Visualization of the field of view in a phase-contrast X-ray imaging system

Abstract

A phase contrast X-ray imaging system with field of view (FOV) visualization is provided, which has a holder arranged to hold a grating and a light field projector to enable FOV illumination for an operator to visualize the area on the subject to be illuminated with X-rays. By utilizing a holder of the required object in the X-ray beam path (i.e., a grating) to hold the light field projector to illuminate the FOV, the solution is naturally more compact to implement and mechanical complexity is kept to a minimum. The light field projector provides a sharp and well-defined area with a well-defined outline of the FOV.

Description

Technical Field

[0001] The present invention relates to the field of phase contrast X-ray images, including phase contrast and dark field X-ray images. The present invention relates to a phase contrast X-ray imaging system having field of view (FOV) visualization, and a holder that enables integration of the FOV visualization function and enables visualization of the region irradiated with X-rays on a subject.

Background Art

[0002] Phase contrast X-ray images (PCI) provide higher sensitivity compared to conventional X-ray images and enable non-destructive imaging of low-density materials. These materials are present across a wide range of applications including, but not limited to, security, construction and building, electronics, and medical applications. In the latter case, phase contrast X-ray imaging systems can potentially offer advantages in clinical applications such as mammography, lung imaging, and bone imaging due to their ability to image subtle differences in material composition that are not accessible or only poorly accessible by other means using conventional X-ray imaging techniques.

[0003] Talbot interferometry (lattice-based imaging) and edge illumination (EI, sometimes called coded aperture technology) are some PCI techniques that are particularly attractive due to the possibility of implementing them using conventional X-ray sources as required for applications in commercial systems.

[0004] Grid-based phase-contrast X-ray imaging (PCI) requires one or more grid components. Exemplarily, the interference pattern generated by a first or phase grid component can be analyzed using a second or analyzer grid component, which is moved at various positions where intensity changes are recorded in the detector. For example, any source grid component may be included to enable the use of low-coherence X-ray sources, such as those commonly used in medical imaging. By placing an object within the interferometer apparatus along the X-ray beam path (e.g., between the source grid and the phase grid, or between the phase grid and the analyzer grid), the waveform as a function of the analyzer grid position can be recorded in the detector and compared to a reference case without an object in the X-ray beam path. The resulting waveform differs in several aspects, namely, average intensity, phase, and amplitude, which provide complementary information regarding attenuation, phase, and dark-field properties.

[0005] The EI approach is based on the fact that when X-rays interact with an object in the X-ray beam path, the direction of the X-rays experiences a slight deviation caused by a phase shift. The effect is enhanced by illuminating only the edges of the detector pixels. For example, photons that would have struck the surface of a detector pixel in the absence of an object will, in the presence of an object, experience a slight deviation sufficient to deflect them outside such a pixel surface. To implement and utilize this effect, typically a pair of edge objects acting as coding apertures, i.e., absorption gratings, are used. In the literature on coding aperture systems, these objects are often called coding aperture masks, and in the context of this invention, this term is also understood as an absorption grating, and the terms are used interchangeably. One of the coding aperture masks or absorption gratings is placed between the X-ray source and the object (a so-called sample mask, or sample absorption grating), generating a plurality of individual X-ray beams, each beam striking one of the pixel edges generated by a second so-called detector mask. In some detector pixels, specifically at the pixel edges masked by the detector mask, regions are defined in the detector that are both highly sensitive and insensitive (i.e., absorbent) to the X-ray region. By measuring the irradiation curve and comparing it with and without an object at a given location, attenuation signals, phase signals, and dark-field signals can be extracted.

[0006] Since a single phase-contrast X-ray imaging system, regardless of its implementation, provides both phase-contrast (PC) and dark-field (DAX) information (in addition to attenuated / transmitted X-ray information), in the context of this invention, the term phase-contrast X-ray imaging should be understood to cover both PC and DAX imaging. [Overview of the project] [Problems that the invention aims to solve]

[0007] Due to the nature of the radiation contained in these systems, it is necessary for the operator to collimate the X-ray beam into the desired field of view (FOV) and thus prevent undesirable radiation exposure. In particular, in medical applications, this is necessary to minimize the X-ray dose to the patient. Consequently, it is desirable, even regulatory requirements in medical applications, that the system can illuminate the area to be irradiated with X-rays before radiation exposure, and therefore visualize this so that the operator can control it as needed (e.g., to irradiate specific organs of the patient).

[0008] In conventional X-ray systems, the radiated area is indicated by a visible light source incorporated into a collimator box that emits the same beam as the X-ray source. In this concept, by using a mirror in the X-ray beam path that is transparent to the wavelength of the radiated beam, visible light located near the X-ray source is reflected to follow the same beam path and collimation as the X-rays. The conventional concept cannot be directly adopted in PCI systems because of the presence of optically opaque objects, i.e., gratings, in the X-ray beam path. In the case of EI-based PCI systems, the presence of a sample absorption grating, or at least a phase grating, is required, and in the case of grating-based PCI systems, either a source grating and / or a phase grating is required. Furthermore, in grating-based imaging, the so-called inverse geometry (when the subject is between the phase grating and the analyzer grating) may be desirable, as it gives the advantage that the largest grating (i.e., the analyzer grating) has the least demanding specifications in terms of grating period. In this scenario, applying this concept leads to a very bulky solution because the mirrors and collimators cannot be placed in the beam path following the X-ray source due to the opaque grating, and therefore require more distant positioning. The more light sources and mirrors are needed, the greater the distance to the focal point that the required number of mirrors becomes. Therefore, the problem of visualizing the area to be irradiated with X-rays before radiation exposure clearly requires special attention in PCI where an optically opaque grating exists in the X-ray beam path.

[0009] International Publication No. 2019076939 claims a system and method to address the aforementioned problem by using two optical fields projected toward a subject in two different optical field directions, partially overlapping each other on the subject to form overlapping optical field regions indicating the area to be radiated. In this invention, the optical fields are separated from the X-ray beam path and projected toward the subject from different paths, for example, from the sides of the radiation path, and therefore they have their own paths and collimation. By avoiding the radiation path, the solution tends to occupy more space than ideally desired and can be mechanically complex. Furthermore, the accuracy of the solution indicating the area to be radiated can be further improved. A simpler and more compact solution is desired that can achieve even greater accuracy while minimizing mechanical complexity. [Means for solving the problem]

[0010] Further advanced solutions are needed to address the irradiation problem in the presence of an opaque grating. This is achieved by the subject matter of each independent claim. Further embodiments of the present invention are described in their respective dependent claims.

[0011] Embodiments of the present invention relate to a phase-contrast X-ray imaging system with field-of-view (FOV) visualization. The system comprises an X-ray source configured to emit an X-ray beam through an inspection area toward a target area located within the inspection area; an X-ray detector position opposite the inspection area from the X-ray source; an X-ray beam shaper configured to shape the X-ray beam to irradiate a radiation area on the target area; a grating positioned between the X-ray source and the detector; an optical field projector configured to project an optical field in the visible spectrum on the target area, wherein the projected optical field corresponds to a radiation area; and a holder configured to hold the optical field projector and the grating. By utilizing a holder (i.e., the grating) of the necessary object in the X-ray beam path to hold the optical field projector for irradiating the FOV, instead of avoiding the radiation path, the solution is naturally more compact to implement, as no additional housing is actually required and mechanical complexity is kept to a minimum.

[0012] In one embodiment, the holder includes a first portion configured to hold an optical field projector and a second portion configured to hold a grid. The first and second portions are permanently or reversibly fixed to each other. In this way, the holder can be used and deployed more flexibly, and the supply and / or replacement of parts can be made more convenient.

[0013] In one embodiment, the diffraction grating is a phase diffraction grating, a light source diffraction grating, or a sample absorption diffraction grating. Thus, a variety of PCI systems and configurations of such systems benefit from the advantages of the claimed invention. For example, a grating-based imaging system in a so-called direct geometry configuration (subject located between the light source grating and the phase grating), a grating-based imaging system in a so-called inverse geometry configuration (subject located between the phase grating and the analyzer grating), or a coded aperture system.

[0014] In one embodiment, multiple light field projectors are mounted in a holder configured to project light fields onto a target area, and the combined projected light field marks the area corresponding to the radiation area. By using multiple light field projectors, the combination of independently projected light fields can result in even more accurate FOV visualization.

[0015] In one embodiment, the PCI system further includes a distance sensor for measuring the distance from the plane on which the optical field is projected to the plane on which the target region is located. A more advanced system with such a distance sensor facilitates the possibility that the optical field projector may have a different source point than that of the X-ray source. In the latter case, such distance measurement enabled by the distance sensor contributes to accurate FOV visualization.

[0016] In one embodiment, the optical field projector is a laser device or projector. The laser device or projector generates a sharp and distinct area so that the FOV can be visualized with sharp and distinct contours. Furthermore, the use of a laser device can enhance the functionality of the system. The beam may be used when detected by an additional sensor on the detector side for alignment and automatic position checking. The use of a projector can also increase the functionality of the system by enabling the projection of additional information, such as alignment to the patient's body with projection of body shape, and based on complementary target data, the projection of a target area (e.g., body part) may favor the application of the correct FOV set, or any other relevant data for examination confirmation (e.g., patient's name, purpose of scan, date of birth, etc.). Furthermore, the projector may be complemented by a feedback device (e.g., a camera) that allows the operator to control the FOV set via gesture control on the back of the subject (e.g., actions on a touchscreen). In addition to the increased functionality through the projection of additional information, such a user interface can improve the workflow and enable faster and more accurate FOV setting, which may be fully automated.

[0017] In one embodiment, the laser apparatus is configured such that an optical field projector projects a linear shape, and the system further comprises a guide rail mounted on a holder, the guide rail having a curvature with a center coinciding with the focal center of an X-ray source, and is configured to allow movement of the laser apparatus along the guide rail. By moving the laser apparatus along the guide rail, which shares the same source point (i.e., the focal center of the X-ray source) with respect to the X-ray source, a combination of projected linear shapes can be achieved to perform a very accurate and relatively simple laser apparatus for indicating the boundary of the FOV, as long as the position of the guide rail coincides with the edge of the system's FOV set, for example, the edge of the collimator blade of a collimator.

[0018] In one embodiment, the optical field projector is configured to update the projected optical field when the radiant region is changed to the updated radiant region, so that the updated projected optical field corresponds to the updated radiant region. In this way, seamless operation of the system, which is advantageous for the workflow, is achieved.

[0019] Further embodiments of the present invention relate to a holder positioned to hold a grating for a phase-contrast X-ray imaging system and an optical field projector for projecting an optical field toward an optical field target region. Such a holder, having the dual purpose of holding both the grating and the optical field projector, is a simple, practical, and compact method that enables more efficient integration of FOV visualization capabilities when installed in a phase-contrast X-ray imaging system.

[0020] In one embodiment, the holder includes a first portion configured to hold an optical field projector and a second portion for holding a grid, wherein the first and second portions are permanently or reversibly fixed to each other.

[0021] In one embodiment, the optical field projector is a laser device or a projector.

[0022] In one embodiment, the holder further comprises a guide rail attached to the holder, the guide rail being configured to allow the movement of an optical field projector along a curved section of the guide rail.

[0023] In one embodiment, the optical field projector comprises multiple laser devices configured to project a linear shape, mounted on a first portion of a holder via guide rails using a spindle having threads. The threads have a reverse slope that allows for symmetrical movement of the laser line shape projected by the laser devices with respect to an axis coinciding with the optical axis of the phase-contrast X-ray imaging system when installed in the phase-contrast X-ray imaging system. Thanks to such symmetrical movement of the laser devices, the positions of the multiple laser devices can be controlled in conjunction, and the position of the laser devices along the guide rails can be directly translated into the required number of rotations of the spindles.

[0024] In one embodiment, when the holder is installed in a phase-contrast X-ray imaging system, it further includes a distance sensor for measuring the distance between the optical field projector and the optical field target region.

[0025] In one embodiment, the optical field projector comprises at least one laser device mounted on a first portion of a holder, configured to project a collimated laser spot toward an optical field target region and to scan over the optical field target region so that the boundaries of the optical field target region are visualized. This embodiment constitutes an alternative to projecting an optical field toward an optical field target region without relying on the mechanical motion of the laser device, and instead of based on a linear shape, it outlines the area through the collimated laser spot projection thanks to the laser spot scan across the optical field target region.

[0026] In one embodiment, the light field projector includes at least one projector attached to a first portion of the holder, and the light field is configured to project a light field toward the light field target area so as to form a light field that covers and defines the entire light field target area. Generally, the use of the projectors has the advantages described above. Since multiple projectors cover an area whose boundaries are within a region of low parallax and depend on a combination of independently projected light fields that define that area, even more accurate implementation can be provided.

[0027] In one embodiment, at least one of the at least one projector projects additional information on or near the light field target area, such as projection of the target area, alignment of the subject's body by projection of the body shape, and / or other data, thus completely providing an improvement in the workflow. These and other aspects of the invention will become apparent from the embodiments described below and will be described with reference to them.

Brief Description of the Drawings

[0028] [Figure 1A] A schematic diagram of a PCI system with FOV illumination is shown, and the holder of the phase grating is also arranged to hold a light field projector, as described in connection with the present invention. A PCI system is shown. [Figure 1B] A more detailed view of the FOV visualization of the PCI system of FIG. 1A is shown. [Figure 2A] A schematic diagram of a PCI system with FOV illumination as described in connection with the present invention is shown. The PCI system is a grating-based imaging system in which the holder of the phase grating also holds a light field projector. [Figure 2B] The PCI system is an EI-based imaging system, and the holder of the sample absorption grating is also arranged to hold a light field projector. [Figure 3A]This section describes embodiments relating to a holder as described in connection with the present invention. A schematic diagram of an exemplary holder arranged to hold a PCI system grating and an optical field projector is shown. [Figure 3B] Diagrams from different perspectives illustrate the design concept of a guide rail having a spindle with threads to which an optical field projector is mounted. [Figure 4A] A schematic diagram of a PCI system having FOV irradiation enabled by multiple laser devices is shown, and the phase grating holder is also arranged to hold an optical field projector, as described in relation to the present invention. This is a side view of the PCI system. [Figure 4B] This is a top view of the PCI system. [Figure 5A] A schematic side view of a PCI system having FOV irradiation is shown, and the holder of the phase grating G1 is also arranged to hold an optical field projector, as described in relation to the present invention. FOV irradiation is enabled by the projector. [Figure 5B] This is made possible by using multiple projectors. [Modes for carrying out the invention]

[0029] The present invention can take the form of various arrangements of components and constituent elements, as well as various processing operations and arrangements of processing operations. The drawings are intended solely to illustrate preferred embodiments and should not be construed as limiting the invention. Certain features may be omitted or dimensions may not conform to scale for better visualization. Similar components are given the same reference numerals in different drawings.

[0030] This detailed description presents various specific details. Embodiments of the present invention can be carried out without these specific details. Furthermore, well-known features, elements, and / or steps are not necessarily described in detail for the sake of clarity and brevity of this disclosure.

[0031] The present invention provides a solution for illuminating the field of view (FOV) of a phase-contrast X-ray imaging (PCI) system, allowing the operator to visualize the area on the subject being irradiated with X-rays and thus control the FOV as needed. It would be advantageous to provide a precise, compact, and relatively simple implementation solution for PCI systems having optically opaque objects (e.g., gratings) in the X-ray beam path. To better address one or more of these challenges, the present invention utilizes an object already present in the X-ray beam path to enable FOV visualization. Accordingly, in a first aspect, the present invention relates to a phase-contrast X-ray imaging system with FOV visualization, and in a second aspect, the present invention relates to a holder positioned to hold an existing object in the X-ray beam path and an optical field projector for enabling FOV visualization.

[0032] Referring to Figure 1A, a schematic diagram of a PCI system with FOV irradiation is shown. The PCI system comprises an X-ray source 10 having an X-ray tube focal center O, an X-ray beam shaper 20, and an X-ray detector 40. The X-ray source 10 is configured to emit an X-ray beam through an examination area 50 toward a target area 31 located within the examination area 50, for example, one part of a patient. The X-ray beam shaper 20 is configured to shape the X-ray beam to irradiate a radiation area 32 on the target area 31. The X-ray detector 40 is positioned on the opposite side of the examination area 50 from the X-ray source 10. The PCI system also includes a grating G, for example, a phase grating G1, positioned between the X-ray source 10 and the detector 40. A holder 60, positioned to hold the grating G and an optical field projector 61, also constitutes the system. The optical field projector 61 projects the contour / area of ​​the FOV onto the object to be imaged. For this purpose, the optical field projector 61 is configured to project an optical field in the visible spectrum onto a target region 31, and the projected optical field 33 corresponds to the radiant region 32. This is schematically shown in Figure 1A, and a more detailed FOV visualization is shown in Figure 1B. The correspondence between the projected optical field 33 and the radiant region 32 means that the region defined by the projected optical field 33 is equivalent or nearly equivalent to the radiant region 32. Here, "equivalent" means that there is a perfect fit between the region defined by the projected optical field 33 and the radiant region 32. In the context of the present invention, the term "nearly equivalent" means that the fit between the regions is substantial within a reasonable margin of error (e.g., within a margin given by a regulatory authority, or an error of the order of 10% or less, preferably 5% or less, more preferably 1% or less), such errors being, for example, slight differences (i.e., 1, 5 or 10% or less) between the surfaces of the regions and / or slight mismatches (i.e., 1, 5 or 10% or less) between the geometric centers of the regions.

[0033] In one example, the PCI system may be a grid-based imaging system as shown in Figure 2A, where so-called inverse geometry is represented. In this case, during the imaging procedure, the subject is located within the inspection area 50 between the phase grid G1 and the analyzer grid G2. Given this setting, in one embodiment, as shown in the figure, the holder 60 of the phase grid G1 is also positioned to hold the optical field projector 61. In another embodiment (not shown) where so-called direct geometry is used, i.e., when the subject is located within the inspection area 50 between the light source grid G0 and the phase grid G1 during the imaging procedure, the holder 60 of the light source grid G0 is also positioned to hold the optical field projector 61.

[0034] In one example, the PCI system may be an EI-based system, i.e., a coded aperture system as shown in Figure 2B. The beam generated by the X-ray source 10 is split into multiple individual beams by a sample absorption grating SG (a so-called sample mask). Thereafter, the absorption grating SG can function as both a beam shaper 20 and a grating G, potentially simplifying the system by optionally eliminating the need for a dedicated beam shaper 20. In one embodiment, as shown in the figure, the holder 60 for the sample absorption grating SG is also positioned to hold an optical field projector 61. In this case, during the imaging procedure, the subject is positioned between the sample absorption grating SG and the detector mask DM.

[0035] From the aforementioned examples, it is clear that alternative embodiments of PCI systems, similarly involving the use of optically opaque objects in the X-ray beam path (such as diffraction gratings G), would benefit from the currently claimed invention. By utilizing holders 60 for the required objects in the X-ray beam path (e.g., holders 60 for the grating G), no additional housing is effectively required, and therefore the solution is naturally more compact to implement.

[0036] In the context of the claimed invention, the term "optical field projector" refers to a device for projecting an optical field in the visible spectrum. The optical field projector 61 is intended to visualize the FOV, as schematically shown in Figure 1B. In the figure, the pattern of vertical lines indicates a target region 31, for example, one part of a patient, and the pattern of horizontal lines indicates a radiation region 32 to be irradiated with X-rays, according to the FOV of the PCI system. The optical field projector 61 projects an optical field towards an optical field target region 33 corresponding to the radiation region 32, thereby enabling visualization of the FOV. As shown in Figure 1(b), visualization of the FOV 33 may be achieved by a cover and boundary (dotted line region), or by a projected boundary (boundary of the dotted line region).

[0037] Examples of optical field projectors 61 include, but are not limited to, projectors or laser devices. Various types of projectors 61 exist, which may depend on the light source they use (e.g., lamps, LEDs, or lasers) and the projection technology. Some examples include DLP (Digital Photon Processing), LCD (Liquid Crystal Display), LED, LCoS (Liquid Crystal on Silicon), or laser projectors. Furthermore, they may be full-size projectors or handheld projectors (e.g., mini-projectors, pico-projectors). In the currently claimed invention, smaller projectors are preferable as they occupy limited space, are lightweight, and are therefore more convenient for support devices such as holders 60. A laser device is defined as a device comprising one or more lasers as a light source and means (e.g., optical lenses, mirrors) for shaping the laser beam into any shape or pattern (e.g., lines, dots, crosses, edges, rectangles, etc.). Other types of optical field projectors 61 may be considered, in particular, if they can produce sharp and clear areas.

[0038] Referring next to the holder 60, a schematic diagram of an exemplary holder 60 is shown in Figure 3A. The holder 60 is positioned to hold the grating G of the PCI system and an optical field projector 61 that projects an optical field toward the optical field target area 33. In one embodiment, the holder 60 comprises a first part positioned to hold the optical field projector 61 and a second part positioned to hold the grating G. The first and second parts are permanently or reversibly fixed to each other, in either case providing flexibility in the use, supply, and replacement of the parts. The optical field projector 61 may be a laser device, a projector, or any other type of optical field projector. At least one or more of these may be mounted on the holder 60, an example of which is schematically shown in Figure 3A. When the holder 60 is installed in the PCI system, it may further include a distance sensor 65 (not shown) for measuring the distance D between the optical field projector 61 and the optical field target area 33, for example, a part of the patient. In another embodiment, the holder 60 further comprises a guide rail 62 attached to the holder, configured to allow the movement of an optical field projector 61 along the guide rail 62 which includes curvature. The laser device 61 is mounted to the guide rail using a spindle 63 having threads. An exemplary implementation of such a spindle 63 together with the threads and the guide rail 62 which includes a curved section is shown in Figure 3B. In the exemplary embodiment, this is realized by a structure comprising two spindles 63 having threads fixedly connected to each other, and a guide joint 64 for ensuring that the spindle position (and therefore the optical field projector position) is securely held as a whole. The spindles 63 have threads with opposite inclinations (S, S') which result in the optical field projector 61 moving in opposite directions (e.g., left / right, up / down) when the spindles are rotated, and the opposite thread inclinations S, S' are indicated in the figure by opposite-direction arrows. The structure also includes a fixture for holding the optical field projector 61 mounted to the holder 60 via the guide rail 62.Views from different perspectives of the overall design concept of the guide rail 62, including a curved section with a threaded spindle 63, are shown in the view. In one example, the laser device 61 is mounted to the first part of the holder 60 via the guide rail 62 having a threaded spindle 63. The purpose of the guide rail 62 having curvature, the spindle 63 having threads with opposite slopes, and the distance sensor 65 will be explained when describing Figures 4 and 5. Those skilled in the art will understand that there are alternative embodiments for the threaded spindle 63, for example, one alternative form based on a single spindle with two threads of opposing slopes, and one alternative form based on two disconnected spindles with two independent motors. The movement of the optical field projector 61 along the guide rail 62 may be generated by means other than the threaded spindle 63, for example, by a linear motor or a toothed belt.

[0039] Figure 4A shows a PCI system having optical FOV irradiation enabled by multiple optical field projectors 61. More specifically, in the system of Figure 4A, the X-ray beam shaping unit 20, in this case a collimator, collimates the X-ray beam to the desired FOV via a collimator blade, and the optical field projectors 61 are laser devices 61 configured to project a linear shape. The system further comprises a guide rail 62 having a spindle 63 to which the thread shown in Figure 3B is attached to a holder 60, in which the thread also serves as a holder for the phase grating G1. The guide rail 62 is configured to allow the laser devices 61 to move along the guide rail 62 and has a curvature with a center that coincides with the center of the focal point O of the X-ray source 10. Four laser devices 61, each projecting linearly, are required to project the FOV boundary onto the target region 31 to be imaged. The laser devices 61 are configured to move along the guide rail 62 according to the collimator blade position so that the linear shape generated by the laser devices 61 coincides with the edge of the collimator blade. To ensure the precise movement of the four laser devices 61, they are mounted on a first part of the holder through guide rails 62 using spindles 63 with threads, as exemplified in Figure 3B, the threads having opposite inclinations S, S'. More specifically, two of these guide rails 62 are used, with two laser devices 61 mounted on each, as shown in Figure 3B, with one guide rail 62 mounted on the top or bottom of the holder 60 and the other on the left or right side. The guide rails 62 share the same source point with respect to the X-ray source 10 (i.e., the center of the focal point O of the X-ray source 10), and through the opposite inclinations S, S', left / right (up / down) symmetrical movement of the laser line shape projected by the laser devices with respect to the optical axis of system A can be achieved. This implementation minimizes mechanical complexity. Figures 4A and 4B show side and top views of the system, respectively, where the shape of the projected line coincides with the collimated X-ray beam, indicated by dashed lines and thanks to the described mechanism.The shape of the projected line appears to be perpendicular to the drawing plane, and the combined projected light field generates an area 33 corresponding to the radiating area 32, enabling visualization of the FOV. Thus, in one embodiment, the PCI system comprises a plurality of light field projectors 61 mounted on a holder 60 configured to project a light field onto a target area 31, and the combined projected light field marks an area 33 corresponding to the radiating area 32.

[0040] To use the system in Figure 4 for FOV visualization, a control unit (not shown) can map the blade position of the collimator 20 to the corresponding laser device 61 position in the guide rail 62 such that the line shape generated by the laser device 61 coincides with the edge of the collimator blade, and therefore the region 33 corresponding to the irradiation area 32 is visualized. The calibration procedure can also be performed, for example, when the FOV may be irradiated with multiple collimator blade apertures, and in each case, the position of the laser device 61 can be configured to coincide with the edge of the collimator blade. Intermediate positions can be interpolated. As can be seen from Figure 3B (e.g., lower left), the laser device 61 is mounted so that it can move to the same point as when the collimator blade is fully closed. The position of the laser device 61 is then directly translated to the required number of rotations of the spindle 63, making the approach relatively easy to implement. Such use can be performed manually or (semi)automatically. In one embodiment, the optical field projector 61 is configured to update the projected light field 33 when the radiant region 32 is changed to the updated radiant region 32 (for example, by moving the collimator blade) so that the projected light field 33 to be updated corresponds to the updated radiant region 32.

[0041] The system shown in Figure 4 allows for extremely accurate display of the field of view (FOV) on the subject, which has the advantage of being independent of the subject's position along the optical axis A, because each laser device 61, through the mechanical movement of the optical field projector 61 along the guide rail 62, reaches a plane including the center of the focal point O of the X-ray source 10 and the edge of one collimator blade.

[0042] A further advantage of using the laser device as an optical field projector 61 is that it provides the option to use the beam when detected by additional sensors on the detector side for alignment and automatic position checks. One check may not require the subject to be in the laser beam, as a normal geometry control, while a second option may involve the subject being in the laser beam as a subject positioning control, for example, to see if the subject is in a symmetrical position in front of the detector 40. The light intensity transmitted at specific landmarks of the object being imaged can provide further information about the object's characteristics. For example, if the subject is a patient, the light intensity transmitted in the shoulder / neck region may indicate the patient's size / height / position relative to the source and the patient's position. The light intensity may also indicate movement that can guide the patient and / or trigger acquisition at moments when there is no (limited) patient movement.

[0043] An alternative example of FOV visualization that does not depend on the mechanical motion of the laser device 61 along the guide rail 62 is shown in the PCI system of Figure 1A. In the figure, a holder 60 is positioned to hold the optical field projector 61 and the phase grating G1, and a collimator 20 collimates the X-ray beam to a desired FOV via the collimator blade. To avoid dependence on the mechanical motion of the optical field projector 61, the system further includes measuring the distance D from the plane B on which the optical field is projected to the plane C on which the target area 31 is located, and calculating the projection angle of the optical field projector 61 (e.g., laser device 61) to correspond to the area 32 on which the projected optical field 33 should be illuminated; in other words, the FOV setting of the collimator 20, i.e., the collimator blade position, is mapped to the projection angle of the optical field projector 61 (e.g., laser device 61) for a given distance D. The system in Figure 1A further includes a distance sensor 65 for measuring the distance D. In another example (not shown), at least one laser device 61 attached to a first portion of the holder 60 is configured to project a laser spot collimated toward a field of view target area 33 and to scan over the FOV so that the boundaries of the FOV are visualized. The laser spot should be scanned quickly enough so that it appears as a solid line to the observer's eye. Similarly, the distance D from the plane B on which the light field is projected to the plane C on which the target area 31 is located needs to be measured, and the scan range (e.g., start and end scan xy positions) is determined to correspond to the area 32 on which the projected light field 33 should illuminate. In one embodiment, the PCI system further comprises a distance sensor 65 for measuring the distance from the plane B on which the light field is projected to the plane C on which the target area 31 is located. Clearly, the distance D measurement is required when the projected light field does not have the same light source point as the X-ray source 10 (i.e., the center of the focal point O of the X-ray source 10), and considering this distance when projecting a light field with a different light source point than that of the X-ray source contributes to correct FOV visualization.

[0044] Figure 5A illustrates a PCI system with optical FOV visualization enabled by an optical field projector 61, which includes a projector 61 held by a holder 60 of a phase grating G1. Similar to the system in Figure 4, the collimator 20 collimates the X-ray beam to a desired FOV via the collimator blade. The set FOV is then mapped to an image projected by the projector 61, thereby forming an optical field that covers and defines the entire FOV 33 corresponding to the radiation region 32. Changes in the FOV 32 are mapped to different images 33 to be projected onto the subject, and therefore there is no need for mechanical movement of optical elements. However, the image projected by the projector does not have the same source point as the X-ray source. Therefore, the FOV can only be accurately visualized at the position of the subject along the optical axis A (i.e., a specific distance D from the plane B on which the optical field is projected to the plane C on which the target region is located). Exemplarily, in a device such as the one depicted in Figure 5A, the projection area has a greater error at the bottom than at the top. A more detailed analysis using realistic assumptions about the geometric shape shows that an accuracy of ±1 cm can be achieved at the bottom if the subject position along the optical axis A does not deviate by more than ±5 cm from the desired position. On the other hand, the top edge is projected with an accuracy of ±1 cm as long as the subject does not deviate by more than ±22 cm from the desired position. Of course, these tolerances vary depending on the collimation (i.e., FOV), and in particular, the range decreases as the collimation narrows.

[0045] Figure 5B shows a more precise schematic of the implementation, which includes multiple projectors 61, with two projectors 61 projecting portions of the FOV independently (partially overlapping) onto the subject. The combination of independently projected light fields improves overall accuracy because the projected boundary of the FOV covers and defines the entire region 33 where the parallax is low.

[0046] In yet another embodiment (not shown), the system includes four projectors 61 mounted on a holder 60 (arranged, for example, as shown in Figure 3A) to achieve high accuracy for all four boundaries of the FOV. Since the distance D from the plane B on which the light field is projected to the plane C on which the target region is located further contributes to accurate FOV visualization, a more advanced embodiment includes a distance sensor 65, as shown in Figure 5B.

[0047] The use of the projector 61 not only enables visualization of the FOV but also allows for the projection of additional information onto or near the light field target area 33. For example, the additional information may include alignment to the patient's body with projections of body shape, projections of target areas (e.g., body parts) to support the application of the correct FOV set based on complementary subject data, or any other relevant data for examination confirmation (e.g., patient's name, purpose of scan, date of birth, etc.). Furthermore, the projector 61 may be complemented by a feedback device (e.g., a camera) that allows the operator to control the FOV set via gesture control on the back of the subject (e.g., actions on a touchscreen). In addition to the increased functionality due to the projection of additional information, such a user interface improves the workflow and enables faster and more accurate FOV setting, which may be fully automated.

[0048] As shown in Figures 1A and 5, to use an embodiment of the system for FOV visualization that does not depend on the mechanical motion of the optical field projector, a control unit (not shown) can map the FOV settings to the FOV irradiation settings for a specific distance D between the optical field projector 61 and the target area 31, such that the projection area 33 corresponds to the radiation area 32. For example, the control unit may map FOV settings such as the collimator blade position to FOV irradiation settings such as the image projected by the projector 61, the projection angle of the laser device 61, the scan range of the laser device 61, etc. Measurements from the distance sensor 65 can also be monitored by the control unit for more accurate implementation. Calibration procedures or lookup tables can be performed for the purpose of mapping FOV settings to FOV irradiation settings. Furthermore, the FOV irradiation set can be configured to update when the radiation area 32 is changed to the updated radiation area 32, such that the updated irradiation area 33 corresponds to the updated radiation area 32. The operation can be performed manually or (semi)automatically.

[0049] It should be noted that in the context of this invention, the imaged “subject” may refer to the body / patient or part thereof of a dead or living human or animal, or a plant or part of a plant. Furthermore, it may represent an inanimate subject such as an item or baggage in a security screening system, or a sample object in non-destructive materials testing. Thus, although the claimed invention is intended for medical applications, it is also very suitable for applications in non-destructive testing (e.g., analysis of the composition, structure and / or quality of biological and non-biological samples) and security scanning (e.g., scanning baggage at airports).

[0050] It should be noted that embodiments of the present invention are described with reference to different subject matter. In particular, some embodiments are described with reference to system-type claims, and other embodiments are described with reference to apparatus-type claims. However, those skilled in the art will gather from the above description that, unless otherwise notified, any combination of features belonging to one type of subject matter, as well as any combination of features relating to different subject matter, are disclosed in this application. However, all features can be combined to provide a synergistic effect greater than the simple sum of the features.

[0051] Although the present invention is illustrated and described in detail in the drawings and the foregoing description, such illustrations and descriptions should be considered illustrative or non-limiting, and the present invention is not limited to the embodiments disclosed. Other variations of the disclosed embodiments can be understood and achieved by those skilled in the art in carrying out the claimed invention from the study of the drawings, disclosure and the appended claims.

[0052] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude the plural.

[0053] A single unit or device can fulfill the functions of several items enumerated in the claims. The mere fact that certain means are described in different dependent claims does not imply that combinations of these means cannot be used advantageously.

[0054] No reference numeral in a claim should be construed as limiting the scope. The embodiments of the present invention are described below. (Note 1) A phase-contrast X-ray imaging system, An X-ray source configured to emit an X-ray beam through the inspection area toward a target area located within the inspection area, An X-ray detector located on the opposite side of the inspection area from the X-ray source, An X-ray beam shaper configured to shape an X-ray beam and irradiate a radiation region on the target region, A grating located between the X-ray source and the detector, A light field projector configured to project a light field in the visible spectrum onto the target region, wherein the projected light field corresponds to the radiating region, A holder arranged to hold the aforementioned optical field projector and grid. A phase-contrast X-ray imaging system having the following features. (Note 2) The system according to Appendix 1, wherein the holder includes a first portion configured to hold the optical field projector and a second portion configured to hold the grid, and the first portion and the second portion are permanently or reversibly fixed to each other. (Note 3) The system according to any one of Appendix 1 or 2, wherein the grid is a phase grid, a light source grid, or a sample absorption grid. (Note 4) The system according to any one of Appendix 1 to 3, wherein multiple light field projectors are mounted in a holder configured to project light fields onto a target area, and the combined projected light fields mark an area corresponding to the radiating area. (Note 5) The system according to any one of appendices 1 to 4, further comprising a distance sensor for measuring the distance from the plane on which the light field is projected to the plane on which the target region is located. (Note 6) The optical field projector is a laser device or a projector, as described in any one of Appendix 1 to 5. (Note 7) The optical field projector is a laser device configured to project a linear shape, the system further comprising a guide rail attached to the holder, the guide rail having a curvature having a center coinciding with the focal center of the X-ray source, the system according to any one of appendices 1 to 6. (Note 8) The system according to any one of Appendix 1 to 7, wherein the optical field projector is configured to update the projected optical field when the radiant region is changed to the updated radiant region such that the updated projected optical field corresponds to the updated radiant region. (Note 9) The grid of the phase contrast X-ray imaging system, An optical field projector for projecting an optical field toward an optical field target area. A holder configured to hold something. (Note 10) The holder according to Appendix 9, comprising a first portion configured to hold the optical field projector and a second portion for holding the grid, wherein the first portion and the second portion are permanently or reversibly fixed to each other. (Note 11) The holder described in Appendix 9 or 10, wherein the optical field projector is a laser device or a projector. (Note 12) The holder according to any one of appendices 9 to 11, further comprising a guide rail attached to the holder, the guide rail being configured to allow the movement of the optical field projector along the guide rail having curvature. (Note 13) The optical field projector has a plurality of laser devices configured to project a linear shape and mounted to the first part via the guide rail using a spindle having threads, wherein the threads have a reverse slope that allows for symmetrical movement of the projected laser linear shape with respect to an axis coinciding with the optical axis of the phase contrast X-ray imaging system when installed in the phase contrast X-ray imaging system, as described in Appendix 12. (Note 14) The holder according to any one of appendices 9 to 13, further comprising a distance sensor for measuring the distance between the optical field projector and the optical field target region when installed in a phase contrast X-ray imaging system. (Note 15) The holder according to any one of appendices 11 to 14, wherein the optical field projector is attached to a first portion of the holder and has at least one laser device configured to project a collimated laser spot toward the optical field target region and to scan the optical field target region so that the boundary of the optical field target region is visualized. (Note 16) The holder according to any one of appendices 11 to 14, wherein the optical field projector has at least one projector attached to the first portion of the holder and is configured to project an optical field toward the optical field target region to form an optical field that covers and defines the entire optical field target region. (Note 17) The holder according to Appendix 16, wherein at least one of the at least one projector projects further information on or near the light field target area, such as projection of a target area, alignment with projection of body shape onto the subject's body, and / or other data.

Claims

1. A phase-contrast X-ray imaging system, An X-ray source configured to emit an X-ray beam through the inspection area toward a target area located within the inspection area, An X-ray detector located on the opposite side of the inspection area from the X-ray source, An X-ray beam shaper configured to shape an X-ray beam and irradiate a radiation region on the target region, A grating located between the X-ray source and the detector, A light field projector configured to project a light field in the visible spectrum onto the target region, wherein the projected light field corresponds to the radiating region, A holder arranged to hold the aforementioned optical field projector and grid, A guide rail attached to the holder, configured to allow the movement of the optical field projector along the guide rail having curvature, A phase-contrast X-ray imaging system having the following features.

2. The system according to claim 1, wherein the holder includes a first portion configured to hold the optical field projector and a second portion configured to hold the grid, the first portion and the second portion being permanently or reversibly fixed to each other.

3. The system according to any one of claims 1 to 2, wherein the grid is a phase grid, a light source grid, or a sample absorption grid.

4. The system according to any one of claims 1 to 3, wherein multiple light field projectors are mounted in a holder configured to project light fields onto a target area, and the combined projected light fields mark an area corresponding to the radiating area.

5. The system according to any one of claims 1 to 4, further comprising a distance sensor for measuring the distance from the plane on which the optical field projector is located to the plane on which the target region is located.

6. The system according to any one of claims 1 to 5, wherein the optical field projector is a laser device or a projector.

7. The system according to any one of claims 1 to 6, wherein the optical field projector is a laser device configured to project a linear shape, and the curvature of the guide rail has a center that coincides with the center of focus of the X-ray source.

8. The system according to any one of claims 1 to 7, wherein the optical field projector is configured to update the projected optical field when the radiant region is changed to the updated radiant region such that the updated projected optical field corresponds to the updated radiant region.

9. The grid of the phase contrast X-ray imaging system, An optical field projector for projecting an optical field in the visible spectrum toward an optical field target region, and when used in a phase-contrast X-ray imaging system, the projected optical field corresponds to the region to be emitted, and the optical field projector and A holder configured to hold, A guide rail attached to the holder, further comprising a guide rail having curvature, configured to allow the movement of the optical field projector along the guide rail, Holder.

10. The holder according to claim 9, comprising a first portion configured to hold the optical field projector and a second portion for holding the grid, wherein the first portion and the second portion are permanently or reversibly fixed to each other.

11. The holder according to claim 9 or 10, wherein the optical field projector is a laser device or a projector.

12. The holder according to claim 10, wherein the optical field projector has a plurality of laser devices configured to project a linear shape and mounted on the first part via the guide rail using a spindle having threads, the threads having a reverse slope that allows for symmetrical movement of the projected laser linear shape with respect to an axis coinciding with the optical axis of the phase contrast X-ray imaging system when installed in the phase contrast X-ray imaging system.

13. The holder according to any one of claims 9 to 12, further comprising a distance sensor for measuring the distance between the optical field projector and the optical field target region when installed in a phase contrast X-ray imaging system.

14. The holder according to any one of claims 11 to 13, wherein the optical field projector is attached to a first portion of the holder and has at least one laser device configured to project a collimated laser spot toward the optical field target region and to scan the optical field target region so that the boundary of the optical field target region is visualized.

15. The holder according to any one of claims 11 to 13, wherein the optical field projector has at least one projector attached to a first portion of the holder, and is configured to project an optical field toward the optical field target region to form an optical field that covers and defines the entire optical field target region.

16. The holder according to claim 15, wherein at least one of the at least one projector projects further information onto or near the optical field target area.

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