CN115299976A - Multi-gamma photon coincidence imaging system and method - Google Patents
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Abstract
The system comprises a time coincidence module, a computer platform, at least two slit collimators with different collimating slit sizes, at least two hole collimators with different collimating holes sizes, a plurality of gamma photon detectors and a driving component for driving the corresponding slit collimators or the slit collimators to change the size of an imaging range; the imaging method reduces the position range of the radionuclide decays to the intersection point of a projection plane determined by gamma photon events detected by a gamma photon detector through a collimation slit and a projection line determined by gamma photon events detected by a gamma photon detector through a collimation hole in a multi-gamma photon coincidence event within the imaging range, so as to obtain the distribution of the radionuclide within the detected range. The multi-gamma-photon coincidence imaging system realizes the performance optimization of the multi-gamma-photon coincidence imaging system on the imaging objects with different sizes, and improves the image space resolution of the imaging of the small-size imaging objects.
Description
Technical Field
The disclosure belongs to the technical field of emission tomography, and particularly relates to a multi-gamma photon coincidence imaging system and method.
Background
Emission tomography is one of the important techniques for detecting internal information of an object today and has numerous applications in a variety of research fields. The gamma photons emitted from the detected object are detected outside the detected object, and the internal information of the detected object is obtained through image reconstruction and non-invasive means observation. In the field of emission tomography, the most important imaging systems include a Positron Emission Tomography (PET), a Single-photon emission computed tomography (SPECT), and a compton camera (compton camera), respectively. Both PET and SPECT are now widely used for clinical examination and diagnosis, including cancer, neurological and cardiovascular diseases, etc., while compton cameras are also used in the nuclear power industry, astronomy, medical, etc.
The applicant has proposed a multi-gamma photon coincidence imaging system and method (application number: 202010465659. X) based on a slot hybrid collimator, the system comprises a plurality of detector probes arranged in a non-parallel manner, a time coincidence module and a computer platform, each detector probe is composed of a slot hybrid collimator and a gamma photon detector with a time measurement function, and a plurality of gamma photons emitted by a detection radionuclide in a short time form a multi-gamma photon coincidence event; the method reduces the position range of radionuclide decay to a plurality of intersection points of a plurality of projection planes determined by gamma photon events detected by a gamma photon detector through a collimation slit and a plurality of projection lines determined by gamma photon events detected by a gamma photon detector through a collimation hole in a multi-gamma photon coincidence event in an imaging range so as to obtain the distribution of the radionuclide in the measured range. The imaging system and the imaging method improve the detection efficiency of multi-gamma photon coincidence events and improve the signal-to-noise ratio of the reconstructed image, thereby reducing the requirement on the total gamma photon counting, improving the signal-to-noise ratio of the reconstructed image and reducing the irradiation risk of patients. However, the imaging range and imaging performance of the system are single, and the imaging range cannot be adjusted according to the size of an imaging object, so that the spatial resolution of a reconstructed image is poor when the imaging object is small.
Disclosure of Invention
The present disclosure is directed to solving, at least to some extent, one of the technical problems in the related art.
To this end, it is an object of the present disclosure to provide a multi-gamma photon coincidence imaging system that uses multiple sets of aperture collimators to change the size of the imaging field, adjust the imaging field of view, and improve the spatial resolution of the reconstructed image of a small imaging subject by shifting out the collimators of different sizes.
In order to achieve the purpose, the following technical scheme is adopted in the disclosure:
the embodiment of the first aspect of the present disclosure provides a multi-gamma photon coincidence imaging system, which includes a time coincidence module, a computer platform and a plurality of heterogeneous probes; the plurality of different types of probes comprise at least one first probe and at least one second probe, the first probe is composed of at least two hole collimators which are parallel to each other and a first gamma photon detector with a time measurement function, the second probe is composed of at least two slit collimators which are parallel to each other and a second gamma photon detector with a time measurement function, each hole collimator and each slit collimator are formed by respectively forming at least one collimation hole and at least one collimation slit on a respective alloy plate, the collimation holes of each hole collimator in the first probe are different in size, the collimation slits of each slit collimator in the second probe are different in size, each hole collimator and each slit collimator are respectively controlled by a corresponding driving part, so that one hole collimator in each first probe and one slit collimator in each second probe are positioned between the front end of the corresponding gamma photon detector and the imaging object and positioned in the detection range of the corresponding gamma photon detector, and the rest hole collimators in each first probe and each second collimator are positioned outside the detection range of the corresponding gamma photon detector, and the rest of the gamma photon detectors in the other detection slits are not capable of generating radioactive decay through the gamma photon detectors of radioactive nuclides of the imaging photon detectors; time signal lines of all the gamma photon detectors are connected with the time coincidence module, a time window set by the time coincidence module is used for judging whether a plurality of gamma photon events detected by a plurality of probes respectively form a multi-gamma photon coincidence event or not, and the judgment result is input into the computer platform; energy and position signal lines of all the gamma photon detectors are also simultaneously connected with the computer platform and are used for judging the effectiveness of the multi-gamma photon coincidence event and calculating the intersection point of a projection line where the occurrence position of the multi-gamma photon coincidence event is possibly located and the projection line in an imaging range, so that the possible position of the radionuclide when decay occurs is obtained; and obtaining the possible distribution of the radioactive nuclide in the imaging object body according to the possible positions of all the radioactive nuclides when decay occurs, and estimating the distribution more accurately through an image reconstruction algorithm.
In some embodiments, neither the first gamma photon detector nor the second gamma photon detector has a width or length less than
D is the size of the imaging object, a is the distance from the surface of the hole collimator or the slit collimator to the corresponding surface of the gamma photon detector, and b is the distance from the center of the imaging object to the surface of the hole collimator or the slit collimator.
In some embodiments, the probing planes of the first and second probes are arranged in a non-parallel arrangement.
In some embodiments, when a plurality of the first probes and a plurality of the second probes are provided, the first probes and the second probes are alternately arranged, and the probing planes of the first probes and the probing planes of the second probes are arranged in a non-parallel manner.
In some embodiments, the aperture collimators and the slit collimators employ flat plate collimators and/or curved surface collimators.
In some embodiments, the curved collimator is a closed or an open curved collimator.
In some embodiments, the drive component is a robotic arm or a drive motor.
In some embodiments, the drive component controls the translation of the respective aperture collimator or slit collimator in the height direction of the imaging subject.
In some embodiments, the radionuclide, in its decay process, can produce at least two gamma photons in a cascade fashion in a very short time.
The multi-gamma photon coincidence imaging system provided by the embodiment of the first aspect of the disclosure has the following characteristics and beneficial effects:
the multi-gamma photon coincidence imaging system provided by the embodiment of the first aspect of the disclosure effectively overcomes the defects of fixed imaging range and single performance of the traditional SPECT, PET and the proposed multi-gamma photon coincidence imaging system. The embodiment of the disclosure uses a plurality of sets of hole collimators and slit collimators, and the imaging range and the imaging spatial resolution are adjusted by moving out the hole collimators and the slit collimators with different sizes, so that the imaging performance of the imaging objects with different sizes is improved.
Another objective of the present disclosure is to provide an imaging method using the above multi-gamma photon coincidence imaging system, comprising:
(1) Starting the multi-gamma photon coincidence imaging system, and setting the time window width of a time coincidence module; setting an energy window of each gamma photon detector according to the gamma photon energy radiated by the used radionuclide;
(2) According to the size of an imaged object, the corresponding hole collimator and the corresponding slit collimator are moved to the detection range of the corresponding gamma photon detector by using the driving part, and the rest hole collimators and the rest slit collimators are moved out of the detection range of the corresponding gamma photon detector;
(3) The computer platform judges whether the imaging process is finished according to the set acquisition time; if so, executing the step (6); if not, executing the step (4);
(4) The time coincidence module judges whether each gamma photon detector detects a multi-gamma photon coincidence event, if so, the step (5) is executed; if not, executing the step (3);
(5) The computer platform judges whether the input gamma photon energy is respectively in the set energy windows according to the gamma photon energy information input by each gamma photon detector; if not, discarding the multi-gamma-photon coincidence event; if the gamma photon coincidence events are in the set energy window, calculating a plurality of projection planes where the occurrence positions of the gamma photon coincidence events are located according to the position information of one gamma photon input by each gamma photon coincidence event in the first gamma photon detector, and calculating a plurality of projection lines where the occurrence positions of the gamma photon coincidence events are located according to the position information and the energy information of one gamma photon input by each gamma photon coincidence event in the second gamma photon detector; recording a plurality of projection planes and a plurality of corresponding intersection points of a plurality of projection lines in the imaging object respectively determined by a plurality of gamma photons in each multi-gamma photon coincidence event as a plurality of possible positions of radionuclide decay; executing the step (3);
(6) And obtaining the possible distribution of the radionuclide in the imaging object according to the plurality of possible decay positions of the radionuclide calculated according to all the multi-gamma photon coincidence events, and performing more accurate estimation on the distribution through an image reconstruction algorithm.
Drawings
The above and/or additional aspects and advantages of the present disclosure will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic overall structural diagram of an imaging system including 4 first probes and 4 second probes according to an embodiment of the present disclosure;
fig. 2 (a) and (b) are schematic structural diagrams of the first plate hole collimator and the first plate slit collimator, respectively, in the imaging system shown in fig. 1;
fig. 3 (a) and (b) are respectively schematic structural diagrams of a second plate hole collimator and a second plate slit collimator in the imaging system shown in fig. 1;
fig. 4 is a block flow diagram of an imaging method according to an embodiment of the disclosure.
In the figure: 1-a first hole collimator, 11-a first collimation hole, 12-an alloy flat plate of the first hole collimator, 2-a first slit collimator, 21-a first collimation slit, 22-an alloy flat plate of the first slit collimator, 3-a second hole collimator, 31-a second collimation hole, 32-an alloy flat plate of the second hole collimator, 4-a second slit collimator, 41-a second collimation slit, 42-an alloy flat plate of the second slit collimator, 51-a first gamma photon detector, 52-a second gamma photon detector, 6-a time coincidence module, 7-a computer platform, 8-a first imaging range, 9-a second imaging range, and 10-a decay possible position.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of and not restrictive on the broad application.
On the contrary, this application is intended to cover any alternatives, modifications, equivalents and variations that may be included within the spirit and scope of the application as defined by the appended claims. Furthermore, in the following detailed description of the present application, certain specific details are set forth in order to provide a better understanding of the present application. It will be apparent to one skilled in the art that the present application may be practiced without these specific details.
The multi-gamma photon coincidence imaging system provided by the embodiment of the first aspect of the disclosure comprises a time coincidence module, a computer platform, a plurality of driving components and a plurality of probes of different types; the plurality of probes of different types comprise at least one first probe and at least one second probe, each first probe is respectively composed of at least two hole collimators which are parallel to each other and a first gamma photon detector with a time measurement function, each second probe is respectively composed of at least two slit collimators which are parallel to each other and a second gamma photon detector with a time measurement function, each hole collimator and each slit collimator are formed by respectively forming at least one collimation hole and at least one collimation slit on a respective alloy plate, the collimation holes of the hole collimators in the first probe are different in size, the collimation slits of the slit collimators in the second probe are different in size, each hole collimator and each slit collimator are respectively controlled by a corresponding driving part, so that one hole collimator in each first probe and one slit collimator in each second probe are positioned between the front end of the corresponding gamma photon detector and the imaging object and positioned in the corresponding gamma photon detector range, and the other hole collimators in each first probe and one slit collimator in each second probe are positioned outside the corresponding gamma photon detector, and the gamma photon detectors in the other collimator in the corresponding gamma photon detector are not capable of generating radioactive decay through the photon detectors of emitting photons; the time signal lines of all the gamma photon detectors are connected with the time coincidence module, and a time window set by the time coincidence module is used for judging whether a plurality of gamma photon events detected by a plurality of probes (including a first probe and a second probe) form a multi-gamma photon coincidence event or not and inputting the judgment result into a computer platform; energy and position signal lines of all gamma photon detectors are also simultaneously connected with a computer platform and are used for judging the effectiveness of the multi-gamma photon coincidence events and calculating intersection points of projection surfaces where the positions of the multi-gamma photon coincidence events possibly exist and projection lines in an imaging range, so that the possible positions of the radioactive nuclides when the radioactive nuclides decay are obtained; and obtaining the possible distribution of the radioactive nuclide in the imaging object according to the possible decay positions of all the radioactive nuclides, and performing more accurate estimation on the distribution through an image reconstruction algorithm.
In some embodiments, each gamma photon detector has a width and length that are both no less than
D is the size of the imaging object, a is the distance from the surface of the hole collimator or the slit collimator to the surface of the corresponding gamma photon detector, and b is the distance from the center of the imaging object to the surface of the hole collimator or the slit collimator, so that gamma photons emitted from all positions in the imaging object with the size of D can be detected by the gamma photon detector.
In some embodiments, the probing planes of the first probe and the second probe are arranged in a non-parallel arrangement therebetween. When a plurality of first probes and a plurality of second probes are provided, the first probes and the second probes are alternately arranged, and the respective first probes and the respective second probes are arranged in a uniformly distributed manner or a non-uniformly distributed manner on the periphery of the imaging subject.
In some embodiments, according to the imaging requirements (imaging size and imaging resolution requirements) of the imaging object, the hole collimator and the slit collimator of corresponding sizes are located in the detection range of the corresponding gamma photon detector by the driving component, and the rest hole collimators and the slit collimator are moved to the detection range of the corresponding gamma photon detector, so that the performance optimization of the multi-gamma photon coincidence imaging system for the imaging objects of different sizes is realized, and the image space resolution for imaging the imaging objects of different sizes (especially small-sized imaging objects) is improved.
Further, each driving unit controls the corresponding hole collimator or slit collimator to translate in the height direction of the imaging object for compactness.
Further, each driving part adopts a mechanical arm or a linear servo motor.
In some embodiments, the alloy plate of each of the hole collimator and the slit collimator may be a flat plate or a curved plate, and when a hole flat plate collimator is used, one or more alignment holes may be formed thereon, and when a hole curved plate collimator (e.g., a closed or non-closed hole cylindrical collimator) is used, one alignment hole (in this case, a non-closed hole curved plate collimator is used) or a plurality of alignment holes (in this case, a closed or non-closed hole curved plate collimator may be used, and the distances between adjacent alignment holes may be the same or different); when a slit plate collimator is used, one collimating slit or a plurality of collimating slits can be formed on the slit plate collimator, and when a slit curved plate collimator (such as a closed or non-closed slit cylindrical surface collimator) is used, one collimating slit (at this time, a non-closed slit curved plate collimator needs to be used) or a plurality of collimating slits (at this time, a closed or non-closed slit curved plate collimator can be used, and the distance between every two adjacent collimating slits is the same or different). The distance d between adjacent collimation holes and collimation slits meets the following requirements: d ≧ D a/(a + b), where D is the size of the imaged object, a is the distance from the surface of the slot hybrid collimator to the surface of the gamma photon detector, and b is the distance from the center of the imaged object to the surface of the aperture collimator or the slot collimator.
In some embodiments, the radionuclide can generate at least two gamma photons in a cascade fashion in a very short time during its decay.
A multi-gamma photon coincidence imaging system proposed according to an embodiment of the present disclosure is described below with reference to fig. 1 to 3.
Referring to fig. 1, the multi-gamma photon coincidence imaging system of the present embodiment is composed of a time coincidence module 6, a computer platform 7, and 4 first probes and 4 second probes which are alternately and uniformly arranged circumferentially. Each first probe is composed of a first gamma photon detector 51, a first hole collimator 1 and a second hole collimator 3 which are parallel to each other and are sequentially arranged from outside to inside at intervals, and each second probe is composed of a second gamma photon detector 52, a first slit collimator 2 and a second slit collimator 4 which are parallel to each other and are sequentially arranged from outside to inside at intervals. Referring to fig. 2 (a), (b), the first hole collimator 1 is formed by forming a first collimating hole 12 in an alloy flat plate 11, and the first slit collimator 2 is formed by forming a first collimating slit 22 in an alloy flat plate 21. Referring to fig. 3 (a) and (b), the second hole collimator 3 is formed by forming a second collimating hole 32 in an alloy plate 31, and the size of the second collimating hole 32 is smaller than that of the first collimating hole 12, and the second slit collimator 4 is formed by forming a second collimating slit 42 in an alloy plate 41, and the size of the second collimating slit 42 is smaller than that of the first collimating slit 22. When all the second hole collimators 3 are moved out of the detection range of the corresponding first gamma photon detector 51 and all the second slit collimators 4 are moved out of the detection range of the corresponding second gamma photon detector 52 in the direction perpendicular to the paper plane shown in fig. 1 by a driving unit (the driving unit is a mechanical arm, not shown in the figure, and each collimator is controlled by a corresponding mechanical arm), each of the first hole collimators 1 and the first slit collimators 2 is in the detection range of the corresponding gamma photon detector, and the imaging range of the system is the first imaging range 8, gamma photons generated by decay of radioactive nuclides in the imaging object located in the first imaging range 8 are detected by the first gamma photon detector 51 and the second gamma photon detector 52 through the first hole collimator 1 and the first slit collimator 2. When all the first hole collimators 1 are moved out of the detection range of the corresponding first gamma photon detector 51 and all the first slit collimators 2 are moved out of the detection range of the corresponding second gamma photon detector 52 by the driving component along the direction perpendicular to the paper surface shown in fig. 1, each of the second hole collimators 3 and the second slit collimators 4 is in the detection range of the corresponding gamma photon detector, the imaging range of the system is the second imaging range 9, and gamma photons generated by decay of radioactive nuclides in the imaging object located in the second imaging range 9 are detected by the first gamma photon detector 51 and the second gamma photon detector 52 through the second hole collimators 3 and the second slit collimators 4. The time signal lines of the 4 first gamma photon detectors 51 and the 4 second gamma photon detectors 52 are all connected to the time coincidence module 6, and the time coincidence module 6 sets a time window with a certain width (the time window width is adjustable according to the adopted radionuclide and is usually within hundreds of nanoseconds) for determining whether the two gamma photon events detected by the two gamma photon detectors respectively constitute a double gamma photon coincidence event, and inputting the corresponding determination result into the computer platform 7, specifically: if the time signals of the two photons from the first gamma photon detector 51 and the second gamma photon detector 52 are not in the set time window, it is determined that the two gamma photon events do not form a double gamma photon coincidence event, and the two events are discarded; if the time signals of the two photons from the first gamma photon detector 51 and the second gamma photon detector 52 are within the set time window, it is determined that the two gamma photon events constitute a double gamma photon coincidence event, and the corresponding determination result is input into the computer platform 7, and the energy and position information of the gamma photons measured by the first gamma photon detector 51 and the second gamma photon detector 52 are transmitted to the computer platform 7. The energy and position information is used for judging the effectiveness of the multi-gamma photon coincidence event and calculating the intersection point of a projection plane where the multi-gamma photon coincidence event possibly exists and a projection line in an imaging range in the computer platform 7, and the possible decay position 10 of the radionuclide is directly obtained; from the possible positions of decay 10 of all the radionuclides, the possible distribution of the radionuclide in the imaging subject can be obtained and can be estimated more accurately by image reconstruction algorithms.
In this embodiment, the distance from the first aperture collimator 1 to the surface of the corresponding first gamma photon detector 51 and the distance from the first slit collimator 2 to the surface of the corresponding second gamma photon detector 52 are both 14.5mm, the distance from the center of the imaging object to the surfaces of the first aperture collimator 1 and the first slit collimator 2 is both 58.0mm, the distance from the second aperture collimator 3 to the surface of the corresponding first gamma photon detector 51 and the distance from the second slit collimator 4 to the surface of the corresponding second gamma photon detector 52 are both 40.7mm, the distance from the center of the imaging object to the surfaces of the second aperture collimator 3 and the second slit collimator 4 is both 31.8mm, the size of the first imaging range 8 is 10cm, the size of the second imaging range 9 is 3.5cm, and the size of each imaging range is the size of the corresponding imaging object.
The first hole collimator 1, the first slit collimator 2 (as shown in fig. 2 (a) and (b)), and the second hole collimator and the second slit collimator (as shown in fig. 3 (a) and (b)) used in this embodiment are each composed of a rectangular tungsten alloy plate, in which the tungsten alloy material has a strong absorption effect on gamma photons. The sizes of the first hole collimator 1 and the first slit collimator 2 are both 38.6mm (long) × 38.6mm (wide) × 8mm (thick), the aperture of the first collimating hole 11 and the width of the first collimating slit 21 are both 1.5mm, the sizes of the second hole collimator 3 and the second slit collimator 4 are both 22.3mm (long) × 22.3mm (wide) × 8mm (thick), and the aperture of the second collimating hole 31 and the width of the second collimating slit 41 are both 0.5mm.
In this embodiment, the first gamma photon detector 51 and the second gamma photon detector 52 are both LaBr3 detectors, and the adopted crystal is a whole continuous LaBr3 crystal, and the size of the crystal is 50mm (length) × 50mm (width) × 6mm (thickness). One end of the LaBr3 crystal, which is far away from the slit collimator or the hole collimator, is provided with a coupling Photomultiplier (PMT) or a silicon Photomultiplier (silicon photomultipliers, siPM), which is used for photoelectric signal conversion so as to realize the measurement of the action position, energy and time of gamma photons in the crystal.
The arrangement of the first collimating holes 12 and the second collimating holes 32 in the hole collimator used in the imaging system of the embodiment of the present disclosure is not limited to the arrangement of a certain number, the same size, equal spacing and specific orientation, but may also be the arrangement of a plurality of numbers, unequal spacing and different orientations of collimating holes, and the number, size, arrangement distance and arrangement direction of the collimating holes of different hole collimators can be selected according to the factors of the detection efficiency, the signal-to-noise ratio, the spatial resolution, the distance from the hole collimator to the corresponding surface of the first gamma photon detector 51, the distance from the center of the imaging object to the plane of the hole collimator, and the like to be achieved.
The arrangement of the first collimating slit 22 and the second collimating slit 42 in the slit collimator used in the imaging system of the embodiment of the present disclosure is not limited to the arrangement of a certain number, the same size, equal spacing and specific orientation, but may also be the arrangement of a plurality of numbers, different sizes, unequal spacing and different orientations of collimating slits, and the number, size, arrangement distance and arrangement direction of the collimating slits of different slit collimators may be selected according to the factors of the detection efficiency, the signal-to-noise ratio, the spatial resolution, the distance from the slit collimator to the surface of the corresponding second gamma photon detector 52, the distance from the center of the imaging object to the plane of the slit collimator, and the like to be achieved.
The probes used in the imaging system according to the embodiment of the present disclosure are not limited to only using 4 first probes and 4 second probes (as shown in fig. 1), but may be a combination of one first probe and one second probe (in this case, the probing planes of the two probes are preferably arranged vertically), or may be a combination of at least one first probe and at least one second probe in other numbers (when the first probe and the second probe are arranged vertically, the total number of probes is not more than 6, and when 6 probes are provided in total, the 6 probes are respectively arranged in the upper, lower and four dimensions of the imaging object), and different probe combinations may be selected according to the factors of the desired probing efficiency, signal-to-noise ratio, spatial resolution, and the like.
The radionuclide labeled by the drug used in the imaging system of the disclosed embodiments may be other multi-gamma photon radionuclide besides lutetium 177, i.e., the radionuclide can generate at least two gamma photons in a cascade manner in a short time during the decay process, including but not limited to indium 111, sodium 22, iodine 131, thallium 201, rubidium 82, yttrium 90, etc.
It should be noted that, the probes used in the imaging system according to the embodiment of the present disclosure are arranged in a non-parallel manner, and since the distribution probability of the emission included angle between a plurality of gamma photon events in the multi-gamma photon coincidence events of most radionuclides is the largest at 90 degrees, in most cases, the probes are distributed perpendicularly to each other as the distribution optimal scheme.
The flow of the imaging method of the imaging system provided by the present disclosure is shown in fig. 4, and the specific implementation steps of the method are described as follows with reference to embodiment 1:
(1) Starting the imaging system, setting the acquisition time to be 20 minutes, and setting the time to be 80ns according with the time window width of the module 6; the energy windows of gamma photon energies detected by the first gamma photon detector 51 and the second gamma photon detector 52 are set according to the gamma photon energies emitted by the multi-gamma photon radionuclide used. The gamma photon emitting nuclide used in this embodiment is lutetium 177, which in a cascade fashion during decay produces two gamma photons with energies of 113keV and 208keV, respectively, in a very short time (typically within a few hundred nanoseconds depending on the radionuclide used), thus setting the two energy windows of the first gamma photon detector 51 and the second gamma photon detector 52 to a combination of one 113keV ± 10% energy window and one 208keV ± 10% energy window; the number of energy windows of the first gamma photon detector 51 and the second gamma photon detector 52 can be adjusted according to the number of gamma photons emitted by the radionuclide cascade, namely, one energy window corresponds to each energy gamma photon; the width of each energy window is adjustable according to the energy resolution of the first and second gamma photon detectors 51, 52; a radiopharmaceutical labeled with lutetium 177 at an activity of 4mCi was injected into the imaged subject.
(2) Selecting a hole collimator and a slit collimator which are positioned in the detection range of the corresponding gamma photon detector according to the size of the imaging object, and if the size of the imaging object is larger than a second imaging range 9, moving out a second hole collimator 3 and a second slit collimator 4 for the imaging system shown in fig. 1; if the size of the imaging subject is smaller than the second imaging range 9, the first aperture collimator 1 and the first slit collimator 2 are removed.
(3) The computer platform 7 judges whether the imaging process is finished according to the set acquisition time; if so, executing the step (6); if not, executing step (4).
(4) The time coincidence module 6 judges whether the first gamma photon detector 51 and the second gamma photon detector 52 detect a double gamma photon coincidence event, if so, the step (5) is executed; if not, executing the step (3); the double gamma photon coincidence event, i.e. if two gamma photon events detected by one first gamma photon detector 51 and one second gamma photon detector 52 are within the time window set by the time coincidence module 6, the two detected gamma photon events constitute a double gamma photon coincidence event.
(5) The computer platform 7 judges whether the two gamma photon energies input by the first gamma photon detector 51 and the second gamma photon detector 52 are respectively in the two set energy windows according to the two gamma photon event energy information input by the first gamma photon detector and the second gamma photon detector; if the dual gamma photon is not in the set energy window, the dual gamma photon coincidence event is abandoned; if within the set energy window, calculating an intersection point determined by back projection of two gamma photon events of each multi-gamma photon coincidence event as a decay possible position 10 (i.e. a possible position of decay of the radionuclide), and recording the decay possible position 10; and (5) executing the step (3).
(6) The method comprises the steps of obtaining possible distribution of the radioactive nuclide in an imaging object according to possible decay positions of the radioactive nuclide calculated by all double gamma photon coincidence events, and reconstructing by using image reconstruction algorithms such as maximum likelihood expected expectation maximization (MLEM) algorithm, ordered Subset Expectation Maximization (OSEM) algorithm and the like to obtain a reconstructed image, wherein the distribution is estimated more accurately.
The imaging system in the embodiment of the disclosure can change the imaging range and the imaging performance by moving the collimator, thereby improving the image spatial resolution of the small-size imaging object and improving the image quality.
The imaging method of the present disclosure is programmed (the process can be implemented by a programmer through a conventional programming technique) and then input into the computer platform 7, and the imaging method can achieve the expected effect according to the steps.
In the description of the present application, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present application and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the present application.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In this application, unless expressly stated or limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can include, for example, fixed connections, removable connections, or integral parts; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through intervening media. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
While embodiments of the present application have been shown and described above, it will be understood that the above embodiments are exemplary and should not be construed as limiting the present application and that changes, modifications, substitutions and alterations in the above embodiments may be made by those of ordinary skill in the art within the scope of the present application.
Claims (10)
1. A multi-gamma photon coincidence imaging system is characterized by comprising a time coincidence module, a computer platform and a plurality of probes of different types; the plurality of different types of probes comprise at least one first probe and at least one second probe, the first probe is composed of at least two hole collimators which are parallel to each other and a first gamma photon detector with a time measurement function, the second probe is composed of at least two slit collimators which are parallel to each other and a second gamma photon detector with a time measurement function, each hole collimator and each slit collimator are formed by respectively forming at least one collimation hole and at least one collimation slit on a respective alloy plate, the collimation holes of each hole collimator in the first probe are different in size, the collimation slits of each slit collimator in the second probe are different in size, each hole collimator and each slit collimator are respectively controlled by a corresponding driving part, so that one hole collimator in each first probe and one slit collimator in each second probe are positioned between the front end of the corresponding gamma photon detector and the imaging object and positioned in the detection range of the corresponding gamma photon detector, and the rest hole collimators in each first probe and each second collimator are positioned outside the detection range of the corresponding gamma photon detector, and the rest of the gamma photon detectors in the other detection slits are not capable of generating radioactive decay through the gamma photon detectors of radioactive nuclides of the imaging photon detectors; time signal lines of all the gamma photon detectors are connected with the time coincidence module, a time window set by the time coincidence module is used for judging whether a plurality of gamma photon events detected by a plurality of probes respectively form a multi-gamma photon coincidence event or not, and the judgment result is input into the computer platform; energy and position signal lines of all the gamma photon detectors are also simultaneously connected with the computer platform and are used for judging the effectiveness of the multi-gamma photon coincidence event and calculating the intersection point of a projection line where the occurrence position of the multi-gamma photon coincidence event is possibly located and the projection line in an imaging range, so that the possible position of the radionuclide when decay occurs is obtained; and obtaining the possible distribution of the radioactive nuclide in the imaging object according to the possible positions of all the radioactive nuclides when the radioactive nuclide decays, and performing more accurate estimation on the distribution through an image reconstruction algorithm.
2. The multi-gamma photon coincidence imaging system of claim 1, wherein the first and second gamma photon detectors have neither a width nor a length less than
D is the size of the imaging object, a is the distance from the surface of the hole collimator or the slit collimator to the corresponding surface of the gamma photon detector, and b is the distance from the center of the imaging object to the surface of the hole collimator or the slit collimator.
3. The multi-gamma photon coincidence imaging system of claim 1, wherein the detection planes of the first and second probes are arranged in a non-parallel arrangement therebetween.
4. The multi-gamma photon coincidence imaging system of claim 1, wherein when a plurality of the first probes and a plurality of the second probes are provided, the first probes and the second probes are alternately arranged and the detection planes of the first probes and the detection planes of the second probes are arranged in a non-parallel manner.
5. The multi-gamma photon coincidence imaging system of claim 1, wherein each aperture collimator and each slit collimator employs a flat collimator and/or a curved collimator.
6. The gamma photon coincidence imaging system of claim 5, wherein the curved collimator is a closed or an open curved collimator.
7. The gamma photon coincidence imaging system of claim 1, wherein the drive component is a robotic arm or a drive motor.
8. The gamma photon coincidence imaging system of claim 1 wherein the drive component controls translation of the respective aperture collimator or slit collimator in a height direction of the imaging subject.
9. The gamma photon coincidence imaging system of claim 1, wherein the radionuclide, in its decay process, is capable of generating at least two gamma photons in a cascade fashion in a short time.
10. An imaging method using the imaging system according to any one of claims 1 to 9, comprising:
(1) Starting the multi-gamma photon coincidence imaging system, and setting the time window width of a time coincidence module; setting an energy window of each gamma photon detector according to the gamma photon energy emitted by the used radionuclide;
(2) According to the size of an imaged object, the corresponding hole collimator and the corresponding slit collimator are moved to the detection range of the corresponding gamma photon detector by using the driving part, and the rest hole collimators and the rest slit collimators are moved out of the detection range of the corresponding gamma photon detector;
(3) The computer platform judges whether the imaging process is finished according to the set acquisition time; if so, executing the step (6); if not, executing the step (4);
(4) The time coincidence module judges whether each gamma photon detector detects a multi-gamma photon coincidence event, if so, the step (5) is executed; if not, executing the step (3);
(5) The computer platform judges whether the input gamma photon energy is respectively in the set energy windows according to the gamma photon energy information input by each gamma photon detector; if not, discarding the multi-gamma-photon coincidence event; if the gamma photon coincidence events are in the set energy window, calculating a plurality of projection planes where the occurrence positions of the gamma photon coincidence events are located according to the position information of one gamma photon input by each gamma photon coincidence event in the first gamma photon detector, and calculating a plurality of projection lines where the occurrence positions of the gamma photon coincidence events are located according to the position information and the energy information of one gamma photon input by each gamma photon coincidence event in the second gamma photon detector; recording a plurality of projection planes and a plurality of corresponding intersection points of a plurality of projection lines in the imaging object respectively determined by a plurality of gamma photons in each multi-gamma photon coincidence event as a plurality of possible positions of radionuclide decay; executing the step (3);
(6) The possible distribution of the radionuclide in the imaging object is obtained according to the plurality of possible decay positions of the radionuclide calculated by all the multi-gamma photon coincidence events, and the distribution is estimated more accurately by an image reconstruction algorithm.
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