CN109031394A - A method of measurement scintillator detector location information - Google Patents
A method of measurement scintillator detector location information Download PDFInfo
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- CN109031394A CN109031394A CN201810414331.8A CN201810414331A CN109031394A CN 109031394 A CN109031394 A CN 109031394A CN 201810414331 A CN201810414331 A CN 201810414331A CN 109031394 A CN109031394 A CN 109031394A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/29—Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation
- G01T1/2914—Measurement of spatial distribution of radiation
- G01T1/2985—In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis)
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- G—PHYSICS
- G01—MEASURING; TESTING
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Abstract
The invention discloses a kind of method for measuring scintillator detector location information, step includes: 1) to choose a positron radioactivity point source；2) along the central axis of nuclear imaging system, in the axial range of setting, make the positron radioactivity point source movement, record the positron radioactivity point source nuclear imaging system is collected in each setting position point and meet event；3) from the axial point receptance function for meeting every a pair of of face detector cells in the selection same ring of nuclear imaging system in event of acquisition；4) according to the axial point receptance function, the physical location information of detector cells is determined.Method of the invention can accurately, easily obtain the physical location parameter of PET imaging system detector cells.
Description
Technical field
The invention belongs to scintillator detector technical fields, are related to a kind of method of measurement detector location information.
Background technique
Positron e mission computed tomography (Positron Emission Tomography, abbreviation PET) technology
It is a kind of Radioactive isotope imaging technique, and most representative medicine imaging technique at present.In PET imaging system
In, the component of core is detector the most, which is used to detect the γ that the intracorporal radionuclide of introducing biology is issued and penetrates
Line, the crystal array and photoelectric converter being generally made of multiple crystal units are coupled to form, also known as scintillator detector.
In general, the detector that single crystal array and photoelectric converter are coupled to form is referred to as one in nuclear imaging system
The detector of detector module, whole system is made of multiple detector modules.In general, the formation of Solid-state pet detector system
Process are as follows: crystal units (crystal item) multiple first form crystal array, and subsequent crystal array is coupled with photodetector, are formed
One detector module, multiple detector modules are spliced into nearly cylindrical type (generally regular polygon) by certain technique again and visit
Survey device ring.When carrying out photon detection, the ray photons (such as γ photon) released in organism are incident on crystal, with crystal
It has an effect and generates fluorescence, fluorescence is converted into electric signal by photoelectric converter, for determining the incident crystal unit of γ photon,
The location information of crystal unit is registered as the incoming position information of γ photon, carries out image reconstruction according to the information, is given birth to
The transmitting image of object.It can be said that the accuracy of the location information of system detector unit directly affects the reconstruction knot of system
Fruit.
Ideally, each detector and crystal unit are installed in specific position designed by system in system, according to
The accurate location information of crystal unit can be obtained according to designed location information, to obtain the accurate location of incident photon
Information.However, there is some difference for manufacture craft or the physical characteristic meeting of crystal, in crystal array in practical manufacturing process
Crystal unit, different crystal arrays, be likely due between detector module to squeeze and processing technology it is imperfect
Deng, there are certain position gaps, cause location error, image reconstruction is carried out using the detector position information of inaccuracy, by
The image space that system can be seriously affected is differentiated, influences picture quality, causes image artifacts.
In the prior art scheme, generally pass through continuous improvement and improvement detector manufacture craft, detector Automatic manual transmission
The means such as technique reduce to the greatest extent and avoid the presence of error, thus provide detector cells location information accurate as far as possible, but
Various techniques realize that technical difficulty is big, at high cost, accuracy evaluation is difficult, do not have universality, influence it in PET imaging field
Application.
Summary of the invention
For the technical problems in the prior art, the purpose of the present invention is to provide a kind of measurement scintillator detectors
The method of location information.Method of the invention can accurately, easily obtain the physical location of PET imaging system detector cells
Parameter.
The purpose of the present invention is what is be achieved through the following technical solutions:
A method of measurement nuclear imaging system detector cells location information, the method are as follows:
Step 1: selection activity, shape, size positron radioactivity point source appropriate.
Activity: the activity of selected radioactive point source should make the counting loss of nuclear imaging system be less than or equal to 15%.This is
Since when the counting loss of nuclear imaging system is excessive, the system dead time influences seriously, and detector can not accurately measure ray light
Son, can not provide accurate detector position response message, lesser radioactive activity can make system since the dead time makes
At counting loss it is smaller or negligible, to not influence the accuracy that system positions photon；
Shape: the shape of point source can be spherical shape, the hexahedron or cylindrical linear of almost spherical etc.；
Size: no matter point source is above-mentioned any shape, is required to guarantee to meet the following conditions in the dimension of its minimum dimension:
The size in the dimension direction of point source minimum dimension should be very small compared with the size of detector cells, in general, should be less than or
Equal to the 1/5 of detector cells size；
Container: point source can be placed in certain container, it is preferred that use nonmetallic vessel, such as organic capillary glass tube,
Organic glass cube etc.；
Radioactive source: point source is positron radioactivity point source.
Step 2: along the central axis of PET imaging system, in certain axial range, making point source step motion, step-length
For Di, data are acquired in each location point i of point source, the acquisition duration of each location point i is Tacq,i, point source is recorded every
When a location point system acquisition to meet event.
When experiment, the smallest size of dimension direction of point source should be made consistent with PET central axis direction；
According to the activity size of the count rate performance of PET imaging system and selected radioactive activity point source, data are determined
Acquisition time Tacq,i, when guaranteeing that point source is placed in system central region, one group of detector cells of center face are in time Tacq,iIt is interior
It collects and meets event number with statistical significance, be such as not less than 1000；Acquisition duration of the point source in each location point i
It answers identical；
According to the accuracy requirement of calibration, point source axial direction single step stepping length D is determinedi；Stepping length is less than or equal to required
The precision to be calibrated；The distance D of each stepping of point sourceiIt may be the same or different, but above-mentioned condition should all be met；
, should be always along the central axis direction of PET system when point source movement, the axial range of movement is " L1+ axially regard
Wild range+L2", as shown in Figure 1, i.e. point source moves in the axial range of terminal A to terminal B, can be from above-mentioned axial fortune
One end A of dynamic range in axial direction moves to other end B, can also be from any position M in above-mentioned axial movement
Starting point, first from M step motion to one end A, then again from M step motion to other end B.The wherein L other than the axial visual field1With
L2Other than the axial visual field of system, L1And L2Length can be equal, can not also wait.L1And L2Length by PET system
The size decision of inherent spatial resolution, L1And L2The half of PET system inherent spatial resolution size cannot be shorter than.
Step 3: pick out suitable positron annihilation and meet event, obtain in the same ring of PET imaging system it is every it is a pair of just
To the axial point receptance function of detector cells.
Collected for each point source position to meet event, axial direction chooses the meet event vertical with PET axis, horizontal
Section direction, which is chosen, meets event by what the face probe unit of cross section central region was detected.
It is described meet event select can be in step 2 while acquisition while select, saved when can also acquire all
Meet event, then therefrom selects again；
For every a pair of of face detector cells in same ring, point source is recorded in each location point, is collected
Meet event number.Jth in i-th detector rings is denoted as D to the detector cells that face meetsij, point source moves to position
When point k, according to above-mentioned condition from DijThe event number that meets selected in event that meets of record is denoted as Cijk.To same axial rings
Any pair interior of face detector cells Dij, with the difference of point source position k, CijkValue corresponding variation, all the points occur
Collected C on the point of source positionijkJust face detector cells D is constitutedijAxial point receptance function, put in receptance function
Heart position is this axial centre position to face detector cells.Face detector cells DijAxial point receptance function be
DijWhat point acquired at various locations meets the distribution curve for meeting event number composition selected in event.
The detector cells can be a detector crystal unit (crystalline substance in perpendicular system axially direction
Body item), it is also possible to mechanically or physically belong to the crystal group of the same module.
Step 4: according to axial point receptance function, determining the physical location information of detector cells.
Theoretically, the peak position of the point receptance function obtained according to above-mentioned experimental method is corresponding face detector
The physical location of the responsing center of unit.Due to shadow that statistical counting, random signals, scattering meet etc. during actual experiment
It rings, leads in a receptance function that there are noises, influence the accuracy of peak position position.Therefore, peak is being determined according to a receptance function
When the position of position, noise according to circumstances can be first removed.Due to selecting the method for data stringenter in step 3, because
When removing noise, using the method for general removal noise, such as Gaussian smoothing filter.The present invention is directed to according to the above method
The axial point receptance function of every a pair of face detector cells in the same ring of the nuclear imaging system of acquisition, using filter function into
Row filtering and noise reduction, the axial point receptance function after obtaining filtering and noise reduction；After denoising, can directly it pass through after finding filtering and noise reduction
Axial point receptance function maximum value, the position of peak value is determined by the position of maximum value, can also be using Gauss curve fitting, secondary
The modes such as Function Fitting find peak position of the peak position of fitting function as point receptance function.Point determined above
The peak position of receptance function is the physical location of the responsing center of corresponding face detector cells.
Since the positive electron in positron emission source is buried in oblivion with negative electron, the photon of generation is a pair of back-to-back γ photon
It is right, that is, meet photon with auto-collimation effect, therefore, only point source face detector when, detector is likely to detect most
More meets event.To sum up, the physical location of the point responsing center of each pair of face detector cells is this in axial same ring
To the system axial physical location of detector cells.
Compared with prior art, the positive effect of the present invention
The present invention provides a kind of method for measuring scintillator detector location information, this method can be accurate, convenient and fast
Obtain the physical location parameter of PET imaging system detector cells.
Detailed description of the invention
Fig. 1 is point source step motion range schematic diagram；
Fig. 2 is method flow schematic diagram provided in an embodiment of the present invention.
Specific embodiment
The following is a clear and complete description of the technical scheme in the embodiments of the invention, it is clear that described embodiment
Only a part of the embodiment of the present invention, instead of all the embodiments.Based on the embodiment of the present invention, ordinary skill
Personnel's every other embodiment obtained without making creative work, belongs to protection scope of the present invention.
Implementation of the invention will be described in detail by taking an animal PET as an example below.
The crystal array of each detector module is made of 16 × 16 scintillation crystals in the animal PET, every crystal
Having a size of 1.9mm × 1.9mm × 10mm, two detector arrays, which are listed in, is axially formed a group (Module), and 24 groups
(Module) detector forms 20 quadrangles in cross section, i.e., entire panel detector structure is the nearly cylinder of 32 ring of axial direction
Type panel detector structure, the smallest probe unit is having a size of 1.9mm.
It is used when experiment22Na point source, point source radiation activity are that the radioactive activity of 2.96MBq (80uCi) radioactive point source is big
For counting loss caused by the small dead time that can make system less than 5%, random signals rate is less than the 5% of gross-count rate.Point source is big
Small is 0.2mm, is sealed in the acrylic cube body that size is 10.0mm.
When experiment, point source is placed in system cross section central region.Position with 5mm outside the axial vision periphery of distance is
Initial point steps to the position of 5mm outside the system axial other end visual field along system centre axis, and the step-length of every step is 0.2mm,
Single step acquisition time is 2min, i.e., in the present embodiment:
L1=L2=5mm
Tacq,i=2min
Di=0.2mm
Storage point source moves to the data acquired when each location point, is organized as the format of sinogram.?
The meet event vertical with PET axis is first sorted out in sinogram data, i.e., axial face meets event, is then selecting again
Cross section is chosen in data out meets event by what the face probe unit of central region was detected.
PET imaging system in the present embodiment makes in individual module and is formed in the technique of detector rings, mechanical
On can guarantee the precision of submillimeter, thus in the present embodiment, pay close attention to the physical location of system axial detector cells.
When forming the axial point receptance function of axial each detector cells pair, the event of cross-sectional direction is not independent in tissue
Crystal unit is distinguished, modules are only distinguished.This have the advantage that can obtain statistical higher in a relatively short period of time
Data.Thus in the same axial rings of system, the point extended response function of 12 pairs of face detector cells can be obtained, it is entire to be
System can obtain the point extended response function of the detector cells of 12 × 32 pairs of faces.
For the axial point receptance function of acquisition, the peak position information of each function is obtained by the way of Gauss curve fitting, with
This responsing center as corresponding face detector cells, the as physical location of detector cells.
The foregoing is only a preferred embodiment of the present invention, but scope of protection of the present invention is not limited thereto,
Within the technical scope of the present disclosure, any changes or substitutions that can be easily thought of by anyone skilled in the art,
It should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with the protection model of claims
Subject to enclosing.
Claims (10)
1. a kind of method for measuring scintillator detector location information, step include:
1) a positron radioactivity point source is chosen；
2) along the central axis of nuclear imaging system, in the axial range of setting, make the positron radioactivity point source movement, remember
It records the positron radioactivity point source nuclear imaging system is collected in each setting position point and meet event；
3) it is rung from the axial point for meeting every a pair of of face detector cells in the selection same ring of nuclear imaging system in event of acquisition
Answer function；
4) according to the axial point receptance function, the physical location information of detector cells is determined.
2. the method as described in claim 1, which is characterized in that the activity of the positron radioactivity point source should make nuclear imaging system
The counting loss of system is less than or equal to 15%.
3. method according to claim 1 or 2, which is characterized in that the size of the positron radioactivity point source is less than or waits
In the 1/5 of detector cells size；The positron radioactivity point source is spherical shape, and is placed in a nonmetallic vessel.
4. the method as described in claim 1, which is characterized in that when step motion, the size of the positron radioactivity point source
The smallest dimension direction is consistent with the central axis direction.
5. the method as described in claim 1, which is characterized in that, adjacent bit identical in the acquisition duration of each location point
Set the distance between be a little respectively less than or equal to required calibration precision；In each position, point, which is collected, meets event number and has
Statistical significance.
6. the method as described in claim 1, which is characterized in that choose the method that positron annihilation meets event are as follows: for every
A point source position is collected to meet event, chooses axially vertical with nuclear imaging system and is being passed through cross section central region just
Meet event to what probe unit was detected.
7. the method as described in claim 1, which is characterized in that the method for obtaining the axial point receptance function are as follows: by core at
As the jth in system in the i-th detector rings is denoted as D to the detector cells that face meetsij, from DijIt is acquired in k-th of location point
The event number that meets selected in event that meets be denoted as Cijk；According to from DijMeeting in event for point acquisition chooses at various locations
The event number that meets chosen constitutes face detector cells DijAxial point receptance function.
8. method as claimed in claim 1 or 7, which is characterized in that the method for determining the physical location information of detector cells
Are as follows: in the step 4), letter is responded to the axial point of a pair of face detector cells every in the same ring of the nuclear imaging system of acquisition
Number carries out noise remove, using the peak position of each axial point receptance function after removal noise as corresponding face detector
The physical location of the responsing center of unit.
9. the method as described in claim 1, which is characterized in that the axial range set is the nuclear imaging system axial direction visual field
A distance L before range1A distance L to nuclear imaging system axial direction field range2；L1And L2It is not shorter than core
The half of imaging system inherent spatial resolution size.
10. the method as described in claim 1~9 is any, which is characterized in that the nuclear imaging system is PET system.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112656439A (en) * | 2020-12-18 | 2021-04-16 | 华中科技大学 | Position decoding method and system for positron emission imaging |
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