CN109350099A - A kind of chance event removal processing method applied to clinical PET system - Google Patents
A kind of chance event removal processing method applied to clinical PET system Download PDFInfo
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- 238000002591 computed tomography Methods 0.000 claims description 3
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Abstract
The invention discloses a kind of chance events applied to clinical PET system to remove processing method, includes two kinds of fast and convenient concrete methods of realizing in this method, that is, optimizes three-dimensional minimizing technology and fast two-dimensional minimizing technology.The present invention has the following advantages and effects: (1) invalid random coincidence event can be removed and be up to 75%.(2) the calculating time that removal meets event in vain is optimized, data processing speed is improved.(3) background noise is reduced.
Description
Technical field
The present invention relates to medical image processing technical fields, more specifically, are related to a kind of applied to clinical PET system
Chance event removes processing method.
Background technique
Positron Emission Computed Tomography (Positron Emission Tomography, abbreviation PET) is to pass through
To human injection's radioactive tracer drug, with specific cells or tissue certain bioprocess occurs for drug in human body, passes through
To the gamma-ray detection of a pair that radionuclide decay generates, to obtain radiopharmaceutical in the intracorporal distribution map of people.
The positive electron that positron radionuclide in PET is generated by decay can fall into oblivion with existing negative electrons a large amount of in human body
It goes out, to generate the γ photon of a pair of reversed approximate 180 degree.The line received between the detector of the two γ photons is referred to as
Meet line (line of response, abbreviation LOR).If two γ photon sources being detected are in the same electron annihilation
Event and wherein at least one photon is scattered with medium, this event are referred to as scattering and meet.If detect two
A photon is derived from two different annihilation events, this event is referred to as random coincidence.
Square directly proportional, and true coincidence counting rate and the system counting rate of random coincidence counting rate and system counting rate
First power it is directly proportional.So when activity is higher, or the PET system long in the covering of the axial visual field, random coincidence event become
One seriously affects the factor of PET image quality, so that PET quantitative analysis be made to lose meaning.Accurately to random coincidence event
Correction be PET system image procossing a key technology.
With being widely used for fast blink crystal and answering for flying time technology (time of flight, TOF)
With can more accurately estimate generation position of each true coincidence event on LOR.Also useless farthest to remove simultaneously
Chance event provide new method.Useless chance event bring benefit is removed before image reconstruction two aspects,
(1) counting for reducing useless event, improves the speed of data processing image reconstruction, (2) farthest reduce ambient noise, mention
High image quality.
The method for removing and correcting relative to existing random signal, this method are schemed according to the CT or MR of each scanning human body
Picture can farthest utilize the temporal resolution performance of PET system, to farthest remove useless Random event
Part is preferably minimized influence of the random signal to picture quality.It also proposed a fast and convenient implementation method simultaneously, it can be with
Receive range according to the time window that each scanning human body calculates each LOR in real time.
Summary of the invention
It is applied to face for the acquisition of PET system list type (List mode) data the object of the present invention is to provide a kind of
The chance event of bed PET system removes processing method, and this method can be fast and convenient or effectively removes useless chance event,
The speed of data processing image reconstruction is improved, and utmostly reduces ambient noise, improves picture quality.
Above-mentioned technical purpose of the invention has the technical scheme that a kind of applied to clinic PET system
The chance event of system removes processing method, includes the following steps, Step 1: being examined using same period scanning computed tomography image or MRI image
Survey the body region of scanning patient；Step 2: extracting location information (a pair of of detector d of each LOR event1And d2), it determines
Whether this LOR intersects with the body region prestored, and the disjoint LOR of body region for rejecting and prestoring；Step 3: will with it is pre-
The LOR for the body region intersection deposited is according to the two point p intersected with body region1And p2, two points are calculated to d1And d2Time
Difference is denoted as T respectively1And T2, read the time difference information T of this LOR recorddiff, judge this LOR whether in effective time difference range
It is interior effective, reject the LOR not in effective range；Step 4: being retained in the LOR in effective range, and carry out Data correction, figure
As reconstruction and post-processing operation.
It is further arranged to: in step 1, image preprocessing being carried out (by PET and CT or MRI to scanning result after scanning
Image registration and dimension correction), bed board and bracket removal, threshold value optimize selections, image binaryzation, boundary profile extraction with
And contour images filling, post processing of image (expansion, corrosion).
It is further arranged to: in step 2, before the location information for extracting LOR event, by patient's 3D CT image in axial direction
It is cumulative to form two-dimentional body region figure, and calculate two-dimentional body contour figure；After the location information for extracting LOR event, LOR is calculated
Projection on two-dimentional cross section.
Be further arranged to: the time difference effective range in step 3 is T1-nσ-ε≤Tdiff≤T2+nσ+ε。
In conclusion the invention has the following advantages:
(1) invalid random coincidence event can be removed and be up to 75%.
(2) the calculating time that removal meets event in vain is optimized, data processing speed is improved.
(3) background noise is reduced.
Detailed description of the invention
Fig. 1 is that list type data random signal of the invention removes flow chart；
Fig. 2 is the treatment process of picture of the present invention；
Fig. 3 is the schematic diagram of three-dimensional optimized minimizing technology of the present invention；
Fig. 4 is the schematic diagram of embodiment fast two-dimensional minimizing technology；
Fig. 5 is using the reconstruction image (background parts) after processing method of the present invention；
Fig. 6 is using the reconstruction image (body part) after processing method of the present invention.
Specific embodiment
Below in conjunction with Fig. 1 to Fig. 5, invention is further described in detail.
Embodiment one, three-dimensional optimized minimizing technology: one kind is acquired for PET system list type (List mode) data, and
Chance event applied to clinical PET system removes processing method, including following operating procedure, step 1 are swept using the same period
Retouch the body region of CT image or MRI image detection scanning patient；Step 2 carries out image preprocessing to the image scanned
(by PET be registrated with CT or MRI image and dimension correction), bed board and bracket removal, threshold value optimize choose, image two-value
Change, boundary profile extracts and contour images filling, post processing of image (expansion, corrosion)；Step 3 extracts each LOR thing
The location information of part, determines whether this LOR intersects with the body region prestored, if do not intersected with the body region prestored,
Reject part LOR；If part LOR intersects with the body region prestored, intersected according to part LOR with body region
Two point p1And p2, two points are calculated to d1And d2Time difference, be denoted as T respectively1And T2, read the time difference of this LOR record
Information Tdiff, judge whether this LOR is effective within the scope of effective time difference, which is T1-nσ-ε≤Tdiff≤
T2+ n σ+ε, wherein σ is related to system timing resolution, and σ=FWHMtiming/2.355, n usually takes between 2 ~ 3, and ε is due to suffering from
Person body is mobile and bring error.The not LOR in time difference effective range is rejected, is retained in time difference effective range
LOR.Step 4 carries out Data correction, image reconstruction and post-processing operation, output to the LOR in effective range of reservation
As a result.
Embodiment two, fast two-dimensional minimizing technology: the embodiment is roughly the same with embodiment one, and difference is in step 2
In, before the location information for extracting LOR event, first by patient 3D CT image in the axially two-dimentional body region figure of cumulative formation, and
Calculate two-dimentional body contour figure.The location information of LOR event is then extracted again.After the location information for extracting LOR event
Need to calculate projection of the LOR on two-dimentional cross section；After extracting LOR, LOR is intersected with the two-dimentional body region prestored to sentence
It is disconnected whether to need to reject part LOR.
Table 1 by the 70cm radial direction visual field, the 40cm axial direction visual field PET scan frame for, for 30cm diameter, 40cm length
Water mould, the ratio of this method removal random coincidence event is up to 75%, and the influence to effective true coincidence event only has
0.23%。
The removal of 1 random coincidence event invalid data of table is compared
| It counts | True coincidence event | Random coincidence event |
| A before removing | 51,991,822 | 43,785,697 |
| B after removal | 51,872,166 | 11,062,411 |
| Removal percentage (a-b)/a × 100% | 0.23% | 74.74% |
Fig. 5 and Fig. 6 is the same die body figure after rebuilding, by adjusting display tonal range, Fig. 5 saliency air background portion
Point, Fig. 6 shows die body activity region.The method of the present invention can almost remove air background noise, living simultaneously for die body
There was only small influence in degree region.
The mean activity value of area-of-interest (ROI) in Fig. 5 and Fig. 6 is shown in table 2.In activity region, difference is only
Have 0.23%, and air background part, this method almost all remove ambient noise.
2 area-of-interest activity value of table compares
| ROI activity value | Body part | Background parts |
| A before removing | 123.7369 | 0.2761 |
| B after removal | 123.9419 | 1.9E10-7 |
| Relative different (Shu a-b Shu/a) * 100% | 0.16% | 99.99% |
This specific embodiment is only explanation of the invention, is not limitation of the present invention, and those skilled in the art exist
It can according to need the modification that not creative contribution is made to the present embodiment after reading this specification, but as long as in the present invention
Scope of the claims in all by the protection of Patent Law.
Claims (4)
1. a kind of chance event applied to clinical PET system removes processing method, it is characterised in that: include the following steps,
Step 1: utilizing same period scanning computed tomography image or the body region of MRI image detection scanning patient；
Step 2: extracting location information (a pair of of detector d of each LOR event1And d2), determine this LOR whether with prestore
Body region intersection, and the disjoint LOR of body region for rejecting and prestoring；
Step 3: by the LOR intersected with the body region prestored according to the two point p intersected with body region1And p2, calculate two
A point is to d1And d2Time difference, be denoted as T respectively1And T2, read the time difference information T of this LOR recorddiff, whether judge this LOR
Within the scope of effective time difference effectively, the LOR not in effective range is rejected；
Step 4: being retained in the LOR in effective range, and carry out Data correction, image reconstruction and post-processing operation.
2. a kind of chance event applied to clinical PET system according to claim 1 removes processing method, feature exists
In: in step 1, image preprocessing is carried out to scanning result after scanning and (is registrated PET and dimension correcting with CT or MRI image
Just), bed board and bracket removal, threshold value optimize selection, image binaryzation, boundary profile extraction and contour images filling, figure
As post-processing (expansion, corrosion).
3. a kind of chance event applied to clinical PET system according to claim 1 removes processing method, feature exists
In: in step 2, before the location information for extracting LOR event, patient 3D CT image is formed into two-dimentional body region axially cumulative
Domain figure, and calculate two-dimentional body contour figure；After the location information for extracting LOR event, throwing of the LOR on two-dimentional cross section is calculated
Shadow.
4. a kind of chance event applied to clinical PET system according to claim 1 removes processing method, feature exists
In: the time difference effective range in step 3 is T1-nσ-ε≤Tdiff≤T2+nσ+ε。
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109998582A (en) * | 2019-04-15 | 2019-07-12 | 上海联影医疗科技有限公司 | Coincidence judging and selecting method, device, equipment and medium |
| CN112102426A (en) * | 2020-08-28 | 2020-12-18 | 上海联影医疗科技股份有限公司 | Background coincidence event judging and selecting method, device, equipment and readable storage medium |
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| CN109998582A (en) * | 2019-04-15 | 2019-07-12 | 上海联影医疗科技有限公司 | Coincidence judging and selecting method, device, equipment and medium |
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| CN112102426A (en) * | 2020-08-28 | 2020-12-18 | 上海联影医疗科技股份有限公司 | Background coincidence event judging and selecting method, device, equipment and readable storage medium |
| CN112102426B (en) * | 2020-08-28 | 2024-03-26 | 上海联影医疗科技股份有限公司 | Background coincidence event judging and selecting method, device and equipment and readable storage medium |
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Application publication date: 20190219 |