CN115778418A - Crystal array detector and emission imaging equipment - Google Patents

Abstract

The invention provides a crystal array detector and an emission imaging device. The crystal array detector comprises a crystal array, an array reflecting layer and a light sensor layer. The crystal array includes a composite crystal layer including a plurality of first scintillation crystals of a first type and a plurality of second scintillation crystals of a second type arranged in a close-packed arrangement in a lateral plane, the plurality of first scintillation crystals being dispersed among the plurality of second scintillation crystals, each of the plurality of first scintillation crystals having a first scintillation light decay time, each of the plurality of second scintillation crystals having a second scintillation light decay time that is different from the first scintillation light decay time. Since multiple first scintillation crystals and multiple second scintillation crystals with different scintillation light decay times are used, ICS events in which energy deposition has occurred within both types of scintillation crystals can be screened out of the energy deposition events detected in the photosensor layer. The signal-to-noise ratio of the reconstructed image can be greatly improved by rejecting or correcting the ICS event.

Description

Crystal array detector and emission imaging device

Technical Field

The present invention relates to an emission imaging system, and in particular, to a crystal array detector and an emission imaging apparatus having the same.

Background

Emission Computed Tomography (ECT) is a kind of imaging technology capable of displaying the distribution and three-dimensional distribution image of radioactive nuclide in each layer of organism, and the technology utilizes the tracing principle of radioactive nuclide to detect the radioactive ray emitted by radioactive nuclide decay and form image through data processing. ECT is currently divided into two major categories, one for detecting the distribution of gamma-emitting radionuclides in the body, called Single Photon Emission Computed Tomography (SPECT); another type of radiation used to detect annihilation radiation of a radionuclide capable of emitting positrons is known as Positron Emission Tomography (PET). Among them, PET imaging has been widely used in the related field of medical imaging.

PET imaging detects two gamma photons emitted in opposite directions upon positron annihilation and reconstructs, by computer, the three-dimensional distribution of the positron tracer in the body. However, during detection, an Inter Crystal scattering event (ICS) is likely to occur when a gamma photon strikes a scintillation Crystal, and the presence of the ICS event can seriously degrade the signal-to-noise ratio of the reconstruction algorithm.

Typically, in biomedical research, most of preclinical disease models use mice as animal models to simulate human health and disease states, and preclinical PET imaging techniques dedicated to small animal imaging are important tools for the transition from molecular biology to the clinic. Because small animals are much smaller in volume and mass than humans, PET imaging for small animals requires higher system sensitivity and spatial resolution in order to acquire image details equivalent to those available for human PET imaging.

The high resolution of PET imaging of small animals is realized based on the smaller size of the scintillation Crystal, and for the smaller size of the scintillation Crystal, an Inter Crystal Scattering (ICS) event can introduce larger noise into a reconstructed image, reduce the signal-to-noise ratio of the reconstructed image, and influence a researcher to make judgment based on the image. Therefore, a certain number of ICS events are identified in PET imaging, and the ICS events are removed or corrected from the total number of the events, so that the signal-to-noise ratio of a reconstructed image can be effectively improved, and the imaging result is more accurate.

In order to screen an ICS event from a total event, an unconventional detector structure design is often adopted in the prior art, and the type of the event is determined based on an acquired photoelectric signal, so that the ICS event is removed or corrected from the total event. The prior art discloses a detector structure for reducing ICS events, the detector being an array of scintillation crystal strips with the side of the detector array facing the center of the field of view. With this arrangement, the detector has the capability to read out a single ICS event. However, in such a detector structure, each wafer of the crystal array needs to be read out individually, and a photodetector and a readout circuit need to be inserted between each wafer of the crystal array, so that the overall detector is very expensive. Moreover, the inserted sets of photodetectors and readout circuits result in a significant reduction in the effective detection volume of the detector, resulting in very low overall detector sensitivity.

Disclosure of Invention

According to an aspect of the present invention, there is provided a crystal array detector comprising:

a crystal array including a composite crystal layer including a plurality of first scintillation crystals of a first type and a plurality of second scintillation crystals of a second type arranged in close proximity in a lateral plane, the plurality of first scintillation crystals being dispersed among the plurality of second scintillation crystals, each of the plurality of first scintillation crystals having a first scintillation light decay time, each of the plurality of second scintillation crystals having a second scintillation light decay time different from the first scintillation light decay time, a side of each of the plurality of first scintillation crystals and the plurality of second scintillation crystals being covered with an intralayer layer that reflects light toward an interior of the corresponding scintillation crystal, the crystal array having opposing entrance and exit faces in a longitudinal direction perpendicular to the lateral light reflection plane;

the array reflecting layer covers the incident surface and reflects light towards the interior of the crystal array; and

a light sensor layer optically coupled to the exit face.

In the crystal array detector provided by the invention, because the plurality of second scintillation crystals of different types are dispersed in the plurality of first scintillation crystals, by enabling the first scintillation crystals and the second scintillation crystals to have different scintillation light decay times, the ICS event that energy deposition occurs in both types of scintillation crystals can be screened out from the energy deposition events detected in the photosensor layer. Thus, by effectively detecting and rejecting or rectifying these ICS events, the proportion of remaining scatter events to the total number of events is greatly reduced, which can greatly improve the signal-to-noise ratio of the reconstructed image. The smaller the cross section of the scintillation crystal in the crystal array is, the larger the fraction of the identified ICS events in the total events is, and the identification capability of the crystal array detector provided by the invention on the ICS events is higher in data accuracy compared with the crystal array adopting the small-size scintillation crystal. In addition, the crystal array detector can adopt the structural design of a conventional detector, and the manufacturing cost of the whole device is in a common level, so that the crystal array detector is more practical.

Illustratively, at least a portion of the plurality of first scintillation crystals and the plurality of second scintillation crystals alternate along a first lateral direction within the lateral plane. With the crystal array detector arranged in this way, the capability of identifying ICS events is stronger, and the sensitivity and the spatial resolution of the whole device are higher.

Illustratively, the plurality of first scintillation crystals and the plurality of second scintillation crystals completely alternate along the first lateral direction.

Illustratively, at least a portion of the plurality of first scintillation crystals and the plurality of second scintillation crystals are alternately arranged along a second lateral direction within the lateral plane, wherein the second lateral direction has an angle with the first lateral direction. With the crystal array detector thus arranged, the sensitivity and resolution for identifying ICS events is better.

Illustratively, the included angle is 90 degrees. Such crystal array detectors have been able to identify a larger fraction of ICS events during detection. Therefore, when the crystal array detector provided by the embodiment is used for imaging, the signal to noise ratio of a reconstructed image can be greatly improved, and the sensitivity and the spatial resolution of an imaging system are further improved.

Illustratively, the plurality of first scintillation crystals and the plurality of second scintillation crystals are arranged completely alternately along both the first lateral direction and the second lateral direction.

Illustratively, the crystal array includes a plurality of composite crystal layers, wherein first scintillating crystals in adjacent composite crystal layers are staggered; and/or the second scintillator crystals in adjacent composite crystal layers are staggered. The crystal array detector with the arrangement can reduce the influence of the action depth of gamma photons in the scintillation crystal on the spatial resolution, and improve the spatial resolution of the crystal array detector. The scintillation crystals may be staggered not only within the composite Crystal layers but also between the composite Crystal layers, so that the Crystal array detector is more capable of recognizing ICS events, and in particular so that the Crystal array detector is also capable of recognizing inter-Layer inter-Crystal scattering events (CLCS), which is one of the ICS events. Thus improving the sensitivity and spatial resolution of the overall device.

Illustratively, a plurality of third scintillation crystals of a third type are also included in the composite crystal layer, the plurality of third scintillation crystals being dispersed among the plurality of first scintillation crystals and the plurality of second scintillation crystals and being in intimate contact with adjacent scintillation crystals, each of the plurality of third scintillation crystals having a third scintillation light decay time that is different from the first scintillation light decay time and the second scintillation light decay time. This allows a larger number of ICS events to be identified, and therefore a crystal array detector with such a crystal array will also be more capable of identifying ICS events.

Illustratively, in the composite crystal layer, the apex angles of each type of scintillation crystal abut a different type of scintillation crystal. The ICS event identified by the crystal array detector designed in the way is more complete and comprehensive, the omission of the ICS event in the detection is reduced, and the omission in the process of removing or correcting the ICS event is further reduced, so that the signal-to-noise ratio of a reconstruction algorithm is improved, and the whole device has better sensitivity and spatial resolution.

Illustratively, in the composite crystal layer, the sides of each type of scintillation crystal abut a different type of scintillation crystal. Therefore, the capability of the whole device for identifying the ICS event is stronger, and the sensitivity and the spatial resolution are improved.

Illustratively, in any one of the crystal array detectors as described above, the crystal arrays are plural and arranged in sequence along the longitudinal direction, each crystal array has a corresponding array light-reflecting layer and a light sensor layer, and the light sensor layer corresponding to one of the two adjacent crystal arrays and the array light-reflecting layer corresponding to the other of the two adjacent crystal arrays are arranged opposite to each other. The crystal array detector with the arrangement can reduce the influence of the action depth of gamma photons in the scintillation crystal on the spatial resolution, and improve the spatial resolution of the crystal array detector.

According to another aspect of the present invention, there is provided an emission imaging apparatus. The emission imaging device includes a plurality of detectors and a processor. The plurality of detectors surround to form a detection cavity, the detection cavity is used for accommodating an object to be detected, at least one of the plurality of detectors is any one of the crystal array detectors, and the incident surface of the crystal array detector faces the detection cavity. The processor is used for determining a mixed energy deposition event according to a photoelectric signal acquired by the photosensor, wherein the photoelectric signal is generated based on the first scintillation light decay time and the second scintillation light decay time, and the mixed energy deposition event is an event that energy deposition occurs in different types of scintillation crystals.

A series of concepts in a simplified form are introduced in the summary, which is described in further detail in the detailed description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

The advantages and features of the present invention are described in detail below with reference to the accompanying drawings.

Drawings

The following drawings of the present invention are included to provide a further understanding of the invention. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings, there is shown in the drawings,

FIG. 1 is a cross-sectional view of a crystal array probe according to a first exemplary embodiment of the present invention;

FIG. 2 is a top view of a crystal array of the crystal array detector shown in FIG. 1;

FIG. 3 is a top view of a crystal array detector according to a second exemplary embodiment of the present invention;

FIG. 4 is a top view of a crystal array detector according to a third exemplary embodiment of the present invention;

FIG. 5 is a top view of a crystal array detector according to a fourth exemplary embodiment of the present invention;

FIG. 6 is a cross-sectional view of a crystal array detector according to a fifth exemplary embodiment of the present invention;

FIG. 7 is a cross-sectional view of a crystal array detector according to a sixth exemplary embodiment of the present invention;

FIG. 8 is a top view of a crystal array detector according to a seventh exemplary embodiment of the invention;

FIG. 9 is a top view of a crystal array detector according to an eighth exemplary embodiment of the invention;

FIG. 10 is a cross-sectional view of a crystal array probe according to a ninth exemplary embodiment of the invention; and

fig. 11 is a QDC-TOT diagram of a data processing method of the transmit imaging apparatus.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the present invention.

In the following description, a detailed structure will be presented for a thorough understanding of the present invention. It is apparent that embodiments of the invention are not limited to the specific details known to those skilled in the art. The following detailed description of the preferred embodiments of the invention, however, the invention can be practiced otherwise than as specifically described.

The present invention provides a crystal array probe 10, as shown in FIG. 1. The crystal array probe 10 may include a crystal array 100, an array reflective layer 200, and a light sensor layer 300.

The crystal array 100 can include a composite crystal layer that can include a plurality of first scintillation crystals 101 of a first type and a plurality of second scintillation crystals 102 of a second type arranged in close proximity in a lateral plane. Scintillation crystals refer to crystals that convert the energy of energetic particles into light energy upon impact by gamma photons. The first scintillation crystal 101 may be a lutetium yttrium silicate scintillation crystal (LYSO crystal), a bismuth germanate scintillation crystal (BGO crystal), a lutetium cerium-doped lutetium oxyorthosilicate scintillation crystal (LSO crystal), a gadolinium oxyorthosilicate scintillation crystal (GSO crystal), a sodium iodide scintillation crystal (NaI crystal), or a crystal of any other variety of materials. The second scintillation crystal 102 can be a crystal of LYSO, BGO, LSO, GSO, naI, or a variety of other materials. Each of the plurality of first scintillation crystals 101 can have a first scintillation light decay time and each of the plurality of second scintillation crystals 102 can have a second scintillation light decay time that is different than the first scintillation light decay time. The decay times of the scintillation light of the first scintillation crystal 101 and the second scintillation crystal 102 can be made different by selecting different materials. The decay time of the scintillation light is the time required for the number of emitted scintillation photons after excitation of the scintillation crystal to fall from a maximum to 1/e of the initial value. The decay time of scintillation light is well known to those skilled in the art and will not be described in further detail herein. The decay time of the scintillation light of LYSO crystal is 40ns, the decay time of the scintillation light of LSO crystal is 40ns, the decay time of the scintillation light of GSO crystal is 50ns, the decay time of the scintillation light of BGO crystal is 300ns, and the decay time of the scintillation light of NaI crystal is 250ns.

Illustratively, the difference between the scintillation light decay times for different types of scintillation crystals can be greater than or equal to 10ns. Preferably, the difference between the decay times of the scintillation light for different types of scintillation crystals may be greater than or equal to 40ns. More preferably, the difference between the decay times of the scintillating light of the different types of scintillation crystals can be greater than or equal to 100ns. The larger the difference between the decay times of the scintillation light for different types of scintillation crystals, the stronger the ability to identify an ICS event as will be mentioned below.

For example, the first scintillation crystal 101 can be a scintillation crystal with a crystal material of LYSO, while the second scintillation crystal 102 can be a scintillation crystal with a crystal material of BGO. Preferably, the larger the difference between the first scintillation light decay time and the second scintillation light decay time, the better. The first scintillation crystal 101 and the second scintillation crystal 102 can be prismatic, cylindrical, or other various shapes. The first scintillator crystal 101 and the second scintillator crystal 102 may have the same size and shape, or may have different sizes and shapes, respectively. In the embodiment shown in fig. 1-2, the first scintillation crystal 101 and the second scintillation crystal 102 are each a quadrangular prism. In the embodiment illustrated in fig. 4-5, the first scintillation crystal 101 and the second scintillation crystal 102 are each triangular prisms. In the embodiment shown in fig. 9, the first scintillation crystal 101 and the second scintillation crystal 102 are each a hexagonal prism. In other embodiments, not shown, one of the first scintillation crystal 101 and the second scintillation crystal 102 can be a triangular prism and the other a quadrangular prism, so that two triangular prisms are sandwiched between each two quadrangular prisms and can be spliced into a quadrangular prism, thereby enabling the first scintillation crystal 101 and the second scintillation crystal 102 to be arranged in close proximity.

Referring back to fig. 2, the plurality of first scintillation crystals 101 and the plurality of second scintillation crystals 102 are arranged in close proximity in a lateral plane (e.g., an XY plane). The transverse plane is perpendicular to the stacking direction of the crystal array 100, the array light-reflecting layer 200 and the photosensor layer 300, which is the longitudinal direction Z-Z shown in fig. 1. The plurality of first scintillator crystals 101 may be dispersed among the plurality of second scintillator crystals 102, and as shown in fig. 1, the second scintillator crystals 102 may be disposed between adjacent first scintillator crystals 101, and the first scintillator crystals 101 may be disposed between adjacent second scintillator crystals 102. However, it is not intended that the second scintillator crystals 102 are provided between any adjacent first scintillator crystals 101, and the first scintillator crystals 101 may be provided between any adjacent second scintillator crystals 102. As shown in fig. 2, no other types of scintillator crystals are disposed between adjacent first scintillator crystals 101 and between adjacent second scintillator crystals 102 as viewed in the Y direction. Also, although the first scintillator crystals 101 and the second scintillator crystals 102 are alternately arranged along the X direction in the drawing, in other embodiments not shown, a plurality of second scintillator crystals 102 may be disposed between adjacent first scintillator crystals 101, and a plurality of first scintillator crystals 101 may be disposed between adjacent second scintillator crystals 102. That is, the first scintillator crystal 101 and the second scintillator crystal 102 may be arranged randomly or irregularly.

As shown in fig. 1, the sides of each of the plurality of first scintillation crystals 101 and the plurality of second scintillation crystals 102 can be covered with an intra-layer light reflecting layer (not shown) that reflects light toward the interior of the corresponding scintillation crystal. The crystal array may have opposing entrance (upper surface in fig. 1) and exit (lower surface in fig. 1) faces along a longitudinal direction Z-Z perpendicular to the transverse plane. The reflective layer in the layer can prevent scintillation crystals from being affected by scintillation light generated when the scintillation crystals are impacted by gamma photons. When the scintillation light of a single scintillation crystal is detected, the reflective layer in the layer can improve the detection accuracy.

The array reflective layer 200 may overlie the incident surface and reflect light toward the interior of the crystal array. The array light reflecting layer 200 can prevent scintillation light generated by the scintillation crystal when being impacted by gamma photons from being emitted from the incidence surface of the scintillation crystal. The in-layer retroreflective layer and the array retroreflective layer 200 described above can be formed by spraying, coating (e.g., spraying or silver coating), or attaching a retroreflective material (e.g., ESR sheeting). As a high-efficiency Reflector, ESR (Enhanced Specular Reflector) has a reflectance of 98% or more in the entire visible light spectrum range, which is higher than that of other types of reflectors. ESR is composed of a polymer film layer and is a more green and environment-friendly reflecting sheet material. ESR retroreflective sheeting has a thickness of around 40 microns, for example 38 microns.

The light sensor layer 300 may be optically coupled to the exit face. The light sensor layer 300 may include one or more light sensors, which may be of various types, now existing or that may appear in the future, such as photomultiplier tubes (PMTs), silicon photomultiplier tubes (sipms), and the like. Optically coupling means that a scintillation light signal can pass between the photosensor layer and the scintillation crystal through the exit face. The array reflective layer 200 can cooperate with the reflective layer in the layer to make the scintillation light generated by the scintillation crystal being hit by gamma photons only exit from the exit layer, and further make the scintillation light only pass through the exit layer and transmit to the photosensor layer 300. The optical sensor layer 300 may receive the scintillation light signal transmitted through the exit surface, and may further convert the scintillation light signal into an electrical signal, where the electrical signal may be used for data processing by a back-end processor, and a visual image may be obtained through the data processing.

For a plurality of first scintillation crystals 101 dispersed in a plurality of second scintillation crystals 102, when these first scintillation crystals 101 are impacted by a gamma photon, if this impact scatters, the particles and secondary particles produced by the scattering can deposit energy in the adjacent second scintillation crystals 102 to be detected by the photosensor layer 300, and thus it can be assumed that an ICS event has occurred. When the first scintillation crystal 101 and the second scintillation crystal 102 are impacted by gamma photons, ICS events can be determined according to the photoelectric signals collected by the photosensor layer 300 due to different scintillation light decay times.

Illustratively, the ICS event may be determined based on a QDC-TOT photo-electric information map. The energy deposition times that occur in different types of scintillation crystals on the QDC-TOT electro-optical information map will be located in different regions on the electro-optical information map, as shown in FIG. 11. QDC (Coulomb digital conversion), also known by the portugal manufacturer as charge integration, means charge-to-digital conversion, which is a charge integration sum. TOT (time over threshold) is the over-threshold time in picoseconds (ps). Different materials have different decay times of the scintillation light. For example, the decay times of scintillation light for LYSO crystals and BGO crystals are 42ns and 300ns, respectively. When the first scintillation crystal 101 and the second scintillation crystal 102 are selected from the LYSO crystal and the BGO crystal, respectively, the event detected by the photosensor layer 300 can be preliminarily identified as a LYSO event, a BGO event, or an ICS event, using the large difference in decay time of scintillation light for the two types of scintillation crystals. On the QDC-TOT optoelectronic information graph, LYSO events are concentrated in a first area I, BGO events are concentrated in a second area II, and ICS events are concentrated in a third area III. Thus, ICS events can be determined based on the QDC-TOT photo-electric information map. The determined ICS events can be deleted or rectified as needed to provide more accurate position information to the reconstruction algorithm.

It should be noted that determining the ICS event based on the QDC-TOT optoelectronic information diagram is only an example of the method for identifying the ICS event by the crystal array detector 10 provided by the present invention, and those skilled in the art can also determine the ICS event based on the optoelectronic signals collected by the photosensor layer 300 by using various methods that may occur in the present or future. Therefore, determining the ICS event is not limited to being implemented by the QDC-TOT optoelectronic information map. For example, a Delayed pulse charge integration (DCI) method may be used to determine the ICS event based on the photo signal collected by the photo sensor layer 300.

As can be seen, in the crystal array detector 10 provided by the present invention, since the plurality of second scintillation crystals 102 of different types are dispersed in the plurality of first scintillation crystals 101, by making the first scintillation crystals 101 and the second scintillation crystals 102 have different scintillation light decay times, an ICS event in which energy deposition has occurred in both types of scintillation crystals can be screened out of the energy deposition events detected in the photosensor layer 300. Thus, by efficiently detecting these ICS events, the proportion of the remaining scatter events to the total number of events is greatly reduced, which greatly improves the signal-to-noise ratio of the reconstructed image. The smaller the cross section of the scintillation crystal in the crystal array, the greater the fraction of the identified ICS events in the total events, and the greater the data accuracy improvement for the crystal array detector 10 provided by the invention for the identification capability of the ICS events for the crystal array using the small-sized scintillation crystal. In addition, the crystal array detector 10 can be designed by adopting a conventional detector structure, and the manufacturing cost of the whole device is a common level, so that the crystal array detector is more practical.

It should be noted that the crystal array 100 and the light sensor layer 300 can be directly coupled by optical glue, or a light guide layer can be disposed between the two. The lightguide layer may be constructed of a lightguide material including, but not limited to, a resin lightguide, a light transmissive glass, a liquid lightguide, or other various materials.

1-2, at least a portion of the plurality of first scintillation crystals 101 and the plurality of second scintillation crystals 102 can be alternately arranged along a first lateral direction X-X in a lateral plane. This arrangement allows the crystal array detector 10 to have a higher sensitivity for detecting ICS events in the first lateral direction X-X, and thus a better ability to identify ICS events. With the crystal array detector 10 thus arranged, as shown in fig. 2, in an exemplary embodiment in which the plurality of first scintillation crystals 101 and the plurality of second scintillation crystals 102 are all arranged alternately in the first lateral direction X-X, the ability to identify ICS events is greater, and the sensitivity and spatial resolution of the overall apparatus is greater.

Illustratively, as shown in fig. 3, at least a portion of the plurality of first scintillation crystals 101 and the plurality of second scintillation crystals 102 can be alternately arranged along a second lateral direction Y-Y within the lateral plane, wherein the second direction has an angle with the first direction. This arrangement allows the crystal-array detector 10 to also have a better ability to identify ICS events in the second lateral direction Y-Y. Illustrated in fig. 3 is one exemplary embodiment in which the plurality of first scintillation crystals 101 and the plurality of second scintillation crystals 102 are all alternately arranged in the second lateral direction Y-Y. With the crystal array detector 10 thus arranged, the sensitivity and resolution for recognizing ICS events is better.

Preferably, the plurality of first scintillation crystals 101 and the plurality of second scintillation crystals 102 are all alternately arranged along the first lateral direction X-X and the second lateral direction Y-Y. With the crystal array detector 10 thus arranged, the sensitivity and resolution for identifying ICS events is optimal.

Illustratively, the first lateral direction X-X may be at an angle of 90 degrees to the second lateral direction Y-Y. FIG. 3 shows an exemplary embodiment in which the first lateral direction X-X is at a 90 degree angle to the second lateral direction Y-Y, and the plurality of first scintillation crystals 101 and the plurality of second scintillation crystals 102 are all alternately arranged in the first lateral direction X-X and the second lateral direction Y-Y. At this time, the first scintillator crystals 101 and the second scintillator crystals 102 are staggered, each first scintillator crystal 101 is surrounded by the second scintillator crystal 102, and likewise, each second scintillator crystal 102 is surrounded by the first scintillator crystal 101. Thus, taking the example of gamma photons impinging on the first scintillation crystal 101, there is a high probability that the secondary particles generated by scattering will enter the second scintillation crystal 102 adjacent to the first scintillation crystal 101 (as shown by arrow a in fig. 3), and further energy will be deposited in both the first scintillation crystal 101 and the adjacent second scintillation crystal 102, and the decay times of the scintillating lights are different based on the first ICS crystal 101 and the second scintillation crystal 102, so that such events can be determined based on the photoelectric signals collected by the photosensor layer 300. That is, such ICS events can be identified. Of course, the secondary particles generated by scattering may enter another first scintillation crystal 101 diagonally adjacent to the first scintillation crystal 101, as indicated by arrow B in fig. 3, and energy is deposited in both diagonally adjacent first scintillation crystals 101, and this type of ICS event occurs between scintillation crystals of the same type, and therefore cannot be identified by the QDC-TOT photoelectron diagram. But such ICS events occur much less frequently than the ICS events indicated by arrow a, and therefore desirably are expected to be adjacent to different types of scintillation crystals, either in a direction perpendicular to the sides of the scintillation crystals or in a diagonal direction, around each scintillation crystal, and an exemplary embodiment will be provided hereinafter for this idea. It is understood, however, that for each scintillation crystal, the fewer its surrounding adjacent scintillation crystals of the same type, the greater the ability to identify an ICS event. The crystal array detector 10 with the crystal array 100 shown in fig. 3 has been able to identify a larger fraction of ICS events during the detection process. Therefore, when the crystal array detector 10 provided by the embodiment is used for imaging, the signal-to-noise ratio of a reconstructed image can be greatly improved, and the sensitivity and the spatial resolution of an imaging system are further improved.

Fig. 4 shows a further embodiment according to the present application. In this embodiment, the cross sections of the first scintillation crystal 101 and the second scintillation crystal 102 are both isosceles right triangles. And one side of each isosceles right triangle is adjacent to different types of scintillation crystals, and the positions of only the vertex angles are adjacent to the scintillation crystals of the same type. In this case the first transverse direction X-X is at an angle other than 90 degrees to the second transverse direction Y-Y. In this embodiment the first transverse direction X-X is at an angle of 45 degrees to the second transverse direction Y-Y. Of course, the first scintillation crystals 101 and the second scintillation crystals 102 are also alternately arranged in a direction within the paper and perpendicular to the first lateral direction X-X. That is, in this embodiment, the first scintillator crystals 101 and the second scintillator crystals 102 can be alternately arranged in more directions. In the crystal array detector 10 employing this crystal array 100, a larger fraction of ICS events can also be identified. Fig. 5 shows another embodiment in which the cross sections of the first scintillation crystal 101 and the second scintillation crystal 102 are both isosceles right triangles. In this embodiment, it can be considered that the first scintillator crystals 101 and the second scintillator crystals 102 are alternately arranged along the first lateral direction X-X and the second lateral direction Y-Y that are perpendicular to each other.

It should be noted that fig. 4 only shows an embodiment in which the angle between the first lateral direction X-X and the second lateral direction Y-Y is not 90 degrees, and the angle between the first lateral direction X-X and the second lateral direction Y-Y can have other values by changing the shapes of the first scintillator crystal 101 and the second scintillator crystal 102 or allowing a gap to occur between the first scintillator crystal 101 and the second scintillator crystal 102.

Illustratively, the crystal array 100 may include a plurality of composite crystal layers. As shown in fig. 6, the crystal array 100 includes two composite crystal layers each including first scintillation crystals 101 and second scintillation crystals 102 alternately arranged. The arrangement of the first scintillator crystal 101 and the second scintillator crystal 102 in the two composite crystal layers is the same. Of course, in other embodiments not shown, the arrangement of the scintillation crystals in the two composite crystal layers may also be different. In the embodiment shown in FIG. 6, the first scintillation crystals 101 in adjacent composite crystal layers are staggered, and the second scintillation crystals 102 in adjacent composite crystal layers are also staggered. With the crystal array detector 10 arranged in this way, the influence of the depth of action of the gamma photons in the scintillation crystal on the spatial resolution can be reduced, and the spatial resolution of the crystal array detector 10 is improved. The scintillation crystals may be staggered not only within the composite crystal layers, but also between the composite crystal layers, such that the crystal array detector 10 is more capable of identifying ICS events, and in particular such that the crystal array detector 10 is also capable of identifying inter-layer inter-crystal scattering events, a CLCS event being one of the ICS events. Thus improving the sensitivity and spatial resolution of the overall device. However, in other embodiments not shown, only one type of scintillator crystal in adjacent composite crystal layers may be staggered. In this case, scintillator crystals of other types (e.g., second type and third type) may not be completely staggered between adjacent composite crystal layers.

As shown in fig. 7, illustratively, a single crystal layer may be included in the crystal array 100 in addition to the above-mentioned composite crystal layer having two types of scintillator crystals. Specifically, the upper layer in the crystal array 100 is a composite crystal layer, the lower layer is a single crystal layer, and the single crystal layer may include only one type of scintillator crystal 104. The scintillation crystal 104 can be an array of crystals or a continuous crystal, which refers to an entire block of scintillation crystals. The scintillation crystal 104 can be the same type as the first scintillation crystal 101, or the same type as the second scintillation crystal 102, or both the first scintillation crystal 101 and the second scintillation crystal 102. In such a crystal array, a part of ICS events occurring in an upper layer can be identified, but ICS events in a lower layer may not be identified, but in any case, the signal-to-noise ratio of a reconstructed image can still be improved. It should be noted that in other embodiments not shown, the crystal array detector provided by the present invention may include two or more crystal arrays, and at least one of the crystal arrays is a composite crystal layer, which is covered by the protection scope of the present application. Further, the position of the composite crystal layer in the entire detector may not be limited, and may be, for example, the lowermost layer near the photosensor layer 300, and/or the uppermost layer far from the photosensor layer 300, and/or an intermediate layer therebetween.

Illustratively, as shown in fig. 8, a plurality of third scintillator crystals 103 of a third type may also be included in the composite crystal layer, and the plurality of third scintillator crystals 103 may be dispersed among the plurality of first scintillator crystals 101 and the plurality of second scintillator crystals 102 and may be in close contact with adjacent scintillator crystals. The third scintillation crystal 103 can have a third scintillation light decay time that is different from the first scintillation light decay time and the second scintillation light decay time. The larger the difference between the first, second, and third scintillation light decay times, the better. The third scintillation crystal 103 can be made of a different scintillation crystal material than the first scintillation crystal 101 and the second scintillation crystal 102. The event that the photosensor layer 300 deposits energy in two different types of scintillation crystals in the event of a gamma photon being directed to the crystal array detector may have three cases, which correspond to an ICS event occurring between the first scintillation crystal 101 and the second scintillation crystal 102, an ICS event between the first scintillation crystal 101 and the third scintillation crystal 103, and an ICS event between the second scintillation crystal 102 and the third scintillation crystal 103, respectively. Of course, it is also possible for an ICS event to occur between the first scintillation crystal 101, the second scintillation crystal 102, and the third scintillation crystal 103. The number of the peripheral, especially diagonally adjacent, scintillation crystals of the same type is smaller for each scintillation crystal, and each scintillation crystal has only two diagonally adjacent scintillation crystals of the same type in the arrangement shown in the figure. Therefore, a larger number of ICS events can be identified, and therefore the crystal array detector 10 having such a crystal array 100 will also be more capable of identifying ICS events. It should be noted that, the above-mentioned drawings illustrate embodiments referred to in this application, but this does not mean that the application can only be implemented in such a form, and in other embodiments not shown, the application can also have various other similar forms, which are not described herein again.

Fig. 9 shows an arrangement of crystal arrays according to another embodiment of the present application. In this crystal array 100, different types of first, second, and third scintillation crystals 101, 102, and 103 are included, and the cross sections of the first, second, and third scintillation crystals 101, 102, and 103 are all in the shape of a regular hexagon. Also, each regular hexagon's sides and corners can abut different types of scintillation crystals. With the crystal array detector 10 having this arrangement, each scintillation crystal is surrounded by a different type of scintillation crystal. For convenience of description, taking the case that a gamma photon strikes the first scintillation crystal 101 for the first time in the event of a gamma photon being emitted to the crystal array detector, secondary particles generated by the gamma photon may enter one or more surrounding scintillation crystals, and these ICS events can be identified because the scintillation decay time of the surrounding scintillation crystal or crystals is different from the scintillation decay time of the first scintillation crystal 101. The ICS event identified by the crystal array detector 10 designed in this way is more complete and comprehensive, the omission of the ICS event in the detection process is reduced, and the omission in the identification of the ICS event is further reduced, so that the signal-to-noise ratio of a reconstruction algorithm is improved, and the whole device has better sensitivity and spatial resolution.

It should be noted that the scintillation crystal can have various other possible shapes besides the triangular, quadrangular and hexagonal shapes, which is applicable to the case where the composite crystal layer includes two types of scintillation crystals, and also to the case where more types of scintillation crystals are available. In addition, different types of scintillation crystals can have the same shape, and can also have different situations.

FIG. 10 shows yet another embodiment according to the present application. As shown in fig. 10, the crystal arrays 100 are plural and arranged in sequence along the longitudinal direction, and each crystal array has a corresponding array light reflecting layer 200 and a light sensor layer 300. The number of crystal arrays 100 shown in fig. 10 is two, and in other embodiments not shown, there may be more crystal arrays 100. The light sensor layer 300 corresponding to one of the two adjacent crystal arrays 100 and the array light reflecting layer 200 corresponding to the other of the two adjacent crystal arrays 100 are disposed opposite to each other. That is, the light sensor layer 300 coupled to the upper crystal array 100 and the array light reflecting layer 200 covering the lower crystal array 100 are opposite to each other. In the illustrated embodiment, the photosensor layer 300 coupled to the upper crystal array 100 and the array reflective layer 200 overlying the lower crystal array 100 are attached to each other, but in other embodiments not shown, they may be spaced apart. In this case, the signal readout circuit of the upper layer photosensor may be placed at the interval. The crystal array detector 10 may include one or more of these repeating units if the array reflective layer 200, the crystal array 100, and the photosensor layer 300 are considered to be one repeating unit. With the crystal array detector 10 arranged in this way, the influence of the action depth of the gamma photons in the scintillation crystal on the spatial resolution can be reduced, and the spatial resolution of the crystal array detector 10 is improved. It should be noted that the crystal array 100 mentioned in fig. 10 may be any one of those mentioned above.

Illustratively, the scintillation crystals in two adjacent crystal arrays may have the same arrangement. Two adjacent crystal arrays are respectively connected to two photosensor layers 300, and the two photosensor layers 300 respectively and independently detect whether energy deposition occurs in the two crystal arrays, so that it can be considered that both photosensor layers 300 recognize an ICS event from a large number of energy deposition events. Of course, the scintillation crystals in two adjacent crystal arrays may also have different arrangements. In the embodiment where two crystal arrays connect one photosensor layer 300 as shown in fig. 6, the plurality of first scintillation crystals in one of the two adjacent crystal arrays are staggered from the plurality of first scintillation crystals in the other of the two adjacent crystal arrays. However, in the embodiment shown in fig. 10 in which each of the crystal arrays connects the photosensor layers, the plurality of first scintillation crystals 101 in one of the two adjacent crystal arrays are staggered from the plurality of first scintillation crystals 101 in the other of the two adjacent crystal arrays, and may also be aligned. Similarly, the second scintillation crystals 102 in the two crystal arrays can be staggered or aligned.

Further, the invention also provides an emission imaging device. The emission imaging device can comprise a plurality of detectors, the detectors can surround to form a detection cavity, and the detection cavity can be used for accommodating an object to be detected. At least a portion of these detectors may be any of the crystal array detectors 10 described above. The entrance face of the crystal array 100 of the crystal array probe 10 may face the detection cavity. Therefore, the data of a plurality of detectors are combined, and more comprehensive and complete three-dimensional information of the object to be detected can be obtained. In the case where some of these detectors employ a crystal array detector 10, the other detectors may be conventional detectors commonly used in PET imaging. The general detector and crystal array detector 10 may be arranged in any suitable manner.

Illustratively, the detection chamber may be cylindrical. The crystal array probe 10 is arranged in a ring around the periphery of the detection chamber. The object to be detected can lie down into the detection cavity. The cylindrical detection cavity is simpler in structure and easy to realize. In other embodiments not shown, the detection chamber may also have other shapes, such as an oblate cylindrical shape, a cuboid shape.

Illustratively, the emission imaging device may further comprise a processor which may be configured to determine a mixed energy deposition event from the photo-electric signals collected by the photosensor layer 300, the mixed energy deposition event being an event in which energy deposition occurs within different types of scintillation crystals. As can be seen from the above description, a hybrid energy deposition event is an ICS event that can be identified. The method for determining the ICS event has been described above and will not be described herein.

The present invention has been illustrated by the above embodiments, but it should be understood that the above embodiments are for illustrative and descriptive purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that many variations and modifications may be made in accordance with the teachings of the present invention, which variations and modifications are within the scope of the present invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (12)

1. A crystal array probe, comprising:

a crystal array comprising a composite crystal layer including a plurality of first scintillation crystals of a first type and a plurality of second scintillation crystals of a second type arranged in a close-packed manner in a lateral plane, the plurality of first scintillation crystals being dispersed among the plurality of second scintillation crystals, each of the plurality of first scintillation crystals having a first scintillation light decay time, each of the plurality of second scintillation crystals having a second scintillation light decay time different from the first scintillation light decay time, a side of each of the plurality of first scintillation crystals and the plurality of second scintillation crystals being covered with an intralayer reflective layer that reflects light toward an interior of the corresponding scintillation crystal, the crystal array having opposing entrance and exit faces in a longitudinal direction perpendicular to the lateral plane;

the array reflecting layer covers the incident surface and reflects light towards the inside of the crystal array; and

a light sensor layer optically coupled to the exit face.

2. The crystal array detector of claim 1, wherein at least a portion of the plurality of first scintillation crystals and the plurality of second scintillation crystals alternate along a first lateral direction within the lateral plane.

3. The crystal array detector of claim 2, wherein along the first lateral direction, the plurality of first scintillation crystals and the plurality of second scintillation crystals completely alternate.

4. The crystal array detector of claim 2, wherein at least a portion of the plurality of first scintillation crystals and the plurality of second scintillation crystals alternate along a second lateral direction within the lateral plane, wherein the second lateral direction has an angle with the first lateral direction.

5. The crystal array detector of claim 4, wherein the included angle is 90 degrees.

6. The crystal array detector of claim 4, wherein the plurality of first scintillation crystals and the plurality of second scintillation crystals are completely interleaved along both the first lateral direction and the second lateral direction.

7. The crystal array detector of claim 1, wherein the crystal array comprises a plurality of the composite crystal layers, wherein first scintillating crystals in adjacent composite crystal layers are staggered; and/or the second scintillation crystals in adjacent composite crystal layers are staggered.

8. The crystal array detector of claim 1, further comprising a plurality of third scintillation crystals of a third type in the composite crystal layer, the plurality of third scintillation crystals dispersed among the plurality of first scintillation crystals and the plurality of second scintillation crystals and in close proximity to adjacent scintillation crystals, each of the plurality of third scintillation crystals having a third scintillation decay time that is different from the first scintillation decay time and the second scintillation decay time.

9. The crystal array detector of claim 8, wherein a top corner of each type of scintillation crystal abuts a different type of scintillation crystal in the composite crystal layer.

10. The crystal array detector of any of claims 1-7, wherein sides of each type of scintillation crystal abut a different type of scintillation crystal in the composite crystal layer.

11. The crystal array probe of any of claims 1-9, wherein the crystal arrays are plural and arranged in sequence along the longitudinal direction, each crystal array having a corresponding array light reflecting layer and a light sensor layer,

the light sensor layer corresponding to one of the two adjacent crystal arrays and the array light reflecting layer corresponding to the other of the two adjacent crystal arrays are arranged opposite to each other.

12. An emission imaging apparatus, comprising:

a plurality of detectors enclosing to form a detection cavity for accommodating an object to be detected, at least a part of the detectors being the crystal array detector according to any one of claims 1-11, an incident surface of the crystal array detector facing the detection cavity; and

a processor configured to determine a mixed energy deposition event from the photo-electric signals collected by the photosensor layer, wherein the photo-electric signals are generated based on the first and second scintillation decay times, and the mixed energy deposition event is an event in which energy deposition occurs in all of the different types of scintillation crystals.

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