An X-ray device includes: an X-ray source configured to emit X-rays; a scintillator, the scintillator being configured to emit light in response to absorption of the X-rays; a detector; a frame enclosing the X-ray source and the detector; standoffs positioned on the frame; shielding panels comprising lead; one or more brackets with fasteners configured to attach to the standoffs; and exterior panels with fasteners configured to attach to the one or more brackets. The standoffs form a datum structure for the one or more brackets. Each of the standoffs has a length and a cross-sectional size, and each of the shielding panels includes holes having a cross-sectional size greater than the cross-sectional size of the standoffs by an amount that ensures the standoffs will pass through the holes. The length of the standoffs is greater than a maximum thickness possible for the given shielding panel due to variations in thickness.

BACKGROUND

This specification relates to X-ray computed tomography (CT) devices.

X-ray computed tomography (CT) is a technique that can be used by manufacturers in order to determine the quality of the products which they produce. X-ray CT is particularly useful to give manufacturers the ability to inspect certain parts of their products in a non-invasive, non-destructive fashion. Given this, X-ray CT is becoming more popular in production manufacturing settings where quality control is of high importance.

X-ray CT devices require shielding to prevent harmful X-rays from leaking from the X-ray CT device.

SUMMARY

This specification describes technologies relating to an X-ray shielding device. In particular, this specification describes systems and apparatuses configured to allow shielding of X-rays to prevent the emission of harmful X-rays.

Compared to other metals and materials in general, lead is one of the most effective X-ray shielding materials, owing to its large attenuation coefficient and high density. Additionally, lead is relatively inexpensive compared to other X-ray shielding materials. Lead, however, is toxic to humans and other species, and poses other engineering problems. For example, due to its softness, obtaining a precisely aligned structure composed of lead can require iterative assembly processes, which can be slow and cumbersome. Additionally, since lead is heavy, panels of lead making up the exterior of an X-ray shielding device might require being split up into smaller panels for assembly. The panels being split up into neighboring, smaller panels create gaps in the X-ray shielding device, which increases the chance of X-ray radiation leaking from the X-ray shielding device.

The described X-ray shielding device overcomes the challenges of working with lead through use of a datum structure to provide accurate mounting features that pass through the lead, thereby avoiding the use of lead for providing structural support. Additionally, in some implementations, a C-channel (or similarly shaped) structure within the X-ray shielding device can seal gaps between neighboring lead panels and reinforce an interior frame structure of the X-ray shielding device.

In general, innovative aspects of the subject matter described in this specification can be embodied an X-ray device that includes: an X-ray source configured to emit X-rays; a scintillator arranged to absorb the X-rays after interaction with an object that has been placed in the X-ray device, the scintillator being configured to emit light in response to absorption of the X-rays; a detector arranged to receive the light from the scintillator; a frame enclosing the X-ray source and the detector; standoffs positioned on the frame; shielding panels comprising lead; one or more brackets with fasteners configured to attach to the standoffs; and exterior panels with fasteners configured to attach to the one or more brackets. The standoffs form a datum structure for the one or more brackets. Each of the standoffs can have a length and a cross-sectional size, and each of the shielding panels can include holes having a cross-sectional size that is greater than the cross-sectional size of the standoffs by an amount that ensures the standoffs will pass through the holes despite variations in a placement of the holes in a given shielding panel resulting from manufacturing of the given shielding panel. The length of the standoffs can be greater than a maximum thickness possible for the given shielding panel due to variations in thickness resulting from the manufacturing of the given shielding panel.

Another general aspect can be embodied in an X-ray device that includes: an X-ray source configured to emit X-rays; a scintillator arranged to absorb the X-rays after interaction with an object that has been placed in the X-ray device, the scintillator being configured to emit light in response to absorption of the X-rays; a detector arranged to receive the light from the scintillator; a frame enclosing the X-ray source and the detector; shielding panels including lead; a metal piece having fasteners configured to attach the metal piece with the frame; and the shielding piece being sized and positioned to prevent X-rays from passing (i) through the gap and (ii) through the holes in the first and second shielding panels on either side of the gap, which are usable when coupling the first and second shielding panels with the frame. Each of the shielding panels can include holes usable to couple the shielding panel with the frame, where a first and a second of the shielding panels protect a single side of the frame and have been reduced in size to facilitate installation of the first and second shielding panels. A gap can remain between the first shielding panel and the second shielding panel when installed on the single side of the frame, and the metal piece can be shaped to receive a shielding piece including lead.

These and other implementations can each optionally include one or more of the following features. In some implementations, the X-ray device includes at least one additional shielding panel without lead.

In some implementations, the X-ray device further includes at least one corner guard including an angled sheet of lead extending between two adjacent sides of the frame. The angled sheet of lead can be placed at an acute angle between the two adjacent sides of the shielding panels, and edges of the angled sheet of lead can be chamfered in accordance with the acute angle.

In some implementations, the X-ray device further includes a metal sheet on which the corner guard is attached. The metal sheet can be attached to the frame

In some implementations, the shielding panels comprise at least one laminate comprising lead and steel. In some implementations, each of the shielding panels is a laminate comprising lead and steel.

In some implementations, at least one of the one or more brackets is configured and arranged to have two of the exterior panels located on different sides of the X-ray device attached to a same bracket.

In some implementations, the X-ray device includes one or more additional shielding panels including a plastic impregnated with lead-free particles.

In some implementations, each of the standoffs includes a threaded hole, and each of the fasteners is configured to attach the brackets to the standoffs is a bolt configured to mate with the threaded hole.

In some implementations, each shielding panel of the shielding panels weighs less than 39 kilograms.

In some implementations, the cross-sectional size of the holes is greater than the cross-sectional size of the standoffs by about 35%. In some implementations, a cross-sectional size of the threaded holes is greater than a cross-sectional size of the standoffs by about 35%.

In some implementations, a shape of the holes in the shielding panels is a rounded rectangle.

In some implementations, the standoffs are arranged on at least two sides of the frame, thereby forming the datum structure in at least two intersecting planes of three-dimensional space.

In some implementations, neighboring edges of first and second shielding panels of the shielding panels form a gap. The X-ray device can further include: a metal piece having fasteners configured to attach the metal piece with the frame; and the shielding piece being sized and positioned to prevent X-rays from passing (i) through the gap and (ii) through holes in the first and second shielding panels on either side of the gap, which are usable to couple the first and second shielding panels with the frame. The metal piece can be shaped to receive a shielding piece including lead.

In some implementations, the X-ray device further includes additional shielding disposed on the shielding.

In some implementations, the X-ray device further includes corner guards including angled sheets of lead extending between two adjacent faces of the shielding panels. The corner guards can be angled at an acute angle between the two adjacent faces of the shielding panels, and edges of the corner guards are chamfered at the acute angle.

In some implementations, the X-ray device further includes a sheet on which each corner guard of the corner guards is attached. The sheet can be attached to the frame.

In some implementations, the X-ray device further includes brackets and standoffs. The standoffs can include threaded holes, and fasteners that attach the brackets to the standoffs can be bolts configured to mate with the threaded holes in the standoffs.

Particular embodiments of the subject matter described in this specification can be implemented to realize one or more of the following advantages. The systems and apparatuses described can provide highly efficient X-ray shielding, while preventing direct contact with lead by a user. Further, the design and assembly process can be quicker and less expensive by avoiding iterative processes for assembling the X-ray shielding device.

In some implementations, the systems and apparatuses described can be assembled without iterative processes, thereby reducing resources, e.g., equipment and time, to create a CT device and increasing a scalability of the CT device. For example, the exterior panels can be more robustly mounted with reduced clearance compared to assemblies without the datum structure. The more robustly mounted exterior panels can have a reduced likelihood of shifting during shipment or use. As another example, the CT device can accommodate larger objects for scanning if the size can be increased without increased error in alignment.

DETAILED DESCRIPTION

FIG.1Ashows a perspective view of an example of an X-ray shielding device100. The X-ray shielding device100can enclose a system that generates X-rays and prevents the generated X-rays from escaping from the X-ray shielding device100. Panels made from lead, which is one of the most efficient X-ray absorbing materials, can surround the system. However, there are gaps114where panels are joined together, e.g., between panels on the same face116of the X-ray shielding device100and at corners118of the X-ray shielding device100.

Although obtaining efficient X-ray shielding does not require the X-ray shielding device100to be perfectly sealed, e.g., since the X-rays may only travel in certain directions based on the geometry of the X-ray shielding device100and the enclosed system, adding shielding in front of the gaps114between panels of lead can improve the shielding efficiency. However, using lead to support structural components presents problems, due to lead's heaviness and softness. Accordingly, the present disclosure describes a datum structure for assembling an X-ray shielding device100that does not use lead for structural support, as well as a metal piece with additional shielding that also provides additional structural support.

FIG.1Bshows a cross-sectional and schematic view of an example of an X-ray computed tomography system110within the X-ray shielding device100ofFIG.1A. The X-ray computed tomography system110includes X-ray source101configured to emit X-rays102towards scintillator103. As X-rays102pass through scan target107and collide with scintillator103, scintillator103absorbs the X-rays102and emits visible light108, which generates an image. In some implementations, X-ray computed tomography system110can include one or more mirrors, e.g., folded optics, to reduce the optical path length and thus size of the X-ray shielding device100.

In various example implementations, the X-ray computed tomography system110may include motion system106configured to move, reposition, manoeuvre, or otherwise manipulate the detector105and/or scan target107relative to the X-ray source101. Furthermore, X-ray computed tomography (CT) system110may be an X-ray CT device. In various examples, X-ray source101may emit an X-ray beam, which may be a pencil beam, fan beam, cone beam, etc.

The shielding efficiency can be defined as the total energy of X-rays that escape the X-ray shielding device divided by the total energy of radiation produced by the X-ray source. For example, in some implementations, X-ray shielding device100only lets escape about one millionth of the energy of the generated X-rays. In some implementations, the shielding efficiency is selected to comply with regulations of the United States Food and Drug Administration (FDA) with a margin, e.g., stricter than the regulations.

FIG.2Ashows a perspective view of an example of a frame120and a datum structure130of the X-ray shielding device100ofFIG.1A. The frame120can include multiple sheets of metal, such as steel, that form six faces121a,121b,121c,121d,121e, and121fof the frame120. In some implementations, the frame has a rectangular prism shape, with top, bottom, and side faces.

In some implementations, at least some of the faces121a-fhave indents formed by the sheets of metal not being completely planar, e.g., face121bincludes two sheets125aand125b,each of which include at least two 90° bends on the surface of the sheet. These bends can increase a stiffness of the sheets of metal, thereby turning them into structural components. At least some of the faces121a-fcan have an indent that creates space for fasteners between the frame120and exterior components.

The sheets of metal forming faces121a-fcan each have holes126, through which fasteners can extend. In some implementations, the holes126are threaded to mate with threaded fasteners.

The datum structure130is marked by the dashed lines to indicate the linear alignment of standoffs128, which in combination with the spacing between standoffs, makes the standoffs a datum structure130. In some implementations, the standoffs128can be pressed into sheet metal or be blind, through hole, and/or threaded standoffs. For example, standoffs128can be pressed into sheet metal of the frame120by a sheet metal fabricator. With sufficient force, the standoffs128bond to the sheet metal and permanently remain in place. In some implementations, the standoffs128are threaded to mate with the frame120.

The datum structure130defines various points for aligning the frame120with the panels of the X-ray shielding device100and other components such as brackets and rails, e.g., holes in each of the sheets of metal forming the frame and panels being aligned and components of the datum structure130passing through the holes.

The datum structure130aids in the alignment of the exterior panels of the X-ray shielding device100, which will be discussed in reference toFIGS.4A-4D. In other words, the datum structure130can be three-dimensional, and the standoffs128forming the datum structure130can be arranged in at least three intersecting planes. In some implementations, the datum structure130can be arranged in fewer than three intersecting planes, e.g., two parallel planes or two intersecting planes.

At least one of the sheets122making up a side face can include an opening124for a door for letting objects pass within and out of the X-ray shielding device100.

FIG.2Bshows a perspective view200of an example of exterior panels138a,138b,and138cof the X-ray shielding device100ofFIG.1Awith a door129. The exterior panels138are made from a material other than lead, so that it is safe for human contact. In some implementations, the exterior panels138a-cinclude metal, plastic, and/or other materials

FIGS.3A-3Crespectively show perspective and cross-sectional views300a,300b,and300cof standoffs128passing through shielding panels132(which can include lead in various forms) from the X-ray shielding device100ofFIG.1A. In perspective view300a,the standoffs128pass from the frame120and through the shielding panels132.

In some implementations, the shielding panels132include lead or a lead-free shielding material, e.g., a plastic impregnated with X-ray absorbing particles. For example, most of the shielding panels132can be pure lead or lead sandwiched between two layers of another material, and the remaining shielding panels can be lead-free. For example, lead-free, secondary shielding panels can cover portions of shielding panels132that include lead but have small leaks, such as holes or seams.

Due to the high density of lead, panels made from pure lead can be prone to bending and drooping along the direction of gravity while being assembled. To reduce the weight of the X-ray shielding device100and to avoid uneven shielding panels132, the size and thus weight of the shielding panels132can be limited. For example, some or all the shielding panels132can be less than a limiting weight of between 20 and 40 kilograms, e.g., less than 23 or 39 kilograms. In order to maintain the weight of each shielding panel132below a threshold, a single face131can include multiple shielding panels132. The specific weight limit can depend on the average strength of the workers in a given country, the workers' health and safety regulations in a given country, or both.

Although steel and lead provide important characteristics, e.g., structural support and X-ray absorption, respectively, manufacturing laminates of steel and lead can be less precise compared to other metals. Accordingly, providing a nonzero tolerance for interconnecting lead and steel laminates can facilitate aligning the lead and steel laminates

The standoffs128pass through holes in the shielding panels132, where the holes are sized to provide a tolerance for the standoffs. For example, as depicted in cross-sectional view300b,holes134in the shielding panels132can be slots with a 11 mm width W1along the Y axis, and the standoffs128can have a rounded-rectangular cross-section with a 7.12 mm width W2along the Y axis, providing a radial clearance C of about 2 mm relative to the slot-shaped hole134. In some implementations, the radial clearance is determined by percentage of the standoff128, e.g., the holes134in the shielding panel132are sized to provide a percentile radial clearance of the width of the standoff128, e.g., 35% of the width of the standoff128. In some implementations, there is also a radial clearance for the standoffs128relative to the holes in the shielding panels132along a direction perpendicular to the width, e.g., the Z axis.

Using slots in the shielding panels132, e.g., a rounded rectangle with a longest edge along the direction of the gap (Y axis in this example), can provide more lateral tolerance compared to using circular holes. If the cross-sectional size of the holes134is greater than the cross-sectional size of the standoffs128by a certain amount, e.g., 2 mm, the standoffs128will pass through the holes134despite variations in placement of the holes134in a given shielding panel132resulting from manufacturing of the given shielding panel132.

As another example, each of the standoffs128and the holes134in the shielding panels132can have a circular cross-section, where the radius of the cross-section of the holes in the shielding panels132is greater than the radius of cross-section of the standoffs128.

To connect the shielding panels132to the frame120, the standoffs128must be long enough to at least pass through the shielding panels132. As shown in cross-sectional view300c,the standoff128has a first length L1along the X axis that is greater than a second length L2of the shielding panel132along the X axis, such that the standoff128can pass through the shielding panel132to connect the exterior panel138to the frame120.

As indicated by the different widths along the X direction of an exterior end128aof a standoff and an interior end128bof a standoff, the exterior end128aof the standoff can be long enough to attach to an exterior panel138through a bracket, while the interior end128bof the standoff is nearly flat after having been pressed into the sheet metal of the frame120. In some implementations, the interior end128bof the standoff has a polygonal, e.g., hexagonal, cross section, e.g., along the X axis inFIG.3C, to prevent rotation of the standoff128.

In some implementations, the shielding panel132is a laminate, e.g., made of one or more materials, such as at least two materials bonded together to form a laminate. For example, shielding panel132can be a laminate formed by a lead layer136asandwiched by layers136bwith adhesive305at the interface between the lead layer136aand the layers136b.Layers136bcan be made from a material stiffer than lead, e.g., steel, to provide extra structural support. When the shielding panel132is a laminate, the length L1of the standoff128can be greater than the second length L2of the shielding panel132including the length of the layers136b.When the shielding panel132is a single layer of lead, the length L1of the standoff128can be greater than a third length L3of lead layers136a.

In general, the length L1of the standoff128is greater than the shielding panel132, including when the shielding panel132includes one or more laminates136, to ensure that the brackets for the exterior panels138do not touch the shielding panels132. Accordingly, the location of the brackets for the exterior panels138and the exterior panels138are not affected by variations in the thickness and/or flatness of the shielding panels132.

The laminates136can be sheets substantially parallel to the shielding panels132. The cross-sectional size of the laminates136can be approximately the same as the shielding panels132, e.g., smaller than the shielding panels132by about 0.5 millimeters. In some implementations, the laminate136is attached to the shielding panel132with an adhesive305.

The length of the standoffs L1is greater than a maximum thickness possible for the given shielding panel, e.g., length L2, due to variations in thickness resulting from the manufacturing of the given shielding panel. In some implementations, the length L2of the shielding panel132along the X axis can be relatively even, e.g., the same within 0.5 millimeters. Due to lead's softness, lead is relatively easy to machine lead panels of various thicknesses.

FIG.3Dshows a cross-sectional view300dof a shielding panel132of the X-ray device ofFIG.1Aheld in place by fasteners135a.Fasteners135aare located around the perimeter of each shielding panel132as depicted inFIG.3A. InFIG.3A, the standoffs128are represented by smaller circles, and larger circles correspond to washers135bwith a raised center corresponding to the fasteners135a.

The holes134in shielding panel132can have a variety of purposes. For example, some of holes134are sized and arranged to allow standoffs128to couple to the frame120to brackets140for mounting the exterior panels138, and some of holes134are sized and arranged to allow fasteners135ato couple the shielding panels132to the frame120.

As depicted inFIG.3D, a fastener135a,such as a bolt, extends completely through the shielding panel132to attach to the frame120. In this example, the shielding panel132is a laminate with a lead layer136asandwiched by layers136b.The washers135bare on an exterior side of the shielding panel132and surround the fastener135a.Washers135bdistribute the load of fastener135aon the shielding panel. Fasteners135care on an interior side of the of the shielding panel132and surround the fastener135a.In some implementations, fasteners135care nuts pressed into the sheet metal of the frame120.

Given the difficulty with precisely manufacturing lead shielding panels132, the holes134in the shielding panels and fasteners135aare sized to provide a clearance around the fastener135a.InFIG.3D, clearances C1and C2are the vertical clearances, e.g., along the Z axis, above and below, respectively, between the fastener135aand hole134of the shielding panel132. In some implementations, there is a clearance between the fasteners135aand holes134in either one or both of the horizontal directions.

FIGS.4A and4Bare perspective and close-up views400aand400bof brackets140from the X-ray shielding device100ofFIG.1A. The datum structure130provides mounting locations for precisely mounting brackets140, as well as door motion and locking components. The brackets140a-140gcan hold the exterior panels138(pictured inFIG.2B) in place, e.g., attached to the frame120via fasteners, such as standoffs or bolts. Each bracket140can attach to at least two exterior panels138. Bracket140ccan include holes that precisely align with the datum structure130, such that standoffs128can extend from the frame120through the shielding panels132to mount the brackets. Using the datum structure130can also increase the repeatability of methods of accurately aligning the various components of the X-ray shielding device100.

In some implementations, as depicted in close-up perspective view400b,some of the brackets, e.g., brackets140a,140b,140fand140g,include edges143aand143bthat meet at a right angle to attach exterior panels138that meet at a right angle. One of the edges, e.g., edge143a,can be ridged. In some implementations, some brackets, e.g., bracket140gcan hold two exterior panels, e.g., exterior panels138aand138c,with different orientations while only being attached to standoffs128.

In some implementations, the X-ray shielding device100includes door guide rails142, which are configured to allow a sliding door, e.g., door129, to slide along a horizontal direction, e.g., the X axis in this example, to both cover and uncover the opening124. Additionally, the X-ray shielding device100can include a door interlock144, which locks the sliding door into place when covering the opening124. When the sliding door is latched into place by the door interlock144, the sliding door is in a position that reduces X-ray leakage compared to other positions.

FIGS.4C and4Dare cross-sectional and close-up views400cand400dof the shielding panels and brackets ofFIGS.4A and4B. As can be seen in both views400cand400d,the bracket140is attached to standoffs128, which in turn are part of the frame120. A small gap145, e.g., 1.5-3 mm, allows for variation in the thickness and flatness tolerance deviations of the shielding panel132without affecting the position of the bracket140. The size of the gap145depends on material thicknesses of the shielding panels132and length(s) of the standoffs128.

FIGS.5A and5Bshow cross-sectional views500aand500bof examples of a metal piece having fasteners configured to attach the metal piece with the frame120within the X-ray shielding device100ofFIG.1A. The metal piece provides mounting locations for the shielding panels132in addition to the mounting locations of the datum structure130at corners of the X-ray shielding device100.

In some implementations, the metal piece is a C-channel150, e.g., a continuous piece of metal and is called a “C”-channel for having a shape like the letter “C.” For example, the C-channel150can be composed of two parallel segments151a151c(extending in a first direction) connected by a segment151b(extending in a second direction) perpendicular to both segments151aand151cand connected at the edges of segments151aand151c.

In general, the metal piece can have various shapes as long as the shape creates room to receive the additional shielding148and includes at least one surface by which the metal piece attaches to the frame120. For example, the shape and location of the metal piece can be selected to cover holes134in the shielding panels132for fasteners135aand standoffs128.

An advantage of using the C-shape is there are two locations where the metal piece attaches to the frame120on either side of the additional shielding148e.g., to the left and right of and below additional shielding148inFIG.5A. As a result, a C-shaped metal piece adds structural support and strength to the frame120and facilitates holding of the weight of the main shielding panels132.

The C-channel150can have associated fasteners, e.g., fastener154, configured to attach the C-channel150to the frame120. In some implementations, the fastener154passes through two aligned holes of the C-channel150and the frame120.

The C-channel150can be disposed between shielding panels132and the frame120where gaps147between neighboring shielding panels132exist. Due to the shape of the C-channel150, e.g., having two segments extending in the direction from the frame120to the shielding panels132(along the Y axis in this example) and another segment parallel to the direction of the gap147between the shielding panels132(along the X axis in this example), additional shielding148can be located between the frame120to the shielding panels132and block the gap147.

The additional shielding148can be attached to a plate152, which is configured to attach to the C-channel150. For example, the plate152can define a hole through which a fastener156can pass and attach to the segment151bof the C-channel150. The plate152can be made of a metal stiffer than lead, e.g., steel. In some implementations, the additional shielding148can be directly attached to the C-channel150without the plate152. However, when the additional shielding148includes lead, creating precise holes for fastening can be easier when using a stiffer metal compared to lead.

FIGS.6A and6Bshow exploded views600aand600bof the C-channel150and additional shielding148ofFIG.5A.FIGS.6A and6Bdepict the C-channel150and additional shielding148but flipped about the Y axis. As depicted inFIGS.6A and6B, the additional shielding fits between the two segments151aand151cof the C-channel150. Holes153in the additional shielding148are aligned with holes155in the C-channel150, such that fasteners156can connect the additional shielding148to the C-channel150.

As visible in exploded views600aand600b,each of the first through third segments151a-151cextends in the third direction perpendicular to both the first and second directions, e.g., a vertical direction along the Z axis in this example. The C-channel150can be long enough in the vertical direction to cover an entire gap between neighboring shielding panels132.

FIG.5Bdepicts a similar view asFIG.5A, with some differences. First, this view is for different side of the X-ray shielding device100, and therefore the orientation is flipped along the X axis. Second, the C-channel158extends longer along the X axis compared to C-channel150. In this example, C-channel158extends far enough along the X axis to span the opening124for the door129. With reference toFIG.2A, the C-channel158is a part of the sheet122, which includes an opening124for the door129. Third, the C-channel158is attached to an additional layer of shielding149, which contacts the exterior panels138.

FIG.6Cdepicts a perspective view600cof the C-channel150ofFIG.5Ariveted to a panel127of the frame120ofFIG.2A. The C-channel150being riveted to the panel127can provide structural reinforcement for the frame120. In some implementations, the C-channel150is riveted to the panel127using flanges on both the top and bottom, e.g., along the Z axis, of the C-channel150.

FIG.7shows a cross-sectional view700of an example of a corner guard160within the X-ray shielding device ofFIG.1A. Similarly to how the additional shielding148prevents strays X-rays from escaping through gaps between neighboring, parallel shielding panels132, the corner guards160can absorb X-rays that would otherwise pass through gaps between neighboring, perpendicular shielding panels132. The corner guards160can include an angled sheet of lead168or another shielding material.

In some implementations, the corner guard160includes a sheet162, which is made of a metal stiffer than lead, such as steel. The sheet162can include holes configured to accept fasteners163, which extend through both the sheets162and a member164. The member164can have an open rectangular shape, e.g., a rectangle with portions from two adjacent sides missing at the point where the two adjacent sides would have met. The metal frame can include portions166that extend from neighboring, perpendicular panels of the frame120, e.g., an L-shaped portion. The portion166can be shaped to receive a sheet162, which is attached to member164, of a corner guard160. For example, the angled edges161aand161bof the angled sheet of lead168can be parallel to each of the L-shaped portions166. The fasteners163can extend through the sheet162, the member164, and the portions166to attach the corner guards160to the frame120. The sheet162and member164can be fastened together to form a more rigid and structural composite member.

In some implementations, the corner guards160are completely within the datum structure130. In other words, the corner guards160are interior rather than exterior to the frame120, e.g., enclosed by portions166of the frame120. The angled sheet of lead168can be chamfered at an acute angle θ, e.g., 30° or 60°, relative to the portions166. The corner guards can be placed in each of the four corners within the X-ray shielding device100.

Referring toFIGS.3B and7, the gap between shielding panels132aand132bcan be reduced by using slots as the shape for holes134. Using slots allows for biasing the shielding panels132up against a blast wall, indicated by the dashed line inFIG.7. For example, shielding panel132acan slide further to the left, e.g., along the X axis, to reduce the gap between the blast wall, e.g., the interior side of the X-ray shielding device100receiving X-ray radiation directly from the X-ray source101. Additionally, the metal piece, e.g., C-channel150, can compensate, e.g., provide additional shielding, for any extra spacing created on the right side of the shielding panel132awhere it meets another shielding panel on the same face. Accordingly, in tandem, the datum structure130and the metal piece provide flexible alignment without reducing the shielding efficiency of the X-ray shielding device100.

Although implementations with a C-channel for the metal piece and doubly chamfered corner guard have been described, other implementations are possible. For example, the metal piece can have a square, rectangular, or circular shape. As another example, the corner guard can have a rectangular shape with one corner being chamfered.

Embodiments of the subject matter and the functional operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Embodiments of the subject matter described in this specification can be implemented using one or more modules of computer program instructions encoded on a non-transitory computer-readable medium for execution by, or to control the operation of, data processing apparatus. The computer-readable medium can be a manufactured product, such as a hard drive in a computer system or an optical disc sold through retail channels, or an embedded system. The computer-readable medium can be acquired separately and later encoded with the one or more modules of computer program instructions, such as by delivery of the one or more modules of computer program instructions over a wired or wireless network. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, or a combination of one or more of them.

To provide for interaction with a user, embodiments of the subject matter described in this specification can be implemented on a computer having a display device, e.g., an LCD (liquid crystal display) display device, an OLED (organic light emitting diode) display device, or another monitor, for displaying information to the user, and a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input.

The computing system can include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. Embodiments of the subject matter described in this specification can be implemented in a computing system that includes a back-end component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a front-end component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an implementation of the subject matter described is this specification, or any combination of one or more such back-end, middleware, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (“LAN”) and a wide area network (“WAN”), an inter-network (e.g., the Internet), and peer-to-peer networks (e.g., ad hoc peer-to-peer networks).

Thus, particular embodiments of the invention have been described. Other embodiments are within the scope of the following claims.