CN107049349A - A kind of conical beam CT imaging system based on attenuating plate - Google Patents
A kind of conical beam CT imaging system based on attenuating plate Download PDFInfo
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- CN107049349A CN107049349A CN201710065172.0A CN201710065172A CN107049349A CN 107049349 A CN107049349 A CN 107049349A CN 201710065172 A CN201710065172 A CN 201710065172A CN 107049349 A CN107049349 A CN 107049349A
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- attenuating plate
- attenuating
- image reconstruction
- plate
- reconstruction software
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- 238000013170 computed tomography imaging Methods 0.000 title claims abstract description 6
- 239000000463 material Substances 0.000 claims description 13
- 238000004364 calculation method Methods 0.000 claims description 11
- 238000003384 imaging method Methods 0.000 claims description 11
- 238000009826 distribution Methods 0.000 claims description 9
- 239000011159 matrix material Substances 0.000 claims description 9
- 238000000034 method Methods 0.000 description 12
- 230000000694 effects Effects 0.000 description 3
- 238000001514 detection method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 239000004411 aluminium Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000002059 diagnostic imaging Methods 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000008447 perception Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/40—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for generating radiation specially adapted for radiation diagnosis
- A61B6/4064—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for generating radiation specially adapted for radiation diagnosis specially adapted for producing a particular type of beam
- A61B6/4085—Cone-beams
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/02—Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
- A61B6/03—Computerised tomographs
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
Abstract
The invention discloses a kind of conical beam CT imaging system based on attenuating plate, by setting attenuating plate between imageable target and flat panel detector, to stop most of scattered rays from imageable target, while allowing enough principal rays to pass through.Removed by calculating the scattered rays from attenuating plate in projected image, and by it from projected image, so as to reduce the interference that scattered rays is caused, obtain clearly reconstruction image.
Description
Technical field
Conical beam CT is imaged.
Background technology
Conical beam CT because the dose of radiation to patient is low, have higher resolution ratio in the axial direction, it is simple in construction and just
The advantages of miniaturization, used in increasing hospital.But it is due to that the volume image-forming principle of conical beam CT radiographic source is determined
Picture quality will largely be reduced by having determined scattered rays.Scattering how is removed, flat panel detector CT images point are given full play to
The high advantage of resolution, is the key for obtaining high-resolution conical beam CT image.At present, the mode obtained according to scattered photon, is removed
The method of scattered photon can be divided into following two class：
One class is the image flame detection algorithm based on software, including noise suppressed restructing algorithm, scatter distributions analytical algorithm or is based on
The scattering algorithm of statistics.Such method can obtain certain effect, but also have respective shortcoming, such as analytic method shortcoming essence
Degree, and the Monte Carlo EGS4 method based on statistics is limited by calculating speed, clinical practice is restricted.
Another kind of is hardware based scatter correction method.A part of hardware based method is directly reduced to up to flat board and visited
The scattered rays of device is surveyed, such as increases the distance between imageable target and detector；Added between imageable target and detector anti-
Scatter grid；Butterfly attenuating plate etc. is added between radiographic source and imageable target.In actual applications, imageable target and flat board are visited
Survey what the distance between device was often limited.Backscattering grid is effective to cupping artifact caused by scattering but caused to scattering
Strip artifact effect is limited, and Contrast-to-noise ratio can be also reduced in some cases.Butterfly attenuating plate can reduce projection centre
Scattered rays principal ray ratio, while can also increase the scattered rays principal ray ratio at edge.Some hardware based method passes through
Shutter of the design with variously-shaped gap estimates scatter distributions, or but this kind of method need it is extra to shield portions
Scanning, increase sweep time；Need, by interpolation calculation shield portions, to lose resolution ratio.What roc of passing away proposed《It is a kind of
Scatter correction based on attenuating plate》（Electronic letters, vol the 7th phase in 2011）Using the uniform aluminium material attenuating plates of 2mm, attenuating plate is located at
Between radiographic source and imageable target, it needs with attenuating plate and is imaged twice without attenuating plate, the spoke that increase patient is subject to
Penetrate.
Some go scattering scheme is then comprehensive to use above-mentioned software and hardware method, but the intrinsic deficiency of various methods still limits it
The effect of scattering and clinical practice.
The content of the invention
In conical beam CT imaging process, because X-ray principal ray has higher energy than scattered rays, therefore principal ray is than dissipating
Ray has stronger penetration capacity.The attenuating plate that the present invention passes through the setting uniform material between imageable target and flat panel detector
To stop the scattered rays from imageable target.Attenuating plate has the most of scattering from imageable target of certain thickness blocks
Line, while allowing enough principal rays to pass through.Principal ray by attenuating plate during can further produce scattered rays, this causes
The scattered rays composition of projected image is essentially from attenuating plate on flat panel detector.Because attenuating plate has known shape, material
Uniformly, it is and fixed with the distance between flat panel detector.Therefore quickly it can be projected by projected image with accurate calculate
Composition from attenuating plate scattered rays in image.It had both been through declining that the composition from attenuating plate scattered rays is subtracted from projected image
Subtract the principal ray composition of plate.By the material and the attenuation coefficient of THICKNESS CALCULATION attenuating plate of attenuating plate, it can obtain not passing through and decline
Subtract the distribution of the principal ray before plate.Imaging system rebuilds three dimensional CT data using the distribution of the principal ray before attenuating plate is not passed through.This side
Method does not need rescan, it is possible to reduce the influence of scattered rays, obtains clearly three-dimensional cone beam CT images.
Attenuating plate can be according to imageable target or the difference of scan mode, and corresponds to different shapes.
Timesharing is scattering into from attenuating plate in every projected image is calculated, would generally produce drop for reduction amount of calculation adopts
The contribution of scatters matrix of sample.But provided in the significantly down-sampled radio-frequency component that can be lost in contribution of scatters, embodiment 2
A kind of star contribution of scatters matrix, can preferably retain while amount of calculation is reduced the high frequency of contribution of scatters center into
Point.
Brief description of the drawings：
The attenuating plate position view of Fig. 1 embodiments 1；
The decay Board position of Fig. 2 embodiments 2 and schematic cross-section；
The star contribution of scatters matrix schematic diagram of Fig. 3 embodiments 2；
The decay Board position of Fig. 4 embodiments 3 and schematic cross-section.
Embodiment：
Embodiment 1：
The invention discloses a kind of conical beam CT imaging system based on attenuating plate, imaging system is by imaging device and image reconstruction
Software is constituted.Imaging device includes organic frame and the x-ray source being fixed in frame（101）, attenuating plate（103）With flat board detection
Device（104）.X-ray source（101）The x lines sent pass through imageable target（102）And attenuating plate（103）Afterwards in flat panel detector
（104）Upper imaging（See Fig. 1）.Imaging system is rotated, to obtain imaging mesh when gathering image by frame around imageable target
Mark the projected image of different angles.Imageable target（102）And flat panel detector（104）Between be provided with uniform material attenuating plate
（103）, this attenuating plate do not have any gap and hole.In frame rotary course, attenuating plate（103）Rotated together with frame, it is arrived
Flat panel detector（104）The distance between it is constant.For 100KeV X source, attenuating plate（103）For uniform water equivalent density material
Material, thickness is 3cm.
It is uniform in material due to attenuating plate regular shape and fixed with the distance between flat panel detector.Therefore by advance
The attenuating plate scattering kernel function of calculating quickly can calculate the scattering composition from attenuating plate in projected image with accurate（Text
Offer " Josh Star-Lack, Mingshan Sun, et.al. Efficient scatter correction using
asymmetric kernels. Proc SPIE 7258, Medical Imaging 2009: Physics of Medical
There is the detailed step that scattering is calculated in Imaging, 72581Z "）.Subtracted from projected image from attenuating plate scattering composition both
For through the principal ray composition of attenuating plate.The corresponding attenuation coefficient of THICKNESS CALCULATION passed through by the material and ray of attenuating plate,
It can obtain and not pass through the distribution of the principal ray before attenuating plate.It is finally three-dimensional using the distribution reconstruction of the principal ray before attenuating plate is not passed through
CT data, algorithm for reconstructing uses FDK algorithms.
Embodiment 2：
Hardware components are other same as Example 1 in addition to attenuating plate in this embodiment（See Fig. 2）.Attenuating plate in this embodiment
（201）For uniform water equivalent density material, because usually there is a scattered rays of greater proportion at the center of image, therefore by attenuating plate
Surface is designed as arc, and centre has bigger thickness preferably to stop scattered rays.For 100KeV X source, edges of boards of decaying
Edge thickness is 2.5mm, and center thickness is 3.5mm（See Fig. 2 bottoms attenuating plate schematic cross-section）.
Contribution of scatters matrix of one pencil beam principal ray on flat panel detector is typically the form on the left of Fig. 3, and A44 is
The center of pencil beam, both this pencil beam was to all pixels（Or down-sampled rear pixel）Contribution of scatters will be calculated, amount of calculation
It is very big.To reduce amount of calculation, we are with reference to the Clapsed Cone algorithms in Rapid Dose Calculation（See document " Collapsed cone
convolution of radiant energy for photon dose calculation in heterogeneous
media, Medcal Physics, Volume 16, Issue 4, 1989, pages 577-592”）, devise in flat board
Star contribution of scatters matrix on detector two dimensional surface（See on the right side of Fig. 3）, to reduce amount of calculation.It is star scattering on the right side of Fig. 3
The schematic diagram of matrix is contributed, the contribution of scatters of the pencil beam centered on B44 is divided into greyish white 8 alternate directions
Scattering in Cone, each Cone between adjacent camber line is concentrated in the pixel of Cone central axis（Such as upper left corner grey
Cone contribution of scatters is just concentrated in the pixels such as B33, B22, B11, B00）.So superposition or convolution algorithm are only needed to
Carried out on Cone directions, greatly reduce operand.Obtain being scattering into from attenuating plate using star contribution of scatters matrix computations
After point, the distribution of the principal ray before attenuating plate is not passed through using being calculated with identical method in embodiment 1, finally using the pressure of iteration
Contracting perception algorithm rebuilds three dimensional CT data.
Although this embodiment employs 8 direction Cone star contribution of scatters matrix, but not office in practical application
It is limited to 8 direction Cone.Cone can be added or reduced in different directions according to computational accuracy and calculating time requirement, it is more
The higher calculating accuracy of Cone directions correspondence, it also requires more calculating the time.
Embodiment 3：
Many conical beam CTs have two kinds of scan patterns of full-fan and half-fan, and less imageable target is generally used
Full-fan patterns, then need to use half-fan patterns to larger imageable target.Embodiment 1 and embodiment 2 are Full-
Fan is scanned, and flat panel detector is in middle position.This embodiment scans for half-fan, and flat panel detector offsets to one side（See figure
4）, attenuating plate（401）For uniform tungsten material, surface is eccentric cambered, and thickness 1.3mm, relatively thin edge thickness 1.0mm are thicker
Edge thickness 1.2mm（See Fig. 4 bottoms attenuating plate schematic cross-section）.Under Half-fan scan patterns, every projected image can be obtained
The imageable target of half must be more than（402）Projection, whole scanning needs the projected image of 360 degree of collection.The calculating of scattered rays
It is identical with minimizing technology and embodiment 2, then used by not passing through the distribution reconstruction three dimensional CT data of the principal ray before attenuating plate
The algorithm for reconstructing of half-fan mode-specifics（See document " Shuai Leng, et.al., Exact fan-beam image
reconstruction algorithm for truncated projection data acquired from an
asymmetric half-size detector, Physics in Medicine and Biology, Volume 50,
2005, pages 1805-1820”）.
Claims (6)
1. the invention discloses a kind of conical beam CT imaging system based on attenuating plate, it is characterised in that imaging system is filled by imaging
Put and visited with image reconstruction software composition, imaging device comprising organic frame and the x-ray source being fixed in frame, attenuating plate and flat board
Device is surveyed, attenuating plate is placed between imageable target and flat panel detector, and this attenuating plate does not have any gap and hole.
2. image reconstruction software according to claim 1, it is characterised in that this image reconstruction software is rebuilding three dimensional CT data
Before, calculate the scattering composition from attenuating plate in every projected image.
3. image reconstruction software according to claim 1, it is characterised in that this image reconstruction software is rebuilding three dimensional CT data
Before, first scattering composition, the material of attenuating plate and the THICKNESS CALCULATION according to projected image, from attenuating plate are not passed through before attenuating plate
Principal ray is distributed.
4. image reconstruction software according to claim 1, it is characterised in that this image reconstruction software is not using passing through attenuating plate
Three dimensional CT data is rebuild in preceding principal ray distribution.
5. attenuating plate according to claim 1, it is characterised in that this attenuating plate is uniform material.
6. the scattering composition from attenuating plate in every projected image is calculated according to claim 2, it is characterised in that scattering
Contribution matrix uses star schema.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110412645A (en) * | 2019-09-03 | 2019-11-05 | 张家港赛提菲克医疗器械有限公司 | A kind of novel scatter suppression flat panel detector |
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| CN101109718A (en) * | 2006-11-14 | 2008-01-23 | 北京国药恒瑞美联信息技术有限公司 | Virtual grid imaging method and system used for eliminating influence of scattered radiation |
| CN101987021A (en) * | 2010-12-06 | 2011-03-23 | 中国科学院深圳先进技术研究院 | Scattering correction method of CT system and CT system |
| CN104161536A (en) * | 2014-07-30 | 2014-11-26 | 西北工业大学 | Cone beam CT scatter correction method and device based on complementary gratings |
| CN104285240A (en) * | 2012-03-06 | 2015-01-14 | 皇家飞利浦有限公司 | Stereo X-ray tube based suppression of outside body high contrast objects |
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2017
- 2017-02-06 CN CN201710065172.0A patent/CN107049349A/en active Pending
Patent Citations (4)
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|---|---|---|---|---|
| CN101109718A (en) * | 2006-11-14 | 2008-01-23 | 北京国药恒瑞美联信息技术有限公司 | Virtual grid imaging method and system used for eliminating influence of scattered radiation |
| CN101987021A (en) * | 2010-12-06 | 2011-03-23 | 中国科学院深圳先进技术研究院 | Scattering correction method of CT system and CT system |
| CN104285240A (en) * | 2012-03-06 | 2015-01-14 | 皇家飞利浦有限公司 | Stereo X-ray tube based suppression of outside body high contrast objects |
| CN104161536A (en) * | 2014-07-30 | 2014-11-26 | 西北工业大学 | Cone beam CT scatter correction method and device based on complementary gratings |
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| CN110412645A (en) * | 2019-09-03 | 2019-11-05 | 张家港赛提菲克医疗器械有限公司 | A kind of novel scatter suppression flat panel detector |
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Effective date of registration: 20191218 Address after: 215631 room 410, building a, emerging industry education center, Zhangjiagang Free Trade Zone, Suzhou City, Jiangsu Province Applicant after: Zhangjiagang Medical Instrument Co.,Ltd. Address before: Huaiyin District of Ji'nan City, Shandong province 250117 Yan Ji Road, No. 440 Applicant before: Li Baosheng Applicant before: Liang Yueqiang |
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Application publication date: 20170818 |