X-ray scanning with selectable range

Abstract

An X-ray scanning system includes: an X-ray source configured to output a beam of source X-rays; a chopper wheel rotatably mounted and arranged relative to the X-ray source so as to receive the beam, the chopper wheel configured to block X-rays of the beam and defining a set of beam apertures that pass there through a portion of the beam of source X-rays to form a scanning beam of source X-rays; a motor mechanically coupled to the chopper wheel; and a controller configured to control the motor to effect rotation of the chopper wheel over a selectable chopper wheel angular range so as to cause the scanning beam of source X-rays to sweep over a selectable scanning angular range for scanning a target.

Description

20098.0040WQU1Atorney Docket: 20098.0040WOU1X-Ray Scanning with Selectable RangeRELATED APPLICATION

[0001] The present Application claims the benefit of U.S. Provisional Application Serial No. 63 / 759,745, filed February 18, 2025. The foregoing application is hereby incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present invention relates to systems, apparatuses, and methods for scanning and imaging, such as using handheld scanners, via penetrating radiation such as X-rays. More particularly, the application relates to systems, apparatuses, and methods that include chopper wheels that can be used to generate a scanning beam of penetrating radiation such as X-rays. Further, the present invention relates to use of such systems, apparatuses, and methods for backscatter imaging applications and for X-ray fluorescence (XRF) measurements.BACKGROUND

[0003] X-ray backscatter imaging has been used for detecting concealed contraband, such as drugs, explosives, and weapons, since the late 1980’s. Unlike traditional transmission X-ray imaging, which creates images by detecting the X-rays penetrating through a target object, backscatter X-ray imaging uses reflected or scattered X-rays to generate a backscatter X-ray image. Typically, an X-ray fan beam is '‘chopped” into a pencil beam by a rotating “chopper wheel” that defines therein apertures such as slit openings or other types of openings of different shapes. The chopper wheel is usually one of three basic types: a rotating disk (“disk” chopper wheel), a rotating wheel (“hub-and-spoke” chopper wheel), or a rotating hoop (“hoop” chopper wheel).

[0004] Handheld backscatter X-ray imagers have been available since 2014 and have used rotating disk chopper wheels. More recently, a handheld backscatter imager using a rotating hoop and a transmission anode X-ray tube with a non-zero extraction angle of the X-rays from the anode has been developed.SUMMARY

[0005] Existing handheld imaging systems, for example, have detected fluorescence X-rays (X-ray fluorescence, or XRF) emitted from concealed lead targets that are excited by an irradiating X-ray beam, for example. This can be useful to alert an operator to a presence of drug concealment traps, for example. The X-ray beam on these imaging devices can scan linearly as the imaging device is translated across the target object being inspected, such that the beam is raster scanned across the object in two dimensions. A limitation of existing approaches is that for smaller concealed target items, the beam is only irradiating the target item for a small fraction of the total beam scan, therefore diluting the XRF signal from the suspect item with a larger fraction of Compton backscatter X-rays, which form a significant background compared to the XRF signal that is desired to be measured. Furthermore, certain types of metal targets, such as very small quantities of tin concealed behind a 1.5cm thick sheet of dry wall in an electronic device, for example, produce XRF signals that are very difficult to detect with existing methods and systems. In the beam scanning mode described above for a backscatter X-ray imaging system, the K-shell X-rays detected from the tin may be only barely visible above the Compton scatter background from the dry wall, for example.

[0006] When using an X-ray scanner for inspection such as imaging, it would be advantageous to be able to use X-ray fluorescence (XRF) analysis more effectively to identify more accurately suspect objects detected in backscatter or transmission X-ray images.

[0007] According to embodiments described herein, it is advantageous to have the option of switching scan modes between a scanning pencil beam, for imaging, and a stationary beam for XRF interrogation of a suspect item. By switching to the stationary beam mode, the beam can be focused onto an area of a target where a suspect item is suspected to be concealed, enhancing the XRF signal emitted by the suspect item and correspondingly reducing the Compton backscatter background under the XRF peaks.

[0008] Further according to certain embodiments described herein, a disk or hoop chopper wheel in a scanning-beam handheld X-ray imager can be rapidly stopped such that a fixed beam can be focused onto concealed suspect target item. Still further according to certain embodiments, an X-ray beam may be “dithered’' over a smaller region of the inspected target object so as to increase XRF signal of a suspect itemcompared with Compton backscatter background signal. Various embodiments further allow a particular aperture in the chopper wheel (e.g. disk or hoop) to be selected so that a fdtered or unfiltered aperture can be used to form the scanning beam.

[0009] According to a first specific embodiment, an X-ray scanning system includes:a) an X-ray source configured to output a beam of source X-rays;b) a chopper wheel rotatably mounted and arranged relative to the X-ray¬ source so as to receive the beam of source X-rays, the chopper wheel comprising an X-ray attenuating material configured to block X-rays of the beam of source X-rays, the chopper wheel defining a set of beam apertures of which each aperture is configured to pass there through a portion of the beam of source X-rays to form a scanning beam of source X-rays;c) a motor mechanically coupled to the chopper wheel; andd) a controller configured to control the motor to effect rotation of the chopper wheel over a selectable chopper wheel angular range so as to cause the scanning beam of source X-rays to sweep over a selectable scanning angular range for scanning a target.

[0010] According to a second specific embodiment, an X-ray imaging apparatus includes:a) a holdable housing;b) an X-ray source mounted within the housing and configured to output a fan beam of X-rays; andc) a chopper wheel rotatably mounted within the housing and comprising an X-ray attenuating material configured to block X-rays of the fan beam, the hoop chopper wheel defining a set of beam apertures of which each aperture is configured to pass there through a corresponding angular portion of X-rays from the fan beam, wherein the chopper wheel can be operated in two or more of three operational modes selected from the group consisting of:i. rotation of the hoop chopper wheel causing scanning of the corresponding angular portion of X-rays, and ii. selectively irradiating a beam aperture with X-rays from the fan beam wherein the chopper wheel is stationary, causing thecorresponding angular portion of X-rays from the fan beam to be stationary, andiii. selectively irradiating a beam aperture with X-rays from the fan beam wherein the chopper wheel is rotated through a small angular range, causing the corresponding angular portion of X-rays from the fan beam to scan through a small angular range.

[0011] According to a third specific embodiment, a penetrating radiation scanning system includes:a) a penetrating radiation source configured to output a beam of source penetrating radiation;b) a chopper wheel rotatably mounted and arranged relative to the penetrating radiation source so as to receive the beam of source penetrating radiation, the chopper wheel comprising a penetrating radiation attenuating material configured to block penetrating radiation of the beam of source penetrating radiation, the chopper wheel defining a set of beam apertures of which each aperture is configured to pass there through a portion of the beam of source penetrating radiation to form a scanning beam of source penetrating radiation;c) a motor mechanically coupled to the chopper wheel; andd) a controller configured to control the motor to effect rotation of the chopper wheel over a selectable chopper wheel angular range so as to cause the scanning beam of source penetrating radiation to sweep over a selectable scanning angular range for scanning a target.

[0012] According to a fourth specific embodiment, a method of X-ray scanning includes:a) outputting abeam of source X-rays;b) blocking X-rays of the beam of source X-rays at a chopper wheel; c) passing a portion of the beam of source X-rays through a set of beam apertures defined by the chopper wheel to form a scanning beam of source X-rays; andd) controlling a motor mechanically coupled to the chopper wheel to effect rotation of the chopper w heel over a selectable chopper wheel angularrange so as to cause the scanning beam of source X-rays to sweep over a selectable scanning angular range for scanning a target.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 (prior art) is a perspective-view illustration, of an X-ray transmission scanning system utilizing a scanning beam of X-rays, showing principles applicable both to backscatter and to transmission X-ray scanning and imaging consistent with various implementations.

[0014] FIGS. 2A-2C (prior art) illustrate rotating disk, rotating wheel, and rotating hoop types of X-ray chopper wheels, respectively, that have been used for backscatter imaging systems.

[0015] FIG. 3 (prior art) is a plan-view diagram of a rotating disk chopper wheel, showing its radial slits and a region irradiated by a fan beam of X-rays.

[0016] FIG. 4 (prior art) is a perspective-view illustration of an X-ray scanning module in which an irradiating fan beam of X-ray radiation is incident on a surface of a tilted or "angled" disk chopper wheel at an angle substantially different from the normal.

[0017] FIG. 5 (prior art) is a perspective-view illustration of an “open-geometry ”-type disk chopper wheel assembly with scatter plates used in certain existing Viken Detection® handheld backscatter X-ray instruments.

[0018] FIG. 6 (prior art) is an illustration of an existing handheld X-ray scanner incorporating an open geometry -type disk chopper wheel assembly of the type illustrated in FIG. 5.

[0019] FIG. 7 (prior art) is a schematic block diagram illustrating an X-ray imaging apparatus having a hoop-type chopper wheel.

[0020] FIG. 8 (prior art) is a perspective-view diagram illustrating a scanning module with an in-line hoop chopper wheel.

[0021] FIG. 9 (prior art) is a perspective-view diagram illustrating a scanning module, along with an example placement of backscatter detectors relative to a hoop chopper wheel.

[0022] FIG. 10 (prior art) shows computer-simulated backscatter images of a line-pair phantom acquired with a prior-art Viken Detection® HBI™ handheld X-ray scanner with a disk chopper wheel compared to images acquired with hoop-ty pe chopper wheel assemblies w ith 1.0 mm square and 0.5 mm x 10 mm rectangular apertures (middle andlower images, respectively), all of which may be modified to include elements and implement methods according to embodiments.

[0023] FIG. 11 (prior art) is a perspective-view diagram illustrating a scanning module with an ‘'angled tube” configuration that can be particularly advantageous when used in various present embodiments.

[0024] FIG. 12 (prior art) is a profile-view diagram illustrating a component layout in embodiment X-ray scanning module that has an ‘'angled tube” configuration and is configured to be handheld.

[0025] FIG. 13A (prior art) is a profile-view illustration of an existing Viken Detection* HBI™ X-ray scanning instrument showing distance between a disk chopper wheel therein and a front of a housing of the instrument.

[0026] FIG. 13B (prior art) is a profile-view illustration of an X-ray scanning instrument with a hoop and a non-zero angle of extraction of X-rays from the anode of the X-ray tube X-ray source, showing distance between a hoop chopper wheel therein and a front of a housing of the instrument.

[0027] FIG. 14 (prior art) shows a handheld backscatter X-ray imager in sweeping beam mode being used to image and perform XRF analysis on a small suspect item (target) concealed behind a sheet of dry wall, exemplifying certain limitations of existing systems in XRF detection.

[0028] FIG. 15 (prior art) shows an example energy’ spectrum from an XRF analysis on a small item containing trace amounts of tin concealed behind a sheet of dry wall using the sweeping beam mode illustrated in FIG. 14.

[0029] FIG. 16 shows a handheld backscatter X-ray scanning system according to a current embodiment, operating in a stationary (or “dithering”) beam mode being used to perform enhanced XRF analysis on a small suspect item (target) concealed behind a sheet of dry wall.

[0030] FIG. 17 shows an example energy’ spectrum from an XRF analysis on a small item irradiated with a 160kV X-ray beam containing trace amounts of tin concealed behind a sheet of dry wall using the stationary beam mode of FIG. 16.

[0031] FIG. 18 shows a disk chopper wheel and X-ray fan beam used in an implementation of an embodiment of the present disclosure for creating a stationary beam wi th a backscatter imager containing a chopper disk by controlling a motor driving thedisk chopper wheel such that a radial slit formed by the disk chopper wheel is centered in a fan beam of source X-rays.

[0032] FIG. 19 shows the stationary scanning beam of source X-rays created using an implementation of an embodiment having the features of FIG. 18, with the additional capability of being “dithered” over the target object; a controller, not show n in FIG. 19, controls a motor, not shown in FIG. 19, to effect rotation of the disk chopper w heel in alternating angular directions so as to cause the scanning beam of source X-rays to sweep in a dithering manner

[0033] FIG. 20 shows an advantageous hoop chopper wheel X-ray scanning module that may be used in connection with the present embodiments for causing a scanning beam of source X-rays to be stationary with a backscatter imager containing a hoop chopper wheel by centering an aperture of the hoop in the fan beam of source X-rays.

[0034] FIG. 21 shows the stationary beam created from the X-ray scanning module shown in FIG. 20, with the additional capability of being “dithered” over the target object.

[0035] FIG. 22 (prior art) shows an existing handheld backscatter imaging system that also has a detector arm for creating transmission images, which can be included in the present embodiments.

[0036] FIG. 23 show s an example energy spectrum from an XRF analysis on a small item irradiated with a 160kV X-ray beam containing trace amounts of tin concealed behind a sheet of dry wall using the stationary beam mode of FIG. 16, showing a difference between beam filtration and no beam filtration, according to implementations of the present embodiments.

[0037] FIG. 24 show s another example energy spectrum from an XRF analysis on a small item irradiated with a 160kV X-ray beam containing trace amounts of tin concealed behind a sheet of drywall using the stationary beam mode of FIG. 16, showing a difference between beam filtration (with a thicker filter than in FIG. 23) and no beam filtration, according to implementations of the present embodiments.

[0038] FIG. 25 is a schematic diagram illustrating an X-ray scanning system according to a first specific embodiment of the present disclosure, which may also be used in connection with an X-ray imaging system according to a second specific embodiment of the present disclosure.

[0039] FIG. 26 illustrates various optional features of an X-ray scanning system, an X-ray imaging apparatus, a penetrating radiation scanning system, and a method of X-ray scanning according to first, second, third, and fourth specific embodiments of the disclosure.

[0040] FIG. 27 is a flow diagram illustrating a procedure for X-ray scanning corresponding to a method of X-ray scanning according to an embodiment of the present disclosure.

[0041] The foregoing will be apparent from the following more particular description of example embodiments, as illustrated in the accompanying drawings, in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments.DETAILED DESCRIPTION

[0042] Definitions

[0043] As used in this description and the accompanying claims, the following terms shall have the meanings indicated, unless the context otherwise requires:

[0044] A '“set” includes at least one member.

[0045] “Target object,” “target,” and “object” are used interchangeably herein and refer to a subject that may be scanned by an X-ray scanner for imaging, for X-ray analysis, for another X-ray scanning application, or for a combination of these purposes.

[0046] “Holdable” means capable of being held and of a size and character that makes holding during scanning use possible by a human, a robot, or a drone. “Holdable” optionally includes “mountable” when a human, robot, or drone performs the “holding.” “Holdable” may be selected from the group consisting of hand holdable, arm holdable, robotically holdable, robotically mountable, articulated-arm-holdable, drone holdable, drone mountable, and combinations thereof.

[0047] Principles of Existing Systems for an Understanding of the Scope of the Present Embodiments

[0048] Referring to FIG. 1 (prior art), a diagram illustrates basic principles of backscatter imaging in reference to a transmission imaging system 100. The system 100 uses a scanning X-ray beam in a manner similar to a backscatter imaging system. A standard X-ray tube 102 generates source X-rays 104 that are collimated into a fan beam106 by a slit aperture in attenuating plate 108. The fan beam 106 is then “chopped'’ into a scanning pencil beam 110 by a rotating “chopper wheel” 12 defining slit apertures (which may also be referred to herein as “slits”) 114 therein. The scanning pencil beam 110 thus scans over target object 116. A target object is also referred to herein as a “target.” In this specific example, the target object 116 is suitcase on a conveyor 118 being imaged as the chopper wheel 112 rotates with a rotation 120.

[0049] In the transmission imaging system 100 as illustrated. X-rays of the scanning pencil beam 110 that are transmitted through the target 116 are detected by a transmission X-ray detector 122, which outputs a signal via a signal cable 124 to a monitor 126, which in turn shows an image 128 of contents of the target 116. In the same ty pe of system, while not shown in FIG. 1, backscatter X-ray detectors may be positioned to detect X-rays from the pencil beam 110 that are scattered by the target 116 in a general or specific backward direction, such as in a vicinity between the target 1 16 and the chopper wheel 112. An intensity of the X-rays scattered in the backwards direction may be thus recorded by one or more large-area backscatter X-ray detectors (not shoyvn in FIG. 1) as a function of the position of the irradiating beam. In the case of backscatter detectors, it can be advantageous to use large-area detectors in order to detect the greatest number of X-rays scattered in various specific backward directions. By moving the object through the plane containing the scanning beam, either on a conveyor 118 or under its own power, a tw o-dimensional backscatter image of the object may be obtained.

[0050] Referring to FIGS. 2A-2C (prior art), with further reference to FIG. 1, illustrations of three different X-ray scanning modules are provided including three respective types of existing X-ray chopper wheels. All of these X-ray chopper wheels are used for generating a scanning pencil beam from a substantially stationary wide X-ray beam emanating either directly from an X-ray tube 202 or from the X-ray tube 202 and through an intermediary collimation plate such as the collimation plate 108 of FIG. 1, for example. The chopper wheel of existing X-ray backscatter imaging systems usually is one of three basic types: a rotating disk chopper wheel (w hich may also referred to herein as a “disk” or “disk chopper wheel”) 212a, a rotating wheel chopper wheel (which may also be referred to herein as a "hub-and-spoke” chopper wheel) 212b, or a rotating hoop chopper wheel (which may also be referred to herein as a “hoop” chopper wheel) 212c. The three types are shown in FIGS. 2A, 2B, 2C, respectively, in X-ray scanning modules 200a, 200b, 200c, respectively. The chopper wheels 212a, 212b, 212c can be rotatablymounted in various ways that are known in the art of X-ray scanning. FIG. 2A illustrates one way of causing a chopper wheel to rotate, wherein the disk chopper wheel 212a is coupled to a shaft of a motor 230. Slits 214 (also referred to herein as "slit apertures / ’ for example) defined within the disk chopper wheel 212a serve a purpose similar to that of the slits 114 in FIG. 1. A fan beam 206 from the X-ray tube 202 irradiates the rotating disk 212a. The rotating wheel 212b of FIG. 2B includes hollow radial spokes 236 that allow X-rays to pass there through to create a scanning pencil beam. The rotating hoop chopper wheel 212c of FIG. 2C includes apertures 238 defined in the hoop to allow X-rays from the fan beam 206 to pass there through to output the scanning pencil beam as the hoop chopper wheel 212c rotates.

[0051] Various benefits and disadvantages of each type of chopper wheel are summarized below.

[0052] Rotating Disk.

[0053] Referring to FIG. 3 (prior art), with further reference to FIGs. 1 and 2A-2C, an example rotating disk (or disk chopper wheel) 312 illustrated, which is typical of designs used in the earliest X-ray imaging systems. Initially, the rotating disk was used to create a digital transmission X-ray imaging system, such as the system 100 illustrated in FIG. 1. Then backscatter imaging was added by incorporating additional backscatter detectors into the system. The disk chopper wheel 312 design includes a disk of attenuating material 316, configured to block source X-rays, such as lead or tungsten, with a series or radial slits 314 defined therein, which allow X-rays to pass through. The disk chopper wheel 312 is irradiated with a fan beam of X-rays 306. The intersection of the fan beam 306 with a radial slit 314 allows a “pencil beam” of X-rays, such as the pencil beam 110 in FIG. 1, to pass through. As the disk rotates with the rotation 120, the pencil beam of X-rays scans within a plane of the incident fan beam, with the scan direction defined by a line of sight from a focal spot of an X-ray tube (not illustrated in FIG. 3) through the irradiated slit 314. If the fan beam is vertical, then the pencil beam scans up and down. Alternatively, if the fan beam is oriented horizontally, then the pencil beam scans from side to side as the disk chopper wheel rotates. An X-ray chopper wheel of this design has been used in baggage scanning systems, which can operate at an X-ray endpoint energy of between 120kV and 180kV. The first two systems used an aluminum wheel, with a ring of lead providing the attenuating material in the region w here the disk intersects the irradiating fan beam. Four radial slits in the lead with slit edges defined by tungsten“jaws” create four sweeping pencil beams per full rotation of the disk chopper wheel. Alternatively, a solid tungsten disk with slits machined into it can be used.

[0054] A disk chopper wheel can be normally irradiated, as shown in FIG. 2A. in which a center of the fan beam 206 irradiates the rotating disk 212a at a substantially perpendicular angle w ith respect to a surface of the rotating disk 212a.

[0055] Referring to FIG. 4 (prior art), with further reference to FIGs. 1-3, an alternative X-ray scanning module 400 is illustrated. The module 400 is a more recent modification of the X-ray scanning module 200a of FIG. 2A, w hich has been modified in the X-ray scanning module 400 in a “tilted chopper wheel” (also referred to as an “angled chopper wheel”) configuration to significant advantage. The X-ray scanning module 400 can be a particularly compact and relatively low -weight X-ray scanning module. This design is particularly advantageous in mobile scanning device applications, as it allows a smaller and lower-cost motorized vehicle with a lower maximum chassis load limit to be used. In a larger, vehicle- or cart-based mobile scanning system, it also allows a vehicle, trailer, or cart that supports the X-ray scanning module to be smaller, lighter, and more maneuverable. Thus, where the embodiments described herein may not have even been feasible or desirable previously, given the weight, expense, and difficulty of handling two massive chopper wheels in a given system, or one such massive chopper wheel on a mobile conveyance, the tilted design can solve the long-standing associated problems. Tilted disk chopper wheels are described more fully in U.S. Patent No. 10,762,998, which is hereby incorporated by reference herein in its entirety. This chopper wheel assembly is compact, and by tilting the disk, the assembly enables a disk chopper wheel design to be used more easily at X-ray energies above 200kV. The compactness and low w eight of the tilted disk chopper wheel X-ray scanning module makes it ideal to be used on a mobile platform, and especially for a mobile dual-sided inspection system for embodiment X-ray scanning modules, systems, and methods described herein.

[0056] FIG. 4 particularly illustrates an orientation of a fan beam 406 output from the X-ray tube 202 and the disk chopper wheel 212a in greater detail. The X-ray tube 202 is oriented with an axis in the Y direction. The fan beam 206 of source X-rays that are output from the X-ray tube 202 is oriented in the X-Z plane (the X-Z plane contains the fan beam 206). The plane of rotation of the chopper disk lies at an oblique nonperpendicular angle 0 to the X-Z plane. The scanning pencil beam 110 also is scanned in the X-Z plane, i.e., the beam plane, as the chopper disk rotates. The disk chopper wheel212a includes a rim 434 and center 432, and the slits 214 are oriented to extend radially toward the rim and center. The rotating disk chopper wheel 212a is rotated by means of the motor 230.

[0057] The chopper disk 212a is not oriented in either the X-Z plane or the X-Y plane, but, rather, in a disk plane that is at an angle 0 with respect to the beam plane (X-Z plane) of the fan beam 206. The disk plane can also be referred to as a plane of rotation (or rotational plane) of the chopper disk 212a, because the disk remains parallel to this plane as it rotates. The disk plane can be parallel to the X axis. By positioning the plane of the rotating disk at an acute (substantially non-perpendicular) angle 0 to the plane of the fan beam, the actual thickness of the disk can be reduced by a factor F = 1 / sin(0) while keeping the disk’s effective thickness the same. As used herein, ‘‘substantially nonperpendicular” indicates that the angle 0 is small enough to increase effective thickness significantly, such as increasing effective thickness by more than 25%, more than 50%, more than 100% (an effective thickness multiplier of 2), more than 200%, or more than 400%.

[0058] The rotating disk is the only chopper wheel type that has been used in handheld backscatter X-ray imaging systems prior to this application. Available 140kV systems all use a normally irradiated, rotating tungsten disk defining four slits.

[0059] Rotating Wheel.

[0060] The second type of the “chopper wheel” was developed for use in a mobile backscatter imaging platform that operates at an X-ray endpoint energy of 450kV. At these X-ray energies, a rotating disk of the standard normally irradiated design would have to be much too thick to provide enough attenuation for the incident X-rays. Thus, that solution included designing a large wheel with the X-ray tube located at its center. Hollow radial “spokes” 236. as illustrated in FIG. 2B, allow the X-rays to escape. As the wheel rotates about the stationary X-ray tube 202, scanning pencil beams of X-rays are emitted, which can scan a target object to be imaged. Enough shielding can then be incorporated into the hub of the wheel to provide the required attenuation. A problem with the rotating wheel or “hub and spoke” design was its sheer size and weight (the wheel had a diameter of several feet), and its maximum rotation speed is a few hundred rotations per minute. Because the X-ray tube is located inside the hub of the wheel, a bipolar X-ray tube can be used. However, the bearings supporting the wheel must have a20098.0040WQU1diameter larger than that of the X-ray tube, and large bearings are inherently expensive and typically have a much lower maximum rotation speed.

[0061] Rotating Hoop.

[0062] A third type of chopper wheel that has been used in backscatter imaging systems is the rotating hoop, as exemplified by the rotating hoop 212c of FIG. 2C. These were first used for a baggage scanner designed for enhanced detection. This mobile scanner system operates at only 225kV, which is half the endpoint energy of the earlier 450k V system. Unlike the 450kV X-ray tube, the 225kV tube has a unipolar design, which allows it to be used inside a rotating hoop chopper wheel. The hoop chopper wheel design includes a rotating hoop of aluminum or steel, with a band of highly attenuating material (such as lead) located in the outer rim. A fan beam of radiation emitted from the X-ray tube located inside the hoop is incident on the inner surface of the hoop rim. The apertures 238 in the attenuating material in the rim allow the X-rays to pass through, creating a beam of X-rays that sweeps across the object being imaged as the hoop rotates. An advantage of this design over the wheel is that it can have smaller bearings and can typically spin faster. In existing hoop designs, all the shielding is in the rim, typically yielding a high moment of inertia and creating large stresses in the hoop material.

[0063] Handheld X-Ray Imagers.

[0064] Handheld backscatter X-ray imagers have been available beginning with a 70kV version. The first higher-energy 120kV model capable of imaging objects through steel (the HBI-120) was developed by Heuresis Corporation (now Viken Detection® Corporation). A higher energy version operating at 140kV called the Nighthawk™ was available a few years later. A 140kV model was available later. All these systems use a rotating tungsten disk with four slits, which is normally irradiated by an incident fan beam from the X-ray source.

[0065] Referring to FIG. 5 (prior art), with further reference to FIGs. 1-4, a perspective-view illustration is provided for an existing “open geometry” disk chopper wheel assembly 500 that includes scatter plates that has been used in previous Viken Detection® handheld backscatter X-ray instruments, as described in U.S. Pat. Nos.10,770,195 and 11,200,998. The assembly 500 includes a disk chopper wheel 501 that is configured to rotate about a rotation axis 540. In the illustration of FIG. 5, the rotation axis 540 coincides with the Z axis for the coordinate system that is shown. The rotation axis 540 is perpendicular to a rotation plane of the disk chopper wheel 501. The rotationplane is parallel to the XY plane that is shown in FIG. 5. The disk chopper wheel 501 has a solid cross-sectional area in the rotation plane. The wheel 501 is configured to absorb X-ray radiation traveling in a direction 544 from an X-ray source (not shown in FIG. 5) that is received at a source side of the chopper wheel (the side where X-rays are first incident, traveling along the direction 544). The disk chopper wheel 501 defines radial slit openings (or “apertures’') 521 around the wheel, and these radial slit openings are configured to pass X-ray radiation from the source side of the wheel to an output side of the disk chopper wheel.

[0066] The assembly 500 further includes a source-side scatter plate 503 that has a solid cross-sectional area in a plane parallel to the rotation plane of the wheel. The source-side scatter plate 503 is configured to absorb X-ray radiation, and it defines an open slot therein that is configured to pass X-ray radiation. Advantageously, the solid cross-sectional area of the source-side scatter plate is substantially smaller than the solid cross-sectional area of the disk chopper wheel, providing for operation of the assembly with significantly reduced weight, even while maintaining X-ray confinement similar to that of existing disk chopper wheel assemblies that include a full shielding enclosure surrounding an entire disk chopper wheel.

[0067] The source-side scatter plate 503 is secured by a support structure 502a-b that secures the source-side scatter plate substantially parallel to the rotation plane of the disk chopper wheel with a source-side gap between the source-side scatter plate and the source side of the disk chopper wheel. While an output-side scatter plate is generally optional, the assembly 500 does include an output-side scatter plate 504 that is secured by the support structure 502a-b to be substantially parallel to the rotation plane of the disk chopper wheel, similar to the source-side scatter plate 503. The support structure maintains an output-side gap between the output side of the scatter plate and the disk chopper wheel. In alternative assemblies not illustrated, the source-side and output-side scatter plates may form a single solid piece, the two scatter plates of which are connected by a bridge over the top of the disk chopper wheel 501 in FIG. 5. In alternatives, such a bridge structure may also be formed of a high-Z material to enhance shielding.

[0068] The output-side scatter plate 504 has a solid cross-sectional area in a plane parallel to the rotation plane of the disk chopper wheel. The output-side scatter plate is configured to absorb X-ray radiation, yet it also defines an open slot therein that is configured to pass X-ray radiation that emanates through the source-side scatter plate 503and radial slits 521 in the chopper wheel. Advantageously, the solid cross-sectional area of the output-side scatter plate 504, like that of the input source-side scatter plate, is substantially smaller than the solid cross-sectional area of the disk, further providing for a lightweight assembly.

[0069] In the assembly 500, the support structure 502a-b is further configured to secure the disk chopper wheel 501 at the rotation axis 540. Advantageously, therefore, the support structure 502a-b performs both the functions of securing the chopper wheel and the functions of securing the source-side and output-side scatter plates 503 and 504, respectively. Further, in the assembly 500, it will be noted that the support structure includes the two portions 502a and 502b on the source side and output side of the chopper wheel, respectively. This provides a particularly robust and stable configuration that performs many needed support functions. However, in other assemblies, a support structure may be one-sided, and the chopper wheel and support structure may be secured and mounted separately, while still being secured with the source-side scatter plate being substantially parallel to the chopper wheel and having the appropriate gap between the source-side scatter plate and the source side of the chopper wheel.

[0070] Further in the assembly 500 in FIG. 5, the support structure 502a-502b includes an inner portion 572 that is configured to secure the disk chopper wheel 501 at the rotation axis 540 thereof, and the support structure 502b further includes radial spokes 542 that extend outward from the inner portion 572 and are configured to secure both the source-side scatter plate 503 and output-side scatter plate 504 with the appropriate alignment and gap with respect to the chopper wheel. The support structure 502a-b does this by means of hardware 546 that secures the two sides of the support structure 502a and 502b together while simultaneously securing the chopper wheel 501. as further illustrated in the exploded-view drawing of the assembly in FIG. 5. Accordingly, the source-side portion 502a and output side portion 502b of the support structure are configured to be connected together and to secure the disk chopper wheel between the two portions of the support structure.

[0071] The support structure 502a-b is formed of aluminum, advantageously, for lighter weight. In other embodiments, other materials may be used. Nonetheless, aluminum may be used advantageously because of low cost, sufficient rigidity and strength, and because the source-side and output-side scatter plates provide the desired shielding, while the support structure need not be relied upon for X-ray shielding.

[0072] The assembly 500 further includes an optional shield structure 505 that is configured to enclose the X-ray radiation in a region of travel between the X-ray source (e.g.. X-ray tube, not shown in FIG. 5) and the source-side scatter plate 503. The shield structure 505 may be formed of a high-Z material, for example, such as tungsten, lead, iron, or another high-Z material having sufficient thickness to prevent incident or scattered X-rays from being emitted outside of the device.

[0073] Referring to FIG. 6 (prior art), with further reference to FIGs. 1-5, an illustration is provided showing an existing handheld X-ray scanner 655 that incorporates an open-geometry-type X-ray disk chopper wheel assembly as shown in FIG. 5.Components of the scanner, such as an X-ray tube and the disk chopper wheel assembly 500 of FIG. 5, are mounted within a housing 630 of the handheld X-ray scanner 655. Various embodiment X-ray imaging apparatuses may be configured specifically for handheld operation, such as in FIG. 6. The scanner 655 can be carried and moved by a person via handles 657 to scan a vehicle, luggage, or other items flexibly to detect contraband, safety issues, etc.

[0074] As illustrated in FIG. 6, a hand 653 of a person holds the scanner 655, in this example via handles 657, and the scanner is directed at a vehicle wheel 651, an example target object for X-ray scanning for contraband. The X-ray scanner 655 is configured to produce a real-time image 655 of the vehicle wheel 651.

[0075] Other Advantages of Hoop Chopper Wheels, Both for Existing X-Ray Scanning Instruments and for Implementations According to the Present Embodiments

[0076] Handheld backscatter X-ray imagers have been available beginning with a 70kV version in 2014. The first higher-energy' 120kV model capable of imaging objects through steel was developed by Heuresis™ Corporation (now' Viken Detection® Corporation) and was first available in 2016. A higher-energy version operating at 140kV called the Nighthawk™ became available a few years later. Another 140kV imager became available in 2019. All these systems use a rotating tungsten disk with four slits (slit apertures), and the disk is irradiated at a normal angle by an incident fan beam from the X-ray source.

[0077] Many existing Viken Detection® handheld backscatter X-ray scanning instruments use an open-geometry' rotating disk chopper wheel with scatter plates as described in U.S. Patent Nos. 10,770,195 and 11,200,998 and in connection with FIGs. 5-6 of the present disclosure.

[0078] A disadvantage of using a disk chopper wheel in a handheld instrument is that the disk and associated shielding and collimators can take up much space and add substantial weight, which may be borne by an operator, often for extended periods of time. As an example, the chopper disk and associated pre-collimator and post-collimator shielding in the Viken Detection® HBI-120™ system weighs about 1.2 lbs.

[0079] Another disadvantage of using a disk chopper wheel is that, due to its potential size and highly attenuating materials, the disk is typically installed behind the backscatter detector assembly. This typically requires the disk to be installed at least one inch (and usually much more) behind a front face of the instrument. Due to divergence of the pencil beam as it exits the chopper disk assembly, the scanning pencil beam may be substantially wider than the slit apertures in the disk at a position where the beam exits the front face of the instrument. Since the imaging resolution of the instrument is determined by the width of the beam at the point it irradiates the target object, the image resolution may be degraded compared to what could be achieved if the disk were located right at the front face of the instrument, and not located behind the backscatter detectors, as described further hereinafter in connection with FIG. 13 A.

[0080] A disadvantage of using a disk chopper wheel in a handheld instrument is that the disk and associated shielding and collimators take up space and add substantial weight.

[0081] Accordingly, it is desirable to have a chopper wheel assembly that both reduces weight and provides higher resolution, especially for a handheld X-ray imaging device.

[0082] More recently, hoop chopper wheel assemblies have been used instead of disk chopper wheels in backscatter X-ray imaging instruments, and more particularly in handheld instruments but also in other types of instruments, such as robotically mounted or held or drone-mounted scanning applications, and even other scanning applications such as van-type or other vehicle mounted applications, cart-mounted applications, and transmission-imaging applications.

[0083] Referring to FIG. 7 (prior art), with further reference to FIGs. 1-6, a block schematic diagram is provided to illustrate a generalized example X-ray imaging apparatus 700 that may be advantageously incorporated as part of implementations of the present embodiments. The apparatus 700 includes a holdable housing 730, a hoop chopper wheel 712, and an X-ray source 702. The X-ray source 702 is mounted withinthe holdable housing 730 and is configured to output a fan beam of source X-rays 706. For convenience, it is noted that the fan beam 706 may be considered to have an extraction direction 707. defined as a center of the fan beam, as determined within a measurement tolerance or specified by a manufacturer, for example. The X-ray source may be a reflection-type X-ray tube, as illustrated in FIG. 2C. Nonetheless, use of a transmission-type X-ray tube as the X-ray source 702 has significant advantages that will become further apparent in view of the totality of the description and drawings.

[0084] The hoop chopper wheel 712 is rotatably mounted within the holdable housing 730 and it is formed of an X-ray attenuating material that is configured to block X-rays of the fan beam 706. Nonetheless, the hoop chopper wheel 712 also defines therein a set of beam apertures 738. As used herein, “set" denotes one or more. Each beam aperture of the set is configured to pass therethrough a corresponding angular portion 710 of X-rays from the fan beam 706. In this manner, rotation 720 of the hoop chopper wheel 712, which can be in the plane of the page through a center of the hoop chopper wheel 712 (not illustrated in FIG. 7) causes scanning of the corresponding angular portion 710 of X-rays, such as over the illustrated scanning direction 736. This is because, as the rotation 720 of the hoop chopper wheel 712 occurs, the corresponding angular portion 710 of the fan beam 706 that passes through the beam aperture 738 changes in direction over time.

[0085] The corresponding angular portion 710 of the X-rays should be understood to constitute a scanning pencil beam of source X-rays in this case. The scanning pencil beam will naturally diverge with distance from the beam aperture 738, as illustrated. Thus, to maximize resolution as much as practical, it can be helpful to cause the scanning beam to intersect with a target object as near as possible to a position where the corresponding angular portion 710 exits that holdable housing 730. As described further hereinafter, embodiments provide significant benefits in resolution by enabling the noted distance to be decreased.

[0086] Also illustrated in FIG. 7 is an example inner surface 732 and an example outer surface 734 of the hoop chopper wheel 712. These surfaces are depicted in FIG. 7 as being circular, smooth, and concentric for simplicity and convenience only.Nonetheless, in vanous embodiments, the outer surface 734 can have flat or other noncircular facets. Furthermore, the hoop chopper wheel 712 may be formed of segments that are configured to be attached together. Moreover, the hoop chopper wheel 712 may have features such as additional drilled holes, added weights, or other features useful forbalancing the wheel during rotation. Various other features that are optional for the hoop chopper wheel 712 will become apparent further throughout the remaining description.

[0087] Referring to FIG. 8 (prior art), with further reference to FIGs. 1-7, a perspective-view diagram is provided illustrating an X-ray scanning module with an inline hoop chopper wheel 812 that may be used in implementations of the present embodiments. The inner surface of the narrow rotating hoop 812 of X-ray attenuating material such as tungsten is irradiated by a fan beam 806 output from an X-ray source, specifically a transmission-type X-ray tube 802. The fan beam 806 is output in substantially the same plane as a plane of rotation of the hoop chopper wheel 812, centered vertically to irradiate a set of apertures 838. The apertures 838 defined in the hoop chopper wheel 812 allow some of the X-rays in the fan beam 806 to pass there through, creating a sweeping pencil beam of X-rays 810 that sweeps from side to side as the hoop rotates about the source. The apertures can be circular, ellipsoidal, or rectangular slits, as just a few examples. A high-voltage power supply 840 is included in order to power the tube with the high voltage necessary to accelerate electrons and produce X-ray radiation.

[0088] Referring to FIG. 9 (prior art), with further reference to FIGs. 1-8, a perspective-view diagram is provided illustrating the scanning module of FIG. 8, further including an example placement of backscatter detectors 938 relative to a hoop chopper wheel 812. This example configuration may be optionally used with embodiments of the present disclosure. FIG. 9 illustrates a significant advantage of using a hoop chopper wheel, especially for holdable embodiments. Namely, the hoop 812 can be made narrow enough so that the irradiated apertures 838 within the hoop can be located very’ close to a front of a housing that houses the tube 802 and hoop 812. adjacent to the detectors 938, without interfering with a backscatter detector assembly. This is illustrated further in FIG.12. This means that a beam width at the point that the beam exits the front of the instrument is almost identical to the aperture width, resulting in much higher resolution than can be achieved with the disk chopper assembly set back into the instrument. This advantage of hoop-based embodiments is made clearer in connection with FIG. 10 and FIGS. 13A-13B, for example.

[0089] Referring to FIG. 10 (prior art), with further reference to FIGs. 1-9, three computer-simulated backscatter images are show n. The images are of a line-pair phantom and are considered to be acquired with an existing handheld X-ray scanners. The upperimage is considered to be acquired using a Viken Detection® HBI™ handheld X-ray scanner with a disk chopper wheel. In contrast, the middle and lower images are considered to be acquired with Viken Detection® X-ray scanners having hoop chopper wheel assemblies with 1.0 mm square and 0.5 mm x 10 mm rectangular apertures, respectively. In FIG. 10, simulated backscatter X-ray images of a line pair phantom are shown for the prior-art HBI- 120™ system (top image) with the chopper disk assembly- shown in FIG. 6 compared with images obtained with a system with a hoop chopper assembly as shown in FIG. 9, with 1 mm square apertures (middle image) and 0.5 mm x 1.0 mm rectangular apertures (bottom image). It is readily apparent from FIG. 10 that the images obtained with the embodiment hoop chopper assembly apparatus can have much higher resolution than for the existing disk chopper wheel assemblies.

[0090] While the hoop chopper wheel assembly shown in FIG. 9 produces high-resolution images, the diameter of the hoop must be large enough in that particular embodiment to allow the hoop to rotate without interfering with the X-ray tube. For some holdable apparatuses such as handheld instruments, this can require using a hoop with a diameter of approximately 5 inches, which can make it challenging to package the chopper assembly into a compact, light-weight handheld instrument.

[0091] Referring to FIG. 11 (prior art), with further reference to FIGs. 1-10 an illustration is provided showing how- the fan beam emitted from the X-ray source transmission anode can be extracted in an extraction direction 1107 that forms an angle 1154 with respect to the long axis of the X-ray tube (for example, 45 degrees). The angle can be generally greater than 0 degrees, between 0 and 90 degrees, in a range of about 10 degrees to about 60 degrees, in a range of about 20 degrees to about 50 degrees, in a range of about 25 degrees to about 35 degrees, or in a range of about 25 degrees to about 35 degrees. In this context, '’about' ’ means to within a measurement tolerance for the angle. This can allow a smaller diameter hoop to be used, as shown in the example of FIG. 11. Specifically, FIG. 11 is a perspective-view7diagram illustrating a scanning module with an “angled tube” configuration that is particularly advantageous in embodiments. In this example (called the “angled tube” configuration), the hoop chopper wheel does not have to clear the entire length of the X-ray tube, allowing a considerably smaller hoop of approximately 3 inches diameter to be used. This makes it much easier to design the hoop into a compact footprint and saves considerable weight. The “long axis”of an X-ray tube, as used herein, is specifically the longitudinal axis 1152, which is the axis over which electrons are accelerated toward the anode of the tube to generate X-rays.

[0092] Referring to FIG. 12 (prior art), with further reference to FIGs. 1-11, an illustration provides an example of packaging a hoop chopper wheel in a handheld instrument. Specifically, FIG. 12 is a profile-view diagram illustrating an component layout in an example X-ray scanning module that has an “angled tube’' configuration and is configured to be handheld. A tungsten hoop 1218, about 5 mm wide and 3 mm thick and defining circular or rectangular beam apertures, is supported by an aluminum cup hoop support 1246 that is mounted onto a shaft supported by dual bearings 1244 and driven by a small electric motor 1242. The bearings 1244 can be mounted firmly to the X-ray source (tube) 1202 to ensure accurate alignment of the fan beam and hoop apertures. This is one example that illustrates how, in embodiments, a minimum distance 1249 between an outer surface of the hoop chopper wheel and a front of the apparatus housing 1248 can be made very small in order to enhance possible resolution. The minimum distance is measured from the front of the housing 1248 to the nearest point of the outer surface of the hoop chopper wheel. In other words, the distance 1249 may be considered as from an outer surface of the hoop chopper wheel adjacent to an aperture that is irradiated at a given time, to a front of the housing that may abut an external target object during a scan. The minimum distance in various implementations can be less than about 50 mm, less than about 30 mm, less than about 10mm, less than about 5 mm or between about 10 mm and about 1 mm. “About” in this context means within tolerance of measurement accuracy.

[0093] Referring to FIGs. 13A-13B (prior art), with further reference to FIGs. 1-12, illustrations compare existing handheld instruments having disk- and hoop-type chopper wheels, respectively. The advantages of an instrument the hoop chopper wheel assembly (FIG. 13B) are apparent. As noted above, a disadvantage of using a disk chopper wheel in a handheld instrument, as in FIG. 13A, is that the disk and associated shielding and collimators require much space and add substantial weight. The weight typically must be borne by the operator, often for extended periods of time. As an example, the chopper disk and associated pre-collimator and post-collimator shielding in the Viken Detection® HBI-120™ system weighs about 1.2 lbs.

[0094] Another disadvantage of using a disk chopper wheel is that, due to its size and highly attenuating materials, the disk must be installed behind the backscatter detector20098.0040WQU1assembly, as illustrated in FIG. 13A for the Viken Detection® HBI-120™ instrument. This typically requires the disk chopper wheel 501 to be installed with an outer surface 1334 thereof to be at least one inch (and usually much more) behind the front face 1348 of the instrument’s housing. Due to the divergence of the pencil beam as it exits the chopper disk assembly, the beam is substantially wider than the slit apertures in the disk by the time the beam exits the front of the instrument. Since the imaging resolution of the instrument is defined by the width of the beam at the point it irradiates the target object, the image resolution is degraded compared to what could be achieved if the disk were located right at the front of the instrument, and not located behind the backscatter detectors. Weight and potential resolution are also a significant issues for small robots and drones to which an X-ray scanning apparatus may be mounted for remote inspection of possibly dangerous items. Thus, this is an important issue facing a variety of holdable X-ray scanning tools.

[0095] Using the apparatus of FIG. 13B, the length of the handheld imager (in the center direction of the scanning pencil beam emission 810) is greatly reduced compared with FIG. 13 A, allowing the embodiment imager apparatus of FIG. 13B to be inserted into much smaller spaces. For example, the length of the instrument would now be short enough to allow the undercarriage of cars with even very small ground clearance to be scanned.

[0096] Regarding weight reduction, the disk chopper assembly of the prior Viken Detection® handheld instruments having disk chopper wheels may weigh approximately 1.2 pounds (lbs ), while the hoop chopper assembly (with the “angled tube configuration”) would weigh a little under 0.5 lbs., resulting in a weight savings of 0.7 lbs. This is a substantial weight reduction for a handheld instrument.

[0097] Description of Various Features of Present Embodiments

[0098] The existing chopper wheel assemblies for beam formation, as illustrated and described in connection with FIGs. 1-13, all create scanning beams of source X-rays that sweep linearly across the target object being inspected.

[0099] When performing X-ray imaging and X-ray fluorescence analysis of concealed items simultaneously with a handheld backscatter X-ray imaging apparatus, it is advantageous to be able to switch between beam scanning modes, consistent with the second specific embodiment of the present disclosure. The second specific embodiment, with various implementations, may be understood by those of ordinary skill in the art inreference to FIGs. 14-24 and the accompanying descriptions, together with the remainder of the present disclosure. A sweeping beam is advantageous for X-ray backscatter and transmission imaging, while a stationary, or almost stationary beam is advantageous for selectively performing XRF interrogation on a particular item of interest.

[0100] Referring to FIG. 14, with further reference to FIGs. 1-13B, a handheld X-ray backscatter imaging device 1400 is used to inspect an item of interest 1410 behind a sheet of drywall 1405. A scanning X-ray beam 1401 starts a sweep along direction 1430 and ends the sweep at 1402, which is a sweep or scan over the full scanning angular range for scanning a target as the chopper wheel (not shown in FIG. 14) rotates in given angular direction. Item of interest 1410 is only irradiated by the beam during a brief angular increment 1425 of the total beam sweep. During the other angular increments 1420, the beam is to either side of the item of interest. When the item of interest is irradiated by the beam during increment 1425, X-ray fluorescence X-rays characteristic of the item are emitted in all directions, and some are detected with an energy-resolving detector 1450. However, due to the larger angular increments 1420 of the beam sweep in which only the dry wall 1405 is irradiated, there is only a small XRF peak from the item of interest that is positioned on top of a large Compton backscatter background signal from the dry wall.

[0101] Referring to FIG. 15, with further reference to FIGs. 1-14, an example energy spectrum of detected X-rays is shown, in which a small object containing very small quantities of tin is concealed behind a 1.5cm thick sheet of dry wall. In the beam scanning mode, using the full angular range of the sweep of the X-ray beam 1402 as described in connection with FIG. 14, the K-shell XRF X-rays detected from the tin are barely visible above the Compton scatter background from the drywall.

[0102] Referring to FIG. 16, with further reference to FIGs. 1-15, an operation according to implementations of the present embodiments is illustrated for selectively allowing imaging while also optimizing XRF interrogation of suspect items. FIG. 16 shows this schematically, wherein the handheld X-ray backscatter imaging device 1400 is used to inspect an item of interest 1410 (suspect item 1410, or target) behind a sheet of drywall 1405. A stationary’, or almost-stationary, X-ray beam 1401 starts a small sweep along direction 1430 and ends the sweep at 1402. Note that the start and end positions may coincide in the case of a completely stationary beam. Item of interest 1410 is now irradiated by the beam during the full angular sweep of the beam, and there is no longer any significant dwell time of the beam on either side of the item of interest. During20098.0040WQU1irradiation by the beam, X-ray fluorescence X-rays characteristic of the item are emitted in all directions, and some are detected with an energy-resolving detector 1450. Due to the very small fraction of time in which only the dry wall 1405 is irradiated, there is now a much larger XRF peak from the item of interest positioned on top of a much smaller Compton backscatter background signal from the drywall. This can greatly increase a Signal to Noise Ratio (SNR) of the resulting XRF signal.

[0103] Referring to FIG. 17, with further reference to FIGs. 1-16, an example energy’ spectrum is shown, corresponding to the stationary or almost stationary beam mode of FIG. 16. The small target object 1410 containing very' small quantities of tin is concealed behind a 1.5cm thick sheet of dry wall. In stationary' beam mode, the K-shell XRF X-rays 1510 detected from the tin are easily visible above the Compton scatter background 1500 from the dry wall.

[0104] Referring to FIG. 18, with further reference to FIGs. 1 -17, there is shown a cross-sectional diagram of the disk chopper wheel 312 of FIG. 3, with operation modified for switching from a scanning beam mode to a stationary beam mode according to present embodiments. A beam of source X-rays is output from an X-ray source (not shown in FIG. 18) and travels from the focal spot emission point in the X-ray source and passes through the attenuating material 316 of the disk chopper wheel 312 when a radial slit 314 moves into strip 306 on the chopper disk that is irradiated by the fan beam. Rotation 120 of the disk chopper wheel causes the output scanning beam of source X-rays to scan across the object under inspection (target).

[0105] With the use of a stepper motor or a motor with an encoder causing rotation of the disk chopper wheel 312, rotation of the disk can be rapidly slowed when switching from scanning mode to stationary mode, such as by using active braking, and one of the radial slits formed by the disk can be brought to a stop at the center of the fan beam of source X-rays (or ‘’irradiation strip”) 306. The source X-rays can then only pass through the intersection region (or “irradiation point”) 320 of the irradiation strip and the centered radial slit. This intersection region forms a square aperture through which the beam is projected onto the object from the focal spot.

[0106] Referring to FIG. 19, with further reference to FIGs. 1-18, the stationary mode capability described above is applied to the assembly 500. The scanning beam of source X-rays 1401 thus formed can then be advantageously directed onto a target item of interest to allow for enhanced XRF interrogation of the object. A resulting SNR can bemuch higher than that acquired with a scanning beam scanning over the full scanning angular range.

[0107] Various implementations according to embodiments allow the interrogating beam 1401 to ‘'dither” over a small angular range 1435, rather than being completely stationary. This can be useful when a very small item of interest is being interrogated and the exact location of the object is uncertain, making aiming of the beam onto the object more difficult. The beam dither allows the beam to “paint” the item of interest, even when the beam is not directly pointed at the item. A stepper motor controlling the disk is especially advantageous for this purpose, as the motor can easily be controlled to rotate the disk back and forth through a carefully controlled angular range. For example, while the full beam scan angle used while imaging might be in the range of 60 degrees to 90 degrees, the angular range 1435 in the “dither” mode could be in the range of 2 degrees to 5 degrees, 5 degrees to 10 degrees, or 10 degrees to 20 degrees.

[0108] Referring to FIG. 20, with further reference to FIGs. 1-19, an apparatus used as part of switching from a scanning beam to a stationary beam for an X-ray scanning system according to implementations of embodiments including a hoop chopper wheel is shown. A beam of X-rays travels from the focal spot emission point in the X-ray source 802 and passes through the attenuating material of hoop 812 when an aperture in hoop 838 moves into the region of the inside surface of the hoop that is irradiated by fan beam 806. Rotation of hoop 812 causes the beam to scan across the object under inspection.

[0109] With the use of a stepper motor or a motor with an encoder, rotation of the hoop can be rapidly slowed when switching from scanning mode to stationary mode using active braking and one of the apertures formed by the hoop can be brought to a stop at the center of the region on the inside surface of the hoop that is irradiated by the fan beam 806. The X-rays then pass through the irradiated aperture and are projected onto the object from the focal spot. The beam 1401 thus formed can then be advantageously directed onto an item of interest to allow for enhanced XRF interrogation of the object, with a resulting SNR that is much higher than that acquired with a scanning beam.

[0110] Referring to FIG. 21, with further reference to FIGs. 1-20, an X-ray scanning module with a hoop chopper wheel for an X-ray imaging system is show. The hoop chopper w heel show n in FIG. 21, incorporating features of embodiments of the present disclosure, allows the interrogating beam 1401 to “dither” over a small scanning angular range 1435, which can be selectable, rather than being completely stationary. A controllerdescribed hereinafter controls a motor that is configured to drive rotation of the chopper wheel. The rotation of the chopper wheel is controlled to be over a selectable chopper wheel angular range that will achieve a desired selectable scanning angular range for the scanning beam of X-rays 1401 to scan over a target. This can be useful when a very small item of interest is being interrogated and the exact location of the object is uncertain, making aiming of the beam onto the object more difficult. The beam dither allows the beam to "‘paint” the item of interest, even when the beam is not directly pointed at the item. A stepper motor controlling the hoop is especially advantageous for this purpose, as the motor can easily be controlled to rotate the hoop back and forth through a carefully controlled angular range. For example, while the full scanning angular range for the scanning beam of X-rays, used while scanning for imaging purposes, might be in the range of 60 degrees to 90 degrees. However, the angular range 1435 in the “dither” mode may be less than the full scanning angular range, such as in a range of 2 degrees to 5 degrees, 5 degrees to 10 degrees, or 10 degrees to 20 degrees, for example. Thus, the selectable scanning angular range may include values less than the full scanning angular range

[0111] Referring to FIG. 22 (prior art), with further reference to FIGs. 1-21, a perspective view is provided for an existing handheld backscatter X-ray imaging system is show n, including a detector arm that incorporates a transmission X-ray detector. In view of FIG. 22, as well as FIG. 1 and other disclosure herein, it will be apparent to those of ordinary skill in the art that transmission X-ray imaging according to known systems may be incorporated into systems, apparatuses, and methods according to implementations of the present embodiments that include switching between scanning, stationary, and or “dithering” modes. Thus, various implementations of embodiments may obtain transmission X-ray images in addition to backscatter X-ray images.

[0112] An additional preferred embodiment of the previously described embodiments allows the operator to select a preferred aperture defined by the chopper disk or chopper hoop to be irradiated in the stationary or dither mode by the incident fan beam. The preferred aperture may contain a beam filter, such as l / 4mm copper that removes the lower energy X-rays emitted by the source and therefore enhances the SNR of particular XRF peaks that otherwise would be superimposed on a higher Compton scatter background.

[0113] Referring to FIG. 23, with further reference to FIGs. 1-22, a graph is provided. An upper curve shows the same energy spectrum as in FIG. 17 for a small item containing trace amounts of tin, concealed behind a sheet of dry wall, irradiated with a 160kV X-ray beam, in which there is no beam filtration. A lower curve shows an energy spectrum acquired for the same item, but with the irradiated aperture containing a l / 4mm thick copper filter. It is apparent from FIG. 23 that the Compton background under the tin XRF peaks has been reduced by approximately a factor of two. while the XRF peaks themselves contain approximately the same number of counts. The resulting SNR for the detection of the tin material is therefore increased by a factor of approximately 40%, providing for a significantly enhanced detection sensitivity7.

[0114] Referring to FIG. 24, with further reference to FIGs. 1-23, a further graph shows, in an upper curve, the same energy' spectrum as in FIG. 17 for a small item containing trace amounts of tin, concealed behind a sheet of drywall, irradiated with a 160kV X-ray beam, in which there is no beam filtration. A lower curve in the graph is the energy spectrum acquired for the same item, but with the irradiated aperture containing a thicker l / 2mm thick copper filter.

[0115] Referring to FIG. 25, with further reference to FIGs. 1-24, an X-ray scanning system 2500 according to the first specific embodiment of the present disclosure is show n schematically. The system 2500 includes:a) an X-ray source 2502 configured to output a beam of source X-rays 2504; b) a chopper wheel 2512 rotatably mounted and arranged relative to the X- ray source 2502 so as to receive the beam of source X-rays 2504, the chopper wheel comprising an X-ray attenuating material configured to block X-rays of the beam of source X-rays 2504, the chopper wheel defining a set of beam apertures 2514 of which each aperture is configured to pass there through a portion of the beam of source X-rays 2504 to form a scanning beam of source X-rays 2510;c) a motor 2530 mechanically coupled to the chopper wheel 2510; and d) a controller 2532 configured to control the motor 2530 to effect rotation of the chopper wheel over a selectable chopper wheel angular range 2532 so as to cause the scanning beam of source X-rays 2510 to sweep over a selectable scanning angular range 2534 for scanning a target 2508.

[0116] It should be understood that by “selectable,” it is meant that the chopper wheel angular range, and correspondingly, the scanning angular range, are selectable via the controller, rather than requiring necessarily a change in hardware configuration. Thus, by appropriate command to the controller (e.g., from a CPU or from an operator through a CPU), the scanning angular range may be selectable on a scan-by-scan basis depending on the application, whether XRF analysis is desired (versus only X-ray scanning for imaging purposes), a size of the target of interest, a proximity’ of an operator to the target, and similar considerations.

[0117] In FIG. 25, a coupling 2532 couples the motor 2530 to the chopper wheel 2512. The coupling may take any form known in the art for coupling a motor to a chopper wheel, including means for attaching a structure connected to the chopper wheel to a shaft of the motor 2530. such as shown in FIGs. 2A and 12. The angular ranges, rotations of the chopper w heel, sweeping of the scanning beam, encoder, and other components are shown only schematically in FIG. 25 and are not intended to indicate specific ranges, positions, or orientations. Certain options for these features may be understood in relation to the preceding figures and disclosure and consistent with knowledge of persons skilled in the art in view’ of this disclosure.

[0118] Additionally, the controller 2532 may be further configured to control the motor 2530 to effect a continuous rotation of the chopper w heel in a given angular direction, such as the direction 1430 of FIG. 14 to cause the beam of source X-rays 2510 to sweep over a full scanning angular range, such as the full range from 1401 to 1402 as described in connect on with FIG. 14.

[0119] Additionally, the selectable scanning angular range may include values less than the full scanning angular range 1430, such from 1401 to 1402 as described in connection with FIG. 16, and such as the small scanning angular range 1435 of FIG. 19.

[0120] Additionally or alternatively, the controller 2532 may be further configured to control the motor 2530 so as to cause the chopper wheel to remain stationary, such that the selectable scanning angular range includes a zero value whereby the pencil beam of source X-rays remains stationary with respect to the X-ray source, as described in connection with FIG. 16, for example.

[0121] Additionally or alternatively, the controller 2532 may be further configured to control the motor to effect rotation of the chopper w heel in alternating angular directions, such as the alternating directions shown via the small angular range 1435 of FIG. 19, for20098.0040WQU1example, so as to cause the scanning beam of source X-rays 2510 to sweep in a dithering manner, in opposing angular directions.

[0122] Referring to FIG. 26, with further reference to FIGs. 1-25, an X-ray scanning system 2600 is illustrated schematically, which includes the features of FIG. 25 and additional optional features according to implementations of the first specific embodiment.

[0123] For example, additionally or alternatively, the system 2500 may further include an energy-resolving detector 2650 as illustrated in FIG. 26, configured to detect X-ray fluorescence received from the target. An example is the detector 1450 of FIGs. 14 and 16. Examples of X-ray fluorescence so detected are provided in FIGs. 15 and 17 and elsewhere in the application.

[0124] Additionally or alternatively, the system 2500 may further include a material identification module 2660, as shown in FIG. 2660, configured to output an indication of a material 2656 of the target 2508 based on the X-ray fluorescence received from the target 2508 by the energy-resolving detector 2650. In one implementation, the module 2660 may include a computer processor, for example, that may calculate an energy’ spectrum of XRF, similar to those of FIGs. 15 and 17, and identify XRF peaks and thereby determine a material such as tin or lead in the target.

[0125] Additionally or alternatively, the motor 2530 can be a stepper motor or a servo motor. These motors collectively may be referred to as “position-controllable” and can be particularly useful in implementations since position of these motors are typically tracked and known either via encoders or via a number of rotation steps of a stepper motor, for example.

[0126] Additionally or alternatively, as indicated in FIG. 26, the system 2500 may further include a position encoder operatively connected to the controller 2532 and configured to provide position information to the controller for control of the motor 2530. Additionally, the position encoder may be selected from the group consisting of: a built-in position encoder 2654 built into the motor 2530, and an external position encoder configured to track rotational position of the chopper wheel, such as the chopper wheel encoder 2652. The chopper wheel encoder may include notches in the chopper wheel and an LED sensor known in the art, as one example, or a Hall effect sensor as known in the art, as another example.

[0127] Additionally or alternatively, the system 2500 further includes a holdable housing, such as the housing 630 of FIG. 6. The X-ray source 2502 and the chopper wheel 2512 may be mounted in the holdable housing, as shown and described in the application.

[0128] Additionally or alternatively, the chopper wheel may a disk chopper wheel, such as one of 112, 212a, 312, and 501, for example. Optionally, the set of apertures may include slit apertures, such 214, for example.

[0129] Additionally or alternatively, the chopper wheel is a hoop chopper wheel, such s 212c, 712, 812, or another hoop chopper wheel described in the examples throughout the application. Optionally the set of apertures may include a selection of apertures selected from the group consisting of slit apertures, circular apertures such as 838, ellipsoidal apertures, rectangular apertures, and combinations thereof.

[0130] Additionally or alternatively, the system 2500 further includes:a) a set of scatter X-ray detectors such as backscatter detector 2638 of FIG.26, which is arranged for detection of scattered X-rays that are scattered from the target 2508 resulting from the scanning beam of source X-rays 2510 scanning the target 2508; andb) an image module 2662 configured to produce an X-ray image 2658 of the target 2508 based on scattered X-rays detected by the backscatter detector 2638. and / or based on a transmission detector such as is incorporated into the detector arm of FIG. 22.

[0131] Additionally or alternatively, the system 2500 further includes an X-ray filter, such as filter 2664 of FIG. 26, situated wi th respect to at least one beam aperture of the set of beam apertures 2514 so as to filter the portion of the beam of source X-rays that the at least one beam aperture is configured to pass. Additionally, the controller 2532 may be further configured to control the motor 2530 so as to select a given beam aperture of the set of beam apertures 2514 to form the scanning beam of source X-rays 2510. Further in addition, the given beam aperture may be selectable based on the X-ray filter 2664 that is situated to filter the portion of the beam.

[0132] The X-ray scanning system 2500 may further be considered to be an X-ray imaging system or apparatus with the inclusion of known components used to produce an X-ray image of the target. In the example implementation of FIG. 26, the backscatter X-ray detector 2638 provides signals to an image module 2662, which generates and outputsan X-ray image 2658, such as 655 of FIG. 6 or such as in FIG. 10, for example. Such components may include a backscater X-ray detector such as in examples of the application, a transmission X-ray detector such as in the detector arm of FIG. 22 or such as the 122 of FIG. 1, an image module such as 2662, such as including an onboard computer processor that is configured to produce the X-ray image of the target based on detected X-rays detected by the set of scater detectors, and optionally an image display screen such as shown in FIG. 6, for example.

[0133] According to a second specific embodiment, an X-ray imaging apparatus includes:a) a holdable housing;b) an X-ray source mounted within the housing and configured to output a fan beam of X-rays; andc) a chopper wheel rotatably mounted within the housing and comprising an X-ray atenuating material configured to block X-rays of the fan beam, the chopper wheel defining a set of beam apertures of which each aperture is configured to pass there through a corresponding angular portion of X-rays from the fan beam, wherein the chopper wheel can be operated in two or more of three operational modes selected from the group consisting of: i. a first operational mode comprising rotation of the chopper wheel in a continuous direction causing scanning of the corresponding angular portion of X-rays;ii. a second operational mode comprising selectively irradiating a beam aperture with X-rays from the fan beam wherein the chopper wheel is stationary with respect to the fan beam, causing the corresponding angular portion of X-rays from the fan beam to be stationary with respect to the X-ray source; and iii. a third operational mode comprising selectively irradiating a beam aperture with X-rays from the fan beam wherein the chopper wheel is rotated through a small angular range, causing the corresponding angular portion of X-rays from the fan beam to scan through a small angular range.

[0134] Implementations of the second specific embodiment will be readily understood by those skilled in the art in view of the present disclosure including FIGs. 1-26. and more specifically FIGs. 14-26.

[0135] For example, additionally, the chopper wheel may be a disk chopper wheel defining radial slit beam apertures. As an alternative, the chopper wheel may be a hoop chopper wheel defining beam apertures in form of slits, circular holes, rectangular holes, or other apertures of other shapes.

[0136] Additionally or alternatively, the third operational mode may cause the chopper wheel to rotate back and forth through a small angular range, causing the corresponding angular portion of X-rays from the fan beam to scan back and forth through a small angular range (smaller than a full angular range of the portion of X-rays of the source beam forming the scanning X-ray beam such as a pencil beam, for example).

[0137] Additionally or alternatively, one or more beam apertures defined by the chopper wheel contain one or more different beam filters, such as illustrated in FIG. 26.

[0138] Additionally or alternatively, in the second and third operational modes, the irradiated aperture may be selected based on the beam filtration provided by the irradiated aperture.

[0139] Additionally or alternatively, the X-ray imaging apparatus may further include any set of elements described in connection with the first specific embodiment.

[0140] Additionally or alternatively, the X-ray imaging apparatus may further comprise use of any set of elements described in connection with implementations of the first specific embodiment.

[0141] Additionally or alternatively, the X-ray imaging apparatus may further comprise operating according to any set of elements of implementations of the first specific embodiment.

[0142] In a third specific embodiment, a penetrating radiation scanning system includes:a) a penetrating radiation source configured to output a beam of source penetrating radiation;b) a chopper wheel rotatably mounted and arranged relative to the penetrating radiation source so as to receive the beam of source penetrating radiation, the chopper wheel comprising a penetrating radiation attenuating materialconfigured to block penetrating radiation of the beam of source penetrating radiation, the chopper wheel defining a set of beam apertures of which each aperture is configured to pass there through a portion of the beam of source penetrating radiation to form a scanning beam of source penetrating radiation;c) a motor mechanically coupled to the chopper wheel; andd) a controller configured to control the motor to effect rotation of the chopper wheel over a selectable chopper wheel angular range so as to cause the scanning beam of source penetrating radiation to sweep over a selectable scanning angular range for scanning a target.

[0143] The penetrating radiation scanning system may include, use, and / or operate according any set of elements described in connection with implementations of the first specific embodiment and / or of the second specific embodiment. In one implementation, the penetrating radiation comprises X-rays. In other implementations, the penetrating radiation takes a form of another type of penetrating radiation such as gamma rays, beta rays, protons, alpha particles, or neutrons, for example. The source, detectors, chopper wheel, and all other components are then modified according to appropriate known components and methods suitable for those types of penetrating radiation.

[0144] FIG. 26 illustrates various optional features of an X-ray scanning system, an X-ray imaging apparatus, a penetrating radiation scanning system, and a method of X-ray scanning according to first, second, third, and fourth specific embodiments of the disclosure.

[0145] FIG. 27 is a flow diagram illustrating a procedure 2700 for X-ray scanning corresponding to a method of X-ray scanning according to the fourth specific embodiment of the present disclosure. The procedure 2700 includes:a) at 2710, outputting a beam of source X-rays;b) at 2720, blocking X-rays of the beam of source X-rays at a chopper wheel; c) at 2730, passing a portion of the beam of source X-rays through a set of beam apertures defined by the chopper wheel to form a scanning beam of source X-rays; andd) at 2740, controlling a motor mechanically coupled to the chopper wheel to effect rotation of the chopper w heel over a selectable chopper w heelangular range so as to cause the scanning beam of source X-rays to sweep over a selectable scanning angular range for scanning a target.

[0146] In various implementations, the procedure 2700 may further include, use. and / or operate according to any set of elements shown and described herein in connection with the first, second, and third specific embodiments. These implementations will be understood by those of skill in the art in view of the present disclosure.

[0147] Additional Advantageous Features

[0148] While X-ray scanners and imagers with their backscatter and transmission X-ray images according to embodiments will be very helpful in locating concealed contraband in vehicles and other enclosures, it is advantageous to expand the capability of these scanners and imagers to include other imaging modalities, such as infrared imaging, and to add non-imaging capabilities such as passive radiation detection and the detection of precious metals through X-ray fluorescence (XRF). An infrared camera can be mounted at the front of the X-ray backscatter imaging apparatus that acquires thermal imaging data that reflects the surface temperature of each area of the target object that is also being scanned with X-rays. This allows additional information to be obtained about the target object being inspected.

[0149] There is also a need to make it easier for the operator to visualize exactly where on the target object the X-ray beam providing the imaging is being positioned. Prior art imaging devices typically use lasers to project a circular spot or a short line pattern onto the target object to indicate to the operator the limits of the X-ray beam sweep trajectory7. The limitation of this approach is that the laser illumination spots can often be hard to see in bright daylight, or the laser beams producing the illumination spots are not intersecting with the target object. In either case, the lasers are of little value to the operator to aid in the inspection process.

[0150] It is advantageous therefore to improve the laser alignment process by introducing a line laser, rather than a point laser, which directly projects a full line onto the target object, corresponding to the full length of the sweep trajectory of the X-ray¬ beam across the target object. In this case, a large portion of the laser line will be visible on the target obj ect even when the start and end points of the scan are not aligned with the target object, and the prior-art laser spots or line segments indicating the beginning and end of the scan trajectory are not visible to the operator.

[0151] The ability to conveniently use handheld backscatter X-ray imaging devices can be hampered when the devices are not designed for operators with gloved hands, such as in cold or dirty environments. There is a need, therefore, to complement the touch screens typically used to control the devices with navigation buttons and / or pads, which allow the operator the choice of keeping their gloves on and not using the touch screen. It is advantageous therefore for the handles for holding the imaging apparatus to include at least one navigational pad configured to navigate options or features on a display screen of the apparatus.

[0152] Many of the handheld X-ray backscatter imagers that have been used in the field since they were introduced in 2018 have been used by Customs agents or by law enforcement officers for drug interdiction applications. In these circumstances, it is often required for legal reasons for the X-ray images to be protected and to have a chain of custody that is not dependent on the operator. It is therefore advantageous for these images to be automatically uploaded to a secure server when the device is powered down after a shift has ended, ensuring that the images are not accidentally erased or misplaced, and that the integrity of the images cannot be easily compromised.

[0153] The depth dimension of a handheld backscatter X-ray imager is often a limiting factor when carrying out inspections in confined spaces. Under such conditions, it is often advantageous to have an imaging device with a depth dimension smaller than that shown in FIG. 8A, which is typical for imaging devices containing a disk chopper wheel. In these devices, the depth dimension is typically approximately 9 to 10 inches. On a newer instrument that has been disclosed, a hoop chopper wheel is used with an angled extraction of the X-rays from the anode of the X-ray tube as shown in FIG. 6. With this arrangement, the depth dimension of the device can be reduced to approximately 6 inches, as shown in FIG. 8B. This allows the device to be used in confined spaces, such as to image the undercarriage of vehicles lower to the ground.

[0154] Certain Applications

[0155] Various embodiments can be used advantageously to detect electronic devices concealed behind barriers, such as dry wall, for example. Printed circuit boards (PCBs) may use lead-based solder, which emits highly penetrating XRF at an X-ray energy of 75keV, for example. However, new er PCBs may use lead-free solder that is mostly tin-based. These emit lower-energy' XRF at X-ray energies of only 25keV and 28keV, which are more challenging to detect. By using various embodiments to increase the dwell timeof the X-ray beam on the target object, the ability to detect the XRF signal is greatly enhanced.

[0156] Embodiments can also be used to detect the presence of precious metals, which may constitute contraband and be concealed behind barriers. Example precious metals include gold, platinum, silver, bullion made of these or other metals in form of coins or bars, and other precious metals in various forms. In all these cases, a probability of detection can be significantly enhanced by increasing the dwell time of the beam on the suspect areas.

[0157] In addition, embodiments can be used in non-destructive testing (NDT) applications, such as identifying a material composition of pipes that are concealed by walls. For example, it is often advantageous to be able to output an alert indicating a presence of lead pipes or lead-lined iron pipes in walls, since often there is a desire to remove and replace these pipes for health reasons.

[0158] Implementation Clauses

[0159] Implementation examples are provided in the following numbered clauses. The numbered clauses represent some embodiments of the present invention and potential claims. (The actual claims are provided at the end of this application.) These clauses form a part of the written description of this application. Accordingly, subject matter of the following clauses may be presented as claims in later proceedings involving this application or any application claiming priority based on this application. Inclusion of such clauses should not be construed to mean that the claims do not cover the subject matter of the clauses. Thus, a decision not to present these clauses as claims in later proceedings should not be construed as a donation of the subject matter to the public.

[0160] Without limitation, potential subject matter that may be claimed includes:

[0161] Clause 1. An X-ray scanning system comprising:a) an X-ray source configured to output a beam of source X-rays;b) a chopper wheel rotatably mounted and arranged relative to the X-ray source so as to receive the beam of source X-rays, the chopper wheel comprising an X-ray attenuating material configured to block X-rays of the beam of source X-rays, the chopper wheel defining a set of beam apertures of which each aperture is configured to pass there through a portion of the beam of source X-rays to form a scanning beam of source X-rays;c) a motor mechanically coupled to the chopper wheel; andd) a controller configured to control the motor to effect rotation of the chopper wheel over a selectable chopper wheel angular range so as to cause the scanning beam of source X-rays to sweep over a selectable scanning angular range for scanning a target.

[0162] Clause 2. The X-ray scanning system of claim 1, wherein the controller is further configured to control the motor to effect a continuous rotation of the chopper wheel in a given angular direction to cause the pencil beam of source X-rays to sweep over a full scanning angular range.

[0163] Clause 3. The X-ray scanning system of clause 2, wherein the selectable scanning angular range includes values less than the full scanning angular range.

[0164] Clause 4. The X-ray scanning system of any of clauses 1-3. wherein the controller is further configured to control the motor so as to cause the chopper wheel to remain stationary, such that the selectable scanning angular range includes a zero value whereby the pencil beam of source X-rays remains stationary with respect to the X-ray source.

[0165] Clause 5. The X-ray scanning system of any of clauses 1-4, wherein the controller is further configured to control the motor to effect rotation of the chopper wheel in alternating angular directions so as to cause the pencil beam of source X-rays to sweep in a dithering manner.

[0166] Clause 6. The X-ray scanning system of any of clauses 1-5, further compnsing an energy-resolving detector configured to detect X-ray fluorescence received from the target.

[0167] Clause 7. The X-ray scanning system of clause 6, further comprising a material identification module configured to output an indication of a material of the target based on the X-ray fluorescence received from the target.

[0168] Clause 8. The X-ray scanning system of any of clauses 1-7, wherein the motor is a stepper motor.

[0169] Clause 9. The X-ray scanning system of any of clauses 1-7, wherein the motor is a servo motor.

[0170] Clause 10. The X-ray scanning system of any of clauses 1-9, further including a position encoder operatively connected to the controller and configured to provide position information to the controller for control of the motor.

[0171] Clause 11. The X-ray scanning system of clause 10, wherein the position encoder is selected from the group consisting of: a built-in position encoder built into the motor, and an external position encoder configured to track rotational position of the chopper wheel.

[0172] Clause 12. The X-ray scanning system of any of clauses 1-11, further comprising a holdable housing, and wherein the X-ray source and the chopper wheel are mounted in the holdable housing.

[0173] Clause 13. The X-ray scanning system of any of clauses 1-12, wherein the chopper wheel is a disk chopper wheel, and optionally wherein the set of apertures includes slit apertures.

[0174] Clause 14. The X-ray scanning system of any of clauses 1-12, wherein the chopper wheel is a hoop chopper wheel, and optionally wherein the set of apertures includes a selection of apertures is selected from the group consisting of slit apertures, circular apertures, ellipsoidal apertures, rectangular apertures, and combinations thereof.

[0175] Clause 15. The X-ray scanning system of any of clauses 1-14, further comprising:a) a set of scatter X-ray detectors arranged for detection of scattered X-rays that are scattered from the target resulting from the scanning beam of source X-rays scanning the target; andb) an image module configured to produce an X-ray image of the target based on scattered X-rays detected by the set of scatter X-ray detectors.

[0176] Clause 16. The X-ray scanning system of any of clauses 1-15, further including an X-ray filter situated with respect to at least one beam aperture of the set of beam apertures so as to filter the portion of the beam of source X-rays that the at least one beam aperture is configured to pass.

[0177] Clause 17. The X-ray scanning system of clause 16, wherein the controller is further configured to control the motor so as to select a given beam aperture of the set of beam apertures to form the scanning beam of source X-rays.

[0178] Clause 18. The X-ray scanning system of clause 17. wherein the given beam aperture is selectable based on the X-ray filter that is situated to filter the portion of the beam.

[0179] Clause 19. An X-ray imaging apparatus comprising:a) a holdable housing;b) an X-ray source mounted within the housing and configured to output a fan beam of X-rays; andc) a chopper wheel rotatably mounted within the housing and comprising an X-ray attenuating material configured to block X-rays of the fan beam, the hoop chopper wheel defining a set of beam apertures of which each aperture is configured to pass there through a corresponding angular portion of X-rays from the fan beam, wherein the chopper wheel can be operated in two or more of three operational modes selected from the group consisting of:i. rotation of the hoop chopper wheel causing scanning of the corresponding angular portion of X-rays;ii. selectively irradiating a beam aperture with X-rays from the fan beam wherein the chopper wheel is stationary, causing the corresponding angular portion of X-rays from the fan beam to be stationary; andiii. selectively irradiating a beam aperture with X-rays from the fan beam wherein the chopper wheel is rotated through a small angular range, causing the corresponding angular portion of X-rays from the fan beam to scan through a small angular range.

[0180] Clause 20. The imaging apparatus of clause 19, wherein the chopper wheel is a disk chopper wheel defining radial slit beam apertures.

[0181] Clause 21. The imaging apparatus of clause 20, wherein the chopper wheel is a hoop chopper wheel defining beam apertures.

[0182] Clause 22. The imaging apparatus of any of clauses 19-21, wherein the third operational mode causes the chopper wheel to rotate back and forth through a small angular range, causing the corresponding angular portion of X-rays from the fan beam to scan back and forth through a small angular range.

[0183] Clause 23. The imaging apparatus of any of clauses 19-22, wherein one or more beam apertures defined by the chopper wheel contain one or more different beam filters.

[0184] Clause 24. The imaging apparatus of any of clauses 19-23, wherein in the second and third operational modes, the irradiated aperture is selected based on the beam filtration provided by the irradiated aperture.

[0185] Clause 25. The imaging apparatus of any of clauses 19-24, further comprising any set of elements of any of clauses 1-18.

[0186] Clause 26. The imaging apparatus of any of clauses 19-25, further comprising using any set of elements of any of clauses 1-18.

[0187] Clause 27. The imaging apparatus of any of clauses 19-25, further comprising operating according to any set of elements of any of clauses 1-18.

[0188] Clause 28. A penetrating radiation scanning system comprising:a) a penetrating radiation source configured to output a beam of source penetrating radiation;b) a chopper wheel rotatably mounted and arranged relative to the penetrating radiation source so as to receive the beam of source penetrating radiation, the chopper wheel comprising a penetrating radiation attenuating material configured to block penetrating radiation of the beam of source penetrating radiation, the chopper wheel defining a set of beam apertures of which each aperture is configured to pass there through a portion of the beam of source penetrating radiation to form a scanning beam of source penetrating radiation;c) a motor mechanically coupled to the chopper wheel; andd) a controller configured to control the motor to effect rotation of the chopper wheel over a selectable chopper wheel angular range so as to cause the scanning beam of source penetrating radiation to sweep over a selectable scanning angular range for scanning a target.

[0189] Clause 29. The penetrating radiation scanning system of clause 28, further comprising any set of elements of any of clauses 1-27.

[0190] Clause 30. The penetrating radiation scanning system of any of clauses 28-29, further comprising using any set of elements of any of clauses 1-27.

[0191] Clause 31. The penetrating radiation scanning system of any of clauses 28-30, further comprising operating according to any set of elements of any of clauses 1-27.

[0192] Clause 32. A method of X-ray scanning, the method comprising:a) outputting abeam of source X-rays;b) blocking X-rays of the beam of source X-rays at a chopper wheel;c) passing a portion of the beam of source X-rays through a set of beam apertures defined by the chopper wheel to form a scanning beam of source X-rays; andd) controlling a motor mechanically coupled to the chopper wheel to effect rotation of the chopper wheel over a selectable chopper wheel angular range so as to cause the scanning beam of source X-rays to sweep over a selectable scanning angular range for scanning a target.

[0193] Clause 33. The method of claim 32, further comprising any set of elements of any of claims 1-31.

[0194] Clause 34. The method of any of claims 32-33, further comprising using any set of elements of any of claims 1-31.

[0195] Clause 35. The method of any of claims 32-34, further comprising operating according to any set of elements of any of claims 1-31.

[0196] Final Considerations

[0197] The embodiments of the invention described above are intended to be merely exemplary. In view of the present description and drawings, numerous variations, modifications, and combinations of parameters are possible. All such variations and modifications are intended to be within the scope of the present invention as defined in any appended claims. Those variations, modifications, and combinations of parameters described herein are examples for purposes of explanation only.

Claims

CLAIMSWhat is claimed is:

1. An X-ray scanning system comprising:an X-ray source configured to output a beam of source X-rays;a chopper wheel rotatably mounted and arranged relative to the X-ray source so as to receive the beam of source X-rays, the chopper wheel comprising an X-ray attenuating material configured to block X-rays of the beam of source X- rays, the chopper wheel defining a set of beam apertures of which each aperture is configured to pass there through a portion of the beam of source X-rays to form a scanning beam of source X-rays;a motor mechanically coupled to the chopper wheel; anda controller configured to control the motor to effect rotation of the chopper wheel over a selectable chopper wheel angular range so as to cause the scanning beam of source X-rays to sweep over a selectable scanning angular range for scanning a target.

2. The X-ray scanning system of claim 1, wherein the controller is further configured to control the motor to effect a continuous rotation of the chopper wheel in a given angular direction to cause the pencil beam of source X-rays to sweep over a full scanning angular range.

3. The X-ray scanning system of claim 2, wherein the selectable scanning angular range includes values less than the full scanning angular range.

4. The X-ray scanning system of any of claims 1 -3, wherein the controller is further configured to control the motor so as to cause the chopper wheel to remain stationary', such that the selectable scanning angular range includes a zero value whereby the pencil beam of source X-rays remains stationary with respect to the X-ray source.

5. The X-ray scanning system of any of claims 1-4, wherein the controller is further configured to control the motor to effect rotation of the chopper wheel inalternating angular directions so as to cause the pencil beam of source X-rays to sweep in a dithering manner.

6. The X-ray scanning system of any of claims 1-5, further comprising an energyresolving detector configured to detect X-ray fluorescence received from the target.

7. The X-ray scanning system of claim 6, further comprising a material identification module configured to output an indication of a material of the target based on the X-ray fluorescence received from the target.

8. The X-ray scanning system of any of claims 1-7, wherein the motor is a stepper motor.

9. The X-ray scanning system of any of claims 1-7, wherein the motor is a servo motor.

10. The X-ray scanning system of any of claims 1-9, further including a position encoder operatively connected to the controller and configured to provide position information to the controller for control of the motor.

11. The X-ray scanning system of claim 10, wherein the position encoder is selected from the group consisting of: a built-in position encoder built into the motor, and an external position encoder configured to track rotational position of the chopper wheel.

12. The X-ray scanning system of any of claims 1-11, further comprising a holdable housing, and wherein the X-ray source and the chopper wheel are mounted in the holdable housing.

13. The X-ray scanning system of any of claims 1-12, wherein the chopper wheel is a disk chopper wheel, and optionally wherein the set of apertures includes slit apertures.

14. The X-ray scanning system of any of claims 1-12, wherein the chopper wheel is a hoop chopper wheel, and optionally wherein the set of apertures includes aselection of apertures is selected from the group consisting of slit apertures, circular apertures, ellipsoidal apertures, rectangular apertures, and combinations thereof.

15. The X-ray scanning system of any of claims 1-14, further comprising:a set of scatter X-ray detectors arranged for detection of scattered X-rays that are scattered from the target resulting from the scanning beam of source X- rays scanning the target; andan image module configured to produce an X-ray image of the target based on scattered X-rays detected by the set of scatter X-ray detectors.

16. The X-ray scanning system of any of claims 1-15, further including an X-ray filter situated with respect to at least one beam aperture of the set of beam apertures so as to filter the portion of the beam of source X-rays that the at least one beam aperture is configured to pass.

17. The X-ray scanning system of claim 16, wherein the controller is further configured to control the motor so as to select a given beam aperture of the set of beam apertures to form the scanning beam of source X-rays.

18. The X-ray scanning system of claim 17, wherein the given beam aperture is selectable based on the X-ray filter that is situated to filter the portion of the beam.

19. An X-ray imaging apparatus comprising:a holdable housing;an X-ray source mounted within the housing and configured to output a fan beam of X-rays; anda chopper wheel rotatably mounted within the housing and comprising an X-ray attenuating material configured to block X-rays of the fan beam, the hoop chopper wheel defining a set of beam apertures of which each aperture is configured to pass there through a corresponding angular portion of X-rays from the fan beam, wherein the chopper wheel can be operated in two or more of three operational modes selected from the group consisting of:rotation of the hoop chopper wheel causing scanning of the corresponding angular portion of X-rays;selectively irradiating a beam aperture with X-rays from the fan beam wherein the chopper wheel is stationary, causing the corresponding angular portion of X-rays from the fan beam to be stationary; and selectively irradiating a beam aperture with X-rays from the fan beam wherein the chopper wheel is rotated through a small angular range, causing the corresponding angular portion of X-rays from the fan beam to scan through a small angular range.

20. The imaging apparatus of claim 19, wherein the chopper wheel is a disk chopper wheel defining radial slit beam apertures.

21. The imaging apparatus of claim 20, wherein the chopper wheel is a hoop chopper wheel defining beam apertures.

22. The imaging apparatus of any of claims 19-21, wherein the third operational mode causes the chopper wheel to rotate back and forth through a small angular range, causing the corresponding angular portion of X-rays from the fan beam to scan back and forth through a small angular range.

23. The imaging apparatus of any of claims 19-22, wherein one or more beam apertures defined by the chopper wheel contain one or more different beam filters.

24. The imaging apparatus of any of claims 19-23, wherein in the second and third operational modes, the irradiated aperture is selected based on the beam filtration provided by the irradiated aperture.

25. The imaging apparatus of any of claims 19-24, further comprising any set of elements of any of claims 1-18.

26. The imaging apparatus of any of claims 19-25, further comprising using any set of elements of any of claims 1-18.

27. The imaging apparatus of any of claims 19-25, further comprising operating according to any set of elements of any of claims 1-18.

28. A penetrating radiation scanning system comprising:a penetrating radiation source configured to output a beam of source penetrating radiation;a chopper wheel rotatably mounted and arranged relative to the penetrating radiation source so as to receive the beam of source penetrating radiation, the chopper wheel comprising a penetrating radiation attenuating material configured to block penetrating radiation of the beam of source penetrating radiation, the chopper wheel defining a set of beam apertures of which each aperture is configured to pass there through a portion of the beam of source penetrating radiation to form a scanning beam of source penetrating radiation;a motor mechanically coupled to the chopper wheel; anda controller configured to control the motor to effect rotation of the chopper wheel over a selectable chopper wheel angular range so as to cause the scanning beam of source penetrating radiation to sweep over a selectable scanning angular range for scanning a target.

29. The penetrating radiation scanning system of claim 28, further comprising any set of elements of any of claims 1-27.

30. The penetrating radiation scanning system of any of claims 28-29, further comprising using any set of elements of any of claims 1-27.

31. The penetrating radiation scanning system of any of claims 28-30, further comprising operating according to any set of elements of any of claims 1-27.

32. A method of X-ray scanning, the method comprising:outputting a beam of source X-rays;blocking X-rays of the beam of source X-rays at a chopper wheel; passing a portion of the beam of source X-rays through a set of beam apertures defined by the chopper wheel to form a scanning beam of source X- rays; andcontrolling a motor mechanically coupled to the chopper wheel to effect rotation of the chopper wheel over a selectable chopper wheel angular range so as to cause the scanning beam of source X-rays to sweep over a selectable scanning angular range for scanning a target.

33. The method of claim 32, further comprising any set of elements of any of claims 1-31.

34. The method of any of claims 32-33, further comprising using any set of elements of any of claims 1-31.

35. The method of any of claims 32-34, further comprising operating according to any set of elements of any of claims 1-31.

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