CN106154306B - A method of detection CT photon counting-type detector accuracy - Google Patents
A method of detection CT photon counting-type detector accuracy Download PDFInfo
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Abstract
The present invention provides a kind of method for detecting CT photon counting-type detector accuracy, is related to technical field of medical equipment.CT scan system is built using x-ray bulb, triangular prism shaped bi-material layers die body and ordinary flat detector, scanning obtains first group of data；Remove die body, sky is swept to obtain second group of data；Based on decaying transmission principle, system of linear equations is constructed according to two groups of data, solution obtains the discrete power spectrum of x-ray first；Ordinary flat detector is replaced with photon counting-type detector to be measured, removes die body, sky is swept to obtain the discrete power spectrum of x-ray second；Two discrete power spectrums are compared, if error is in a certain range, photon counting-type detector accuracy reaches requirement.The present invention is by being arranged triangular prism shaped bi-material layers die body, based on decaying transmission principle, carries out spectral measurement using two kinds of attenuating materials, the pathosis of system of linear equations to be solved is effectively improved in root, die body structure is simple, and scanning times are few, effectively avoid waste of resource, high reliablity.
Description
Technical field：
The present invention relates to technical field of medical equipment more particularly to a kind of detection CT photon counting-type detector accuracys
Method.
Background technique：
Typical CT equipment mainly includes three parts, i.e. sweep test, examination couch and operating console.Wherein, CT
Sweep test is mainly made of x-ray bulb, high pressure generator, detector, data collection system, control computer etc..X-ray bulb
X-ray beam is issued to be scanned selected level, and detector will then be collected into x-ray signal and be changed into electric signal, through mould/
Number (A/D) converter is converted into digital signal, computer stored and processing is inputted, to obtain the CT of the level constituent parts volume
Value, and it is arranged in character matrix.Detector is the important component in CT system, traditional charge integration type X-ray detection
Device, the ability without identification energy, and photon counting detector can replace photon energy to deposit with photon number, have
High energy resolution, and can be divided into the X-ray energy spectrum mixed originally different in such a way that energy threshold is set
Energy section, then the photonic particles number in each energy section respectively is counted, this makes it possible to obtain the X under different-energy section
The attenuation of ray photons energy.
The accuracy of photon counting-type detector is extremely important, if detector is not accurate enough to the measurement of attenuation coefficient,
Small error in measurement may be mistaken as the variation of signal, directly affect image quality and subsequent processing.Generally set in CT
Before standby factory, production firm can all carry out accuracy detection to photon counting-type detector, buyer be also required to its accuracy into
Performing check assesses influence of the detector to the CT performance being imaged, to carry out subsequent correction and energy-threshold calibration.So
Having the method for an economical and practical and easy to operate inspection photon counting-type detector accuracy is necessary.
The X-ray energy spectrum of CT imaging system is distributed in dual intensity spectrum CT imaging, the scattering of the hardening correcting of CT image, CT image
The various fields such as correction, the quantitative analysis of CT image play important role.Due to the X-ray that X-ray machine generates in CT system
Stream it is larger by force, directly measured using x-ray spectrometer relatively difficult, therefore there has been proposed a variety of round-about ways to estimate
The X-ray energy spectrum of CT system is distributed.Currently, there are many methods to obtain the distribution of accurate X-ray energy spectrum, as experience with
Semiempirical model, Compton scattering and decaying transmission beam method etc..Wherein, energy range is relatively wide, counts with adapting to for decaying transmission beam method
The advantages that relatively easy is calculated, in the X-ray energy spectrum measurement especially sigmatron energy spectrum reconstruction of MeV energy, is obtained more
Concern and research.X-ray energy spectrum measurement method based on decaying transmission principle is broadly divided into two steps：The first step is to obtain X
For ray with the direct puncture transmittance graph of attenuating material thickness change, second step is then associated using transmissivity and X-ray energy spectrum
Equation carries out spectrum unscrambling.The existing technology for rebuilding X-ray energy spectrum using decaying transmission principle is all based on a kind of attenuating material, if
The scanning die body shape of meter has wedge shape and section centrum etc..The equation that the identical point of this design is has the morbid state of height
Property, then want by solving equation to obtain correct discrete energy spectrum be a problem, the prior art is all to find emphatically more
The method, such as iterative perturbation method etc. of effective solution ill-condition equation, in the hope of more correct discrete energy spectrum.
Summary of the invention：
In view of the drawbacks of the prior art, the present invention provides a kind of method for detecting CT photon counting-type detector accuracy,
By the way that triangular prism shaped bi-material layers die body is arranged, based on decaying transmission principle, spectral measurement is carried out using two kinds of attenuating materials, indirectly
The accuracy for detecting photon counting-type detector, is effectively improved the pathosis of system of linear equations to be solved, by normal in root
The linear equation derivation algorithm seen acquires relatively accurate discrete energy spectrum；Die body structure is simple, easy to operate, scanning times
It is few, waste of resource is effectively avoided, the high reliablity of spectral measurement provides for the subsequent correction work of photon counting-type detector
Strong foundation is more advantageous to and the performance test to photon counting-type detector is promoted to work.
The present invention provides a kind of method for detecting CT photon counting-type detector accuracy, includes the following steps：
Step 1 builds the first CT scan system, including light source, die body and detector, scans to obtain first group to die body and sweep
Data are retouched, are specifically included：
Step 101, setting light source are X-ray bulb；
Step 102, die body are set between optical light source and detector, and die body is set as triangular prism shaped bi-material layers die body, triangular prism
Upper bottom surface be congruence isosceles obtuse triangle, the rectangular section where high on the bottom edge of the above bottom surface is boundary, will
Triangular prism die body is divided into the big wedge-like portions such as two, and side wedge shape is attenuation of the first kind material, and other side wedge shape is second
Kind attenuating material；Rectangle sides in triangular prism where the bottom edge of isosceles obtuse triangle are as the plane of incidence, other two rectangle
Side is respectively the first exit facet and the second exit facet, and the plane of incidence face light source is placed；
Step 103, setting detector are ordinary flat charge integration type X-ray detector；
Step 104 scans triangular prism shaped bi-material layers die body using the first CT scan system, and starting X-ray bulb transmitting X is penetrated
Line, the X-ray of sending are injected from the plane of incidence, also cross two kinds of attenuating materials of bi-material layers die body, from the first exit facet and the
Two exit facets project；
Step 105, detector receive the X-ray signal after die body, obtain first group of scan data；
Step 2 removes die body in the first CT scan system, and other parameters and condition are constant, forms the second CT scan system
System starts light source, carries out sky and sweeps, obtains second group of scan data；
Step 3 is based on decaying transmission principle, carries out X-ray energy spectrum measurement, the first group of scan data obtained according to scanning
X-ray energy spectrum is solved with second group of scan data, obtains the discrete power spectrum of X-ray first；
Step 4 replaces the spy of the ordinary flat in the second CT scan system with CT photon counting-type detector to be measured
Device is surveyed, the setting of light source is constant, carries out sky and sweeps, obtains the discrete power spectrum of X-ray second；
Step 5 compares the discrete power spectrum of X-ray second and the discrete power spectrum of X-ray first, if the two is consistent or misses
Difference is within the scope of predictive error, then CT photon counting-type detector accuracy reaches requirement, and otherwise, accuracy is insufficient.
Further, in step 1, the size of die body and specific location between optical light source and detector according to light source with
The size for the angle and detector working face that distance, the X-ray of detector cover is arranged, the X-ray covering for emitting light source
Entire die body, and received by detector working face.
Further, the obtuse angle angle of the isosceles obtuse triangle of triangular prism shaped bi-material layers die body is covered according to X-ray
The distance between angle, light source and die body and attenuating material thickness setting, should guarantee that X-ray energy covers entire die body,
Guarantee that the thickness of die body is unlikely to keep number of photons decaying excessively serious and influence Effect on Detecting again.
Further, in step 3, based on decaying transmission principle, the method for carrying out X-ray energy spectrum measurement is specially：
It is saturating to obtain X-ray for step 301, the first group of scan data and second group of scan data obtained using twice sweep
Rate is penetrated with the system of linear equations of the thickness change of attenuating material, the formula of linear equation is：
In formula, xS, i(i=1 ..., m, s=1,2) indicates that i-th kind of thickness of s kind attenuating material, s=1 are expressed as first
Kind of attenuating material, s=2 are expressed as attenuation of the second kind material, and m indicates the thickness total number of s kind attenuating material, the value of m by
The number of the search coverage divided on detector determines；T(xS, i) indicate discretization X-ray transmission rate, T (xS, i)=I
(xS, i)/I(0s), I (xS, i) it is first group of scan data, it indicates by with a thickness of xS, iAttenuating material after detector receive
Signal strength, I (0s) it is second group of scan data, indicate the empty detector received signal strength without decaying swept；Ej(j
=1 ..., n) indicate that discrete photon energy, j indicate the number of different discrete photon energy, n indicates total of discrete photon energy
Number, for the positive integer greater than 1, the value of n according to practical operation condition and guarantees that the number of equation is greater than etc. in actual operation
It is set in n, E1=Emin, indicate photon energy lower limit, En=Emax, indicate the photon energy upper limit；F(Ej) indicate discrete power spectrum
Value；μs(Ej) indicate under each conventional attenuating material s mass attentuation coefficient；ρsIndicate the density of attenuating material s；ΔE
Indicate conventional interval width, Δ E=(Emax-Emin)/(n-1)；
System of linear equations in step 302, solution procedure 301 is rebuild X-ray energy spectrum, is solved using EM algorithm
Linear equation obtains X-ray the first discrete energy spectrum F (Ej)。
Further, attenuation of the first kind material is iron, and attenuation of the second kind material is aluminium.
As shown from the above technical solution, the beneficial effects of the present invention are：A kind of detection CT photon meter provided by the invention
The method of number type detector accuracy goes to detect the poly-talented spy of photon indirectly using the spectral measurement method based on decaying transmission principle
The method for surveying device accuracy, by the way that triangular prism shaped bi-material layers die body is arranged, is based on two on the basis of original attenuation transmission principle
Kind of attenuating material carries out spectral measurement, effectively mitigates the pathosis of system of linear equations to be solved in root, using common
Linear equation derivation algorithm can acquire relatively accurate discrete energy spectrum, have high reliability.Trigone in the present invention
Cylindricality bi-material layers die body, die body structure is simple, can place two kinds of materials simultaneously and not have an impact mutually, easy to operate, sweeps
It retouches that number is few, can be obtained by the attenuation data of two kinds of materials by single pass, not only improve the pathosis of equation, also save
Resource has been saved, effectively strong foundation can be provided for the subsequent correction work of photon counting-type detector, be more advantageous to propulsion
Performance test work to photon counting-type detector.
Detailed description of the invention：
Fig. 1 is method flow diagram provided in an embodiment of the present invention；
Fig. 2 is die body structure and its plane of incidence schematic diagram in the embodiment of the present invention；
Fig. 3 is the exit facet schematic diagram of die body in the embodiment of the present invention；
Fig. 4 is the structural schematic diagram of the first CT scan system in the embodiment of the present invention.
In figure：1, light source；2, die body；201, attenuation of the first kind material；202, attenuation of the second kind material；203, the plane of incidence；
204, the first exit facet；205, the second exit facet；3, detector.
Specific embodiment：
With reference to the accompanying drawings and examples, specific embodiments of the present invention will be described in further detail.Implement below
Example is not intended to limit the scope of the invention for illustrating the present invention.
As shown in Figure 1, the method for the present embodiment is as described below.
Step 1 builds the first CT scan system, including light source 1, die body 2 and detector 3, as shown in figure 4, sweeping to die body 2
It retouches to obtain first group of scan data I (xS, i), the specific method is as follows.
Step 101, setting light source 1 are X-ray bulb, and in the present embodiment, light source 1 is arranged a 10kev~130kev's
Discrete power spectrum；
Step 102, die body 2 are set between light source 1 and detector 3, and die body 2 is set as triangular prism shaped bi-material layers die body, such as
Shown in Fig. 2, the upper bottom surface of triangular prism is the isosceles obtuse triangle of congruence, the square at the high place on the bottom edge of the above bottom surface
Shape section is boundary, triangular prism die body is divided into the big wedge-like portions such as two, side wedge shape is attenuation of the first kind material iron
201, other side wedge shape is attenuation of the second kind materials of aluminum 202；
Rectangle sides in triangular prism where the bottom edge of isosceles obtuse triangle are as the plane of incidence 203, other two rectangle
Side is respectively the first exit facet 204 and the second exit facet 205, as shown in figure 3,203 face light source 1 of the plane of incidence is placed；This reality
Apply in example, the rectangle that the rectangle plane of incidence 203 of die body 2 is 30 × 60 centimetres, between two bottom surfaces with a thickness of 1 centimetre；
The reason of selecting aluminium and both attenuating materials of iron for：First is that aluminium and iron are relatively common, be easy preparation, second is that aluminium and
The decaying gender gap of iron is larger, and aluminium Decay Rate is relatively mild, and iron Decay Rate is stronger, such that the order of the linear equation arrived
Increase, conditional number reduces, to effectively mitigate the pathosis of equation, obtains more accurately solving；In specific implementation, it can also adopt
With the attenuating material of three kinds or more, spectral measurement is carried out using identical decaying transmission principle, selection is proper also to be obtained
To said effect, even better than said effect, triangular prism shaped bi-material layers die body cannot be only taken, but is needed respectively to difference
The wedge-shaped die body of material is scanned, and is then carried out the superposition of equation, is increased the complexity and cost of experiment in a way,
So comprehensively considering the triangular prism shaped bi-material layers die body chosen and be made of two kinds of attenuating materials of aluminium and iron, the structure of wedge-shaped die body is special
When point can guarantee X-ray by a kind of attenuating material, it can produce different thickness, obtain a series of linear equations, to three
Prismatic bi-material layers die body is scanned the transmission that can be realized respectively by single pass to two kinds of attenuating materials；
The size of die body 2 and specific location between light source 1 and detector 3 according to light source 1 and detector 3 away from
Size setting from 3 working face of angle and detector that, X-ray covers, the X-ray for emitting light source 1 cover entire die body
2, and received by 3 working face of detector；The obtuse angle angle of the isosceles obtuse triangle of triangular prism shaped bi-material layers die body is penetrated according to X
The setting of the thickness of the distance between angle, light source 1 and die body 2 that line covers and attenuating material should guarantee that X-ray energy covers
Entire die body 2 guarantees that the thickness of die body 2 is unlikely to keep number of photons decaying excessively serious and influence Effect on Detecting again, so,
In specific implementation, the angle at obtuse angle needs to comprehensively consider the decision of actual scanning system.
Step 103, setting detector 3 are ordinary flat charge integration type X-ray detector；
Step 104 scans triangular prism shaped bi-material layers die body 2 using the first CT scan system, and starting X-ray bulb emits X
The X-ray of ray, sending is injected from the plane of incidence 203, also cross two kinds of attenuating materials of die body 2, from 204 He of the first exit facet
Second exit facet 205 projects；
Step 105, detector 3 receive the X-ray signal after die body 2, obtain first group of scan data I (xS, i)；
Step 2 removes die body 2 in the first CT scan system, and other parameters and condition are constant, the pipe electricity including bulb
Pressure, tube current, the parameters such as relative position between bulb and detector form the second CT scan system, start light source 1, carry out
Sky is swept, and second group of scan data I (0 is obtaineds)。
Step 3 is based on decaying transmission principle, carries out X-ray energy spectrum measurement, the first group of scan data obtained according to scanning
X-ray energy spectrum is solved with second group of scan data, obtains the discrete power spectrum of X-ray first, specific method is：
It is saturating to obtain X-ray for step 301, the first group of scan data and second group of scan data obtained using twice sweep
Rate is penetrated with the system of linear equations of the thickness change of attenuating material, the formula of linear equation is：
In formula, xS, i(i=1 ..., m, s=1,2) indicates that i-th kind of thickness of s kind attenuating material, s=1 are expressed as first
Kind attenuating material iron 201, s=2 are expressed as attenuation of the second kind materials of aluminum 202, and m indicates the thickness total number of s kind attenuating material,
The value of m is determined by the number of the search coverage divided on detector 3；T(xS, i) indicate discretization X-ray transmission rate, T
(xS, i)=I (xS, i)/I(0s), I (xS, i) it is first group of scan data, it indicates by with a thickness of xS, iAttenuating material after spy
Survey device received signal strength, I (0s) it is second group of scan data, indicate that the empty detector without decaying swept receives signal
Intensity；Ej(j=1 ..., n) indicates that discrete photon energy, j indicate the number of different discrete photon energy, and n indicates discrete photon
The total number of energy, for the positive integer greater than 1, the value of n according to practical operation condition and guarantees equation in actual operation
Number is more than or equal to n and sets, E1=Emin, indicate photon energy lower limit, En=Emax, indicate the photon energy upper limit；F(Ej) table
Show discrete energy spectrum；μs(Ej) indicate under each conventional attenuating material s mass attentuation coefficient；ρsIndicate attenuating material s
Density；Δ E indicates conventional interval width, Δ E=(Emax-Emin)/(n-1)；In the present embodiment, m value is that 60, n takes
Value is 60, and energy interval Δ E is 2, obtains 60 linear equations, wherein preceding 30 linear equations are after attenuating material iron
Equation, rear 30 linear equations are the equation after attenuating material aluminium；
Step 302, using the system of linear equations in EM algorithm solution procedure 301, rebuild X-ray energy spectrum, obtain X
Ray the first discrete energy spectrum F (Ej)；Since x-ray attenuation coefficient is very slow with energy variation, the coefficient of system of linear equations
Matrix has height pathosis, can not carry out spectrum unscrambling using the conventional method of matrix inversion, the side after two kinds of attenuating materials
Journey pathosis is compared have been substantially reduced with a kind of attenuating material, can use the calculation that expectation maximization solves ill-condition equation at this time
Method goes to solve equation, obtains more accurate the first discrete energy of X-ray spectrum.
Step 4 replaces the spy of the ordinary flat in the second CT scan system with CT photon counting-type detector to be measured
Device is surveyed, the setting of light source 1 is constant, carries out sky and sweeps, obtains the discrete power spectrum of X-ray second.
Step 5 compares the discrete power spectrum of X-ray second and the discrete power spectrum of X-ray first, if the two is consistent or misses
Difference is within the scope of predictive error, then CT photon counting-type detector accuracy reaches requirement, and otherwise, accuracy is insufficient.It is predetermined to miss
Difference can be obtained by calculating relative error, and scheduled error is relative error less than 2% in the present embodiment, and error is got in principle
Small better, specific range is artificially chosen according to actual scanning system.The comparing result of two power spectrums can instruct the next of detector
Correction work is walked, such as bad point correction assesses it to CT imaging performance to carry out more accurate performance test to detector
It influences.
The method of detection CT photon counting-type detector accuracy provided in this embodiment, using based on decaying transmission principle
Spectral measurement method go indirectly detect the poly-talented detector accuracy of photon method, on the basis of original attenuation transmission principle
On, by the way that triangular prism shaped bi-material layers die body is arranged, carry out spectral measurements based on two kinds of attenuating materials, effectively mitigate in root to
The pathosis of the system of linear equations of solution can acquire relatively accurate discrete power spectrum using common linear equation derivation algorithm
Value has high reliability.Triangular prism shaped bi-material layers die body in the present embodiment, die body structure is simple, can place simultaneously
Two kinds of materials do not have an impact mutually simultaneously, and easy to operate, scanning times are few, can be obtained by two kinds of materials by single pass
Attenuation data not only improves the pathosis of equation, also saves resource, can effectively be the subsequent school of photon counting-type detector
Positive work provides strong foundation, is more advantageous to and the performance test to photon counting-type detector is promoted to work.
Finally it should be noted that：The above embodiments are only used to illustrate the technical solution of the present invention., rather than its limitations；To the greatest extent
Present invention has been described in detail with reference to the aforementioned embodiments for pipe, those skilled in the art should understand that：Its according to
So be possible to modify the technical solutions described in the foregoing embodiments, or to some or all of the technical features into
Row equivalent replacement；And these are modified or replaceed, it does not separate the essence of the corresponding technical solution, and the claims in the present invention are limited
Fixed range.
Claims (5)
1. a kind of method for detecting CT photon counting-type detector accuracy, which is characterized in that this approach includes the following steps：
Step 1 builds the first CT scan system, including light source (1), die body (2) and detector (3), scans to obtain to die body
One group of scan data, specifically includes：
Step 101, setting light source (1) are X-ray bulb；
Step 102, the die body (2) are set between the light source (1) and detector (3), and the die body (2) is set as triangular prism
Shape bi-material layers die body, the upper bottom surface of the triangular prism are the isosceles obtuse triangle of congruence, on the bottom edge of the above bottom surface
Rectangular section where high is boundary, triangular prism die body is divided into the big wedge-like portions such as two, side wedge shape declines for the first
Subtract material (201), other side wedge shape is attenuation of the second kind material (202)；The bottom edge of isosceles obtuse triangle in the triangular prism
For the rectangle sides at place as the plane of incidence (203), other two rectangle sides is respectively the first exit facet (204) and the second outgoing
Face (205), light source (1) described in the plane of incidence (203) face are placed；
Step 103, setting detector (3) are ordinary flat charge integration type X-ray detector；
Step 104 scans the triangular prism shaped bi-material layers die body using the first CT scan system, starts the X-ray ball
Pipe emits X-ray, and the X-ray of sending is injected from the plane of incidence (203), also cross two kinds of decaying materials of the bi-material layers die body
Material is projected from first exit facet (204) and the second exit facet (205)；
Step 105, the detector (3) receive the X-ray signal after the die body (2), obtain first group of scan data；
Step 2 removes die body (2) in the first CT scan system, and other parameters and condition are constant, forms the second CT scan
System starts light source (1), carries out sky and sweeps, obtains second group of scan data；
Step 3, based on decaying transmission principle, X-ray energy spectrum measurement is carried out, according to the obtained first group of scan data of scanning and the
Two groups of scan datas solve X-ray energy spectrum, obtain the discrete power spectrum of X-ray first；
Step 4 replaces the ordinary flat detector in the second CT scan system with CT photon counting-type detector to be measured,
The setting of light source (1) is constant, carries out sky and sweeps, obtains the discrete power spectrum of X-ray second；
Step 5 compares the discrete power spectrum of the X-ray second and the discrete power spectrum of the X-ray first, if the two is consistent
Or error within the scope of predictive error, then CT photon counting-type detector accuracy reaches requirement, otherwise, accuracy is insufficient.
2. a kind of method for detecting CT photon counting-type detector accuracy according to claim 1, which is characterized in that institute
It states in step 1, the size of the die body (2) and the specific location being set between the light source (1) and detector (3) are according to light source
(1) at a distance from detector (3), the size setting of the angle that X-ray covers and detector (3) working face, make the light source
(1) X-ray emitted covers entire die body (2), and is received by detector (3) working face.
3. a kind of method for detecting CT photon counting-type detector accuracy according to claim 1, which is characterized in that institute
State the angle that the obtuse angle angle of the isosceles obtuse triangle of triangular prism shaped bi-material layers die body covers according to X-ray, light source (1) with
The setting of the thickness of the distance between die body (2) and attenuating material should guarantee that X-ray energy covers entire die body (2), guarantee again
The thickness of die body (2) is unlikely to keep number of photons decaying excessively serious and influence Effect on Detecting.
4. a kind of method for detecting CT photon counting-type detector accuracy according to claim 1, which is characterized in that institute
It states in step 3, based on decaying transmission principle, the method for carrying out X-ray energy spectrum measurement is specially：
Step 301, the first group of scan data and second group of scan data obtained using twice sweep obtain X-ray transmission rate
With the system of linear equations of the thickness change of attenuating material, the formula of linear equation is：
In formula, xS, i(i=1 ..., m, s=1,2) indicates that i-th kind of thickness of s kind attenuating material, s=1 are expressed as the first and decline
Subtract material (201), s=2 is expressed as attenuation of the second kind material (202), and m indicates the thickness total number of s kind attenuating material, m's
Value is determined by the number of the search coverage divided on detector (3)；T(xS, i) indicate discretization X-ray transmission rate, T
(xS, i)=I (xS, i)/I(0s), I (xS, i) it is first group of scan data, it indicates by with a thickness of xS, iAttenuating material after spy
Survey device received signal strength, I (0s) it is second group of scan data, indicate that the empty detector without decaying swept receives signal
Intensity；Ej(j=1 ..., n) indicates that discrete photon energy, j indicate the number of different discrete photon energy, and n indicates discrete photon
The total number of energy, for the positive integer greater than 1, the value of n according to practical operation condition and guarantees equation in actual operation
Number is more than or equal to n and sets, E1=Emin, indicate photon energy lower limit, En=Emax, indicate the photon energy upper limit；F(Ej) table
Show discrete energy spectrum；μs(Ej) indicate under each conventional attenuating material s mass attentuation coefficient；ρsIndicate attenuating material s
Density；Δ E indicates conventional interval width, Δ E=(Emax-Emin)/(n-1)；
System of linear equations in step 302, solution procedure 301 rebuilds X-ray energy spectrum, is solved using EM algorithm linear
Equation obtains X-ray the first discrete energy spectrum F (Ej)。
5. a kind of method for detecting CT photon counting-type detector accuracy according to any one of claims 1 to 4, special
Sign is that the attenuation of the first kind material (201) is iron, and attenuation of the second kind material (202) is aluminium.
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| CN109100775B (en) * | 2018-07-06 | 2020-05-29 | 郑州云海信息技术有限公司 | Energy spectrum correction method and device for double-layer detector |
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