CN107507257A - A kind of big visual field indexing migration reconstruction method and its system - Google Patents
A kind of big visual field indexing migration reconstruction method and its system Download PDFInfo
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- CN107507257A CN107507257A CN201710690043.0A CN201710690043A CN107507257A CN 107507257 A CN107507257 A CN 107507257A CN 201710690043 A CN201710690043 A CN 201710690043A CN 107507257 A CN107507257 A CN 107507257A
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- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T11/00—2D [Two Dimensional] image generation
- G06T11/003—Reconstruction from projections, e.g. tomography
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T11/00—2D [Two Dimensional] image generation
- G06T11/003—Reconstruction from projections, e.g. tomography
- G06T11/006—Inverse problem, transformation from projection-space into object-space, e.g. transform methods, back-projection, algebraic methods
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- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2211/00—Image generation
- G06T2211/40—Computed tomography
- G06T2211/421—Filtered back projection [FBP]
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Abstract
The invention provides a kind of big visual field indexing migration reconstruction method, comprise the steps：With rotary index αj' under actual measurement CT data replace rotary index αjUnder CT data to be mended, treat the compensation for mending CT data to realize, CT data are that next X ray of a rotary index passes through the CT values collected after determinand by X-ray detector unit；The vertical shift under each rotary index of determinand is measured, and probe angle is corrected according to the vertical shift, obtains tuning detector angle；Using the tuning detector angle of whole CT data as parameter, backprojection reconstruction is filtered.
Description
Technical field
The present invention relates to CT image reconstructions field, more particularly to a kind of big visual field indexing migration reconstruction method and its system.
Background technology
19 end of the centurys, William roentgen are found that X ray.After this, internal structure of body is examined using X ray
Survey a kind of important means become for Non-Destructive Testing.With the development of computer technology, computer application gradually penetrates into
Among every subjects.CT (Computed Tomography) Computed tomography, is exactly computer science and high energy thing
A kind of brand-new nondestructiving detecting means that Neo-Confucianism intersects to form.The technology realize testee faultage image scanning with again
Build.And it is widely used in the field such as medical science and industry.
In numerous CT systems, horizontal industrial CT system is in the field such as railway and Aero-Space extensive application.It is horizontal
Industrial CT system is generally used for detecting longer column object under test.Object under test is lying on clamping rotary system, utilizes folder
Floating self-clamping module on tool clamps object under test, fixture is formed rigid body with object under test.By driving fixture to rotate, make to treat
Thing rotation is surveyed, completes scanning of the CT beams to determinand.
Regular industrial CT system uses III generation CT scan more, i.e. fan-beam ray scanning covering of the fan can include whole determinand
Body.But when object under test is relatively large in diameter, it may appear that x-ray detector array can not be included entirely with fan-beam ray scanning covering of the fan
The situation of object under test.Now, industrial CT system can use big visual field CT scan, i.e. fan-beam ray scanning covering of the fan only includes part
Object under test.
When object under test weight is larger and shell is rigidly insufficient, to ensure object under test safety, is not clamped and damage by fixture
Bad, floating self-clamping module has certain elasticity.The characteristic can ensure object under test vessel safety, but in rotation sweep, treat
Same rigid body can not be kept with fixture by surveying object.The characteristic can cause each scanning rotary index in CT scan can be in Y side
To (scanning vertical direction), X-direction (scanning radial direction) produces skew.Rotary index offset can influence CT picture qualities.
Horizontal CT system under specific circumstances, because of grasping system problem, it may appear that each rotary index data-bias situation.
Existing scheme is only capable of handling the problem of each rotary index offset is fixed, and it is different to handle each rotary index offset
The problem of；The big visual field CT of existing scheme rebuilds and uses iterative approximation, possesses preferable reconstruction quality.But because of iterative approximation side
The serial computing characteristic of method, cause iterative approximation can not parallel speed-up computation, rebuild speed it is slower.
The content of the invention
To solve the above problems, the invention discloses a kind of big visual field indexing migration reconstruction method, the present invention can remove and regard greatly
During CT scan, the problem of because of grasping system, occur determinand in the vertical direction under each rotary index occur it is different degrees of
The reconstruction error for offseting and bringing, the invention discloses a kind of big visual field indexing migration reconstruction method, swept based on fan-beam x-ray bombardment
Retouch thing and be projected on X-ray detector, determinand rotates around pivot during measurement, the X-ray detection under different rotary indexing
Device surveys CT data corresponding to obtaining, meanwhile, measure the offset Δ for corresponding to the lower determinand in the vertical direction of different rotary indexing
d；And each X under corresponding rotation indexing is calculated by the distance value l of the offset Δ d, x-ray source to determinand pivot vertical line
The indexing deviation angle Δ α of ray detector, calculation formula areAccording to the indexing deviation angle Δ
α is corrected to probe angle, obtains tuning detector angle, and formula isIts
Middle αjFor the actual detection angle of detector, α 'jFor tuning detector angle；Realized by compensation data and filtered back-projection
CT image reconstructions；Wherein, the coverage of fan-beam X ray comprises at least the outward flange of determinand from vertical direction to pivot
Part.
Further, the method for the compensation data is：For any rotary index θi, a CT data Data to be compensated
(θi, ψ+γ) and with rotary index it is θiThe γ of+π+2, probe angle are that CT data are surveyed corresponding to ψ-γ to replace, i.e. Data
(θi, ψ+γ) and=Data (θi+ π+2 γ, ψ-γ), wherein, ψ is the angle of fan-beam center line and pivot-x-ray source line,
γ is the angle of pivot-x-ray source line and virtual ray to be compensated.
Further, in θiUnder the γ of+π+2 rotary index, use X-ray detector in detection angle for αk、αk+1It is actual
CT data the Data ([θ of detectioni+π+2γ],αk)、Data([θi+π+2γ],αk+1) by interpolation calculation, to compensate because of X ray
Detector data collection discretization and lack its desired angle obtain CT data Data ([θi+π+2γ],αj), i.e.,
Wherein, αk＜ ψ-γ ＜ αk+1。
The invention also discloses a kind of big visual field indexing migration reconstruction system, including X-ray detector, x-ray source, bottom
Seat, it is characterised in that：Also include position sensor, controller and signal generator, the position sensor is arranged on big visual field
The system base of CT scan, the radial surface of detecting head face determinand, for obtaining the skew of determinand in the vertical direction
Amount, the X-ray detector, position sensor, the output of signal generator are connected with the input of controller.
Compared to prior art, the present invention has the advantages that：
1st, the reconstruction to CT data is realized in the case of rotary index vertical shift difference, apparent CT is obtained and rebuilds
Image.
2nd, breach big visual field CT and rebuild the limitation that must use iterative algorithm, by way of compensation data, make to regard greatly
Field CT image reconstructions also can save the time of CT detections by the way of filtered back projection.
Brief description of the drawings
Accompanying drawing 1 indexes migration reconstruction method flow diagram for a kind of big visual field of embodiment.
Accompanying drawing 2 is that big visual field indexes migration reconstruction system schematic.
Accompanying drawing 3 is CT compensation data principle schematics.
Accompanying drawing 4 is rotary index vertical shift and indexing deviation angle schematic diagram.
Accompanying drawing 5 is position sensor, X-ray detector, controller, the circuit logic theory diagram of signal generator.
Embodiment
The particular content that the invention will now be described in detail with reference to the accompanying drawings, as shown in Figure 2, the invention discloses one kind to regard greatly
Field indexing migration reconstruction system, including X-ray detector 4, x-ray source S, base 2, in addition to position sensor 3, controller 7
With signal generator 9, the position sensor 3 is arranged on the system base 2 of big visual field CT scan, detecting head face determinand 6
Radial surface, for obtaining the offset Δ d of the in the vertical direction of determinand 6, X-ray detector 4, position sensor 3, letter
The output of number generator 9 is connected with the input of controller 7.The trigger signal of signal generator 9, controller 7 receive same after signal
Step obtains the data of X-ray detector 4 and position sensor 3, and carries out calculating processing by controller 7.
The present invention also disclosed a kind of big visual field indexing migration reconstruction method, and accompanying drawing 1 is the step of the present invention.Such as accompanying drawing 4
A kind of big visual field indexing migration reconstruction method shown, that the present invention announces, this method are based on fan-beam x-ray projection, treat during measurement
Survey thing to rotate clockwise around 6 pivot O, its step is：
1st, the synchronous actual measurement CT data Data (θ for obtaining determinand 6 in each rotary indexi,αj) with determinand in vertical side
Upward offset Δ d, a CT data represent a rotary index θiUnder, a probe angle αjCorresponding CT values, wherein
Probe angle αjLine and fan-beam center line SE corner dimensions for X-ray detector unit-x-ray source S, θiRepresent rotation
Indexing.
2nd, when object under test weight is larger and shell is rigidly insufficient, to ensure object under test safety, do not clamped by fixture
Damage, floating self-clamping module have certain elasticity.The characteristic can ensure object under test vessel safety, but in rotation sweep,
Object under test can not keep same rigid body with fixture.The characteristic can cause each scanning rotary index in CT scan to sweep
Vertical direction and scanning radial direction are retouched, mainly scans vertical direction, produces skew.Rotary index offset can influence CT figures
As quality, it is therefore desirable to which the skew to each indexing determinand in the vertical direction is corrected, and its method is：
According to rotary index vertical shift data Δ d and x-ray source S to pivot vertical line l distance, arc tangent is utilized
Function, indexing deviation angle is calculated,Probe angle α in step 1 is added with indexing deviation angle Δ αj,
Probe angle α ' after being correctedj, formula is,
3rd, according to basic physics theory, intensity I0Single energy X ray absorptionmetry through some uneven object when, X ray
The X-ray intensity that detector receives meets Beer law：
Wherein, L is a certain path that X ray passes through, and μ (x, y) is attenuation coefficient, I0For X ray incident intensity, I penetrates for X
Line is emitted intensity.From above formula, CT data and the incident direction of X ray that X ray is obtained by a line segment of determinand
It is unrelated.
As shown in Figure 4, the scope among SC and SD is the ray surface sweeping scope of big visual field CT system, in θiRotary index
Under, the line segment AB parts marked on figure are not in CT system scanning range, i.e. Data (θi, ψ+γ) and it is not present, then now line
Section AB CT data are numerically equal with another rotary index lower line segment BA CT data.Wherein, ψ be fan-beam center line SE with
Angle the ∠ OSE, γ of pivot O-X radiographic source S lines are pivot O-X radiographic source S lines and virtual ray to be compensated
SAB angle ∠ OSB, wherein fan-beam center line SE are ∠ CSD angular bisectors.
Determinand 6 turns clockwise around pivot O, can regard x-ray source S and X-ray detector as while in rotation
Heart O rotate counterclockwises, when S goes to S ' position in accompanying drawing 4, the CT values under this rotary index are Data (θn,αm), S ' is AB
Extended line and using O as the center of circle, OS are the intersection point of the circle of radius, are easy to get now rotary index θ according to basic geometrical principlenIt is worth for θi+
Probe angle α corresponding to the γ of π+2, ray S ' BAmFor ψ-γ, i.e.,
Data(θi, ψ+γ) and=Data (θi+π+2γ,ψ-γ)
It is in a practical situation discrete data in view of X-ray detector rotary index, is not necessarily present rotary index θi+
The γ data of π+2, rotary index data it can be substituted existing for hithermost one group, it is assumed that the replacement rotary index data are Data
([θi+π+2γ],αm), wherein αm=ψ-γ, but because angle has offset, beam can not be completely superposed, and need to be revolved with the replacement
Turn indexing θiHithermost two beam datas compensate under the γ of+π+2, and compensation formula is：
Wherein, αk＜ ψ-γ ＜ αk+1.Other line segments treated in compensatory zone carry out aforesaid operations, obtain area to be compensated
The offset data of all line segments in domain, probe angle correction is carried out to all CT data.
4th, backprojection reconstruction is filtered as data source using whole CT data after correction, formula is：
CTReconsData (x, y)=FBP (Data (θi,α′j)
Finally illustrate, the above embodiments are merely illustrative of the technical solutions of the present invention and it is unrestricted, although with reference to compared with
The present invention is described in detail good embodiment, it will be understood by those within the art that, can be to the skill of the present invention
Art scheme is modified or equivalent substitution, and without departing from the objective and scope of technical solution of the present invention, it all should cover at this
Among the right of invention.
Claims (4)
1. a kind of big visual field indexing migration reconstruction method, scans thing based on fan-beam x-ray bombardment and is projected in X-ray detector
On, determinand rotates around pivot during measurement, it is characterised in that X-ray detector obtains corresponding under different rotary indexing
Actual measurement CT data, meanwhile, measure the offset Δ d of the corresponding lower determinand in the vertical direction of different rotary indexing；And pass through
The offset Δ d, the distance value l of x-ray source to determinand pivot vertical line calculate each X ray under corresponding rotation indexing and visited
The indexing deviation angle Δ α of device is surveyed, calculation formula isAccording to the indexing deviation angle Δ α to visiting
Survey device angle to be corrected, obtain tuning detector angle, formula isWherein αj
For the actual detection angle of detector, αj' it is tuning detector angle；Realize that CT schemes by compensation data and filtered back-projection
As rebuilding；Wherein, the coverage of fan-beam X ray comprises at least the outward flange of determinand from vertical direction to the portion of pivot
Point.
A kind of 2. big visual field indexing migration reconstruction method as claimed in claim 1, it is characterised in that the side of the compensation data
Method is：For any rotary index θi, a CT data Data (θ to be compensatedi, ψ+γ) and with rotary index it is θiThe γ of+π+2, detection
Device angle is that CT data are surveyed corresponding to ψ-γ to replace, i.e. Data (θi, ψ+γ) and=Data (θi+ π+2 γ, ψ-γ), wherein, ψ
The angle of fan-beam center line and pivot-x-ray source line, γ be pivot-x-ray source line with it is to be compensated virtual
The angle of ray.
A kind of 3. big visual field indexing migration reconstruction method as claimed in claim 2, it is characterised in that：In θiThe γ of+π+2 rotation
Under indexing, use X-ray detector in detection angle for αk、αk+1CT data the Data ([θ of actual detectioni+π+2γ],αk)、
Data([θi+π+2γ],αk+1) by interpolation calculation, to compensate what is lacked by the discretization of X-ray detector data acquisition
Its CT data Data ([θ obtained in desired anglei+π+2γ],αj), i.e.,
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Wherein, αk＜ ψ-γ ＜ αk+1。
4. a kind of big visual field indexing migration reconstruction system, including X-ray detector, x-ray source, base, it is characterised in that：Also wrap
Position sensor, controller and signal generator are included, the position sensor is arranged on the system base of big visual field CT scan, visits
The radial surface of gauge head face determinand, for obtaining the offset of determinand in the vertical direction, the X-ray detector,
Position sensor, the output of signal generator are connected with the input of controller.
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| CN113745077A (en) * | 2021-08-07 | 2021-12-03 | 电科睿视技术(北京)有限公司 | Error correction device for X-ray tube and use method thereof |
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| CN102253061A (en) * | 2011-04-19 | 2011-11-23 | 东南大学 | Vertical cone beam CT (Computed Tomography) imaging calibration system and method applying same |
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| CN103654833A (en) * | 2013-11-19 | 2014-03-26 | 中国科学院过程工程研究所 | Method and device for determining detector deflection angle of CT |
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