CN103784160A - Correction device and correction method for geometric position of cone beam CT system - Google Patents
Correction device and correction method for geometric position of cone beam CT system Download PDFInfo
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- CN103784160A CN103784160A CN201410081224.XA CN201410081224A CN103784160A CN 103784160 A CN103784160 A CN 103784160A CN 201410081224 A CN201410081224 A CN 201410081224A CN 103784160 A CN103784160 A CN 103784160A
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Abstract
The invention discloses a correction device and correction method for the geometric position of a cone beam CT system. The correction device comprises a supporting body, a vertical rod, a horizontal ring and locating balls. The vertical rod, the horizontal ring and the locating balls are all fixed to the supporting body. All points on the horizontal ring are arranged in the same face. The vertical rod is perpendicular to the plane where the horizontal ring is located. The two locating balls are arranged on the two sides of the horizontal ring respectively in the direction parallel to the vertical rod, and the distances between the locating balls and the horizontal ring are equal. The geometric correction device including the vertical rod, the horizontal ring and the locating balls is adopted, the projection characteristics of corresponding points, lines and faces are observed, the size and direction of the displacement errors and the angle errors of a detector are judged, corresponding adjustment is carried out, and therefore the geometric correction of the cone beam CT system is achieved faster and more accurately. After correction is completed, a relatively precise geometric parameter value can be calculated according to imaging of one or more points in the device at different positions.
Description
Technical field
The present invention relates to biomedical imaging field, be specifically related to correcting unit and the bearing calibration thereof of a kind of cone-beam CT system geometric position.
Background technology
Cone-beam CT system adopts cone type X-ray bundle and pixel detection array to carry out noninvasive imaging to testee.The feature of cone-beam CT system maximum is that spatial resolution is high, can reach tens microns.But in its image reconstruction, also there will be various artifacts, reconstructed image quality is had a strong impact on.Wherein, the geometry of machinery error of CT system is to cause that artifact produces a kind of key factor.In the FDK of cone-beam CT system image reconstruction algorithm, require x-ray source focus, testee center of rotation, detector image-forming to be centered close to straight line, and detector pixel array place plane is perpendicular to this straight line.But due to the precision problem such as machining and installation, the position of x-ray source, testee, detector cannot meet the desired desirable geometrical relationship of algorithm.If do not carry out the geometric correction of CT system, can cause ring-type or banded artifact, fuzzy etc. in image rebuilding, reduce reconstructed image spatial resolution.Therefore, must carry out geometric correction to cone-beam CT system.
Lorenz von Smekal, Marc Kachelrie β etc., in Geometric misalignment and calibration in cone-beam tomography, propose a kind of Fourier transformation method based on point-like project objects, can obtain the geometric parameter of whole system.By obtaining projection (as zirconium point) and the corresponding projection angle information of multiple point-like objects of multiple angles, progressively calculate the geometric parameter of system.But, in the method, owing to need to finding the barycenter of multiple subpoints, and subpoint barycenter is carried out to elliptic curve matching, and the measurement of model parameter in calculating.Be easy to introduce error.The method corner time error outside the face of calculating detector is larger.Kai Yang, Alexander L.C.Kwan etc. are again on this basis, a kind of method of geometric correction has been proposed in A geometric calibration method for cone beam CT systems, the outer corner of face that first the method has proved detector is very little to the measurement image of image reconstruction and geometric parameter, and then the projection of point-like object by multiple angles and the information of angle progressively calculate the geometric parameter of system.This method can well calculate the geometric parameter of system, because the treatment step of its data is the same with Fourier methods, so the method for its shortcoming and Fourier transformation is the same.
Yang Min etc. proposes a kind of method in Non-linear least square estimation of geometrical parameters for Cone-beam three dimensional computed tomography article, this method is by theoretical projection and the actual projection contrast of point, carry out matching by nonlinear least square method, realize the measurement of geometric parameter.This method does not need to know in advance accurate position a little, but the method is more responsive to initial value.
Roug é e et al provides a kind of method of estimating system parameter, and by obtaining the information of projection of point of some known location, suitable calibrating patterns reference point Spiral distribution used is in known position.But this method is more responsive to original state, the number of the reference point to use is also more responsive, and the precision magnitude of parameter estimation changes span too greatly simultaneously.
The people such as Yao Ming propose a kind of orthogonal filament model in " adjustment of detector CT system and parameter acquiring method ", by the projection of design ad-hoc location and angle, according to projecting figure feature, system structure are adjusted and calculated interrelated geometrical parameters.The systematic parameter error that the method obtains is less than 0.5%.But the method is very high to the required precision of model, and in practical operation, the adjusting of every kind of deviation is needed in a certain order, certainly will cause the accumulative effect of operate miss in adjustment process.Regulate because the method selected ad-hoc location, angle etc. cannot realize Real-time and Dynamic in practical operation simultaneously, can cause adjustment process very consuming time, say not ideal enough from practicality.
The people such as Smekal have proposed a kind of method of inlaying two circle steel balls on low density material in " Accuratetechnique for complete geometric calibration of cone-beam computed tomography system ".On a cylinder, inlay upper and lower two-layer steel ball, and each 12 up and down, on circumference, being uniformly distributed, the relative position between steel ball is known, and the relative position of the projection centre by it on detector carries out geometric parameter correction.But in the method, the corresponding relation of projection and former steel ball is easy to obscure.
Patent CN202104929U has improved said method, has added again one or more positioning balls between two-layer steel ball, makes the corresponding relation of projection and former steel ball clearer and more definite, and the method is easier on calculating simultaneously.But the precision of these two kinds of methods is subject to the interference of several factors, for example, proofread and correct the certainty of measurement of the relative position between machining accuracy, the steel ball of imitating body etc.
Summary of the invention
In order to overcome problems of the prior art, the invention provides the correcting unit and the bearing calibration thereof that propose a kind of cone-beam CT system geometric position, can realize more high-precision calibration, and obtain more accurate geometric parameter values.
One object of the present invention is to provide the correcting unit of a kind of cone-beam CT system geometric position.
The correcting unit of cone-beam CT system of the present invention geometric position comprises: supporter, vertical bar, horizontal loops and two positioning beads; Wherein, vertically bar, horizontal loops and positioning bead are all fixed on supporter; Each point in horizontal loops is positioned at the same face; Vertically bar is perpendicular to the plane at horizontal loops place; Two positioning beads lay respectively at the both sides of horizontal loops along the direction parallel with vertical bar, be positioned at same perpendicular with vertical bar, and equate to the distance of horizontal loops.
Horizontal loops is about the perpendicular symmetry at vertical bar and two positioning bead places; Or adopt two horizontal location pearls, two horizontal location pearls lay respectively at the both sides of vertical bar along the direction parallel with horizontal loops, and equate to the horizontal direction distance of vertical bar.
Supporter can be solid, housing or framework.
The material that supporter adopts, is less than to the attenuation quotient of ray the material that vertical bar, horizontal loops and positioning bead adopt, so that after transmission of radiation, can clearly tell the projection of vertical bar, horizontal loops and positioning bead at detector.Supporter adopts the material little to attenuation coefficient, as lucite, polrvinyl chloride and resin etc.; Vertically bar, horizontal loops and positioning bead adopt the material large to attenuation coefficient, as tungsten, copper, molybdenum, lead and zirconium etc.
Correcting unit of the present invention is proofreaied and correct for the geometric position of cone-beam CT system, and cone-beam CT system comprises: turntable, adjustable base, regulating platform, detector, radiographic source and radiographic source platform; Wherein, regulating platform, adjustable base and radiographic source platform are located along the same line; Radiographic source platform and regulating platform lay respectively at two ends, and radiographic source is positioned on radiographic source platform; Detector is placed on regulating platform; Adjustable base is between regulating platform and radiographic source platform, and turntable is arranged on adjustable base, and the correcting unit of cone-beam CT system geometric position is placed on turntable.
Regulating platform has 6 degree of freedom, can move along three mutually perpendicular axis, and can rotate around three mutually perpendicular axis.Radiographic source platform has 6 degree of freedom, can move along three mutually perpendicular axis, and can rotate around three mutually perpendicular axis.Adjustable base has 3 degree of freedom, can move along three mutually perpendicular axis.
Ray source focus is positioned at radiographic source inside, and central ray sends from ray source focus, and along continuous straight runs is beaten on detector.Correcting unit is placed in the FOV of cone-beam CT system, can be by respective point, line and ring being observed at the projection properties of ad-hoc location or angle at cone-beam CT system, judge the displacement error of detector, the size and Orientation of angular error, and make corresponding adjusting, thereby realize accurate cone-beam CT system geometric correction more fast.After correction completes, can, to some or multiple in diverse location imaging in device, derive respective formula according to the position of point and the geometrical relationship of its projected position, calculate more accurate geometric parameter values mutually.
Another object of the present invention is to provide a kind of bearing calibration of proofreading and correct for cone-beam CT system geometric position.
Radiographic source sends cone-beam x-ray, and ray source focus is positioned in X-axis, and central ray is propagated along X-axis, and turntable rotates around Z axis, and detector to be adjusted is positioned at UO
2v plane, O
2for the imaging center of detector to be adjusted.
Bearing calibration of proofreading and correct for cone-beam CT system geometric position of the present invention, comprises the following steps:
1) correcting unit is placed on turntable, vertically bar is perpendicular to turntable, and radiographic source is launched cone-beam x-ray, and central ray is along X-axis;
2) the face internal rotation angle degree error of adjusting detector:
Vertical bar is carried out to projection, on detector, form projection straight line, observe the pixel column whether projection straight line drops on detector, regulating platform rotates to regulate the detector anglec of rotation around X-axis, make the projection straight line of vertical bar drop on detector pixel column, there is not face internal rotation angle degree error in detector now;
3) the imaging center O of adjusting detector
2displacement error along U axle:
First, vertical bar is rotated and projection, whether the projected position of observing on detector changes, and by regulating the position of correcting unit on turntable, makes the rear projected position of vertical bar rotation constant, and now vertically bar is positioned at rotating shaft;
Then, observe the projection of vertical bar, regulate the displacement of detector along U axle by regulating platform, make the projection of vertical bar be positioned at the center pixel row of detector, the now imaging center O of detector
2without the displacement error along U axle;
4) the imaging center O of adjusting detector
2displacement error along V axle:
First, to horizontal loops projection, whether be straight line, regulate the height of turntable by adjustable base if observing projection of shape, and the projection of shape that makes horizontal loops is horizontal linear, and now horizontal loops is positioned at the horizontal plane at central ray place;
Then, the center pixel whether projection straight line of eye-level ring drops on detector is capable, to regulate detector along the displacement of V axle, make the projection straight line of horizontal loops be positioned at the center pixel of detector capable, the now imaging center O of detector by the displacement along V axial adjustment regulating platform
2without the displacement error along V axle;
5) regulate detector angular error outside the face of U axle:
First, two positioning beads are carried out to projection, rotate by turntable, the projection Ban center of two positioning beads is dropped in the projection straight line of locating rod, now two positioning beads are positioned at the perpendicular at central ray place;
Then, whether the projection Ban center of observing two positioning beads equates to the distance of the projection straight line of horizontal loops, around U axle rotation, the projection Ban center of two positioning beads is equated by regulating platform to the distance of the projection straight line of horizontal loops, now detector around U axle without face outside angular error;
6) regulate detector angular error outside the face of V axle:
Horizontal loops is about the perpendicular symmetry at vertical bar and positioning bead place, the projection straight line of eye-level ring, by regulating platform around V axle rotation, the two ends of projection straight line that make horizontal loops on U direction of principal axis about V axial symmetry, now detector around V axle without face outside angular error;
Or adopt two horizontal location pearls, two horizontal location pearls lay respectively at the both sides of vertical bar along the direction parallel with horizontal loops, and the horizontal direction distance to vertical bar equates, observe the projection of two horizontal location pearls, rotate around V axle by regulating platform, make being projected on U direction of principal axis about V axial symmetry of two horizontal location pearls, now detector around V axle without face outside angular error;
Wherein, step 2) to 4) order interchangeable, and step 5) and 6) order interchangeable.
Further, the present invention obtains system geometric parameter after being also included in cone-beam CT system being proofreaied and correct for how much.
System geometric parameter comprises that ray source focus is to the distance of rotating shaft, ray source focus to the distance of the imaging plane of detector and the projection coordinate of central ray.The projection coordinate of central ray can directly read, and ray source focus can calculate by the geometrical relationship of the position of positioning bead and its projection to the distance of the imaging plane of detector to distance and the ray source focus of rotating shaft.
Advantage of the present invention:
The present invention adopts the correcting unit that comprises vertical bar, horizontal loops and positioning bead, by the projection properties of respective point, line dough-making powder is observed, judge the displacement error of detector, the size and Orientation of angular error, and make corresponding adjusting, thereby realize accurate cone-beam CT system geometric correction more fast.After correction completes, can, to some or multiple in diverse location imaging in device, derive respective formula according to the position of point and the geometrical relationship of its projected position, calculate more accurate geometric parameter values mutually.
Accompanying drawing explanation
Fig. 1 is the structural representation of an embodiment of the correcting unit of cone-beam CT system of the present invention geometric position;
Fig. 2 is the structural representation that adopts a correcting unit of the present invention embodiment that cone-beam CT system is proofreaied and correct;
Fig. 3 is the principle schematic of cone-beam CT system of the present invention;
Fig. 4 is the schematic diagram of the geometric error situation of several detectors, wherein, be (a) and (b) projection of detector in XOZ plane, (c) be (d) projection of detector at XOY plane, (e) be the projection of detector in YOZ plane;
Fig. 5 is the schematic diagram that positioning bead of the present invention moves the geometrical relationship of the projection of front and back positioning bead and positioning bead.
The specific embodiment
Below in conjunction with accompanying drawing, by embodiment, the present invention will be further described.
As shown in Figure 1, the correcting unit of the cone-beam CT system geometric position of the present embodiment comprises: supporter 11, vertical bar 12, horizontal loops 13 and positioning bead 14; Wherein, vertically bar 12, horizontal loops 13 and positioning bead 14 are all fixed on supporter 11; Each point in horizontal loops 13 is positioned at same plane; Vertically bar 12 is perpendicular to the plane at horizontal loops 13 places; Vertically bar 12 is positioned at horizontal loops 13 center, and horizontal loops 13 is about vertical bar 12 centrosymmetry; Two positioning beads 14 lay respectively at the both sides of horizontal loops 13 along the direction parallel with vertical bar 12, and equate to the distance of horizontal loops 13.
As shown in Figure 2, cone-beam CT system comprises: turntable 5, adjustable base 4, regulating platform 2, detector 3, radiographic source 7 and radiographic source platform 6; Wherein, regulating platform 2, adjustable base 4 and radiographic source platform 6 are arranged on optical table 8 and on same straight line; Radiographic source platform 6 and regulating platform 2 lay respectively at the two ends of optical table 8, and radiographic source 7 is positioned on radiographic source platform 6; Detector 3 is placed on regulating platform 2; Adjustable base 4 is between regulating platform 2 and radiographic source platform 6, and turntable 5 is arranged on adjustable base 4, and the correcting unit 1 of cone-beam CT system geometric position is placed on turntable 5.
The table top flatness 0.10mm/m of optical table 8
2, surface uniform distribution standard M6 screw.Detector 3, radiographic source 7 are fixed on the table top two ends of optical table 8 by regulating platform 2 and radiographic source platform 6 respectively, and turntable 5 is fixed on optical table 8 by adjustable base 4, and three is centered close to straight line.Detector 3 pixel sizes are 74.8 μ m, and pel array is 1944 × 1536.Turntable 5 is provided with motor, can be by the computer control anglec of rotation, can realize continuously, be interrupted rotation, minimum step value 0.5 degree.Radiographic source 7 is point source, and focal spot size is 40 μ m.Regulating platform 2 and radiographic source platform 6 can be realized by spiral button the adjusting of 6 degree of freedom, comprise along X, Y and Z-direction displacement adjusting and rotate around X, Y and Z axis, and degree of regulation is 0.02mm.Adjustable base 4 is for fixing and adjusting turntable 5, because the angular error of turntable 5 can be summed up to the angular error η of detector 7, therefore adjustable base only need be realized the adjusting of 3 degree of freedom, regulate along the displacement of X, Y and Z-direction, degree of regulation is 0.02mm.
As shown in Figure 3, S represents light source, and central ray is propagated along X-axis, and XYZ coordinate system is the space coordinates of setting up with central ray and rotating shaft, and O is initial point.UV coordinate system is the plane coordinate system of setting up with the central row of actual detector and central series, and ideally, this plane parallel is in YOZ, and O
2be positioned on OX axle, U is parallel to Y, and V is parallel to Z.Detector to be adjusted is positioned at VO
2u plane, O
2for the imaging center of detector to be adjusted.
Fig. 4 is the schematic diagram of the geometric error situation of several detectors.Wherein, be (a) and (b) projection of detector in XOZ plane, as shown in Figure 4 (a), detector rotates θ around U axle; As shown in Figure 4 (b), the imaging center O of detector
2apart from differ Δ V along V wheelbase from O.Figure (c) and (d) be the projection of detector at XOY plane, as shown in Figure 4 (c), detector rotates β around V axle; As shown in Fig. 4 (d), the imaging center O of detector
2apart from differ Δ U along U wheelbase from O.As shown in Fig. 4 (e), detector rotates η around X-axis.
Utilize the correcting unit of the cone-beam CT system geometric position of the present embodiment to proofread and correct for how much cone-beam CT system, bearing calibration comprises the following steps:
1) correcting unit is placed on turntable, guarantees that vertical bar 12, horizontal loops 13 and positioning bead 14 are all positioned at field range (Field of View, FOV), vertically bar 12 is perpendicular to turntable 5, and radiographic source 7 is launched cone-beam x-ray, and central ray is along X-axis.
2) regulate the face internal rotation angle degree error η of detector around X-axis:
For example, in the time that the projection straight line of vertical bar 12 is the inclination of upper left, bottom right, the angular error η that shows detector 3 is rotated and causes around X-axis clockwise by detector 3 edges, should be in the counterclockwise direction around the suitable rotary detector of X-axis, if vertically the projection straight line of bar 12 is that upper right, lower-left tilts after regulating, show that last time adjusting angle was excessive, should be along clockwise direction around the suitable rotary detector of X-axis; So repeatedly regulate, until the projection straight line of vertical bar 12 drops on certain pixel column of detector.Other situations in like manner regulate.
3) the imaging center O of adjusting detector
2displacement error Δ U along U axle:
First, to vertical bar 12 rotation projections, whether the projected position of observing on detector changes, if in rotary course, vertically the projected position of bar 12 is constant, show that vertical bar 12 is positioned at rotating shaft position, if in rotary course, vertically the projected position of bar 12 changes, show that vertical bar 12 is not in rotating shaft position, by regulating the position of correcting unit 1 on turntable 5, make the rear projected position of vertical bar 12 rotation constant, now vertically bar 12 is positioned at rotating shaft.
For example, when vertical bar 12 rotates a circle the region of projection while being rectangle, observe it and reach rectangle along U direction of principal axis boundary position; Control turntable 5 rotations to vertical bar 12 projections and reach aforementioned boundary position, now along Y direction shift calibrating device 1, make vertical bar 12 near rotating shaft; Re-imaging, repeats aforementioned operation, until vertically the rear projected position of bar 12 rotation is constant.Other situations in like manner regulate.
Then, whether the projection straight line of observing vertical bar 12 drops on the center pixel row of detector 3, if the projection straight line of vertical bar 12 drops on the center pixel row of detector 3, shows not presence bit shift error Δ U of detector; If vertically the projection straight line of bar 12 is not listed as at the center pixel of detector 3, show detector presence bit shift error Δ U, regulate the displacement of detector 3 along U axle by regulating platform 2, make the projection of vertical bar be positioned at the center pixel row of detector, the now imaging center O of detector
2nothing is along U axial displacement error delta U.
For example, in the time that the projection straight line place of vertical bar 12 pixel column is positioned at UV coordinate plane+U scope, show that detector 3 exists the displacement error Δ U of edge-U direction, should be along+suitable the mobile detector of U direction, if vertically the projection straight line of bar 12 is positioned at UV coordinate plane-U scope after regulating, show last time to regulate displacement excessive, should be along-suitable the mobile detector of U direction; So repeatedly regulate, until the projection straight line of vertical bar 12 drops on the center pixel row of detector 3.Other situations in like manner regulate.
4) the imaging center O of adjusting detector
2displacement error Δ V along V axle:
First, to horizontal loops projection, whether observe projection of shape is straight line, if the projection of shape of horizontal loops 13 is horizontal linear, show that horizontal loops 13 is positioned at the central ray place horizontal plane of radiographic source 7, if the projection of shape of horizontal loops 13 is oval, show that horizontal loops 13 is not positioned at the central ray place horizontal plane of radiographic source 7, regulate the height of turntable by adjustable base, the projection of shape that makes horizontal loops is horizontal linear, and now horizontal loops 13 is positioned at the horizontal plane at central ray place.
For example, when horizontal loops 13 be projected as ellipse time, regulate turntable 5 rising micro-displacements by variable base 4, if it is large that the oval V direction of principal axis axial length of the now projection of horizontal loops 13 becomes, show that horizontal loops 13, higher than radiographic source central ray place horizontal plane, should suitably regulate the height of turntable downwards, now, if the projection of horizontal loops 13 is still that ellipse and V direction of principal axis axial length become greatly after regulating, show that aforementioned adjusting displacement is excessive, should upwards suitably regulate turntable 5 height; If the projection of horizontal loops 13 is still for ellipse and V direction of principal axis axial length diminish after regulating, show that aforementioned adjustable range is too small, horizontal loops 13 is still higher than radiographic source central ray place horizontal plane, should continue suitably to regulate turntable 5 height downwards, or show that aforementioned adjustable range is excessive, horizontal loops 13 is lower than the horizontal plane at radiographic source central ray place, but diminishes before regulating with radiographic source central ray place the horizontal plane; So repeatedly regulate, until horizontal loops 13 be projected as horizontal linear.Other situations in like manner regulate.
Then, the center pixel whether projection straight line of eye-level ring 13 drops on detector 3 is capable, if the projection straight line of horizontal loops 13 drops on detector pixel central row, shows not 3 presence bit shift error Δ V of detector; If it is capable that the projection straight line of horizontal loops 13 does not drop on the pixel center of detector 3, show detector 3 presence bit shift error Δ V, the displacement along V axle with adjusting detector 3 by the displacement along V axial adjustment regulating platform 2, make the projection straight line of horizontal loops 13 be positioned at the center pixel of detector 3 capable, the now imaging center O of detector
2without the displacement error Δ V along V axle.
For example, in the time that the projection straight line of horizontal loops 13 is positioned at UV coordinate plane+V scope, show that detector exists the displacement error Δ V of edge-V direction, should be along+suitable the mobile detector of V direction, if the projection straight line of horizontal loops 13 is positioned at UV coordinate plane-V scope after regulating, show last time to regulate displacement excessive, should be along-suitable the mobile detector of V direction; So repeatedly regulate, until that the projection straight line of horizontal loops 13 drops on the pixel center of detector 3 is capable.Other situations in like manner regulate.
5) regulate detector angle error theta outside the face of U axle:
First, two positioning beads 14 are carried out to projection, observe the projection speckle of positioning bead 14 and the relative position of the projection of vertical bar 12.If positioning bead 14 projection Ban centers are dropped in the projection straight line of vertical bar 12, show that positioning bead 14 is positioned at radiographic source central ray place perpendicular; If positioning bead 14 projection Ban centers are not in the projection straight line of vertical bar 12, show that positioning bead 14 is not in the perpendicular at the central ray place of radiographic source 7, rotate by turntable 5, the projection Ban center of two positioning beads 14 is dropped in the projection straight line of locating rod 12, and now two positioning beads 14 are positioned at the perpendicular at central ray place.
For example, when positioning bead 14 is positioned at the side near radiographic source 7 on turntable 5, and within the scope of the drop on-U of projection speckle of positioning bead 14 time, show that positioning bead 14 should move to+X ,+Y-direction, should suitably regulate in the counterclockwise direction turntable 5 angles, if after regulating, be positioned at drop on+U of the projection speckle scope of positioning bead 14 above, show that last time adjusting angle was excessive, should suitably regulate along the pin direction of taking advantage of a situation the angle of turntable 5.So repeatedly regulate, until the projection Ban center of positioning bead 14 is dropped in the projection straight line of vertical bar 12.Other situations in like manner regulate.
Then, whether the projection Ban center of observing two positioning beads 14 equates to the distance of the projection straight line of horizontal loops 13, if the projection Ban center of positioning bead 14 is equal to the distance of the projection straight line of horizontal loops 13, shows that detector 3 does not exist angular error θ; If positioning bead 14 projection Ban centers are unequal to the distance of the projection straight line of horizontal loops 13, show that detector exists angular error θ, rotate around U axle by regulating platform, the projection Ban center that makes two positioning beads equates to the distance of the projection straight line of horizontal loops, now detector 3 around U axle without face outside angle error theta.
For example, in the time being positioned at projection Ban center that the projection Ban center of positioning bead 14 of top is greater than to the distance of the projection straight line of horizontal loops 13 positioning bead 14 that is positioned at below and arriving the distance of projection straight line of horizontal loops 13, showing that detector 3 exists along clockwise direction rotates around U axle the angular error θ causing, should be in the counterclockwise direction around the suitable rotary detector of U axle, if after regulating, the projection Ban center that is positioned at the positioning bead 14 of top is less than the projection Ban center of the positioning bead 14 that is positioned at below to the distance of the projection straight line of horizontal loops 13 to the distance of the projection straight line of horizontal loops 13, show that last time adjusting angle was excessive, now detector 3 exists along clockwise direction and rotates around U axle the angular error θ causing, should be along clockwise direction around the suitable rotary detector of U axle.So repeatedly regulate, until the projection Ban center of two positioning beads 14 equates to the distance of the projection straight line of horizontal loops 13.Other situations in like manner regulate.
6) regulate detector angular error β outside the face of V axle:
The projection straight line of eye-level ring 13, the two-end-point of the projection straight line of horizontal loops 13 in corresponding horizontal loops 13 2 in Y direction about X-axis symmetry, the i.e. Y coordinate figure equal and opposite in direction of 2, if the two-end-point of the projection straight line of horizontal loops 13 equates to the distance of V axle, the projection straight line that is horizontal loops 13 is equated by two sections of straight lengths that projection was divided into of vertical bar 12, shows that detector does not exist angular error β; If the projection straight line of horizontal loops 13 is unequal by two sections of straight lengths that projection was divided into of vertical bar 12, show that detector 3 exists angular error β, regulate detector 3 by regulating platform 2 around the rotation of V axle, the two ends of projection straight line that make horizontal loops 13 on U direction of principal axis about V axial symmetry, now detector 3 around V axle without face outside angular error β;
Wherein, step 2) to 4) order interchangeable, and step 5) and 6) order interchangeable.
The present invention, after cone-beam CT system is proofreaied and correct for how much, further comprises and obtains system geometric parameter.
System geometric parameter comprises that ray source focus is to the distance SO of rotating shaft, ray source focus to the distance SD of the imaging plane of detector and the (u of projection coordinate of central ray
0, v
0).(the u of projection coordinate of central ray
0, v
0) can directly read, ray source focus can calculate by the geometrical relationship of the position of positioning bead 14 and its projection to the distance SD of the imaging plane of detector to distance SO and the ray source focus of rotating shaft.The method that gets parms is as follows:
The spacing of two positioning beads of definition is that l, two positioning beads are r to the distance of vertical bar 12, and the value of l and r can be by measuring.
(1) after geometric correction completes to cone-beam CT system, read the intersecting point coordinate of the projection straight line of vertical bar 12 and the projection straight line of horizontal loops 13, be the projection coordinate (u0, v0) of central ray; The projection centre coordinate that calculates the positioning bead 14 that is positioned at top, is designated as (u1, v1);
(2) regulate turntable height, make the positioning bead 14 that is positioned at top along Z-direction displacement d, the projection centre coordinate that compute location pearl 14 is current, be designated as (u2, v2), the geometrical relationship of the projection centre of positioning bead 14 positions and positioning bead before and after can moving, as shown in Figure 5.Can obtain following formula according to Similar Principle of Triangle:
Above-mentioned two formulas are solved, can obtain ray source focus to rotating shaft d apart from SO and ray source focus to the imaging plane of detector the value apart from SD.
So far, the geometric parameter after cone-beam CT system correction has been obtained.
Need explanation, in said method, the relative size of d and l is without specific limited, but need guarantee that positioning bead 14 is in the FOV of cone-beam CT system.Do not limit positioning bead 14 and move along Z-direction, also can be moving along X-axis or y-axis shift, specific formula for calculation is derived according to practical situation.Do not require that positioning bead 14 is positioned at radiogenic central ray place perpendicular, only need to determine that positioning bead 14 and rotating shaft are along X-direction distance.
And the formula proving of this process does not limit position and the projection relation of only choosing positioning bead 14.Ray source focus can be by calculating the geometrical relationship of other positions and projected position apart from the value of SD to the imaging plane of detector apart from SO, ray source focus to rotating shaft.As also optional one or more points on one or more points, supporter 11 etc. of getting in horizontal loops 13, only need meet taken point location aware.In the time choosing difference, concrete computing formula should be derived according to practical situation.
Finally it should be noted that, the object of publicizing and implementing mode is to help further to understand the present invention, but it will be appreciated by those skilled in the art that: without departing from the spirit and scope of the invention and the appended claims, various substitutions and modifications are all possible.Therefore, the present invention should not be limited to the disclosed content of embodiment, and the scope that the scope of protection of present invention defines with claims is as the criterion.
Claims (10)
1. a correcting unit for cone-beam CT system geometric position, is characterized in that, the correcting unit (1) of described cone-beam CT system geometric position comprises: supporter (11), vertical bar (12), horizontal loops (13) and two positioning beads (14); Wherein, described vertical bar (12), horizontal loops (13) and positioning bead (14) are all fixed on supporter (11); Each point in described horizontal loops (13) is positioned at the same face; Described vertical bar (12) is perpendicular to the plane at horizontal loops (13) place; Described two positioning beads (14) lay respectively at the both sides of horizontal loops (13) along the direction parallel with vertical bar (12), be positioned at same perpendicular with vertical bar, and equate to the distance of horizontal loops (13).
2. the correcting unit of cone-beam CT system as claimed in claim 1 geometric position, is characterized in that, described horizontal loops (13) is about the perpendicular symmetry at vertical bar (12) and two positioning beads (14) place; Or adopt two horizontal location pearls, two horizontal location pearls lay respectively at the both sides of vertical bar (12) along the direction parallel with horizontal loops (13), and equate to the horizontal direction distance of vertical bar (12).
3. the correcting unit of cone-beam CT system as claimed in claim 1 geometric position, is characterized in that, described supporter (11) is solid, housing or framework.
4. the correcting unit of cone-beam CT system as claimed in claim 1 geometric position, is characterized in that, the material that described supporter (11) adopts is less than to the attenuation quotient of ray the material that vertical bar (12), horizontal loops (13) and positioning bead (14) adopt; The material that described supporter (11) adopts comprises lucite, polrvinyl chloride and resin; The material that described vertical bar (12), horizontal loops (13) and positioning bead (14) adopt comprises tungsten, copper, molybdenum, lead and zirconium.
5. the correcting unit of cone-beam CT system as claimed in claim 1 geometric position, it is characterized in that, proofread and correct geometric position for cone-beam CT system, and described cone-beam CT system comprises: turntable (5), adjustable base (4), regulating platform (2), detector (3), radiographic source (7) and radiographic source platform (6); Wherein, described regulating platform (2), adjustable base (4) and radiographic source platform (6) are located along the same line; Described radiographic source platform (6) and regulating platform (2) lay respectively at two ends, and radiographic source (7) is positioned on radiographic source platform (6); Described detector (3) is placed on regulating platform (2); Described adjustable base (4) is positioned between regulating platform (2) and radiographic source platform (6), and it is upper that described turntable (5) is arranged on adjustable base (4), and the correcting unit (1) of described cone-beam CT system geometric position is placed on turntable (5).
6. the correcting unit of cone-beam CT system as claimed in claim 5 geometric position, is characterized in that, described regulating platform (2) moves along three mutually perpendicular axis, and rotates around three mutually perpendicular axis.
7. the correcting unit of cone-beam CT system as claimed in claim 5 geometric position, is characterized in that, described radiographic source platform (6) moves along three mutually perpendicular axis, and rotates around three mutually perpendicular axis.
8. the correcting unit of cone-beam CT system as claimed in claim 5 geometric position, is characterized in that, described adjustable base (4) moves along three mutually perpendicular axis.
9. a bearing calibration of proofreading and correct for cone-beam CT system geometric position, radiographic source sends cone-beam x-ray, and ray source focus is positioned in X-axis, and central ray is propagated along X-axis, and turntable rotates around Z axis, and detector to be adjusted is positioned at UO
2v plane, O
2for the imaging center of detector to be adjusted, it is characterized in that, comprise the following steps:
1) correcting unit is placed on turntable, vertically bar is perpendicular to turntable, and radiographic source is launched cone-beam x-ray, and central ray is along X-axis;
2) the face internal rotation angle degree error of adjusting detector:
Vertical bar is carried out to projection, on detector, form projection straight line, observe the pixel column whether projection straight line drops on detector, regulating platform rotates to regulate the detector anglec of rotation around X-axis, make the projection straight line of vertical bar drop on detector pixel column, there is not face internal rotation angle degree error in detector now;
3) the imaging center O of adjusting detector
2displacement error along U axle:
First, vertical bar is rotated and projection, whether the projected position of observing on detector changes, and by regulating the position of correcting unit on turntable, makes the rear projected position of vertical bar rotation constant, and now vertically bar is positioned at rotating shaft;
Then, observe the projection of vertical bar, regulate the displacement of detector along U axle by regulating platform, make the projection of vertical bar be positioned at the center pixel row of detector, the now imaging center O of detector
2without the displacement error along U axle;
4) the imaging center O of adjusting detector
2displacement error along V axle:
First, to horizontal loops projection, whether be straight line, regulate the height of turntable by adjustable base if observing projection of shape, and the projection of shape that makes horizontal loops is horizontal linear, and now horizontal loops is positioned at the horizontal plane at central ray place;
Then, the center pixel whether projection straight line of eye-level ring drops on detector is capable, to regulate detector along the displacement of V axle, make the projection straight line of horizontal loops be positioned at the center pixel of detector capable, the now imaging center O of detector by the displacement along V axial adjustment regulating platform
2without the displacement error along V axle;
5) regulate detector angular error outside the face of U axle:
First, two positioning beads are carried out to projection, rotate by turntable, the projection Ban center of two positioning beads is dropped in the projection straight line of locating rod, now two positioning beads are positioned at the perpendicular at central ray place;
Then, whether the projection Ban center of observing two positioning beads equates to the distance of the projection straight line of horizontal loops, around U axle rotation, the projection Ban center of two positioning beads is equated by regulating platform to the distance of the projection straight line of horizontal loops, now detector around U axle without face outside angular error;
6) regulate detector angular error outside the face of V axle:
Horizontal loops is about the perpendicular symmetry at vertical bar and positioning bead place, the projection straight line of eye-level ring, by regulating platform around V axle rotation, the two ends of projection straight line that make horizontal loops on U direction of principal axis about V axial symmetry, now detector around V axle without face outside angular error;
Or adopt two horizontal location pearls, two horizontal location pearls lay respectively at the both sides of vertical bar along the direction parallel with horizontal loops, and the horizontal direction distance to vertical bar equates, observe the projection of two horizontal location pearls, rotate around V axle by regulating platform, make being projected on U direction of principal axis about V axial symmetry of two horizontal location pearls, now detector around V axle without face outside angular error;
Wherein, step 2) to 4) order interchangeable, and step 5) and 6) order interchangeable.
10. bearing calibration as claimed in claim 9, it is characterized in that, after being further included in cone-beam CT system how much being proofreaied and correct, obtain system geometric parameter, system geometric parameter comprises that ray source focus is to the distance of rotating shaft, ray source focus to the distance of the imaging plane of detector and the projection coordinate of central ray; Directly read the projection coordinate of central ray, calculate the distance of ray source focus to the distance of rotating shaft and ray source focus to the imaging plane of detector by the position of positioning bead and the geometrical relationship of its projection.
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Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104997529A (en) * | 2015-06-30 | 2015-10-28 | 大连理工大学 | Method for correcting cone beam CT system geometric distortion based on symmetrically repetitive template |
| CN105023251A (en) * | 2015-07-07 | 2015-11-04 | 苏州海斯菲德信息科技有限公司 | Geometric correction method for high-resolution cone beam CT system |
| CN105193439A (en) * | 2014-06-23 | 2015-12-30 | 上海理工大学 | Experimental device for CBCT system calibration |
| CN107684435A (en) * | 2017-08-16 | 2018-02-13 | 深圳先进技术研究院 | Cone-beam CT system geometric calibration method and its calibrating installation |
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| CN116421205A (en) * | 2023-03-22 | 2023-07-14 | 北京朗视仪器股份有限公司 | Cone beam CT system correction method |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1692889A (en) * | 2005-01-28 | 2005-11-09 | 大连理工大学 | Scale template used for pyramidal tract x-rays CT system |
| EP1760457A2 (en) * | 2005-07-13 | 2007-03-07 | Carl Zeiss Industrielle Messtechnik GmbH | Method and a system for calibrating a measuring apparatus |
| US20070122020A1 (en) * | 2005-11-29 | 2007-05-31 | General Electric Company | Method and device for geometry analysis and calibration of volumetric imaging systems |
| CN101515370A (en) * | 2009-03-06 | 2009-08-26 | 北京航空航天大学 | Calibration method of projection coordinate of ray source focus in three-dimensional microscopic CT scanning system |
| CN101750430A (en) * | 2009-06-10 | 2010-06-23 | 中国科学院自动化研究所 | Geometry correction method of X-ray computed tomography imaging system |
| CN203776924U (en) * | 2014-03-06 | 2014-08-20 | 北京锐视康科技发展有限公司 | Calibration device for geometric position of cone-beam CT (computed tomography) system |
-
2014
- 2014-03-06 CN CN201410081224.XA patent/CN103784160B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1692889A (en) * | 2005-01-28 | 2005-11-09 | 大连理工大学 | Scale template used for pyramidal tract x-rays CT system |
| EP1760457A2 (en) * | 2005-07-13 | 2007-03-07 | Carl Zeiss Industrielle Messtechnik GmbH | Method and a system for calibrating a measuring apparatus |
| US20070122020A1 (en) * | 2005-11-29 | 2007-05-31 | General Electric Company | Method and device for geometry analysis and calibration of volumetric imaging systems |
| CN101515370A (en) * | 2009-03-06 | 2009-08-26 | 北京航空航天大学 | Calibration method of projection coordinate of ray source focus in three-dimensional microscopic CT scanning system |
| CN101750430A (en) * | 2009-06-10 | 2010-06-23 | 中国科学院自动化研究所 | Geometry correction method of X-ray computed tomography imaging system |
| CN203776924U (en) * | 2014-03-06 | 2014-08-20 | 北京锐视康科技发展有限公司 | Calibration device for geometric position of cone-beam CT (computed tomography) system |
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105193439A (en) * | 2014-06-23 | 2015-12-30 | 上海理工大学 | Experimental device for CBCT system calibration |
| CN104997529B (en) * | 2015-06-30 | 2017-12-26 | 大连理工大学 | Method based on symmetrically repeating template correction cone-beam CT system geometric distortion |
| CN104997529A (en) * | 2015-06-30 | 2015-10-28 | 大连理工大学 | Method for correcting cone beam CT system geometric distortion based on symmetrically repetitive template |
| CN105023251B (en) * | 2015-07-07 | 2018-08-28 | 苏州海斯菲德信息科技有限公司 | A kind of geometric correction method of high-resolution cone-beam CT system |
| CN105023251A (en) * | 2015-07-07 | 2015-11-04 | 苏州海斯菲德信息科技有限公司 | Geometric correction method for high-resolution cone beam CT system |
| CN107684435A (en) * | 2017-08-16 | 2018-02-13 | 深圳先进技术研究院 | Cone-beam CT system geometric calibration method and its calibrating installation |
| CN108030501A (en) * | 2017-11-14 | 2018-05-15 | 深圳先进技术研究院 | A kind of static state cone-beam CT imaging system geometric calibration device and method |
| CN111325678A (en) * | 2018-12-17 | 2020-06-23 | 西门子医疗有限公司 | Artifact correction method for three-dimensional image data |
| CN111325678B (en) * | 2018-12-17 | 2023-11-17 | 西门子医疗有限公司 | Artifact correction method for three-dimensional volume image data |
| CN109924994A (en) * | 2019-04-02 | 2019-06-25 | 晓智科技（成都）有限公司 | A kind of x photo-beat take the photograph during detection position automatic calibrating method and system |
| CN109924994B (en) * | 2019-04-02 | 2023-03-14 | 晓智未来(成都)科技有限公司 | Method and system for automatically calibrating detection position in x-ray shooting process |
| CN113281360A (en) * | 2021-06-30 | 2021-08-20 | 中国电子科技集团公司第三十八研究所 | Sample fixing device of cone beam CT imaging equipment |
| CN113281360B (en) * | 2021-06-30 | 2023-02-28 | 中国电子科技集团公司第三十八研究所 | Sample fixing device of cone beam CT imaging equipment |
| CN114460110A (en) * | 2022-03-08 | 2022-05-10 | 中国电子科技集团公司第三十八研究所 | Servo system error compensation method |
| CN116421205A (en) * | 2023-03-22 | 2023-07-14 | 北京朗视仪器股份有限公司 | Cone beam CT system correction method |
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