Radiation detector arrangement and method for imaging using a semiconductor detector with determination of the interaction depth

Abstract

Radiation detector arrangement (100) comprising: a semiconductor detector (110) having a surface (112); a plurality of pixelated anodes (114) disposed on the surface (112), each pixelated anode (114) configured to generate a primary signal in response to receipt of a photon (116) by the pixelated anode (114) and to generate at least one secondary signal in response to an induced charge caused by receipt of a photon (116) by at least one of the surrounding anodes (114); and at least one processor (120) operatively connected to the pixelated anodes (114), the at least one processor (120) being configured to: detecting a primary signal from one of the anodes (114) in response to receipt of a photon (116) by said one of the anodes (114); detecting at least one secondary signal from at least one adjacent pixel from said one of the anodes (114) in response to an induced charge caused by the reception of the photon (116) by said one of the anodes (114); and Determining a depth of interaction (DOI) in the semiconductor detector (110) for the reception of the photon (116) by the one of the anodes (114) using the at least one secondary signal; wherein the semiconductor detector (110) has a depth (D) with a first region (I) and with a second region (II), wherein the second region (II) is arranged above the first region (I) and closer to the pixelated anodes (114), wherein an electric field vector in the first region (I) has a downward component and the electric field vector in the second region (II) has an upward component.

Description

BACKGROUND OF THE INVENTION

[0001] The content disclosed herein generally relates to an apparatus and method for diagnostic medical imaging, such as nuclear medicine (NM) imaging.

[0002] In NM imaging, for example, systems with multiple detectors or detector heads can be used to image a subject, for example, to scan a region of interest. For example, the detectors can be positioned adjacent to the subject to acquire NM data, which is used to generate a three-dimensional (3D) image of the subject.

[0003] Image detectors can be used to detect the reception of photons from an object (e.g., a human patient who has been administered a radiotracer) by the image detector. The depth of interaction (DOI), or the position along the thickness of a detector at which photons are detected, can influence the strength of the signals generated by the detector in response to the photons and can be used to determine the number and location of detected events. Accordingly, the DOI can be used to correct the detector signals to improve the resolution and sensitivity of the detector energy. However, conventional approaches to determining DOI use signals from a cathode, which requires additional hardware and setup complexity to use hardware to collect and process cathode signals.In addition, cathodes tend to be relatively large and produce relatively noisy signals, which reduces the accuracy and effectiveness of using signals from cathodes.

[0004] US Patent No. 6,002,741 B1 discloses a method and apparatus for spatially resolving the interaction of a photon with a room-temperature semiconductor detector. The article "Signals induced in semiconductor gamma-ray imaging detectors" by JD Eskin, HH Barrett, and HB Barber presents various methods for the theoretical calculation and simulation of signals induced in semiconductor detectors (Journal of Applied Physics 85, 647 (1999)). BRIEF DESCRIPTION OF THE INVENTION

[0005] In one embodiment, a radiation detector assembly is provided that includes a semiconductor detector, a plurality of pixelated anodes, and at least one processor. The semiconductor detector has a surface. The plurality of pixelated anodes are arranged on the surface. Each pixelated anode is configured to generate a primary signal in response to the pixelated anode receiving a photon and to generate at least one secondary signal in response to an induced charge caused by the at least one surrounding anode receiving a photon.The at least one processor is operatively coupled to the pixelated anodes and is configured to detect a primary signal from one of the anodes in response to receipt of a photon by the one of the anodes; to detect at least one secondary signal from at least one adjacent pixel of the one of the anodes in response to an induced charge caused by receipt of the photon by the one of the anodes; and to determine an interaction depth in the semiconductor detector for receipt of the photon by the one of the anodes using the at least one secondary signal.

[0006] In another embodiment, a method of imaging using a semiconductor detector is provided. The semiconductor detector has a surface with a plurality of pixelated anodes disposed thereon. Each pixelated anode is configured to generate a primary signal in response to receipt of a photon by the pixelated anode and to generate at least one secondary signal in response to an induced charge caused by receipt of a photon by at least one surrounding anode. The method includes detecting a primary signal from one of the anodes in response to receipt of a photon by the one of the anodes, and detecting at least one secondary signal from at least one adjacent pixel of one of the anodes in response to an induced charge caused by receipt of the photons by the one of the anodes.The method also includes determining an interaction depth in the semiconductor detector for reception of the photon by the one of the anodes using the at least one secondary signal.

[0007] In another embodiment, a method comprises providing a semiconductor detector having a surface with a plurality of pixelated anodes disposed thereon. Each pixelated anode is configured to generate a primary signal in response to receipt of a photon by the pixelated anode and to generate at least one secondary signal in response to an induced charge caused by receipt of a photon by at least one adjacent anode. The method also comprises operably coupling the pixelated anodes to at least one processor. Further, the method comprises providing a calibrated radiation source at different depths along a sidewall of the semiconductor detector, wherein the pixelated anodes generate primary signals and secondary signals in response to the calibrated radiation supply.The method further includes capturing the primary signals and the secondary signals from the pixelated anodes with the at least one processor. The method further includes determining the corresponding negative values ​​of the total induced charges for each of the different depths and determining the calibration information based on the negative values ​​of the total induced charges for each of the different depths. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a representation of weighting potentials of a detector with a pixel biased by a voltage potential. Fig. 2 shows four events within the detector of Fig. 1. Fig. 3 shows corresponding induced charges for the four events of Fig. 2. Fig. Figure 4 shows five groups of events under a primary or collecting pixel located at five different DOIs. Fig. Figure 5 shows the resulting uncollected or secondary signals for the events occurring at Z0 from Fig. 4 are located. Fig. Figure 6 shows the resulting uncollected or secondary signals for the events occurring at Z1 from Fig. 4 are located. Fig. Figure 7 shows the resulting uncollected or secondary signals for the events occurring at Z2 from Fig. 4 are located. Fig. Figure 8 shows the resulting uncollected or secondary signals for the events occurring at Z3 from Fig. 4 are located. Fig. Figure 9 shows the resulting uncollected or secondary signals for the events occurring at Z4 from Fig. 4 are located. Fig. 10 shows a calibration system according to various embodiments. Fig. 11 provides a schematic view of a radiation detector arrangement according to various embodiments. Fig. 12 provides a flowchart of a method according to various embodiments. Fig. 13 provides a flowchart of a method according to various embodiments. Fig. 14 provides a schematic view of an imaging system according to various embodiments. Fig. 15 provides a schematic view of an imaging system according to various embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0008] The following detailed description of certain embodiments will be better understood when read in conjunction with the accompanying drawings. To the extent that the figures illustrate diagrams of the functional blocks of various embodiments, the functional blocks are not necessarily indicative of the division between hardware circuits. For example, one or more of the functional blocks (e.g., processors or memory) may be implemented in a single piece of hardware (e.g., a general-purpose signal processor or a block of random access memory, a hard disk, or the like) or in multiple pieces of hardware. Similarly, the programs may be stand-alone programs, may be included as subroutines in an operating system, may be functions in an installed software package, and the like.It is to be understood that the various embodiments are not limited to the arrangements and means shown in the drawings.

[0009] As used herein, the terms "system," "unit," or "module" may encompass a hardware and / or software system that operates to perform one or more functions. For example, a module, unit, or system may include a computer processor, controller, or other logic-based device that performs operations based on instructions stored on a tangible and non-transitory computer-readable storage medium, such as computer memory. Alternatively, a module, unit, or system may include a wired device that performs operations based on the device's wired logic. Various modules or units shown in the accompanying figures may represent hardware operating based on software or wired instructions, software instructing the hardware to perform the operations, or a combination thereof.

[0010] "Systems," "units," or "modules" may include or represent hardware and associated instructions (e.g., software stored on a tangible and non-transitory computer-readable storage medium such as a computer hard disk, ROM, RAM, or the like) that perform one or more operations described herein. The hardware may include electronic circuitry that includes and / or is coupled to one or more logic-based devices such as microprocessors, processors, controllers, or the like. These devices may be commercially available devices that are appropriately programmed or instructed to perform the operations described herein based on the instructions described above. Additionally or alternatively, one or more of these devices may be hard-wired with logic circuitry to perform these operations.

[0011] As used herein, an element or step listed in the singular and preceded by a word such as "a" or "an" should be understood to not exclude a plurality of such elements or steps unless such exclusion is expressly stated. Furthermore, references to "an embodiment" should not be interpreted as excluding the presence of additional embodiments that also include the stated features. Unless expressly stated otherwise, embodiments that "comprise" or "have" one or more elements having a particular characteristic may include additional elements that do not have that characteristic.

[0012] Various embodiments provide systems and methods for improving the sensitivity and / or energy resolution of image acquisition, for example, in nuclear medicine (NM) imaging applications. In various embodiments, measurements of uncollected (or induced) neighboring transition signals are used to determine a depth of interaction (DOI) of corresponding events in a detector. Note that the same measurements of the uncollected neighboring transition signals can also be used to determine corresponding subpixel positions for the events.

[0013] In general, various embodiments provide methods and / or systems for measuring the negative value of induced signals and deriving or determining the corresponding DOI based on the negative value. For certain DOI values ​​(e.g., DOIs not located near an anode), all events with the same DOI produce approximately the same negative value for uncollected induced signals, regardless of their lateral position (with lateral position defined as x, y coordinates, where the DOI is measured along a z-axis). Accordingly, various embodiments use a measured value of induced signals (e.g., a measured negative value of uncollected induced signals, which can also be used for subpixel positioning) to derive or determine the DOI, as well as provide 3D positioning of events causing the uncollected induced signals.

[0014] A technical effect provided by various embodiments includes increased sensitivity and / or energy resolution of a detector system, such as an NM image detector system. A technical effect of various embodiments includes improved image quality. A technical effect of various embodiments includes reduced processing and / or hardware complexity associated with determining DOI via eliminating the use of signals from a cathode.

[0015] Before addressing specific aspects of certain embodiments, certain aspects of detector operation will be explained. Fig. Figure 1 shows a representation 10 of weighting potentials for a detector 11 with a pixelated anode 12 biased by a potential of 1 volt. Neighboring pixelated anodes 13 are unbiased or are at a ground potential of 0 volts. It should be noted that the representation of a given pixelated anode at one voltage, while neighboring pixelated anodes are unbiased in connection with various examples herein, is provided for clarity of illustration and ease of illustration; however, in practice, each pixelated anode of a detector may be biased by a similar voltage. In the Fig. In the example shown in Figure 1, the cathode 14 is grounded at 0 volts. The solid curves 15 represent electric field lines, while dashed curves 16 represent equipotential lines. The equipotential lines run perpendicular to the electric field lines at the points where the lines intersect.

[0016] The weighting potentials of Fig. 1 are plotted according to the Shockley-Ramo theorem. Under this theorem, the induced current generated by the weighting potential is described as i = qE*V = qE*V*cos(a), where i is the induced current, q is the electron charge, E*V is the dot product between the electric field E of the weighting potential and the electron velocity V, and a is the angle between the vectors E and V.

[0017] The Fig. 2 and Fig. 3 show the occurrence of the events in different positions of the detector 11 and the resulting induced charges. Fig. 2 shows four events within the detector 11 from Fig. 1, and Fig. 3 shows corresponding induced charges.

[0018] Fig. Figure 2 shows four events—event 21 starting at a depth of Z0, event 22 starting at a depth of Z1, event 23 starting at a depth of Z2, and event 24 starting at a depth of Z3. Each of the events moves along a curve starting at X1 and ending at the anode of the primary or collecting pixel 25 (the anode that collects the events). The uncollected induced charge on the neighboring pixel (or non-collecting pixel, in this case pixel 12, which in the illustrated example is immediately adjacent to collecting pixel 25) is the integral over time (or over distance) of the current given by the relationship explained above (i = qE*V = qE*V*cos(a)). E is the weighting potential field of the non-collecting neighboring pixel (pixel 12 in this example). Two regions are shown above the depth D of the detector—a first region I and a second region II.

[0019] In region I, the field vector has a downward component. Accordingly, the induced charge across region I is positive. Across region II, the field vector has an upward component. Accordingly, the induced charge across region II is negative. Event 21 at depth Z0 starts at cathode 14, and accordingly, the associated charge travels the entire length of region I and region 11. The other events start away from the cathode, and accordingly, the associated charges do not spread the entire depth of region I. Furthermore, event 24 at depth Z3 starts within the boundary of region II, thus closer to the pixelated anodes than the boundary of region II. Accordingly, the charge related to event 24 at depth Z3 does not travel the entire depth of region II.

[0020] Fig. 3 shows the resulting signals corresponding to the events from Fig. 2. Namely, signal 32 represents the collection or primary signal leading to collection pixel 25. Signal 34 represents the non-collecting signal of pixelated anode 12 resulting from event 21 starting at Z0, signal 35 represents the non-collecting signal of pixelated anode 12 resulting from event 22 starting at Z1, signal 36 represents the non-collecting signal of pixelated anode 12 resulting from event 23 starting at Z2, and signal 37 represents the non-collecting signal of pixelated anode 12 resulting from event 24 starting at Z3.

[0021] As in Fig. 3, for event 21 starting at Z0 (the event occurring at cathode 14 and moving over the entire area of ​​both region I and region II), the total induced charge in regions I and II is zero, since the positively induced charge in region I and the negatively induced charge in region 11 are equal and cancel each other out over the entire depth (e.g., at the anodes with Z = D, where D is the thickness of detector 11).

[0022] For event 22, which starts at Z1 (which is away from the cathode), the total induced charge is negative because the positive induced charge in region I is less than that of event 21, as the charge from event 22 does not traverse the entire depth of region I. Similarly, the total induced charge of event 23 is more negative than the total induced charge of event 22 and the total induced charge of event 24 is more negative than the total induced charge of event 23. This can be represented as [Q0=0]〉[Q1〈0][Q2 〈0]〉[Q3〈0], where Q0 is the total induced charge for event 21 starting at Z0, where Q1 is the total induced charge for event 22 starting at Z1, where Q2 is the total induced charge for event 23 starting at Z2 and where Q3 is the total induced charge for event 24 starting at Z3. Accordingly, as in the Fig. As shown in Figure 3, the closer an event is to the pixelated anodes (or further from the cathode), the more negative the signal from a non-collecting anode.

[0023] Fig. Figure 4 shows five groups of events under a primary pixel 42 (the collection pixel that generates a primary signal) located at five different DOIs: Z0, Z1, Z2, Z3, Z4. Each group includes three events at different X-coordinates (namely X1, X2, and X3) for a given depth. The curves for each event that extends to the primary anode 42 (e.g., anode 25 from Fig. 2) are shown schematically in Fig. 4. These events move in the weighted potential and electric field of the adjacent non-collecting pixel 44 (e.g., anode 12 of Fig. 1 and Fig. 2) on which the uncollected charge is induced, resulting in a secondary signal generated by the adjacent non-collecting pixel 44.

[0024] The resulting induced uncollected or secondary signals generated by each event are shown in the Fig. 5-9. Fig. 5 includes a graph 50 that represents the resulting uncollected or secondary signals for the events located at Z0. As in Fig. As shown in Figure 5, the groups of events at Z0, despite the fact that they have different lateral positions X1, X2, and X3, all produce the same total uncollected induced charge signal, which is zero. Note that all events at Z0 begin at the cathode. Curve 51 in Fig. 5 is the primary collected signal at the primary anode 42 and is in Fig. 5 to help illustrate the differences between the primary signal and the secondary induced signal in terms of amplitude and shape.

[0025] Fig. 6 contains a graph 60 showing the resulting uncollected or secondary signals for the events located at Z1. As in Fig. As can be seen in Figure 6, all events at Z1, despite having different lateral positions X1, X2, and X3, produce the same (or nearly the same) total uncollected induced charge signal, which is negative. Note that all events at Z1 start at a small distance from the cathode and, accordingly, have a relatively small negative induced charge.

[0026] Fig. Figure 7 contains a graph 70 showing the resulting uncollected or secondary signals for the events located at Z2. As in Fig. As shown in Figure 7, all events at Z2, despite having different lateral positions X1, X2, and X3, generate approximately the same total uncollected induced charge signal, which is negative (e.g., within region 72). Note that all events at Z2 begin at a greater distance from the cathode than for the event at Z1 and, accordingly, have a relatively negative induced charge of a relatively small magnitude.

[0027] Fig. Figure 8 contains a graph 80 that represents the resulting uncollected or secondary signals for the events located at Z3. As in Fig. As shown in Figure 8, all events at Z3, despite having different lateral positions X1, X2, and X3, produce approximately the same total uncollected induced charge signal, which is negative (e.g., within region 82). Note that all events at Z3 start at a greater distance from the cathode than for the event at Z2 (and Z1) and, accordingly, have a relatively more negative induced charge of a relatively small magnitude. Note that the difference between the upper and lower values ​​for region 82 and region 72 (see Fig. 7) is small enough to be ignored in various embodiments, so that the DOI is treated as independent of lateral position.

[0028] Fig. Figure 9 contains a graph 90 depicting the resulting uncollected or secondary signals for the events located at Z4. The negative charges for the events originating at a depth of Z4 differ significantly due to the proximity of Z4 to the anodes. In general, in the illustrated example, as the depth of the event moves closer to the anode, the variability of the negatively induced charge based on lateral position increases, with the variability becoming significant only at depths very close to the anode.

[0029] As discussed above, events, with the exception of events that initiate very close to a collection anode, generate a total uncollected induced charge in one or more adjacent anodes to the collection anode that is correlated with the DOI of the event essentially independent of lateral position. Accordingly, the total induced charge caused by an event at the adjacent pixelated anode (or anodes) that is zero or negative can be used to derive or determine the DOI of the particular event. It should further be noted that due to the high absorption of the detector, very few events initiate close to the anodes and, accordingly, such events may have a negligible effect on the use of a negative induced charge to determine the DOI.Accordingly, various embodiments and methods disclosed herein determine a magnitude for a negatively induced uncollected signal (also referred to herein as a secondary signal) and use the determined negative signal magnitude value to determine or derive the DOI.

[0030] As discussed above, in various embodiments, the DOI of an event may be derived from a zero or negative correlation between the DOI of the event and the total uncollected induced charge on the neighboring pixel (or pixels), where the correlation between the DOI and the total uncollected induced charge is substantially independent of lateral position, so that lateral position may be disregarded in deriving the DOI. However, it should be noted that, for example, different photons may have different energies, which may produce a different value for the total uncollected induced charge. Accordingly, in various embodiments, a detector system may be calibrated to account for different photon energies, for example, to normalize the uncollected induced charge value to photon energy.Such a calibration process can be performed to provide calibration information used to determine the DOI. The calibration information can be in the form of, for example, a lookup table or, for example, a formula or mathematical expression based on a curve fit.

[0031] Fig. Figure 10 shows a calibration system 92 according to one embodiment. The illustrated calibration system 92 is used to calibrate a detector 93 having a sidewall 94 extending between an anode surface 95 and a cathode surface 96. The calibration system 92 includes a radiation source 97 and a pinhole collimator 98. The pinhole collimator 98 defines a scanning aperture that can be moved along the Z-direction, as shown in Fig. 10 to irradiate the sidewall 94 of the detector 93 at different DOIs (different Z coordinates). In this way, events with known DOIs and known photon energies are generated with different lateral positions, where the lateral positions depend on the absorption statistics of the irradiation across the sidewall. By measuring resulting induced negative charges for different DOIs, the negative values ​​of the total induced charge for uncollected neighboring signals can be used to generate a lookup table or other relationship to derive the DOI from the induced uncollected charge.

[0032] It should also be noted that since the negative value of the induced charge also depends on the energy of the absorbed photon, the calibration can also take photon energy into account. For example, the DOI can be calibrated based on a ratio between a negative value of the induced non-collected signal and the amplitude of the primary or collected signal. Such a ratio can be expressed in various embodiments as follows: DOI∝V[negative value of the induced charges]V[amplitude of the primary signal]

[0033] Since the negative value of the induced signal is independent (or, as explained herein, substantially or largely independent) of the lateral position (or X, Y coordinates), all adjacent or neighboring pixels generate similar negative signals. Accordingly, the signal-to-noise ratio can be improved by summing the negative signal from a number of adjacent or neighboring pixels. Such a ratio can be expressed in various embodiments as: DOI∝∑i=1i=NV[negative value of the induced charges]iV[amplitude of the primary signal]

[0034] Note that in various embodiments, the negative induced charge or a signal from a neighboring pixel and the primary signal are measured after pulse shapers configured to shape the received or detected signals. In various embodiments, both signals have a generally step-like shape and generally similar peak and shaping times. Accordingly, the relationship between the signals may be approximately equal either after the pulse shapers or immediately after the amplifiers from which the shapers receive the signals.

[0035] Fig. 11 provides a schematic view of a radiation detector assembly 100 according to various embodiments. As shown in Fig. 11, the radiation detector assembly 100 includes a semiconductor detector 110 and a processing unit 120. The semiconductor detector 110 has a surface 112 on which a plurality of pixelated anodes 114 are disposed. In the illustrated embodiment, a cathode 142 is disposed on a surface opposite the surface 112 on which the pixelated anodes 114 are disposed. For example, a single cathode may be disposed on one surface with the pixelated anodes disposed on an opposite surface. When radiation (e.g., one or more photons) impinges on the pixelated anodes 114, the semiconductor detector 110 generally generates electrical signals corresponding to the radiation penetrating across the surface of the cathode 142 and being absorbed in the volume of the detector 110 below the surface 112.In the illustrated embodiment, the pixelated anodes 114 are shown in a 5 × 5 arrangement for a total of 25 pixelated anodes 114. However, it should be noted that other numbers or arrangements of pixelated anodes may be used in various embodiments. For example, each pixelated anode 114 may have a surface area of ​​2.5 mm2; however, other sizes and / or shapes may be used in various embodiments.

[0036] The semiconductor detector 110 can be constructed in various embodiments using various materials, such as semiconductor materials, including cadmium zinc telluride (CdZnTe), often referred to as CZT, cadmium telluride (CdTe), and silicon (Si), among others. The detector 110 can be configured, for example, for use with nuclear medicine (NM) imaging systems, positron emission tomography (PET) imaging systems, and / or single-photon emission computed tomography (SPECT) imaging systems.

[0037] In the illustrated embodiment, each pixelated anode 114 generates different signals depending on the lateral position (e.g., in the X, Y directions) at which a photon is absorbed in the volume of detector 110 below surface 112. For example, each pixelated anode 114 generates a primary or collected signal in response to the absorption of a photon in the volume of detector 110 below the particular pixelated anode 114 through which the photon enters the detector volume. The volumes of detector 110 below the pixelated anodes 114 are defined as voxels (not shown). For each pixelated anode 114, detector 110 has the corresponding voxel.The absorption of a photon by a particular voxel corresponding to a particular pixelated anode 114a also results in an induced charge that can be detected by pixels 114b adjacent to or surrounding the particular pixelated anode 114a that receives the photon. The charge detected by a neighboring or surrounding pixel may be referred to herein as uncollected charge and may result in an uncollected or secondary signal. A primary signal may include information related to photon energy (e.g., a distribution across a range of energy levels) as well as positional information corresponding to the particular pixelated anode 114 at which a photon penetrates across the surface of the cathode 142 and is absorbed in the corresponding voxel.

[0038] For example, in Fig. 1, a photon 116 is shown impinging on the pixelated anode 114a to be absorbed in the corresponding voxel. Accordingly, the pixelated anode 114a generates a primary signal in response to receiving the photon 116. As also shown in Fig. As can be seen in Figure 1, the pixelated anodes 114b are adjacent to the pixelated anode 114a. The pixelated anode 114a has eight neighboring pixelated anodes 114b. When the pixelated anode 114a is struck by the photon 116, a charge is induced in and collected by the pixelated anode 114a to generate the primary signal. One or more of the neighboring pixelated anodes 114b generate a secondary signal in response to the induced charge generated in and collected by the pixelated anode 114a, thereby generating the primary signal. The secondary signal has an amplitude smaller than the primary signal. For any given photon, the corresponding primary signal (from the affected pixel) and the secondary signals (from one or more pixels adjacent to the affected pixel) can be used to locate the reception point of a photon at a specific position within the pixel (e.g.to identify specific subpixel positions within the pixel).

[0039] As in Fig. As can be seen in Figure 11, the sidewalls 140 extend along a depth 150 in the Z direction between the surface 112 and the cathode 142. The position along the Z direction along the depth 150 of absorption where the photon 116 is absorbed is the DOI for the corresponding event. As explained herein, the negatively induced uncollected charge on one or more adjacent pixelated anodes 114b is used in the illustrated embodiment to determine the DOI for the event corresponding to the impact of the photon 116.

[0040] Each pixelated anode 114 may be associated with one or more electronic channels configured to provide the primary and secondary signals in cooperation with the pixelated anodes to one or more aspects of the processing unit 120. In some embodiments, each electronic channel may be located entirely or partially on the detector 110. Alternatively or additionally, each electronic channel may be located entirely or partially external to the detector 110, for example, as part of the processing unit 120, which may be or include an application-specific integration circuit (ASIC). The electronic channels may be configured to provide the primary and secondary signals to one or more aspects of the processing unit 120 while discarding other signals. For example, in some embodiments, each electronic channel includes a threshold discriminator.The threshold discriminator can allow the transmission of signals that exceed a threshold while preventing or restricting the transmission of signals that do not exceed a threshold. Generally, the threshold level is set low enough to reliably detect the secondary signals while still being set high enough to exclude signals of lower magnitude, for example, due to noise. Note that because the secondary signals may be relatively low in magnitude, the electronics used are preferably low-noise electronics to reduce or eliminate noise that is not eliminated by the threshold level. In some embodiments, each electronic channel includes a peak-and-hold unit for storing electrical signal energy and may also include a readout mechanism.For example, the electronic channel may include a request acknowledgement mechanism that allows the peak-and-hold energy and pixel position to be read individually for each channel. Furthermore, in some embodiments, processing unit 120 or another processor may control the signal threshold level and the request acknowledgement mechanism.

[0041] In the illustrated embodiment, processing unit 120 is operatively coupled to pixelated anodes 114 and is configured to detect primary signals (for collected charges) and secondary signals (for uncollected charges). For example, in various embodiments, processing unit 120 detects a primary signal from one of the anodes in response to the anode receiving a photon. For example, a primary signal may be detected from pixelated anode 114a in response to the photon being received 116. Processing unit 120 also detects at least one secondary signal from at least one neighboring pixel (e.g., at least one neighboring anode 114b) in response to an induced charge caused by the photon being received. For example, a secondary signal may be detected from one or more of the neighboring pixels 114b in response to the photon being received 116.It should be noted that the secondary signal (or signals) and the primary signal generated in response to the receipt of the photon 116 may be associated with each other based on the timing and position of detection of the corresponding charges.

[0042] The illustrated processing unit 120 is further configured to determine a depth of interaction (DOI) in the semiconductor detector 110 for receiving the photon using (e.g., based on) the at least one secondary signal. For example, a DOI may be determined along the depth 150 at which the photon 116 is absorbed. In some embodiments, a total negative induced uncollected charge for the at least one secondary signal may be determined and used to determine the DOI, as explained herein. In various embodiments, a lookup table or other correlation may be used to determine the DOI from a determined total negative induced uncollected charge for the at least one secondary signal.It should be noted that in various embodiments, the processing unit 120 determines the DOI using only signals generated based on information from the pixelated anodes 114 and without using information from the cathode 142. Accordingly, the design and / or arrangement of the detector array 100 may avoid or remove any hardware or electrical connections that would otherwise be necessary to acquire signals from the cathode 142 for use in determining the DOI. Additionally, the acquisition and / or processing complexity or requirements may be further reduced by using the same information (primary and secondary signals) as discussed herein to determine both the DOI and the subpixel position.

[0043] The determined DOI can be used to improve image quality. For example, the determined DOI can be used to correct or adjust acquired image information. In some embodiments, the processing unit 120 is configured to adjust an energy level for an event corresponding to the reception of a photon by an anode based on the DOI. Note that the charge loss for a detected event depends on the distance of absorption for the event from the anode. Accordingly, the DOI can be used for a number of events to adjust the charge loss to make the energy levels for the events more uniform and / or closer to a photopeak, to perform accurate event identification and counting.

[0044] Alternatively or additionally, processing unit 120 may be configured to reconstruct an image using the DOI. For example, the DOI of a number of events may be used directly by a reconstruction technique to utilize the 3D positioning of events in the detector for reconstruction. As another example, the DOI may be used indirectly by a reconstruction technique by using the DOI to correct the energy levels and then using the corrected energy levels for image reconstruction.

[0045] As explained herein, calibration information is used in various embodiments. The processing unit 120 is configured in various embodiments to use calibration information (see, e.g., Fig. 10 and the related explanations) to determine the DOI. The calibration may be in the form of a lookup table or other relationship that is stored or otherwise associated with or accessible to the processing unit 120 (e.g., stored in memory 130). In some embodiments, the processing unit 120 is configured to determine the DOI using a calibration based on a ratio between a negative value of a single secondary signal and an amplitude of the primary signal. (See Fig. 10 and the related explanations.) As another example, in some embodiments, the processing unit 120 is configured to determine the DOI using a calibration based on a ratio between a sum or combination of negative values ​​for a plurality of secondary signals (e.g., signals from a number of neighboring pixels 114b) and an amplitude of the primary signal. (See Fig. 10 and the related explanations.) In various embodiments, the processing unit 120 may also be configured to determine a subpixel position (e.g., a lateral position) for events using the primary signal and at least one secondary signal in addition to determining the DOI. The subpixel position and the DOI may be determined using the same primary signal and at least one secondary signal, thereby providing efficient determination of both. For example, the illustrated example processing unit 120 is configured to define subpixels for each pixelated anode. Note that in the illustrated embodiment, the subpixels (shown as separated by dashed lines) are not physically separate, but instead are virtual entities defined by the processing unit 120.In general, using an increasing number of subpixels per pixel improves resolution while also increasing computational or processing requirements. The particular number of subpixels defined or employed in a given application can be selected based on a balance between improved resolution and increased processing requirements. In various embodiments, the use of virtual subpixels, as explained herein, provides improved resolution while avoiding or reducing costs associated with an increasingly larger number of progressively smaller pixelated anodes.

[0046] In the illustrated embodiment, the pixelated anode 114a is divided into four subpixels, namely subpixel 150, subpixel 152, subpixel 154 and subpixel 156, as shown. While in Fig. 11 subpixels are shown only for the pixelated anode 114a for reasons of clarity and simplicity of illustration, it should be noted that in the illustrated embodiment, the processing unit 120 also defines corresponding subpixels for each of the remaining pixelated anodes 114. As shown in Fig. 11, the photon 116 strikes a part of the pixelated anode 114a defined by the virtual subpixel 150.

[0047] In the illustrated embodiment, processing unit 120 acquires the primary signal for a given sensing event (e.g., photon impact) from pixelated anode 114a, along with timing information (e.g., timestamp information) corresponding to a generation time of the primary signal and position information identifying pixelated anode 114a as the pixelated anode corresponding to the primary signal. For example, a sensing event such as a photon impacting pixelated anode 114 may result in a number of counts occurring across a range or spectrum of energies, with the primary signal containing information describing the distribution of counts across the range or spectrum of energies.Processing unit 120 also acquires one or more secondary signals for the detection event from pixelated anodes 114b, along with timestamp information and position information for the secondary signal(s). Processing unit 120 then determines the position for the given detection event, identifies pixelated anode 114a as the affected pixelated anode 114a, and then determines which of subpixels 150, 152, 154, 156 defines the position of impact for the detection event. Using conventional techniques, the position of the sub-pixels 150, 152, 154, 156 may be derived based on the position (e.g., of the associated pixelated anode) and the relationships between the strengths of the primary signal in the associated pixelated anode 114a and the secondary signal(s) in the adjacent pixelated anodes 114b for the detection event.Processing unit 120 may use timestamp information and position information to correlate the primary signal and secondary signals generated in response to the given detection event and to distinguish the primary signal and secondary signals for the given detection event from signals for other detection events occurring during a detection or detection period using the timestamp and position information. Accordingly, the use of timestamp information helps distinguish between the primary signal and its corresponding secondary signals from a random coincidence that may occur between primary signals of neighboring pixels, because the timestamps for the primary signal and its corresponding secondary signals are correlated with specific detection events.

[0048] Further explanations regarding virtual subpixels and the use of virtual subpixels, as well as the use of collected and uncollected signals, can be found in U.S. patent application serial number 14 / 724,022, entitled "Systems and Method for Charge-Sharing Identification and Correction Using a Single Pixel," filed May 28, 2015, published as US 9,482,764 B1 ("the '022 application"); U.S. patent application serial number 15 / 280,640, entitled "Systems and Methods for Sub-Pixel Location Determination," filed September 29, 2016, published as US 2017 / 0016998 A1 ("the '640 application"); and US patent application serial number 14 / 627,436 entitled “Systems and Methods for Improving Energy Resolution by Sub-Pixel Energy Calibration”, filed on February 20, 2015, published as US 2016 / 0 245 934 A1 (“the ’436 application”).The contents of each of the applications 022, 640 and 436 are hereby incorporated by reference in their entirety.

[0049] In various embodiments, the processing unit 120 includes processing circuitry configured to perform one or more tasks, functions, or steps discussed herein. It should be noted that "processing unit" as used herein is not necessarily limited to a single processor or computer. For example, the processing unit 120 may include multiple processors, ASICs, FPGAs, and / or computers that may be integrated into a common housing or unit, or that may be distributed among different units or housings. It should be noted that operations performed by the processing unit 120 (e.g.,Operations corresponding to the process flows or methods or aspects thereof discussed herein) may be sufficiently complex that the operations may not be capable of being performed by a human within a reasonable period of time. For example, determining values ​​of collected and uncollected charges and / or determining DOIs and / or subpixel positions based on the collected and / or uncollected charges within the time constraints associated with such signals may rely on or utilize calculations that could not be performed by a human within a reasonable period of time.

[0050] The illustrated processing unit 120 includes a memory 130. The memory 130 may include one or more computer-readable storage media. The memory 130 may store, for example, imaging information describing subpixel positions, acquired image data corresponding to the generated images, results of intermediate processing steps, calibration parameters or calibration information (e.g., a lookup table correlating negatively induced charge with DOI), or the like. Furthermore, the process flows and / or flowcharts discussed herein (or aspects thereof) may represent one or more sets of instructions stored in the memory 130 for directing the operations of the radiation detection assembly 100.

[0051] Fig. 12 provides a flowchart of a method 200 (e.g., for determining DOI) according to various embodiments. The method 200 may, for example, employ or be performed by structures or aspects of various embodiments (e.g., systems and / or methods and / or process flows) discussed herein. In various embodiments, certain steps may be omitted or added, certain steps may be combined, certain steps may be performed concurrently, certain steps may be split into multiple steps, certain steps may be performed in a different order, or certain steps or series of steps may be repeated iteratively. In various embodiments, portions, aspects, and / or variations of the method 200 may be used as one or more algorithms to implement hardware (e.g.,instruct one or more aspects of processing unit 120) to perform one or more operations described herein.

[0052] At 202, primary signals and secondary signals corresponding to detection events (e.g., events corresponding to the reception of photons) are acquired. The primary and secondary signals are generated in response to the reception of photons by a semiconductor detector and received by pixelated anodes (e.g., anodes of a semiconductor device of an imaging system such as array 100). For example, a patient who has been administered at least one radiopharmaceutical may be positioned within a field of view of one or more detectors, and radiation (e.g., photons) emitted by the patient may impinge on the pixelated anodes deposited on the receiving surfaces of the one or more detectors, resulting in detection events (e.g., photon strikes).For a given photon impact in the illustrated exemplary embodiment, a primary signal (responsive to a collected charge) is generated by the affected pixelated anode (or collecting anode) and one or more secondary signals (responsive to a non-collected charge) are generated by pixelated anodes adjacent to the affected pixelated anode (or non-collecting anode).

[0053] At 204, a depth of interaction (DOI) in the semiconductor device is determined for the sensing events, resulting in the primary and secondary signals acquired at 202. In various embodiments, the DOI for a particular event is determined using at least one secondary signal for that particular event. For example, as explained herein, in various embodiments, the DOI is determined based on a total negatively induced uncollected charge value from one or more neighboring or non-collecting pixels (e.g., at least one neighboring pixelated anode). Note that in various embodiments, the DOI is determined without using any information (e.g., sensed charge or corresponding signals) from a cathode of the detector array.

[0054] In various embodiments, the total negative non-collecting induced charge may be adjusted or corrected to account for variations in semiconductor construction and / or photon energies. For example, in the illustrated embodiment, at 206, calibration information is used to determine the DOI. As discussed herein, in some embodiments, the DOI may be determined using a calibration based on a ratio between a negative value of a single secondary signal and an amplitude of the primary signal, and in some embodiments, the DOI may be determined using a calibration based on a ratio between a sum or combination of negative values ​​for multiple secondary signals and an amplitude of the primary signal. (See Fig. 10 and the associated explanations.)

[0055] At 208, a subpixel position is determined using the primary signal and the at least one secondary signal. A corresponding subpixel position can be determined for each event. Note that the same information (primary and secondary signals) used to determine DOIs for events can also be used to determine subpixel positions for those events.

[0056] At 210, an energy level for an event is adjusted based on the DOI. For example, since the sensed energy may vary based on the DOI, the DOI for each sensed event may be used to adjust the corresponding energy levels based on the corresponding DOIs to make the energy levels for a group of events more consistent and / or closer to a target or other predetermined energy level.

[0057] At 212, an image is reconstructed using the DOI. For example, corrected energy levels from 210 can be used in the reconstruction of an image. As another example, the DOIs for events can be used to determine 3D position information of those events within a detector, with the 3D position information being used to reconstruct an image.

[0058] As discussed herein, a radiation detector system (e.g., a system configured to determine DOI using secondary signals corresponding to uncollected induced charges) may be calibrated. Fig. 13 provides a flowchart of a method 300 (e.g., for providing and calibrating a radiation detector assembly) according to various embodiments. The method 300 may, for example, employ or be performed by structures or aspects of various embodiments (e.g., systems and / or methods and / or process flows) discussed herein. In various embodiments, certain steps may be omitted or added, certain steps may be combined, certain steps may be performed concurrently, certain steps may be split into multiple steps, certain steps may be performed in a different order, or certain steps or series of steps may be repeated iteratively. In various embodiments, portions, aspects, and / or variations of the method 300 may be used as one or more algorithms to modify hardware (e.g.,instruct one or more aspects of processing unit 120) to perform one or more operations described herein.

[0059] At 302, a semiconductor detector (e.g., semiconductor detector 110 of radiation imaging assembly 100) is provided. The semiconductor detector of the illustrated example includes a surface with a plurality of pixelated anodes disposed on the surface. Each pixelated anode is configured to generate a primary signal in response to receipt of a photon by the pixelated anode and to generate at least one secondary signal in response to an induced charge caused by receipt of a photon by at least one adjacent anode. At 304, the pixelated anodes are operably coupled to at least one processor (e.g., processing unit 120).

[0060] At 306, a calibrated radiation source (e.g., with a known photon energy) is provided at different depths along a sidewall of the semiconductor detector. In response to receiving the calibrated radiation supply, the pixelated anodes generate primary and secondary signals. For example, the calibrated radiation supply may be guided through a pinhole collimator to the sidewall of the semiconductor detector. The position of a given pinhole (e.g., in a Z-direction) through which radiation is guided may be used to determine the DOI at which the corresponding radiation is guided by the collimator and received by the semiconductor detector. At 308, the primary and secondary signals from the pixelated anodes are detected by the at least one processor.

[0061] At 310, corresponding negative values ​​of the total induced charges are determined for each of the different depths at which the radiation was applied. At 312, calibration information (e.g., a lookup table or other correlation relationship between DOIs and negatively induced uncollected charge values) is determined.

[0062] Fig. 14 is a schematic representation of an NM imaging system 1000 having a plurality of imaging detector head assemblies mounted on a gantry (which may be mounted, for example, in rows, in an iris shape, or in other configurations, such as a configuration in which the movable detector supports 1016 are radially aligned with the patient body 1010). In particular, a plurality of image detectors 1002 are attached to a gantry 1004. In the illustrated embodiment, the image detectors 1002 are configured as two separate detector arrays 1006 and 1008 coupled to the gantry 1004 above and below a subject 1010 (e.g., a patient), as shown in Fig. 14. The detector arrays 1006 and 1008 may be coupled directly to the gantry 1004 or may be coupled to the gantry 1004 via support elements 1012 to enable movement of the entire assemblies 1006 and / or 1008 relative to the gantry 1004 (e.g., transverse translational movement in the left or right direction as indicated by arrow T in the Fig. 14). Additionally, each of the image detectors 1002 includes a detector unit 1014, at least some of which are mounted on a movable detector support 1016 (e.g., a support arm or actuator that can be driven by a motor to effect its movement) that extends from the gantry 1004. In some embodiments, the detector supports 1016 enable movement of the detector units 1014 toward and away from the subject 1010, such as linearly. Thus, in the illustrated embodiment, the detector arrays 1006 and 1008 are mounted in parallel above and below the subject 1010 and enable linear movement of the detector units 1014 in a direction (indicated by arrow L) shown as perpendicular to the support member 1012 (which are coupled generally horizontally on the gantry 1004). However, other configurations and orientations are possible, as described herein.It should be noted that the movable detector support 1016 may be any support that allows movement of the detector units 1014 relative to the support member 1012 and / or gantry 1004, which in various embodiments allows the detector units 1014 to move linearly toward and away from the support member 1012.

[0063] Each of the image detectors 1002, in various embodiments, is smaller than a conventional whole-body or general-purpose image detector. A conventional image detector may be large enough to image most or all of the width of a patient's body at once and may have a diameter or larger dimension of approximately 50 cm or more. In contrast, each of the image detectors 1002 may include one or more detector units 1014 coupled to a respective detector carrier 1016, having dimensions ranging from, for example, 4 cm to 20 cm, and may be composed of cadmium zinc telluride (CZT) tiles or modules. For example, each of the detector units 1014 may have a size of 8 x 8 cm and be composed of a plurality of CZT pixel modules (not shown). For example, each module may be 4 x 4 cm and have 16 x 16 = 256 pixels.In some embodiments, each detector unit 1014 includes a plurality of modules, such as a 1 × 7 module array. However, different configurations and array sizes are contemplated, including, for example, detector units 1014 with multiple rows of modules.

[0064] It is understood that the image detectors 1002 may have different sizes and / or shapes relative to one another, such as square, rectangular, circular, or other shapes. An actual field of view (FOV) of each of the image detectors 1002 may be directly proportional to the size and shape of the respective image detector.

[0065] The gantry 1004 may be provided with an opening 1018 (e.g., opening or bore), as shown. A patient table 1020, such as a patient couch, is configured with a support mechanism (not shown) to support and support the subject 1010 in one or more of a plurality of viewing positions within the aperture 1018 and relative to the image detectors 1002. Alternatively, the gantry 1004 may include a plurality of gantry segments (not shown), each of which can independently move a support member 1012 or one or more of the image detectors 1002.

[0066] The gantry 1004 may also be configured in other shapes, such as "C," "H," and "L," and may be rotatable around the test subject 1010. For example, the gantry 1004 may be configured as a closed ring or circle, or as an open arc, which allows easy access to the test subject 1010 during imaging and facilitates loading and unloading of the test subject 1010 and reduces claustrophobia in some test subjects 1010.

[0067] Additional image detectors (not shown) may be positioned to form rows of detector arrays or an arc or ring around the subject 1010. By positioning multiple image detectors 1002 at multiple positions relative to the subject 1010, such as along an imaging axis (e.g., head-to-toe direction of the subject 1010), image data specific to a larger FOV may be acquired more quickly.

[0068] Each of the image detectors 1002 has a radiation detection area directed toward the subject 1010 or a region of interest within the subject.

[0069] In various embodiments, multi-bore collimators can be designed to register with pixels of detector units 1014, which in one embodiment are CZT detectors. However, other materials can also be used. Registered collimation can improve spatial resolution by causing photons passing through a bore to be collected primarily by one pixel. Additionally, registered collimation can improve the sensitivity and energy response of pixelated detectors, since the detector region near the edges of a pixel or between two adjacent pixels may exhibit reduced sensitivity or reduced energy resolution or other performance degradation.When collimator septa are placed directly above the edges of pixels, the probability that a photon will land at those positions with reduced power is reduced without reducing the overall probability that a photon will pass through the collimator.

[0070] A control unit 1030 can control the movement and positioning of the patient table 1020, the image detectors 1002 (which can be configured as one or more arms), the gantry 1004, and / or the collimators 1022 (which, in various embodiments, move with the image detectors 1002 to which they are coupled). A range of movement before or during an acquisition, or between different image acquisitions, is set to maintain the actual FOV of each of the image detectors 1002, for example, "aiming" at a specific area or region of the subject 1010 or along the entire subject 1010. The movement can be a combined or complex movement in multiple directions simultaneously, concurrently, or sequentially, as described in more detail herein.

[0071] The control unit 1030 may include a gantry motor controller 1032, a stage controller 1034, a detector controller 1036, a pan controller 1038, and a collimator controller 1040. The controllers 1030, 1032, 1034, 1036, 1038, 1040 may be commanded automatically by a processing unit 1050, manually controlled by an operator, or a combination thereof. The gantry motor controller 1032 may move the image detectors 1002 with respect to the subject 1010, for example, individually, in segments or subsets, or simultaneously in a fixed relationship to one another. For example, in some embodiments, the gantry controller 1032 may cause the image detectors 1002 and / or the support members 1012 to move relative to or rotate about the subject 1010, which may include movement of less than or up to 180 degrees (or more).

[0072] The table controller 1034 can move the patient table 1020 to position the test subject 1010 relative to the image detectors 1002. The patient table 1020 can be moved, for example, in up-down, in-out, and right-left directions. The detector controller 1036 can control the movement of each of the image detectors 1002 to move together as a group or individually, as described in more detail herein. The detector controller 1036 can also, in some embodiments, control the movement of the image detectors 1002 to move them closer to and farther from a surface of the test subject 1010, for example, by controlling the translational movement of the detector supports 1016 linearly toward or away from the test subject 1010 (e.g., a sliding or telescoping movement). Optionally, the detector controller 1036 may control the movement of the detector carriers 1016 to enable movement of the detector array 1006 or 1008.For example, the detector controller 1036 controls the lateral movement of the detector carriers 1016, represented by the arrow T (and shown as left and right, as in . Fig. 14). In various embodiments, the detector controller 1036 controls the detector supports 1016 or the support elements 1012 to move in different lateral directions. The detector controller 1036 controls the pivoting movement of the detectors 1002 along with their collimators 1022.

[0073] The pan control 1038 controls a panning or rotational movement of the detector units 1014 at the ends of the detector supports 1016 and / or a panning or rotational movement of the detector support 1016. For example, one or more of the detector units 1014 or detector supports 1016 can be rotated about at least one axis to view the subject 1010 from multiple angular orientations, for example, to acquire 3D image data in a 3D SPECT or 3D imaging operation mode. The collimator control 1040 can adjust a position of an adjustable collimator, such as a collimator with adjustable stripes (or wings) or adjustable pinholes.

[0074] It should be noted that the movement of one or more image detectors 1002 may be in directions other than strictly axial or radial, and in various embodiments, movements in multiple directions of movement may be used. Therefore, the term "motion controller" may be used to provide a collective designation for all motion controllers. It should be noted that the various controllers may be combined; for example, the detector controller 1036 and the pan controller 1038 may be combined to provide the various movements described herein.

[0075] Before acquiring an image of the subject 1010 or a portion of the subject 1010, the image detectors 1002, the gantry 1004, the patient table 1020, and / or the collimators 1022 may be adjusted, such as to first or initial imaging positions, as well as subsequent imaging positions. The image detectors 1002 may each be positioned to image a portion of the subject 1010. Alternatively, for example, in the case of a smaller subject 1010, one or more of the image detectors 1002 may not be used to acquire data, such as the image detectors 1002 at the ends of the detector arrays 1006 and 1008 located as in Fig. 14, in a position retracted from the test subject 1010. Positioning may be performed manually by the operator and / or automatically, which may include, for example, using image information such as other images acquired prior to the current acquisition, for example, by another imaging modality such as x-ray computed tomography (CT), MRI, x-ray, PET, or ultrasound. In some embodiments, the additional information for positioning, such as the other images, may be acquired by the same system, such as in a hybrid system (e.g., a SPECT / CT system). Additionally, the detector units 1014 may be configured to acquire non-NM data such as x-ray CT data.In some embodiments, a multi-modality imaging system may be provided to enable, for example, the performance of NM or SPECT imaging as well as X-ray CT imaging, which may include a dual-modality or gantry design, as described in more detail herein.

[0076] After the image detectors 1002, the gantry 1004, the patient table 1020, and / or the collimators 1022 are positioned, one or more images, such as three-dimensional (3D) SPECT images, are acquired using one or more of the image detectors 1002, which may include the use of a combined motion that reduces or minimizes the distance between the detector units 1014. The image data acquired by each image detector 1002 may be combined and reconstructed into a composite image or 3D images in various embodiments.

[0077] In one embodiment, at least one of the detector arrays 1006 and / or 1008, the gantry 1004, the patient table 1020, and / or the collimators 1022 are moved after initial positioning, which includes a single movement of one or more of the detector units 1014 (e.g., combined lateral and sweeping movement) along with the sweeping movement of the detectors 1002. For example, at least one of the detector arrays 1006 and / or 1008 may be moved laterally while being swept. Thus, in various embodiments, a plurality of small detectors, such as the detector units 1014, may be used for 3D imaging, for example, when the detector units 1014 are moved or swept in combination with other movements.

[0078] In various embodiments, a data acquisition system (DAS) 1060 receives electrical signal data generated by the image detectors 1002 and converts this data into digital signals for subsequent processing. However, in various embodiments, digital signals are generated by the image detectors 1002. An image reconstruction device 1062 (which may be a processing device or a computer) and a data storage device 1064 may be provided in addition to the processing unit 1050. It should be noted that one or more functions related to data acquisition, motion control, data processing, and / or image reconstruction may be performed by hardware, software, and / or shared processing resources that may be located within, near, or remote from the imaging system 1000.Additionally, a user input device 1066 may be provided to receive user inputs (e.g., control commands), as well as a display 1068 for displaying images. DAS 1060 receives the acquired images from detectors 1002 along with the corresponding lateral, vertical, rotational, and panning coordinates of gantry 1004, support elements 1012, detector units 1014, detector supports 1016, and detectors 1002 for accurately reconstructing an image containing 3D images and their slices.

[0079] It should be noted that the design of Fig. 14 can be understood as a linear array of detector heads (e.g., using detector units arranged in a row and extending parallel to each other). In other embodiments, a radial design can be used. For example, radial designs can offer additional advantages in terms of efficiently imaging smaller objects such as limbs, heads, or infants. Fig. 15 provides a schematic view of a nuclear medicine (NM) multi-head imaging system 1100 according to various embodiments.

[0080] In general, the imaging system 1100 is configured to acquire image information (e.g., photon counts) from an object to be imaged (e.g., a human patient) to whom a radiopharmaceutical has been administered. The illustrated imaging system 1100 includes a gantry 1110 having a bore 1112, a plurality of radiation detector head assemblies 1115, and a processing unit 1120.

[0081] The gantry 1110 defines the bore 1112. The bore 1112 is configured to receive an object to be imaged (e.g., a human patient or a portion thereof). As shown in Fig.15, a plurality of radiation detector head assemblies 1115 are mounted on the gantry 1110. In the illustrated embodiment, each radiation detector head assembly 1115 includes an arm 1114 and a head 1116. The arm 1114 is configured to move the head 1116 radially toward and / or away from a center of the bore 1112 (and / or in other directions), and the head 1116 includes at least one detector, with the head 1116 being disposed at a radially inner end of the arm 1114 and pivotably configured to provide a range of positions from which image information is acquired.

[0082] The detector of head 1116 may, for example, be a semiconductor detector. For example, various embodiments of a semiconductor detector may be constructed using various materials, such as semiconductor materials, including cadmium zinc telluride (CdZnTe), often referred to as CZT, cadmium telluride (CdTe), and silicon (Si), among others. The detector may, for example, be configured for use with nuclear medicine (NM) imaging systems, positron emission tomography (PET) imaging systems, and / or single-photon emission computed tomography (SPECT) imaging systems.

[0083] In various embodiments, the detector may comprise an array of pixelated anodes and may generate different signals depending on the position at which a photon is absorbed in the volume of the detector below a surface. The volumes of the detector below the pixelated anodes are defined as voxels. For each pixelated anode, the detector has a corresponding voxel. The absorption of photons by specific voxels corresponding to specific pixelated anodes results in charges that can be counted. The counts can be correlated to specific positions and used to reconstruct an image.

[0084] In various embodiments, each detector head assembly 1115 may define a corresponding view aligned with the center of the bore 1112. Each detector head assembly 1115 in the illustrated embodiment is configured to acquire image information over a scan area corresponding to the view of the given detector unit. Additional details regarding examples of systems with detector units arranged radially around a bore can be found in U.S. patent application Ser. No. 14 / 788,180, filed June 30, 2015, published as US 2017 / 0 000 448 A1, entitled "Systems and Methods For Dynamic Scanning With Multi-Head Camera," the contents of which are hereby incorporated by reference in their entirety.

[0085] Processing unit 1120 includes memory 1122. Imaging system 1100 is illustrated as including a single processing unit 1120; however, the block for processing unit 1120 may be understood to represent one or more processors, which may be distributed or remote from each other. The illustrated processing unit 1120 includes processing circuitry configured to perform one or more tasks, functions, or steps discussed herein. It should be noted that "processing unit" as used herein is not necessarily limited to a single processor or computer. For example, processing unit 1120 may include multiple processors and / or computers, which may be integrated into a common housing or unit, or which may be distributed among different units or housings.

[0086] Generally, various aspects (e.g., programmed modules) of processing unit 1120 operate individually or cooperatively with other aspects to perform one or more aspects of the methods, steps, or processes discussed herein. In the illustrated embodiment, memory 1122 comprises a tangible, non-transitory computer-readable medium storing instructions for performing one or more aspects of the methods, steps, or processes discussed herein.

[0087] It should be noted that the various embodiments may be implemented in hardware, software, or a combination thereof. The various embodiments and / or components, such as the modules or components and controllers therein, may also be implemented as part of one or more computers or processors. The computer or processor may include a computing device, an input device, a display unit, and an interface, such as for accessing the Internet. The computer or processor may include a microprocessor. The microprocessor may be connected to a communications bus. The computer or processor may also include memory. The memory may include random access memory (RAM) and read-only memory (ROM).The computer or processor may further include a storage device, which may be a hard disk drive or a removable storage drive, such as a solid-state drive, an optical disk drive, and the like. The storage device may also be another similar means for loading computer programs or other instructions into the computer or processor.

[0088] As used herein, the term "computer" or "module" can encompass any processor-based or microprocessor-based system, including systems using microcontrollers, reduced instruction set computers (RISCs), ASICs, logic circuits, and any other circuitry or processor capable of performing the functions described herein. The above examples are exemplary only and are therefore not intended to limit the definition and / or meaning of the term "computer" in any way.

[0089] The computer or processor executes a set of instructions stored in one or more memory elements to process input data. The memory elements can also store data or other information as desired or needed. The memory element can be in the form of an information source or a physical storage element within a processing machine.

[0090] The set of instructions may include various instructions that instruct the computer or processor, as a processing engine, to perform specific operations such as the methods and processes of the various embodiments. The set of instructions may be in the form of a software program. The software may exist in various forms, such as system software or application software, and may be embodied as a tangible and non-transitory computer-readable medium. Furthermore, the software may be in the form of a collection of separate programs or modules, a program module within a larger program, or as a section of a program module. The software may also include modular programming in the form of object-oriented programming.

[0091] The processing of input data by the processing machine may be in response to operator commands, in response to results of previous processing, or in response to a request from another processing machine.

[0092] As used herein, a structure, constraint, or element "configured to" perform a task or operation is specially structurally designed, constructed, or adapted in a manner appropriate to the task or operation. For the purpose of clarity and avoidance of doubt, an object that can be modified merely to perform the task or operation is not "configured" to perform the task or operation as used herein. Instead, the use of "configured to" as used herein refers to structural adaptations or characteristics and denotes structural requirements of any structure, constraint, or element described as "configured to" perform the task or operation.For example, a processing unit, processor, or computer that is "configured" to perform a task or operation may be understood as being particularly structured to perform the task or operation (e.g., having one or more programs or instructions stored thereon or used in connection therewith that are tailored or intended to perform the task or operation, and / or having an arrangement of processing circuitry tailored or intended to perform the task or operation).For the sake of clarity and avoidance of doubt, a general-purpose computer (which, if appropriately programmed, may be "configured" to perform the task or operation) is not "configured" to perform a task or operation unless it is specifically programmed or structurally modified to perform the task or operation.

[0093] As used herein, the terms "software" and "firmware" are interchangeable and include any computer program stored in memory for execution by a computer, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above memory types are exemplary only and therefore do not limit the types of memory that may be used to store a computer program.

[0094] It should be noted that the above description is intended to be illustrative and not restrictive. For example, the above-described embodiments (and / or aspects thereof) may be used in combination with one another. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the various embodiments without departing from their scope. Although the dimensions and types of materials described herein are intended to define the parameters of the various embodiments, they are in no way limiting and are merely exemplary. Many other embodiments will be apparent to those skilled in the art after reviewing the above description. The scope of the various embodiments should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.In the appended claims, the terms "including" and "in which" are used as the simple equivalents of the respective terms "comprising" and "wherein." Furthermore, in the following claims, the terms "first," "second," and "third," etc., are used merely as labels and are not intended to impose numerical requirements on their objects.

[0095] This written description uses examples to disclose the various embodiments, including the best mode, and to enable those skilled in the art to practice the various embodiments, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the various embodiments is defined by the claims and may include other examples that may occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if the examples have structural elements that do not differ from the literal language of the claims, or if the examples include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

[1] Radiation detector arrangement (100) comprising: a semiconductor detector (110) having a surface (112); a plurality of pixelated anodes (114) disposed on the surface (112), each pixelated anode (114) configured to generate a primary signal in response to receipt of a photon (116) by the pixelated anode (114) and to generate at least one secondary signal in response to an induced charge caused by receipt of a photon (116) by at least one of the surrounding anodes (114); and at least one processor (120) operatively connected to the pixelated anodes (114), the at least one processor (120) being configured to: detecting a primary signal from one of the anodes (114) in response to receipt of a photon (116) by said one of the anodes (114); detecting at least one secondary signal from at least one adjacent pixel from said one of the anodes (114) in response to an induced charge caused by the reception of the photon (116) by said one of the anodes (114); and Determining a depth of interaction (DOI) in the semiconductor detector (110) for the reception of the photon (116) by the one of the anodes (114) using the at least one secondary signal; wherein the semiconductor detector (110) has a depth (D) with a first region (I) and with a second region (II), wherein the second region (II) is arranged above the first region (I) and closer to the pixelated anodes (114), wherein an electric field vector in the first region (I) has a downward component and the electric field vector in the second region (II) has an upward component. [2] The radiation detector assembly (100) of claim 1, wherein the at least one processor (120) is configured to set an energy level for an event corresponding to reception of the photon (116) by the one of the anodes (114) based on the depth of interaction (DOI). [3] The radiation detector assembly (100) of claim 1, wherein the at least one processor (120) is configured to reconstruct an image using the depth of interaction (DOI). [4] The radiation detector array (100) of claim 1, wherein the at least one adjacent pixel comprises at least one adjacent anode (114). [5] The radiation detector assembly (100) of claim 1, wherein the at least one processor (120) is configured to use calibration information to determine the depth of interaction (DOI). [6] The radiation detector assembly (100) of claim 5, wherein the at least one processor (120) is configured to determine the depth of interaction (DOI) using a calibration based on a ratio between a negative value of a single secondary signal and an amplitude of the primary signal. [7] The radiation detector assembly (100) of claim 5, wherein the at least one processor (120) is configured to determine the depth of interaction (DOI) using a calibration based on a ratio between a sum of negative values ​​for a plurality of secondary signals and an amplitude of the primary signal. [8] The radiation detector assembly (100) of claim 1, wherein the at least one processor (120) is configured to determine the depth of interaction (DOI) without using information from a cathode (142) of the radiation detector assembly (100). [9] The radiation detector assembly (100) of claim 1, wherein the at least one processor (120) is configured to determine a subpixel position using the primary signal and the at least one secondary signal. [10] A method (200) for imaging using a semiconductor detector (110) having a surface (112) with a plurality of pixelated anodes (114) arranged thereon, each pixelated anode (114) configured to generate a primary signal in response to receipt of a photon (116) by the pixelated anode (114) and to generate at least one secondary signal in response to an induced charge caused by receipt of a photon (116) by at least one surrounding anode (114), the method comprising: detecting (202) a primary signal from one of the anodes (114) in response to receipt of a photon (116) by said one of the anodes (114); detecting (202) at least one secondary signal from at least one adjacent pixel of one of the anodes (114) in response to an induced charge caused by the reception of the photon (116) by the one of the anodes (114); and Determining (204) a depth of interaction (DOI) in the semiconductor detector (110) for the reception of the photon (116) by one of the anodes (114) using the at least one secondary signal wherein the semiconductor detector (110) has a depth (D) with a first region (I) and with a second region (II), wherein the second region (II) is arranged above the first region (I) and closer to the pixelated anode (114), wherein an electric field vector in the first region (I) has a downward component and the electric field vector in the second region (II) has an upward component. [11] The method (200) of claim 10, further comprising setting an energy level for an event corresponding to the reception of the photon (116) by the one of the anodes (114) based on the depth of interaction (DOI). [12] The method (200) of claim 10, further comprising reconstructing (212) an image using the depth of interaction (DOI). [13] The method (200) of claim 10, wherein the at least one adjacent pixel comprises at least one adjacent anode (114). [14] The method (200) of claim 10, further comprising using (206) calibration information to determine the depth of interaction (DOI). [15] The method (200) of claim 14, further comprising determining the depth of interaction (DOI) using a calibration based on a ratio between a negative value of a single secondary signal and an amplitude of the primary signal.

Images