CN102853800B - Die body, system and method for measuring oscillation of gantry of CT (computed tomography) device - Google Patents
Die body, system and method for measuring oscillation of gantry of CT (computed tomography) device Download PDFInfo
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Abstract
The invention relates to a die body for measuring oscillation of a gantry of a CT (computed tomography) device. The die body comprises a first part and a second part, wherein the first part is shaped in a cuboid, aluminum tapes are obliquely embedded in the upper area and the lower area of the first part, and no aluminum tape is embedded in the middle area of the first part, and an angle formed between one aluminum tape and a plane formed along the length direction and the width direction of the first part is identical with an angle formed between the other aluminum tape and the plane of the first part in absolute value and is opposite to the same in positive-negative direction. The second part is a cylinder capable of driving the first part to rotate and holding the first part. Besides, the invention further relates to a system and a method for measuring oscillation of the gantry of the CT device. By the aid of the die body, the system and the method, oscillation of the gantry of the CT device can be accurately measured, accurate foundation can be provided to operators to adjust hardware of the CT device and to software algorithm utilized in radiation scanning of the CT device, and accordingly image quality of a reconstructed image is improved.
Description
Technical field
The present invention relates to medical imaging field, die body, system and method that especially a kind of frame for measuring X ray computer tomographic apparatus swings.
Background technology
Carrying out in X ray computer tomoscan (Computed Tomography, CT) process, the frame (gantry) of CT equipment can rotate, to carry out X-ray scanning to object to be checked.Due to High Rotation Speed, can there is undesirable swing in frame, and this swing can reduce the picture quality of rebuilding image in rotary course on the direction of examination couch turnover frame.Along with improving constantly of requiring temporal resolution, require that the rotary speed of frame also improves thereupon, this will increase the centripetal torque of frame significantly, thus causes frame by a larger margin to swing.
If want to obtain high-quality reconstruction image in frame High Rotation Speed situation, just need to carry out necessary hardware adjustment to CT equipment, or the software algorithm that radioscanning uses is adjusted to be controlled the rotation of frame, thus elimination frame swings the adverse effect caused.Accomplishing this point, measure accurately the swing of frame, is must with primary work.But in the prior art, lack and equipment and the method for carrying out accurate quantitative analysis measurement are swung to frame.
Summary of the invention
In view of this, the present invention proposes die body, system and method that a kind of frame for measuring CT equipment swings, swinging in order to the frame measuring CT equipment exactly.
According to an aspect of the present invention, there is provided a kind of for measuring the die body that CT equipment mid frame swings, comprise first component and second component, described first component is cuboid, region and lower area tilt to embed aluminium strip respectively and keep its central region not have aluminium strip to embed at an upper portion thereof, and two embedded aluminium strips become identical, the positive and negative contrary angle of order of magnitude with the length direction by described first component respectively with the plane that width forms; Described second component is the cylinder that described first component can be driven to rotate, and it holds described first component.
Preferably, described die body also comprises the 3rd parts, and described 3rd parts are connected with the inspection part of described second component and described CT equipment respectively, in order to support described second component and to be fixed in described inspection part by described die body.
Preferably, the absolute value of the plane angulation that two aluminium strips embedding described first component form with length direction and the width by described first component is respectively greater than arctan (1/4).
Preferably, on described second component or with described second component in relative rotation equipment on be provided with the anglec of rotation range of the anglec of rotation determining described second component.
Preferably, the described first component of described die body, described second component and/or described 3rd parts are made by PMMA material.
According to another aspect of the present invention, also provide a kind of system using die body to swing to measure CT equipment mid frame, described system comprises: initial angle computing unit, for calculating the initial angle of described CT equipment; Optimum anglec of rotation determining unit, for determining the optimum anglec of rotation of described die body according to the described initial angle calculated; Swing factor calculating unit, for scanning according to the described die body rotated to the described optimum anglec of rotation swing factor that obtained reconstruction image calculates described CT equipment; And amplitude of fluctuation determining unit, for according to the described initial angle calculated, the determined described optimum anglec of rotation and the described swing factor that calculates, determined the amplitude of fluctuation of described CT equipment by inquiry swinging model database.
Preferably, described initial angle computing unit comprises: the first computing unit, for calculate described CT equipment the original die body anglec of rotation be respectively-90 degree ,-45 degree, 0 degree, 45 degree and 90 degree time the swing factor; First redefines unit, for determining the maximum swinging the factor described in the result that described first computing unit calculates, and the original die body anglec of rotation corresponding to this maximum is newly defined as 0 degree, and two angles being adjacent 45 degree are newly defined as-45 degree and 45 degree; Second computing unit, for redefining-45 degree and the angle between 45 degree that unit redefines with 15 degree for interval to described first, calculates the swing factor of described CT equipment; Second redefines unit, for determining the maximum swinging the factor described in the result that described second computing unit calculates, and the original die body anglec of rotation corresponding to this maximum is newly defined as 0 degree, and two angles being adjacent 45 degree are newly defined as-45 degree and 45 degree; 3rd computing unit, for redefining-45 degree and the angle between 45 degree that unit redefines with 5 degree for interval to described second, calculates the swing factor of described CT equipment; And initial angle determining unit, for determining the maximum swinging the factor described in the result that described 3rd computing unit calculates, and the original die body anglec of rotation corresponding to this maximum is defined as the described initial angle of described CT equipment.
Preferably, if the absolute value of the described initial angle of described CT equipment is less than or equal to 45 degree, then described initial angle is defined as the described optimum anglec of rotation of described die body by described optimum anglec of rotation determining unit; If the absolute value of the described initial angle of described CT equipment is greater than 45 degree, then the described optimum anglec of rotation of described die body is defined as 45 degree or-45 degree by described optimum anglec of rotation determining unit, and its sign symbol is consistent with the sign symbol of described initial angle.
Preferably, described swing factor calculating unit comprises scanning element, coordinate swings factor calculating unit and average wobble factor calculating unit, described scanning element is used for given gantry rotation rate, to rotation to being scanned by the described die body of the determined described optimum anglec of rotation of described optimum anglec of rotation determining unit, to obtain the described reconstruction image of described die body; Described coordinate swings factor calculating unit to rebuild the swing factor at given coordinate position place in image described in following formulae discovery:
Wherein, R is coordinate position and the scanning center distance on examination couch vertical lifting direction, FWHM|
σ, Rby the determined half peak value overall with value of R in the described CT equipment with amplitude of fluctuation σ, ε |
rthat abs (x) is the function of trying to achieve x variable absolute value by R determined half peak value overall with value in the desirable CT equipment that there is not frame swing; Described average wobble factor calculating unit to rebuild the average wobble factor in image described in following formulae discovery, and using the described swing factor of the described average wobble factor as described CT equipment:
WF|
σ＝Ave(WF|
σ，R)
Wherein, Ave (x) is the function calculating variable x mean value.
Preferably, described swinging model database is determined by system simulation technology.
According to another aspect of the present invention, also provide a kind of method using die body to swing to measure CT equipment mid frame, described method comprises: initial angle calculation procedure, for calculating the initial angle of described CT equipment; Optimum anglec of rotation determining step, for determining the optimum anglec of rotation of described die body according to the described initial angle calculated; Swing factor calculation step, for scanning according to the described die body rotated to the described optimum anglec of rotation swing factor that obtained reconstruction image calculates described CT equipment; And amplitude of fluctuation determining step, for according to the described initial angle calculated, the determined described optimum anglec of rotation and the described swing factor that calculates, determined the amplitude of fluctuation of described CT equipment by inquiry swinging model database.
Preferably, described initial angle calculation procedure comprises: the first calculation procedure, for calculate described CT equipment the original die body anglec of rotation be respectively-90 degree ,-45 degree, 0 degree, 45 degree and 90 degree time the swing factor; First steps of redefinition, for determining the maximum swinging the factor described in the result that calculates in described first calculation procedure, and the original die body anglec of rotation corresponding to this maximum is newly defined as 0 degree, and two angles being adjacent 45 degree are newly defined as-45 degree and 45 degree; Second calculation procedure, for-45 degree redefined in described first steps of redefinition and angle between 45 degree with 15 degree for interval, calculate the swing factor of described CT equipment; Second steps of redefinition, for determining the maximum swinging the factor described in the result that calculates in described second calculation procedure, and the original die body anglec of rotation corresponding to this maximum is newly defined as 0 degree, and two angles being adjacent 45 degree are newly defined as-45 degree and 45 degree; 3rd calculation procedure, for-45 degree redefined in described second steps of redefinition and angle between 45 degree with 5 degree for interval, calculate the swing factor of described CT equipment; And initial angle determining step, for determining the maximum swinging the factor described in the result that calculates in described 3rd calculation procedure, and the original die body anglec of rotation corresponding to this maximum is defined as the described initial angle of described CT equipment.
Preferably, if the absolute value of the described initial angle of described CT equipment is less than or equal to 45 degree, then described initial angle is defined as the described optimum anglec of rotation of described die body in described optimum anglec of rotation determining step; If the absolute value of the described initial angle of described CT equipment is greater than 45 degree, then the described optimum anglec of rotation of described die body is defined as 45 degree or-45 degree in described optimum anglec of rotation determining step, its sign symbol is consistent with the sign symbol of described initial angle.
Preferably, described swing factor calculation step comprises scanning step, coordinate swings factor calculation step and average wobble factor calculation step, in described scanning step, with given gantry rotation rate, the described die body rotated to the described optimum anglec of rotation determined in described optimum anglec of rotation determining step is scanned, to obtain the described reconstruction image of described die body; Swing in factor calculation step, to rebuild the swing factor at given coordinate position place in image described in following formulae discovery at described coordinate:
Wherein, R is coordinate position and the scanning center distance on examination couch vertical lifting direction, FWHM|
σ, Rby the determined half peak value overall with value of R in the described CT equipment with amplitude of fluctuation σ, ε |
rthat abs (x) is the function of trying to achieve x variable absolute value by R determined half peak value overall with value in the desirable CT equipment that there is not frame swing; In described average wobble factor calculation step, to rebuild the average wobble factor in image described in following formulae discovery, and using the described swing factor of the described average wobble factor as described CT equipment:
WF|
σ＝Ave(WF|
σ，R)
Wherein, Ave (x) is the function calculating variable x mean value.
Preferably, described swinging model database is determined by system simulation technology.
By technique scheme of the present invention, the frame that the present invention can measure CT equipment exactly swings, this carries out with regard to the hardware or CT equipment adjusting CT equipment for operator the software algorithm that radioscanning uses and provides accurate foundation, thus improves the picture quality of rebuilding image.
Accompanying drawing explanation
The preferred embodiments of the present invention will be described in detail by referring to accompanying drawing below, the person of ordinary skill in the art is more clear that above-mentioned and other feature and advantage of the present invention, in accompanying drawing:
Fig. 1 (a) is the front view swinging die body in the specific embodiment of the invention.
Fig. 1 (b) is the left view swinging die body in the specific embodiment of the invention.
Fig. 1 (c) is the top view swinging die body in the specific embodiment of the invention.
Fig. 2 swings the part B of die body and the annexation schematic diagram of part C in the specific embodiment of the invention.
Fig. 3 is the structure chart measuring the system that frame swings in the specific embodiment of the invention.
Fig. 4 is the reconstruction image that in the specific embodiment of the invention, CT equipment scans rear formation to swing die body.
Fig. 5 is to the curve map carrying out half peak value overall with measurement in Fig. 4 image to position fixing in the specific embodiment of the invention.
Fig. 6 is amplitude of fluctuation and the relation curve that swings between factor when to swing the anglec of rotation β of die body be 0 degree.
Fig. 7 swings the relation curve that the anglec of rotation β of die body is-45 amplitudes of fluctuation when spending and swings between the factor.
Fig. 8 is amplitude of fluctuation and the relation curve that swings between factor when to swing the anglec of rotation β of die body be 90 degree.
Fig. 9 is the structure chart of initial angle computing unit in the specific embodiment of the invention.
Figure 10 is the flow chart of steps of the method for carrying out initial angle calculating in the specific embodiment of the invention.
Figure 11 is the structure chart swinging factor calculating unit in the specific embodiment of the invention.
Figure 12 calculates in the specific embodiment of the invention to swing the factor and the method flow diagram determining amplitude of fluctuation.
Figure 13 is the flow chart of steps measuring the method that frame swings in the specific embodiment of the invention.
Detailed description of the invention
For making the object, technical solutions and advantages of the present invention clearly, the present invention is described in more detail by the following examples.
In the present invention, in definition CT equipment, the horizontal direction of examination couch turnover frame is z-axis direction, and the direction of examination couch vertical lifting is y-axis direction, and y-axis direction is vertical with z-axis direction, and with all orthogonal Ze WeixZhou direction, direction in y-axis direction and z-axis direction.Under normal circumstances, frame can rotate with scan image when not tilting in an x-y plane, and the swing of frame is departing from the z-axis direction to x-y plane, numerical value quantitatively on can be understood as the inclined degree that plane of rack and this x-y plane formed.
i: die body designs
In the operation of CT equipment, die body (phantom) is through being commonly used to simulation CT equipment to the scanning process of patient or carry out the simulated measurements such as such as tomography width measure.The present invention designs a kind of novel die body (rear title " swing die body ") for measuring frame swing, its frame to CT equipment is swung very responsive, thus the degree that Measurement accuracy frame swings.
Fig. 1 is for measuring the structural representation of the swing die body that frame swings in the present invention's detailed description of the invention.Wherein, Fig. 1 (a) is the front view of this swing die body; Fig. 1 (b) is the left view of this swing die body; Fig. 1 (c) is the top view of this swing die body.
This swing die body in detailed description of the invention mainly comprises first component and second component, represents respectively in FIG with part A and part B.Described first component is cuboid, region and lower area tilt to embed aluminium strip respectively and keep its central region not have aluminium strip to embed at an upper portion thereof, and two embedded aluminium strips become identical, the positive and negative contrary angle of order of magnitude with the length direction by described first component respectively with the plane that width forms; Described second component is the cylinder that described first component can be driven to rotate, and it holds described first component.In preferred embodiment, described die body also comprises the 3rd parts, represents in FIG with part C.Described 3rd parts are connected with the inspection part of described second component and described CT equipment respectively, in order to support described second component and to be fixed in described inspection part by described die body.Just introduce each parts of this swing die body below respectively.
Part A is the core swinging die body in this detailed description of the invention.This part A is the cuboid plate be made up of PMMA material, and its length is in the z-axis direction much smaller than its length in x-axis and y-axis direction.Two aluminium strips of one fixed width are tilted to embed respectively at the upper area of part A and lower area.Part A length is in the y-axis direction 320mm, length in the direction of the x axis by the aluminium strip that tilts to embed and the angle that formed of x-axis determine, length in the z-axis direction and the desired z-axis scope covered of operator decide, and this is relevant with the design of CT equipment.
0.2mm is by two al zone thickness in upper and lower two regions of embedded part A respectively, size is in the y-axis direction 120mm, they are the upper area of inclination embedded part A cuboid plate and lower area respectively, as shown in figure each in Fig. 1, make part A be in the y-axis direction middle part 80mm within the scope of do not have aluminium strip to embed, shown in the dash area in figure as each in Fig. 1.That is, upper and lower two aluminium strips all have the side-play amount of 40mm relative to part A center in the y-axis direction.
Upper and lower two aluminium strips are respectively to become in the inclination angle embedded part A of same absolute value with x-y plane, and as shown in the oblique line of two in the part A in Fig. 1 (c), its middle and upper part aluminum strip becomes positive-angle with x-y plane, and bottom aluminum strip becomes negative angle with x-y plane.The size at this inclination angle is determined by CT equipment de-sign, but usually can much larger than the arctan (1/4) in the general die body used in the operation of tomography width measure.
Swing the part A embed wholly of die body in part B.
Part B is the oblate cylinder be made up of PMMA material, and its size is determined by the size of part A and CT equipment de-sign.This cylinder side middle panel has rectangular recess, in order to holding portion A, as shown in Fig. 1 (b) He Fig. 1 (c).The major function of part B is holding portion A and drives part A to carry out the rotation of accurate angle (such as using 5 degree as a unit).In order to carry out the rotation of accurate angle, the panel of part B can have the scale that range spends from-90 degree to+90, be spaced apart 5 degree, as shown in Fig. 1 (a).It will be understood by those skilled in the art that the object in order to accurately determine the anglec of rotation, this range also can be arranged on and be formed with part B in relative rotation on miscellaneous equipment.
Fig. 2 swings the part B of die body and the annexation schematic diagram of part C in the specific embodiment of the invention.
Part B is connected with part C by the syndeton shown in Fig. 2.Part C is the oblate cylinder be made up of PMMA material, and its size is greater than the size of part B, and concrete size is determined by the size of part B and CT equipment de-sign.Part C is used for support section B, and by the fixed mechanism on its rear board, as shown in Fig. 1 (b) He Fig. 1 (c), will swing the overall inspection part being fixed on CT equipment of die body, such as, on examination couch.
It will be appreciated by those skilled in the art that, only just need when the swing die body in this detailed description of the invention is used alone to arrange C part in swing die body, and when the swing die body in this detailed description of the invention is integrated in other sweep object, as on die body time, then part B directly can be fixed on other sweep object by modes such as fixed mechanisms, and without the need to arranging C part in this swing die body.
Those skilled in the art are also appreciated that, although A, B, C tri-parts swinging die body are in a specific embodiment made by PMMA material, one of them or multiple part also can have similar, present obvious different CT scan imaging characteristic from aluminium material by other and make.
iI: frame swings measuring system and measuring method
Fig. 3 is the structure chart measuring the system that frame swings in the specific embodiment of the invention.
This system uses and swings the amplitude of fluctuation that die body measures CT equipment mid frame.As shown in Figure 3, this system comprises: initial angle computing unit 10, for calculating the initial angle of CT equipment; Optimum anglec of rotation determining unit 20, for determining the optimum anglec of rotation of described swing die body according to the described initial angle calculated; Swing factor calculating unit 30, for scanning according to the described swing die body rotated to the described optimum anglec of rotation swing factor that obtained reconstruction image calculates CT equipment; And amplitude of fluctuation determining unit 40, for according to the described initial angle calculated, the determined described optimum anglec of rotation and the described swing factor that calculates, determined the amplitude of fluctuation of described CT equipment by inquiry swinging model database.
In the research that frame is swung, the swing characteristic of frame can be embodied with swing curve.This swing curve is the curve of frame in a rotation period (being 2 π angles of a circumference) mid frame angle change.Amplitude peak at a rotation period mid frame angle of inclination can be defined as amplitude of fluctuation σ by us, and we are also by determining this amplitude of fluctuation σ to realize the quantitative measurment swung frame in the present invention.
In the scanning process of CT equipment, X-ray bulb present position is an important parameter, usual projected angle (projection angle), namely between X-ray bulb point and scanning center (Iso center), line and x-axis positive direction angulation characterize.Initial angle ω 0 in the present invention to be defined as in CT equipment swing curve relative to the delay angle of projected angle.For a given CT equipment, due to the otherness of its system hardware configuration, determine, the initial angle ω 0 that each CT equipment is unique and fixing.According to the research of inventor, initial angle ω 0 has remarkable impact for swing die body to the susceptibility that frame swings, because of but important parameter in measuring machine frame swing process.
Therefore in the present invention, by calculating initial angle ω 0, and and then can determine that amplitude of fluctuation σ carrys out the swing degree of quantitative measurment frame.In a specific embodiment, we will calculate the initial angle ω 0 of CT equipment, and obtain the value of amplitude of fluctuation σ with this initial angle ω 0, thus realize the quantitative measurment to frame swing.
(1) mode swinging the factor is calculated
Fig. 4 is the reconstruction image that in the specific embodiment of the invention, CT equipment scans rear formation to swing die body.Fig. 5 rebuilds image to Fig. 4 in the specific embodiment of the invention to carry out the curve map that half peak value overall with (Full Width at HalfMaximum, FWHM) measures to position fixing.Wherein, FWHM refers to that ordinate is peak value one half in two-dimensional curve figure, corresponding to the width value on abscissa.In Figure 5, abscissa is that in reconstruction image, certain is to the pixel value on position fixing straight line, and ordinate is standard CT value, therefore passes through the reconstruction image graph 4 of the swing die body obtained, just can in the hope of the FWHM value of coordinate position each in image.
In order to easy analysis, define one in the present invention and swing relevant variable with frame---swing the factor (WobblingFactor, WF).As follows in the computing formula (1) of the swing factor WF rebuilding certain given coordinate position in image:
Wherein, FWHM|
σ, Rit is the FWHM value determined by R value in CT equipment to be measured (the CT equipment of corresponding amplitude of fluctuation σ); ε |
rit is the FWHM value determined by R value in idealized system (the CT equipment of amplitude of fluctuation σ=0); Abs (x) is the function of trying to achieve x variable absolute value.Wherein, R is the given coordinate position shown in Fig. 4 and Iso center distance in the y-axis direction.Note, when in swing die body rotation process, angle shown in image rotation to Fig. 4 will be rebuild, namely make demonstrating the size two line regions up and down of embedded in aluminium strip angle in vertical position being measured R value.
For given CT equipment to be measured, can scan the swing die body in the specific embodiment of the invention with this CT equipment, by emulating the reconstruction image after scanning, the above-mentioned formula position that R value is different on die body is then utilized to record the value swinging factor WF respectively.
In a specific embodiment of the present invention, take 10mm as interval, R=-150mm ,-140mm ... ,-60mm ,-50mm, 50mm, 60mm ..., 140mm, 150mm position measure respectively and swing the value of factor WF.From above to the introducing of structure swinging die body, above-mentioned position is all correspond to position part A having aluminium strip and embed.Afterwards, utilize the above-mentioned multiple swing factor WF values calculated, the average wobble factor (Average Wobbling Factor) is calculated by formula (2) below, and using the value of this average wobble factor as the swing factor WF of this CT equipment:
WF|
σ＝Ave(WF|
σ，R)………(2)
Wherein Ave (x) is the function calculating variable x mean value.
(2) relationship analysis of amplitude of fluctuation σ and initial angle ω 0
Pass through system simulation technology, those skilled in the art can by carrying out scanning emulation respectively to the swing die body being in different rotary angle β, thus obtaining various CT equipment swinging model database under circumstances, this anglec of rotation β can be determined by the anglec of rotation range on the part B of above introduced swing die body.In this swinging model database, the quantitative relation amplitude of fluctuation σ of CT equipment, initial angle ω 0 can be set up, swinging factor WF and swing between die body anglec of rotation β.
According to this swinging model database that system emulation obtains, Fig. 6, Fig. 7, Fig. 8 schematically illustrate respectively swing the anglec of rotation β of die body be respectively 0 degree ,-45 degree and 90 degree time, amplitude of fluctuation σ and the relation curve swung between factor WF, initial angle ω 0.
Show according to research, when initial angle ω 0 fixes (for the CT equipment that certain is given), swing factor WF dull increase along with the increase of amplitude of fluctuation σ.Meanwhile, the relation swung between factor WF and amplitude of fluctuation σ is subject to the remarkable impact of initial angle ω 0, swings factor WF larger as the anglec of rotation β of initial angle ω 0 close to swing die body, as Fig. 6-8 each figure shown in.
As can be seen from Fig. 6-8, we, be 90 degree when swinging the difference of die body anglec of rotation β and initial angle ω 0, and when namely β-ω 0=90 spends, the value of swing factor WF is minimum; And when swinging die body anglec of rotation β and being equal with initial angle ω 0, when namely β-ω 0=0 spends, the value swinging factor WF is maximum.Utilize above-mentioned character, we can calculate the swing factor WF when difference swings die body anglec of rotation β, and these swing die body anglec of rotation β corresponding to maximum swinging factor WF are the initial angle ω 0 of CT equipment.Further, by the swing die body anglec of rotation β determined, the swing factor WF calculated and the initial angle ω 0 obtained, just can inquire about existing swinging model database to determine the value of amplitude of fluctuation σ, thus obtain the frame amplitude of fluctuation of CT equipment.When the data do not met completely in swinging model database, those skilled in the art can also utilize the data with existing in database, adopt interpolation computing method well known in the art to determine the value of amplitude of fluctuation σ.
(3) initial angle ω 0 is calculated
Fig. 9 is the structure chart of initial angle computing unit in the specific embodiment of the invention.
In the specific embodiment of the invention, described initial angle computing unit 10 comprises: the first computing unit 101, for calculate CT equipment the original swing die body anglec of rotation be respectively-90 degree ,-45 degree, 0 degree, 45 degree and 90 degree time the swing factor; First redefines unit 102, for determining the maximum swinging the factor described in the result that described first computing unit 101 calculates, and the original swing die body anglec of rotation corresponding to this maximum is newly defined as 0 degree, and two angles being adjacent 45 degree are newly defined as-45 degree and 45 degree; Second computing unit 103, for redefining-45 degree and the angle between 45 degree that unit 102 redefines with 15 degree for interval to described first, the swing factor of calculating CT equipment; Second redefines unit 104, for determining the maximum swinging the factor described in the result that described second computing unit 103 calculates, and the original swing die body anglec of rotation corresponding to this maximum is newly defined as 0 degree, and two angles being adjacent 45 degree are newly defined as-45 degree and 45 degree; 3rd computing unit 105, for redefining-45 degree and the angle between 45 degree that unit 104 redefines with 5 degree for interval to described second, the swing factor of calculating CT equipment; And initial angle determining unit 106, for determining the maximum swinging the factor described in the result that described 3rd computing unit 105 calculates, and the original swing die body anglec of rotation corresponding to this maximum is defined as the described initial angle of CT equipment.
Figure 10 is the flow chart of steps of the method for carrying out initial angle calculating in the specific embodiment of the invention.
As shown in Figure 10, in the specific embodiment of the invention, described initial angle computing unit 10 in the following manner flow process calculates the value of the initial angle ω 0 of CT equipment.
In step s 11, the first computing unit 101 utilizes formula (1) and formula (2) to calculate respectively to swing that die body anglec of rotation β is-90 degree ,-45 degree, 0 degree, 45 degree and 90 degree time, the value of the swing factor WF of CT equipment.
In step s 12, first redefines the maximum that unit 102 finds out CT equipment swing factor WF in above-mentioned result of calculation, swing die body anglec of rotation β corresponding to this maximum is newly defined as 0 degree, and two angles being adjacent 45 degree is newly defined as-45 degree and 45 degree.
In step s 13, second computing unit 103 to-45 degree after redefining and the angle between 45 degree with 15 degree for interval, utilize formula (1) and formula (2) again to calculate CT equipment and swing the value of factor WF, namely calculate and swing the value of CT equipment swing factor WF that die body anglec of rotation β is positioned at after redefining-45 degree ,-30 degree ,-15 degree, 0 degree, 15 degree, 30 degree, 45 degree place.
In step S14, second redefines the operation of unit 104 according to the result of calculation repeated execution of steps S12 of step S13, redefines out-45 degree and 45 degree.That is, determine the maximum swinging the factor in the result that the second computing unit 103 calculates, and the swing die body anglec of rotation corresponding to this maximum is newly defined as 0 degree, and two angles being adjacent 45 degree are newly defined as-45 degree and 45 degree.
In step S15,3rd computing unit 105 to-45 degree after redefining and the angle between 45 degree with 5 degree for interval, utilize formula (1) and formula (2) again to calculate CT equipment and swing the value of factor WF, namely calculate swing die body anglec of rotation β be positioned at after redefining-45 degree ,-40 degree ...-5 degree, 0 degree, 5 degree ..., 40 degree, the CT equipment at 45 degree of places swings the value of factor WF.
In step s 16, initial angle determining unit 106 finds CT equipment to swing the maximum of factor WF from step S15 result of calculation, and the original swing die body anglec of rotation β corresponding to this maximum is initial angle ω 0.
Below, we are with the implementation of an example in explanation said method step.
In certain CT equipment, utilize formula (1) and formula (2) first in step s 11, calculate respectively swing die body anglec of rotation β be-90 degree ,-45 degree, 0 degree, 45 degree and 90 degree time CT equipment swing factor WF value.In step s 12, find that in above-mentioned result of calculation, CT equipment swing factor WF is maximum when swing die body anglec of rotation β is 45 degree, the position being now 45 degree by swing die body anglec of rotation β is newly defined as 0 degree, and two angles being adjacent 45 degree are newly defined as-45 degree and 45 degree, be newly defined as-45 by original swing die body anglec of rotation β two positions that are 0 degree and 90 degree and spend and 45 degree.In step s 13, calculating swing die body anglec of rotation β is positioned at after redefining-45 degree ,-30 degree ,-15 are spent, the value of the CT equipment swing factor WF at 0 degree, 15 degree, 30 degree, 45 degree place, namely calculates the value that original swing die body anglec of rotation β is the CT equipment swing factor WF of 0 degree, 15 degree, 30 degree, 45 degree, 60 degree, 75 degree, 90 degree.In step S14, the CT equipment in above-mentioned result of calculation of finding swings-15 maximum when spending after to swing die body anglec of rotation β be redefine of factor WF, namely maximum when original swing die body anglec of rotation β is 30 degree, the position being now 30 degree by original swing die body anglec of rotation β is newly defined as 0 degree, and two angles being adjacent 45 degree are newly defined as-45 degree and 45 degree, be-15 to spend and to reorientate be 45 degree and 45 degree two positions of 75 degree by original swing die body anglec of rotation β.In step S15, calculate swing die body anglec of rotation β be positioned at after redefining-45 degree ,-40 degree ... 5 degree, 0 degree, 5 degree ..., 40 degree, the CT equipment at 45 degree of places swings the value of factor WF, the dynamic model body anglec of rotation β namely calculating original pendulum is-15 degree ,-10 degree ... 25 degree, 30 degree, 35 degree ... the CT equipment of 70 degree, 75 degree swings the value of factor WF.In step s 16, the CT equipment in above-mentioned result of calculation of finding swings-10 maximum when spending after to swing die body anglec of rotation β be redefine of factor WF, namely maximum when original swing die body anglec of rotation β is 20 degree, now 20 degree are the initial angle ω 0 of CT equipment.
(4) optimum anglec of rotation β opt is determined
The optimum anglec of rotation β opt swinging die body is determined above below with determined initial angle ω 0.
If the absolute value of the initial angle ω 0 of the CT equipment calculated hereinbefore is less than or equal to 45 degree, then this initial angle ω 0 is defined as optimum anglec of rotation β opt by optimum anglec of rotation determining unit 20; If the absolute value of the initial angle ω 0 of CT equipment is greater than 45 degree, then optimum anglec of rotation β opt is defined as 45 degree or-45 degree by optimum anglec of rotation determining unit 20, and its sign symbol is consistent with the symbol of initial angle ω 0.
Such as, when the CT equipment initial angle ω 0 calculated is 35 degree, then the optimum anglec of rotation β opt swinging die body is 35 degree; And if the CT equipment initial angle ω 0 calculated for-60 spend time, then the optimum anglec of rotation β opt swinging die body is-45 degree.
(5) calculating swings factor WF and determines the amplitude of fluctuation σ of CT equipment
Before the amplitude of fluctuation σ determining CT equipment, first we for given CT equipment, will calculate the swing factor WF of CT equipment.
Figure 11 is the structure chart swinging factor calculating unit in the specific embodiment of the invention.
As shown in figure 11, described swing factor calculating unit 30 in the specific embodiment of the invention comprises scanning element 301, coordinate swings factor calculating unit 302 and average wobble factor calculating unit 303, described scanning element 301 is for given gantry rotation rate, to rotation to being scanned by the described swing die body of the determined described optimum anglec of rotation of described optimum anglec of rotation determining unit 20, to obtain the described reconstruction image of described swing die body; It is the swing factor at R place that described coordinate swing factor calculating unit 302 calculates in described reconstruction image coordinate position with introduced formula (1) above; Described average wobble factor calculating unit 303 with as above the formula (2) introduced calculate as described in the average wobble factor in reconstruction image, and using the described swing factor of the described average wobble factor as CT equipment.
Below, we illustrate in the specific embodiment of the invention swing factor WF the method determining the amplitude of fluctuation σ of CT equipment rack that calculate CT equipment.
Figure 12 shows in the specific embodiment of the invention to calculate and swings the factor and the method flow diagram determining amplitude of fluctuation σ.
In step S41, the position of die body rotation to the optimum anglec of rotation β opt determined will be swung above.
In step S42, a rotary speed of given CT equipment rack, scanning element 301 scans swing die body with this given gantry rotation rate.
In step S43, coordinate swings factor calculating unit 302 and scans obtained reconstruction image according to swing die body, and utilize formula (1) to calculate rebuilding coordinate position in image is the swing factor at R place; Average wobble factor calculating unit 303 utilizes formula (2), rebuilds the average wobble factor of image under calculating current gantry rotation rate, and using the value of this average wobble factor as the swing factor WF of CT equipment.
In step S44, according to the swing factor WF of the CT equipment calculated in optimum anglec of rotation β opt, the step S43 of determined swing die body and the CT equipment initial angle ω 0 that obtained, amplitude of fluctuation determining unit 40 determines the value of the amplitude of fluctuation σ of CT equipment under current gantry rotation rate by inquiring about existing swinging model database, thus obtains the frame amplitude of fluctuation of CT equipment.When the data do not met completely in swinging model database, those skilled in the art can utilize the data with existing in database, adopt interpolation computing method well known in the art to determine the value of amplitude of fluctuation σ.
In step S45, judge whether to measure in all gantry rotation rate situations.If do not measured under all rotation speed behavior, then turn back to step S42, another rotary speed of given CT equipment rack determines amplitude of fluctuation σ again; If measured under all rotation speed behavior, then ending method flow process.
Like this, by repeatedly performing the operation of step S42 to step S44, the amplitude of fluctuation σ of CT equipment under different gantry rotation rate can be calculated.
Content comprehensively presented hereinbefore, the specific embodiment of the invention additionally provides a kind of method utilizing die body to swing to measure frame.Figure 13 is the flow chart of steps measuring the method that frame swings in the specific embodiment of the invention.
As shown in figure 13, in the specific embodiment of the invention, described method comprises: initial angle calculation procedure S1, for calculating the initial angle of CT equipment; Optimum anglec of rotation determining step S2, for carrying out the optimum anglec of rotation of true described swing die body according to the described initial angle calculated; Swing factor calculation step S3, for scanning according to the described swing die body rotated to the described optimum anglec of rotation swing factor that obtained reconstruction image calculates CT equipment; And amplitude of fluctuation determining step S4, for according to the described initial angle calculated, the determined described optimum anglec of rotation and the described swing factor that calculates, determined the amplitude of fluctuation of described CT equipment by inquiry swinging model database.
By technique scheme, the frame that the present invention can measure CT equipment exactly swings, and this just adjusts CT equipment for operator or the algorithm that uses provides accurate foundation, thus improves the picture quality of reconstruction image.
The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (15)
1., for measuring the die body that CT equipment mid frame swings, comprise first component (A) and second component (B),
Described first component (A) is cuboid, region and lower area tilt to embed aluminium strip respectively and keep its central region not have aluminium strip to embed at an upper portion thereof, and two embedded aluminium strips become identical, the positive and negative contrary angle of order of magnitude with the length direction by described first component (A) respectively with the plane that width forms;
Described second component (B) is the cylinder that described first component (A) can be driven to rotate, and it holds described first component (A).
2. die body according to claim 1, is characterized in that, described die body also comprises the 3rd parts (C),
Described 3rd parts (C) are connected with the inspection part of described second component (B) and described CT equipment respectively, in order to support described second component (B) and to be fixed in described inspection part by described die body.
3. die body according to claim 1, it is characterized in that, the absolute value of the plane angulation that two aluminium strips embedding described first component (A) form with length direction and the width by described first component (A) is respectively greater than arctan (1/4).
4. die body according to claim 1, it is characterized in that, at described second component (B) upper or with described second component (B) in relative rotation equipment on be provided with the anglec of rotation range of the anglec of rotation determining described second component (B).
5. according to the die body in claim 1-4 described in any one, it is characterized in that, make the described first component (A) of described die body, described second component (B) and/or described 3rd parts (C) by PMMA material.
6. use the system that die body swings to measure CT equipment mid frame, described system comprises:
Initial angle computing unit (10), for calculating the initial angle of described CT equipment;
Optimum anglec of rotation determining unit (20), for determining the optimum anglec of rotation of described die body according to the described initial angle calculated;
Swing factor calculating unit (30), for scanning according to the described die body rotated to the described optimum anglec of rotation swing factor that obtained reconstruction image calculates described CT equipment; And
Amplitude of fluctuation determining unit (40), for according to the described initial angle calculated, the determined described optimum anglec of rotation and the described swing factor that calculates, determines the amplitude of fluctuation of described CT equipment by inquiry swinging model database.
7. system according to claim 6, is characterized in that, described initial angle computing unit (10) comprising:
First computing unit (101), for calculate described CT equipment the original die body anglec of rotation be respectively-90 degree ,-45 degree, 0 degree, 45 degree and 90 degree time the swing factor;
First redefines unit (102), for determining the maximum swinging the factor described in the result that described first computing unit (101) calculates, and the original die body anglec of rotation corresponding to this maximum is newly defined as 0 degree, and two angles being adjacent 45 degree are newly defined as-45 degree and 45 degree;
Second computing unit (103), for redefining-45 degree and the angle between 45 degree that unit (102) redefines with 15 degree for interval to described first, calculates the swing factor of described CT equipment;
Second redefines unit (104), for determining the maximum swinging the factor described in the result that described second computing unit (103) calculates, and the original die body anglec of rotation corresponding to this maximum is newly defined as 0 degree, and two angles being adjacent 45 degree are newly defined as-45 degree and 45 degree;
3rd computing unit (105), for redefining-45 degree and the angle between 45 degree that unit (104) redefines with 5 degree for interval to described second, calculates the swing factor of described CT equipment; And
Initial angle determining unit (106), for determining the maximum swinging the factor described in the result that described 3rd computing unit (105) calculates, and the original die body anglec of rotation corresponding to this maximum is defined as the described initial angle of described CT equipment.
8. system according to claim 6, it is characterized in that, if the absolute value of the described initial angle of described CT equipment is less than or equal to 45 degree, then described initial angle is defined as the described optimum anglec of rotation of described die body by described optimum anglec of rotation determining unit (20); If the absolute value of the described initial angle of described CT equipment is greater than 45 degree, then the described optimum anglec of rotation of described die body is defined as 45 degree or-45 degree by described optimum anglec of rotation determining unit (20), and its sign symbol is consistent with the sign symbol of described initial angle.
9. system according to claim 6, it is characterized in that, described swing factor calculating unit (30) comprises scanning element (301), coordinate swings factor calculating unit (302) and average wobble factor calculating unit (303)
Described scanning element (301) is for given gantry rotation rate, to rotation to being scanned by the described die body of the determined described optimum anglec of rotation of described optimum anglec of rotation determining unit (20), to obtain the described reconstruction image of described die body;
Described coordinate swings factor calculating unit (302) to rebuild the swing factor at given coordinate position place in image described in following formulae discovery:
Wherein, R is coordinate position and the scanning center distance on examination couch vertical lifting direction, FWHM|
σ, Rby the determined half peak value overall with value of R in the described CT equipment with amplitude of fluctuation σ, ε |
rthat abs (x) is the function of trying to achieve x variable absolute value by R determined half peak value overall with value in the desirable CT equipment that there is not frame swing;
Described average wobble factor calculating unit (303) to rebuild the average wobble factor in image described in following formulae discovery, and using the described swing factor of the described average wobble factor as described CT equipment:
WF|
σ＝Ave(WF|
σ，R)
Wherein, Ave (x) is the function calculating variable x mean value.
10. according to the system in claim 6-9 described in any one, it is characterized in that, determine described swinging model database by system simulation technology.
11. 1 kinds of methods using die body to swing to measure CT equipment mid frame, described method comprises:
Initial angle calculation procedure, for calculating the initial angle of described CT equipment;
Optimum anglec of rotation determining step, for determining the optimum anglec of rotation of described die body according to the described initial angle calculated;
Swing factor calculation step, for scanning according to the described die body rotated to the described optimum anglec of rotation swing factor that obtained reconstruction image calculates described CT equipment; And
Amplitude of fluctuation determining step, for according to the described initial angle calculated, the determined described optimum anglec of rotation and the described swing factor that calculates, determines the amplitude of fluctuation of described CT equipment by inquiry swinging model database.
12. methods according to claim 11, is characterized in that, described initial angle calculation procedure comprises:
First calculation procedure, for calculate described CT equipment the original die body anglec of rotation be respectively-90 degree ,-45 degree, 0 degree, 45 degree and 90 degree time the swing factor;
First steps of redefinition, for determining the maximum swinging the factor described in the result that calculates in described first calculation procedure, and the original die body anglec of rotation corresponding to this maximum is newly defined as 0 degree, and two angles being adjacent 45 degree are newly defined as-45 degree and 45 degree;
Second calculation procedure, for-45 degree redefined in described first steps of redefinition and angle between 45 degree with 15 degree for interval, calculate the swing factor of described CT equipment;
Second steps of redefinition, for determining the maximum swinging the factor described in the result that calculates in described second calculation procedure, and the original die body anglec of rotation corresponding to this maximum is newly defined as 0 degree, and two angles being adjacent 45 degree are newly defined as-45 degree and 45 degree;
3rd calculation procedure, for-45 degree redefined in described second steps of redefinition and angle between 45 degree with 5 degree for interval, calculate the swing factor of described CT equipment; And
Initial angle determining step, for determining the maximum swinging the factor described in the result that calculates in described 3rd calculation procedure, and is defined as the described initial angle of described CT equipment by the original die body anglec of rotation corresponding to this maximum.
13. methods according to claim 11, it is characterized in that, if the absolute value of the described initial angle of described CT equipment is less than or equal to 45 degree, then described initial angle is defined as the described optimum anglec of rotation of described die body in described optimum anglec of rotation determining step; If the absolute value of the described initial angle of described CT equipment is greater than 45 degree, then the described optimum anglec of rotation of described die body is defined as 45 degree or-45 degree in described optimum anglec of rotation determining step, its sign symbol is consistent with the sign symbol of described initial angle.
14. methods according to claim 11, is characterized in that, described swing factor calculation step comprises scanning step, coordinate swings factor calculation step and average wobble factor calculation step,
In described scanning step, with given gantry rotation rate, the described die body rotated to the described optimum anglec of rotation determined in described optimum anglec of rotation determining step is scanned, to obtain the described reconstruction image of described die body;
Swing in factor calculation step, to rebuild the swing factor at given coordinate position place in image described in following formulae discovery at described coordinate:
Wherein, R is coordinate position and the scanning center distance on examination couch vertical lifting direction, FWHM|
σ, Rby the determined half peak value overall with value of R in the described CT equipment with amplitude of fluctuation σ, ε |
rthat abs (x) is the function of trying to achieve x variable absolute value by R determined half peak value overall with value in the desirable CT equipment that there is not frame swing;
In described average wobble factor calculation step, to rebuild the average wobble factor in image described in following formulae discovery, and using the described swing factor of the described average wobble factor as described CT equipment:
WF|
σ＝Ave(WF|
σ，R)
Wherein, Ave (x) is the function calculating variable x mean value.
15., according to the method in claim 11-14 described in any one, is characterized in that, determine described swinging model database by system simulation technology.
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| CN2298775Y (en) * | 1997-06-12 | 1998-12-02 | 北京市卫生防疫站 | Imaging performance detecting model of CT machine |
| CN1657009A (en) * | 2005-03-22 | 2005-08-24 | 东软飞利浦医疗设备系统有限责任公司 | CT apparatus geometric parametar corrction method |
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| CN2298775Y (en) * | 1997-06-12 | 1998-12-02 | 北京市卫生防疫站 | Imaging performance detecting model of CT machine |
| CN1657009A (en) * | 2005-03-22 | 2005-08-24 | 东软飞利浦医疗设备系统有限责任公司 | CT apparatus geometric parametar corrction method |
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