, for example pulmonary.
For each layer position; Thus at first according on the time of radioscopic image camera system each other successively the measurement data of the rotating projection of part rebuild a plurality of ground floor images, preferably make up the measurement data of two radioscopic image camera systems respectively for this tomographic image.90 ° angle is arranged on the frame of computer tomograph because two radioscopic image camera systems stagger in the double source computer tomograph each other; Thus in this case for half revolution is rebuild four/enough once rotating because in order to rebuild the projection or the measurement data of two radioscopic image camera systems of ground floor image synthesis.Different X ray energy is inoperative at this, because this ground floor image only is considered for confirming possible motion in the method for being advised.For each radioscopic image camera system, can rebuild the ground floor image dividually.In this case thus for rebuilding half revolution that needs frame respectively.
Go up the tolerance that changes according to these ground floor images for the time of each layer position calculation tomographic image to the picture material of tomographic image thus.This point preferably through will be on each time successively tomographic image each other, just according to the gray value differences phase Calais realization between the tomographic image rebuild of the rotating measurement data of part successively each other on the time by pixel.The locational motion tolerance of layer that changes at image recording at the value representation of this acquisition according to this layer, and below be called motion vector.Through obtaining about returning back to the information of moving in the interesting areas of the rotating corresponding layer of locational inspection object of part in part to analyzing at the locational ground floor image of each layer.Then, with the trickleer time grid (Zeitraster) that is inserted into each projection in the motion vector.This point can be realized through linear interpolation under the simplest situation.About each projection, this draws the course that suction movement (Pumpbewegung) corresponding to heart has maximum and minima with describing under the situation of heart movement to the influence of interesting areas.It is obvious that thus, in which projection of record of strong movements stage and in faint motion or which projection of quiescent phase record.
For final dual intensity image reconstruction; Wherein utilize the measurement data of two radioscopic image camera systems record to rebuild tomographic image for each radioscopic image camera system dividually, so the projection of only considering to write down in such stage or the measurement data of these projections at faint motion or quiescent phase.The upper threshold value of given motion vector in advance for this reason.This threshold value can be absolute value or for example also can be used as definite peaked part or provide as several times of minima.
Image reconstruction for the dual intensity tomographic image only uses following projection thus, promptly wherein during measuring, does not move or small motion only, thereby in image, reduces motion artifacts significantly.
Said method can be used to reduce the motion artifacts that causes through heart movement highly beneficially, particularly the motion artifacts when dual intensity pulmonary perfusion CT.
Description of drawings
Combine accompanying drawing that the method for being advised is described further according to embodiment below.In the accompanying drawing:
Fig. 1 shows the schematic representation of apparatus of radioscopic image camera system in the double source computer tomograph,
Fig. 2 shows the flow chart of the method that execution advises, and
Fig. 3 shows the sketch map according to the time relationship of the example of the method for being advised.
The specific embodiment
Fig. 1 schematically shows the device of two radioscopic image camera systems in the double source computer tomograph strongly.Two radioscopic image camera systems forming by X-ray tube 1,3 with the X-ray detector 2,4 of X-ray tube positioned opposite respectively are arranged in frame 5 inside of computer tomograph under angle staggers 90 ° condition.Can utilize two radioscopic image systems to write down respectively to stagger 90 ° projection in this way simultaneously.Thus, measurement data analyzes and is redeveloped into the tomographic image of expectation in data processing unit 6.The patient is being positioned at during the image recording on unshowned patient's bed in known manner, and this patient's bed moves through frame 5 on the z direction.The z direction is corresponding to perpendicular to the planar direction of page or leaf in the accompanying drawings.
In the method for being advised, gather the dual intensity measurement data with little pitch, select about 0.5 pitch in this example for this reason.Measured value projection p thus 1(z 0) ..., p n(z 0) facilitate z in the position 0Image layers or the tomographic image of reconstruction.Because little feed value, shown layer can a plurality of with the time on imaging in the double source at the interval of pi/2 is rebuild each other successively.At t k=(k-1) * pi/2+t sDouble source constantly is reconstituted in half revolution reconstruction that this expression is formed by the complementary measurement data of pi/2 angle of two radioscopic image recording systems 1,2 or 3,4.t sBe the first measured value projection (p 1) the moment, the z in layer position is facilitated in this first measured value projection 0Image reconstruction.Angle through frame having been rotated 90 ° can be gathered the projection about 180 ° angular range through the measurement data that merges two radioscopic image camera systems thus, and carries out half revolution thus and rebuild.Obtain in the picture position z for each k 0The picture signal I at place k(z 0).Little pitch based on 0.5 here can embodiment such as disjoint half revolution of k=8 rebuild so that obtain in layer position z 08 tomographic images at place.From this image stack, can confirm motion vector (Motionvektor, motion vector MM k).This for example can realize through the gray value differences phase Calais by pixel that will go up adjacent picture signal or tomographic image the time:
MM k ( z 0 ) = Σ x ( I k ( x ) - I k - 1 ( x ) ) 2
At this can certainly be other gap size.Thus with the trickleer time grid that is inserted into projection scanning in the motion vector.Usually because the smoothed curve that the heart movement expectation has motion maximum and minima.Rebuild for dual intensity, just separately rebuild the measurement data of detector 2 and detector 4, only consider the measured value projection of gathering for corresponding layer position at the quiescent phase of motion vector.The dual intensity CT image that is only comprised the pseudo-shadow of minimum movement thus.Usually a small amount of ray of each image layers is that image is made contributions.Consider this point under the standardized situation in backprojector.
Fig. 2 is schematically illustrated in the above-mentioned flow process under the situation of the method for being advised for this reason.Exemplary once more among Fig. 3 temporal relation is shown.At this, electrocardiogram is represented on the top of Fig. 3, and this electrocardiogram shows heart movement.Exemplary table is shown time range 7 in the bottom, and record is used for the z in layer position in this time range 0The measurement data that the place rebuilds.Because little feed speed can be rebuild a plurality of tomographic images from the measurement data of record in this time range 7, a width of cloth tomographic image is rebuild in per quart revolution (pi/2), as this representes through arrow in the accompanying drawings.Be reconstituted in the measurement data of two radioscopic image camera systems of this combination for this.Then from these images calculation of motion vectors and in be inserted into the time grid of each projection.Bottom at accompanying drawing shows the result, wherein schematically shows the temporal course of the motion vector that obtains in this way.According to expection, this motion vector have respectively in heart strong movements stage scope maximum and in the minima of quiescent phase.Thus, motion vector shows the zone of the motion of varying strength.For motion compensation ground rebuilds dual intensity CT image, only use the projection that comes from the stage 8 of not moving as far as possible thus.

Claims (8)

1. method of utilizing computer tomograph in dual energy computed tomography, to reduce motion artifacts, said computer tomograph has two radioscopic image camera systems (1-4) that separate, wherein
-image recording utilizes pitch to carry out, and utilizes this pitch to obtain a plurality of projections for each layer position, and a plurality of tomographic images inequality are rebuild in these projections permissions in each layer position,
-for rebuilding a plurality of ground floor images on the time of each layer position radioscopic image camera system (1-4) each other successively in the measurement data of the rotating projection of part,
-calculate the tolerance that time of picture material of tomographic image to the tomographic image of ground floor image go up to change respectively for each layer position, and insert the temporal variation of confirming to be projected to projection through interior,
-select following projection, the temporal variation that promptly wherein is projected to projection is less than given in advance threshold value, and
-rebuild second layer image for each radioscopic image camera system (1-4), wherein only use the measurement data of radioscopic image camera system (1-4) and selected projection separately.
2. method according to claim 1 is characterized in that, carries out the reconstruction of said ground floor image dividually for each radioscopic image camera system (1-4).
3. method according to claim 1 is characterized in that, makes up the measurement data of two radioscopic image camera systems (1-4) respectively for the reconstruction of said ground floor image.
4. method according to claim 3 is characterized in that, from the time of radioscopic image camera system (1-4), rebuilds the ground floor image the measurement data of four/single-revolution successively each other respectively for each layer position.
5. according to each described method in the claim 1 to 4, it is characterized in that the pitch through≤0.5 is carried out image recording.
6. according to each described method in the claim 1 to 5, it is characterized in that, through the tolerance that will obtain in the gray value differences phase Calais between the respective pixel of each ground floor image to change on time of picture material of tomographic image to tomographic image.
7. according to each described method in the claim 1 to 6, be used to reduce cardiac motion artefacts.
8. according to each described method in the claim 1 to 6, be used to reduce the cardiac motion artefacts when the image recording of dual intensity pulmonary perfusion image.
CN201210059317.3A 2011-03-15 2012-03-08 Method for reducing motion artifact in dect Expired - Fee Related CN102670230B (en)

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CN110298794A (en) * 2019-05-20 2019-10-01 上海联影智能医疗科技有限公司 Medical image system, method, computer equipment and readable storage medium storing program for executing
CN112603338A (en) * 2020-12-02 2021-04-06 赛诺威盛科技（北京）有限公司 Method and device for selecting and retrospective reconstruction data of heart spiral retrospective reconstruction

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CN110298794A (en) * 2019-05-20 2019-10-01 上海联影智能医疗科技有限公司 Medical image system, method, computer equipment and readable storage medium storing program for executing
CN112603338A (en) * 2020-12-02 2021-04-06 赛诺威盛科技（北京）有限公司 Method and device for selecting and retrospective reconstruction data of heart spiral retrospective reconstruction

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