CN110368009A - The corrected method of the detection efficient of a kind of pair of pet detector - Google Patents
The corrected method of the detection efficient of a kind of pair of pet detector Download PDFInfo
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Abstract
The present invention discloses the corrected method of detection efficient of a kind of pair of pet detector, and method includes: A1, obtains the scan data behind PET system placement bucket source；A2, according to the scan data, determine actual position information of the bucket source in the PET system；A3, according to the actual position information, obtain the relevant update information in bucket source and the average information for correcting detection efficiency；A4, according to radionuclide intensity in the update information, average information, scan data, the actual position information in the bucket source and the bucket source, obtain the correction value of all crystal detection efficients.The invention enables detection efficient measurement experiment Operating Complexities to substantially reduce, and can effectively reduce staff's institute's raying in this experiment, and experimental cost is effectively reduced.
Description
Technical field
The present invention relates to the corrected sides of the detection efficient of medical imaging field more particularly to a kind of pair of pet detector
Method.
Background technique
Positron emission tomography (Positron Emission Tomography, PET) is currently the only can to show
Show the metabolism of living body biological molecule, receptor and the movable New video technology of neurotransmitter, is widely used in the mirror of a variety of diseases
Not Zhen Duan, therapeutic evaluation, organ function research and new drug development etc..Its working principle is that by biological life be metabolized in it is necessary
Substance, such as: glucose, protein, nucleic acid, fatty acid, short-life radionuclide is (such as on label18F,11C etc.), note
Enter human body, it is different using metabolism state of the human body different tissues to labeled substance, such as in the malignant tumor tissue of hypermetabolism
Middle glucose metabolism is vigorous, and aggregation is more etc., and the feature of these reflection vital metabolic activities is showed by image, thus
Achieve the purpose that early diagnose the diseases such as tumour.
In PET scan, decay release positive electron occurs for radionuclide, buries in oblivion with free negative electron, generates several
Back-to-back two photons.Detector infers the true generation position of event with this by detecting the photon pair；Meanwhile it visiting
Measure the generation intensity of how much reflection events of photon pair.When only all detectors are consistent for the detection efficient of photon,
It can obtain the image for really reflecting radionuclide specific activity distribution.But by the structure of detector, detector crystal it is non-same
The influence of the factors such as property, PET system difference probe unit are inconsistent to the detection efficient for the photon for being incident on its surface.It is terrible
To radionuclide specific activity distributed image unbiased esti-mator, different probe units carry out inconsistent correct back to of photon detection efficiency.
The correction experiment of the detection efficient of current pet detector, needs artificially to be placed on bucket source the center of detector, into
And carry out the correction of the detection efficient of pet detector.However, in actual operation, in order to guarantee that a barrel source is placed centrally, usually needing
Operator is wanted repeatedly to touch containing active bucket source, accurately to adjust the position in barrel source.This not only makes the experiment multiple
Miscellaneous, operating difficulties also makes experimenter need to be subjected to the radiation of large dosage.
Summary of the invention
To solve the above problems, the object of the present invention is to provide the detection efficient of a kind of pair of pet detector is corrected
Method.
To achieve the above object, the main technical schemes that the present invention uses include:
In a first aspect, the present invention provides the corrected method of detection efficient of a kind of pair of pet detector, comprising:
A1, the scan data behind PET system placement bucket source is obtained；
A2, according to the scan data, determine actual position information of the bucket source in the PET system；
A3, according to the actual position information, obtain the relevant update information in bucket source and in correcting detection efficiency
Between information；
A4, according to the update information, average information, scan data, the actual position information in the bucket source and the bucket
Radionuclide intensity in source obtains the correction value of all crystal detection efficients.
Optionally, the step A2 includes:
A21, it is based on the scan data, using selected algorithm for reconstructing, obtains the reconstruction image in bucket source；
A22, according to the reconstruction image, obtain center of gravity, obtain the actual position information in barrel source using gravity model appoach.
Optionally, the step A21 includes:
A21-1, the reconstruction that undamped correction is carried out to scan data, obtain PET activity distributed image one；
A21-2, the average value for calculating all pixels in PET activity distributed image one, select the average value matched pre-
If threshold value, the pixel for being greater than preset threshold in PET activity distributed image one is selected；
According to priori knowledge, the attenuation coefficient corresponding with bucket source substance of the pixel of selection is assigned, attenuation coefficient is obtained
Distribution one；
A21-3, the reconstruction for having correction for attenuation is carried out using a pair of of scan data of attenuation coefficient distribution, it is living obtains PET
Spend distributed image two；
The process of iteration P above-mentioned steps A21-2 and step A21-3 obtain living by the PET of accurate correction for attenuation
Degree distribution output image；
Wherein, when iteration P is according to the activity size of radionuclide in the performance of pet detector, bucket source and/or acquisition
Between determine.
Optionally, the step A21 includes:
A211, the acquisition data that the bucket source is obtained according to other imaging systems are obtained and are rebuild PET activity distribution output figure
As corresponding attenuation coefficient is distributed；
A212, the reconstruction for having correction for attenuation is carried out to scan data using attenuation coefficient distribution, obtains PET activity point
Cloth exports image.
That is, when experiment has the auxiliary of other imaging systems, and high-precision configuration figure can be provided for PET image reconstruction
It when picture, can be distributed with accurate definition attenuation coefficient, can directly carry out the process of correction for attenuation reconstruction, obtain by accurately declining
The output image of correction down.
Optionally, update information relevant to the bucket source includes following one or more:
Indicate that different LOR are influenced by detector geometry and cause the non-uniform modifying factor SG of detection efficientuivj；
Indicate different LOR by die body geometry influenced and caused by detection efficient non-uniform modifying factor FGuivj；
Average information for correcting detection efficiency includes: to meet number of crystals Nui。
Optionally, the acquisition in the step A3 is used for the average information of correcting detection efficiency, comprising:
A3-1, the actual position information based on the bucket source are selected in any crystal and the LOR of its face faceted crystal composition
LOR across bucket source part, the LOR across bucket source part are with the symmetrical LOR of diameter detector；
The actual position information of A3-2, the LOR of foundation selection and bucket source, determine effective LOR, obtain meeting number of crystals Nui；
Alternatively,
A31, the actual position information based on the bucket source, select it is all by bucket source and about bucket source diameter it is symmetrical
LOR；
The actual position information of A32, the LOR of foundation selection and the bucket source, determine effective LOR, obtain meeting number of crystals
Nui。
Optionally, the step A4 includes:
Every LOR actual detection example number E in A41, foundation scan datauivj, radionuclide intensity in the bucket source
With the update information, the product η of the both ends crystal detection efficient of every LOR is obtained based on following formula oneuivj；
Wherein, EuivjActual detection example number, u, v represent the axial number of any two crystal, and i, j represent the ring of crystal
To number；
A indicates radionuclide intensity, SGuivjIndicate the modifying factor of the correspondence detector geometry of influence detection efficient
Son；
FGuivjIndicate the modifying factor of the correspondence bucket source geometry of influence detection efficient；
A42, the detection efficient according to formula two and formula three, after obtaining correction.
Wherein, NuiExpression meets number of crystals.
Second aspect, the present invention provide a kind of PET system, which is characterized in that including pet detector, the pet detector
Execute any method of above-mentioned first aspect.
The beneficial effects of the present invention are:
When being corrected due to the detection efficient of the prior art, being placed centrally for bucket source is the requirement for being not easy satisfaction.This
The method of invention greatly reduces the operation of experiment so that detection efficient measurement experiment no longer needs a barrel source to be strictly placed centrally
Difficulty, while reducing the radiation risk of staff.
In addition, method of the invention makes full use of a barrel source scan data, the true position in barrel source is obtained by computer program
It sets.And then the actual position in bucket source is utilized, and the deviation of detection efficient theoretical caused by uneven irradiation is modeled, it will be by
It is eccentric in bucket source position and caused by difference detector meet line to the difference of bucket source radioactive activity integrated value to what is constituted
It corrects back to and, so that it is equivalent to all crystal and be illuminated uniformly.Eccentric bucket source scan data is corrected, it is available
Reflect the detection efficient distribution of the intrinsic difference of crystal efficiency.
Further, in detection efficient calculating process, valid data are adaptively utilized, exclude due to invalid data band
The counting loss come.So-called valid data refer to that detector passes through bucket source to the line that meets of composition；And invalid data, refer to
It is to meet line not over bucket source.
Detailed description of the invention
Fig. 1 is the fan-shaped schematic diagram that crystal ui and one group of crystal of right opposite meet line formation in the present invention；
Fig. 2 is the schematic diagram that sectorial area is determined in the present invention；
Fig. 3 is in the present invention according to the signal of eccentric barrel source actual calculation of location corresponding the case where at least meeting number of crystals
Figure；
Fig. 4 is in the present invention according to the corresponding signal for meeting number of crystals of the eccentric barrel source each crystal of actual calculation of location
Figure；
Fig. 5 is showing for the corrected method of detection efficient for a kind of pair of pet detector that one embodiment of the invention provides
It is intended to.
Specific embodiment
In order to better explain the present invention, in order to understand, with reference to the accompanying drawing, by specific embodiment, to this hair
It is bright to be described in detail.
The scheme of embodiment in order to better understand the present invention carries out general introduction to the scheme of the embodiment of the present invention below and says
It is bright.
Improvement for a better understanding of the present invention below says the correction course of the detection efficient of existing pet detector
It is bright as follows.
Radionuclide specific activity distributed image unbiased esti-mator in order to obtain, different probe units to photon detection efficiency not
Consistent that artificial correct back to is needed, which is called normalization.
Relatively common normalization method has direct measuring method and detection efficient modularization measurement method.The former is
Reduction statistical noise, needs largely to count, acquisition time is longer, is extremely difficult to more satisfactory statistic.Currently, facing
In bed application, detection efficient modularization measurement method is generally used.In the case where guaranteeing all detector cells uniform irradiations,
The counting of detector cells is how many, reflects the height of its relative detection efficiency.It is uniform in order to meet all detector cells
The precondition of irradiation, detection efficient are generally come using the bucket source for being centrally placed in visual field (FOV, Field-of-View)
Measurement.Wherein, bucket source is to cover drum of the detector axis to FOV with certain radius, axial length, and have certain activity
Radionuclide (such as contains18The liquid source of F contains68The Solid Source of G, or contain other radionuclides).
The experiment of detection efficient modifying factor measurement, it is desirable that all detector crystals are illuminated uniformly, that is, bucket source is required to occupy
Middle placement.In actual operation, in order to guarantee this point, it usually needs operator repeatedly touches containing active bucket source, with
The accurate position for adjusting bucket source.This not only makes the experiment complicated, and operating difficulties also makes experimenter need to be subjected to big agent
The radiation of amount.
When detection efficient measurement experiment, being placed centrally for bucket source is the requirement for being not easy satisfaction.In practical operation, one
As bucket source is first placed roughly to the center of cross section FOV, by being tentatively imaged, calculate bucket source center of gravity, fine-tune barrel source
Position.Process needs are repeated multiple times just to can guarantee that barrel source strictly occupy the center FOV.
Embodiment one
The invention proposes the corrected methods of the detection efficient of a kind of pair of pet detector, as shown in Figure 1, this implementation
The method of example includes following content.
A1, the scan data behind PET system placement bucket source is obtained.
It will be appreciated that the collected data that meet of Solid-state pet detector system are generally divided into list mode data (List
Mode Data) and sinogram data (Sinogram Data), wherein List Mode data can pass through data sorting
(Sorting) Sinogram data are converted to.
A2, according to the scan data, determine actual position information of the bucket source in the PET system；
For example, step A2 may include following sub-step not shown in the figure:
A21, it is based on the scan data, using selected algorithm for reconstructing, obtains the reconstruction image in bucket source；
A22, according to the reconstruction image, obtain center of gravity, obtain the actual position information in barrel source using gravity model appoach.
A3, according to the actual position information, obtain the relevant update information in bucket source and in correcting detection efficiency
Between information；
For example, update information relevant to the bucket source includes following one or more:
Indicate that different LOR are influenced by detector geometry and cause the non-uniform modifying factor SG of detection efficientuivj；
Indicate different LOR by die body (i.e. detected object) geometry influenced and caused by detection efficient it is non-uniform
Modifying factor FGuivj；
Average information for correcting detection efficiency includes: to meet number of crystals Nui。
A4, according to the update information, average information, scan data, the actual position information in the bucket source and the bucket
Radionuclide intensity in source obtains the correction value of all crystal detection efficients.
That is, in pet detector all crystal detection efficients correction value.
When being corrected due to the detection efficient of the prior art, being placed centrally for bucket source is the requirement for being not easy satisfaction.This
The method of invention greatly reduces the operation of experiment so that detection efficient measurement experiment no longer needs a barrel source to be strictly placed centrally
Difficulty, while reducing the radiation risk of staff.
Embodiment two
The most common structure of pet detector be it is cylindric, the structure overall alignment being made of crystal is in periphery.It is visited
It surveys object to be placed in bed body, gos deep into carrying out data acquisition in cylinder.Different crystal judges what it was detected by electrical signal
Whether photon is recorded from the same example.If two crystal detect two light from same example
Son, then the example occurs on the line of two crystal certainly.In analysis, which is known as meeting line of response LOR (Line
of Response).The collected data that meet of Solid-state pet detector system are generally divided into list mode data (List Mode
Data) and sinogram data (Sinogram Data), wherein List Mode data can pass through data sorting (Sorting) and turn
It is changed to Sinogram data.The data format that scan data uses in the application is Singoram data.In Sinogram data
Each element size represents the actual detection example number E of corresponding LORuivj。
LOR actual detection example number EuivjIt can indicate are as follows:
Euivj=A × SGuivj×FGuivj×εui×εvj………………………………………………(2)
The detection efficient of any one LOR can be expressed as the product of both ends crystal detection efficient:
ηuivj=εui×εvj……………………………………………………(1)
Wherein, u, v represent the axial number of any two crystal, and i, j represent the circumferential number of crystal.
In above-mentioned formula, A indicates radionuclide intensity；SGuivjIndicate different LOR by detector (Scanner) geometry
Structure influence and caused by the non-uniform modifying factor of detection efficient, the angle difference etc. of crystal is incident on from different LOR
Factor is general to be obtained by rotation line source experiment measurement；FGuivjIndicate that different LOR are influenced by die body (Phantom) geometry
The non-uniform modifying factor of detection efficient caused by and passes through the length of die body (detected object) not from different LOR
Unanimously, which is strictly dependent on shape and the position of die body.By SGuivjAnd FGuivjRevised LOR distribution is equivalent to institute
Some crystal are illuminated uniformly, the intrinsic difference for being only detector crystal efficiency of reflection.By analyzing the distribution, can obtain
To the intrinsic detection efficient of detector cells.
As shown in Figure 1, an arbitrarily selected detector crystal-ui, selectes one group of crystal A, ui and A in its circumferential right opposite
In any one crystal vj be consistent.Then the detection efficient of any crystal ui can indicate are as follows:
Combinatorial formula (1), obtains
The premise that above formula is set up is opposite crystal efficiency (crystal included in Group A in Fig. 1) and to be approximately equal to its brilliant
Body number, i.e.,
Wherein, N is the crystal number being consistent with crystal ui right opposite (GroupA in Fig. 1) with it.In the present invention, by N
It is defined as meeting number of crystals in detection efficient calculating process.The number of crystals that Group A includes is more, different crystal detection efficient
Intrinsic difference will be compensated for, and mean value is closer to 1, i.e., summation is close to crystal sum, and above formula is closer to equal.It is theoretical
On, it should guarantee the establishment of formula (5) using LOR as much as possible, and statistics can be increased, reduces noise.
But in actual normalization experimental implementation, by the LOR at bucket source edge, the effective length across bucket source is short,
Count it is less, have very big statistic fluctuation.In order to avoid being influenced by the LOR at bucket source edge on result bring, when experiment,
It will generally be removed by the LOR at bucket source edge when calculating detection efficient.It is specific to pass through the bucket source center of circle as shown in Fig. 2, only choosing
Neighbouring LOR.
Under conditions of strict demand bucket source is placed centrally, FG is generally provided in advanceuivjDistribution and detection efficient calculate
In the process meet number of crystals.But when bucket source is not placed centrally according to given requirements, it can make first related to bucket source
Geometrical factor FGuivjMistake is corrected, secondly, introducing invalid LOR when causing to calculate certain crystal efficiencies.The above two o'clock, can
Detection efficient is caused to calculate mistake.
Method of the invention overcomes the limitation being placed centrally in existing algorithm for bucket source.First with sweeping for detector
Data are retouched, the reconstruction image in barrel source is obtained, and then calculate the physical location in bucket source by gravity model appoach；Secondly, according to bucket source reality
Position obtains geometrical factor modifying factor relevant with bucket source, and is modified to scan data；Finally, according to the reality in bucket source
Position obtains meeting number of crystals in detection efficient calculating process in the case where guaranteeing that studied LOR effectively passes through barrel source.
The image distribution that under multi-modal scan pattern, the position in bucket source can also be provided by other scanning mode is obtained
Out.
1)The real center in barrel source is obtained using gravity model appoach
Step 1: obtaining the reconstruction image in barrel source based on selected algorithm for reconstructing according to scan data.
For example, in practice, the integrated ordered subset expectation maximization algorithm (Ordered- of PET system can be used
Subset-Expectation-Maximization, OSEM) scan data is handled, obtain the reconstruction image in bucket source.
In other embodiments, the method reconstruction image using above-mentioned OSEM can not also be limited, according to actual needs into
Row selection, the method for any reconstruction image can be used.
It will be appreciated that the reconstruction image in above-mentioned steps one, can for example, one kind be achieved in that without other at
When as system auxiliary, obtained reconstruction image.Another kind is that there are reconstruction images when other imaging systems auxiliary, obtained.
Step 2: being based on reconstruction image, the center of gravity in bucket source is calculated.For different scan patterns, the acquisition of image reform
Approach slightly has difference.
Step 3: determining location information of the bucket source in PET system according to the center of gravity in the bucket source.
1.1) it is assisted without other imaging systems, obtains reconstruction image
When auxiliary of the experiment without other imaging systems, the attenuation coefficient distribution in bucket source is unknown.For this purpose, this implementation
It needs to obtain attenuation coefficient using acquisition data i.e. scan data in example to be distributed.Specific step is as follows:
Step 1: carrying out the reconstruction of undamped correction to acquisition data, that is, scan data, obtain PET activity distributed image one.
Step 2: calculating the average value of pixel in PET activity distributed image one, according to the value, set suitable threshold value (ratio
Such as: 0.5 times of average value), it will be greater than the pixel of the threshold value, according to priori knowledge, assign decline corresponding with bucket source substance
Subtract coefficient, for example, the attenuation coefficient of liquid water is 0.096.And it is less than the pixel of the threshold value, it is set as 0, obtains attenuation coefficient point
Cloth one.
Step 3: a pair of of acquisition data, which are distributed, using attenuation coefficient obtained in step 2 carries out the reconstruction for having correction for attenuation,
Obtain PET activity distributed image two.Step 2 is repeated, attenuation coefficient distribution two is obtained.
Successively iteration continues, can obtain exporting image (namely by the PET activity distribution of accurate correction for attenuation
It says, the reconstruction image reaction of PET is exactly detected object activity distribution map, and the two is consistent).The number of iterations depends on
The performance of pet detector, the activity size of radionuclide, acquisition time etc..
In other embodiments, the reconstruction image of PET system, can also by means of have other imaging systems auxiliary, such as
The modes such as MR modality assist.
It, can be with when experiment has the auxiliary of other imaging systems, and can provide high-precision configuration image for PET image reconstruction
The distribution of accurate definition attenuation coefficient, can directly carry out above-mentioned steps 3, obtain the output image by accurate correction for attenuation.
About the mode of other modality assisted reconstruction images, the application is repeated no more.In following way of example with without other at
Sub- explanation in case where being assisted as system.
1.2) it is directed to step 2 above-mentioned, calculates the center of gravity in bucket source, detailed description are as follows.
Image is exported by analysis, obtains the true location coordinate in barrel source in two steps.Specific step is as follows:
Step 01: using whole image as research object, calculating its center of gravity.Specific calculation formula is as follows:
Wherein, PixeliFor the value of any pixel i, xiAnd yiFor the x and y coordinates of respective pixel.It is research with all pixels
Object can obtain the center of gravity x ' in barrel sourcecAnd y 'c。
Step 02: due to calculating center of gravity x 'cAnd y 'cWhen all pixels are utilized, it is understood that there may be periphery background is to result
Influence.And then on the basis of step 01, with (x 'c, y 'c) it is the center of circle, select the bigger drum of a radius ratio bucket source radius
Range.It can be adjusted according to the actual situation selected drum range.Bring the value of all pixels in selection area into formula
(6) in, the true center of gravity x in barrel source can be found outcAnd yc.And the eccentric distance in bucket source can pass through xcAnd ycObtain a barrel source
Eccentric distance:
2) actual position according to bucket source calculates the geometric corrections factor relevant with bucket source
As shown in Fig. 2, the length that difference LOR is passed through in bucket source is different, i.e., the sum of photon occurs on LOR route not
Together.It is modeled by PET system, available bucket source radioactive activity is distributed in the integrated value on different LOR, i.e., in acquisition data
Geometric corrections factor FG related to bucket sourceuivj.The SG that joint preamble is testeduivj, using formula (2), can obtain by
Detection efficient distribution after correction, being equivalent to all LOR under the conditions of all crystal are illuminated uniformly.The distribution is analyzed, just
The relative detection efficiency of available detector cells.
So-called SGuivj, refer to photon in different LOR since different, crystal exists by the angle that is incident on corresponding crystal
The reasons such as position difference influence and the difference relatively of detected efficiency in detector.It is generally obtained, for example revolved by other experiments
Turn line source.Traditionally, the geometric corrections factor of detector, i.e. SG are referred to asuivj。
So-called FGuivj, obtained by system modelling.FGuivjIt refers to being detected at different location by each LOR in FOV
Probability is determined by the size of the two detector subtended angles corresponding to LOR of difference in FOV.Its calculating process is comparatively laborious, generally
It takes and calculates in advance, is stored as certain format, clinically call directly.Traditionally, it is referred to as system modelling.Quilt
When detecting object difference, by the probability detected at different location in FOV by each LOR multiplied by the radioactive activity at this, i.e.,
It can obtain detected integrated value of the object on each LOR.
3) actual position according to bucket source, which calculates in detection efficient calculating, meets number of crystals
In general, detection efficient in order to obtain, chooses the LOR that any crystal is constituted with its face faceted crystal and is studied.
But when detected object bias is placed, selected certain LOR become invalid LOR before will cause, and cause calculated result wrong
Accidentally.Pass through a barrel source to guarantee that all detector cells and its meet the LOR that crystal is constituted, meeting number of crystals should be by being visited
The physical location for surveying physics determines.
In the embodiment of the present invention, the method searching for providing two kinds of adaptive detected physics physical locations meets number of crystals.
The first, chooses and passes through bucket source part in the LOR that any crystal and its face faceted crystal are constituted as research object,
I.e. studied LOR is symmetrical about diameter detector；
Second, all LOR by bucket source are chosen as research object, that is, studied LOR is symmetrical about bucket source diameter.
For every case, both effective LOR can be determined by system modelling on the basis of the physical location of bucket source,
It obtains meeting number of crystals, can also directly be calculated and meet by the geometrical relationship between bucket source physical location and detector
Number of crystals.
3.1) meet number of crystals by symmetry axis selection of diameter detector
System modelling
In order to adaptively obtain meeting number of crystals used in detection efficient calculating process, any crystal ui is selected, is utilized
Bucket source physical location, by system modelling above-mentioned, under the premise of guaranteeing that LOR passes through bucket source, assessment is located at the crystal face
Face, the number of crystals being consistent with the crystal, are denoted as Nui。
In order to guarantee the selected right opposite for meeting crystal set and being located at crystal ui, first selection crystal face faceted crystal
Vj, by guaranteeing vj- (Nui- 1) vj+ (N/2 is arrivedui- 1) before the LOR of crystal and crystal ui composition completely extends across barrel source between/2
Condition is proposed, N is obtainedui.After traversing all crystal, obtain corresponding with all crystal meeting number of crystals.
Consider the relatively fewer, problem that statistic fluctuation is larger by the counting of bucket source edge LOR, will with pass through bucket source edge
LOR relevant crystal removal.The value data can optimize according to specific experiments.Finally selected value is imitated as detection
Each crystal in rate calculating process is corresponding to meet number of crystals Nui。
Geometrical relationship
As shown in figure 3, being located at A point for any crystal ui.Its space coordinate is known.Using being calculated before
Detected object center of gravity, be located at O ' point, calculate distance between the two, i.e. in Fig. 3 | O ' A | length, be denoted as d.FOV circle
The heart is O.In triangle OO ' A, three sides are no longer stated herein it is known that the solution procedure of angle is general equation.AB is connection
The bucket source tangent line of studied crystal, the nearly center of circle FOV O, point of contact E.B ' is symmetric points of the B about C.Wherein
Wherein, RcylFor the radius in bucket source, TransaxialCrystal is detector rings to number of crystals, NuiAs such as Fig. 3
The number of crystals for including in shown Group A.After traversing all crystal, obtain corresponding with all crystal meeting number of crystals.
Consider the relatively fewer, problem that statistic fluctuation is larger by the counting of bucket source edge LOR, will with pass through bucket source edge
LOR relevant crystal removal.The value data can optimize according to specific experiments.Finally selected value is imitated as detection
Each crystal in rate calculating process is corresponding to meet number of crystals Nui。
3.2) meet number of crystals by symmetry axis selection of bucket source diameter
In detection efficient calculating, meeting number of crystals as symmetry axis selection using diameter detector is conventional algorithm, still, when
When detected physics is eccentric too many, if only considering that crystal and its face faceted crystal set symbol close, certain crystal cannot be found
Effectively meet number of crystals.In order to consider such case, we meet number of crystals by symmetry axis selection of bucket source diameter.
System modelling
Each crystal is corresponding to meet number of crystals in order to adaptively obtain in detection efficient calculating process, selectes any crystal
Ui, using bucket source physical location, by system modelling above-mentioned, under the premise of guaranteeing that LOR passes through bucket source, assessment and the crystal
The number of crystals being consistent, is denoted as Nui.After traversing all crystal, obtain corresponding with all crystal meeting number of crystals.
Consider the relatively fewer, problem that statistic fluctuation is larger by the counting of bucket source edge LOR, will with pass through bucket source edge
LOR relevant crystal removal.The value data can optimize according to specific experiments.Finally selected value is imitated as detection
Each crystal in rate calculating process is corresponding to meet number of crystals Nui。
Geometrical relationship
In Fig. 4, for any crystal ui, it is located at A point.Its space coordinate is known.Utilize what is be calculated before
The center of gravity of detected object is located at O ' point, calculates distance between the two, i.e. in Fig. 4 | O ' A | length, be denoted as d.The center of circle FOV
For O.Meet to be formed in all LOR with crystal ui, across the part of detected object, as shown in figure between AB and AB '.
Number of crystals included in Group A is directly proportional to angle ∠ BOB '.Enable ∠ BOB '=θ.It, can be with using the geometrical relationship in figure
Obtain the ∠ of ∠ BOB '=2 BAB '.
In turn
Consistent, R discuss before incylFor the radius in bucket source, TransaxialCrystal is detector rings to number of crystals,
NuiThe number of crystals for including in Group A as shown in Figure 4.After traversing all crystal, meet corresponding with all crystal is obtained
Number of crystals.
Consider the relatively fewer, problem that statistic fluctuation is larger by the counting of bucket source edge LOR, will with pass through bucket source edge
LOR relevant crystal removal.The value data can optimize according to specific experiments.Finally selected value is imitated as detection
Each crystal in rate calculating process is corresponding to meet number of crystals Nui。
4) it utilizes and meets number of crystals calculating detection efficient
In the case that in bucket source, bias amplitude is little, in order to guarantee that the statistic fluctuation in the calculating of different crystal detection efficient is protected
Hold consistent, different crystal, which is generally chosen, same number of meets number of crystals.Meet crystal in each crystal obtained before
Number NuiIn, its minimum value is chosen, meets number of crystals N as in detection efficient calculating.Using formula (4), can be visited
Survey efficiency.
But when detected object is eccentric too many, different crystal to meet number of crystals difference bigger.If wanted by force
It asks and meets number of crystals using unified, the waste of data to a certain extent will be caused.It, will in order to utilize data to the greatest extent
The number of crystals that meets of each crystal obtained before brings formula (4) into respectively.Correspondingly, formula (4) becomes following form:
All crystal are traversed, detection efficient is obtained.
The realization of the present embodiment method reduces the complexity of staff's operation, does not have to it again to keep barrel source tight
Lattice are placed in the middle, and the position in each manually fine tuning bucket source；Secondly, the inclusiveness of experiment analytical method, reduces experiment
The case where re-starting is needed since bucket source is placed in the middle bad.
The invention enables detection efficient measurement experiment Operating Complexities to substantially reduce, and can effectively reduce staff at this
Institute's raying in experiment, and experimental cost is effectively reduced.
It is to be appreciated that describing the skill simply to illustrate that of the invention to what specific embodiments of the present invention carried out above
Art route and feature, its object is to allow those skilled in the art to can understand the content of the present invention and implement it accordingly, but
The present invention is not limited to above-mentioned particular implementations.All various changes made within the scope of the claims are repaired
Decorations, should be covered by the scope of protection of the present invention.
Claims (8)
1. the corrected method of the detection efficient of a kind of pair of pet detector characterized by comprising
A1, the scan data behind PET system placement bucket source is obtained；
A2, according to the scan data, determine actual position information of the bucket source in the PET system；
A3, believe according to the actual position information, the relevant update information in acquisition bucket source and for the intermediate of correcting detection efficiency
Breath；
A4, according in the update information, average information, scan data, the actual position information in the bucket source and the bucket source
Radionuclide intensity obtains the correction value of all crystal detection efficients.
2. the method according to claim 1, wherein the step A2 includes:
A21, it is based on the scan data, using selected algorithm for reconstructing, obtains the reconstruction image in bucket source；
A22, according to the reconstruction image, obtain center of gravity, obtain the actual position information in barrel source using gravity model appoach.
3. according to the method described in claim 2, it is characterized in that, the step A21 includes:
A21-1, the reconstruction that undamped correction is carried out to scan data, obtain PET activity distributed image one；
A21-2, the average value for calculating all pixels in PET activity distributed image one, select the matched default threshold of the average value
Value selects the pixel for being greater than preset threshold in PET activity distributed image one；
According to priori knowledge, the attenuation coefficient corresponding with bucket source substance of the pixel of selection is assigned, obtains attenuation coefficient distribution
One；
A21-3, the reconstruction for having correction for attenuation is carried out using a pair of of scan data of attenuation coefficient distribution, obtains PET activity point
Cloth image two；
The process of iteration P above-mentioned steps A21-2 and step A21-3 obtain the PET activity point by accurate correction for attenuation
Cloth exports image；
Wherein, iteration P is true according to the activity size of radionuclide and/or acquisition time in the performance of pet detector, bucket source
Fixed.
4. according to the method described in claim 2, it is characterized in that, the step A21 includes:
A211, the acquisition data that the bucket source is obtained according to other imaging systems are obtained and are rebuild PET activity distribution output image pair
The attenuation coefficient distribution answered；
A212, the reconstruction for having correction for attenuation is carried out to scan data using attenuation coefficient distribution, it is defeated obtains the distribution of PET activity
Image out.
5. the method according to claim 1, wherein update information relevant to the bucket source includes following one
Kind is a variety of:
Indicate that different LOR are influenced by detector geometry and cause the non-uniform modifying factor SG of detection efficientuivj；
Indicate different LOR by die body geometry influenced and caused by detection efficient non-uniform modifying factor FGuivj；
Average information for correcting detection efficiency includes: to meet number of crystals Nui。
6. according to the method described in claim 5, it is characterized in that, the acquisition in the step A3 is for correcting detection efficiency
Average information, comprising:
A3-1, the actual position information based on the bucket source are passed through in the LOR for selecting any crystal to constitute with its face faceted crystal
The LOR of bucket source part, the LOR across bucket source part are with the symmetrical LOR of diameter detector；
The actual position information of A3-2, the LOR of foundation selection and bucket source, determine effective LOR, obtain meeting number of crystals Nui；
Alternatively,
A31, the actual position information based on the bucket source, select it is all by bucket source and about the symmetrical LOR of bucket source diameter；
The actual position information of A32, the LOR of foundation selection and the bucket source, determine effective LOR, obtain meeting number of crystals Nui。
7. according to the method described in claim 6, it is characterized in that, the step A4 includes:
Every LOR actual detection example number E in A41, foundation scan datauivj, radionuclide intensity and described in the bucket source
Update information obtains the product η of the both ends crystal detection efficient of every LOR based on following formula oneuivj；
Wherein, EuivjActual detection example number, u, v represent the axial number of any two crystal, and i, j represent the circumferential of crystal and compile
Number；
A indicates radionuclide intensity, SGuivjIndicate the modifying factor of the correspondence detector geometry of influence detection efficient；
FGuivjIndicate the modifying factor of the correspondence bucket source geometry of influence detection efficient；
A42, the detection efficient according to formula two and formula three, after obtaining correction；
Wherein, NuiExpression meets number of crystals.
8. a kind of PET system, which is characterized in that including pet detector, the pet detector executes the claims 1 to 7
Any method.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109077748A (en) * | 2018-08-31 | 2018-12-25 | 北京锐视康科技发展有限公司 | A kind of accurately PET normalization method |
| CN111557675A (en) * | 2020-05-12 | 2020-08-21 | 上海联影医疗科技有限公司 | Correction method, device and system of medical imaging device |
| CN112807009A (en) * | 2021-02-02 | 2021-05-18 | 上海联影医疗科技股份有限公司 | Radioactive source positioning method, system, equipment, electronic device and storage medium |
| CN113069138A (en) * | 2021-03-23 | 2021-07-06 | 上海联影医疗科技股份有限公司 | Positron emission tomography device, coincidence efficiency detection method and normalization method |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20070176087A1 (en) * | 2006-01-31 | 2007-08-02 | Koninklijke Philips Electronics N.V. | Component method and system for pet detector efficiency normalization |
| CN105894525A (en) * | 2016-04-29 | 2016-08-24 | 上海联影医疗科技有限公司 | Detector correction method for positive electron emission tomography system |
| CN109077748A (en) * | 2018-08-31 | 2018-12-25 | 北京锐视康科技发展有限公司 | A kind of accurately PET normalization method |
-
2019
- 2019-08-09 CN CN201910735219.9A patent/CN110368009B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20070176087A1 (en) * | 2006-01-31 | 2007-08-02 | Koninklijke Philips Electronics N.V. | Component method and system for pet detector efficiency normalization |
| CN105894525A (en) * | 2016-04-29 | 2016-08-24 | 上海联影医疗科技有限公司 | Detector correction method for positive electron emission tomography system |
| CN109077748A (en) * | 2018-08-31 | 2018-12-25 | 北京锐视康科技发展有限公司 | A kind of accurately PET normalization method |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109077748A (en) * | 2018-08-31 | 2018-12-25 | 北京锐视康科技发展有限公司 | A kind of accurately PET normalization method |
| CN109077748B (en) * | 2018-08-31 | 2021-08-20 | 北京锐视康科技发展有限公司 | Accurate PET normalization correction method |
| CN111557675A (en) * | 2020-05-12 | 2020-08-21 | 上海联影医疗科技有限公司 | Correction method, device and system of medical imaging device |
| CN112807009A (en) * | 2021-02-02 | 2021-05-18 | 上海联影医疗科技股份有限公司 | Radioactive source positioning method, system, equipment, electronic device and storage medium |
| CN113069138A (en) * | 2021-03-23 | 2021-07-06 | 上海联影医疗科技股份有限公司 | Positron emission tomography device, coincidence efficiency detection method and normalization method |
| CN113069138B (en) * | 2021-03-23 | 2023-06-30 | 上海联影医疗科技股份有限公司 | Positron emission tomography device, coincidence efficiency detection method and normalization method |
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