Medical image diagnostic device and medical information processing method

Abstract

To improve accuracy of real-time determination of scattering events.SOLUTION: A medical image diagnostic apparatus includes a processing unit configured to detect a first event and a second event of gamma rays detected by a plurality of detector crystals. When the second event is within a time window determined on the basis of the first event and satisfies a constraint relating to position information determined on the basis of a detected position of the first event, the processing unit is configured to classify the second event into the same first cell of the first event and a demultiplexer. When the second event does not satisfy at least one of the time window and the constraint relating to the position information, the processing unit is configured to classify the second event into a second cell of the demultiplexer different from the first cell.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The embodiments disclosed in this specification and the drawings relate to a medical image diagnostic apparatus and a medical information processing method. [Background technology]

[0002] Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) are functional imaging modalities capable of imaging biochemical processes in humans and animals using radioactive tracers. For example, in PET imaging, a tracer agent is introduced into the patient to be imaged by injection, inhalation, or ingestion. After administration, the tracer agent is concentrated in a specific location in the patient's body as a function of its physical and biomolecular properties. The actual spatial distribution of the tracer agent, the intensity of the accumulation area, and the kinetics of the process from administration to its eventual disappearance are all factors that have clinical significance.

[0003] During the above process, the tracer attached to the tracer agent emits a positron. When the emitted positron collides with an electron, an annihilation event occurs, in which the positron and the electron combine. In most cases, the annihilation event produces two gamma rays (511 keV) traveling approximately 180 degrees apart.

[0004] In positron emission tomography (PET), the measured coincidence factor includes both true coincidence factor and background signal (e.g., accidental coincidence factor). To improve the image quality in the reconstructed PET signal, it is desirable to estimate and account for this background signal. The background signal includes counts due to accidental events and scattering events. The background signal in PET is mainly composed of accidental coincidence counts (also called accidental) and scattering.

[0005] Although most of the scattered photons in the body are not detected at the detection surface, some scattered photons are detected and recorded, resulting in an inaccurate line-of-response (LOR). This scattering event occurs in the detector crystal when some energy is scattered from the first crystal that receives the radiation and deposited in an adjacent crystal. In some embodiments, some of the scattering events that cause the inaccurate LOR can be removed by energy discrimination. This is because some of the photon's energy is lost during the Compton scattering that causes the scattering event. Even then, some scattered photons (scattering) and some accidental coincidences (accidental) are inevitably recorded, so the background signal contains accidental and scattering. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 7,567,620 Summary of the Invention [Problem to be solved by the invention]

[0007] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to improve the accuracy of real-time determination of scattering events. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described later can also be positioned as other problems. [Means for solving the problem]

[0008] A medical image diagnostic apparatus according to an embodiment includes a processor configured to detect a first event and a second event of gamma rays detected by a plurality of detector crystals, the processor classifying the second event into the same first cell of a demultiplexer as the first event when the second event is within a time window determined based on the first event and satisfies a constraint on position information determined based on a detection position of the first event, and classifying the second event into a second cell of the demultiplexer different from the first cell when the second event does not satisfy at least one of the constraints on the time window and the position information. [Brief description of the drawings]

[0009] [Figure 1A] FIG. 1A is a schematic diagram of a transaxial section of a PET scanner according to one embodiment. [Figure 1B] FIG. 1B illustrates normalization of efficiency in the axial domain of a first crystal according to one embodiment of the present disclosure. [Figure 1C] FIG. 1C is a schematic diagram illustrating detection in the absence of scattering, according to one embodiment. [Figure 1D] FIG. 1D is a schematic diagram illustrating detection involving a single scattering event, according to one embodiment. [Figure 1E] FIG. 1E is a schematic diagram illustrating detection involving multiple scattering events according to one embodiment. [Figure 1F] FIG. 1F is a schematic diagram illustrating zoning of a detector block according to one embodiment. [Diagram 2] FIG. 2 is a block diagram illustrating an assembled demultiplexer module according to one embodiment. [Diagram 3] FIG. 3 is a block diagram illustrating a cell of a parameterized plurality of cells according to one embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of an event stream according to one embodiment. [Diagram 5] FIG. 5 illustrates a demultiplexer module assembled for a first event according to one embodiment. [Figure 6] FIG. 6 is a schematic diagram illustrating a first zone assignment for a first event according to one embodiment. [Figure 7] FIG. 7 illustrates an assembled demultiplexer module when triaging an event according to one embodiment. [Figure 8] FIG. 8 is a schematic diagram illustrating further zone allocation according to one embodiment. [Figure 9] FIG. 9 is a block diagram illustrating an assembled demultiplexer module upon detection of a scattering event according to one embodiment. [Figure 10] FIG. 10 is a schematic diagram illustrating zonal allocation of scatter events according to one embodiment. [Figure 11] FIG. 11 is a block diagram illustrating an assembled demultiplexer module upon detection of a scattering event, according to one embodiment. [Figure 12] FIG. 12 is a schematic diagram illustrating zonal allocation of scatter events according to one embodiment. [Figure 13] FIG. 13 is a block diagram illustrating an assembled demultiplexer module upon detection of a scattering event according to one embodiment. [Figure 14] FIG. 14 is a schematic diagram illustrating zonal allocation of scatter events according to one embodiment. [Figure 15] FIG. 15 is a block diagram illustrating an assembled demultiplexer module upon detection of a new primary event according to one embodiment. [Figure 16] FIG. 16 is a diagram illustrating a schematic of zone assignment for a new primary event according to one embodiment. [Figure 17] FIG. 17 illustrates a non-limiting example flow chart of a method for classifying a detected event according to one embodiment. [Figure 18A] FIG. 18A is a perspective view of a Positron Emission Tomography (PET) scanner, according to one embodiment. [Figure 18B] FIG. 18B is a schematic diagram illustrating a PET scanner, according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of a medical image diagnostic apparatus and a medical information processing method will be described in detail with reference to the accompanying drawings.

[0011] In one embodiment, a medical imaging diagnostic apparatus and a medical information processing method are described that include a parameterized cell-based circular sorting algorithm based on timestamp and location to improve energy correction sensitivity, system performance, and reconstructed image quality.

[0012] The following disclosure provides various embodiments (or examples) embodying various features of the subject matter of this specification. Specific examples of components and configurations are described below to facilitate understanding of the present disclosure, but it should be understood that these are merely examples and are not limiting. For example, the formation of a first feature on a second feature in the following description includes an embodiment in which the first and second features are formed in direct contact with each other, and an embodiment in which an additional feature is formed between the first and second features such that the first and second features are not in direct contact with each other. In addition, the present disclosure repeats reference numerals and / or characters in various examples. This repetition is for the purpose of brevity and clarity, and does not in itself indicate a relationship between the various embodiments and / or configurations described herein. Furthermore, spatial relationship terms such as "above," "below," "directly below," "below," "below," "above," and "above" are used herein to facilitate description in describing the relationship of a component or feature shown in the figures to another component or feature. These spatial relationship terms include various orientations of the device in use or operation in addition to the orientations shown in the figures. The system may be oriented in other orientations than those shown (rotated 90 degrees or at other orientations) and the meaning of the spatial relationship descriptors used herein should be interpreted accordingly.

[0013] The order in which the various steps are described herein is for clarity of explanation. In general, the steps may be performed in any suitable order. Moreover, although various aspects, techniques, configurations, etc. are described herein in various places in this disclosure, these concepts may be performed independently or in combination with each other. Thus, the present invention may be embodied in various ways and interpreted in various ways.

[0014] 1A is a schematic diagram of a transaxial section of a PET scanner 100 according to an embodiment of the present disclosure. In one embodiment, the PET scanner 100 includes detector blocks 130 arranged in a ring around a central axis and configured to detect gamma rays. The PET scanner 100 includes a ring of additional detector blocks 130 along the axis of the ring along which the detector blocks 130 are disposed. Further configurations of the PET scanner 100 are shown in FIGS. 18A and 18B, which are described below in the accompanying discussion. A subject 110 to be scanned, such as a phantom or human, is positioned in the center of the detector blocks 130.

[0015] 1B is a schematic diagram illustrating a detector module 125 according to one embodiment of the present disclosure. The detector module 125 is shown as a top view of one of the flattened rings. The detector module 125 includes multiple sub-modules 120. The sub-modules 120 include multiple detector blocks 130. The detector blocks 130 include multiple detector crystals 105, also referred to as detector elements.

[0016] As mentioned above, when a positron emitted from a phantom or human collides with an electron, an annihilation event occurs in which the positron and the electron combine. In most cases, this annihilation event generates two gamma rays (511 keV) that move approximately 180 degrees apart. One of these gamma rays is called a single 115. To reconstruct the spatial and temporal distribution of the tracer by tomographic reconstruction principles, each detection event is characterized by its energy (amount of light generated), location, and timing. By detecting the two gamma rays (the two singles 115) and drawing a line connecting their locations (i.e., a line of coincidence (LOR)), the location where the first decay is believed to have occurred can be determined. A set of singles 115 that now move approximately 180 degrees apart from the location of the annihilation event is called a pair.

[0017] 1C, 1D, and 1E are schematic diagrams illustrating detection in the absence of scattering, detection with a single scattering event, and detection with multiple scattering events, according to an embodiment of the present disclosure.

[0018] In one embodiment, when the solitons 115 are absorbed by the detector module 125, the energy of the solitons 115 (i.e., gamma rays) is deposited in the first crystal 105a. In an ideal detection event, no further scattering occurs and the solitons 115 are recorded in the first crystal 105a as an event at the position of the first crystal 105a where they entered (FIG. 1C). Ideally, a crystal facing the first crystal 105a in the detector module 125 detects the solitons 115 moving approximately 180 degrees away from the position of the annihilation event, and the correct LOR is determined. Also, ideally, the detection energy of each solitons 115 is measured to be approximately 511 keV. In addition to the position and energy of the detected solitons 115, the time of detection (e.g., a timestamp) is recorded with the detection event. This detection is considered to be exclusively based on the photoelectric effect.

[0019] However, in many cases, some of the energy of the singular 115 is scattered (e.g., Compton scattering) and deposited in another crystal, e.g., the second crystal 105b adjacent to the first crystal 105a (FIG. 1D). In this scenario, a second detection event is recorded with a second unique energy, location, and timestamp. This detection is considered to be based on a mixture of Compton and photoelectric effects. Each cell of the demultiplexer described below can perform a classification of two events for the detected gamma ray, representing a single Compton scattering event after the primary event as shown in FIG. 1D. The scattering of the singular 115 can occur many more times. For example, as shown in FIG. 1E, two scattering events occur from the first crystal 105a to the second crystal 105b, and from the second crystal 105b to another crystal, e.g., the third crystal 105c adjacent to the second crystal 105b. In this scenario, a third detection event is recorded having a third unique energy, location and timestamp. Each cell of the demultiplexer described below is capable of three event classifications of detected gamma rays, representing double Compton scatter events after the primary event as shown in FIG. 1E.

[0020] FIG. 1F is a schematic diagram showing zone assignments of detector blocks 130 according to an embodiment of the present disclosure. The zone assignments of detector blocks 130 shown in FIG. 1F are an example of constraints on position information. In one embodiment, multiple detector blocks 130 are combined to form a zone. The size of the zone is adjusted based on the number of detector blocks 130 classified into the zone. For example, two detector blocks 130 are combined to form a base zone (a zone indicated by the number "0" in FIG. 1F). Zones of this size are further combined to form a cross-shaped zone that is extended vertically and horizontally. This is the first extended zone (an extended portion indicated by the number "1" in FIG. 1F (which also includes the base zone)). Similarly, the corners of this cross-shaped zone are filled by further combinations to form a second extended zone (an extended portion indicated by the number "2" in FIG. 1F (which also includes the base zone and the first extended zone)). Additional extended portions may be added. These zones are formed and adjusted to group detection events to capture all possible scattering events.

[0021] In addition, although the case where multiple detector crystals are classified into multiple detector blocks is shown in FIG. 1F, the embodiment is not limited to this. That is, the constraint on the position information may be set regardless of the classification into detector blocks. For example, a zone formed by multiple detector crystals included within a predetermined distance from the position of the first crystal 105a may be set as a constraint on the position information.

[0022] Discarding an event due to accumulation of scattered energy reduces the sensitivity of the single 115 by approximately 30% and the sensitivity of the pair by approximately 50% (the efficiency of the single 115 is squared). As described herein, the "information" (energy) scattered from the primary incidence is recovered by assembling multiple events of detector data based on timestamp and position. This assembly mode increases the energy correction sensitivity of the PET device, thus improving device performance and image quality.

[0023] 2 is a block diagram illustrating an assembled demultiplexer module according to one embodiment of the present disclosure, the assembled demultiplexer module being formed around a number of parameterized cells 205. The assembled demultiplexer module also includes a number of the parameterized cells 205.

[0024] 3 is a block diagram illustrating a cell of a plurality of parameterized cells 205 according to one embodiment of the present disclosure. The parameterized cell 205 can make its own decisions based on predefined settings, such as time windows, zone allocations, and the number of events that can be collected within a time window or zone allocation.

[0025] In one embodiment, a predetermined number of parameterization cells 205 instantiated in the assembled module is calculated based on the time window setting. The parameterization cells 205 are connected inversely in parallel to form a circular operation chain, which allows real-time processing with minimal resources. An event pointer provides an access point to the event stream. That is, the event pointer is a rotating data pointer that indicates the first entry position in the cell pipeline. The event pointer sends all events in the event stream to the active parameterization cell 205 in the active time window. When a time window ends, the pointer moves to the next parameterization cell 205 in the chain and sends all events to the active parameterization cell 205. Within a given time window, the parameterization cell 205 determines whether the event under investigation should be kept or sent to the next parameterization cell 205. When the time window for the corresponding parameterization cell 205 ends, the corresponding parameterization cell 205 sends all assembled events in the parameterization cell 205. This parameterization cell 205 can group the maximum number of detected events. This maximum number can be increased or decreased.

[0026] The predetermined number of parameterization cells 205 is determined by the maximum number of consecutive events compared to the primary event. The maximum number is determined by the maximum event rate (expected with standard deviation), the disparity, and the maximum time window. In one example, the disparity (i.e., the multiplicity of events) is 1.16, the standard deviation of the number of secondary scattering events is √0.16 or 0.4, and the 4σ window containing all secondary scattering events together with the primary detection events is 1+0.4×4 or 2.6. In the same example, the number of background events mixed with the useful events is given by the average number of background events in a time window that is 144 MHz×10 ns or 1.44, the standard deviation from a Poisson distribution is √1.44 or 1.2, and the 4σ confidence level based on detection events falling within one quadrant of the maximum time window is 1.2×4 or 4.8. Thus, 2.6 and 4.8 add up to 7.4, rounded up to 8. That is, the ninth event is outside the time window of the first event, and the number of grouped cells is five.

[0027] 4 is a diagram illustrating an example of an event stream according to one embodiment of the present disclosure. In this embodiment, all events are shown at the top of Fig. 4, and categorized events are shown below. Event sorting will now be described.

[0028] FIG. 5 is a diagram illustrating a demultiplexer module assembled for a first event according to an embodiment of the present disclosure. In one embodiment, when a first event is input, a first parameterization cell 205a is instantiated with a first time window based on the detection time of the first event. The first time window (as well as other time windows described herein) is a predetermined length of time during which additional events may occur and be considered as scattered events derived from the first event (or each event in the time window). The first parameterization cell 205a captures the first event and designates it as a primary event. FIG. 6 is a schematic diagram illustrating a first zone assignment for the first event according to an embodiment of the present disclosure. The first parameterization cell 205a further creates a first zone assignment. The size (range) and location of the first zone assignment are determined based on the detection location of the first event for comparison with subsequent input events. As shown, the first zone assignment for the first event consists of nine detector blocks 130 arranged in a three by three rows, with the first event being placed in the center one of the detector blocks 130. As shown in FIG. 1F, different sizes of the zone assignments can provide different sensitivity and flexibility in determining whether a detected event is a primary event or a scatter event.

[0029] A detected event is determined to be a scattered event if (1) the detection time of the event is within a first time window and (2) the event is detected within a first zone allocation. That is, for condition (1), the difference between the detection time of the first event and the detection time of the scattered event is less than the first time window. For example, by increasing the size of the zone allocation, more detected events will satisfy condition (2).

[0030] In the above setup, after a second event is detected and evaluated by the first parameterization cell 205a (the active parameterization cell), the second event is rejected by the first parameterization cell 205a unless it satisfies both of the above conditions (1) and (2), i.e., the first parameterization cell 205a determines that the second event is a primary event rather than a scattered event.

[0031] FIG. 7 illustrates an assembled demultiplexer module when triaging events according to an embodiment of the present disclosure. FIG. 8 illustrates a schematic diagram of further zone assignments according to an embodiment of the present disclosure. In an embodiment, if conditions (1) and (2) are not satisfied, a second parameterization cell 205b is instantiated with a second time window based on the time of detection of a second event, which is determined to be a primary event. Similarly, if conditions (1) and (2) are not satisfied, a third parameterization cell 205c is instantiated with a third time window based on the time of detection of a third event, which is determined to be a primary event. As shown in FIG. 8, the second and third events are detected outside the first zone assignment of the first event. The second parameterization cell 205b further creates a second zone assignment. The size (range) and location of the second zone assignment are determined based on the detection location of the second event for comparison with subsequent input events. Similarly, the third parameterization cell 205c further creates a third zone assignment. The size (extent) and location of the third zone assignment is determined based on the detection location of the third event for comparison with subsequent input events. As shown in Figure 8, the zone assignments for the second and third events are similar in size and shape to the first event, and the detection locations of each event are centrally located, similar to the first event.

[0032] FIG. 9 is a block diagram illustrating an assembled demultiplexer module upon detection of a scattered event according to an embodiment of the present disclosure. FIG. 10 is a schematic diagram illustrating a zone assignment of a scattered event according to an embodiment of the present disclosure. In one embodiment, an event pointer designates the first parameterization cell 205a as the active parameterization cell. A fourth event is detected and evaluated by the active parameterization cell, for example the first parameterization cell 205a, and determined to be located within the first time window and within the first zone assignment of the first event. In this manner, the fourth event is determined to be a scattered (secondary) event derived from the first event and classified in the same manner as the first event.

[0033] FIG. 11 is a block diagram illustrating an assembled demultiplexer module upon detection of a scattered event according to an embodiment of the present disclosure. FIG. 12 is a schematic diagram illustrating a zone assignment of a scattered event according to an embodiment of the present disclosure. In an embodiment, a fifth event is detected and evaluated by an active parameterization cell, for example the first parameterization cell 205a, to determine that it is outside of either the first time window or the first zone assignment. The fifth event information is then evaluated by the second parameterization cell 205b to determine that it is outside of either the second time window or the second zone assignment. The fifth event information is then evaluated by the third parameterization cell 205c to determine that it is within the third time window and the third zone assignment. In this manner, the fifth event is determined to be a scattered (secondary) event derived from the third event and classified in the same manner as the third event.

[0034] FIG. 13 is a block diagram illustrating an assembled demultiplexer module upon detection of a scattered event according to an embodiment of the present disclosure. FIG. 14 is a schematic diagram illustrating a zone assignment of a scattered event according to an embodiment of the present disclosure. In one embodiment, a sixth event is detected and evaluated by an active parameterization cell, for example the first parameterization cell 205a, and determined to be outside of either the first time window or the first zone assignment. The sixth event information is then evaluated by the second parameterization cell 205b and determined to be within the second time window and the second zone assignment. In this manner, the sixth event is determined to be a scattered (secondary) event derived from the second event and classified in the same manner as the second event.

[0035] In one embodiment, when the sixth event is detected, the event pointer is incremented to designate the second parameterization cell 205b as the active cell when the sixth event is determined to be detected beyond the length of the first time window. In this manner, the sixth event is skipped from evaluation by the first parameterization cell 205a so that the time window is closed to all possible additional scattering events derived from the first event. Furthermore, when the event pointer is incremented to the second parameterization cell 205b, all captured detected event data from the first parameterization cell 205a is sent. For example, the captured detected event data is sent to an assembled event formatter and then to a centralized controller for further processing. Thereafter, the first parameterization cell 205a is determined to be empty and ready to accept the next detected event data.

[0036] FIG. 15 is a block diagram illustrating an assembled demultiplexer module upon detection of a new primary event according to an embodiment of the present disclosure. FIG. 16 is a schematic diagram illustrating a zone assignment of a new primary event according to an embodiment of the present disclosure. In an embodiment, a seventh event is detected and evaluated by an active parameterization cell, for example, the second parameterization cell 205b, and determined to be outside of either the second time window or the second zone assignment. The seventh event information is then evaluated by the third parameterization cell 205c and determined to be outside of either the third time window or the third zone assignment. Thus, if conditions (1) and (2) are not satisfied and the seventh event is determined to be a primary event, a fourth parameterization cell 205d is instantiated with a fourth time window based on the detection of the seventh event. The fourth parameterization cell 205d further creates a fourth zone assignment. The size (range) and location of the fourth zone assignment are determined based on the detection location of the seventh event for comparison with subsequent input events.

[0037] In one embodiment, when the detection of the seventh event is determined to be a time beyond the length of the second time window, the event pointer is incremented to designate the third parameterization cell 205c as the active cell. In this manner, the seventh event is skipped from evaluation by the second parameterization cell 205b so that the time window is closed to all possible additional scattering events derived from the second event. Furthermore, when the event pointer is incremented to the third parameterization cell 205c, all captured detection event data is transmitted from the second parameterization cell 205b.

[0038] In one embodiment, the processing circuit performs the above-mentioned steps, i.e., detecting the events, sorting the events, and assigning the events to the corresponding cells in the assembled demultiplexer module. For example, the processing circuit is implemented in an FPGA to facilitate real-time processing. It is noted that such a processing circuit is an example of a processing unit. The FPGA uses a cell module in which identical parameterized cells are cascaded in a pipelined manner, where the last cell in the chain circle returns to the first cell when the time window corresponding to the last cell closes for the last cell. Furthermore, the processing circuit (e.g., in the FPGA) is communicatively connected to the PET scanner 100 and is located in close proximity to the detector array 130 to further facilitate real-time processing. This provides a scalable solution without requiring either internal or external memory. The cell chain skeleton also eliminates the need for additional resources (comparators, RAM), simplifying the logic and allowing faster data transfer.

[0039] Note that the parameterized cells 205 are time-aware cells: in the case of an event followed by a long pause in the input event stream, the active parameterized cell accepts the event as a primary event and, once the time window has elapsed, sends the information of the event (and all related events) to its output while incrementing the event pointer to the next parameterized cell 205. Furthermore, the parameterized cell 205 processes input events from previous cells with priority over input events from the event pointer. In this case, the event present at the event pointer port is held for one clock cycle before being read into the target parameterized cell 205.

[0040] When events are discarded due to accumulation of scattered energy, the sensitivity of the single 115 decreases by about 30% and the sensitivity of the pair decreases by about 50% (the efficiency of the single 115 is squared).

[0041] Data including undiscarded scatter events, which are more sensitive to both singles 115 and pairs, can be effectively utilized to reconstruct a more accurate final image of the scanned subject, thereby improving diagnosis and other medical procedures.

[0042] In summary, events can be input in streaming order and processed in real-time without piping, buffering or delays. The circular nature of this mechanism (when a time window closes, the active parameterized cell becomes the last parameterized cell in the concatenated chain) allows for optimization of resources (e.g. FPGA resources) and improves throughput.

[0043] FIG. 17 illustrates a non-limiting example flow chart of a method 1700 for classifying detected events, according to an embodiment of the present disclosure. In step 1705, a first event is detected at a first crystal 105a. In step 1710, the first event is assigned to a first parameterization cell 205a. In step 1715, a first time window for the first event is determined. In step 1720, a position of the first detector block in the detector block 130 is determined. In step 1725, a first zone assignment for the first event is determined. In step 1730, a second event is detected at a second crystal (which may not be the same as the second crystal 105b). In step 1735, it is determined whether the second event can be classified with the first event based on the detection time and detection position of the second event. If the second event is detected within the first time window and within the first zone assignment of the first event, in step 1740, the second event is classified with the first event into the first parameterization cell 205a. If not, then in step 1745 the second event is assigned to a second parameterization cell 205b of the demultiplexer. In step 1750 a second time window for the second event is determined. In step 1755 a location of a second detector block in detector block 130 is determined. In step 1760 a second zone assignment for the second event is determined. In step 1765 it is determined whether there are more detected events. If there are more detected events, method 1700 repeats from step 1730. If not, method 1700 ends.

[0044] 18A and 18B show a non-limiting example of a PET scanner 1800 in which methods 100 and 200 can be implemented. The PET scanner 1800 is an example of a medical imaging device. The PET scanner 1800 includes a number of Gamma-Ray Detectors (GRDs) (e.g., GRD1-GRDN), each configured as a rectangular detector module. In one embodiment, the detector ring includes 40 GRDs. In another embodiment, there are 48 GRDs. The more GRDs used, the larger the inner diameter of the PET scanner 1800.

[0045] Each GRD consists of a two-dimensional array of individual detector crystals. Each detector crystal absorbs gamma radiation and emits scintillation photons. The scintillation photons are detected by a two-dimensional array of photomultiplier tubes (PMTs) arranged in the GRD as well as the detector crystals. A light guide is placed between the detector crystal array and the PMT array.

[0046] Alternatively, the scintillation photons are detected by an array of Silicon Photomultipliers (SiPMs) associated with each detector crystal.

[0047] Each photodetector (e.g., PMT or SiPM) generates an analog signal indicating when a scintillation event occurred and the energy of the gamma ray that caused the detection event. Alternatively, photons emitted from a detector crystal can be detected by two or more photodetectors, and based on the analog signals generated by each photodetector, the detector crystal corresponding to the detection event can be determined using, for example, Anger Logic crystal position calculations.

[0048] FIG. 18B is a schematic diagram of a PET scanner device with multiple gamma-ray photon counting detectors (GRDs) arranged to detect gamma rays emitted from an object OBJ. The GRDs can measure the timing, position, and energy corresponding to each gamma-ray detection. In one embodiment, the gamma-ray detectors are arranged in a ring as shown in FIGS. 18A and 18B. The detector crystal is made of a scintillator crystal that is a two-dimensional array of individual scintillator elements. The scintillator elements are made of any known scintillation material. The PMTs are arranged such that light from each scintillator element is detected by multiple PMTs, allowing for Anger logic crystal position calculation of scintillation events.

[0049] In the arrangement example of the PET scanner 1800 shown in Fig. 18B, the object OBJ to be imaged is placed on a table 1816, and the GRD modules GRD1-GRDN are arranged around the object OBJ and the table 1816. Each GRD is fixedly connected to an annular member 1820, which is fixedly connected to a gantry 1840. The gantry 1840 houses many components of the PET imaging device. The gantry 1840 of the PET imaging device is also provided with an open opening, through which the object OBJ and the table 1816 are transported. Gamma rays emitted in opposite directions from the object OBJ due to an annihilation event are detected by the GRD. Furthermore, the coincidence counts of the gamma ray pairs are determined using timing information and energy information.

[0050] The circuitry and hardware shown in FIG. 18B also captures, stores, processes, and partitions gamma ray detection data. The circuitry and hardware includes a processor 1870, a network controller 1874, a memory 1878, and a Data Acquisition System (DAS) 1876. The PET imaging device also includes a data channel through which detection and measurement results are sent from the GRD to the DAS 1876, the processor 1870, the memory 1878, and the network controller 1874. The DAS 1876 controls the capture, digitization, and routing of detection data from the detector. In one embodiment, the DAS 1876 controls the movement of the bed 1816. The processor 1870 performs functions such as image reconstruction from detection data, pre-reconstruction processing of detection data, and post-reconstruction processing of image data, as described herein.

[0051] The processor 1870 is configured to perform various steps and variations of the methods 100 and / or 200 described herein. That is, the processor 1870 is an example of a demultiplexer. The processor 1870 includes a CPU implemented as discrete logic gates, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or other Complex Programmable Logic Device (CPLD). The FPGA or CPLD implementation is coded in VHDL, Verilog, or other hardware description language, and the code is stored in electronic memory embedded in the FPGA or CPLD or in a separate electronic memory. The memory may also be a non-volatile memory such as a ROM, EPROM, EEPROM, or Flash memory. The memory may also be a volatile memory such as a static RAM or a dynamic RAM. A processor such as a microcontroller or microprocessor may be provided to control the electronic memory and the interaction of the FPGA or CPLD with the memory.

[0052] Alternatively, the CPU of the processor 1870 may execute a computer program including a set of computer readable instructions for performing each step of the method 100 and / or 200. The program may be stored in the non-transitory electronic memory and / or a hard disk drive, a CD, a DVD, a flash drive, or any other storage medium known in the art. Furthermore, the computer readable instructions may be provided as a utility application, a background daemon, a component of an operating system, or a combination thereof, and executed in conjunction with a processor such as Xenon processors manufactured by Intel, Inc., Opteron processors manufactured by AMD, Inc., Microsoft VISTA, UNIX, Solaris, LINUX, Apple, MAC-OS, and other operating systems known to those skilled in the art. Furthermore, the CPU may be implemented as multiple processors that execute instructions in a parallel, cooperative manner.

[0053] Although the various steps and variations of the methods 100 and / or 200 described above are executed in the processor 1870, the embodiments are not limited thereto. For example, the various steps and variations of the methods 100 and / or 200 described above may be executed in the DAS 1876. That is, the DAS 1876 may function as a demultiplexer. By locating the demultiplexer closer to the output of each GRD, it is possible to more quickly determine the scattering event.

[0054] Memory 1878 may comprise a hard disk drive, a CD-ROM drive, a DVD drive, a flash drive, RAM, ROM, or any other type of electronic storage device known to those of skill in the art.

[0055] A network controller 1874 (such as an Intel Ethernet PRO network interface card manufactured by Intel Corporation, USA) interfaces the various components of the PET imaging device with each other. The network controller 1874 also interfaces with an external network. As is well known, the external network may be a public network such as the Internet, a private network such as a LAN or WAN network, or any combination thereof. Also, there may be PSTN or ISDN sub-networks. The external network may be a wired network such as an Ethernet network, or a wireless network such as a cellular network such as EDGE, 3G, 4G, and 5G wireless cellular systems. Also, there may be wireless networks such as WiFi, Bluetooth, or any other wireless communication method known in the art.

[0056] Although the above description provides specific details, such as a particular arrangement of the processing system and a description of the various components and processes used in the system, it will be apparent that the techniques described herein may be practiced in other embodiments that depart from these specific details, and that these specific details are provided for purposes of explanation and not limitation.

[0057] For example, the above embodiment has been described with the PET imaging device as an example, but the present invention can be applied to a SPECT imaging device as well. For example, the SPECT imaging device includes a detector (gamma camera) for detecting gamma rays, and a first event and a second event of gamma rays are detected by a plurality of detector crystals of the detector. The SPECT imaging device also includes a processing unit similar to the above processor 1870. When the second event is within a time window determined based on the first event and satisfies a constraint on position information determined based on the detection position of the first event, the processing unit can classify the second event into the same first cell of the demultiplexer as the first event, and when the second event does not satisfy at least one of the constraints on the time window and the position information, the processing unit can classify the second event into a second cell of the demultiplexer different from the first cell.

[0058] The embodiments of the present disclosure have been described with reference to the accompanying drawings. Similarly, for the purpose of explanation, specific numbers, materials, and configurations have been described to ensure sufficient understanding. However, each embodiment can be implemented without including these specific details. In addition, multiple components having substantially the same functional configuration are given the same reference numerals, and redundant description is omitted.

[0059] Although the various techniques have been described as multiple discrete operations to facilitate understanding of the embodiments, the order of description does not necessarily imply that the operations are order dependent. In practice, the operations may not be performed in the order described. Also, the described operations may be performed in a different order than in the embodiments described above. Various additional operations may be performed and / or the described operations may be omitted in additional embodiments.

[0060] At least one of the embodiments described above can improve the accuracy of real-time determination of scattering events.

[0061] Although some embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations of embodiments can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0062] 1800 PET Scanner 1870 Processor

Claims

1. A medical image diagnostic device comprising a processing unit configured to detect a first event of a gamma ray detected by a plurality of detector crystals and a second event which is an event detected by the plurality of detector crystals after the first event, The processing unit includes: classifying the second event into the same first cell of a demultiplexer as the first event if the second event is within a time window of a predetermined length from the detection time of the first event and within a zone allocation set around the detection position of the first event; If the second event does not satisfy at least one of the time window and the zone assignment, the second event is classified into a second cell of the demultiplexer that is different from the first cell.

2. The processing unit includes: detecting the first event at a first detector crystal in the plurality of detector crystals, the first event including first time information, first energy information, and first position information; assigning the first event, the first time information, the first energy information, and the first location information to the first cell; determining, based on the first time information, a first time window having a predetermined time length as the time window; determining, based on the first position information, a first zone assignment including the first detector crystal as the zone assignment; detecting the second event at a second detector crystal, the second event comprising second time information, second energy information, and second position information; determining whether the second event is detected within the first time window and within the first zone assignment based on the second time information and the second location information; classifying the second event, along with the first event, in the first cell as a scattering event of the first event when the second event is determined to be detected within the first time window and within the first zone assignment; The medical image diagnostic apparatus of claim 1 , wherein the second event is classified as a primary event into the second cell if the second event does not satisfy at least one of the first time window and the first zone assignment.

3. The plurality of detector crystals are grouped into a plurality of detector blocks; The processing unit includes:

3. The medical imaging diagnostic device of claim 2, further comprising: a first detector block including the first detector crystal, the first zone assignment including at least the first detector block and defining a region around the first detector block within which further events may be detected and associated with the first event, the first zone assignment being determined based on the first position information.

4. The processing unit includes: determining an activity status of the first cell based on the first time window, and specifying an event pointer to send a detected event to the first cell when the first cell is active; 4. The medical image diagnostic device according to claim 2, wherein when it is determined that a third event including third time information is detected outside a predetermined time length of the first time window, the designation by the event pointer is assigned to the second cell, and the information in the first cell of the demultiplexer is transmitted to a receiving device.

5. The medical image diagnostic apparatus according to claim 4 , wherein the processing unit reconstructs an image based on a data set including the information in the first cell of the demultiplexer.

6. The processing unit includes: if the second event does not satisfy at least one of the first time window and the first zone assignment; determining a second time window having the predetermined length of time based on the second time information of the second event; 4. The medical imaging diagnostic device of claim 3, further comprising: a second detector block including the second detector crystal, the second detector block being positioned relative to the second detector crystal; and a second zone assignment including at least the second detector block and defining an area around the second detector block within which further events may be detected and associated with the second event.

7. the processing unit is communicatively connected to the detector array and disposed substantially proximate to the detector array; A medical imaging diagnostic device according to any one of claims 1 to 6, which detects a new event, determines whether the new event is detected within the time window and within a zone assignment of a previous detected event, and assigns the new event to a cell of the demultiplexer each time a gamma ray is detected.

8. The medical image diagnostic apparatus according to any one of claims 1 to 7, wherein the demultiplexer is realized by at least one of the group consisting of an FPGA, an ASIC, and an EEPROM.

9. 9. The medical image diagnostic apparatus according to claim 1, wherein each cell of the demultiplexer performs a classification of two events relating to the gamma rays, the classification representing a single Compton scattering event after a primary event.

10. 9. The medical image diagnostic apparatus according to claim 1, wherein each cell of the demultiplexer performs a classification of three events relating to the gamma rays, the classification representing a double Compton scattering event after a primary event.

11. classifying a second gamma ray event detected after the first event at a plurality of detector crystals into the same first cell of the demultiplexer as the first event if the second event is within a time window of a predetermined time length from the detection time of the first gamma ray event and within a zone allocation set around the detection position of the first event; classifying the second event into a second cell of the demultiplexer, different from the first cell, if the second event does not satisfy at least one of the time window and the zone assignment. A medical information processing method comprising:

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