CN104700377B - Obtain the method and apparatus that the beam hardening correction coefficient of beam hardening correction is carried out to computed tomography data - Google Patents
Obtain the method and apparatus that the beam hardening correction coefficient of beam hardening correction is carried out to computed tomography data Download PDFInfo
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Abstract
The present invention provides a kind of method and apparatus for obtaining and carrying out the beam hardening correction coefficient of beam hardening correction to computed tomography data.This method comprises the following steps: first against the object of specific dimensions, obtaining its original reconstructed image and initial sinusoids figure；Then error reduction sinogram is obtained after carrying out error reduction processing to original reconstructed image；Then it samples and calculates the average value of initial sinusoids figure and the average value of error reduction sinogram；Then it reduces sinogram according to error to optimize initial sinusoids figure, to determine the coefficient vector of the majorized function of the object for specific dimensions；Finally the coefficient vector of the majorized function of initial sinusoids figure is fitted, to obtain the beam hardening correction coefficient of the object for specific dimensions.
Description
Technical field
Present invention relates in general to computed tomography (Computed Tomography, CT), relate more particularly to obtain
Obtain the method and apparatus that the beam hardening correction coefficient of beam hardening correction is carried out to computed tomography data.
Background technique
Auxiliary diagnostic equipment includes magnetic resonance (Magnetic Resonance, MR) system, ultrasonic system, calculates X-ray
Tomographic system, positron emission tomography X (PET) system, core medical treatment and other kinds of imaging system.
For example, X-ray is used for the internal junction to patient body being carried out in CT x-ray imaging using CT system to patient
The feature of structure and region of interest (ROI) is imaged.The imaging is completed by CT scanner.When operation, photography target is swept
Initial data is retouched and collected, initial data is pre-processed, then reconstructed image, is improving image quality, after also carrying out
Reason.
Due to the spectral correlations of the ray attenuation performance of real-world object, will be observed in the case where the X-ray of polychrome
It is deviated to from the average energy for being pierced the X-ray that object transmits to higher energy value.Referred to as " beam is hard for the effect
Change ".In the reconstructed image of object by the gray value relative to theoretical case deviate it is observable it is linear, with spectrum phase
The ray attenuation of pass.This is especially by with reconstructed image caused by the high number of nuclear charges and highdensity material (such as bone)
In gray value offset --- or beam hardening virtual image --- make correct judgement of the image interference to image after reconstruct, and may
Cause the doctor checked to the misinterpretation of image in the worst case.
In pretreatment, carrying out beam hardening correction at least can partly exclude this virtual image.Some existing beams are hard
Change technology has shown improved uniformity for centering scanning, but for eccentric scanning, also shows band-like puppet on the image
Picture.
Summary of the invention
One embodiment of the present of invention provides a kind of obtain and carries out beam hardening correction to computed tomography data
The method of beam hardening correction coefficient.This method comprises the following steps: first against the object of specific dimensions, it is original heavy to obtain its
Composition picture and initial sinusoids figure；Then error reduction sinogram is obtained after carrying out error reduction processing to original reconstructed image；So
Post-sampling simultaneously calculates the average value of initial sinusoids figure and the average value of error reduction sinogram；Then sinogram is reduced according to error
Initial sinusoids figure is optimized, to determine the coefficient vector of the majorized function of the object for specific dimensions；Finally to original
The coefficient vector of the majorized function of sinogram is fitted, to obtain the beam hardening correction system of the object for specific dimensions
Number.
A kind of obtain of another embodiment of the invention penetrates computed tomography data progress beam hardening correction
The device of beam hardening correcting coefficient.The device includes acquisition device, error reduction device, equilibration device, optimizes device and fitting
Device.Wherein, acquisition device is directed to the object of specific dimensions, obtains its original reconstructed image and initial sinusoids figure；Error is reduced
Device obtains error reduction sinogram after carrying out error reduction processing to original reconstructed image；Equilibration device is sampled and is calculated original
The average value and error of sinogram reduce the average value of sinogram；Optimize device and sinogram is reduced to initial sinusoids figure according to error
It optimizes, to determine the coefficient vector of the majorized function of the object for specific dimensions；Device is fitted to initial sinusoids figure
The coefficient vector of majorized function is fitted, to obtain the beam hardening correction coefficient of the object for specific dimensions.
The method that a kind of pair of computed tomography data carries out beam hardening correction, which is characterized in that using such as right
It is required that the beam hardening correction coefficient that method described in any of 1-6 obtains is disconnected to the computer of other objects of specific dimensions
Layer scan data carries out beam hardening correction.
Of the invention provides the dress that a kind of pair of computed tomography data carries out beam hardening correction in one embodiment
It sets comprising as described above to obtain the beam hardening correction coefficient that beam hardening correction is carried out to computed tomography data
Device and correction computing device, the correction computing device using the beam hardening correction coefficient to the other of specific dimensions
The computed tomography data of object carries out beam hardening correction.
The fourth embodiment of the present invention provides a kind of ct apparatus comprising scanning means and processor.
Wherein scanning means is for being scanned to obtain initial data object using X-ray, to generate original reconstructed image；Place
Reason device, which can operate, is couple to the scanning means, and programmable to realize: for the object of specific dimensions, obtaining its original reconstructed
Image and initial sinusoids figure；Error reduction sinogram is obtained after carrying out error reduction processing to original reconstructed image；It samples and counts
The average value and error of calculating initial sinusoids figure reduce the average value of sinogram；According to error reduce sinogram to initial sinusoids figure into
Row optimization, to determine the coefficient vector of the majorized function of the object for specific dimensions；To the majorized function of initial sinusoids figure
Coefficient vector is fitted, to obtain the beam hardening correction coefficient of the object for specific dimensions.
The fifth embodiment of the present invention provides a kind of computer program product, including is stored in nonvolatile recording medium
On instruction, when the instruction executes in the processor, implement the embodiment of the present invention disclosed in method the step of.
The sixth embodiment of the present invention provides a kind of non-volatile memory medium, and which stores ought execute in the processor
When implement the embodiment of the present invention disclosed in method the step of instruction.
Detailed description of the invention
In order to thoroughly understand content of this disclosure, below with reference to the following description carried out in conjunction with attached drawing, in attached drawing
In:
Fig. 1 is the structural map according to the CT imaging system of the disclosure；
Fig. 2 is the schematic block diagram of system shown in Fig. 1；
Fig. 3 is the process flow diagram according to the beam hardening correction of the embodiment of the present disclosure；
Fig. 4 is the method schematic diagram according to embodiment of the present disclosure deckle circle view really；
Fig. 5 is an image using the water mould reconstructed after existing beam hardening correction；
Fig. 6 is another image using the water mould reconstructed after existing beam hardening correction；
Fig. 7 is using an image according to the water mould reconstructed after the beam hardening correction of the embodiment of the present disclosure；
Fig. 8 is using another image according to the water mould reconstructed after the beam hardening correction of the embodiment of the present disclosure；
Fig. 9 is an image using the head reconstructed after existing beam hardening correction；
Figure 10 is using an image according to the head mould reconstructed after the beam hardening correction of the embodiment of the present disclosure；
Figure 11 is the block diagram according to the device for obtaining beam hardening correction coefficient of the embodiment of the present disclosure.
Figure 12 is the block diagram according to the device for beam hardening correction of the embodiment of the present disclosure.
Specific embodiment
In the following detailed description, with reference to as part thereof of attached drawing, wherein being diagrammatically shown in which
The specific embodiment of the disclosure may be implemented.With these embodiments of enough datail descriptions, enable those skilled in the art
It realizes the disclosure, and should be understood that in the case where not departing from the range of each embodiment of the disclosure, embodiment can be carried out
Combination, or can use other embodiments and structure, logic and variation electrically can be made.Therefore, below detailed
Carefully description should not be taken as restrictive, and should be illustrative.The scope of the present invention be by appended claims and
What its equivalent limited.
With reference to Fig. 1 and 2, CT computer tomography (CT) imaging system 10 is shown as including scanning support 12.At one
In non-restrictive example, system 10 includes " third generation " CT scanner.Scanning support 12 has x-ray source 14, by 16 court of X-ray beam
Detector assembly 18 is incident upon in the opposite side of scanning support 12.Detector assembly 18 is by multiple detectors 20 and data acquisition
The formation of system (DAS) 32.The X-ray of projection of the multiple sensing of detector 20 across medical patient 22, wherein each detection
Device 20 generates analog electrical signal, indicates impinging x-ray beam and the thus intensity of the attenuated beam when it passes through patient 22.Inspection
Device 20 is surveyed to generally include for making to be used in the collimator of the received X-ray beam collimation of detector, adjacent to collimator by X-ray
Be converted to the scintillator (scintillator) of luminous energy and for receiving from the luminous energy of neighbouring scintillator and producing from it
The photodiode of raw electric signal.In general, X-ray is converted to luminous energy by each scintillator of scintillator arrays.Each scintillator
Luminous energy is discharged to the photodiode adjacent to it.Each photodiode detects luminous energy and generates corresponding electrical signal detection device
Each detector 20 of array 18 generates individual electric signal, which represents the strong of impact radiation beam (such as X-ray beam)
It spends and therefore can be used for estimating passing through the decaying that object or patient 22 are radiation beams in radiation beam.
During the scanning for obtaining X-ray projection data, scanning support 12 and the component installed thereon surround rotation center 24
Rotation.The rotation of scanning support 12 and the operation of x-ray source 14 can be managed by the control mechanism 26 of CT system 10.Control mechanism
26 include X-ray controller 28, provides electric power and timing signal to x-ray source 14 and gantry motor controller 30, the rack
The rotation speed of 30 gantry 12 of electric machine controller and position.Data acquisition system 32 in control mechanism 26 samples
Carry out the analogue data of self-detector 20 and converts this data to digital signals for subsequent processing.DAS32 output is included in specific
The data for projection collection for the attenuation measurement that gantry rotation angle (such as visual angle) obtains.It, can be single when scanning support 12 rotates
Multiple views are obtained during rotation.Single rotation is a complete 360 degree rotation of scanning support 12.Each view, which has, to be corresponded to
Visual angle, and the specific position on scanning support 12.
The image of reconstruct is applied as input to computer 36, which stores the image on high-capacity storage 38
In.
Computer 36 also receives order and sweep parameter from operator, operator's console through operator's console 40
40 have a some form of operator interface, for example, keyboard, mouse, voice activation controller or any other is suitable defeated
Enter equipment.Associated display 42 allows operator to observe from other data of computer 36 and the image of reconstruct.Operator
The order of offer and parameter can be used to provide to DAS32, X-ray controller 28 and gantry motor controller 30 from computer 36
Control signal and information.In addition, 36 station electric machine controller 44 of computer, controls the platform 46 of motorization to place patient 22
With scanning support 12.Especially, patient 22 is moved through the frame openings 48 of Fig. 1 by platform 46 in whole or in part.
In one embodiment, computer 36 includes equipment 50, for example, floppy disk drive, CD-ROM drive, DVD drive
Dynamic device, magneto-optic disk (MOD) equipment, or any other digital device of the network access device including such as ethernet device, are used
In from computer-readable medium 52 read instruction and/or data, the computer-readable medium 52 such as floppy disk, CD-ROM, DVD
Or such as another of network or internet digital source, and the digital device to be developed.In another embodiment, computer
36 execute the instruction being stored in firmware (not shown).In some configurations, computer 36 and/or image reconstructor 34 are programmed
To execute functions described herein.
Fig. 3 is the process flow diagram according to the beam hardening correction of the embodiment of the present disclosure.We use the water of all size
Mould calculates beam hardening correction coefficient.However the present invention is not limited to be applicable to only with water mould using any mould.It is various
The scan vision (Scan Field ofView, SFOV) for the various sizes that the water mould correspondence of size may scan.Assuming that we select
N kind water mould of different sizes is determined.
For the water mould of some size, firstly, obtaining original reconstructed image I in step 302origWith initial sinusoids figure
Iorigsin, original reconstructed image IorigWith initial sinusoids figure IorigsinIt can be to the data for projection of DAS32 in image reconstructor
It inputs, is also possible to from the acquisition of high-capacity storage 38, alternatively it is also possible to be from computer 36 after being reconstructed in 34
It obtains.
In step 304, orthographic projection is carried out to original reconstructed image, wherein need to carry out error reduction processing to projection value,
It obtains error and reduces sinogram IUnifsin.Error reduces the mode of processing such as, but not limited to: view is pressed, for each detection
The CT value for the pixel that X-ray detected by it is passed through is summed, then divided by the number of pixel, is obtained by device
The set of value be denoted as P ', the set for finding out corresponding projection value in initial sinusoids figure is denoted as P, using following equation meter
It calculates:
Wherein a is fixed coefficient, e.g. the value that defines to water mould of system, thus obtains error and reduces sinogram
IUnifsin。
Then, in step 306, boundary view is determined.In initial sinusoids figure IorigsinIn, it is logical that detector is found out from top to bottom
The view Orig_View1 that road intersects with water mould first, such as the 400th view, while another direction is found out from bottom to up
The view Orig_View2 that upper detector channel intersects with water mould first, such as the 200th view, as shown in figure 4, abscissa
View is represented, ordinate represents the channel of detector.A line is to start from above first to intersect with initial sinusoids figure above
Horizontal line, the corresponding abscissa of intersection point represents the 400th view, below a line be since following first with it is original just
The horizontal line of string figure intersection, the corresponding abscissa of intersection point represent the 200th view.Equally, sinogram I is reduced in errorUnifsin
In find out view corresponding with Orig_View1 (such as the 400th view) and Orig_View2 (such as the 200th view)
Unif_View1 (such as the 400th view) and Unif_View2 (such as the 200th view).
Next in step 308, the average sine value of boundary view is calculated.It needs to reduce just initial sinusoids figure and error
String figure calculates separately.It first has to sample, in initial sinusoids figure, by the positive throwing of two boundary views and its several views of front and back
Shadow value is averaged together.Such as Orig_View1, its 20 view in front and back is found out, to Orig_View2, before finding out it
20 views afterwards, the average value for calculating the orthographic projection value of this 42 views in total obtain average view Orig_Aver, subtract to error
Few sinogram is similarly operated, and for Unif_View1, is found out its 20 view in front and back and is also looked for for Unif_View2
Its 20 view in front and back out, the average value for calculating the orthographic projection value of this 42 views in total obtain average view Unif_Aver.Its
In, average view number can be used as parameter to understand, it depends on the size of noise, it can be set according to experiment,
It can be 10,20 or 40, but the number preferably taken in two sinograms is equal.
Then in step 310, initial sinusoids figure I is optimized as sample using average vieworigsin, so that initial sinusoids figure
IorigsinSinogram I is reduced close to error as far as possibleUnifsin.The mode of optimization is shown with reference to following formula:
Wherein, Q and Q ' is Orig_Aver and Unif_Aver respectively, we withAs ideal orthographic projection value,
Wherein a is fixed coefficient, and the e.g. value that defines to water mould of system passes through one group of basic function B as targetj(j=1,
2 ... n, n are the number of used basic function, and artificially determined by experiment) excellent to original orthographic projection value P progress
Change, i=1,2 ... m, m be customized top step number, the step for purpose be determining majorized function coefficient vector b.
It for different size of water mould, needs to repeat step 302-310, so that it is determined that the water mould of different sizes for N kind
N number of coefficient vector b.
In step 312, it is fitted against N number of coefficient vector b, to obtain beam hardening correction coefficient c.Fitting for example may be used
To use formula as follows:
Wherein h=1,2 ... h, h are customized top step number, can be same or different with m.
Hereafter, so that it may using beam hardening correction coefficient vector c to the computerized tomography of various sizes of other objects
Scan data carries out beam hardening correction.The formula mentioned in the formula of correction and above-mentioned fitting is similar, the projection after correction
Data PnewAre as follows:
It should be noted that as a system, it is necessary to have the objects to all size to carry out beam hardening correction
Ability.But from the point of view of single object, from step 302 to 312, only carry out one time, so that it may obtain penetrating for the single object
Beam hardening correcting coefficient.
Fig. 5 is using an image of the water mould reconstructed after existing beam hardening correction, this is scanned in eccentric 5.6mm
Obtained result, it can be seen that there are a black circles between water mould and boundary, this is undesirable appearance.Fig. 6 is using existing
Another image of the water mould reconstructed after some beam hardening corrections, this be eccentric 5cm scan as a result, can see
Out, with the increase of eccentric distance, problem is more serious, there are a wider band artifacts in the picture, this is obviously also
Undesirable appearance.Fig. 7 is using an image according to the water mould reconstructed after the beam hardening correction of the embodiment of the present disclosure, together
Sample scans to obtain in eccentric 5.6mm, and black circle obviously disappears.Fig. 8 is after using according to the beam hardening correction of the embodiment of the present disclosure
Another image of the water mould of reconstruct, this is to scan to obtain in eccentric 5cm, and band artifacts disappear, and obtains relatively uniform image,
This be it is desired, meet actual image.Refer now to the result that patients head is imaged in practice.Fig. 9 is to adopt
With an image of the head reconstructed after existing beam hardening correction, it is to be obtained in 5cm eccentric scanning, can sees
Out, there are band artifacts for the image in skull, this will affect the diagnosis of doctor.Figure 10 is using penetrating according to the embodiment of the present disclosure
One image of the head mould reconstructed after beam hardening correcting, also in being obtained in the case of 5cm eccentric scanning, it can be seen that skull
The band artifacts problem of interior image is relieved.In fact, using method of the invention, it can eliminate or alleviate slightly
" black circle " issuable when eccentric scanning, and the issuable band artifacts in apparent eccentric scanning.
Figure 11 is the block diagram according to the device for obtaining beam hardening correction coefficient of the embodiment of the present disclosure.Wherein it is used for
The device 1100 for obtaining beam hardening correction coefficient includes: acquisition device 1101, error reduction device 1102, equilibration device
1103, optimize device 1104 and fitting device 1105.Wherein acquisition device 1101 at least reduces device 1102, average dress with error
Set 1103 with optimization device 1104 mutually couple, error reduce device 1102 at least with equilibration device 1103 and optimize 1104 phase of device
Coupling, optimization device 1104 also at least are wanted to couple with equilibration device 1103 and fitting device 1105.In Figure 11, for the side of diagram
Just, each device is mutually coupled.It is noted, however, that each device can be with any other connection type phase coupling
It connects, as long as being able to achieve each function as described below.Also, the function of multiple devices may be incorporated in a device and realize,
And each device can also be further divided into more devices to realize, also, the quantity of the same device in systems
1 can be greater than.
Acquisition device 1101 is mainly used for obtaining original reconstructed image and initial sinusoids figure.It is main that error reduces device 1102
For obtaining the sinogram of relative ideal.Equilibration device 1103 is mainly used for some views near the boundary view for calculating water mould
Average orthographic projection value.Optimization device 1104 is mainly used for result and initial sinusoids figure according to equilibration device 1103 come calculation optimization
Basic function coefficient.Fitting device 1105 is mainly used for being fitted beam hardening correction based on optimization device more than 1104 times results
Coefficient.
Assuming that we have selected N kind water mould of different sizes.For the water mould of some size, firstly, acquisition device
1101 obtain original reconstructed image IorigWith initial sinusoids figure Iorigsin, original reconstructed image IorigWith initial sinusoids figure
IorigsinIt can be and input after the data for projection of DAS32 is reconstructed in image reconstructor 34, be also possible to from magnanimity
What storage device 38 obtained, alternatively it is also possible to be obtained from computer 36.
Then error reduces device 1102 and carries out orthographic projection to original reconstructed image, wherein needing to carry out error to projection value
Reduction processing obtains error and reduces sinogram IUnifsin.Error reduces the mode of processing such as, but not limited to: view is pressed, for
Each detector sums the CT value for the pixel that the X-ray detected by it is passed through, then divided by of pixel
Number, the set of obtained value are denoted as P ', and the set for finding out corresponding projection value in initial sinusoids figure is denoted as P, and use is following
Formula calculates:
Wherein a is fixed coefficient, e.g. the value that defines to water mould of system, thus obtains error and reduces sinogram
IUnifsin。
Then, equilibration device 1103 determines boundary view by its boundary determining device 11031.In initial sinusoids figure
IorirsinIn, the view Orig_View1 that detector channel intersects with water mould first, such as the 400th view are found out from top to bottom
Figure, while the view Orig_View2 that detector channel intersects with water mould first on another direction, example are found out from bottom to up
Such as the 200th view, as shown in figure 4, abscissa represents view, ordinate represents the channel of detector.Above a line be from
First horizontal line intersected with initial sinusoids figure started above, the corresponding abscissa of intersection point represent the 400th view, below one
Bar line is first horizontal line intersected with initial sinusoids figure since following, and the corresponding abscissa of intersection point represents the 200th view
Figure.Equally, sinogram I is reduced in errorUnifsinIn find out with Orig_View1 (such as the 400th view) and Orig_View2
(such as the 200th view) corresponding view Unif_View1 (such as the 400th view) and Unif_View2 (such as the 200th
A view).
Following equilibration device 1103 calculates the average sine value of boundary view by its average computation device 11032.It needs
Sinogram is reduced to initial sinusoids figure and error to calculate separately.It first has to sample, in initial sinusoids figure, two boundaries is regarded
The orthographic projection value of figure and its several views of front and back is averaged together.Such as Orig_View1, its front and back 20 is found out
View finds out its 20 view in front and back to Orig_View2, and the average value for calculating the orthographic projection value of this 42 views in total obtains
Average view Orig_Aver reduces sinogram to error and is similarly operated, and for Unif_View1, finds out its front and back 20
A view also finds out its 20 view in front and back for Unif_View2, calculates the orthographic projection value of this 42 views in total and is averaged
Value obtains average view Unif_Aver.Wherein, average view number can be used as parameter to understand, it depends on noise
Size, can be set according to experiment, can be 10,20 or 40, but preferably be taken in two sinograms
Number is equal.
Then optimization device 1104 optimizes initial sinusoids figure I as sample using average vieworigsin, so that initial sinusoids figure
IorigsinSinogram I is reduced close to error as far as possibleUnifsin.The mode of optimization is shown with reference to following formula:
Wherein, Q and Q ' is Orig_Aver and Unif_Aver respectively, we withAs ideal orthographic projection value,
Wherein a is fixed coefficient, and the e.g. value that defines to water mould of system passes through one group of basic function B as targetj(j=1,
2 ... n, n are the number of used basic function, and artificially determined by experiment) excellent to original orthographic projection value P progress
Change, i=1,2 ... m, m are customized top step number.The step for purpose be determining majorized function coefficient vector b.
It for different size of water mould, needs to repeat operation above, so that it is determined that for N kind water mould of different sizes
N number of coefficient vector b.
Fitting device 1105 is fitted this N number of coefficient vector b, to obtain beam hardening correction coefficient c.Fitting is for example
Formula as follows can be used:
Wherein h=1,2 ... h, h are that customized highest terminates, can be identical or different with m.
Hereafter, so that it may the computed tomography using beam hardening correction coefficient c to various sizes of other objects
Data carry out beam hardening correction.
Figure 12 is according to the block diagram of the device for beam hardening correction of the embodiment of the present disclosure, wherein being used for beam hardening
The device of correction includes the device 1100 for being used to obtain beam hardening correction coefficient and the correction being attached thereto as shown in figure 11
Computing device 1202.After the device 1100 for obtaining beam hardening correction coefficient obtains correction coefficient vector c, correction meter
Device 1202 is calculated data for projection P is corrected to obtain P using coefficient vector cnew:
Herein, term "a" or "an" includes that odd number is each or more than one a plurality of.Term "or" is used for
Refer to being not excluded for or (nonexclusive or), unless otherwise stated.
Also as it is used herein, word " reconstructed image " be not intended to exclude wherein generate indicate image data without
Generate the embodiment of the disclosure of visual image.Therefore, term " image " used herein broadly refers to visual image and table
Show the data of visual image.However, many embodiments generate (or being configured as generating) at least one visual image.
The operating environment of the disclosure is described relative to 16 layers of X-ray computed tomography (CT) system.However, this field
Technical staff will be appreciated that, the system that the disclosure is equally applicable to multi-layer configuration, and suitable for moving or " trembling during operation
It is dynamic " system of the ability of focus.Moreover, the disclosure will be described relative to the detection of X-ray and conversion.However, this field skill
Art personnel further to be appreciated that the disclosure is equally applicable to the detection and conversion of other high frequency electromagnetic energies.Although specific
Embodiment is with reference to third generation CT system, but method described herein applies equally to forth generation CT system (such as with rotation
Turn the silent oscillation detector of x-ray source) and the 5th generation CT system (such as silent oscillation detector and x-ray source).Additionally, it is contemplated that this
Disclosed benefit extends to other imaging patterns in addition to CT, such as MRI, SPECT and PET.
A part that various embodiments or its component can be used as computer system is realized.The computer system may include meter
Calculation machine, input equipment, display unit and for example for accessing the interface of internet.Microprocessor may be coupled to communication bus.
Computer can also include memory.The memory may include random access memory (RAM) and read-only memory (ROM).
The computer system can also include storage equipment, can make hard disk drive or such as floppy disk drive, CD drive
Deng movable memory equipment.The storage equipment can also be used in Load Computer program or other instructions to computer system
In other similar device.
In the various embodiments of the disclosure, creating the method described herein for obtaining beam hardening correction coefficient be can handle
The form of machine embodies.The typical case of processor includes general purpose computer, the microprocessor of programming, digital signal processor
(DSP), microcontroller, peripheral integrated circuit element, and the step of can be realized method described herein other equipment or set
Standby arrangement.
As it is used herein, term " computer " is not limited to be referred to as the integrated electricity of those of computer in the art
Road, but may include any based on processor or based on untreated system, including use microcontroller, reduced instruction current collection
Road (RISC), specific integrated circuit (ASIC), logic circuit and any other circuit or the place for being able to carry out function described herein
The system for managing device.Above-mentioned example is exemplary, and is not intended to the definition of limiting term " computer " in any way
And/or meaning.Such as computer, processor, microcontroller, microcomputer, programmable logic controller (PLC), specific integrated circuit
It is used interchangeably with these terms of other programmable circuits etc herein.
Processing mechanism executes one group of instruction (for example, the corresponding described method and step), and it is multiple which is stored in a work
In memory element (also referred to computer usable medium).The form of memory element can be database or be present in processor
Physical memory element.Memory element can also hold data or other information as required.Physical storage can be, such as but
It is not limited to: electronics, magnetic, optical, electromagnetic, infrared or semiconductor system, device, equipment or propagation medium.Physical storage has more
Body example includes but is not limited to lower example: random access memory (RAM), read-only memory (ROM), the read-only storage of erasable programmable
Device (EPROM or flash memory), hard disk drive (HDD) and compact disc-ROM (CDROM).Above-mentioned type of memory is only demonstrated
Property, therefore the type of the memory for can be used for storing computer program is not restrictive.
Described instruction group may include various orders, which indicates that processor executes specific operation, such as the disclosure
The process of various embodiments.The form of instruction group can be software program.Software can be such as system software or application software
Various forms.In addition, the form of software can be single program, program module or a part of program mould in larger program
The set of block.Software further includes the modeled programming using Object-Oriented Programming as form.Input data is handled by processor
It can be the order corresponding to user, or corresponding to previously processed as a result, or asking corresponding to what is made by another processor
It asks.
The various embodiments of the disclosure, the method for obtaining beam hardening correction coefficient can be real by software, hardware or combinations thereof
It is existing.Such as it can the various embodiments implemented in software by the disclosure by using standard programming language (such as C, C++, Java etc.)
The method of offer.As it is used herein, term " software " and " firmware " can be interchanged, and including use stored in memory
In any computer program performed by computer.
In addition, though method described here is retouched in the medical scene of X-ray computed tomography (CT) system
It states, it is contemplated that these benefits also help magnetic resonance (MR) system, ultrasonic system, positron emission x-ray tomography
(PET) system of photography, core medical treatment and other kinds of imaging system.It can be operated for certain organs or structure, this packet
Include biologic-organ, such as brain, stomach, heart, lung or liver；Biological structure, such as diaphragm, the wall of the chest, thoracic cavity, rib cage, spine, breastbone
Or pelvis；Tumour or damage or wound (sore), such as compression fracture.
Claims (16)
1. a kind of obtain the method for carrying out the beam hardening correction coefficient of beam hardening correction to computed tomography data, packet
Include step:
For the object of specific dimensions, its original reconstructed image and initial sinusoids figure are obtained；
Original reconstructed image is projected, and the initial sinusoids figure is carried out at error reduction based on the average value of projection value
Error is obtained after reason reduces sinogram；
It samples and calculates the average value of initial sinusoids figure and the average value of error reduction sinogram；
Sinogram is reduced according to error to optimize initial sinusoids figure so that the initial sinusoids figure and the error are reduced just
Error between string figure is minimum, to determine the coefficient vector of the majorized function of the object for specific dimensions；
The coefficient vector of the majorized function of initial sinusoids figure is fitted, it is hard to obtain being directed to the beam of object of specific dimensions
Change correction coefficient.
2. as described in claim 1 obtain the beam hardening correction for carrying out beam hardening correction to computed tomography data
The method of coefficient, which is characterized in that a variety of various sizes of objects can be directed to, the coefficient vector of majorized function is calculated separately,
And the fitting is fitted to the coefficient vector of all majorized functions.
3. as described in claim 1 obtain the beam hardening correction for carrying out beam hardening correction to computed tomography data
The method of coefficient, which is characterized in that the error reduction processing further comprises step:
The CT value for the pixel that the X-ray detected by it is passed through is summed, so by view for each detector
Afterwards divided by the number of the pixel passed through, the set P ' that is worth；
The set P for finding out corresponding projection value in initial sinusoids figure, is calculated using following equation:Obtain error
Sinogram is reduced, wherein a is coefficient of the system to the object definition.
4. as described in claim 1 obtain the beam hardening correction for carrying out beam hardening correction to computed tomography data
The method of coefficient, which is characterized in that the sampling simultaneously calculates the average value of initial sinusoids figure and being averaged for error reduction sinogram
Value further comprises step:
The boundary view and its neighbouring view for determining initial sinusoids figure, as the first sampling view, and determine that error is reduced just
The boundary view of string figure and its neighbouring view, as the second sampling view；
The average value of the first sampling view and the second sampling view is calculated separately, average value and error as initial sinusoids figure subtract
The average value of few sinogram.
5. as described in claim 1 obtain the beam hardening correction for carrying out beam hardening correction to computed tomography data
The method of coefficient, which is characterized in that described optimized according to error reduction sinogram to initial sinusoids figure further comprises step
It is rapid:
Calculating makesAs close possible to zero coefficient to
B is measured, wherein Q and Q ' is the average value of initial sinusoids figure and the average value of error reduction sinogram respectively, and Bj is base letter used
Number, j=1,2 ... n, n are the number of used basic function, and i=1,2 ..., m, m are the top step number of definition.
6. as claimed in claim 5 obtain the beam hardening correction for carrying out beam hardening correction to computed tomography data
The method of coefficient, which is characterized in that the coefficient vector of the majorized function to initial sinusoids figure, which is fitted, further comprises:
According toCalculate beam hardening correction coefficient to
C is measured, wherein k=1,2 ... h, h are the top step number of definition.
7. a kind of obtain the device for carrying out the beam hardening correction coefficient of beam hardening correction to computed tomography data, packet
It includes:
Acquisition device is directed to the object of specific dimensions, obtains its original reconstructed image and initial sinusoids figure；
Error reduces device, projects to original reconstructed image, and based on the average value of projection value to the initial sinusoids
Figure obtains error reduction sinogram after carrying out error reduction processing；
Equilibration device samples and calculates the average value of initial sinusoids figure and the average value of error reduction sinogram；
Optimize device, according to error reduce sinogram initial sinusoids figure is optimized so that the initial sinusoids figure with it is described
Error reduces the error minimum between sinogram, to determine the coefficient vector of the majorized function of the object for specific dimensions；
It is fitted device, the coefficient vector of the majorized function of initial sinusoids figure is fitted, to obtain for specific dimensions
The beam hardening correction coefficient of object.
8. as claimed in claim 7 obtain the beam hardening correction for carrying out beam hardening correction to computed tomography data
The device of coefficient, which is characterized in that a variety of various sizes of objects can be directed to, the coefficient vector of majorized function is calculated separately,
And the fitting device is fitted to the coefficient vector of all majorized functions.
9. as claimed in claim 7 obtain the beam hardening correction for carrying out beam hardening correction to computed tomography data
The device of coefficient, which is characterized in that the error reduces device and is further used for:
The CT value for the pixel that the X-ray detected by it is passed through is summed, so by view for each detector
Afterwards divided by the number of the pixel passed through, the set P ' that is worth；
The set P for finding out corresponding projection value in initial sinusoids figure, is calculated using following equation:Obtain error
Sinogram is reduced, wherein a is coefficient of the system to the object definition.
10. as claimed in claim 7 obtain the beam hardening school for carrying out beam hardening correction to computed tomography data
The device of positive coefficient, which is characterized in that the equilibration device is further used for:
The boundary view and its neighbouring view for determining initial sinusoids figure, as the first sampling view, and determine that error is reduced just
The boundary view of string figure and its neighbouring view, as the second sampling view；
The average value of the first sampling view and the second sampling view is calculated separately, average value and error as initial sinusoids figure subtract
The average value of few sinogram.
11. as claimed in claim 7 obtain the beam hardening school for carrying out beam hardening correction to computed tomography data
The device of positive coefficient, which is characterized in that optimization device is further used for:
Calculating makesAs close possible to zero coefficient to
B is measured, wherein Q and Q ' is the average value of initial sinusoids figure and the average value of error reduction sinogram, B respectivelyjIt is base letter used
Number, j=1,2 ... n, n are the number of used basic function, and i=1,2 ..., m, m are the top step number of definition.
12. as claimed in claim 11 obtain the beam hardening school for carrying out beam hardening correction to computed tomography data
The device of positive coefficient, which is characterized in that fitting device is further used for:
According toCalculate beam hardening correction coefficient to
C is measured, wherein k=1,2 ... h, h are the top step number of definition.
13. the method that a kind of pair of computed tomography data carries out beam hardening correction, which is characterized in that wanted using such as right
Computerized tomography of the beam hardening correction coefficient for asking method described in any of 1-6 to obtain to other objects of specific dimensions
Scan data carries out beam hardening correction.
14. the device that a kind of pair of computed tomography data carries out beam hardening correction characterized by comprising
Acquisition as described in any of claim 7-12 carries out beam hardening correction to computed tomography data and penetrates
The device of beam hardening correcting coefficient；And
Correct computing device, the computed tomography using the beam hardening correction coefficient to other objects of specific dimensions
Data carry out beam hardening correction.
15. a kind of ct apparatus, comprising:
Scanning means, for being scanned object to obtain initial data using X-ray, to generate original reconstructed image；
Processor can operate and be couple to the scanning means, and programmable to realize:
For the object of specific dimensions, its original reconstructed image and initial sinusoids figure are obtained；
Original reconstructed image is projected, and the initial sinusoids figure is carried out at error reduction based on the average value of projection value
Error is obtained after reason reduces sinogram；
It samples and calculates the average value of initial sinusoids figure and the average value of error reduction sinogram；
Sinogram is reduced according to error to optimize initial sinusoids figure so that the initial sinusoids figure and the error are reduced just
Error between string figure is minimum, to determine the coefficient vector of the majorized function of the object for specific dimensions；
The coefficient vector of the majorized function of initial sinusoids figure is fitted, it is hard to obtain being directed to the beam of object of specific dimensions
Change correction coefficient.
16. a kind of non-volatile memory medium, which stores implement when executing in the processor according to as appointed in claim 1-6
The instruction of method described in one.
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| JP2014245446A JP6411877B2 (en) | 2013-12-06 | 2014-12-04 | Method and device for obtaining beam hardening correction coefficients for performing beam hardening correction on computed tomography data |
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| CN117315071B (en) * | 2023-11-30 | 2024-03-15 | 赛诺威盛科技(北京)股份有限公司 | Defocus artifact correction method, device and computer readable medium |
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| CN1775176A (en) * | 2004-11-16 | 2006-05-24 | 北京航空航天大学 | CT beam sclerosis correcting method based on original projection sine diagram |
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| JP3204701B2 (en) * | 1991-11-14 | 2001-09-04 | ジーイー横河メディカルシステム株式会社 | Beam hardening correction method |
| JP3414471B2 (en) * | 1994-01-24 | 2003-06-09 | 株式会社東芝 | X-ray CT system |
| JP3950811B2 (en) * | 2003-04-17 | 2007-08-01 | ジーイー・メディカル・システムズ・グローバル・テクノロジー・カンパニー・エルエルシー | X-ray CT apparatus and beam hardening post-processing method |
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| CN1775176A (en) * | 2004-11-16 | 2006-05-24 | 北京航空航天大学 | CT beam sclerosis correcting method based on original projection sine diagram |
| CN102609908A (en) * | 2012-01-13 | 2012-07-25 | 中国人民解放军信息工程大学 | Base image TV model based CT (Computed Tomography) beam hardening correcting method |
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