X-ray imaging apparatus and method

Abstract

An x-ray imaging device for producing an x-ray image of an object comprises a support frame to which an x-ray source and an x-ray detector are connected. The x-ray source and the x-ray detector define an object space for an object to be inspected between them. The x-ray source is configured to emit an x-ray beam having a main direction from a focal spot into the object space. The x-ray detector comprises an array of pixels sensitive to x-ray radiation. The x-ray imaging device further comprises a collimator arranged close to the x-ray source and in the path of the x-ray beam between the x-ray source and the object to be inspected. The collimator comprises one or more collimator bodies defining a plurality of channels of the collimator, the channels having respective central directions defining a common focus of the collimator on the side of the x-ray source, the channels preferably being channels of a 2D array as seen in a plane perpendicular to the main direction of the x-ray beam.

Description

Technical Field

[0001] The present invention relates to an X-ray imaging apparatus for producing an X-ray image of an object, comprising:

[0002] a support frame to which the x-ray source and the x-ray detector are attached,

[0003] wherein the x-ray source and the x-ray detector define between them an object space for the object to be examined,

[0004] The x-ray source is configured to emit an x-ray beam having a main direction from the focal spot into object space,

[0005] The x-ray detector includes an array of pixels sensitive to x-ray radiation. Background Art

[0006] Such x-ray imaging devices are well known and are used to examine an object, such as a living organism, such as a small animal, or a specimen, by sending a beam of x-ray radiation through the object and detecting the radiation after being attenuated by the object.

[0007] A problem with known x-ray imaging devices is that they do not always provide detected images with a sufficiently high resolution, especially if the size of the objects to be examined varies relatively widely, and more specifically if they are relatively small relative to the x-ray source. The latter is relevant, for example, for small animal imaging, where the internal organs or structures in the body of an animal (e.g. a mouse) may be very small. Some x-ray sources are known in which the focal spot or the area from which photons are emitted is itself small, or in which it is possible to switch between a large focal spot and a small focal spot. These small focal spot x-ray sources can be impractical in that they are usually rather bulky, for example because the "electron accelerator" or voltage source is usually located directly behind the anode of the source, which is undesirable, and they usually have a relatively short service life due to greatly increased wear. Summary of the Invention

[0008] It is therefore generally an object of the present invention to provide an x-ray imaging device of the above-mentioned type which is able to provide high-resolution images even of small objects, for example in small animal imaging.

[0009] It is a further object of the present invention to enable the use of compact and / or long-lived x-ray sources which still have high resolution.

[0010] The present invention provides an x-ray imaging apparatus according to claim 1 .

[0011] An x-ray imaging device according to the present invention can achieve one or more of the objectives, since the collimator can be used as a device for selecting only a relatively small portion of the focal spot of an x-ray source. Typically, such an x-ray source is an x-ray tube having an emission area, i.e., a focal spot, of a specific size, which is not negligibly small relative to the structures in the object to be examined, in particular the details required therefor, and therefore the achievable resolution is usually insufficient. By using a collimator device according to the present invention close to the x-ray source (which, as will be explained herein, has a channel whose central direction originates from the focal spot or, more precisely, the focal volume), the apparent size of the x-ray focal spot is further reduced. In fact, the effective size becomes close to the size of the focal spot or focal volume of the collimator. Depending on the characteristics of the collimator, these dimensions can be limited in embodiments to a few micrometers for small animal imaging, or a few tenths of a millimeter for use in clinical x-ray systems or CT scanners.

[0012] In theory, it is possible to make all the central directions of the collimator's channels originate from exactly one point, the focal point. However, in practice, the x-rays emerging from the channels will still be distributed in a range of directions around the central direction of the channel. This means that the apparent source of the x-rays emerging from a single channel is also a "fuzzy" focus, the focal volume. However, since each channel will have a non-negligible length, this distribution, i.e. the size of the focal volume, can be significantly smaller than the original focal spot area of the x-ray source.

[0013] According to the present invention, the collimator is positioned close to the x-ray source and between the x-ray source and the object to be imaged. In practice, the collimator will be positioned very close to the x-ray source, in particular as close as possible to the x-ray source. In a practical embodiment, the x-ray source is an x-ray tube having a housing including an x-ray window through which the x-ray beam exits the x-ray source, wherein the collimator is arranged outside the window and close to the window, for example a beryllium window.

[0014] Preferably, the collimator and any collimator mover (when present) are mounted to a support frame, for example, on and / or near the x-ray source. For example, in embodiments where the support frame is movable by a support frame drive to bring the x-ray source into various spatial positions relative to the object space, the collimator then follows the movement of the support frame and is maintained close to the x-ray source and in the path of the x-ray beam between the x-ray source and the object to be examined.

[0015] The distance between the collimator and the x-ray source is preferably fixed, for example, to allow for positioning the focal point of the collimator channel at the actual focal spot of the x-ray source. For example, the collimator can be moved by an associated mover in a direction or plane perpendicular to the extension of the x-ray beam, but cannot be moved along the direction of the x-ray beam toward or away from the x-ray source.

[0016] Preferably, the common focus of the multiple channels of the collimator is located on the focal spot of the X-ray source.

[0017] Preferably, the common focal point of the multiple channels of the collimator has an effective size smaller than the focal spot of the X-ray source, eg an effective size between 10 μm and 50 μm in diameter, eg for small animal imaging.

[0018] In an embodiment, the channels of the collimator each have a diameter or maximum cross-sectional dimension between 1 μm and 10 μm, such as between 1 μm and 5 μm, eg for small animal imaging.

[0019] The collimator in the x-ray imaging device according to the present invention comprises a collimator body, or sometimes a plurality of collimator bodies, which by themselves or in combination define channels or through-holes for the x-rays. Between the channels is the x-ray blocking material of the collimator, so that there are some directions corresponding to the blocking material in which the x-ray source does not effectively emit radiation when the collimator is in its operating position. In order to compensate for this effect, and also in order to obtain information from those directions, it is very preferred that the collimator can be moved by an associated collimator mover configured to move the collimator. For example, the mover is implemented to move the collimator in two directions perpendicular to the direction of the x-ray beam. In practical embodiments, the displacement of the collimator does not need to be greater than (much greater than) the center-to-center distance of the channels, and in some embodiments can even be equal to or even less than said distance, for example half of said distance or approximately said distance.

[0020] Of course, positioning such a collimator in the x-ray beam path reduces the intensity of the x-rays, which can be compensated by extending the exposure time. It may be necessary to ensure that the object does not move during the extended exposure. However, it should be noted that the object being examined is often a tissue section or an anesthetized subject; in this case, motion blur will not occur during the extended exposure. This also indicates that the absolute size of real objects (e.g., organs or limbs of animals) is often much smaller than that of ordinary objects, i.e., intact animals.

[0021] In an embodiment, the x-ray imaging apparatus further comprises a collimator mover configured to move the collimator relative to the x-ray source in at least two directions (eg orthogonal directions) in a plane perpendicular to the main direction of the x-ray beam.

[0022] For example, the collimator mover is configured to provide only planar movement of the collimator relative to the x-ray source in at least two directions (eg orthogonal directions) in a plane perpendicular to the main direction of the x-ray beam. This solution has low complexity.

[0023] During acquisition of data associated with the one image, it is contemplated that the collimator mover is configured and operable to move the collimator to a plurality of different positions during the generation of an x-ray image. For example, the collimator may include an array of a plurality of channels spaced apart at center-to-center intervals on an incident side of the collimator in a direction perpendicular to the x-ray beam, wherein the collimator mover is configured and operable to move the collimator in the one direction between two acquisition positions, for example, during acquisition of data associated with the one image, from a spatial position of the x-ray source relative to the object to be examined, by a distance associated with the center-to-center distance, for example, by a distance between 0.5 and 2 times the center-to-center distance, for example, by 1 times the center-to-center distance.

[0024] In an embodiment, the collimator mover is configured to move and is operated to move the collimator over an area of a virtual sphere relative to the common focus.

[0025] In one embodiment, the collimator mover includes one or more piezoelectric actuators to provide movement of the collimator, for example configured and operable to move the collimator to a plurality of different positions during generation of an x-ray image during acquisition of data associated with said one image.

[0026] In one embodiment, the collimator has an array of multiple channels spaced apart at center-to-center intervals in a direction perpendicular to the x-ray beam on an incident side of the collimator, wherein the collimator mover is configured to move and is operated to move the collimator in the one direction through a distance related to the center-to-center distance, for example through a distance between 0.5 times and 2 times the center-to-center distance, for example, a distance of 1 times the center-to-center distance.

[0027] Specific embodiments are described in the dependent claims and in the following part of the description.

[0028] In an embodiment, the support frame is movable relative to the fixed main frame by a support frame drive.

[0029] In an embodiment, the object carrier is movable relative to the fixed main frame by an object carrier drive, preferably controllable independently of the movement of the support frame by the support frame drive.

[0030] In an embodiment, the support frame may be rotated by an associated drive about an axis extending through the object space (eg, a horizontal axis). This may allow, for example, the creation of a 3D imaging capability.

[0031] In an embodiment, the x-ray imaging apparatus further comprises a main frame (eg, a fixed main frame) mounted with a support frame, and an object carrier for carrying an object in the object space. In an embodiment, the support frame and the object carrier are rotatable relative to each other.

[0032] The object may be positioned on an object carrier, such as an optionally movable object table or other carrier, or may be held by one or more wires or the like.

[0033] The object carrier may be part of the x-ray imaging apparatus, or may be a different device that is removable from and insertable into the object space.

[0034] The support frame may be rotated relative to the fixed main frame, and / or the object carrier may be rotated relative to the support frame, for example to obtain 3D imaging capabilities.However, it is also useful to have only one imaging direction (ie only 2D imaging).

[0035] In some embodiments, the collimator is removably positioned in an operative position. Providing a removable collimator that can be removed from the path of the x-ray beam altogether allows for use of a "normal" x-ray source for relatively large objects or portions thereof, while the collimator is placed in its operative position if higher resolution is desired, such as for smaller details or objects in particular. In the operative position, in some embodiments, a collimator mover may be present to perform collimator motion as described herein for acquiring data associated with creating an x-ray image.

[0036] In an embodiment, the x-ray imaging apparatus further includes a collimator remover device for automatically moving the collimator between an operative position and a non-operative position, wherein the collimator is out of the x-ray beam. The automatic movement removes the collimator and, conversely, moves the collimator back to the operative position, enabling switching to different resolutions when examining the same object.

[0037] In an embodiment, the collimator comprises a cone-beam collimator having a plate body with a 2D array of holes in the plate body, wherein all holes are directed toward a common focal spot and form the plurality of channels of the collimator. This type of collimator is well known per se and is currently used close to an x-ray source to select a small portion of the focal spot for emitting an effective x-ray beam. Such a cone-beam collimator can be manufactured by making channels in a plate having a thickness of about 0.5 mm to several millimeters, for example by laser drilling or electrical discharge machining. Alternatively, holes can be punched or otherwise provided in a plurality of thin plates having a thickness of, for example, 0.1 mm, which, when stacked, together form the channels of the collimator.

[0038] In one embodiment, the collimator comprises a cone-beam collimator having a collimator plate with a 2D array of holes extending therethrough, wherein the holes all point toward a common focus and form the plurality of channels of the collimator. In one embodiment, the holes each have a diameter between 1 μm and 10 μm, for example, between 1 μm and 5 μm.

[0039] In an alternative or supplemental embodiment, the collimator comprises a group consisting of a first collimator body and a second collimator body arranged in series with the first collimator body, wherein the first collimator body comprises a plurality of first holes therein, wherein the second collimator body comprises a plurality of second holes therein, and wherein the first holes and the second holes together form the plurality of channels of the collimator.

[0040] In one embodiment, a collimator includes a first collimator body and a second collimator body arranged in series with the first collimator body, wherein the first collimator body includes a first stack of spaced-apart first plates with respective first slit spaces therebetween, the first slit spaces oriented toward a common first imaginary line; and wherein the second collimator body includes a second stack of spaced-apart second plates with respective second slit spaces therebetween, the second slit spaces oriented toward a common second imaginary line, the first and second common imaginary lines intersecting at a common focus, such that the first and second slit spaces together form the plurality of channels of the collimator. This structure is somewhat similar to a slit-strip collimator and has the advantage of being easier to manufacture. The structure has channels that are generally square or rectangular, which can produce a portion of the image that is more suitable for a detector. For example, each collimator body is made by stacking a plurality (e.g., at least three) of x-ray opaque plates (e.g., gold or some other metal) with an x-ray transmissive plate, such as a plastic such as polystyrene, interposed between them. Another option is to take a piece of X-ray transparent material, create slits in it, for example by milling or laser machining, and then fill these slits with X-ray opaque material. Other production methods, such as 3D printing, are not ruled out.

[0041] There is no particular limitation on the manner in which the collimator or its collimator body(s) is moved relative to the x-ray source. Indeed, it is desirable to provide a motion that ensures that x-ray radiation from a sufficient number of angles is imaged through the object.

[0042] Preferably, the collimator mover is arranged to move the collimator during imaging in two different directions, preferably continuously, which directions are substantially perpendicular to the main direction of the x-ray beam, e.g. orthogonal to each other. Each of said movements may be through a distance that is related to the center-to-center distance between two adjacent channels in said direction, e.g. half of said distance, or approximately or exactly said distance, or a multiple of said distance.

[0043] In practice, it is desirable to move the collimator so that all radiation from the focal spot / focal volume, rather than radiation from the larger focal spot of the x-ray source, can pass through at least one channel of the collimator.

[0044] In each case, it may be possible to use a corresponding distance to the side of the x-ray source that is equal to the center-to-center distance minus the width of the channel.

[0045] Note that in certain embodiments, the movement of the collimator, or each of the one or more collimator bodies, by the collimator mover is performed on an imaginary sphere extending around the focal point, thus having the focal point as the center of a radius. This can be done, for example, given the spherical symmetry of the x-ray beam. With a strictly planar displacement of the collimator, the focal point will then move across the focal spot of the x-ray source, which may reduce resolution. In embodiments, the collimator and associated mover are configured to perform such spherical motion (e.g., on a geodesic grid across the sphere). This can be achieved by mechanical coupling between the motions, which then effectively moves in three dimensions, or by electronically controlling the individual motions in all directions.

[0046] The movement of one or more collimator bodies relative to the x-ray source can be performed in steps, for example in a "grid", where several images are first taken at a starting position in a first direction, and there are steps to move the collimator in a second direction through a portion of the desired total displacement. Thereafter, one step is taken in the first direction, and several images are taken again with a stepwise displacement in the second direction, and so on, until all desired steps in the first direction have been completed. For example, a 4×4 grid of steps will effectively provide good results, although any other number of steps may also be performed satisfactorily. Scans can also be performed in the second direction, i.e., imaging is continued while moving the collimator in the second direction, and after the scan is completed, a step is taken in the first direction, the scan is repeated, and so on.

[0047] In an embodiment, the first and second collimator bodies of the collimator are movable relative to each other and / or relative to the x-ray source at multiple positions relative to the x-ray beam, for example during acquisition of imaging data for creating a single x-ray image.

[0048] In an embodiment, the first collimator body and the second collimator body are mounted to each other as an integrated collimator body, wherein the integrated collimator body is movable relative to the x-ray source by a collimator mover as described herein.

[0049] In one embodiment, a first collimator body and a second collimator body are movable relative to each other and relative to an x-ray source, wherein a first collimator body mover is coupled to the first collimator body, and wherein a second collimator body mover is coupled to the second collimator body, each of the first collimator body mover and the second collimator body mover being configured to move the respective collimator bodies. For example, one or both of the first collimator body mover and the second collimator body mover are implemented as described herein.

[0050] In one embodiment, the collimator includes a group consisting of a first collimator body and a second collimator body arranged in series with the first collimator body, wherein the first collimator body includes a first stack of spaced-apart first plates with respective first slit spaces therebetween, the first slit spaces being directed toward a common first imaginary line, and wherein the second collimator body includes a second stack of spaced-apart second plates with respective second slit spaces therebetween, wherein the second slit spaces are directed toward a common second imaginary line, the first common imaginary line and the second common imaginary line intersecting each other at a common focus such that the first slit spaces and the second slit spaces together form the plurality of channels of the collimator, and wherein the first collimator body and the second collimator body are movable relative to each other and relative to an x-ray source, wherein a first collimator body mover is connected to the first collimator body, and wherein a second collimator body mover is connected to the second collimator body, the first collimator body mover and the second collimator body mover being configured to move the respective collimator bodies in a direction generally perpendicular to the slits of the respective collimator bodies. For example, one or both of the first collimator body mover and the second collimator body mover are implemented as described herein.

[0051] In an embodiment, the collimator mover can move one of the first and second bodies one step at a time in the corresponding direction, and then between two subsequent steps, move the other collimator body in another direction (e.g., vertical direction) by another mover while making x-ray images all the time.

[0052] The present invention also relates to a combination of an x-ray source and a collimator, the x-ray source being configured for use in an x-ray imaging apparatus for producing an x-ray image of an object, the x-ray source being configured to emit an x-ray beam having a main direction from a focal spot into an object space of the x-ray imaging apparatus, the collimator being arranged proximate to the x-ray source and in a path of the x-ray beam from the x-ray source to the object to be examined, the collimator comprising one or more collimator bodies defining a plurality of channels of the collimator, the channels having respective center directions defining a common focal point of the collimator at a side of the x-ray source, the channels preferably being a 2D array of channels viewed in a plane perpendicular to the main direction of the x-ray beam. It will be appreciated that the combination may be further provided with one or more of the additional features discussed herein.

[0053] The invention also relates to a method for imaging an object by means of an x-ray imaging device as described herein.

[0054] The present invention also relates to a method for retrofitting an x-ray imaging device for producing an x-ray image of an object, the x-ray imaging device comprising:

[0055] a support frame to which the x-ray source and the x-ray detector are connected,

[0056] wherein the x-ray source and the x-ray detector define between them an object space for an object to be inspected,

[0057] The x-ray source is configured to emit an x-ray beam having a main direction from a focal spot into the object space,

[0058] The x-ray detector includes a pixel array sensitive to the x-ray radiation,

[0059] The method comprises the step of arranging a collimator close to the x-ray source and in the path of the x-ray beam between the x-ray source and the object to be examined, the collimator comprising one or more collimator bodies defining a plurality of channels of the collimator, the channels having respective central directions defining a common focus of the collimator at the sides of the x-ray source, the channels preferably being a 2D array of channels seen in a plane perpendicular to the main direction of the x-ray beam, the collimator creating an effective focal spot smaller than the focal spot of the x-ray source.

[0060] The present invention also relates to a method for reducing the effective focal spot of an x-ray source in an x-ray imaging device, wherein the method comprises the steps of arranging a collimator close to the x-ray source and in the path of the x-ray beam between the x-ray source and the object to be inspected, the collimator comprising one or more collimator bodies defining a plurality of channels of the collimator, the channels having respective center directions defining a common focus of the collimator on the side of the x-ray source, the channels preferably being channels of a 2D array seen in a plane perpendicular to the main direction of the x-ray beam, the collimator creating an effective focal spot smaller than the focal spot of the x-ray source. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The invention will now be explained with reference to several non-limiting example embodiments and the accompanying drawings, in which:

[0062] Figure 1 A first embodiment of an x-ray imaging apparatus according to the invention is shown very diagrammatically in a side view;

[0063] Figure 2 shows very diagrammatic details of different embodiments of an x-ray imaging apparatus according to the invention; and

[0064] Figure 3 Shown in more detail in a schematic perspective view Figure 2 collimator in . DETAILED DESCRIPTION

[0065] Figure 1 A first embodiment of an x-ray imaging device 1 according to the invention is shown very diagrammatically in a side view.

[0066] The x-ray imaging device 1 comprises a stationary main frame 2 , on which a movable, preferably rotatable, support frame 3 is mounted, for example in the form of a C-arm, schematically shown here, or in the form of a rotating gantry.

[0067] The support frame 3 is rotatable about an axis 5, eg about a single axis, eg as in a gantry imaging system, preferably at least in step mode by means of a support frame rotator 4. In a practical embodiment, the axis 5 is a horizontal axis.

[0068] An x-ray tube is indicated by reference numeral 6. Typically, the x-ray tube 6 comprises an anode and an emitter arrangement comprising a cathode for emitting an electron beam towards the anode onto a focal spot on the anode, e.g. comprising electron optics for focusing the electron beam onto the focal spot on the anode.

[0069] The x-ray tube 6 is provided with an x-ray window, for example a beryllium window 7 .

[0070] The object carrier 10 is configured to carry an object 11 to be inspected, such as a small animal, here a mouse.

[0071] The x-ray detector 8 is arranged for detecting at least a portion of the x-ray beam that has passed through the object 11 .

[0072] Reference symbol A denotes an object space between the x-ray tube 6 and the x-ray detector 8 , in which an object 11 to be inspected is usually placed.

[0073] The x-ray detector 8 comprises an array, eg a 2D array, of pixels 9 that are sensitive to x-ray radiation.

[0074] For example, the object carrier 10 comprises a horizontal table on which the object 11 to be inspected is placed.

[0075] The object carrier 10 is preferably movable between a retracted position outside the object space A and an imaging position within the object space A by means of an associated object carrier mover 12 , here a stage mover 12 .

[0076] Preferably, when the carrier 10 supports the object in the object space, the object carrier 10 can be moved by means of an associated object carrier mover 12 (here a stage mover 12) in one or more directions, for example in a plurality of orthogonal directions, such as in the x, y, z directions, e.g. as indicated by arrows D. These one or more directional movements can be performed before, during and / or after scanning the object with the device.

[0077] The computerized reconstructor reconstructs the imaging data and, in an embodiment, may be configured to generate three-dimensional (3D) volumetric image data indicative of the examination region and objects therein. The resulting volumetric image data may be processed by an image processor or the like to generate one or more images.

[0078] A general purpose computing system may be provided for use as an operator console and include output devices such as a display and input devices such as a keyboard, mouse, etc. Software resident on the console may allow the operator to control the operation of the imaging device, e.g., allowing the operator to start a scan, etc.

[0079] A collimator 13 is provided in front of the window 7 . The collimator 13 has a collimator body 14 with a through-channel 15 and is movable in the direction of arrow B by a collimator mover 16 .

[0080] The collimator remover 17 can remove the collimator 13 in the direction of arrow C from the emitted x-rays 18 .

[0081] The wire shaping and blocking device is marked "19".

[0082] The narrowed and more focused beam is indicated as 18 ′, and the focal point of the beam 18 ′ is labeled “ 20 ”.

[0083] In use, an object 11, such as a mouse, is provided on an object carrier or table 10 and moved into object space "A" by means of a table mover 12. By moving the table 10 in any one or more directions indicated by arrows D, the object 11 can be positioned as desired relative to the x-ray source 6 and detector 8, i.e., relative to the beam 18.

[0084] X-rays 18 are generated by an x-ray source 6 (in this case, for example, an x-ray tube) and are emitted, depending on the nature of the source 6, in a relatively thick beam 18 (for example, with a focal spot size between approximately 0.1 mm and 1.2 mm in diameter).

[0085] Using the collimator of the present invention, the coarse x-ray beam 18 emitted by the source 6 is clipped and shaped into a beam 18' that appears to originate from a much smaller effective focal spot defined by a focal point or focal volume 20. The effective focal spot or volume may have a size of, for example, 20-25 μm in diameter. Furthermore, the coarse radiation 18 is sent through a collimator 13 having a collimator body 14 having a through hole or channel 15.

[0086] In the example shown, the collimator is a cone-beam collimator in which there is one collimator body 14 and all the holes or channels are directed to the same focal point on the focal spot 20 .

[0087] Optionally, additional beam shaping and blocking means 19 are provided to block any surface radiation, which means 19 in principle do not extend much beyond the edge around the collimator body 14. The presence of such a simple edge, which can be as thick as the rest of the collimator body 14, ensures that no x-rays other than those in the beam 18' will pass through, without having to provide too many holes 15 in the edge of the collimator body 14.

[0088] In use of the x-ray imaging apparatus 1 , the collimator 13 may be moved relative to the source 6 by means of the collimator mover 16 , for example in the direction of arrow B. Note that the collimator 13 need not be moved more than the centre-to-centre distance between channels 15 in order to provide a complete image.

[0089] To improve accuracy, the collimator 13 is preferably moved on an imaginary sphere around the focal point 20 so that the effective position of the focal point 20 remains unchanged during imaging. The collimator mover and its control should then of course be arranged accordingly. This can be achieved by mechanical means or by increasing mobility in the third dimension and having the collimator mover 16 perform the desired combined spherical movement of the collimator 13 with the collimator body 14.

[0090] The collimator mover 16 may include one or more piezoelectric actuators to provide mobility. Such actuators can provide the required small displacements with high precision, reliability and repetition rate. However, other actuators, such as stepper motors, are not excluded.

[0091] A collimator remover 17 is shown as being provided for removing the collimator 13 from the x-ray beam 18 / 18'. In this case, the shaped beam 18' is then again replaced by "coarse" x-rays 18, for example for imaging and examining larger objects 11, or with higher intensity and correspondingly shorter exposure times. The collimator remover may comprise a coarser actuator than that used for the collimator mover 16, but it is also possible to combine the collimator mover and the collimator remover into one, for example using a device combining a piezoelectric actuator and a hinge or a linear actuator with a greater travel.

[0092] It is important to note that the figures are not drawn to scale. In particular, the size of the object space A, i.e., the distance between the x-ray tube 6 and the detector 8, is typically between approximately 200 mm and 600 mm. Conversely, the thickness of the collimator body 14 can practically be approximately 1-2 mm. Greater thickness may not further improve quality, but may make the fabrication of the aperture or channel 15 more difficult.

[0093] Furthermore, the number of channels 15 in the collimator body 14 will be (much) greater than the five shown here. The diameter of each channel 15 will in practice be several μm, for example between 1 μm and 10 μm. Together, they ensure that the focal spot 20 of the x-ray tube 6 will be effectively reduced to a focal volume pf of a few tens of μm, for example 25 μm wide. Similarly, the pixels 9 of the x-ray detector 8 are typically slightly smaller than 0.1×0.1 mm, for example 75 μm×75 μm, and their number is correspondingly higher than that shown in the figures. In all cases, these numbers are exemplary and are intended only to give an impression of actual values.

[0094] Furthermore, while the entire mouse 11, or at least a large portion thereof, can be examined in the present case, it is possible to bring the object 11 closer to the x-ray source 6, with the collimator 13 still positioned between the source 6 and the object 11. This generally allows for the examination of relatively smaller objects, or portions thereof. Due to the greater magnification (the ratio between the distance from the source 6 to the object 11 and the distance from the source 6 to the detector 8), achieving high resolution in the image becomes even more important. This is made possible by providing the collimator 13 between the source 6 and the object 11, which reduces the effective size (focal spot) of the x-ray source from, for example, 0.1 mm to 2 mm to, for example, 25 μm. Note that when bringing the object 11 closer to the source 6, it may be necessary to adjust the rotation of the frame 3 carrying the source 6 and detector 8 about the axis passing through the object 11 in order to obtain sufficient angular information. This adjustment may include sliding the support frame 3 in a direction perpendicular to the axis 5, so that the x-ray source 6 is closer to the axis 5 than the detector 8. Any other means of achieving the same effect are also possible.

[0095] The support frame 3 is shown here as rotatable relative to the main frame 2, e.g. about a horizontal rotation axis. However, it is also possible to have a non-rotatable fixed frame 3 and have the object carrier 10 rotate relative to the frame 3, or even not rotate at all and have only 2D imaging properties.

[0096] Figure 2 Shown are very diagrammatic details of different embodiments of an x-ray imaging device according to the invention, in particular the parts with the x-ray source and the collimator. In this text, as in all the figures, similar parts are denoted by the same reference numerals.

[0097] The detail shows a small part of the frame 3 with the x-ray source 6 , the protective but x-ray transparent window 7 and the different collimators 13 ′ having a focal point 20 on the focal spot of the x-ray source 6 .

[0098] The collimator 13' includes a set of first collimator bodies 21 and a second collimator body 22 arranged in series with the first collimator bodies 21. The first collimator bodies 21 include a first stack of spaced-apart first plates 26 with respective first slit spaces 28 between adjacent plates. These first slit spaces 28 are all directed toward a common first imaginary line F1. The second collimator body 22 includes a second stack of spaced-apart second plates 23 with respective second slit spaces 24 therebetween. These second slit spaces 24 are all directed toward a common second imaginary line F2. The plates of the bodies are non-parallel from one body to another, such that the first and second common imaginary lines intersect at a common focal point 20. As a result, the first and second slit spaces 28, 24, together form a plurality of channels of the collimator 13' that are focused on a common focal point 20, for example, of a very small size (e.g., much smaller than the focal spot of an x-ray source in the absence of the collimator 13').

[0099] The bodies 21 , 22 can be moved around their respective focal lines by respective movers 25 , 26 .

[0100] As schematically illustrated, the bodies 21 , 22 may be joined with curved or even spherical adjoining sides, for example allowing each body to be moved about a respective focal line, for example by a respective mover 25 , 26 .

[0101] Figure 3 The collimator 13 ′ is shown in more detail in a diagrammatic perspective view.

[0102] When from Figure 2 When the x-ray beam of the x-ray source 6 in is irradiated through the collimator 13 ′, the resulting source “seen” by the object is again a distinct focal spot 20 where the focal lines F1 and F2 intersect.

[0103] The number of plates shown here by way of example is arbitrary, and this number as well as the thickness of the plates 27 , 23 and the width of the slits 28 , 24 can be selected as required.

[0104] The first collimator body mover 25 is arranged, for example, in a direction substantially perpendicular to the main direction of the respective slit 28 (although particularly preferably on a spherical surface around the focus 20 or around the line F1, i.e. Figure 2 The first body 21 is moved in the direction indicated by “A” in the drawing, which enters / leaves the paper. Similarly, the second collimator body mover 26 may be arranged to move the second body 22 in the vertical direction of arrow B.

[0105] The movement of the two bodies 21, 22 can be coordinated, for example in a first step the first body 21 is moved and then in a further step a scanning or similar movement is performed on the second body 22, or vice versa. A faster oscillatory movement of the two bodies 21, 22 during imaging is also possible, as long as all desired or possible beam directions originating from the focal point are adequately imaged. Note that the first collimator body mover and the second collimator body mover can again comprise piezoelectric actuators or the like and can together be supplemented by a collimator remover (not shown) for removing the collimator 13', similar to Figure 1 Collimator remover 17 in.

[0106] The examples and drawings are given as illustrative explanations of the present invention only and do not limit the scope of the appended claims.

Claims

1. An x-ray imaging apparatus for producing an x-ray image of an object, comprising: a support frame to which the x-ray source and the x-ray detector are connected, wherein the x-ray source and the x-ray detector define between them an object space for an object to be inspected, The x-ray source is configured to emit an x-ray beam having a main direction from a focal spot into the object space, The x-ray detector includes a pixel array sensitive to the x-ray radiation, The x-ray imaging apparatus further includes a collimator arranged proximate to the x-ray source and in a path of the x-ray beam between the x-ray source and the object to be inspected, the collimator including one or more collimator bodies defining a plurality of channels of the collimator, the channels having respective center directions defining a common focal point of the collimator on a side of the x-ray source, wherein the collimator includes a group consisting of a first collimator body and a second collimator body arranged in series with the first collimator body, wherein the first collimator body includes a first stack of spaced-apart first plates with respective first slit spaces therebetween, the first slit spaces pointing to a common first imaginary line, and wherein the second collimator body includes a second stack of spaced-apart second plates with respective second slit spaces therebetween, wherein the second slit spaces point to a common second imaginary line, the first common imaginary line and the second common imaginary line intersecting each other at the common focal point such that the first slit spaces and the second slit spaces together form the plurality of channels of the collimator. 2 . The x-ray imaging apparatus of claim 1 , wherein the common focus of the plurality of channels of the collimator is on the focal spot of the x-ray source. 3 . The x-ray imaging apparatus of claim 1 , wherein the common focal point of the plurality of channels of the collimator has an effective size that is smaller than the focal spot of the x-ray source. 4 . The x-ray imaging apparatus of claim 1 , wherein the common focal spot of the plurality of channels of the collimator has an effective size of between 10 μm and 50 μm in diameter.

5. The x-ray imaging apparatus of claim 1 , wherein the x-ray source has a housing including an x-ray window from which the x-ray beam exits the x-ray source, wherein the collimator is arranged outside the window, close to the window.

6. The X-ray imaging apparatus according to claim 1, wherein: The x-ray imaging apparatus further includes a collimator mover configured to move the collimator relative to the x-ray source in at least two directions in a plane perpendicular to the main direction of the x-ray beam. 7 . The x-ray imaging apparatus according to claim 6 , wherein the collimator mover is configured to move the collimator over an area of a virtual spherical surface relative to the common focal point.

8. The x-ray imaging apparatus of claim 6, wherein the collimator mover comprises one or more piezoelectric actuators to provide movement of the collimator.

9. The X-ray imaging apparatus according to claim 1, further comprising a main frame, the support frame supporting the X-ray source and the X-ray detector being mounted to the main frame, the support frame being rotatable around a rotation axis relative to the main frame.

10. The x-ray imaging apparatus of claim 1, further comprising an object carrier configured to carry an object in the object space.

11. An x-ray imaging device according to claim 1, wherein the collimator is removably positionable in a position close to the x-ray source, wherein the imaging device includes a collimator remover device, the collimator remover device being configured to automatically remove the collimator from the position to a non-operating position outside the x-ray beam.

12. The x-ray imaging apparatus of claim 1, wherein the first collimator body and the second collimator body are movable relative to each other and / or relative to the x-ray source.

13. The x-ray imaging device of claim 1 , wherein the first collimator body and the second collimator body are mounted relative to each other as an integrated collimator body, and wherein the x-ray imaging device further comprises a collimator mover configured to move the integrated collimator body relative to the x-ray source in at least two directions in a plane perpendicular to the main direction of the x-ray beam.

14. The x-ray imaging apparatus of claim 1 , wherein the first collimator body and the second collimator body are movable relative to each other and relative to the x-ray source, wherein a first collimator body mover is connected to the first collimator body, and wherein a second collimator body mover is connected to the second collimator body, the first collimator body mover and the second collimator body mover being configured to move their respective collimator bodies.

15. The x-ray imaging apparatus of claim 1 , wherein the first collimator body and the second collimator body are movable relative to each other and relative to the x-ray source, wherein a first collimator body mover is connected to the first collimator body, and wherein a second collimator body mover is connected to the second collimator body, the first collimator body mover and the second collimator body mover being configured to move the respective collimator bodies in a direction substantially perpendicular to the slits of the respective collimator bodies.

16. Method for imaging an object by means of an x-ray imaging device according to claim 1.

17. The method of claim 16, wherein the collimator creates an effective focal spot that is smaller than the focal spot of the x-ray source.

18. A method for retrofitting an x-ray imaging device for producing an x-ray image of an object, the x-ray imaging device comprising: a support frame to which the x-ray source and the x-ray detector are connected, wherein the x-ray source and the x-ray detector define between them an object space for an object to be inspected, The x-ray source is configured to emit an x-ray beam having a main direction from a focal spot into the object space, The x-ray detector includes a pixel array sensitive to the x-ray radiation, wherein the method includes the step of arranging a collimator proximate to the x-ray source and in a path of the x-ray beam between the x-ray source and the object to be examined, the collimator including one or more collimator bodies defining a plurality of channels of the collimator, the channels having respective center directions defining a common focal point of the collimator on a side of the x-ray source, wherein the collimator includes a group consisting of a first collimator body and a second collimator body arranged in series with the first collimator body, wherein the first collimator body includes a first stack of spaced-apart first plates having respective first slit spaces therebetween, the first slit spaces being directed toward a common first imaginary line, and wherein the second collimator body includes a second stack of spaced-apart second plates having respective second slit spaces therebetween, wherein the second slit spaces are directed toward a common second imaginary line, the first and second common imaginary lines intersecting each other at the common focal point such that the first and second slit spaces together form the plurality of channels of the collimator, the collimator creating an effective focal spot that is smaller than the focal spot of the x-ray source.

19. A method for reducing the focal spot of an x-ray source in an x-ray imaging apparatus, wherein the method comprises the steps of arranging a collimator close to the x-ray source and in a path of the x-ray beam between the x-ray source and an object to be examined, the collimator comprising one or more collimator bodies defining a plurality of channels of the collimator, the channels having respective center directions defining a common focal point of the collimator on the sides of the x-ray source, wherein the collimator comprises a group consisting of a first collimator body and a second collimator body arranged in series with the first collimator body, wherein the first collimator body comprises an intermediate a first stack of spaced-apart first plates having respective first slit spaces therebetween, the first slit spaces pointing towards a common first imaginary line, and wherein the second collimator body comprises a second stack of spaced-apart second plates having respective second slit spaces therebetween, wherein the second slit spaces point towards a common second imaginary line, the first common imaginary line and the second common imaginary line intersecting each other at the common focus such that the first slit spaces and the second slit spaces together form the plurality of channels of the collimator, the collimator creating an effective focal spot that is smaller than the focal spot of the x-ray source.

Images