Quantitative pulse selection for a photon counting computed tomography system

Abstract

One embodiment is a method for counting charge events detected by a pixel in a photon counting computed tomography (PCCT) scanning system comprising a plurality of discriminators, wherein each discriminator is associated with a respective one of a plurality of threshold voltage levels. The method comprises: detecting a signal output from one of the discriminators; if the detected discriminator output signal satisfies a first condition, increasing a quantitative count corresponding to the threshold voltage level associated with the one of the discriminators; and if the detected discriminator output signal satisfies at least one second condition, increasing a qualitative count.

Description

[0001] Cross-references to related applications

[0002] This application claims the entire contents of U.S. Provisional Application No. 63 / 300953, filed January 19, 2022, entitled “Quantitative Pulse Selection for a Photon Counting Computed Tomography System,” which is incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to the field of photon counting computed tomography (PCCT) scanning systems, and more specifically, to quantitative pulse selection techniques for such systems. Attached Figure Description

[0004] To provide a more complete understanding of this disclosure and its features and advantages, the same reference numerals denote the same parts, wherein:

[0005] Figure 1 This is a schematic diagram illustrating the operation of a conventional CT scanning system with features according to certain embodiments described herein;

[0006] Figure 2 This is a schematic block diagram of an example signal processing architecture for a PCCT scanning system, based on features of certain embodiments described herein;

[0007] Figure 3 This illustrates features according to certain embodiments described herein. Figure 2 A graph showing the results of a simulation example of a PCCT scanning system;

[0008] Figure 4A An example of a charging event accumulation featuring certain embodiments described herein is shown;

[0009] Figure 4B An example of charge sharing features according to embodiments described herein is shown.

[0010] Figure 5A This is a flowchart illustrating the operation of a quantitative pulse selection (QPS) technique featuring the characteristics of an embodiment described herein;

[0011] Figure 5B It is a state machine implemented using QPS technology according to the features of the embodiments described herein;

[0012] Figures 6A-6C The diagram shows the count of charging events detected at a pixel of interest (POI) based on features according to embodiments described herein;

[0013] Figures 7A-7DQuantitative and qualitative counting curves of various PCCT counting methods, compared to ground truth, are shown, characteristic of the embodiments described herein;

[0014] Figure 8 The total count curves of QPS techniques with and without Time Exceeds Threshold (ToT) characteristics, compared to ground truth, according to embodiments described herein, are shown.

[0015] Figure 9A and 9B A series of estimates of bone thickness in a simulated dataset based on features of embodiments described herein are shown;

[0016] Figure 10 This is a block diagram of a computer system that can be used to implement all or part of a PCCT scanning system, based on features of certain embodiments described herein. Detailed Implementation

[0017] For the purposes of this disclosure, the phrase "A and / or B" refers to (A), (B), or (A and B). For the purposes of this disclosure, the phrase "A, B, and / or C" refers to (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C). When referring to a measurement range, the term "between" includes the ends of the measurement range. The symbol "A / B / C" as used herein represents (A), (B), and / or (C).

[0018] This specification uses the phrases "in an embodiment" or "in an implementation," which may refer to one or more of the same or different implementations, respectively. Furthermore, the terms "comprising," "including," "having," etc., used with respect to embodiments of this disclosure are synonyms. This disclosure may use perspective-based descriptions, such as "above," "below," "over," and "below"; such descriptions are used to facilitate discussion and are not intended to limit the application of the disclosed embodiments. The drawings are not necessarily drawn to scale. Unless otherwise specified, the use of ordinal adjectives such as "first," "second," and "third" to describe a common object merely indicates that different instances of similar objects are being referenced and does not imply that the objects described in this way must be in a given order in time, space, ranking, or any other way.

[0019] In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which illustrative embodiments that can be practiced are shown. It should be understood that other embodiments may be used, and structural or logical changes may be made without departing from the scope of this disclosure. Therefore, the following detailed description should not be limited thereto.

[0020] The following disclosure describes various illustrative embodiments and examples for implementing the features and functions of this disclosure. While specific components, arrangements, and / or features are described below in conjunction with various exemplary embodiments, these are merely examples for simplifying this disclosure and are not intended to be limiting. It will be appreciated that in the development of any actual embodiment, many implementation-specific decisions must be made to achieve the developer's specific objectives, including compliance with system, business, and / or legal constraints, which may vary from implementation to implementation. Furthermore, it should be recognized that while such development efforts may be complex and time-consuming, this will be a routine task for those skilled in the art who benefit from this disclosure.

[0021] In this specification, reference may be made to the spatial relationships between the various components and the spatial orientation of various aspects of the components shown in the accompanying drawings. However, as those skilled in the art will recognize upon fully reading this disclosure, the devices, components, members, apparatuses, etc., described herein can be positioned in any desired orientation. Therefore, the use of terms such as “above,” “below,” “over,” and “below” to describe the spatial relationships between various components or to describe the spatial orientation of various aspects of these components should be understood as describing the relative relationships between the components or the spatial orientation of various aspects of these components, since the components described herein can be oriented in any desired direction. When used to describe the range of dimensions or other characteristics (such as time, pressure, temperature, length, width, etc.) of elements, operations, and / or conditions, the phrase “between X and Y” indicates a range including both X and Y.

[0022] Furthermore, reference numerals and / or letters may be repeated in various examples within this disclosure. Such repetition is for simplicity and clarity and does not in itself prescribe a relationship between the various embodiments and / or configurations discussed. Exemplary embodiments that can be used to implement the features and functions of this disclosure will now be described in more detail with reference to the accompanying drawings.

[0023] refer to Figure 1 A conventional computed tomography (CT) scanning system 100 uses X-rays 101 generated by an X-ray source 102 and passing through an object of interest 104. The X-rays are converted into light 108 by a collimator and scintillator 106, and the light 108 is captured by a detector implemented as a photodiode array 110. The photodiode array 110 converts the light 108 into an analog electrical signal 112, which is then converted into a digital signal 114 using an analog-to-digital (A / D) converter 116. The digital signal output by the A / D converter is used to generate a grayscale image known as a CT scan.

[0024] PCCT imaging offers significant advantages and improvements over existing CT imaging techniques. A PCCT system employs a photon counting detector (PCD) comprising a semiconductor layer to realize an array of detector pixels. By tracking the deposited energy of each interaction, the PCD's detector pixels record the approximate energy spectrum and intensity of photons, making PCCT a spectral or energy-resolved CT technique. In contrast, conventional CT scanners use an energy integration detector (EID), which records the total energy of one or more photons along with electronic noise deposited in the pixel over a fixed time period. Therefore, EID only records photon intensity, similar to black and white photography. In contrast, PCD records both photon intensity and spectral information, similar to color photography.

[0025] PCCT imaging transforms the aforementioned three-step process into a more streamlined, direct conversion from X-rays to charge via a semiconductor layer comprising a PCD. Specifically, the semiconductor material used to realize the PCD efficiently converts each X-ray photon into a charge burst proportional to the X-ray energy. The benefits of this technique include improved signal-to-noise ratio, reduced X-ray dose to the patient (due to the ability to achieve higher resolution with the same X-ray dose), improved spatial resolution, and the ability to distinguish between various contrast agents and different types of materials / tissues by using multiple "energy boxes."

[0026] When photons interact in a PCD, the height of the resulting electrical pulse is roughly proportional to the photon energy. By comparing each pulse generated in a pixel to an appropriate low-energy threshold, contributions from low-energy events (generated by photon interactions and electronic noise) can be filtered out. Therefore, compared to EID, PCD offers a higher signal-to-noise ratio and contrast-to-noise ratio, enabling improved image quality at the same X-ray exposure level, or a reduction in patient X-ray dose while maintaining the same image quality.

[0027] Introducing more energy thresholds above the low energy threshold allows the PCD to be divided into multiple discrete energy boxes. Each registered photon is assigned to a specific box according to its energy, thus measuring a histogram of the incident X-ray spectrum for each pixel. This spectral information can qualitatively determine the material composition of each pixel in the reconstructed CT image, compared to the estimated average linear attenuation coefficient obtained in a conventional CT scan. Furthermore, using more than two energy boxes allows for the differentiation of dense bone and calcification from heavier elements typically used as contrast agents, reducing the need for a reference scan before contrast agent injection and further reducing the X-ray dose received by the patient.

[0028] Figure 2 A schematic diagram of an example signal processing architecture for a PCCT system 200, including a PCD comprising multiple detector pixels, is shown. Figure 2The current pulse is represented by a single pixel. In operation, the current pulse originates from sensor 202, is amplified by charge-sensitive amplifier (CSA) 204, and shaped by pulse shaper (PS) 206. The voltage pulse output from PS 206 is input to a set of N discriminators (or comparators) 208, which compare the pulse to N incrementing voltage thresholds. The set of discriminators 208 creates a pulse digital output in a "thermometer code". Counter 210 can count the pulses at each level or threshold, and the resulting count value (which can be temporarily stored in result register 212) represents how many X-ray hits occurred at each of the N thresholds. It will be appreciated that the thresholds are set to match different voltages corresponding to photons of different energies. According to the features of the embodiments described herein, in addition to the quantitative counters corresponding to each of the N thresholds, counter 210 also includes a qualitative counter, the purpose of which will be described in more detail below.

[0029] Figure 3 It is shown Figure 2 The graph shows the results of a simulation example of the PCCT system, where there are no overlapping charging events. The first waveform 300 represents the excitation current from sensor 202, and the second waveform 302 represents the corresponding shaper voltage from PS 206 and the increased voltage discriminator threshold voltage (vth[0]-vth[4]), in millivolts (mV). Waveform 304 represents the corresponding pulse counted by counter 210 at each level. Finally, waveform 306 represents the input of discriminator 208 to the output of counter 210. Figure 3 The lieutenant general noted that for each current pulse, a voltage pulse from the pulse shaper produces an output on discriminator 208. Counter 210 counting the peak discriminator output for each pulse is the desired response.

[0030] When all pulses are sufficiently spaced in time, there are several ways to efficiently implement a counter to count and "store" the pulses. Two common techniques for doing this include asynchronous edge counting and peak-zero counting. With asynchronous edge counting, an asynchronous counter is associated with each discriminator output. As a result, the counter increments for any energy level higher than the threshold level of the associated discriminator. If a "boxed" value is needed, for each counter, the count of the higher threshold level counter must be subtracted from the count to determine the correct count for the threshold level. For example, for each discriminator 1-N count, the counter associated with discriminator 0 also increments; therefore, to obtain an accurate level 0 count, the counts of discriminators 1-N must be subtracted from the count of discriminator 0. Similarly, for each discriminator 2-N count, the counter associated with discriminator 1 also increments; therefore, to obtain an accurate level 1 count, the counts of discriminators 2-N must be subtracted from the count of discriminator 1.

[0031] Using peak-zero counting, the edge of the signal output from discriminator 0 is used to determine which counter to increment. This method essentially increments only the maximum discriminator count that occurs between the rising and falling edges of discriminator 0.

[0032] Asynchronous edge counting and peak zero counting both work correctly when the events being counted are spaced apart without any overlap. If there are no other charging events, there will always be an ordered sequence, starting and ending with the rising and falling edges of discriminator 0. Below the maximum switching discriminator, all levels will have a rising edge.

[0033] In reality, charging events may occur too close together to be distinguished from each other, potentially leading to multiple charging events being counted as a single charging event with incorrect energy. This phenomenon is commonly referred to as "stacking," and examples include... Figure 4A As shown. Reference Figure 4A Graph 400 shows two instances of the stacking, denoted by reference numerals 402a and 402b. Specifically, instance 402a corresponds to the stacking of two overlapping charge events 404a and 404b. Instance 402b corresponds to the stacking of three overlapping charge events 406a-406c.

[0034] Furthermore, charge events can occur at the boundaries between adjacent pixels, causing charge energy to split between (or between) pixels. This phenomenon is often referred to as "charge sharing," and examples include... Figure 4B As shown. Reference Figure 4B Charge event 410 occurs on boundary 412 between pixels 414 and 416, resulting in charge sharing among these pixels. Conversely, charge event 418 occurs entirely within the boundary of pixel 420.

[0035] When measuring photon energy, both accumulation and charge sharing can lead to errors. During a measurement frame, some events may be affected by accumulation and / or charge sharing, while others may not.

[0036] Various charging event counting techniques have been proposed and implemented. For example, the technique referred to in this paper as the "tickdown" counter uses an asynchronous state machine to count "down tick" events to maximize the probability of matching the total event count. Another approach adopted is called the ToT technique, where events at a spectral threshold are immediately counted and the timer is reset if the time exceeding the spectral threshold is longer than the expected time for a single event. The ToT technique improves counting performance, especially at high throughput. One approach to reduce the impact of charge sharing can be called the "overlapping counter" method, which attempts to correct for individual events under the influence of charge sharing.

[0037] Based on the features of embodiments of the QPS system described herein, if accumulation and / or charge sharing events can be detected, the corresponding charge events can be counted by a qualitative counter to maintain an accurate record of the total count. The energy-sensitive quantitative detector classifies only events unaffected by accumulation and / or charge sharing. As long as a statistically significant number of qualitative events can be measured during the measurement frame, the entire energy spectrum can be estimated without systematic errors caused by charge sharing and accumulation. In some embodiments, QPS techniques are combined with ToT techniques to improve performance. Unlike the coincidence counter method, in the QPS method described herein, charge sharing is detected and the corresponding events are ignored in order to estimate the energy spectrum.

[0038] Figure 5A This is a flowchart illustrating an example operation of an embodiment of a QPS system. For example... Figure 5A As shown, the event detected at the pixel (step 500) is quantized (step 502), and then in step 504, it is determined whether the quantized event exhibits a monotonic up-down characteristic, indicating that the detected event is not affected by stacking. Specifically, this condition is met if and only if the quantized event consists of only a series of low-to-high transitions starting from the baseline level and a series of high-to-low transitions ending at the baseline level. If not (indicating that the detected charging event is affected by stacking), then in step 506, the event is counted by a qualitative counter; otherwise, in step 510, it is determined whether the ToT parameter has been exceeded. If the ToT parameter has been exceeded, then in step 506, the event is counted by a qualitative counter (or, based on the amount of time exceeding the ToT parameter); otherwise, in step 512, it is determined whether any adjacent pixels 514 have detected overlapping events, indicating charge sharing. If one or more adjacent pixels 516 are determined to have detected overlapping events, then in step 506, the event is counted by a qualitative counter; otherwise, in step 516, the event is binned by a quantitative counter.

[0039] Figure 5B This is a state machine illustrating example operation of a QPS system according to an embodiment described herein. Figure 5B The state variables of the state machine are defined as follows:

[0040] disc_nz: Discriminator output is non-zero (also known as disc_out[0])

[0041] neighbor_nz: At least one neighbor (N, S, E, W) discriminator output is a non-zero OR of the discriminator output of all neighbors' disc_nz.

[0042] disc_dir: The final output direction of the discriminator

[0043] 0 → Last CD output was higher

[0044] 1→The last CD output was low

[0045] t_over_t: Time indicator for exceeding the threshold

[0046] 0 → Absent

[0047] 1→The timeout timer has expired.

[0048] Figure 5B The output of the state machine is defined as follows:

[0049] +QUAL_CT: Incrementing qualitative pulse counter

[0050] +QUANT_CT[N]: Incremental quantitative pulse counter for cell N.

[0051] After the counter is incremented, t_over_t is reset to zero. It should be noted that more internal state variables than defined above may be needed to track the state history.

[0052] Figure 6A The diagram illustrates the count of events 600 detected at a POI, according to an embodiment of the QPS counting method described herein. Figure 6A As shown, event 600 is unaffected by superposition (i.e., the POI discriminator output waveform is monotonically up and down and does not exceed ToT) or charge sharing (no activity on the waveform corresponding to the output of the orthogonal adjacent discriminators); therefore, event 600 is counted by the quantitative counter corresponding to bin 2 (represented by waveform 602).

[0053] Figure 6B The diagram illustrates the count of events 610 detected at a POI, according to an embodiment of the QPS counting method described herein. (See diagram for example.) Figure 6B As shown, event 610 is unaffected by superposition (i.e., the POI discriminator output waveform is monotonically up and down and does not exceed ToT); however, event 610 is affected or charge-shared as indicated by activity on at least one of the waveforms corresponding to the outputs of the orthogonal adjacent discriminators (i.e., waveform 612). As a result, event 610 is counted by a qualitative counter (represented by waveform 614).

[0054] Figure 6C The diagram illustrates the count of events 620 detected at a POI, according to an embodiment of the QPS counting method described herein. (See diagram for reference.) Figure 6CAs shown, event 620 is unaffected by charge sharing (no activity on the waveform corresponding to the output of the quadrature adjacent discriminator); however, event 620 is affected by accumulation, as shown by ToT exceeding 2x in bin 4 (waveform 622). As a result, event 620 is counted 2x by the quantitative counter (represented by waveform 624).

[0055] Figures 7A-7D Quantitative and qualitative counting curves for various PCCT counting methods are shown, including tickdown compared to ground truth. Figure 7A ), QPS Figure 7B ), tickddown with ToT ( Figure 7C ) and having ToT ( Figure 7D QPS. Note that QPS and the ToT method significantly improve the correlation between the estimated and actual total counts, as well as the correlation between the estimated and actual proportions of the warehouse counts.

[0056] For the purpose of comparison, Figure 8 The total count curves for QPS with and without ToT are shown. As the throughput increases, the number of quantitative counts increases monotonically, while the number of qualitative counts decreases. Measurements at the high end of the throughput range contain almost no spectral information. This is a useful feature of the QPS method because the low proportion of qualitative counts relative to the total count can be used to indicate that the signal does not contain useful spectral information. In some embodiments, ignoring the spectrum of a measurement based on such an indicator may be beneficial rather than providing inaccurate spectral estimates.

[0057] Charge sharing leads to spectral shifts, primarily due to high-energy photons from neighboring pixels that share a significant portion of the charge with lower-positioned points of interest (POIs). The QPS technique described in this paper can identify some of these events, thereby improving the accuracy of low-throughput spectra. Specific results will depend on the choice of discriminator threshold. QPS largely prevents spectral shifts caused by stacking, where high bin counts (e.g., bin 4) increase at the expense of other (lower) bins. Above 10 megacounts per second (Mcps), the number of quantitative counts is very small, and these can be ignored. As a result, systems employing QPS can detect situations where almost every charge event in a measurement frame is affected by charge sharing or stacking, thus highly corrupting and effectively rendering the frame's spectral information useless. In other systems, corrupted spectral information might be used to incorrectly present inaccurate results as reliable.

[0058] The ultimate goal of CT scans is to generate 3D images of objects from which different materials can be identified. Therefore, one way to benchmark PCCT counting methods is to use them to perform material identification tasks. For example, counting data from a single pixel can be used to estimate the proportion of different materials present along a simulated linear X-ray photon trajectory.

[0059] Figure 9A and 9B The results of such a material identification experiment are shown, where simulated data correspond to X-ray beams passing through 10 cm of water (similar to the X-ray absorption of human tissue) and 1 cm of bone. Water and bone have different X-ray absorption characteristics, so the proportion of water and bone along the simulated trajectory can be estimated using the number of received photons.

[0060] Figure 9A This represents a series of estimates of bone thickness in a simulated dataset. Figure 9A In the table, the first column, labeled "GT (Analysis)," shows the actual bone thickness used to generate the simulation data. The other columns represent estimates of this bone thickness based on a series of Monte Carlo simulations using three different hypothetical photon counters. The second column, labeled "GT (Simulation)," represents an estimate based on an ideal photon counter that obtains the correct energy from each photon event, unaffected by stacking and charge sharing. Errors in this estimate are caused by the finite sample size of photons arriving at the detector within a finite time range. The third column, labeled "tickdown," shows an estimate based on a simulated photon counter using the "tickdown" method. The fourth column, labeled "QPS," represents an estimate based on a simulated photon counter using the QPS method.

[0061] Figure 9B The results of the same experiment are shown when estimating the thickness of water in a simulated dataset.

[0062] Figure 9A and 9B Experimental results show that the QPS method performs material identification tasks with better accuracy than the tickdown method.

[0063] Figure 10 This is a block diagram illustrating an example system 1100, which can be configured to implement at least a portion of the techniques according to the embodiments described herein, and more specifically, as shown in the figures described above. Figure 10As shown, system 1100 may include at least one processor 1102, such as a hardware processor 1102, coupled to memory element 1104 via system bus 1106. Thus, the system can store program code and / or data within memory element 1104. Furthermore, processor 1102 can execute program code accessed from memory element 1104 via system bus 1106. In one aspect, the system may be implemented as a computer suitable for storing and / or executing program code. However, it should be understood that system 1100 may be implemented in the form of any system including a processor and memory capable of performing the functions described in this disclosure.

[0064] In some embodiments, processor 1102 may execute software or algorithms to perform the activities discussed in this specification; particularly those related to the embodiments described herein. Processor 1102 may include any combination of hardware, software, or firmware providing programmable logic, including, as non-limiting examples, microprocessors, DSPs, field-programmable gate arrays (FPGAs), programmable logic arrays (PLAs), integrated circuits (ICs), application-specific integrated circuits (ASICs), or virtual machine processors. Processor 1102 may be communicatively coupled to memory element 1104, for example, in a direct memory access (DMA) configuration, such that processor 1102 can read from or write to memory element 1104.

[0065] Typically, memory element 1104 may include any suitable volatile or non-volatile memory technology, including double data rate (DDR) random access memory (RAM), synchronous RAM (SRAM), dynamic RAM (DRAM), flash memory, read-only memory (ROM), optical media, virtual memory regions, magnetic storage, or magnetic tape storage, or any other suitable technology. Unless otherwise specified, any memory element discussed herein should be construed as included within the broad term "memory". Information measured, processed, tracked, or sent to or from any component of system 1100 may be available in any database, register, control list, cache, or storage structure, all of which may be referenced at any suitable time. Any such storage option may be included within the broad term "memory" as used herein. Similarly, any potential processing elements, modules, and machines described herein should be understood as included within the broad term "processor". Each element shown in this figure may also include a suitable interface for receiving, transmitting, and / or otherwise transferring data or information in a networked environment, such as a system having similar or identical hardware to another of these elements.

[0066] In some exemplary implementations, the mechanisms for implementing the embodiments outlined herein may be implemented by logic encoded in one or more tangible media, which may include non-transitory media, such as ASIC, DSP instructions, embedded logic provided in software (potentially including object code and source code), executed by a processor or other similar machine, etc. In some instances, memory elements (e.g., Figure 10 The memory element 1104 shown herein can store data or information used for the operations described herein. This includes the memory element's ability to store software, logic, code, or processor instructions that are executed to perform the activities described herein. A processor can execute any type of instructions associated with data or information to implement the operations detailed herein. In one example, such as Figure 10 The processor 1102 shown herein can transform elements or items (e.g., data) from one state or thing to another. In another example, the activities outlined herein can be implemented with fixed logic or programmable logic (e.g., software / computer instructions executed by a processor), and the elements identified herein can be some type of programmable processor, programmable digital logic (e.g., FPGA, DSP, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)), or an ASIC that includes digital logic, software, code, electronic instructions, or any suitable combination thereof.

[0067] Memory element 1104 may include one or more physical memory devices, such as local memory 1108 and one or more mass storage devices 1110. Local memory may refer to RAM or other non-persistent memory devices that are typically used during the actual execution of the program code. Mass storage devices may be implemented as hard disk drives or other persistent data storage devices. Processing system 1100 may also include one or more cache memories (not shown) that provide temporary storage for at least some of the program code to reduce the number of times the program code must be retrieved from mass storage device 1110 during execution.

[0068] like Figure 10 As shown, memory element 1104 can store the energy storage event counting module 1120. In various embodiments, module 1120 can be stored in local memory 1108, one or more mass storage devices 1110, or separately from both local memory and mass storage devices. It should be understood that system 1100 can further execute an operating system that can facilitate the execution of module 1120. Figure 10(Not shown in the diagram). Module 1120, implemented in the form of executable program code and / or data, can be read, written, and / or executed by system 1100 (e.g., by processor 1102). In response to reading from, writing to, and / or executing module 1120, system 1100 can be configured to perform one or more operational or method steps described herein.

[0069] Optionally, the input / output (I / O) devices depicted as input device 1112 and output device 1114 may be coupled to the system. Examples of input devices may include, but are not limited to, a keyboard, a pointing device such as a mouse, etc. Examples of output devices may include, but are not limited to, a monitor or display, a speaker, etc. In some implementations, the system may include a device driver (not shown) for output device 1114. Input and / or output devices 1112, 1114 may be coupled to system 1100 directly or via an intermediate I / O controller. Furthermore, sensor 1115 may be coupled to system 1100 directly or via an intermediate controller and / or driver.

[0070] In one embodiment, the input and output devices can be implemented as a combined input / output device (in... Figure 10 (Shown as dashed lines around input device 1112 and output device 1114). An example of such a combined device is a touch-sensitive display, sometimes also called a "touchscreen display" or simply a "touchscreen". In such an embodiment, input to the device can be provided by the movement of a physical object (e.g., a user's stylus or finger) on or near the touchscreen display.

[0071] Optionally, network adapter 1116 may also be coupled to system 1100 to enable it to couple to other systems, computer systems, remote network devices, and / or remote storage devices via an intervening private or public network. The network adapter may include a data receiver for receiving data transmitted to system 1100 by said systems, devices, and / or networks, and a data transmitter for transmitting data from system 1100 to said systems and / or devices. Modems, cable modems, and Ethernet cards are examples of different types of network adapters that can be used with system 1100.

[0072] Example 1 provides a method for counting charge events detected by a pixel in a photon counting computed tomography (PCCT) scanning system including a plurality of discriminators, wherein each discriminator is associated with a corresponding one of a plurality of threshold voltage levels, the method comprising: detecting a signal output from one of the discriminators; incrementing a quantitative count corresponding to the threshold voltage level associated with one of the discriminators if the detected discriminator output signal satisfies a first condition; and incrementing a qualitative count if the detected discriminator output signal satisfies at least one second condition.

[0073] Example 2 provides the method of Example 1, wherein the at least one second condition includes the expiration of a threshold (ToT) timer.

[0074] Example 3 provides the method of Example 2, and further includes, upon the expiration of the ToT timer: incrementing the qualitative count; and resetting the ToT timer.

[0075] Example 4 provides the method of Example 1, wherein the at least one second condition includes a signal output from one of the discriminators overlapping with a signal output from a discriminator associated with a neighboring pixel.

[0076] Example 5 provides the method of Example 1, wherein the at least one second condition includes an output signal from one of the discriminators, the signal comprising only a monotonic sequence of only one low-to-high transition and only a monotonic sequence of only one high-to-low transition.

[0077] Example 6 provides the method of Example 1, wherein the first condition includes the absence of the at least one second condition.

[0078] Example 7 provides the method of Example 1, wherein the plurality of discriminators includes five discriminators.

[0079] Example 8 provides the method of Example 1, wherein the plurality of threshold voltage levels includes five threshold voltage levels.

[0080] Example 9 provides the method of Example 1, wherein each of the discriminators compares a voltage signal input to the discriminator with a threshold voltage level associated with the discriminator.

[0081] Example 10 provides the method of Example 9, wherein the output of each of the discriminators is driven high when the voltage signal input to the discriminator exceeds a threshold voltage level associated with the discriminator.

[0082] Example 11 provides the method of Example 1, wherein the spectral information is ignored if a specific threshold for the total number of qualitative counts is not reached.

[0083] Example 12 provides a method for counting charge events detected by a pixel in a photon-counting computed tomography (PCCT) scanning system comprising a plurality of discriminators, wherein each discriminator is associated with a corresponding one of a plurality of threshold voltage levels, the method comprising: detecting a signal output from one of the discriminators; and incrementing a qualitative count when at least one of the following occurs: a timeout (ToT) timer expires; the signal output from one of the discriminators overlaps with a signal output from a discriminator associated with a neighboring pixel; and the signal output from one of the discriminators comprises only a monotonic low-to-high transition and a monotonic high-to-low transition; otherwise, incrementing a quantitative count corresponding to a threshold voltage level associated with one of the discriminators.

[0084] Example 13 provides the method of Example 12, further comprising, upon the expiration of the ToT timer: incrementing the qualitative count; and resetting the ToT timer.

[0085] Example 14 provides a photon counting computed tomography (PCCT) scanning system, comprising: a plurality of discriminators, wherein each discriminator is associated with a corresponding one of a plurality of threshold voltage levels; and a counting circuit configured to: detect a signal output from one of the discriminators; and if the detected discriminator output signal satisfies a first condition, increment a quantitative count corresponding to the threshold voltage level associated with one of the discriminators; and if the detected discriminator output signal satisfies at least one second condition, increment a qualitative count.

[0086] Example 15 provides the PCCT scanning system of Example 14, wherein the at least one second condition includes the expiration of a threshold (ToT) timer.

[0087] Example 16 provides the PCCT scanning system of Example 15, and further includes, upon the expiration of the ToT timer: incrementing the qualitative count; and resetting the ToT timer.

[0088] Example 17 provides the PCCT scanning system of Example 14, wherein the at least one second condition includes an overlap of a signal output from one of the discriminators with a signal output from a discriminator associated with a neighboring pixel.

[0089] Example 18 provides the PCCT scanning system of Example 14, wherein the at least one second condition includes an output signal from one of the discriminators, the signal comprising only a monotonic sequence of low-to-high transition and a monotonic sequence of high-to-low transition.

[0090] Example 19 provides the PCCT scanning system of Example 14, wherein the first condition includes the absence of the at least one second condition.

[0091] Example 20 provides the PCCT scanning system of Example 14, wherein the plurality of discriminators includes five discriminators.

[0092] Example 21 provides the PCCT scanning system of Example 14, wherein the plurality of threshold voltage levels includes five threshold voltage levels.

[0093] Example 22 provides the PCCT scanning system of Example 14, wherein each of the discriminators compares a voltage signal input to the discriminator with a threshold voltage level associated with the discriminator.

[0094] Example 23 provides the PCCT scanning system of Example 14, wherein the output of each of the discriminators is driven high when the voltage signal input to the discriminator exceeds a threshold voltage level associated with the discriminator.

[0095] It should be noted that all specifications, dimensions, and relationships (e.g., the number of elements, operations, steps, etc.) outlined herein are for illustrative and educational purposes only. Such information may be significantly altered without departing from the spirit of this disclosure or the scope of the appended claims. This specification applies only to a non-limiting example and should therefore be interpreted as such. Exemplary embodiments have been described with reference to specific component arrangements in the foregoing description. Various modifications and changes may be made to these embodiments without departing from the scope of the appended claims. Therefore, the description and drawings should be considered illustrative rather than restrictive.

[0096] Note that the interactions in the numerous examples provided herein can be described using two, three, four, or more electrical components. However, this is done merely for clarity and illustration. It should be understood that the system can be combined in any suitable manner. Along similar design alternatives, any components, modules, and elements shown in the figures can be combined in a wide variety of possible configurations, all of which are clearly within the broad scope of this specification. In some cases, it is easier to describe one or more functions of a given set of flows by referring to only a limited number of electrical components. It should be understood that the figures and the circuits they teach are readily expandable and can accommodate a large number of components as well as more complex / complex arrangements and configurations. Therefore, the examples provided should not limit the scope of the circuits or inhibit the broad teaching of the circuits, as the circuits can be applied to countless other architectures.

[0097] It should also be noted that in this specification, references to various features (e.g., elements, structures, modules, components, steps, operations, characteristics, etc.) included in “one embodiment,” “exemplary embodiment,” “another embodiment,” “some embodiments,” “various embodiments,” and “other embodiments” are intended to mean that any such feature is included in one or more embodiments of this disclosure, but may or may not be combined in the same embodiment.

[0098] It should also be noted that the functions related to the circuit architecture only illustrate some possible circuit architecture functions that can be performed by the system shown in the figures or within the system described in the figures. Where appropriate, some of these operations can be deleted or removed, or these operations can be significantly modified or changed without departing from the scope of this disclosure. Furthermore, the timing of these operations may vary considerably. The preceding operational flow is provided for illustrative and discussion purposes. The embodiments described herein offer substantial flexibility, as any suitable arrangement, timing, configuration, and timing mechanism can be provided without departing from the teachings of this disclosure.

[0099] Those skilled in the art can identify many other changes, substitutions, variations, alterations, and modifications, and this disclosure is intended to include all such changes, substitutions, variations, modifications, and alterations that fall within the scope of the appended claims.

[0100] Note that all optional features of the devices and systems described above can also be implemented with respect to the methods or processes described herein, and the details in the examples can be used anywhere in one or more embodiments.

[0101] In these cases, the “apparatus” (as described above) may include (but is not limited to) any suitable components used in this document, as well as any suitable software, circuitry, hubs, computer code, logic, algorithms, hardware, controllers, interfaces, links, buses, communication paths, etc.

[0102] Note that the interactions can be described using two, three, or four network elements for the examples provided above, as well as many other examples presented herein. However, this is done merely for clarity and illustration. In some cases, it is easier to describe one or more functions of a given set of flows by referring to only a limited number of network elements. It should be understood that the topologies shown and described with reference to the accompanying figures (and their teachings) are easily scalable and can accommodate a large number of components, as well as more complex / complex arrangements and configurations. Therefore, the examples provided should not limit the scope of the topologies shown or inhibit the extensive teachings that the topologies shown can be applied to countless other architectures.

[0103] It should also be noted that the steps in the preceding flowcharts only illustrate some possible signaling scenarios and patterns that can be performed by or within the communication system shown in the diagrams. Where appropriate, some of these steps can be deleted or removed, or these steps can be significantly modified or changed without departing from the scope of this disclosure. Furthermore, many of these operations are described as being performed simultaneously or in parallel with one or more additional operations. However, the timing of these operations can vary considerably. The preceding operational flow is provided for illustrative and discussion purposes. The communication system shown in the diagrams offers considerable flexibility, as any suitable arrangement, timing, configuration, and periodic mechanism can be provided without departing from the teachings of this disclosure.

[0104] Although this disclosure has been described in detail with reference to specific arrangements and configurations, these exemplary configurations and setups can be significantly modified without departing from the scope of this disclosure. For example, although this disclosure has been described with reference to specific communication exchanges, the embodiments described herein can be adapted to other architectures.

[0105] Those skilled in the art can identify many other changes, substitutions, variations, alterations, and modifications, and this disclosure is intended to include all such changes, substitutions, variations, modifications, and substitutions that fall within the scope of the appended claims. In order to assist the United States Patent and Trademark Office (USPTO) and any reader of any patent in this application in interpreting the appended claims, the applicant wishes to draw the attention of the applicant that: (a) unless the words “represent” or “step” are specifically used in a particular claim, none of the appended claims are intended to invoke anything existing at the date of this application under section 142, paragraph 6(6) of 35 United States Code; and (b) no statement in the specification is intended to limit this disclosure in any way not otherwise reflected in the appended claims.

Claims

1. A method for counting charge events in a photon-counting computed tomography (PCCT) scanning system, the method comprising: The signal output from one of a plurality of discriminators included in the PCCT scanning system is detected, wherein the discriminator is associated with a pixel in the PCCT scanning system, and each of the plurality of discriminators is associated with a corresponding threshold voltage level of a plurality of threshold voltage levels. In response to the detected signal output satisfying the first condition, a quantitative count corresponding to the threshold voltage level associated with the discriminator is increased; and In response to a detected signal output satisfying at least one second condition, a qualitative count is incremented, wherein the qualitative count defines the number of charge accumulation events, charge sharing events, or combinations thereof.

2. The method of claim 1, wherein the at least one second condition includes the expiration of a threshold (ToT) timer.

3. The method of claim 2, further comprising responding to the expiration of the ToT timer: Increase the qualitative count; and Reset the ToT timer.

4. The method of claim 1, wherein the at least one second condition includes the signal output overlapping with a second signal output from a discriminator associated with a neighboring pixel.

5. The method of claim 1, wherein the at least one second condition includes the signal output non-exclusively comprising a monotonic sequence of low-to-high transitions and a subsequent monotonic sequence of high-to-low transitions.

6. The method of claim 1, wherein the first condition includes the absence of the at least one second condition.

7. The method of claim 1, wherein the plurality of discriminators comprises five discriminators.

8. The method of claim 1, wherein the plurality of threshold voltage levels comprises five threshold voltage levels.

9. The method of claim 1, wherein a first discriminator of the plurality of discriminators compares a voltage signal input to the plurality of discriminators with a threshold voltage level associated with the first discriminator.

10. The method of claim 9, wherein when the voltage signal input to the plurality of discriminators exceeds a threshold voltage level associated with a first discriminator among the plurality of discriminators, the output of the first discriminator is driven high.

11. The method of claim 1, wherein spectral information is ignored when the threshold number of qualitative counts is not reached.

12. A method for counting charge events in a photon-counting computed tomography (PCCT) scanning system, the method comprising: The signal output from one of a plurality of discriminators included in the PCCT scanning system is detected, wherein the discriminator is associated with a pixel in the PCCT scanning system, and each of the plurality of discriminators is associated with a corresponding threshold voltage level of a plurality of threshold voltage levels. and The qualitative count increases in response to at least one of the following: The first condition is defined by the expiration of the Time Exceeds Threshold (ToT) timer; A second condition defined by the overlap of the signal output and the second signal output from the discriminator associated with the neighboring pixel; or The signal output non-exclusively includes a third condition defined by a monotonic sequence of low-to-high transitions starting from the baseline level and a subsequent monotonic sequence of high-to-low transitions terminating at the baseline level. as well as In the absence of the first, second, or third condition, a quantitative count corresponding to the threshold voltage level associated with the discriminator is incremented, wherein the qualitative count defines the number of charge accumulation events, charge sharing events, or combinations thereof.

13. The method of claim 12, further comprising responding to the expiration of the ToT timer: Reset the ToT timer.

14. A photon counting computed tomography (PCCT) scanning system, comprising: Multiple discriminators, wherein each discriminator is associated with a corresponding threshold voltage level among a plurality of threshold voltage levels; and The counting circuit is configured as follows: Detect the signal output from one of the plurality of discriminators; and In response to the detected signal output satisfying the first condition, a quantitative count corresponding to the threshold voltage level associated with the discriminator is increased; and In response to a detected signal output satisfying at least one second condition, a qualitative count is incremented, wherein the qualitative count defines the number of charge accumulation events, charge sharing events, or combinations thereof.

15. The PCCT scanning system of claim 14, wherein the at least one second condition includes the expiration of a time exceeding a threshold (ToT) timer.

16. The PCCT scanning system of claim 15, wherein the counting circuit is further configured to: in response to the expiration of the ToT timer. Increase the qualitative count; and Reset the ToT timer.

17. The PCCT scanning system of claim 14, wherein the at least one second condition includes the signal output overlapping with a second signal output from a discriminator associated with a neighboring pixel.

18. The PCCT scanning system of claim 14, wherein the at least one second condition includes the signal output non-exclusively comprising a monotonic sequence of low-to-high transitions and a subsequent monotonic sequence of high-to-low transitions.

19. The PCCT scanning system of claim 14, wherein the first condition includes the absence of the at least one second condition.

20. The PCCT scanning system of claim 14, wherein a first discriminator of the plurality of discriminators compares a voltage signal input to the plurality of discriminators with a threshold voltage level associated with the first discriminator, and wherein the output of the first discriminator is driven high in response to a voltage signal input to the plurality of discriminators exceeding the threshold voltage level associated with the first discriminator.

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