CN102853800A - 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 the medical imaging field, die body, system and method that especially a kind of frame for measuring the X ray computer tomographic apparatus swings.
Background technology
In carrying out X ray computer tomoscan (Computed Tomography, CT) process, the frame of CT equipment (gantry) can be rotated, so that object to be checked is carried out X-ray scanning.Because undesirable swing can occur in the direction of examination couch turnover frame in High Rotation Speed, frame in rotary course, and this swing can reduce the picture quality of reconstructed image.Along with improving constantly that temporal resolution is required, require the rotational speed of frame also to improve thereupon, this will increase the centripetal torque of frame significantly, thereby causes frame by a larger margin to swing.
In frame High Rotation Speed situation, obtain high-quality reconstructed image if want, just need to carry out necessary hardware adjustment to CT equipment, perhaps the employed software algorithm of radioscanning is adjusted with the rotation to frame and controlled, swing the adverse effect that causes thereby eliminate frame.Accomplish this point, it then is necessary and primary work that the swing of frame is measured accurately.Yet in the prior art, lack equipment and the method that the accurate quantitative analysis measurement is carried out in swing 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, swing in order to the frame of measuring exactly CT equipment.
According to an aspect of the present invention, a kind of die body for measuring the swing of CT equipment mid frame is provided, comprise first component and second component, described first component is rectangular parallelepiped, zone and lower area tilt to embed respectively aluminium strip and keep its central region not have aluminium strip embedding at an upper portion thereof, and two embedded aluminium strips become identical, the positive and negative opposite angle of order of magnitude with length direction by described first component with the plane that Width forms respectively; Described second component is the right cylinder that can drive described first component rotation, and it holds described first component.
Preferably, described die body also comprises the 3rd parts, described the 3rd parts respectively with described second component be connected the inspection of CT equipment and partly be connected, in order to support described second component and described die body be fixed on the described inspection part.
The absolute value of the plane angulation that two aluminium strips that preferably, embed described first component form with length direction and Width by described first component respectively is greater than arctan (1/4).
Preferably, on described second component or with described second component in relative rotation equipment be provided with anglec of rotation range in order to the anglec of rotation of determining described second component.
Preferably, make the described first component of described die body, described second component and/or described the 3rd parts by the PMMA material.
According to another aspect of the present invention, also provide a kind of and measure the system that CT equipment mid frame swings with die body, described system comprises: the initial angle computing unit, for the initial angle of calculating described CT equipment; Optimum rotation angle determining unit is for the optimum rotation angle of determining described die body according to the described initial angle that calculates; Swing factor calculating unit, be used for according to the described die body of described optimum rotation angle scans the swing factor that resulting reconstructed image calculates described CT equipment to rotating extremely; And the amplitude of fluctuation determining unit, be used for according to the described initial angle, the determined described optimum rotation angle that calculate and the described swing factor that calculates, determine the amplitude of fluctuation of described CT equipment by inquiry swinging model database.
Preferably, described initial angle computing unit comprises: the first computing unit is used for calculating described CT equipment and is respectively-90 degree ,-45 degree, 0 degree, swing factor when 45 degree and 90 are spent in original die body rotation angle; First redefines the unit, be used for to determine to swing described in the result that described the first computing unit calculates the maximal value of the factor, and the corresponding original die body rotation angle of this maximal value is redefined is 0 degree, and two angles that will be adjacent 45 degree redefine and are that-45 degree and 45 spend; The second computing unit is used for redefining-45 degree that the unit redefines and the angle between 45 degree take 15 degree as the interval to described first, calculates the swing factor of described CT equipment; Second redefines the unit, be used for to determine to swing described in the result that described the second computing unit calculates the maximal value of the factor, and the corresponding original die body rotation angle of this maximal value is redefined is 0 degree, and two angles that will be adjacent 45 degree redefine and are that-45 degree and 45 spend; The 3rd computing unit is used for redefining-45 degree that the unit redefines and the angle between 45 degree take 5 degree as the interval to described second, calculates the swing factor of described CT equipment; And the initial angle determining unit, be used for to determine to swing the maximal value of the factor described in the result that described the 3rd computing unit calculates, and the corresponding original die body rotation angle of this maximal value 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 optimum rotation angle determining unit is defined as described initial angle the described optimum rotation angle of described die body; If the absolute value of the described initial angle of described CT equipment is greater than 45 degree, then described optimum rotation angle determining unit is defined as 45 degree or-45 degree with the described optimum rotation angle of described die body, and its sign symbol is consistent with the sign symbol of described initial angle.
Preferably, described swing factor calculating unit comprises that scanning element, coordinate swing factor calculating unit and on average swing factor calculating unit, described scanning element is used for given frame rotational speed, rotation to the described die body by the determined described optimum rotation angle of described optimum rotation angle determining unit is scanned, to obtain the described reconstructed image of described die body; Described coordinate swings factor calculating unit is calculated given coordinate position place in the described reconstructed image with following formula the swing factor:
Wherein, R is coordinate position and the scanning center distance on examination couch vertical lifting direction, FWHM|
σ, RBe in having the described CT equipment of amplitude of fluctuation σ by the determined half peak value overall with value of R, ε |
RBe in the desirable CT equipment that does not exist frame to swing by the determined half peak value overall with value of R, abs (x) is the function of trying to achieve x variable absolute value; Described average swing factor calculating unit is calculated the average swing factor in the described reconstructed image with following formula, and with the described swing factor of the described average swing factor as described CT equipment:
WF|
σ＝Ave(WF|
σ，R)
Wherein, Ave (x) is the function that calculates variable x mean value.
Preferably, determine described swinging model database by system simulation technology.
According to another aspect of the present invention, also provide a kind of and measure the method that CT equipment mid frame swings with die body, described method comprises: the initial angle calculation procedure, for the initial angle of calculating described CT equipment; Optimum rotation angle determining step is for the optimum rotation angle of determining described die body according to the described initial angle that calculates; Swing factor calculation procedure, be used for according to the described die body of described optimum rotation angle scans the swing factor that resulting reconstructed image calculates described CT equipment to rotating extremely; And the amplitude of fluctuation determining step, be used for according to the described initial angle, the determined described optimum rotation angle that calculate and the described swing factor that calculates, determine the amplitude of fluctuation of described CT equipment by inquiry swinging model database.
Preferably, described initial angle calculation procedure comprises: the first calculation procedure is used for calculating described CT equipment and is respectively-90 degree ,-45 degree, 0 degree, swing factor when 45 degree and 90 are spent in original die body rotation angle; The first steps of redefinition, be used for swinging described in the result who determines to calculate in described the first calculation procedure the maximal value of the factor, and the corresponding original die body rotation angle of this maximal value is redefined is 0 degree, and two angles that will be adjacent 45 degree redefine and are that-45 degree and 45 spend; The second calculation procedure take 15 degree as the interval, is calculated the swing factor of described CT equipment for the angle between-45 degree and 45 that redefine at described the first steps of redefinition are spent; The second steps of redefinition, be used for swinging described in the result who determines to calculate in described the second calculation procedure the maximal value of the factor, and the corresponding original die body rotation angle of this maximal value is redefined is 0 degree, and two angles that will be adjacent 45 degree redefine and are that-45 degree and 45 spend; The 3rd calculation procedure take 5 degree as the interval, is calculated the swing factor of described CT equipment for the angle between-45 degree and 45 that redefine at described the second steps of redefinition are spent; And the initial angle determining step, be used for swinging described in the result who determines to calculate in described the 3rd calculation procedure the maximal value of the factor, and the corresponding original die body rotation angle of this maximal value be 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 in described optimum rotation angle determining step, described initial angle is defined as the described optimum rotation angle of described die body; If the absolute value of the described initial angle of described CT equipment greater than 45 degree, then is defined as 45 degree or-45 degree with the described optimum rotation angle of described die body in described optimum rotation angle determining step, its sign symbol is consistent with the sign symbol of described initial angle.
Preferably, described swing factor calculation procedure comprises that scanning step, coordinate swing factor calculation procedure and on average swing factor calculation procedure, in described scanning step, with given frame rotational speed, the described die body of rotation to the described optimum rotation angle of determining in described optimum rotation angle determining step scanned, to obtain the described reconstructed image of described die body; Swing in the factor calculation procedure at described coordinate, calculate the swing factor at given coordinate position place in the described reconstructed image with following formula:
Wherein, R is coordinate position and the scanning center distance on examination couch vertical lifting direction, FWHM|
σ, RBe in having the described CT equipment of amplitude of fluctuation σ by the determined half peak value overall with value of R, ε |
RBe in the desirable CT equipment that does not exist frame to swing by the determined half peak value overall with value of R, abs (x) is the function of trying to achieve x variable absolute value; In described average swing factor calculation procedure, calculate the average swing factor in the described reconstructed image with following formula, and with the described swing factor of the described average swing factor as described CT equipment:
WF|
σ＝Ave(WF|
σ，R)
Wherein, Ave (x) is the function that calculates variable x mean value.
Preferably, determine described swinging model database by system simulation technology.
By technique scheme of the present invention, the frame that the present invention can measure CT equipment exactly swings, this just carries out the employed software algorithm of radioscanning accurate foundation is provided for the operator adjusts the hardware of CT equipment or CT equipment, thereby has improved the picture quality of reconstructed image.
Description of drawings
The below will make clearer above-mentioned and other feature and advantage of the present invention of those of ordinary skill in the art by describing the preferred embodiments of the present invention in detail with reference to accompanying drawing, in the accompanying drawing:
Fig. 1 (a) is the front elevation that swings die body in the specific embodiment of the invention.
Fig. 1 (b) is the left view that swings die body in the specific embodiment of the invention.
Fig. 1 (c) is the vertical view that swings die body in the specific embodiment of the invention.
Fig. 2 swings the part B of die body and the annexation synoptic diagram of part C in the specific embodiment of the invention.
Fig. 3 is the structural drawing of measuring the system of frame swing in the specific embodiment of the invention.
Fig. 4 is the reconstructed image that CT equipment scans rear formation in the specific embodiment of the invention to swinging die body.
Fig. 5 is to carrying out the curve map that half peak value overall with is measured to position fixing in Fig. 4 image in the specific embodiment of the invention.
Fig. 6 be the rotation angle β that swings die body be 0 amplitude of fluctuation when spending with the swing factor between relation curve.
To be the rotation angle β that swings die body be the relation curve between-45 amplitudes of fluctuation when spending and the swing factor to Fig. 7.
Fig. 8 be the rotation angle β that swings die body be 90 amplitudes of fluctuation when spending with the swing factor between relation curve.
Fig. 9 is the structural drawing of initial angle computing unit in the specific embodiment of the invention.
Figure 10 is the flow chart of steps of carrying out the method for initial angle calculating in the specific embodiment of the invention.
Figure 11 is the structural drawing that swings factor calculating unit in the specific embodiment of the invention.
Figure 12 calculates the method flow diagram that swings the factor and determine amplitude of fluctuation in the specific embodiment of the invention.
Figure 13 is the flow chart of steps of measuring the method for frame swing in the specific embodiment of the invention.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, the present invention is described in more detail by the following examples.
In the present invention, the horizontal direction of examination couch turnover frame is the z direction of principal axis in the definition CT equipment, and the direction of examination couch vertical lifting is the y direction of principal axis, and the y direction of principal axis is vertical with the z direction of principal axis, with y direction of principal axis and z direction of principal axis all the direction of quadrature then be the x direction of principal axis.Generally, frame can rotated with scan image in an x-y plane in the situation about not tilting, and the swing of frame be on the z direction of principal axis to the departing from of x-y plane, quantitatively can be understood as plane of rack and this formed inclined degree in x-y plane at numerical value.
I: die body design
In the operation of CT equipment, die body (phantom) is simulated CT equipment to patient's scanning process or is carried out such as simulated measurements such as tomography width measures through being commonly used to.The present invention designs a kind of novel being used for and measures the die body (rear claim " swing die body ") that frame swings, and it is very responsive that its frame to CT equipment is swung, thus the degree that the Measurement accuracy frame swings.
Fig. 1 is the structural representation that is used for the swing die body of measurement frame swing in embodiment of the present invention.Wherein, Fig. 1 (a) is the front elevation of this swing die body; Fig. 1 (b) is the left view of this swing die body; Fig. 1 (c) is the vertical view of this swing die body.
This swing die body in the embodiment mainly comprises first component and second component, represents with part A and part B respectively in Fig. 1.Described first component is rectangular parallelepiped, zone and lower area tilt to embed respectively aluminium strip and keep its central region not have aluminium strip embedding at an upper portion thereof, and two embedded aluminium strips become identical, the positive and negative opposite angle of order of magnitude with length direction by described first component with the plane that Width forms respectively; Described second component is to drive the right cylinder that described first component rotates, and it holds described first component.In the preferred embodiment, described die body also comprises the 3rd parts, represents with part C in Fig. 1.Described the 3rd parts respectively with described second component be connected the inspection of CT equipment and partly be connected, in order to support described second component and described die body be fixed on the described inspection part.Below just introduce respectively each parts of this swing die body.
Part A is the core that swings die body in this embodiment.This part A is the rectangular parallelepiped plate of being made by the PMMA material, its in the length on the z direction of principal axis much smaller than its length on x axle and y direction of principal axis.Two aluminium strips that tilt to embed respectively one fixed width at upper area and the lower area of A part.The length of part A on the y direction of principal axis is 320mm, length on the x direction of principal axis is determined by aluminium strip and the formed angle of x axle of inclination's embedding, the z axle scope of the length on the z direction of principal axis and the desired covering of operator decides, and this design with CT equipment is relevant.
By embedded part A respectively up and down two al zone thickness in two zones be 0.2mm, size on the y direction of principal axis is 120mm, their tilt respectively upper area and lower areas of embedded part A rectangular parallelepiped plate, shown in each figure among Fig. 1, so that do not have aluminium strip to embed in the 80mm scope of part A in the middle part of the y direction of principal axis is in, shown in the dash area among each figure of Fig. 1.That is to say that two aluminium strips all have the side-play amount of 40mm with respect to the center of part A on the y direction of principal axis up and down.
Two aluminium strips are respectively with among the inclination angle embedded part A that becomes same absolute value with the x-y plane up and down, and shown in two oblique lines in the part of the A among Fig. 1 (c), its middle and upper part aluminum strip becomes positive-angle with the x-y plane, and the bottom aluminum strip becomes negative angle with the x-y plane.The size at this inclination angle determines by the CT device design, but usually can be much larger than the arctan (1/4) in the employed general die body 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 of being made by the PMMA material, and its size is determined by size and the CT device design of A part.This right cylinder one side panel middle part has rectangular recess, in order to holding portion A, shown in Fig. 1 (b) and Fig. 1 (c).The major function of part B is holding portion A and drives the rotation that part A carries out accurate angle (for example spending as a unit with 5).In order to carry out the rotation of accurate angle, can have on the panel of part B range from-90 the degree to+90 the degree, be spaced apart 5 the degree scales, shown in Fig. 1 (a).It will be understood by those skilled in the art that in order accurately to determine the purpose of the anglec of rotation this range also can be arranged on B and partly form in relative rotation on the miscellaneous equipment.
Fig. 2 swings the part B of die body and the annexation synoptic 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 of being made by the PMMA material, and its size is greater than the size of B part, and concrete size is determined by size and the CT device design of B part.Part C is used for support section B, and by the fixed mechanism on its rear panel, shown in Fig. 1 (b) and Fig. 1 (c), swing die body integral body is fixed on the inspection part of CT equipment, for example on the examination couch.
It will be appreciated by those skilled in the art that, only when being used separately, the swing die body in this embodiment just need in swinging die body, the C part be set, and when the swing die body in this embodiment is integrated in other sweep object, as on the die body time, then the B part directly can be fixed on other sweep object by modes such as fixed mechanisms, and need not in this swing die body, to arrange the C part.
Those skilled in the art also are appreciated that, make by the PMMA material although swing three parts of A, B, C of die body in embodiment, one of them or a plurality of part also can have similarly by other, make from the material that aluminium presents obvious different CT scan imaging characteristics.
II: frame swings measuring system and measuring method
Fig. 3 is the structural drawing of measuring the system of frame swing in the specific embodiment of the invention.
The amplitude of fluctuation of CT equipment mid frame is measured by this system with the swing die body.As shown in Figure 3, this system comprises: initial angle computing unit 10, for the initial angle of calculating CT equipment; Optimum rotation angle determining unit 20 is for the optimum rotation angle of determining described swing die body according to the described initial angle that calculates; Swing factor calculating unit 30, be used for according to the described swing die body of described optimum rotation angle scans the swing factor that resulting reconstructed image calculates CT equipment to rotating extremely; And amplitude of fluctuation determining unit 40, be used for according to the described initial angle, the determined described optimum rotation angle that calculate and the described swing factor that calculates, determine the amplitude of fluctuation of described CT equipment by inquiry swinging model database.
In the research that swings for frame, can embody with swing curve the swing characteristic of frame.This swing curve is that frame is at the curve of a rotation period (being 2 π angles of a circumference) mid frame angle change.We can be defined as amplitude of fluctuation σ with the amplitude peak at a rotation period mid frame angle of inclination, and we also are by determining that this amplitude of fluctuation σ realizes quantitative measurment that frame is swung in the present invention.
In the scanning process of CT equipment, X ray bulb present position is an important parameter, usually with projected angle (projection angle), namely line and x axle positive dirction angulation characterize between X ray bulb loca and the scanning center (Iso center).Initial angle ω 0 among the present invention is defined as in the CT equipment swing curve with respect to the delay angle of projected angle.For a given CT equipment, because the otherness of its system hardware configuration has determined the initial angle ω 0 that each CT equipment is unique and fixing.According to inventor's research, initial angle ω 0 has appreciable impact for swinging die body to the susceptibility that frame swings, thereby is the important parameter of measuring in the frame swing process.
Therefore in the present invention, can be by calculating initial angle ω 0, and and then definite amplitude of fluctuation σ come the swing degree of quantitative measurment frame.In 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, thereby realize the quantitative measurment to the frame swing.
(1) calculates the mode that swings the factor
Fig. 4 is the reconstructed image that CT equipment scans rear formation in the specific embodiment of the invention to swinging die body.Fig. 5 carries out the curve map that half peak value overall with (Full Width at HalfMaximum, FWHM) is measured to Fig. 4 reconstructed image to position fixing in the specific embodiment of the invention.Wherein, FWHM refers to that ordinate is peak value one half in two-dimensional curve figure, corresponding to the width value on the horizontal ordinate.In Fig. 5, horizontal ordinate is that certain gives the pixel value on the position fixing straight line in the reconstructed image, and ordinate is the standard CT value, therefore by reconstructed image Fig. 4 of the swing die body that obtained, and just can be in the hope of the FWHM value of each coordinate position in the image.
For easy analysis, define in the present invention a variable relevant with the frame swing---swing the factor (WobblingFactor, WF).The computing formula (1) of the swing factor WF of certain given coordinate position is as follows in reconstructed image:
Wherein, FWHM|
σ, RIt is the FWHM value of in CT equipment to be measured (the CT equipment of corresponding amplitude of fluctuation σ), being determined by the R value; ε |
RIt is the FWHM value of in idealized system (the CT equipment of amplitude of fluctuation σ=0), being determined by the R value; 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 the Iso center distance on the y direction of principal axis.Note, in swinging the die body rotation process, with the reconstructed image rotation to angle shown in Figure 4, namely so that demonstrating angle that up and down two line zones of having embedded aluminium strip are in vertical position and measure the size of 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 the reconstructed image after the scanning is carried out emulation, then utilize the above-mentioned formula position that the R value is different on die body to record respectively the value that swings factor WF.
In a specific embodiment of the present invention, take 10mm as the interval, R=-150mm ,-140mm ... ,-60mm ,-50mm, 50mm, 60mm ..., 140mm, 150mm the position measure respectively the value that swings factor WF.By above to the introduction of the structure that swings die body as can be known, above-mentioned position all is the position that embeds corresponding to having aluminium strip on the part A.Afterwards, utilize above-mentioned a plurality of swing factor WF values of calculating, calculate by following formula (2) and on average swing the factor (Average Wobbling Factor), and will be somebody's turn to do the average swing factor as the value of the swing factor WF of this CT equipment:
WF|
σ＝Ave(WF|
σ，R)………(2)
Wherein Ave (x) is the function that calculates 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 be by scanning respectively emulation to the swing die body that is in different rotary angle β, thereby obtain the swinging model database of various CT equipment under various environment, this rotation angle β can be determined by the anglec of rotation range on the part B of the swing die body of above introducing.In this swinging model database, can set up CT equipment amplitude of fluctuation σ, initial angle ω 0, swing factor WF and swing quantitative relation between the die body rotation angle β.
According to this swinging model database that system emulation obtains, Fig. 6, Fig. 7, Fig. 8 exemplarily show respectively the rotation angle β that swings die body be respectively 0 degree, when-45 degree and 90 are spent, the relation curve between amplitude of fluctuation σ and swing factor WF, the initial angle ω 0.
According to studies show that, as initial angle ω 0 fixedly the time (for certain given CT equipment), swing factor WF along with the increase of amplitude of fluctuation σ dull the increase.Simultaneously, swing the appreciable impact that factor WF and the relation between the amplitude of fluctuation σ are subject to initial angle ω 0, when initial angle ω 0 during near the rotation angle β of swing die body swing factor WF larger, shown in each figure of Fig. 6-8.
We can find out from Fig. 6-8, are 90 degree when swinging the difference of die body rotation angle β with initial angle ω 0, i.e. β-when ω 0=90 spends, swing the value minimum of factor WF; And when swing die body rotation angle β equated with initial angle ω 0, namely β-when ω 0=0 spent, the value that swings factor WF was maximum.Utilize above-mentioned character, we can calculate the swing factor WF when difference swings die body rotation angle β, and these the corresponding swing die body of maximal value rotation angle β that swing factor WF are the initial angle ω 0 of CT equipment.Further, by swing die body rotation angle β, the swing factor WF that calculates that determines and the initial angle ω 0 that has obtained, just can inquire about existing swinging model database and determine the value of amplitude of fluctuation σ, thereby obtain the frame amplitude of fluctuation of CT equipment.When the data that do not meet fully in the swinging model database, those skilled in the art can also utilize the data with existing in the database, adopt interpolation computing method well known in the art to determine the value of amplitude of fluctuation σ.
(3) calculate initial angle ω 0
Fig. 9 is the structural drawing 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, be used for to calculate CT equipment and be respectively-90 degree ,-45 degree, 0 degree, swing factor when 45 degree and 90 are spent in original swing die body rotation angle; First redefines unit 102, be used for to determine to swing described in the result that described the first computing unit 101 calculates the maximal value of the factor, and the corresponding original swing die body rotation angle of this maximal value is redefined is 0 degree, and two angles that will be adjacent 45 degree redefine and are that-45 degree and 45 spend; The second computing unit 103 is used for redefining-45 degree that unit 102 redefines and the angle between 45 degree take 15 degree as the interval to described first, calculates the swing factor of CT equipment; Second redefines unit 104, be used for to determine to swing described in the result that described the second computing unit 103 calculates the maximal value of the factor, and the corresponding original swing die body rotation angle of this maximal value is redefined is 0 degree, and two angles that will be adjacent 45 degree redefine and are that-45 degree and 45 spend; The 3rd computing unit 105 is used for redefining-45 degree that unit 104 redefines and the angle between 45 degree take 5 degree as the interval to described second, calculates the swing factor of CT equipment; And initial angle determining unit 106, be used for to determine to swing the maximal value of the factor described in the result that described the 3rd computing unit 105 calculates, and the corresponding original swing die body rotation angle of this maximal value is defined as the described initial angle of CT equipment.
Figure 10 is the flow chart of steps of carrying out the method for 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 calculates the value of the initial angle ω 0 of CT equipment with following method flow.
In step S11, the first computing unit 101 utilizes formula (1) and formula (2) to calculate respectively to swing die body rotation angle β for-90 degree ,-45 degree, 0 degree, when 45 degree and 90 are spent, the value of the swing factor WF of CT equipment.
In step S12, first redefines the maximal value that CT equipment swing factor WF in the above-mentioned result of calculation is found out in unit 102, it is 0 degree that the corresponding swing die body of this maximal value rotation angle β is redefined, and two angles that will be adjacent 45 degree redefine and are that-45 degree and 45 spend.
In step S13, angle between after 103 pairs of the second computing units redefine-45 degree and 45 degree is take 15 degree as the interval, utilize formula (1) and formula (2) again to calculate the value that CT equipment swings factor WF, namely calculate and swing the CT equipment that die body rotation angle β is positioned at-45 degree after redefining ,-30 degree ,-15 degree, 0 degree, 15 degree, 30 degree, 45 degree places and swing the value of factor WF.
In step S14, second redefines unit 104 according to the operation of the result of calculation repeated execution of steps S12 of step S13, redefines out-45 degree and 45 degree.That is, determine to swing the maximal value of the factor among the result that the second computing unit 103 calculates, and the corresponding swing die body of this maximal value rotation angle is redefined is 0 degree, and two angles that will be adjacent 45 degree to redefine be that-45 degree and 45 are spent.
In step S15, angle between after 105 pairs of the 3rd computing units redefine-45 degree and 45 degree is take 5 degree as the interval, utilize formula (1) and formula (2) again to calculate the value that CT equipment swings factor WF, namely calculate swing die body rotation angle β be positioned at-45 degree after redefining ,-40 degree ...-5 the degree, 0 the degree, 5 the degree ..., 40 degree, 45 degree places CT equipment swing the value of factor WF.
In step S16, initial angle determining unit 106 finds CT equipment to swing the maximal value of factor WF from step S15 result of calculation, and the corresponding original swing die body rotation angle β of this maximal value is initial angle ω 0.
Below, we are with the implementation of an example in explanation said method step.
In certain CT equipment, at first in step S11, utilize formula (1) and formula (2), calculate respectively and swing die body rotation angle β for-90 degree ,-45 degree, 0 degree, CT equipment swung the value of the factor WF when 45 degree and 90 were spent.In step S12, find in the above-mentioned result of calculation that it is 45 maximums when spending swinging die body rotation angle β that CT equipment swings factor WF, it is 0 to spend that the positions that will swing die body rotation angle β this moment and be 45 degree redefine, and two angles that will be adjacent 45 degree redefine and are-45 degree and 45 degree, and it is-45 to spend and 45 spend that two positions that are about to original swing die body rotation angle β and are 0 degree and 90 degree redefine.In step S13, calculate to swing the CT equipment that die body rotation angle β is positioned at-45 degree after redefining ,-30 degree ,-15 degree, 0 degree, 15 degree, 30 degree, 45 degree places and swing the value of factor WF, the CT equipment that namely calculate original swing die body rotation angle β and be 0 degree, 15 degree, 30 degree, 45 degree, 60 degree, 75 degree, 90 degree swing the value of factor WF.In step S14, the CT equipment in the above-mentioned result of calculation found swings-15 when the spending maximums of factor WF after to swing die body rotation angle β be to redefine, be 30 maximums when spending at original swing die body rotation angle β namely, will original swing die body rotation angle β be that the positions of 30 degree redefine this moment is 0 to spend, and two angles that will be adjacent 45 degree redefine and are-45 degree and 45 degree, and being about to that original swing die body rotation angle β reorientates for two positions of-15 degree and 75 degree is 45 to spend and 45 spend.In step S15, calculate to swing die body rotation angle β be positioned at-45 degree after redefining ,-40 degree ... 5 the degree, 0 the degree, 5 the degree ..., 40 degree, 45 degree places CT equipment swing the value of factor WF, the dynamic model body rotation angle β that namely calculates original pendulum for-15 degree ,-10 degree ... 25 the degree, 30 the degree, 35 the degree ... the CT equipment of 70 degree, 75 degree swings the value of factor WF.In step S16, the CT equipment in the above-mentioned result of calculation found swings-10 when the spending maximums of factor WF after to swing die body rotation angle β be to redefine, be 20 maximums when spending at original swing die body rotation angle β namely, this moments 20, degree was the initial angle ω 0 of CT equipment.
(4) determine optimum rotation angle β opt
The below determines to swing the optimum rotation angle β opt of die body with the initial angle ω 0 that above determines.
If the absolute value of the initial angle ω 0 of the CT equipment that calculates hereinbefore is less than or equal to 45 degree, then optimum rotation angle determining unit 20 is defined as optimum rotation angle β opt with this initial angle ω 0; If the absolute value of the initial angle ω 0 of CT equipment is greater than 45 degree, then optimum rotation angle determining unit 20 is defined as 45 degree or-45 degree with optimum rotation angle β opt, and its sign symbol is consistent with the symbol of initial angle ω 0.
For example, when the CT equipment initial angle ω 0 that calculates is 35 when spending, the optimum rotation angle β opt that then swings die body is 35 degree; And if the CT equipment initial angle ω 0 that calculates is for-60 when spending, the optimum rotation angle β opt that then swings die body is-45 degree.
(5) calculate the amplitude of fluctuation σ that swings factor WF and determine CT equipment
Before the amplitude of fluctuation σ that determines CT equipment, we at first will for given CT equipment, calculate the swing factor WF of CT equipment.
Figure 11 is the structural drawing that swings 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 that scanning element 301, coordinate swing factor calculating unit 302 and on average swing factor calculating unit 303, described scanning element 301 is used for given frame rotational speed, rotation to the described swing die body by described optimum rotation angle determining unit 20 determined described optimum rotation angle is scanned, to obtain the described reconstructed image of described swing die body; Described coordinate swings factor calculating unit 302 and calculates in the described reconstructed image coordinate position as the swing factor at R place take the formula (1) of above being introduced; Described average swing factor calculating unit 303 is calculated the average swing factor in the described reconstructed image with the formula (2) of being introduced as mentioned, and with the described swing factor of the described average swing factor as CT equipment.
Below, we illustrate the swing factor WF that calculates CT equipment in the specific embodiment of the invention and the method for determining the amplitude of fluctuation σ of CT equipment rack.
Figure 12 shows and calculates the method flow diagram that swings the factor and determine amplitude of fluctuation σ in the specific embodiment of the invention.
In step S41, the position of die body rotation to the optimum rotation angle β opt that above determines will be swung.
In step S42, a rotational speed of given CT equipment rack, scanning element 301 scans swinging die body with this given frame rotational speed.
In step S43, coordinate swings factor calculating unit 302 according to scanning resulting reconstructed image to swinging die body, utilizes formula (1) to calculate that coordinate position is the swing factor at R place in the reconstructed image; The average factor calculating unit 303 that swings is utilized formula (2), calculates the average swing factor of reconstructed image under the forebay rotational speed, and will be somebody's turn to do the average factor that swings as the value of the swing factor WF of CT equipment.
In step S44, the swing factor WF of the CT equipment that calculates among optimum rotation angle β opt, the step S43 according to determined swing die body and the CT equipment initial angle ω 0 that has obtained, amplitude of fluctuation determining unit 40 is determined CT equipment in the value of the amplitude of fluctuation σ under the forebay rotational speed by inquiring about existing swinging model database, thereby obtains the frame amplitude of fluctuation of CT equipment.When the data that do not meet fully in the swinging model database, those skilled in the art can utilize the data with existing in the database, adopt interpolation computing method well known in the art to determine the value of amplitude of fluctuation σ.
In step S45, judge whether in institute's organic frame rotational speed situation, to measure.If in all rotational speed situations, do not measure, then turn back to step S42, another rotational speed of given CT equipment rack is determined amplitude of fluctuation σ again; If in all rotational speed situations, measure, then the ending method flow process.
Like this, can calculate the amplitude of fluctuation σ of CT equipment under different frame rotational speeies by execution in step S42 repeatedly to the operation of step S44.
The comprehensive content of introducing above, the specific embodiment of the invention also provide a kind of die body that utilizes to measure the method that frame swings.Figure 13 is the flow chart of steps of measuring the method for frame swing 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 the initial angle of calculating CT equipment; Optimum rotation angle determining step S2 is used for the optimum rotation angle according to the next true described swing die body of the described initial angle that calculates; Swing factor calculation procedure S3, be used for according to the described swing die body of described optimum rotation angle scans the swing factor that resulting reconstructed image calculates CT equipment to rotating extremely; And amplitude of fluctuation determining step S4, be used for according to the described initial angle, the determined described optimum rotation angle that calculate and the described swing factor that calculates, determine 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 the operator or employed algorithm provides accurate foundation, thereby has improved the picture quality of reconstructed image.
The above only is preferred embodiment of the present invention, and is in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (15)
1. one kind is used for measuring the die body that CT equipment mid frame swings, and comprises first component (A) and second component (B),
Described first component (A) is rectangular parallelepiped, zone and lower area tilt to embed respectively aluminium strip and keep its central region not have aluminium strip embedding at an upper portion thereof, and two embedded aluminium strips become identical, the positive and negative opposite angle of order of magnitude with length direction by described first component (A) with the plane that Width forms respectively;
Described second component (B) is the right cylinder that can drive described first component (A) rotation, 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 the 3rd parts (C) respectively with described second component (B) be connected the inspection of CT equipment and partly be connected, in order to support described second component (B) and described die body be fixed on the described inspection part.
3. die body according to claim 1, it is characterized in that the absolute value of the plane angulation that two aluminium strips that embed described first component (A) form with length direction and Width by described first component (A) respectively is 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 be provided with anglec of rotation range in order to the anglec of rotation of determining described second component (B).
5. the described die body of any one is characterized in that according to claim 1-4, makes the described first component (A) of described die body, described second component (B) and/or described the 3rd parts (C) by the PMMA material.
6. one kind is used die body to measure the system that CT equipment mid frame swings, and described system comprises:
Initial angle computing unit (10) is for the initial angle of calculating described CT equipment;
Optimum rotation angle determining unit (20) is for the optimum rotation angle of determining described die body according to the described initial angle that calculates;
Swing factor calculating unit (30), be used for according to the described die body of described optimum rotation angle scans the swing factor that resulting reconstructed image calculates described CT equipment to rotating extremely; And
Amplitude of fluctuation determining unit (40) is used for according to the described initial angle, the determined described optimum rotation angle that calculate and the described swing factor that calculates, and 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:
The first computing unit (101) is used for calculating described CT equipment and is respectively-90 degree ,-45 degree, 0 degree, swing factor when 45 degree and 90 are spent in original die body rotation angle;
First redefines unit (102), be used for to determine to swing described in the result that described the first computing unit (101) calculates the maximal value of the factor, and the corresponding original die body rotation angle of this maximal value is redefined is 0 degree, and two angles that will be adjacent 45 degree redefine and are that-45 degree and 45 spend;
The second computing unit (103) is used for redefining-45 degree that unit (102) redefines and the angle between 45 degree take 15 degree as the interval to described first, calculates the swing factor of described CT equipment;
Second redefines unit (104), be used for to determine to swing described in the result that described the second computing unit (103) calculates the maximal value of the factor, and the corresponding original die body rotation angle of this maximal value is redefined is 0 degree, and two angles that will be adjacent 45 degree redefine and are that-45 degree and 45 spend;
The 3rd computing unit (105) is used for redefining-45 degree that unit (104) redefines and the angle between 45 degree take 5 degree as the interval to described second, calculates the swing factor of described CT equipment; And
Initial angle determining unit (106), be used for to determine to swing the maximal value of the factor described in the result that described the 3rd computing unit (105) calculates, and the corresponding original die body rotation angle of this maximal value 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 optimum rotation angle determining unit (20) is defined as described initial angle the described optimum rotation angle of described die body; If the absolute value of the described initial angle of described CT equipment is greater than 45 degree, then described optimum rotation angle determining unit (20) is defined as 45 degree or-45 degree with the described optimum rotation angle of described die body, and its sign symbol is consistent with the sign symbol of described initial angle.
9. system according to claim 6 is characterized in that, described swing factor calculating unit (30) comprises that scanning element (301), coordinate swing factor calculating unit (302) and the average factor calculating unit (303) that swings,
Described scanning element (301) is used for given frame rotational speed, rotation to the described die body by the determined described optimum rotation angle of described optimum rotation angle determining unit (20) is scanned, to obtain the described reconstructed image of described die body;
Described coordinate swings factor calculating unit (302) is calculated given coordinate position place in the described reconstructed image with following formula the swing factor:
Wherein, R is coordinate position and the scanning center distance on examination couch vertical lifting direction, FWHM|
σ, RBe in having the described CT equipment of amplitude of fluctuation σ by the determined half peak value overall with value of R, ε |
RBe in the desirable CT equipment that does not exist frame to swing by the determined half peak value overall with value of R, abs (x) is the function of trying to achieve x variable absolute value;
Described average swing factor calculating unit (303) is calculated the average swing factor in the described reconstructed image with following formula, and with the described swing factor of the described average swing factor as described CT equipment:
WF|
σ＝Ave(WF|
σ，R)
Wherein, Ave (x) is the function that calculates variable x mean value.
10. the described system of any one is characterized in that according to claim 6-9, determines described swinging model database by system simulation technology.
11. one kind is used die body to measure the method that CT equipment mid frame swings, described method comprises:
The initial angle calculation procedure is for the initial angle of calculating described CT equipment;
Optimum rotation angle determining step is for the optimum rotation angle of determining described die body according to the described initial angle that calculates;
Swing factor calculation procedure, be used for according to the described die body of described optimum rotation angle scans the swing factor that resulting reconstructed image calculates described CT equipment to rotating extremely; And
The amplitude of fluctuation determining step is used for according to the described initial angle, the determined described optimum rotation angle that calculate and the described swing factor that calculates, and determines the amplitude of fluctuation of described CT equipment by inquiry swinging model database.
12. method according to claim 11 is characterized in that, described initial angle calculation procedure comprises:
The first calculation procedure is used for calculating described CT equipment and is respectively-90 degree ,-45 degree, 0 degree, swing factor when 45 degree and 90 are spent in original die body rotation angle;
The first steps of redefinition, be used for swinging described in the result who determines to calculate in described the first calculation procedure the maximal value of the factor, and the corresponding original die body rotation angle of this maximal value is redefined is 0 degree, and two angles that will be adjacent 45 degree redefine and are that-45 degree and 45 spend;
The second calculation procedure take 15 degree as the interval, is calculated the swing factor of described CT equipment for the angle between-45 degree and 45 that redefine at described the first steps of redefinition are spent;
The second steps of redefinition, be used for swinging described in the result who determines to calculate in described the second calculation procedure the maximal value of the factor, and the corresponding original die body rotation angle of this maximal value is redefined is 0 degree, and two angles that will be adjacent 45 degree redefine and are that-45 degree and 45 spend;
The 3rd calculation procedure take 5 degree as the interval, is calculated the swing factor of described CT equipment for the angle between-45 degree and 45 that redefine at described the second steps of redefinition are spent; And
The initial angle determining step is used for swinging described in the result who determines to calculate in described the 3rd calculation procedure the maximal value of the factor, and the corresponding original die body rotation angle of this maximal value is defined as the described initial angle of described CT equipment.
13. method 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 in described optimum rotation angle determining step, described initial angle is defined as the described optimum rotation angle of described die body; If the absolute value of the described initial angle of described CT equipment greater than 45 degree, then is defined as 45 degree or-45 degree with the described optimum rotation angle of described die body in described optimum rotation angle determining step, its sign symbol is consistent with the sign symbol of described initial angle.
14. method according to claim 11 is characterized in that, described swing factor calculation procedure comprises that scanning step, coordinate swing factor calculation procedure and on average swing factor calculation procedure,
In described scanning step, with given frame rotational speed, the described die body of rotation to the described optimum rotation angle of determining in described optimum rotation angle determining step scanned, to obtain the described reconstructed image of described die body;
Swing in the factor calculation procedure at described coordinate, calculate the swing factor at given coordinate position place in the described reconstructed image with following formula:
Wherein, R is coordinate position and the scanning center distance on examination couch vertical lifting direction, FWHM|
σ, RBe in having the described CT equipment of amplitude of fluctuation σ by the determined half peak value overall with value of R, ε |
RBe in the desirable CT equipment that does not exist frame to swing by the determined half peak value overall with value of R, abs (x) is the function of trying to achieve x variable absolute value;
In described average swing factor calculation procedure, calculate the average swing factor in the described reconstructed image with following formula, and with the described swing factor of the described average swing factor as described CT equipment:
WF|
σ＝Ave(WF|
σ，R)
Wherein, Ave (x) is the function that calculates variable x mean value.
15. the described method of any one is characterized in that according to claim 11-14, determines described swinging model database by system simulation technology.
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| CN104198506A (en) * | 2014-08-27 | 2014-12-10 | 清华大学 | Small-angle self-pendulum type large-size multi-layer spiral CT (Computed Tomography) equipment and inspection method |
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| WO1998051220A1 (en) * | 1997-05-13 | 1998-11-19 | Analogic Corporation | Wobbling focal spot ct optimal channel filter |
| CN1657009A (en) * | 2005-03-22 | 2005-08-24 | 东软飞利浦医疗设备***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 |
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| WO1998051220A1 (en) * | 1997-05-13 | 1998-11-19 | Analogic Corporation | Wobbling focal spot ct optimal channel filter |
| CN1657009A (en) * | 2005-03-22 | 2005-08-24 | 东软飞利浦医疗设备***有限责任公司 | CT apparatus geometric parametar corrction method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104198506A (en) * | 2014-08-27 | 2014-12-10 | 清华大学 | Small-angle self-pendulum type large-size multi-layer spiral CT (Computed Tomography) equipment and inspection method |
| CN104198506B (en) * | 2014-08-27 | 2017-11-07 | 清华大学 | Low-angle is from pendulum-type large-sized multiple layer helical CT device and inspection method |
| US11022569B2 (en) | 2014-08-27 | 2021-06-01 | Nuctech Company Limited | Low-angle self-swinging, large-scale multi-slice spiral computed tomography apparatus and inspection method |
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