CN102670230B - Method for reducing motion artifact in dect - Google Patents

Method for reducing motion artifact in dect Download PDF

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Publication number
CN102670230B
CN102670230B CN201210059317.3A CN201210059317A CN102670230B CN 102670230 B CN102670230 B CN 102670230B CN 201210059317 A CN201210059317 A CN 201210059317A CN 102670230 B CN102670230 B CN 102670230B
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image
layer
projection
ground floor
radioscopic
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CN102670230A (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

For reduce 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 to reduce motion artifacts in dual energy computed tomography, this computer tomograph has two radioscopic image camera systems that separate, also referred to as double source computer tomograph.
Background technology
By 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 record radioscopic image simultaneously and take, method is with different two X-ray tubes of voltage operation.Dual intensity is taken for example can distinguish organization types different in radioscopic image.For example, known for checking dual intensity (DE) the pulmonary perfusion CT (computer tomography) of pulmonary, its can detecting breathing defect or the perfusion that causes by thrombosis (Thromben) lose.But the in the situation that of this application, can occur the image artifacts causing by heart movement, these image artifacts critically affect perfusion analysis.
Summary of the invention
The technical problem to be solved in the present invention is, a kind of method is provided, and by the method, can in dual energy computed tomography (DECT), reduce motion artifacts.
Above-mentioned technical problem is by solving according to method of the present invention.The favourable embodiment of the method is the content of dependent claims or can from description below and embodiment, draws.
In advised method, by two radioscopic image camera systems that separate, with pitch, implement image recording, utilize this pitch for each layer of position z 0obtain n projection of quantity, these projections allow at each layer of a plurality of tomographic image of position reconstruction.This in known manner pitch be understood to rotation causes about each frame the bed feeding of computer tomograph and the ratio of the bed thickness of imaging layer.Preferably, in advised method, select 0.5 or be less than 0.5 pitch.According to common mode image recording itself, by the different x-ray voltage of two X-ray tubes, implement, for example, to utilize the interested region of different X ray energy acquisition inspection objects, pulmonary.
For each layer of position, thus 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, for this tomographic image, preferably combine respectively the measurement data of two radioscopic image camera systems.Because two radioscopic image camera systems stagger each other in double source computer tomograph, the angle of 90 ° is arranged in the frame of computer tomograph, thus in this case for half revolution is rebuild four/ enough once rotating because in order to rebuild 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 is only considered for determining possible motion in advised method.For each radioscopic image camera system, can rebuild dividually ground floor image.In this case thus for rebuilding half revolution that needs respectively frame.
According to these ground floor images, for each layer of position calculation tomographic image to the time of the picture material of tomographic image, go up the tolerance changing thus.This point preferably, by by tomographic image successively each other on each time, is namely realized according to the gray value differences phase Calais by pixel between the tomographic image that on the time, the rotating measurement data of part is rebuild successively each other.Value representation in this acquisition is measured in the locational motion of layer of the image recording variation according to this layer, and is called motion vector below.By obtaining about return back to the information of moving in the interested region of the locational inspection object of the rotating corresponding layer of part in part analyzing at each layer of locational ground floor image.Then, the trickleer time grid (Zeitraster) of each projection will be inserted in motion vector.This point can be realized by linear interpolation in the simplest situation.About each projection, this is in the situation that heart movement describes to draw that on the impact in interested region the suction movement (Pumpbewegung) corresponding to heart has the course of maximum and minima.It is evident that thus, in the strong movements stage, record which projection and record which projection in faint motion or quiescent phase.
For final dual intensity image reconstruction, wherein utilize the measurement data of two radioscopic image camera systems record for each radioscopic image camera system, to rebuild tomographic image dividually, so only consider the projection of recording in such stage at faint motion or quiescent phase or the measurement data of these projections.The upper threshold value of motion vector given 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 dual intensity tomographic image is only used following projection thus, wherein during measuring, does not move or only motion on a small quantity, thereby in image, reduces significantly motion artifacts.
Described method can be very advantageously for reducing the motion artifacts causing by heart movement, the motion artifacts while particularly pouring into CT (computer tomography) in dual intensity pulmonary.
Accompanying drawing explanation
According to embodiment, by reference to the accompanying drawings advised method is described further below.In accompanying drawing:
Fig. 1 shows the schematic diagram of the device of radioscopic image camera system in double source computer tomograph,
Fig. 2 shows the flow chart of the method that execution advises, and
Fig. 3 shows according to the schematic diagram of the time relationship of the example of advised method.
The specific embodiment
Fig. 1 schematically shows the device of two radioscopic image camera systems in double source computer tomograph strongly.Two radioscopic image camera systems that form by X-ray tube 1,3 with the X-ray detector 2,4 of X-ray tube positioned opposite are respectively arranged in frame 5 inside of computer tomograph under angle staggers the condition of 90 °.Can utilize in this way two radioscopic image systems to record respectively to stagger the projection of 90 ° simultaneously.Thus, measurement data analyzes and is redeveloped into the tomographic image of expectation in data processing unit 6.Patient is being positioned at during image recording on unshowned patient's bed in known manner, and this patient's bed moves through frame 5 in z direction.Z direction is corresponding to the direction perpendicular to page plane in the accompanying drawings.
In advised method, with little pitch, gather dual intensity measurement data, select in this example about 0.5 pitch for this reason.Measured value projection p thus 1(z 0) ..., p n(z 0) facilitate at position z 0image layer or the tomographic image of reconstruction.Due to 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 is constantly reconstituted in this half revolution that represents that the measurement data by the pi/2 angle complementation of two radioscopic image recording systems 1,2 or 3,4 forms and rebuilds.T sthe first measured value projection (p 1) the moment, this first measured value projection is facilitated at layer position z 0image reconstruction.By frame having been rotated to the angle of 90 °, can gather the projection about the angular range of 180 ° by merging the measurement data of two radioscopic image camera systems thus, and carry out thus half revolution and rebuild.For each k, obtain at picture position z 0the picture signal I at place k(z 0).Little pitch based on 0.5 herein can embodiment be rebuild as disjoint half revolution of k=8, to obtain at layer position z 08 tomographic images at place.From this image stack, can determine motion vector (Motionvektor, motion vector MM k).This for example can be by realizing upper adjacent picture signal of time or the gray value differences phase Calais by pixel of tomographic image:
MM k ( z 0 ) = Σ x ( I k ( x ) - I k - 1 ( x ) ) 2
At this, it can certainly be other gap size.The trickleer time grid of projection scanning will be inserted into thus in motion vector.Conventionally due to heart movement, estimate to have the smoothed curve of motion maximum and minima.For dual intensity, rebuild, the measurement data of namely separately rebuilding detector 2 and detector 4, only considers the measured value projection in the quiescent phase collection of motion vector for corresponding layer position.Obtain thus only comprising the dual intensity CT image of minimum movement artifact.Conventionally a small amount of ray of each image layer is that image is made contributions.In standardized situation in backprojector, consider this point.
Fig. 2 is schematically illustrated in the above-mentioned flow process in the situation of advised method for this reason.In Fig. 3, again illustrate temporal relation.At this, the top of Fig. 3 represents electrocardiogram, and this electrocardiogram shows heart movement.The exemplary expression time range 7 in bottom, in this time range, record is used at layer position z 0the measurement data that place rebuilds.Due to little feed speed, can from the measurement data at these time range 7 interior records, rebuild a plurality of tomographic images, a width tomographic image is rebuild in per quart revolution (pi/2), as this represents by arrow in the accompanying drawings.For this, be reconstituted in the measurement data of two radioscopic image camera systems of this combination.Then from these images calculation of motion vectors and in be inserted into the time grid of each projection.Bottom at accompanying drawing shows result, wherein schematically shows the temporal course of the motion vector obtaining in this way.According to expection, this motion vector has respectively maximum in heart strong movements stage scope and in the minima of quiescent phase.Thus, motion vector shows the region of the motion of varying strength.Thus for motion compensation rebuild dual intensity CT image, only use the projection that comes from the stage 8 of not moving as far as possible.

Claims (8)

1. utilize computer tomograph in dual energy computed tomography, to reduce a method for motion artifacts, described 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 of position, and these projections allow at each layer of a plurality of not identical tomographic image of position reconstruction,
-for rebuilding a plurality of ground floor images in the measurement data of the rotating projection of part successively each other on the time of each layer of position radioscopic image camera system (1-4),
-for each layer of position, calculate respectively the tomographic image of ground floor image to the upper tolerance changing of time of the picture material of tomographic image, and by interpolation, determine the temporal variation that is projected to projection,
-select following projection, the temporal variation that is wherein projected to projection is less than threshold value given in advance, and
-for each radioscopic image camera system (1-4), rebuild second layer image, 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, for each radioscopic image camera system (1-4), carries out dividually the reconstruction of described ground floor image.
3. method according to claim 1, is characterized in that, combines respectively the measurement data of two radioscopic image camera systems (1-4) for the reconstruction of described ground floor image.
4. method according to claim 3, is characterized in that, for each layer of position, rebuilds ground floor image successively each other respectively from the time of radioscopic image camera system (1-4) in the measurement data of four/single-revolution.
5. according to the method described in any one in claim 1 to 4, it is characterized in that, the pitch by≤0.5 is carried out image recording.
6. according to the method described in any one in claim 1 to 4, it is characterized in that, by gray value differences phase Calais between the respective pixel at each ground floor image being obtained to tomographic image to the tolerance changing on the time of the picture material of tomographic image.
7. according to the method described in any one in claim 1 to 4, for reducing cardiac motion artefacts.
8. according to the method described in any one in claim 1 to 4, for reducing 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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