Patent ID: 12193867

DETAILED DESCRIPTION

For a better understanding, it may be useful to continue with an introductory description of non-limiting examples of an overall x-ray imaging system in which data processing and transferring according to the inventive concept may be implemented.

FIG.2is a schematic diagram illustrating an example of a CT imaging system1comprising an X-ray source10, which emits X-rays, an X-ray detector system20with an X-ray detector, which detects X-rays after they have passed through the object, analog processing circuitry25, which processes the raw electrical signals from the X-ray detector and digitizes it, digital processing circuitry40, which may carry out further processing operations on the measured data, such as applying corrections, storing it temporarily, or filtering, and a computer50, which stores the processed data and may perform further post-processing and/or image reconstruction. According to an exemplary embodiment, all or part of the analog processing circuitry25may be implemented in the X-ray detector system20. The X-ray source and X-ray detector may be coupled to a rotating member of a gantry15of the CT imaging system1.

The overall X-ray detector may be regarded as the X-ray detector system20, or the X-ray detector system20combined with the associated analog processing circuitry25.

In communication with and electrically coupled to the analog processing circuitry25is an imaging processing system30, which may include digital processing circuitry40and/or a computer50, which may be configured to perform image reconstruction based on the image data from the X-ray detector. The image processing system30may, thus, be seen as the computer50, or alternatively the combined system of the digital processing circuitry40and the computer50, or possibly the digital processing circuitry40by itself if the digital processing circuitry is further specialized also for image processing and/or reconstruction.

An example of a commonly used X-ray imaging system is a CT imaging system, which may include an X-ray source or X-ray tube that produces a fan beam or cone beam of X-rays and an opposing array of X-ray detectors measuring the fraction of X-rays that are transmitted through a patient or object. The X-ray source or X-ray tube and detector array are mounted in a gantry15that rotates around the imaged object.

FIG.3schematically shows a CT imaging system1as an illustrative example of an X-ray imaging system. The CT imaging system comprises a computer50receiving commands and scanning parameters from an operator via an operator console60that may have a display62and some form of operator interface, e.g., a keyboard, mouse, joystick, touch screen or other input device. The operator supplied commands and parameters are then used by the computer50to provide control signals to an X-ray controller41, a gantry controller42and a table controller43. To be specific, the X-ray controller41provides power and timing signals to the x-ray source10to control emission of X-rays onto the object or patient lying on the table12. The gantry controller42controls the rotating speed and position of the gantry11comprising the X-ray source10and the X-ray detector20. By way of example, the X-ray detector20may be a photon-counting X-ray detector. The table controller43controls and determines the position of the patient table12and the scanning coverage of the patient. There is also a detector controller44, which is configured for controlling and/or receiving data from the X-ray detector20.

In an embodiment, the computer50also performs post-processing and image reconstruction of the image data output from the X-ray detector20. The computer50thereby corresponds to the image processing system30as shown inFIGS.1and2. The associated display62allows the operator to observe the reconstructed images and other data from the computer50.

The X-ray source10arranged in the gantry11emits X-rays. An X-ray detector20, which may be in the form of a photon-counting X-ray detector, detects the X-rays after they have passed through the object or patient. The X-ray detector20may for example be formed by plurality of pixels, also referred to as sensors or detector elements, and associated processing circuitry, such as Application Specific Integrated Circuits (ASICs), arranged in detector modules. A portion of the analog processing part may be implemented in the pixels, whereas any remaining processing part is implemented in, for instance, the ASICs. In an embodiment, the processing circuitry (ASICs) digitizes the analog signals from the pixels. The processing circuitry (ASICs) may also comprise a digital processing part, which may carry out further processing operations on the measured data, such as applying corrections, storing it temporarily, and/or filtering. During a scan to acquire X-ray projection data, the gantry and the components mounted thereon rotate about an isocenter13.

Modem X-ray detectors normally need to convert the incident X-rays into electrons, this typically takes place through the photoelectric effect or through Compton interaction and the resulting electrons are usually creating secondary visible light until its energy is lost and this light is in turn detected by a photo-sensitive material. There are also detectors, which are based on semiconductors and in this case the electrons created by the X-ray are creating electric charge in terms of electron-hole pairs which are collected through an applied electric field.

There are detectors operating in an energy integrating mode in the sense that they provide an integrated signal from a multitude of X-rays. The output signal is proportional to the total energy deposited by the detected X-rays.

X-ray detectors with photon counting and energy resolving capabilities are becoming common for medical X-ray applications. The photon counting detectors have an advantage since in principle the energy for each X-ray can be measured which yields additional information about the composition of the object. This information can be used to increase the image quality and/or to decrease the radiation dose.

Generally, a photon-counting X-ray detector determines the energy of a photon by comparing the height of the electric pulse generated by a photon interaction in the detector material to a set of comparator voltages. These comparator voltages are also referred to as energy thresholds. Generally, the analog voltage in a comparator is set by a digital-to-analog converter (DAC). The DAC converts a digital setting sent by a controller to an analog voltage with respect to which the heights of the photon pulses can be compared.

A photon-counting detector counts the number of photons that have interacted in the detector during a measurement time. A new photon is generally identified by the fact that the height of the electric pulse exceeds the comparator voltage of at least one comparator. When a photon is identified, the event is stored by incrementing a digital counter associated with the channel.

When using several different threshold values, a so-called energy-discriminating photon-counting detector is obtained, in which the detected photons can be sorted into energy bins corresponding to the various threshold values. Sometimes, this type of photon-counting detector is also referred to as a multi-bin detector. In general, the energy information allows for new kinds of images to be created, where new information is available and image artifacts inherent to conventional technology can be removed. In other words, for an energy-discriminating photon-counting detector, the pulse heights are compared to a number of programmable thresholds (Ti-TN) in the comparators and are classified according to pulse-height, which in turn is proportional to energy. In other words, a photon counting detector comprising more than one comparator is here referred to as a multi-bin photon counting detector. In the case of multi-bin photon counting detector, the photon counts are stored in a set of counters, typically one for each energy threshold. For example, counters can be assigned to correspond to the highest energy threshold that the photon pulse has exceeded. In another example, counters keep track of the number of times that the photon pulse cross each energy threshold.

As an example, edge-on is a special, non-limiting design for a photon-counting detector, where the X-ray sensors such as X-ray detector elements or pixels are oriented edge-on to incoming X-rays.

For example, such photon-counting detectors may have pixels in at least two directions, wherein one of the directions of the edge-on photon-counting detector has a component in the direction of the X-rays. Such an edge-on photon-counting detector is sometimes referred to as a depth-segmented photon-counting detector, having two or more depth segments of pixels in the direction of the incoming X-rays.

Alternatively, the pixels may be arranged as an array (non-depth-segmented) in a direction substantially orthogonal to the direction of the incident x-rays, and each of the pixels may be oriented edge-on to the incident x-rays. In other words, the photon-counting detector may be non-depth-segmented, while still arranged edge-on to the incoming X-rays.

By arranging the edge-on photon-counting detector edge-on, the absorption efficiency can be increased, in which case the absorption depth can be chosen to any length, and the edge-on photon-counting detector can still be fully depleted without going to very high voltages.

A conventional mechanism to detect X-ray photons through a direct semiconductor detector basically works as follows. The energy of the X-ray interactions in the detector material are converted to electron-hole pairs inside the semiconductor detector, where the number of electron-hole pairs is generally proportional to the photon energy. The electrons and holes are drifted towards the detector electrodes and backside (or vice versa). During this drift, the electrons and holes induce an electrical current in the electrode, a current which may be measured.

As illustrated inFIG.4, signal(s) is/are routed26from detector elements22of the X-ray detector to inputs of parallel processing circuits (e.g., ASICs)25. It should be understood that the tenn Application Specific Integrated Circuit (ASIC) is to be interpreted broadly as any general circuit used and configured for a specific application. The ASIC processes the electric charge generated from each X-ray and converts it to digital data, which can be used to obtain measurement data such as a photon count and/or estimated energy. The ASICs are configured for connection to digital data processing circuitry so the digital data may be sent to further digital data processing40and/or one or more memory circuits or components45and finally the data will be the input for image processing30/50to generate a reconstructed image.

As the number of electrons and holes from one x-ray event is proportional to the energy of the X-ray photon, the total charge in one induced current pulse is proportional to this energy. After a filtering step in the ASIC, the pulse amplitude is proportional to the total charge in the current pulse, and therefore proportional to the X-ray energy. The pulse amplitude can then be measured by comparing its value with one or more thresholds (THR) in one or more comparators (COMP), and counters are introduced by which the number of cases when a pulse is larger than the threshold value may be recorded. In this way it is possible to count and/or record the number of X-ray photons with an energy exceeding an energy corresponding to respective threshold value (THR) which has been detected within a certain time frame.

The ASIC typically samples the analog photon pulse once every Clock Cycle and registers the output of the comparators. The comparator(s) (threshold) outputs a one or a zero depending on whether the analog signal was above or below the comparator voltage. The available information at each sample is, for example, a one or a zero for each comparator representing weather the comparator has been triggered (photon pulse was higher than the threshold) or not.

In a photon counting detector, there is typically a Photon Counting Logic which determines if a new photon has been registered and, registers the photons in counter(s). In the case of a multi-bin photon counting detector, there are typically several counters, for example one for each comparator, and the photon counts are registered in the counters in accordance with an estimate of the photon energy. The logic can be implemented in several different ways. Two of the most common categories of Photon Counting Logic are the so-called non-paralyzable counting modes, and the paralyzable counting modes. Other photon-counting logics include, for example, local maxima detection, which counts, and possibly also registers the pulse height of, detected local maxima in the voltage pulse.

There are many benefits of photon-counting detectors including, but not limited to: high spatial resolution; less sensitivity to electronic noise; good energy resolution: and material separation capability (spectral imaging ability). However, energy integrating detectors have the advantage of high count-rate tolerance. The count-rate tolerance comes from the fact/recognition that, since the total energy of the photons is measured, adding one additional photon will always increase the output signal (within reasonable limits), regardless of the amount of photons that are currently being registered by the detector. This advantage is one of the main reasons that energy integrating detectors are the standard for medical CT today.

FIG.5shows a schematic illustration of a photon-counting circuit and/or device according to prior art.

When a photon interacts in a semiconductor material, a cloud of electron-hole pairs is created. By applying an electric field over the detector material, the charge carriers are collected by electrodes attached to the detector material. The signal is routed from the detector elements to inputs of parallel processing circuits, e.g., ASICs. It should be understood that the term Application Specific Integrated Circuit, ASIC, is to be interpreted broadly as any general circuit used and configured for a specific application. The ASIC processes the electric charge generated from each X-ray and converts it to digital data, which can be used to obtain measurement data such as a photon count and/or estimated energy. In one example, the ASIC can process the electric charge such that a voltage pulse is produced with maximum height proportional to the amount of energy deposited by the photon in the detector material.

The ASIC may include a set of comparators302where each comparator302compares the magnitude of the voltage pulse to a reference voltage. The comparator output is typically zero or one (0/1) depending on which of the two compared voltages that is larger. Here we will assume that the comparator output is one (1) if the voltage pulse is higher than the reference voltage, and zero (0) if the reference voltage is higher than the voltage pulse. Digital-to-analog converters (DACs),301can be used to convert digital settings, which may be supplied by the user or a control program, to reference voltages that can be used by the comparators302. If the height of the voltage pulse exceeds the reference voltage of a specific comparator, we will refer to the comparator as triggered. Each comparator is generally associated with a digital counter303, which is incremented based on the comparator output in accordance with the photon counting logic.

As previously mentioned, when the resulting estimated basis coefficient line integral Âi, for each projection line is arranged into an image matrix, the result is a material specific projection image, also called a basis image, for each basis i. This basis image can either be viewed directly (e.g., in projection x-ray imaging) or taken as input to a reconstruction algorithm to form maps of basis coefficients α1inside the object (e.g., in CT). Anyway, the result of a basis decomposition can be regarded as one or more basis image representations, such as the basis coefficient line integrals or the basis coefficients themselves.

It will be appreciated that the mechanisms and arrangements described herein can be implemented, combined and re-arranged in a variety of ways.

For example, embodiments may be implemented in hardware, or at least partly in software for execution by suitable processing circuitry, or a combination thereof.

The steps, functions, procedures, and/or blocks described herein may be implemented in hardware using any conventional technology, such as discrete circuit or integrated circuit technology, including both general-purpose electronic circuitry and application-specific circuitry.

Alternatively, or as a complement, at least some of the steps, functions, procedures, and/or blocks described herein may be implemented in software such as a computer program for execution by suitable processing circuitry such as one or more processors or processing units.

In the following, non-limiting examples of specific detector module implementations will be discussed. More particularly, these examples refer to edge-on oriented detector modules and depth-segmented detector modules. Other types of detectors and detector modules may also be feasible.

FIG.6is a schematic diagram illustrating an example of a semiconductor detector sub-module according to an exemplary embodiment. This is an example of a semiconductor detector sub-module with the semiconductor sensor21split into detector elements or pixels22, where each detector element (or pixel) is normally based on a diode having a charge collecting electrode as a key component. The X-rays enter through the edge of the semiconductor sensor.

FIG.7is a schematic diagram illustrating an example of semiconductor detector sub-module according to another exemplary embodiment. In this example, the semiconductor sensor21is also split into a plurality of so-called depth segments or detector elements22in the depth direction, again assuming the X-rays enter through the edge.

Normally, a detector element is an individual X-ray sensitive sub-element of the detector. In general, the photon interaction takes place in a detector element and the thus generated charge is collected by the corresponding electrode of the detector element.

Each detector element typically measures the incident X-ray flux as a sequence of frames. A frame is the measured data during a specified time interval, called frame time.

Depending on the detector topology, a detector element may correspond to a pixel, especially when the detector is a flat-panel detector. A depth-segmented detector may be regarded as having a number of detector strips, each strip having a number of depth segments. For such a depth-segmented detector, each depth segment may be regarded as an individual detector element, especially if each of the depth segments is associated with its own individual charge collecting electrode.

The detector strips of a depth-segmented detector nonnally correspond to the pixels of an ordinary flat-panel detector, and therefore sometimes also referred to as pixel strips. However, it is also possible to regard a depth-segmented detector as a three-dimensional pixel array, where each pixel (sometimes referred to as a voxel) corresponds to an individual depth segment/detector element.

The semiconductor sensors may be implemented as so called Multi-Chip Modules (MCMs) in the sense that the semiconductor sensors are used as base substrates for electric routing and for a number of ASICs which are attached preferably through so called flip-chip technique. The routing will include a connection for the signal from each pixel or detector element to the ASIC input as well as connections from the ASIC to external memory and/or digital data processing. Power to the ASICs may be provided through similar routing taking into account the increase in cross-section which is required for the large currents in these connections, but the power may also be provided through a separate connection. The ASICS may be positioned on the side of the active sensor and this means it can be protected from the incident X-rays if an absorbing cover is placed on top and it can also be protected from scattered X-rays from the side by positioning an absorber also in this direction.

FIG.8Ais a schematic diagram illustrating a semiconductor detector sub-module implemented as a MCM similar to embodiments in U.S. Pat. No. 8,183,535. In this example, it is illustrated how the semiconductor sensor21also can have the function of substrate in a MCM. The signal is routed by signal paths23from the detector elements or pixels22to inputs of parallel processing circuits24(e.g., ASICs) that are positioned next to the active sensor area. It should be understood that the term Application Specific Integrated Circuit (ASIC) is to be interpreted broadly as any general integrated circuit used and configured for a specific application. The ASICs process the electric charge generated from each X-ray and converts it to digital data which can be used to detect a photon and/or estimate the energy of the photon. The ASICs may have their own digital processing circuitry and memory for small tasks. And, the ASICs may be configured for connection to digital processing circuitry and/or memory circuits or components located outside of the MCM and finally the data will be used as input for reconstructing an image.

However, the employment of depth segments also brings two noticeable challenges to a silicon-based photon-counting detector. First, a large number of ASIC channels has to be employed to process data fed from the associated detector segments. In addition to the increased number of channels due to both the smaller pixel size and the depth segmentation, multi-energy bin further increases the data size. Second, since the given X-ray input counts are divided into smaller pixels, segments and energy bins, each bin has much lower signal and so the detector calibration/correction requires more than several orders of magnitude more calibration data to minimize statistical uncertainty.

Naturally, the several orders of magnitude larger data size slow down both data handling and pre-processing in addition to the need of larger computing resources, harddisk, memory and central processing unit (CPU)/graphics processing unit (GPU). When the size of data is 10 Gigabytes instead of 10 Megabyte, for example, the data handling time, read and write, can take 1000 times longer. For pileup (Radiation Detection and Measurement, Glenn F. Knoll., 3rdedition., John Wiley & Sons Inc, pp. 632-pp. 642) calibration vector generation, the pileup calibration data needs to be pre-processed for spit correction. For material decomposition vector generation, the material decomposition data needs to be pre-processed for both spit and pileup correction. For patient scan data, the data needs to be pre-processed for spit, pileup and material decomposition before the image reconstruction gets started. These are simplified examples to explain “pre-processing” since the actual pre-processing steps can include several other calibration steps as needed, like reference normalization and air calibration. The term “processing” may indicate only the final step in each calibration vector generation or patient scan, but it is used interchangeably in some cases.

FIG.8Bis a schematic diagram illustrating an example of a set of tiled detector sub-modules, where each detector sub-module is a depth-segmented detector sub-module and the ASICs or corresponding circuitry24are arranged below the detector elements22as seen from the direction of the incoming X-rays, allowing for routing paths from the detector elements22to the ASICs23in the space between detector elements.

The present invention relates to a system architecture for an improved data handling capability with respect to data processing and/or data transferring.

According to a first aspect there is provided a CT imaging system comprising a gantry including a rotating member on a rotating side and a stationary member on a stationary side. The rotating member on the rotating side comprises an X-ray source configured to emit X-rays, an X-ray detector configured to generate detector data, a data storage unit configured to store the detector data, and processing circuitry configured to process at least part of the stored detector data to generate a processed data set. The stationary member on the stationary side is communicatively coupled to the rotating member on the rotating side. The CT imaging system further comprises a data communication system configured to transfer the processed data set from the rotating member on the rotating side to the stationary member on the stationary side.

By way of example, the rotating member may be a rotating part/section/segment/portion, of the gantry, which is configured to rotate, e.g. around the subject/object to be imaged. The stationary member may be defined as a stationary part/section/segment/portion, of the gantry, which is arranged in a stationary manner on the stationary side, wherein the rotating and stationary member may be communicatively connected via a data communication system. e.g. a slip ring.

By storing data on a rotating side of a CT imaging system, processing at least a part of the data to generate a processed data set on the rotating side and transferring or sending the processed data set to the stationary side, it is possible to get relevant data at the stationary side in a fast, efficient and versatile manner. Processing at least part of the detector data on the rotating side may reduce the data size of the data being transferred via the data communication system, e.g. the slip ring, by factors of 2-20000×, making many calibration and/or imaging steps capable of sending the data within existing slip-ring bandwidth, thus speeding up the overall process of imaging and/or calibrating. The data storage unit may comprise a dedicated large memory, for example, non-volatile memory express (NVMe). The data storage unit on the rotating side may comprise, in addition or alternatively, a temporary memory needed during a continuous data processing, for example, ASIC, field-programmable gate array (FPGA) register or memory. The data storage unit may comprise, in addition or alternatively, a RAM (random access memory). The processing of the data stored on the rotating side may include one or more operations. As an example, an operation may be for example, but not limited to, X-ray source or X-ray tube spit correction, data accumulation, and pileup correction.

An X-ray tube “spit” refers to a temporary electrical short-circuit that sometimes occurs inside an X-ray tube. Typically, upon the occurrence of tube-spit, the supply of power to the X-ray tube is temporarily blocked to prevent arching and generates no X-ray output. A spit can be corrected and is currently applied at the stationary side, see U.S. Pat. No. 7,114,850. When the correction is done at the rotating side, it enables frame accumulation for detector data, e.g., calibration data, at the rotating side as well. As mentioned, with a given X-ray input, smaller pixel, depth segments and multi-energy bins reduce X-ray count in each bin by an order of magnitude (input X-ray counts/(pixel size ratio ×number of segments ×number of energy bins)). To generate a statistically meaningful calibration vectors, for example, pileup (each X-ray hit generates a certain length of electrical signal. Due to the finite length of the signal pulse, it can overlap with the next incoming X-ray pulses. The overlap is called “pileup”. It distorts both counts and energy distribution that needs to be corrected.) and materia decomposition requires many frames, 100-10000, accumulated or averaged. Due to the large amount of the data size, even with the latest computing power at the stationary side, rather simple spit and accumulation tasks take a while that is impractical. The distributed electronics at the rotating side. ASIC/FPGA/CPU (40/45inFIG.4,114/118/116inFIG.9) per subdetector, can parallelly be utilized to achieve the same goal without any delay or within unnoticeable time.

When the frames are accumulated, the data size is smaller which enables both quick data transfer though the data communication system, e.g., a slip ring, and faster processing of the detector data, e.g., calibration data, to generate pileup and material decomposition calibration vectors at the stationary side.

In addition, to make the data acquisition more efficient, pileup and material decomposition calibration vectors/algorithms can be loaded into a register/memory, e.g., the data storage unit, and concurrently applied to the data being collected. It eliminates the slower stationary side calibration pre-processing by utilizing the parallel detector electronics.

Once the data are corrected at the rotating side, pixels and segments can be combined to support different patient scan modes, for example, ultra-high resolution, high resolution, cardiac specific, axial scan, etc. One example patient scan mode requires ultra-high spatial resolution, another exemplary scan mode requires better material contrast that can be achieved by combining pixels to increase statistics. The combined data can be promptly transferred to the stationary side and reconstructed for patient diagnosis.

As an example, X-ray tube spit correction may be implemented as follows. While reading out one frame of the ASIC energy bin counts to an ASIC register/memory, the X-ray tube spit information for the frame gets broadcasted to all detector elements through a data acquisition board. The length of one frame is typically longer than 25 μsec to accumulate X-ray counts, and the spit broadcasting from an X-ray tube can be done in less than 1 μsec. During the time of the next frame collection, if a spit occurred in the current frame, a spit correction is applied to the current frame and the corrected current frame is moved to the next register/memory in ASIC. This allows the first register/memory space to be used for the next frame while the spit correction is applied seamlessly.

The spit corrected views can be accumulated as needed. As an exemplary, if 1000 frames are to be accumulated, the count from each frame may be summed. After the 1000th frame, the summed count gets transferred to the data communication unit, e.g.,130-1inFIG.9, and the register/memory gets reset for the next 1000 frames.

Since the modern FPGA has a great amount of computing resources, a processing circuitry can be implemented in FPGA to execute more complex algorithm. A simple example is to do view averaging and standard deviation calculation. A more complex algorithm will be applying a pileup algorithm to the data stream.

For example, the present system architectural invention allows data to be processed and transferred concurrently, which may speed up the process of using a CT imaging system and retrieving a result. The present invention may further speed up the process of retrieving a result, by allowing data to be promptly processed in the rotating side and turn them into a format which is faster and/or more efficient to transfer through the data communication system in terms of information sent per unit of time.

Furthermore, the present invention is advantageous in that it allows a CT imaging system to be more versatile with respect to selection of and timing of data for processing and transferring. In particular, by storing detector data in the data storage unit on the rotating side, without any pre-processing or compression, a CT imaging system with such improved versatility is achieved. For example, the system may be used in one way for a quick patient scan, and in another way for a more thorough examination of a subject/object, since it provides the option of choosing what data to process and send, and when. For the quick patient scan the system may process the detector data of a fill scan, by for example merging, with respect to view and/or pixels, on the rotating side, and transfer the processed data to the stationary side where e.g., the final steps of generating an image is performed. This allows a user of the CT imaging system to retrieve a good-enough result in a faster way. In the case of a thorough examination, the CT imaging system may transfer the full raw detector data as generated by the X-ray detector to the stationary side.

According to an embodiment, the processed data set comprises a reduced data set. By the term “reduced data set” it is here meant, but not limited to, a data set resulting from operations on a previous data set, e.g., the generated detector data, which reduces the size of the data. As mentioned, due to small pixel, depth segment and energy bins, detector calibration requires multiple same view/frame data to reduce statistical error. Examples of operations being performed on the same view data include averaging data per each energy bin and/or accumulating frame data per each energy bin, wherein a detector element may comprise at least one energy bins. The input can be e.g.,1000views and its output is one accumulated or averaged view. They can be achieved concurrently in ASIC while each view data was readout from the detector. Or the count can be transferred to a separate other memory and accumulated.

In the following, “output modes” of the processing circuitry will be described with reference to a number of optional features. It is to be understood that any combination of these features is envisioned by the inventors.

According to an embodiment, the processing circuitry is configured to operate in a plurality of output modes, each generating a respective processed data set. For example, the plurality of output modes may comprise an output mode for calibration and an output mode for patient imaging. The plurality of output modes may comprise a plurality of different calibration modes for a CT imaging system and a plurality of output modes for patient imaging.

The plurality of output modes may generate respective processed data sets, each being different from the other output modes with respect to the data size of the respective generated processed data set.

According to an embodiment, an output mode is selected in response to a request to generate a corresponding processed data set using the selected output mode. The present embodiment allows a user of the CT imaging system to request an output mode via a user interface. Hence, a user may at least partially decide how to rnm the CT imaging system, in terms of how data is handled. The user interface may be e.g., a display on a computer on the rotating side or the stationary side.

According to an embodiment, the processing circuitry is configured to select a pre-determined output mode to generate a corresponding processed data set using the pre-determined output mode, which allows a CT imaging system to run one or more output modes without the need for a user to request a certain output mode. For example, the CT imaging system may have one or more default modes that are predetermined.

According to an embodiment, the processing circuitry is configured to process the stored data using a set of consecutive output modes to generate respective processed data sets, and wherein the data communication system is configured to transfer the respective processed data sets consecutively. The present embodiment is advantageous in that the CT imaging system may operate in steps, wherein the steps may be predetermined. For example, this allows the CT imaging system to optimize how the detector data is stored, processed and transferred for first generating an initial image for quick diagnosis, followed by generating a more detailed image for final diagnosis. Furthermore, the present embodiment allows the CT imaging system to process and transfer one or more processed data sets without requiring input from a user, thus reducing downtime for the whole process by avoiding pauses between steps.

According to an embodiment, parts of a first processed data set is transferred via the data communication system, while other parts of the first processed data set is being generated, such that the processing of the detector data and the transferring of a processed data set from the rotating member on the rotating side to the stationary member on the stationary side is performed at least partially simultaneously. The present embodiment allows a CT imaging system to be used in a quicker and more efficient manner, essentially reducing the time it takes from performing the scan of the subject/object to producing an image reconstructed from the detector data.

According to an embodiment, the data communication system comprises a first data communication unit on the rotating member on the rotating side and a second data communication unit on the stationary member on the stationary side.

According to an embodiment, the data communication system comprises one or more slip rings.

According to an embodiment, the X-ray detector is configured to send the detector data to the data storage unit, and wherein the data storage unit is configured to store the generated detector data in its entirety. The present embodiment is advantageous in that all information from a scan using the CT imaging system is stored and can be processed or transferred, which allows a more versatile way to handle the detector data.

According to an embodiment, the data storage unit is a non-volatile memory, NVMe, and/or a Random Access Memory, RAM, which allows the CT imaging system to store detector data and/or processed data on the rotating side in order to optimize the data handling. The NVMe may provide more reliable storing of data, to e.g., minimize consequences due power loss.

According to an embodiment, the data storage unit is a set of transitory registers that is a part of the data processing circuitry.

According to an embodiment, the X-ray detector is a photon-counting detector. The present invention is especially useflul for detector technologies which generate large amounts of data, such as photon-counting detectors.

According to an embodiment, the X-ray detector is an energy-discriminating detector, such as a detector with multiple energy bins.

According to an embodiment, the processing of the detector data, to generate a processed data set, comprises combining detector data.

According to an embodiment, the processing circuitry is configured to process at least part of the generated detector data before it is stored on the data storage unit, in order to fuither optimize the data handling. Spit correction or pileup correction or other correction can be applied before the storage. After the storage, it can be transferred through the data communication unit, e.g., a slip ring, as it is, or segments, pixels and views can be combined depending on the patient data prescription. A filtering can be applied as well to smooth statistical variation.

According to an embodiment, the system comprises a second data storage unit, wherein the second data storage unit is configured to receive the processed data set from the rotating member on the rotating side, and a second set of processing circuitry, wherein the second set of processing circuitry is configured to process the received processed data set, wherein both the second data storage unit and the second set of processing circuitry are arranged on the stationary member on the stationary side.

For a better understanding, the proposed technology will now be described in further detail with reference toFIGS.9-13illustrating non-limiting examples of the data processing and transferring according to the invention.

FIG.9schematically shows a CT imaging system100according to an exemplifying embodiment of the present invention. InFIG.9the CT imaging system100comprises a rotating side110and a stationary side120. The rotating side110may comprise a gantry including a rotating member arranged on the rotating side110which is able to rotate around a subject/object, e.g., as described inFIG.3, with an X-ray source112arranged on one side of the gantry and an X-ray detector114arranged on the opposite side, such that X-rays emitted by the X-ray source112may pass through the subject/object and be received/detected at the X-ray detector114. The X-ray detector114may be a photon counting detector, and optionally also a detector with multiple energy bins that is energy-discriminating, e.g., as described inFIGS.3-7,8a,8b. The X-ray detector may alternatively be an energy-integrating detector (EID) in which the detected signal is proportional to the total energy deposited by all photons without specific information about an individual photon or its energy. The CT imaging system100further comprises a data storage unit116, which allows detector data from the X-ray detector114to be stored on the rotating side110. The data storage unit116may be a non-volatile memory. The CT imaging system100further comprises processing circuitry118which may receive data, such as detector data, and process it. By the term “processing circuitry” it is here meant circuitry, e.g., a processor, that is capable of performing operations, such as mathematical operations, for processing/transforming data. The processing circuitry may be digital processing circuitry.

The processing circuitry118and data storage unit116may be communicatively connected, such that data may be transferred between them. It is to be understood that the processing circuitry118may process detector data and/or already processed data, in order to get a resulting processed data set which may be transferred to the stationary side120. The processed data set may be a reduced data set, wherein a reduced data set may have a reduced data size.

The processing performed by the processing circuitry118may comprise one or more operations, e.g., to change the format, or reduce the size, of the data. For example, at least parts of the detector data may be averaged or accumulated in order to generate a reduced data set with reduced data size. The reduction of data size may be performed through lossy and/or lossless compression. The CT imaging system100further comprises a data communication system130, through which non processed detector data and/or processed detector data may be transferred from the rotating side110to e.g., a computer on the stationary side120.

By way of example, the data communication system130may comprise a first data communication unit130-1on the rotating side and a second data communication unit130-2on the stationary side. For example, the data communication system130may be a slip ring typically used in CT imaging systems with a rotating member of a gantry. By “slip ring” it is here meant, but not limited to, an electromechanical device that allows the transmission of power and electrical signals, e.g., power and data transfer between a rotating structure and a stationary structure. The CT imaging system100ofFIG.9may also comprise a display132coupled to the second data communication unit130-2and is configured to receive and display the processed data set.

FIG.10schematically shows CT imaging system100which is similar to the CT imaging system100inFIG.9. Since much of the configuration and operation of the CT imaging system100is substantially similar to that described inFIG.9, a detailed description of features common to the embodiment illustrated inFIG.9has been omitted to avoid needless prolixity and for the sake of brevity and conciseness.

InFIG.10the CT imaging system100comprises a second data storage unit126and a second set of processing circuitry128arranged on the stationary side120. The second data storage unit126is configured to receive the processed data set from the rotating side110, via the data communication system130. The second set of processing circuitry120may be configured to process the data received at the data storage unit126, in order to construct a final image of the scan of the object/subject. By way of example, the CT imaging system100may store the detector data in full. The CT imaging system100may process part of the detector data stored on the data storage unit116, on the rotating side110, with the processing circuitry118in order to generate a processed data set. The CT imaging system may also process all of the stored detector data on the rotating side110in order to generate a processed data set. The detector data being processed may be a copy of the stored detector data and/or the processed data set may be a new data set generated from the detector data set, thus allowing the same detector data to be processed multiple times in different ways.

The CT imaging system100may transfer the processed data set and/or detector data to the stationary side120, via the data communication system130. The transferred processed data set and/or detector data may be received by the data storage unit126and stored therein. For example, any processed data set and/or detector data may be processed on the stationary side120, in order to e.g., finalize image reconstruction of the detector data. Hence, detector data may be processed once on the rotating side110and generate a processed data set, then processing may be performed again on the processed data set on the stationary side120. Furthermore, the detector data may be transferred, in full, from the rotating side110to the stationary side120, even if a part of the detector data has been used to generate a processed data set which has already been transferred to the stationary side120. This may be useful in the scenario when a processed data set, based on detector data from a patient scan, is desired in a quicker manner to allow for quicker diagnosis, and a more thorough investigation is desired afterwards, based on the detector data in full.

The CT imaging system100may store any part of the detector data and/or processed data on the data storage unit116and/or the second data storage unit126.

FIG.11schematically shows CT imaging system100which is similar to the CT imaging system100inFIGS.9and10. Because much of the configuration and operation of the CT imaging system100is substantially similar to that described inFIGS.9and10, a detailed description of features common to the embodiment illustrated inFIGS.9and10has been omitted to avoid needless prolixity and for the sake of brevity and conciseness.

InFIG.11the X-ray detector114is an energy-discriminating detector comprising individual detector elements,114a/114b/114c/114d. The CT imaging system100may discern the detector data coming from a specific detector element114a/114b/114c/114d, store the detector data without losing the information on which detector element it originates from. The stored detector data may be processed by the processing circuitry118, by performing one or more operations. For example, one operation may be that detector data from different detector elements114a/114b/114c/114dare averaged, or that the data from certain elements, e.g., neighboring elements, are grouped together/accumulated. The CT imaging system provide the option of individually storing, processing and/or transferring, between the rotating side and the stationary side, detector data, and/or a processed data set from one or more detector elements114a/114b/114c/114d. The CT imaging system100ofFIG.11may also comprise a display132coupled to the second data communication unit130-2and is configured to receive and display the processed data set.

FIG.12schematically shows CT imaging system100which is similar to the CT imaging system100inFIGS.9,10and11. Because much of the configuration and operation of the CT imaging system100is substantially similar to that described inFIGS.9,10and11, a detailed description of features common to the embodiment illustrated inFIGS.9,10and11has been omitted to avoid needless prolixity and for the sake of brevity and conciseness.

InFIG.12the processing circuitry118is configured to operate in a plurality of output modes, wherein each output mode generates a respective processed data set. One or more output mode can be related to calibration of the CT imaging system100, and one or more modes may be related to patient imaging. Calibrating a CT imaging system100may comprise producing correction coefficients used for the reconstruction of a later scan. A purpose of the calibration may be to characterize system-specific behavior which can be compensated for later, either before/during scanning or after scanning. The calibration may be performed by scanning phantoms, wherein the phantoms may be objects which imitates the human body in terms of composition, e.g., in order to provide references such that a more accurate quantitative representation of the scanned object/subject can be provided by the CT imaging system100. Alternatively, calibration may be performed by scanning air, e.g., to normalize detector response at different locations in the detector. Another alternative is to calibrate by acquiring data with the X-ray source turned off, to e.g., characterize and compensate for phenomena due to detector electronics.

Calibration of the CT imaging system100may comprise taking multiple detector measurements to get multiple sets of detector data, and processing them together to compute the calibration coefficients. For instance, multiple consecutive scan/views, with corresponding detector data, taken at the same angle may be averaged together in order to reduce the influence of noise in the measurements and produce better statistics in the correction coefficients. One alternative is to transfer detector data to the stationary side120and perform the processing there; that could be quite slow when the bandwidth of the data communication system130is a bottleneck relative to the size of detector data. Another alternative is to generate one or more processed data sets on the rotating side110from the detector data, and transfer the processed data sets, which is smaller in data size than the detector data, which may allow faster transfer via the data communication system130.

The CT imaging system100may provide the option of operating in many different patient imaging modes, such as a primary patient scan mode which allows the process of generating a reconstructed image to be faster but less detailed. The reason why the CT imaging system100may provide e.g., images faster is because the CT imaging system100allows specification of which detector data, stored on the data storage unit116, that is to be processed by the processing circuitry118, and also how the detector data is processed. Further, it allows a specified processed data set to be transferred to the stationary side120via the data communication system130, allowing e.g., the most important/desired parts in the detector data to be processed and/or transferred to the stationary side120before the bulk of the detector data is processed and/or transferred. Another exemplary output mode is a secondary patient scan mode which provides more details in e.g., a reconstructed image, but takes longer to produce. The different output modes may be employed when scanning objects as well.

In a sense, an output mode may be regarded as a data processing mode in which a respective processed data set is generated and output for further use and/or transferring.

The respective processed data sets generated by a respective output mode may be different with respect to data size. For example, a first output mode may generate a first processed data set from a first part of the detector data, and a second output mode may generate a second processed data set from a second part of the detector data, wherein the first processed data set may be smaller in data size compared to the second processed data set. The detector data may be received from storage on the data storage unit116, or be received directly from the X-ray detector114, or from individual detector elements114a/114b/114c/114d. The processing circuitry118may perform different operations on the data depending on what output mode is being run. The first part of the detector data may be the same as, or part of, the second part of the detector data. Depending on what output mode is being run, the amount of detector data being processed on the rotating side110, and on the stationary side120, may be altered, as well as at what point in time detector data and/or processed data sets are transferred to the stationary side120.

The CT imaging system100may be configured, in e.g., the first output mode for patient imaging, to first produce a less detailed image based on the detector data from a scan of a subject/object, and afterwards produce a more detailed image of the scan. This may be done by initially generating the first processed data set from the first part of the detector data, followed by transferring the first processed data set via the data communication system130to the stationary side120. Subsequently, the CT imaging system100may be configured, in the first output mode, to transfer the remaining detector data to the stationary side120via the data communication system130, without processing it with the processing circuitry118. The first output mode of the CT imaging system thus allows an initial, quicker, scan to be performed and shown to a user of the system, while the remaining detector data may be processed and/or transferred afterwards.

The CT imaging system100may be configured, in e.g., the second output mode, to initially process the second part of the detector data to generate the second processed data set, transfer the second processed data set via the data communication system130, to the stationary side120, to provide an image based on the second processed data set. Subsequently, the CT imaging system100may be configured to process a third part of the detector data to generate a third processed data set, which is then transferred via the data communication system130, to the stationary side120, in order to provide a secondary image with information not present in the second processed data set, e.g., to achieve a more detailed image. The CT imaging system100ofFIG.12may also comprise a display132coupled to the second data communication unit130-2and is configured to receive and display the processed data set.

FIG.13is a schematic diagram illustrating an example of a method of operating a CT imaging system according to an embodiment.

According to a second aspect there is provided a method of operating a CT imaging system. The CT imaging system comprises a rotating side comprising an X-ray source configured to emit X-rays, an X-ray detector, a data storage unit, processing circuitry and a stationary side communicatively coupled to the rotating side via a data communication system.

The method basically comprises generating310detector data via the X-ray detector and storing320the detector data in the data storage unit. The method further comprises processing330the stored detector data, in the processing circuitry, to generate a processed data set. The method further comprises transferring340the processed data set from the rotating side to the stationary side via the data communication system. “Storing data” may be done with a dedicated memory and/or a transit register/memory in a processing circuitry. For example, when the generating detector data310is concurrently processed through a transit register,320and330may be reversed or320may be skipped.

According to an embodiment, the processing, in the processing circuitry, comprises selecting an output mode out of a plurality of output modes, each generating a respective processed data set. The present embodiment is advantageous in that the CT imaging system is more versatile, since it can store and process data according to a need or desire of a user.

According to an embodiment, the processing, in the processing circuitry, comprises selecting an output mode out of a plurality of output modes, wherein each of the plurality of output modes generates a respective processed data set each being different from the others with respect to data size of the processed data set. The present embodiment is advantageous in that the data handling may be customized to fit different time frames and requirements on the resulting image.

According to an embodiment, an output mode out of a plurality of output modes in response to a request may be selected, to generate a corresponding processed data set using the selected output mode.

According to an embodiment, the transferring comprises transferring parts of a first processed data set via the data communication system, while other parts of the first processed data set is being generated, such that the processing of the detector data and the transferring of a processed data set from the rotating side to the stationary side is performed at least partially simultaneously.

According to an embodiment, the detector data is sent to the data storage unit, and wherein the data storage unit is configured to store the generated detector data in its entirety.

According to an embodiment, the processing circuitry is configured to process at least part of the generated detector data before it is stored on the data storage unit.

According to an embodiment, the processed data from the rotating side may be received, on the stationary side, at a second data storage unit, and the processed data received at the second data storage unit may be processed, on the stationary side, in a second set of processing circuitry.

FIG.14schematically shows a non-limiting example of a CT imaging system100according to an embodiment. InFIG.14, the CT imaging system100comprises an X-ray detector114, a data storage unit116and processing circuitry118arranged on the rotating side of the CT imaging system100, e.g. on a rotating member of a gantry. Here, at least part of the generated detector data from the X-ray detector114is pre-processed by pre-processing circuitry115before being stored on the data storage unit116and/or before being processed by the processing circuitry118. The processing circuitry118may comprise a logic box118-1and/or a processing box118-2, wherein the processing box118-2may be configured to performer higher complexity computations compared to the logic box118-1. The processing circuitry118may process at least part of the detector data on the data storage unit116, and a data collector119may collect data, processed or non-processed, from all channels or a subset thereof and send it to the data communication system130which may then transfer the data from the rotating member of the gantry, to a stationary member of the gantry, arranged on the stationary side of the CT imaging system100. By way of example, a selected subset of the generated detector data from the X-ray detector114may be pre-processed by the pre-processing circuitry115before storage on the data storage unit116and/or before main processing by the processing circuitry118. In a particular example, the same subset of detector data or an at least partially different or completely different subset of detector data may be processed by the processing circuitry118.

FIG.15schematically shows another non-limiting example of a CT imaging system100according to an embodiment. InFIG.15, the CT imaging system100comprises an X-ray detector114, a data storage unit116and processing circuitry118arranged on the rotating side of the CT imaging system100, e.g. on a rotating member of a gantry. Here, the generated detector data from the X-ray detector114is stored on the data storage unit116and/or processed by the processing circuitry118without being pre-processed. The processing circuitry118may comprise a logic box118-1and/or a processing box118-2, wherein the processing box118-2may be configured to performer higher complexity computations compared to the logic box118-1. The processing circuitry118may process at least part of the detector data on the data storage unit116, and a data collector119may collect data, processed or non-processed, from all channels or a subset thereof and send it to the data communication system130which may then transfer the data from the rotating member of the gantry, to a stationary member of the gantry, arranged on the stationary side of the CT imaging system100. This embodiment has certain technical advantages, as previously discussed. Effects and features of the second aspect are largely analogous to those described above in connection with the first aspect. Embodiments mentioned in relation to the first aspect are largely compatible with the second aspect. It is further noted that the inventive concepts relate to all possible combinations of features unless explicitly stated otherwise.