The side of the gap-filling material with reduced dynamic misalignment sensitivity faces the X-ray detector.

Abstract

The present invention provides a side-facing X-ray detector (20) configured for detecting incoming X-rays. The side-facing X-ray detector (20) includes a plurality of adjacent X-ray sensors (21), each X-ray sensor (21) being oriented sideways toward the incoming X-rays. The X-ray sensors (21) are arranged side-by-side and / or sequentially, and the gaps between the X-ray sensors (21) are at least partially filled with a gap-filling material (26), the gap-filling material comprising a mixture or composite of resin and metal disulfide.

Description

Technical Field

[0001] The proposed technology relates to X-ray imaging, and more specifically, to X-ray detectors and X-ray imaging systems. Background Technology

[0002] Radiographic imaging (such as X-ray imaging) has been used for non-destructive testing in medical applications for many years.

[0003] Typically, an X-ray imaging system consists of an X-ray source and an X-ray detector system. The X-ray source emits X-rays, which pass through the object or structure to be imaged and are then recorded by the X-ray detector system. Because some materials absorb a larger portion of the X-rays than others, an image of the object or structure is formed.

[0004] To improve absorption efficiency, the X-ray detector can be arranged with its side facing the incoming or incident X-rays. In this case, the absorption depth can be selected to any length, and the detector can still be completely depleted without reaching very high voltages.

[0005] Therefore, side-facing is a special design in which the X-ray sensor is oriented sideways to the incoming X-rays. By design, this type of detector can have X-ray sensor and / or detector elements with a so-called high aspect ratio, which is the relatively high ratio between the length (or depth) of the X-ray sensor and / or detector element in the direction of the incident X-rays and the width of the X-ray sensor and / or detector element in the substantially vertical direction.

[0006] While side-facing X-ray detectors offer many advantages, a drawback of high aspect ratio X-ray sensors and / or their detector elements is their sensitivity to dynamic misalignment relative to the X-ray source focus. Dynamic misalignment is a technical reality that is not easily eliminated. The effects of dynamic misalignment can result in clinically unacceptable image artifacts and / or other image quality problems.

[0007] Therefore, a technical solution is needed to mitigate the effects of dynamic alignment in side-facing X-ray detectors. Summary of the Invention

[0008] The general object of the present invention is to provide improvements related to X-ray detectors and / or X-ray imaging systems.

[0009] For example, there is a desire for X-ray detectors to be more robust to dynamic misalignments, or for technical solutions that at least reduce sensitivity to such dynamic misalignments.

[0010] The specific object of the present invention is to provide a side-facing X-ray detector configured for detecting incoming X-rays.

[0011] Another object of the present invention is to provide an X-ray imaging system including such an X-ray detector.

[0012] These and other objectives can be achieved through one or more implementations of the proposed technology.

[0013] According to a first aspect, a side-facing X-ray detector configured for detecting incoming X-rays is provided. The side-facing X-ray detector includes a plurality of adjacent X-ray sensors, each oriented sideways to the incoming X-rays. The X-ray sensors are arranged side-by-side and / or sequentially ordered, and the gaps between the X-ray sensors are at least partially filled with a gap-filling material comprising a mixture or compound of resin and metal disulfide.

[0014] For example, while various metal disulfides can be used, it has been shown that tungsten disulfide is a favorable choice for interstitial filling mixtures or composites. For instance, resins can be mixed with tungsten disulfide powder.

[0015] In this way, side-facing X-ray detectors become more robust to dynamic misalignment. In particular, so-called high aspect ratio X-ray sensor and / or detector elements may be less sensitive to dynamic misalignment relative to the X-ray source focus. This, in turn, can lead to improved image quality. Specifically, it may more or less eliminate some image artifacts, for example, in clinical computed tomography (CT) applications.

[0016] According to the second aspect, an X-ray imaging system including such a side facing the X-ray detector is provided.

[0017] Slightly different in expression, according to the third aspect, the proposed technology provides a side-facing X-ray detector configured to detect incoming X-rays, the X-ray detector comprising a plurality of adjacent X-ray detector sub-modules, wherein each X-ray detector sub-module is oriented sideways toward the incoming X-rays. The X-ray detector sub-modules are arranged side-by-side and / or sequentially ordered, and the gaps between the X-ray detector sub-modules are at least partially filled with a material comprising metal disulfides mixed into a synthetic resin or organic resin or composite.

[0018] Other advantages will be understood when reading the detailed implementation. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating an example of an overall X-ray imaging system.

[0020] Figure 2 This is a schematic diagram illustrating another example of an X-ray imaging system.

[0021] Figure 3 This is a schematic block diagram of a CT system as an illustrative example of an X-ray imaging system.

[0022] Figure 4 This is a schematic diagram illustrating an example of a conceptual structure for implementing an energy-discriminative photon counting detector.

[0023] Figure 5 This is a schematic diagram illustrating an example of a semiconductor detector submodule according to an exemplary embodiment.

[0024] Figure 6 This is a schematic diagram illustrating an example of a semiconductor detector submodule according to another exemplary embodiment.

[0025] Figure 7 This is a schematic diagram illustrating an example of an X-ray detector that includes a set of tiled X-ray sensor or detector submodules.

[0026] Figure 8 This is a schematic diagram illustrating an example of focal misalignment of the central axis of an X-ray sensor and / or detector element relative to the associated X-ray source.

[0027] Figure 9 This is a schematic graph illustrating an example of how more photons will interact in a misaligned X-ray sensor and / or detector element compared to the non-misaligned case.

[0028] Figure 10 This is a schematic graph showing an example of the relative difference as a function of energy, illustrating the shift of the spectrum of interacting photons toward the lower energy side.

[0029] Figure 11 This is a schematic perspective view illustrating an example of an X-ray detector comprising a group of adjacent X-ray sensors arranged side-by-side and / or sequentially ordered.

[0030] Figure 12 This is a cross-sectional schematic diagram illustrating an example of an X-ray detector comprising a set of adjacent X-ray sensors arranged side-by-side and / or sequentially ordered.

[0031] Figure 13 This is a schematic diagram illustrating an example of an X-ray sensor, where a separate detector element may be defined by a charge collection electrode on the back side.

[0032] Figure 14A This is a schematic diagram illustrating an example of a specific implementation of a detector module based on two X-ray sensors.

[0033] Figure 14B It is shown by Figure 14AA schematic diagram illustrating a specific implementation of an X-ray detector constructed from several detector modules.

[0034] Figure 15A This is a planar schematic diagram illustrating an example of how a resin-based mixture or composite is applied to the surface of an X-ray sensor.

[0035] Figure 15B This is a cross-sectional schematic diagram illustrating an example of a detector module based on two X-ray sensors, with a scattering suppression foil arranged between the two X-ray sensors, and having a gap-filling material comprising a resin-based mixture or composite of the present invention.

[0036] Figure 16 This is a schematic plan view illustrating another example of how a resin-based mixture or compound is applied to the surface of an X-ray sensor.

[0037] Figure 17 This is a schematic graph illustrating an example of the relative difference as a function of energy in the case of misalignment when only epoxy resin adhesive is used in the gap between X-ray sensors.

[0038] Figure 18 This is a schematic graph illustrating a first example of the relative difference as a function of energy in the case of misalignment when using a material comprising a mixture or composite of epoxy resin and tungsten disulfide in the gap between X-ray sensors.

[0039] Figure 19 This is a schematic graph illustrating a second example of the relative difference as a function of energy in the case of misalignment when using a material comprising a mixture or composite of epoxy resin and tungsten disulfide in the gap between X-ray sensors.

[0040] Figure 20 This is a schematic diagram illustrating an example of a computer implementation according to an embodiment. Detailed Implementation

[0041] refer to Figure 1 It may be helpful to first provide a brief, illustrative overview of the overall X-ray imaging system. In this non-limiting example, the X-ray imaging system 100 essentially includes an X-ray source 10, an X-ray detector system 20, and an associated image processing device 30. Generally, the X-ray detector system 20 is configured to record radiation from the X-ray source 10, which may have been focused by optional X-ray optics and has passed through an object, or part thereof. The X-ray detector system 20 may be connected to the image processing device 30 via suitable analog processing and readout electronics (which may be integrated into the X-ray detector system 20) to enable the image processing device 30 to perform image processing and / or image reconstruction.

[0042] Figure 2 This is a schematic diagram illustrating an example of an X-ray imaging system 100, which includes: an X-ray source 10 that emits X-rays; an X-ray detector system 20 that detects X-rays after they have passed through an object; an analog processing circuit system 25 that processes and digitizes the raw electrical signals from the detector; a digital processing circuit system 40 that can perform further processing operations on the measurement data, such as applying corrections, temporary storage, or filtering; and a computer 50 that stores the processed data and can perform further post-processing and / or image reconstruction.

[0043] The overall detector can be considered as X-ray detector system 20, or a combination of X-ray detector system 20 and associated analog processing circuitry system 25.

[0044] The digital portion, including the digital processing circuitry system 40 and / or the computer 50, can be considered as the digital image processing system 30, which performs image reconstruction based on image data from an X-ray detector. Therefore, the image processing system 30 can be viewed as the computer 50, or alternatively, a combination of the digital processing circuitry system 40 and the computer 50, or, if the digital processing circuitry system 40 is further specifically used for image processing and / or reconstruction, it may be viewed as the digital processing circuitry system itself.

[0045] A common example of an X-ray imaging system is a computed tomography (CT) system, which may include an X-ray source that generates a fan-shaped or cone-shaped beam of X-rays and a corresponding X-ray detector system for recording the fraction of X-rays that travel through the patient or object. The X-ray source and detector system are typically mounted in a gantry that rotates around the object being imaged.

[0046] therefore, Figure 1 and Figure 2 The X-ray source 10 and X-ray detector system 20 shown can therefore be arranged as part of a CT system, for example, they can be installed in a CT gantry.

[0047] Figure 3This is a schematic block diagram of a CT system as an illustrative example of an X-ray imaging system. The CT system includes a computer 50 that receives commands and scan parameters from an operator via an operator console 60, which may have a display and some form of operator interface, such as a keyboard and mouse. The commands and parameters provided by the operator are then used by the computer 50 to provide control signals to an X-ray controller 41, a gantry controller 42, and an examination table controller 43. Specifically, the X-ray controller 41 provides power and timing signals to the X-ray source 10 to control the emission of X-rays onto an object or patient located on the examination table 12. The gantry controller 42 controls the rotational speed and position of the gantry 11, which includes the X-ray source 10 and the X-ray detector 20. The examination table controller 43 controls and determines the position of the patient examination table 12 and the patient's scan coverage. A detector controller 44 is also present, configured to control and / or receive data from the detector 20.

[0048] In one implementation, computer 50 also performs post-processing and image reconstruction on the image data output from the X-ray detector. Therefore, the computer corresponds to, for example... Figure 1 and Figure 2 The image processing system 30 shown. The associated display allows the operator to view the reconstructed images and other data from the computer.

[0049] An X-ray source 10, arranged in a gantry 11, emits X-rays. An X-ray detector 20 (e.g., in the form of a side-facing X-ray detector) detects these X-rays after they have passed through the patient. The X-ray detector 20 may, for example, have multiple pixels (also referred to as sensor or detector elements) and an associated processing circuitry system (such as an ASIC) arranged in the detector module. At least a portion of the analog processing portion may be implemented in the pixels, while any remaining processing portion may be implemented, for example, in the ASIC. In one embodiment, the processing circuitry system (ASIC) digitizes the analog signals from these pixels. The processing circuitry system (ASIC) may also include a digital processing portion that can perform further processing operations on the measurement data, such as applying corrections, temporary storage, and / or filtering. During the scan to acquire X-ray projection data, the gantry and the components mounted thereon rotate about an isocenter.

[0050] The challenge of X-ray imaging detectors is to extract the maximum information from the detected X-rays to provide input for an image of an object or structure, which is depicted based on its density, composition, and structure. While using film-type screens as detectors remains common, it is now most prevalent to have detectors that provide digital images.

[0051] Modern X-ray detectors typically require the conversion of incident X-rays into electrons, usually through light absorption or Compton interactions. The resulting electrons typically produce secondary visible light until their energy is lost and this light is subsequently detected by a photosensitive material. Semiconductor-based detectors also exist, in which electrons generated by X-rays acquire an electric charge based on electron-hole pairs collected by an applied electric field.

[0052] Conventional X-ray detectors are energy integrals, so the contribution from each detected photon to the detection signal is proportional to its energy, and in conventional CT, measurements are acquired for a single energy distribution. Therefore, images produced by conventional CT systems have a certain appearance, with different tissues and materials displaying typical values ​​within a certain range.

[0053] There are detectors that operate in integration mode, in which they provide an integrated signal from multiple X-rays, and this signal is only digitized later to retrieve the best guess at the number of incident X-rays in a pixel.

[0054] However, in some applications, photon counting detectors have become a viable alternative; currently, these detectors are primarily commercially available in mammography. Photon counting detectors have advantages because, in principle, they can measure the energy of each X-ray, which produces additional information about the composition of the object. This information can be used to improve image quality and / or reduce radiation dose.

[0055] Further improvements involve the development of so-called energy-discriminate photon counting detectors, such as... Figure 4 The diagram illustrates this. In this type of X-ray detector, each recorded photon generates a current pulse, which is compared to a set of thresholds to count the number of photons incident on each of several so-called energy chambers. This can be very useful in image reconstruction. Sometimes, energy-discriminatory photon counting detectors are referred to as multi-chamber detectors.

[0056] Generally speaking, energy information allows for the creation of new types of images where new information is available and image artifacts inherent in conventional techniques can be removed.

[0057] In other words, for an energy discrimination detector, the pulse height is compared with multiple programmable thresholds in a comparator, and the pulse height is classified according to the pulse height, which is then proportional to the energy.

[0058] However, an inherent problem with any (charge-sensitive) amplifier is that it adds electronic noise to the detected current. To avoid detecting noise instead of real X-ray photons, it is important to set the minimum threshold (Thr) high enough that the number of times the noise value exceeds the threshold is low enough not to interfere with the detection of X-ray photons.

[0059] By setting the minimum threshold above the noise floor, electronic noise, a major obstacle to reducing radiation dose in X-ray imaging systems, can be significantly reduced.

[0060] A general characteristic of (shaping) filters is that a large shaping time value results in long pulses of X-ray photons and reduces the noise amplitude after the filter. A small shaping time value results in shorter pulses and larger noise amplitudes. Therefore, in order to count as many X-ray photons as possible, a large shaping time is needed to minimize noise and allow for the use of a relatively small threshold level.

[0061] As mentioned earlier, in order to improve absorption efficiency, the X-ray detector can be set to face sideways. In this case, the absorption depth can be selected to any length, and the detector can still be completely depleted without reaching very high voltage.

[0062] Therefore, side orientation is a special design in which the X-ray sensor is oriented to face the incoming X-rays from the side.

[0063] For example, such a side-facing X-ray detector may have pixels or detector elements in at least two directions, wherein one of the directions of the side-facing detector has a component in the direction of the X-ray. Such a side-facing X-ray detector is sometimes referred to as a depth-segmented X-ray detector, which has two or more depth segments of detector elements in the direction of the incoming X-ray.

[0064] Alternatively, the detector elements can be arranged in an array (non-depth segmented) in a direction substantially perpendicular to the incident X-rays, and each detector element can be oriented laterally toward the incident X-rays. In other words, the X-ray detector can be non-depth segmented while still being arranged laterally toward the incoming X-rays.

[0065] Figure 5 This is a schematic diagram illustrating an example of an X-ray sensor 21 with its side facing outwards according to an exemplary embodiment, also referred to as a detector module or submodule. This is an example of an X-ray sensor 21 or detector submodule where the sensor portion is divided into detector elements or pixels, each of which is typically based on a diode with a charge collection electrode as a key component. X-rays enter through the edge of the X-ray sensor.

[0066] Figure 6 This is a schematic diagram illustrating an example of a side-facing X-ray sensor 21 or detector submodule according to another exemplary embodiment. In this example, it is again assumed that the X-rays enter through the edge, and the sensor portion is further divided into so-called depth segments in the depth direction.

[0067] Typically, a detector element is a single X-ray sensitive element of the detector. Generally, photon interactions occur within the detector element, and the resulting charge is collected by the corresponding electrodes of the detector element.

[0068] Each detector element typically measures the incident X-ray flux as a sequence of frames. A frame is data measured during a specified time interval (called the frame time).

[0069] Depending on the detector topology, detector elements may correspond to pixels, especially when the detector is a flat panel detector. A depth segmented detector can be viewed as having multiple detector strips, each strip having multiple depth segments. For such a depth segmented detector, each depth segment can also be viewed as a separate detector element, especially if each depth segment is associated with its own separate charge collection electrode.

[0070] The detector stripes of a depth segment detector typically correspond to the pixels of a regular flat panel detector, and are therefore sometimes referred to as pixel stripes. However, a depth segment detector can also be viewed as a three-dimensional pixel array, where each pixel (sometimes called a voxel) corresponds to a separate depth segment / detector element.

[0071] For example, a sensor can be implemented as a so-called multi-chip module (MCM), in which the semiconductor sensor serves as the bottom substrate for electrical wiring and multiple application-specific integrated circuits (ASICs), which are preferably attached via so-called flip-chip technology. The wiring will include signal connections 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. Given the increased cross-sectional area required for the large currents in these connections, power can be supplied to the ASIC via similar wiring, but it can also be supplied via separate connections.

[0072] Figure 7 This is a schematic diagram illustrating an example of an X-ray detector 20 comprising a set of tiled X-ray sensors 21 (also referred to as X-ray detector submodules), wherein each X-ray sensor or detector submodule 21 is a depth-segmented side facing the X-ray sensor or detector submodule, and an ASIC or corresponding circuitry 24 is arranged below the detector element 22 as viewed from the direction of the incoming X-ray, thereby allowing a wiring path 23 to exist from the detector element 22 to the ASIC 24 in the space between the detector elements.

[0073] As previously mentioned, a disadvantage of high aspect ratio detector elements (such as side-facing X-ray detectors) is their sensitivity to dynamic misalignment relative to the X-ray source focus. Dynamic misalignment is a technical reality that is not easily eliminated. The effects of dynamic misalignment can result in clinically unacceptable image artifacts and / or other image quality problems.

[0074] Therefore, a technical solution is needed to mitigate the effects of dynamic alignment in side-facing X-ray detectors.

[0075] To better understand, an illustrative problem scenario will be discussed in more detail below.

[0076] For example, a photon-counting multi-compartment detector has the ability to divide a broad spectrum of incident photons into several compartments based on its deposition energy. This is typically achieved through a pulse height comparator (e.g., see again). Figure 3 This is accomplished by a pulse height comparator acting on an analog signal whose amplitude is proportional to the charge released by the X-rays in the detector's semiconductor material.

[0077] The benefits of using photon-counting multi-compartment detectors in computed tomography applications include the elimination of beam-hardening artifacts, material quantization, and the possibility of generating images with improved contrast-to-noise ratios by producing synthetic monoenergetic images. These benefits are typically achieved through material-based decomposition. Material-based decomposition is usually performed in the projection domain, i.e., by applying the raw photon counts to each individual projection. In short, the goal of this decomposition is to use the counts in each projection and estimate the corresponding path lengths for a set of underlying materials. These path length estimates are later used for image reconstruction.

[0078] A prerequisite for performing a material-based decomposition is an accurate understanding of the system. This knowledge is typically captured in the forward model, which describes the expected response (counts in each bin) for all feasible combinations of basic material path lengths. Material-based decomposition is equivalent to inverting the forward model using a noisy X-ray realization (counts detected in the bins) and the estimated corresponding path lengths. One feasible approach is to use the maximum likelihood method.

[0079] The larger the aspect ratio of a single detector element, that is, the greater the ratio of its length in the direction of incident X-rays to its length in the vertical direction, the more sensitive the detector is to dynamic misalignment of the detector element and the focal source.

[0080] Dynamic misalignment refers to the displacement of the central axis of the X-ray sensor and / or detector element relative to the focal source, as referenced. Figure 8Such movement has many sources, including thermal expansion, rotational forces, and focus displacement, which will be detailed below. It is important that the potential effects of such movement have already been commented on here; if severe, it can invalidate the forward model. For example, if the calibration data for an X-ray sensor and / or detector element was obtained with the sensor axis pointing towards the focus, the determined forward model will only be accurate for that alignment. If misalignment causes X-rays to enter an X-ray sensor and / or detector element with a large aspect ratio at an angle, the number of interacting photons and their deposited energy may differ because the attenuation length through the active detector material varies greatly for X-rays striking the X-ray sensor and / or detector element at an angled edge. While X-rays also strike misaligned X-ray sensor and / or detector elements with a small aspect ratio at angled edges, the fraction of X-rays striking the edge increases with increasing aspect ratio, according to... Figure 8 It is obvious. If the difference in the number of interacting photons and their energies is large enough, the forward model determined during proper alignment will not be accurate enough to perform a material-based decomposition without bias.

[0081] The Beer-Lambert law, describing exponential transmission, provides a more thorough understanding of why the energies of interacting photons differ in these two cases. Even the volume of the irradiated X-ray sensor and / or detector element (refer to...) Figure 8 The path length does not change with the misalignment angle. A larger portion of the X-ray sensor and / or detector elements will generate counts only from the X-rays traversing a short distance, and therefore more low-energy photons will interact compared to the case without misalignment. Similarly, in the case of misalignment, the portion of the X-rays traversing the distance corresponding to the full detector length is smaller, and this will result in relatively fewer high-energy photon interactions. This effect can be quite significant, as illustrated by simulations, the results of which can be found in… Figure 9 As seen in the image, the simulation parameters, though intended for illustrative purposes only and not for limitation, are based on a silicon strip detector with a width of 650µm and a height of 37mm, producing an aspect ratio of 57. The misalignment corresponds to an exaggerated tilt angle of 0.115°. Clearly, the spectrum of interacting photons is altered, and a total of 3.2% more photons interact in the misaligned X-ray sensor (dashed line) and / or detector elements compared to the non-misaligned case (solid line).

[0082] exist Figure 10 The graph depicts the relative difference as a function of energy. This indicates that the spectrum of interacting photons has shifted towards the lower energy side.

[0083] So far, we have shown that, for example, if the focus shifts during the time between calibration and image acquisition, dynamic misalignment can lead to biased material path length estimates. If all individual X-ray sensor and / or detector elements are identical, they will respond to dynamic misalignment in the same way, i.e., with the same bias. However, there is also unavoidable static misalignment of X-ray sensor and / or detector elements, stemming from inaccuracies, such as those during installation. Due to the nonlinear nature of X-ray attenuation, two statically misaligned X-ray sensor and / or detector elements will respond differently to the same dynamic misalignment. This leads to the conclusion that the resulting bias in the basic material path length will differ. In third-generation CT, such differences, if large enough, can generate ring artifacts during reconstruction, which are clinically intolerable in patient images.

[0084] Therefore, dynamic misalignment is a real image quality problem, and its effects are exacerbated for systems using X-ray sensor and / or detector elements with large aspect ratios. Furthermore, the sources of dynamic misalignment are not easily eliminated. For example, while it is predictable and therefore calibrable that the detector carriage may bend during rotation, calibrating the system for all possible rotational speeds is extremely time-consuming in practice. Similarly, even though thermal expansion (from the heat generated by the detector module during scanning) is expected to be predictable with temperature, calibration at all possible detector temperatures (depending on the ambient environment and scan duration) is impractical. Finally, despite efforts to minimize dynamic focus motion, it is a technical reality in all X-ray tubes with rotating anodes used in clinical practice.

[0085] This more detailed description of the problem indicates that dynamic misalignment is a technical reality that is not easily eliminated. The effects of dynamic misalignment can be clinically unacceptable image artifacts, especially for photon-counting multi-compartment detectors with high aspect ratios used in CT applications.

[0086] The general object of the present invention is to provide improvements related to X-ray detectors and / or X-ray imaging systems.

[0087] For example, there is a desire for X-ray detectors to be more robust to dynamic misalignments, or for technical solutions that at least reduce sensitivity to such dynamic misalignments.

[0088] The specific object of the present invention is to provide a side-facing X-ray detector configured for detecting incoming X-rays.

[0089] Another object of the present invention is to provide an X-ray imaging system including such an X-ray detector.

[0090] These and other objectives can be achieved through one or more implementations of the proposed technology.

[0091] According to a first aspect, a side-facing X-ray detector configured for detecting incoming X-rays is provided. The side-facing X-ray detector includes a plurality of adjacent X-ray sensors, each oriented sideways to the incoming X-rays. The X-ray sensors are arranged side-by-side and / or sequentially ordered, and the gaps between the X-ray sensors are at least partially filled with a gap-filling material comprising a mixture or compound of resin and metal disulfide.

[0092] Figure 11 This is a schematic perspective view showing an example of an X-ray detector 20 comprising a group of adjacent X-ray sensors 21 arranged side-by-side and / or sequentially ordered. As can be seen, the X-ray sensors are oriented sideways toward the incoming X-rays.

[0093] Figure 12 This is a schematic cross-sectional view of an example of an X-ray detector 20 comprising a set of adjacent X-ray sensors 21 arranged side by side and / or sequentially ordered, wherein each X-ray sensor is oriented with its side facing the incoming X-rays. Figure 12 The cross-sectional view also shows the manner in which the gaps are at least partially filled with gap / filler material 26. The material 26 comprises a mixture or compound of resin and metal disulfide.

[0094] Figure 13 This is a schematic diagram illustrating an example of an X-ray sensor, where a separate detector element may be defined by a charge collection electrode on the back side.

[0095] Typically, it is desirable for the X-ray sensors 21 to be close to each other to maximize the active detector area / volume and thus dose efficiency, but at the same time, they should not be in direct physical contact with each other due to the significant risk of short circuits. From a manufacturing perspective, and because of the high aspect ratio of the X-ray sensors 21 and / or their detector elements, some lateral support and gaps and / or filler material are required between the X-ray sensors 21, for example, to ensure a rigid structure and proper function. This gap and / or filler material can be, for example, based on resin (such as glue or another adhesive, or generally, any organic or synthetic resin), which facilitates its automatic dispensing by industrial robots as part of the manufacturing process, thus allowing for assembly-line production.

[0096] The parasitic capacitance between X-ray sensor and / or detector elements affects the electronic noise level and thus the detector performance. This parasitic capacitance is inversely proportional to the distance separating the two X-ray sensors and also depends on the dielectric constant of the materials separating them. Therefore, from a dose efficiency perspective, it is desirable for the X-ray sensors to be as close as possible, but from a noise perspective, it is desirable for the X-ray sensors to be further apart to maintain parasitic capacitance and thus minimize noise.

[0097] This is beneficial for gap-filling materials that possess X-ray attenuation properties. For example, if it is desirable for them to provide mixtures or composites that mimic silicon attenuation, especially if silicon-based X-ray sensors are used.

[0098] More generally, the present invention proposes to incorporate X-ray attenuating metal disulfides (e.g., in powder form) into the resin to reduce sensitivity to dynamic misalignment.

[0099] In other words, the inventors have discovered that incorporating metal disulfides into resins provides a technical solution that supports the useful properties and characteristics mentioned above, which will be further elaborated later.

[0100] In this way, side-facing X-ray detectors become more robust to dynamic misalignment. In particular, so-called high aspect ratio X-ray sensor and / or detector elements may be less sensitive to dynamic misalignment relative to the X-ray source focus. This, in turn, can lead to improved image quality. Specifically, it may more or less eliminate some image artifacts, for example, in clinical CT applications.

[0101] The difference lies in the way it's expressed: the assembly process causes some variation in the sensor-to-sensor and sensor-to-sheet distances (in the z-direction). If a standard adhesive (like epoxy resin with a low average atomic number) is used, the X-ray attenuation of the gaps filled with adhesive in the assembly will be very low. This will make the design highly sensitive to dynamic focus shifts (in the z-direction), as different sensors will react very differently. The spectral changes caused by focus shift will result in ring artifacts. By using an adhesive or resin mixture obtained by mixing tungsten disulfide (or any other metal powder with a high atomic number) at a certain concentration into the adhesive or resin, making the adhesive gaps appear as similar to silicon as possible, the sensitivity to artifacts will be significantly reduced.

[0102] Figure 14AThis is a schematic diagram illustrating an example of a detector module based on two X-ray sensors. In this example, X-ray sensors 21 are arranged side by side, with a scattering suppression foil or plate 27 located between the X-ray sensors. The gap between the X-ray sensors 21 is also at least partially filled with a material 26 based on a mixture or composite of resin and metal disulfide, i.e., a so-called resin-based mixture.

[0103] Figure 14B It is shown by Figure 14A This is a schematic diagram illustrating an example of a specific implementation of an X-ray detector constructed from several detector modules. Here, it can be seen that the gaps between the detector modules are also at least partially filled with a resin-based mixture 26. It can also be seen that the X-ray sensor 21 (and the overall X-ray detector assembly or X-ray detector) is oriented laterally toward the incident X-rays, thus defining the lateral X-ray detector 20.

[0104] For example, while various metal disulfides can be used, tungsten disulfide has been shown to be a favorable choice for interstitial filling mixtures or composites. For instance, resins can be mixed with tungsten disulfide powder. Tungsten disulfide is an inorganic compound composed of tungsten and sulfur, with the chemical formula WS2 or WS2.

[0105] In specific examples, the product of the fill factor of the mixture and the weight fraction of tungsten disulfide in the mixture ranges from 5% to 15%.

[0106] Ideally, the product of the filling factor of the mixture and the weight fraction of tungsten disulfide in the mixture should be between 6% and 12%.

[0107] In a further specific example, it has been shown that truly satisfactory performance can be achieved when the product of the fill factor of the mixture and the weight fraction of tungsten disulfide in the mixture is in the range of 8% to 10%.

[0108] For example, the filling factor of a mixture can be defined as the fraction of the gap space between X-ray sensors occupied by the mixture.

[0109] For example, the resin can be an organic resin or a synthetic resin.

[0110] In certain examples, the resin may have adhesive properties, such as in the form of adhesives and / or glues.

[0111] For example, the resin may include adhesives based on epoxy resins, acrylates, silicones, polyvinyl acetate and / or urethane or polyurethane.

[0112] Optionally, the X-ray detector may further include a scattering suppression foil or plate disposed between at least a portion of the X-ray sensor.

[0113] For example, these scattering suppression foils or plates can be made of tungsten.

[0114] For example, an X-ray sensor may be side-facing and each component may have multiple detector elements, such as... Figures 5 to 7 As shown.

[0115] In a specific example, each side of the X-ray sensor is based on a silicon wafer with multiple detector electrodes.

[0116] As illustrated schematically, assuming the X-rays enter through the edge, each side facing the X-ray sensor may include a detector element extending in the depth direction of the side facing the X-ray sensor.

[0117] In a specific example, each side facing the X-ray sensor is a depth-segmented X-ray sensor, which has two or more detector element depth segments in the direction of the incoming X-rays, see, for example, [reference needed]. Figure 6 or Figure 7 .

[0118] For example, X-ray sensors may be arranged side by side and / or sequentially in a direction substantially perpendicular to the direction of incoming X-rays, and / or arranged in a slightly curved overall configuration relative to the X-ray focus of the associated X-ray source.

[0119] For example, the X-ray sensor may be a planar module, and for at least a portion of the X-ray sensor, the X-ray sensor may be arranged side by side in the so-called in-plane direction and / or in a direction transverse to the in-plane direction.

[0120] In a specific example, the side-facing X-ray detector can be a photon-counting X-ray detector, such as a photon-counting multi-compartment X-ray detector.

[0121] So-called resin-based mixtures or complexes having metal disulfides mixed with resin can be applied to the surface of an X-ray sensor in many different ways, for example, by being applied in a series or in a point pattern to at least one subset of adjacent X-ray sensors.

[0122] Figure 15AThis is a planar schematic diagram illustrating an example of how a resin-based mixture or composite is applied to the surface of an X-ray sensor. In this example, a resin-based mixture 26 having a metal disulfide is applied in strings to the planar surface of an X-ray sensor substrate. Optionally, an additional adhesive 28 may be applied, preferably in dots, to lock and / or reinforce the connection and rigidity between adjacent X-ray sensors. This optional adhesive 28 may, for example, be a UV- and / or thermosetting adhesive.

[0123] Figure 15B This is a cross-sectional schematic diagram illustrating an example of a detector module based on two X-ray sensors, with a scattering suppression foil arranged between the two X-ray sensors, and having a gap-filling material comprising a resin-based mixture or composite of the present invention.

[0124] Figure 16 This is a schematic plan view illustrating another example of how a resin-based mixture or compound is applied to the surface of an X-ray sensor.

[0125] As previously mentioned, the parasitic capacitance between X-ray sensor and / or detector elements affects the electronic noise level and thus the detector performance. This parasitic capacitance is inversely proportional to the distance separating the two X-ray sensors and also depends on the dielectric constant of the materials separating them. Therefore, from a dose efficiency perspective, it is desirable for the X-ray sensors to be as close as possible, but from a noise perspective, it is desirable for the X-ray sensors to be further apart to maintain parasitic capacitance and thus minimize noise.

[0126] Most resins and / or adhesives have relatively low average atomic numbers, and therefore, in terms of X-ray linear attenuation coefficients, are very similar to air. As described above, this results in sensitivity to dynamic misalignment between the detector element axis and the focal spot. This is in Figure 17 The diagram shows a simulation of a silicon strip detector with a large aspect ratio of 57. To make the simulation more realistic, dynamic misalignment corresponds to a dynamic focus movement of 0.2 mm. Assuming a source-to-detector distance of 1 m, this corresponds to a 0.0115°... Dynamic misalignment. In this example, the gap between the X-ray sensor and / or detector elements is assumed to be filled with cured epoxy resin. In summary, more than 0.14% of photons interact in the detector (compared to the non-misaligned case), and the ratio of photon energy is... Figure 17 As shown in the image. From Figure 17 It can be seen that, for example, a focus shift of 0.2 mm will result in more than 2000 ppm of photons interacting in the detector in the energy range of 60 keV-70 keV, and the difference is greater at lower energies.

[0127] The numbers 2000 ppm and 0.14% may seem small, but for detectors used in third-generation CT scans, this will unfortunately result in visible ring artifacts.

[0128] For example, it is desirable for CT detector components to be robust to dynamic misalignment.

[0129] As outlined above, the present invention proposes to incorporate X-ray attenuating metal disulfides (e.g., in powder form) into resins such as epoxy resin adhesives to reduce sensitivity to dynamic misalignment.

[0130] As a basis for discussing the details of the implementation, the metal powder and its concentration should preferably be selected to minimize the spectral sensitivity of the detector assembly to dynamic misalignment and to keep the parasitic capacitance between the X-ray sensor and / or detector elements to a minimum. Meanwhile, the desired properties of the resin (such as epoxy resin adhesive), namely non-particle size and viscosity that allows for its self-distribution, should preferably be maintained.

[0131] For example, mixing molybdenum disulfide into a resin may result in the desired X-ray attenuation properties, but due to molybdenum's relatively low atomic number, a high mass fraction is required. In some cases, mixing itself may become difficult, or the resin-powder mixture may become too viscous. This is particularly true if the gaps between the X-ray sensor and / or detector elements are not completely filled with the resin-based mixture or compound, for example, if the resin is distributed in line with a fill factor less than 1. In this case, the weight fraction of power must be correspondingly larger to produce similar attenuation. Using a fill factor less than 1 is expected to keep parasitic capacitance to a minimum. Furthermore, the resin-based mixture must be non-conductive, as this would cause short circuits in the detector elements. This makes the use of industrially available adhesives that become conductive by adding metal grains impractical.

[0132] It may be advantageous to use a metal disulfide, such as tungsten disulfide (WS2), instead of molybdenum disulfide. Choosing tungsten disulfide instead of molybdenum disulfide as a powder to be mixed into resins or adhesives overcomes the practical problem of obtaining bulky, non-sticky mixtures by allowing for a smaller weight fraction due to its higher atomic number. WS2 also has a low dielectric constant, keeping parasitic capacitance low and allowing for smaller X-ray sensor spacing.

[0133] However, the spectral sensitivity to dynamic misalignment is concentration-sensitive. For example, using the same simulation parameters as above, adding 13% WS2 to a resin such as epoxy resin resulted in a total count change of 500 ppm, and the energy distribution was similar to... Figure 18 .

[0134] If 9.5% by weight of WS2 is added to a resin such as epoxy resin, the total number of detected photons (excluding energy) differs by only 60 ppm when the misalignment is 0.0115° compared to the non-misaligned case. This effect is negligible. Figure 19 The results show that for the most significant X-ray energies in the 80keV-100keV spectrum, the difference resulting from a 0.0115° misalignment is on the order of several hundred parts per million (ppm). This is a tolerable level in third-generation CT and generally does not cause ring artifacts.

[0135] This suggests that, with careful consideration, the proposed method can make so-called high aspect ratio X-ray detectors more or less insensitive to dynamic misalignment.

[0136] According to the second aspect, an X-ray imaging system including such a side facing the X-ray detector is provided.

[0137] Slightly different in expression, according to the third aspect, the proposed technology provides a side-facing X-ray detector configured to detect incoming X-rays, the X-ray detector comprising a plurality of adjacent X-ray detector sub-modules, wherein each X-ray detector sub-module is oriented sideways toward the incoming X-rays. The X-ray detector sub-modules are arranged side-by-side and / or sequentially ordered, and the gaps between the X-ray detector sub-modules are at least partially filled with a material comprising metal disulfides mixed into a synthetic resin or organic resin or composite.

[0138] It should be understood that the methods and equipment described herein can be combined and rearranged in a variety of ways.

[0139] For example, a particular function may be implemented in hardware or in software for execution by a suitable processing circuitry system, or a combination thereof.

[0140] The steps, functions, processes, modules, and / or blocks described herein can be implemented in hardware using any conventional techniques, such as semiconductor technology, discrete circuitry, or integrated circuit technology, including general-purpose electronic circuits and application-specific circuits.

[0141] Specific examples include one or more appropriately configured digital signal processors and other known electronic circuits, such as discrete logic gates interconnected to perform specific functions, or application-specific integrated circuits (ASICs).

[0142] Alternatively, at least some of the steps, functions, processes, modules and / or blocks described herein may be implemented in software such as a computer program for execution by a suitable processing circuitry system such as one or more processors or processing units.

[0143] Examples of processing circuitry systems include, but are not limited to, one or more microprocessors, one or more digital signal processors (DSPs), one or more central processing units (CPUs), video acceleration hardware, and / or any suitable programmable logic circuitry, such as one or more field-programmable gate arrays (FPGAs) or one or more programmable logic controllers (PLCs).

[0144] It should also be understood that the general processing power of any conventional device or unit in which the proposed technology is implemented can be reused. Existing software can also be reused, for example, by reprogramming existing software or by adding new software components.

[0145] Figure 20 This is a schematic diagram illustrating an example of a computer implementation according to an embodiment. In this particular example, system 200 includes a processor 210 and a memory 220 containing instructions executable by the processor, thereby enabling the processor to perform the steps and / or actions described herein. These instructions are generally organized as computer programs 225, 235, which may be pre-configured in memory 220 or downloaded from external storage device 230. Optionally, system 200 includes an input / output interface 240 that may be interconnected to processor 210 and / or memory 220 to enable the input and / or output of relevant data, such as input parameters and / or resulting output parameters.

[0146] The term “processor” should be interpreted in a general sense as any system or device capable of executing program code or computer program instructions to perform specific processing, determination, or computational tasks.

[0147] Therefore, a processing circuit system including one or more processors is configured to perform well-defined processing tasks (such as those described herein) when executing a computer program.

[0148] The processing circuitry system is not limited to performing the steps, functions, processes and / or blocks described above, but can also perform other tasks.

[0149] The proposed technology also provides a computer program product including computer-readable media 220 and 230, on which such computer program is stored.

[0150] For example, software or computer programs 225, 235 may be implemented as computer program products typically carried or stored on computer-readable media 220, 230 (especially non-volatile media). Computer-readable media may include one or more removable or non-removable memory devices, including but not limited to: read-only memory (ROM), random access memory (RAM), compressed optical disc (CD), digital versatile optical disc (DVD), Blu-ray disc, universal serial bus (USB) storage, hard disk drive (HDD) storage devices, flash memory, magnetic tape, or any other conventional memory device. Therefore, a computer program may be loaded into the operational memory of a computer or equivalent processing device for execution by its processing circuitry.

[0151] A method flow, when executed by one or more processors, can be viewed as a computer action flow. A corresponding device, system, and / or apparatus can be defined as a set of functional modules, where each step executed by the processor corresponds to a functional module. In this case, the functional module is implemented as a computer program running on the processor. Therefore, the device, system, and / or apparatus can alternatively be defined as a set of functional modules, where these functional modules are implemented as computer programs running on at least one processor.

[0152] Computer programs residing in memory can therefore be organized into appropriate functional modules that are configured to perform at least a portion of the steps and / or tasks described herein when the computer program is run by a processor.

[0153] Alternatively, modules can be implemented primarily through hardware modules or alternatively through hardware. The degree of software relative to hardware is purely a matter of implementation choice.

[0154] The above embodiments are given as examples only, and it should be understood that the proposed technology is not limited thereto. Those skilled in the art will understand that various modifications, combinations, and changes can be made to these embodiments without departing from the scope of the invention as defined by the appended claims. In particular, where technically possible, different portions of solutions from different embodiments can be combined in other configurations.

Claims

1. A side-facing X-ray detector (20) configured to detect incoming X-rays, wherein the side-facing X-ray detector (20) comprises a plurality of adjacent X-ray sensors (21), wherein each X-ray sensor (21) is oriented sideways to the incoming X-rays. The X-ray sensors (21) are arranged side by side and / or sequentially arranged, and the gaps between the X-ray sensors (21) are at least partially filled with a gap-filling material (26), which includes a mixture or composite of resin and metal disulfide.

2. The side-facing X-ray detector (20) according to claim 1, wherein the metal disulfide is tungsten disulfide.

3. The side-facing X-ray detector (20) according to claim 1 or 2, wherein the resin is mixed with tungsten disulfide powder.

4. The side-facing X-ray detector (20) according to claim 2, wherein the product of the filling factor of the mixture and the weight fraction of tungsten disulfide in the mixture is in the range of 5% to 15%.

5. The side-facing X-ray detector (20) according to claim 4, wherein the product of the filling factor of the mixture and the weight fraction of tungsten disulfide in the mixture is in the range of 6% to 12%.

6. The side-facing X-ray detector (20) according to claim 4, wherein the product of the filling factor of the mixture and the weight fraction of tungsten disulfide in the mixture is in the range of 8% to 10%.

7. The side-facing X-ray detector (20) according to claim 4, wherein the filling factor of the mixture is defined as the fraction of the gap between the X-ray sensors occupied by the mixture.

8. The side-facing X-ray detector (20) according to claim 1, wherein the resin is an organic resin or a synthetic resin.

9. The side-facing X-ray detector (20) according to claim 1, wherein the resin has adhesive properties.

10. The side-facing X-ray detector (20) according to claim 1, wherein the resin comprises an adhesive based on epoxy resin, acrylate, silicone, polyvinyl acetate and / or urethane or polyurethane.

11. The side-facing X-ray detector (20) according to claim 1, wherein the X-ray detector (20) further comprises a scattering suppression foil or plate (27) disposed between at least a portion of the X-ray sensor.

12. The side-facing X-ray detector (20) according to claim 11, wherein the scattering suppression foil or plate (27) is made of tungsten.

13. The side-facing X-ray detector (20) according to claim 1, wherein the X-ray sensor (21) is a side-facing X-ray sensor, each having a plurality of detector elements.

14. The side-facing X-ray detector (20) according to claim 13, wherein each side-facing X-ray sensor is based on a silicon wafer having a plurality of detector electrodes.

15. The side-facing X-ray detector (20) according to claim 13 or 14, wherein it is assumed that the X-rays enter through the edge, and each side-facing X-ray sensor includes a detector element extending in the depth direction of the side-facing X-ray sensor.

16. The side-facing X-ray detector (20) according to claim 13, wherein each side-facing X-ray sensor is a depth segmented X-ray sensor having two or more detector element depth segments in the direction of the incoming X-ray.

17. The side-facing X-ray detector (20) according to claim 1, wherein the X-ray sensors (21) are arranged side by side and / or sequentially in a direction substantially perpendicular to the direction of the incoming X-rays, and / or arranged in a slightly curved overall configuration relative to the X-ray focus of the associated X-ray source.

18. The side-facing X-ray detector (20) according to claim 1, wherein the X-ray sensor (21) is a planar module, and for at least a portion of the X-ray sensor, the X-ray sensor (21) is arranged side-by-side in the in-plane direction of the X-ray sensor and / or in a direction transverse to the in-plane direction of the X-ray sensor.

19. The side-facing X-ray detector (20) according to claim 1, wherein the side-facing X-ray detector (20) is a photon-counting X-ray detector.

20. The side-facing X-ray detector (20) according to claim 1, wherein the gap-filling material (26) comprising a mixture of resin and metal disulfide is applied in a series or in a point pattern to at least a subset of adjacent X-ray sensors.

21. An X-ray imaging system (100) comprising a side-facing X-ray detector (20) according to any one of claims 1 to 20.

22. A side-facing X-ray detector (20) configured to detect incoming X-rays, wherein the X-ray detector (20) comprises a plurality of adjacent X-ray detector sub-modules, wherein each X-ray detector sub-module is oriented side-facing towards the incoming X-rays. The X-ray detector submodules are arranged side-by-side and / or sequentially, and the gaps between the X-ray detector submodules are at least partially filled with a material comprising metal disulfides mixed into a synthetic resin or organic resin or composite.

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