Abstract:
Disclosed herein is a method and apparatus for providing radiation shielding for non-invasive inspection systems. An embodiment of the apparatus may include a radiation shield having a plurality of slats, where each of the plurality of slats comprises a radiation attenuating material. The radiation shield may further include a support structure configured to hold the slats in a non-planar shape. An embodiment of the method may include gathering a plurality of slats, each slat comprising a radiation attenuating material. The method may further include disposing the slats to form a shielding curtain having a non-planar shape. The method may also include positioning the shielding curtain to cover an opening of a scanner.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The technology disclosed herein relates to radiation shielding systems generally, and more particularly, to a method, apparatus, and system for providing radiation shielding for non-invasive inspection systems. 
         [0003]    2. Discussion of Related Art 
         [0004]    Explosive detection systems and other types of inspection systems typically use radiation-based scanners, such as x-ray line scanners, x-ray CT scanners, and coherent x-ray scatter scanners, to examine bags (pieces of passenger baggage) for the presence of one or more alarm objects (explosives, weapons, illegal drugs, contraband, product components, and the like). In certain types of inspection systems, such as explosive detection systems, one or more shielding curtains typically blocks the entrance and exit of an x-ray scanner, since highly concentrated dose of high-energy radiation from the scanner can damage human tissue if the dose is too high. Some shielding curtains (hereinafter, “sheet curtains”) are formed of solid sections of material. More commonly, radiation-shielding curtains (hereinafter, “strip curtains”) are formed of multiple adjoining slats, each of which is aligned with adjacent slats to form a common plane. 
         [0005]      FIG. 1 , a sectional, perspective view of a conventional explosive detection system (EDS)  100 , provides an example of how radiation-shielding curtains are typically arranged. In  FIG. 1 , a conveyor belt  101 , positioned on a base  102 , extends from one end of the EDS  100  to the opposite end of the EDS  100 . The base  102  houses one or more conveyor belt motors (not shown), a computer (not shown), and one or more components of an x-ray scanner  103 . A housing  104  rests on the base  102 . A tunnel  105  formed in the housing  104  extends from one end of the housing  104  to the opposite end of the housing  104 , and encloses the conveyor belt  101 . 
         [0006]    The x-ray scanner  103 , positioned within a center portion of the housing  104 , includes a scanning area  106 , into which the conveyor belt  101  introduces one or more scannable objects. Configurations of the scanning area  106  will vary depending on the type of x-ray scanner used. For example, if an x-ray CT scanner is used, the scanning area  106  will be enclosed by a circular, movable gantry, to which an x-ray source and one or more detectors are fixedly attached. 
         [0007]    Multiple, closely-spaced, strip curtains  107  hang suspended within the housing  104  over a portion of the conveyor belt  101 . The portion of the conveyor belt over which the strip curtains  107  are positioned extends from an entrance  108  of the EDS  100  to an entrance  109  of the scanning area  106 . In a like manner, parallel, planar rows of strip curtains  110  hang suspended within the housing  104  over another portion of the conveyor belt  101 . This other portion of the conveyor belt  101  extends from the exit  111  of the scanning area  106  to the exit  112  of the housing  104 . 
         [0008]    In use, pieces of luggage (hereinafter, “bags”) may be loaded onto the conveyor belt  101  at the entrance  108  of the tunnel  105 . Supported by the conveyor belt  101 , the bags proceed through the EDS  100  in the direction of arrow  113  (from the EDS  100  entrance  108  to the EDS  100  exit  112 ). Enroute through the EDS  100 , each bag passes through the scanning area  106  and is scanned by the x-ray scanner  103 . After being scanned, the bags are transported by the conveyor belt  101  to the EDS  100  exit  112  and ejected from the EDS  100 . 
         [0009]    Aligning strip curtains in a common plane in the conventional manner, as shown in  FIG. 1 , has disadvantages. Chief among such disadvantages is that bags occasionally jam as they pass through the shielding curtains. When shielding curtains are arranged in parallel, planar rows, jamming occurs because most or all of the slats will contact a bag simultaneously, which traps the bag(s) in the strip curtain(s) even though the conveyor belt supporting the bag(s) continues to move. Another disadvantage associated with conventional strip curtains, such as those illustrated in  FIG. 1 , is that the slats from one strip curtain often entangle the slats of one or more other strip curtains. 
         [0010]    One or more solutions are needed, which attenuate radiation produced by a radiation-based scanner while simultaneously permitting objects to enter and exit the scanner without jamming. 
       BRIEF DESCRIPTION 
       [0011]    Embodiments of the invention overcome the disadvantages associated with the related art and meet the needs discussed above. For example, embodiments of the invention provide a radiation shield, and configurations thereof, that permit bags or other scannable objects to enter and exit a radiation-based scanner without jamming, while simultaneously confining radiation to a scanning area of the scanner. 
         [0012]    Relatively simple and cost-effective to manufacture and install, shielding curtains constructed and configured in accordance with embodiments of the present invention provide advantages that render them suitable for use in security applications, manufacturing applications, medical applications, etc. The solutions provided by such shielding curtains, and configurations thereof, afford several advantages, or technical effects. Illustratively, these advantages include, but are not limited to, significantly fewer bag jams, increased baggage throughput, reduced maintenance costs, and/or operating costs—all as compared with conventional shielding curtains and conventional shielding curtain configurations. 
         [0013]    Embodiments of the invention increase baggage throughput by creating rows of non-planar passive shielding curtains. Each non-planar passive shielding curtains may comprise any suitable geometric shape. In one embodiment, each non-planar passive shielding curtain comprises slats of radiation-attenuating material arranged in a chevron-shape. The chevron configuration has at least two advantages. First, a chevron configuration reduces the number of slats that simultaneously contact a bag as the bag moves through the shielding curtain. The chevron configuration also reduces the force of the initial impact of the bag as it moves through the curtains and therefore reduces the occurrence of bag jams while still providing radiation protection. Reducing or eliminating the number of bag jams in this manner increases the number of bags a radiation-based inspection system can process in a given amount of time. 
         [0014]    Many factors will affect the bag jam rate. Exemplary factors include, but are not limited to: whether the apex of the non-planar radiation shield is directed toward a scanning area or toward a portal through which bags enter or exit the scanner; the degree of the curtain angle; how many rows of shielding curtains will be used; how far apart the curtain rows are spaced from each other; and the height, weight, and width of the slats used to form each shielding curtain. In an embodiment of the invention, at least one or more of these exemplary factors is optimized to reduce the occurrence of bag jams. 
         [0015]    Shielding curtains constructed and configured in accordance with embodiments of the invention may attenuate any known type of radiation. Non-limiting examples of the types of radiation that may be attenuated include: X-ray radiation, microwave radiation, laser radiation, and the like. 
         [0016]    An embodiment of the invention provides a novel radiation shield. The radiation shield may include a plurality of slats, each comprised of a radiation attenuating material, and a support structure (or means for holding). The support structure (or means for holding) may be configured to hold the slats in a non-planar shape. 
         [0017]    Another embodiment of the invention provides a method of constructing and/or installing a novel radiation shield. The method may include: gathering a plurality of slats, each comprised of a radiation attenuating material; disposing the slats to form a strip curtain having a non-planar shape; and positioning the strip curtain to cover an opening of a scanner. 
         [0018]    The foregoing has outlined rather broadly the features of embodiments of the invention so that the following detailed description may be better understood. Additional features and advantages of various embodiments of the invention that form the subject matter of the appended claims are described below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    For a more complete understanding of the technology described herein, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
           [0020]      FIG. 1  is a sectional, perspective view of a conventional explosive detection system illustrating the layout and components of the explosive detection system; 
           [0021]      FIG. 2  is a top view of a radiation shield configured according to an embodiment of the invention; 
           [0022]      FIG. 3  is a perspective view of a radiation shield configured according to another embodiment of the invention; 
           [0023]      FIG. 4  is a perspective view of a radiation shield configured according to another embodiment of the invention; 
           [0024]      FIG. 5  is a perspective view of an exemplary x-ray based scanner for use with a non-invasive inspection system, which may be configured to include one or more non-planar radiation shields; 
           [0025]      FIG. 6  is a block schematic diagram of a scanner that may be used in an inspection system, which is configured according to an embodiment of the invention; and 
           [0026]      FIG. 7  is a flowchart of an embodiment of a method of constructing and configuring a radiation shield. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    Reference is made herein to the accompanying drawings briefly described above, which show by way of illustration various embodiments of the invention. Persons of ordinary skill in the above-referenced technological field will recognize that other embodiments may be utilized, and that various changes may be made without departing from the scope of the claimed invention. 
         [0028]    As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” includes plural elements or steps, unless exclusion of such plural elements or steps is explicitly recited. 
         [0029]      FIG. 2  is a top view of an embodiment of a radiation shield having four strip curtains, each arranged in a non-planar shape. Any type of non-planar (e.g., three-dimensional) shape may be used, a non-limiting example of which is a chevron-shape. As used herein, “chevron-shape” refers to a “V,” “U,” inverted “V,” or inverted “U” arrangement of radiation shielding material. As used herein, “radiation shield” refers to any configuration of radiation attenuating material configured to attenuate an amount of radiation leakage and/or scatter radiation that may occur during operation of a radiation-based scanner. The term “scanner” refers to any type of hardware and/or related software (i.e., linear x-ray, computed tomography (CT), coherent x-ray scatter, laser, magnetic resonance imaging (MRI), etc.) configured to generate a digital representation of an object for storage in a computer-readable medium and/or for analysis by a computer. The term “strip curtain” refers to a grouping of slats of radiation attenuating material. The term “radiation attenuating material” refers to any material that absorbs or reflects radiation including, but not limited to, aluminum, antimony, bismuth, barium, cadmium, copper, iron, iodine, lead, mercury, nickel, silver, thallium, tantalum, tellurium, tin, tungsten, uranium, and zinc, either alone or in combination. The term “slat” refers to a thin piece of radiation attenuating material having a length greater than its width. 
         [0030]    Referring to  FIG. 2 , a radiation shield  200  includes a plurality of flexible (or semi-flexible) slats of radiation attenuating material  214 , and means for holding the flexible slats  214  to form a strip curtain ( 202 ,  203 ,  204 , and  205 ) having a non-planar shape. In an embodiment, the holding means comprises a frame  201  and a plurality of curtain supports  212  from which one or more non-planar strip curtains  202 ,  203 ,  204 ,  205  hang. In an airport security application or an engineering application, the non-planar strip curtains may be suspended over a conveyor belt  206 , which may move objects in either direction indicated by the double-ended direction arrow  230 . Also as used herein, “object” refers to anything that can be imaged by a scanner. Non-limiting examples of an “object” include a bag, a medical patient, a commercial product, etc. The term “bag” refers to a piece of baggage, and the term “baggage” refers to all of a traveler&#39;s luggage and personal belongings. 
         [0031]    In a medical application, the non-planar strip curtains  212  may be suspended over a portion of a support structure that supports a medical patient (or a portion thereof). Non-limiting examples of a support structure include a bed, a table, a stretcher, a gurney, etc. As used herein, “gurney” refers to a mobile bed with wheels designed for transport of patients in hospitals and ambulances. 
         [0032]    Referring again to  FIG. 2 , the frame  201  may include two substantially parallel, longitudinally extending beams  207  and  208 . The beams  207 , 208  may be braced with one or more lateral support members  209 . Any type of known means for fastening (e.g., a weld, a bolt, screw, etc.) can be used to couple the lateral support member(s)  209  with one of the beams  207  and  208 . The frame  201  may further include two upright support members  210  and  211 , which support the beams  207  and  208  above the conveyor belt  206 . 
         [0033]    The frame  201  may further include one or more curtain supports  212 , which, in an embodiment, may be cylindrical rods that lie orthogonally across the beams  207  and  208 . Each curtain support  212  may fixedly or adjustably couple with the beams  207  and  208 . In turn, an upper end of each slat  214  may couple with one of the curtain supports  212  via one or more fasteners  213 . 
         [0034]    Each non-planar strip curtain  202 ,  203 ,  204  or  205  may include multiple curtain supports  212 . For example, in one embodiment, each non-planar strip curtain  202 ,  203 ,  204 , and  205  includes eight curtain supports  212 . In other embodiments, the number of curtain supports  212  included in each non-planar strip curtain  202 ,  203 ,  204 , and  205  may be greater or less than eight. 
         [0035]    Each slat  214  may comprise any radiation attenuating material or combination of materials known to a skilled artisan. Such a material may have a unique radiation transmission attenuation factor, which will vary depending upon the specific embodiment. In an embodiment, the radiation attenuating material is generally flexible to permit each slat  214  to flex slightly when pushed by a bag. In alternative embodiments, the radiation attenuating material may be weighted and/or rigid. 
         [0036]    Referring again to  FIG. 2 , each non-planar strip curtain  202 ,  203 ,  204 , and  205  includes a base  215  and an apex  216 . In an embodiment, the base  215  is formed by two co-planar slats, and the apex  216  is formed either by a single slat or by two co-planar slats. The base  215  is distinguished from the apex  216  in that the two co-planar slats that form the base  215  are separated by a greater lateral distance (as measured orthogonally to a longitudinal center axis  240 ) than the co-planar slat(s) that form the apex  216 . Additionally, the base  215  is vertically separated (as measured along the longitudinal center axis  240 ) from the apex  216 . When configured in this manner, each non-planar strip curtain  202 ,  203 ,  204 , and  205  has a height (measured orthogonal to the conveyor belt  206 ), a width (measured parallel to a width of the conveyor belt  106 ), and a depth (measured along the longitudinal center axis  240  from a plane passing through the base slats to a plane passing through the apex slat(s)). 
         [0037]    The chevron-shape of each strip curtain  202 ,  203 ,  204 , and  205  is formed by arranging slats  214  in a predetermined pattern such that the slats  214  are generally longitudinally aligned (as measured along the longitudinal center axis  240 ) and laterally staggered (as measured orthogonal to the longitudinal center axis  240 ). 
         [0038]    In an embodiment, “longitudinally aligned” refers to one of two arrangements of slats. In a first arrangement, the centers of slats in one shielding curtain are generally aligned with the centers of slats in a second (adjacent) shielding curtain. In a second arrangement, the centers of slats in one shielding curtain are offset from the centers of slats in a second (adjacent) curtain. This second (offset) arrangement staggers the gaps (if any) between the curtain slats from row to row to prevent the gaps from being aligned and therefore reduce radiation leakage. 
         [0039]    In an embodiment, “laterally staggered” refers to one of two arrangements. In a first arrangement, the side edges of slats within a shielding curtain are overlapped with each other so that no gaps appear between neighboring curtain slats. In a second arrangement, the side edges of slats within a shielding curtain are not overlapped. In this second arrangement, the side edges of slats within a shielding curtain may be separated by a gap. 
         [0040]    In other words, one or more slats  214  forming the apex  216  may be attached to a center portion of a first curtain support  217 . A first pair of slats  221 , comprised of two slats  214  that are laterally spaced at about equal distances from the longitudinal center axis  240  of the frame  201 , may be coupled with a second curtain support  218 , which longitudinally adjoins the first curtain support  217 . A second pair of slats  222 , comprised of two slats  214  that laterally spaced at greater distances from the longitudinal center axis  240  than the first pair of strip curtains  220 , may be coupled with a third curtain support  219 , and so on, until a final pair of slats  223  having the greatest lateral spacing from the longitudinal center axis  240  are coupled with a final curtain support  231 . In an embodiment, the final curtain support  231  is separated from the first curtain support  217  by one or more curtain supports disposed therebetween. 
         [0041]    As illustratively shown in  FIG. 2 , such an arrangement of slats causes a curtain angle  225  to be formed, which determines how sharply the base  215  of each strip curtain  202 ,  203 ,  204 ,  205  tapers to its apex  216 . Two intersecting (imaginary) lines may define the curtain angle  225 . The first line  229 , which orthogonally intersects the longitudinal center axis  240 , may be drawn tangent the apex  216 . The second line  270 , which passes through the intersection of the first line  229  and the longitudinal center axis  240 , may be drawn generally along a sloping face of the non-planar strip curtain  202  to be tangent an outer edge of one of the pair of slats  223  that form the base  215 . In an embodiment, an exemplary curtain angle is about 8.0 degrees, but in alternative embodiments, lesser and greater curtain angles may also be used. 
         [0042]    Still referring to  FIG. 2 , one or more predetermined curtain spacings  226  may separate two or more of the non-planar strip curtains  202 ,  203 ,  204 , and  205  from each other. The amount of each curtain spacing  226  will vary depending on the embodiment and the type of application. Illustratively, the curtain spacing  226  may be measured as the distance separating one base strip curtain  227  (in strip curtain  205 ) from another adjacent base strip curtain  228  (in strip curtain  204 ). In an embodiment, an exemplary curtain spacing  226  measures about 152.40 mm, but other curtain spacings are possible. 
         [0043]    Referring now to  FIGS. 1 and 2 , the apexes  216  of all or some of the non-planar strip curtains  202 ,  203 ,  204 ,  205  may be directed toward a scanning chamber  106  of a scanner  103 . In such an embodiment, the apexes  216  of all or some of the non-planar strip curtains  202 ,  203 ,  204 ,  205  may be located nearer the chamber  106  than the bases  215  of each non-planar strip curtain. In alternative embodiments, the apexes  216  of all or some of the non-planar strip curtains  202 ,  203 ,  204 ,  205  may be directed away from the scanning chamber  106  of the scanner  103 . In such alternative embodiments, the bases  215  of all or some of the non-planar strip curtains  202 ,  203 ,  204 ,  205  may be located nearer the chamber  106  than the apexes  216  of all or some of the non-planar strip curtains  202 ,  203 ,  204 ,  205 . 
         [0044]      FIGS. 3 and 4  are perspective views of embodiments of non-planar radiation shields  300  and  400 , respectively. These views, as well as the top view shown in  FIG. 2 , illustrate exemplary frames and curtain supports, which allow quick changes from one curtain embodiment (or configuration) to another during testing. Skilled artisans will appreciate that various other means for supporting the novel configurations of shielding curtains described herein (for testing and/or use in an operational medical inspection system or explosive detection system) are possible and contemplated.  FIG. 3  is a perspective view of a radiation shield  300  having six shielding curtains  301 ,  302 ,  303 ,  304 ,  305 ,  306 , with each shielding curtain arranged in a chevron pattern, according to another embodiment of the invention. Each non-planar shielding curtain  301 ,  302 ,  303 ,  304 ,  305 ,  306  includes an apex  316  and a base  324 , as previously described above with respect to  FIG. 2 . 
         [0045]    In  FIG. 3 , the radiation shield  300  includes a frame  301  to which one or more curtain supports  312  are coupled. The six non-planar strip curtains  301 ,  302 ,  303 ,  304 ,  305 ,  306 , each formed of one or more slats  314 , hang suspended from the one or more curtain supports  312  over a conveyor belt  306  (or other type of means for supporting an object for scanning). The conveyor belt  306  may be configured to move objects in either direction indicated by the double-ended direction arrow  330 . 
         [0046]    The frame  201  may include two substantially parallel, longitudinal beams  307  and  308  that are braced with one or more lateral support members  309 . The lateral support member(s)  309  are attached at either end to one of the beams  307  and  308  using any type of known fastening means (e.g., a weld, a bolt, screw, etc.). The frame  201  may further include two upright support members  310  and  311 , which support the beams  307  and  308  above the conveyor belt  306 . As noted above, the frame  201  may further include one or more adjustable or fixed curtain supports  312 , which may fixedly or adjustably couple with the beams  307  and  308  at about right angles. 
         [0047]    In the embodiment shown in  FIG. 3 , the non-planar strip curtains  301 ,  302 ,  303 ,  304 ,  305 ,  306  are paired into the following three groups: a first curtain pair consisting of strip curtains  301 , 302 ; a second curtain pair consisting of strip curtains  303 , 304 ; and a third curtain pair consisting of strip curtains  305 , 306 . Each of these first, second, and third curtain pairs has an identical (or similar) internal curtain spacing  330 ,  331 , and  332 , respectively, which are further defined below. Additionally, each of the first, second, and third curtain pairs are separated from each other by spacings  340  and  341  (also defined further below). For example, spacing  340  separates the first curtain pair  301 , 302  from the second curtain pair  303 , 304 . Another spacing  341  may separate the second curtain pair  303 , 304  from the third curtain pair  305 , 306 . 
         [0048]    In an embodiment, each of the internal curtain spacings  330 ,  331 , and  332  that separate individual strip curtains are smaller than the spacings  340 , 341  that separate the first, second, and third curtain pairs. 
         [0049]    The internal curtain spacings  330 ,  331 , and  332  may be measured as follows. The internal curtain spacing  330  may be the distance between a base slat  351  of the strip curtain  301  and a base slat  352  of the strip curtain  302 . The internal curtain spacing  331  may be the distance between a base slat  353  of the strip curtain  303  and a base slat  354  of the strip curtain  304 . The internal curtain spacing  332  may be the distance between a base slat  355  of the strip curtain  305  and a base slat  356  of the strip curtain  306 . 
         [0050]    The spacings  340  and  341  between the first, second, and third curtain pairs may be measured as follows. The spacing  340  may be the distance between a base slat  352  of the strip curtain  302  and a base slat  353  of the strip curtain  303 . The spacing  341  may be the distance between a base slat  354  of the strip curtain  304  and a base slat  355  of the strip curtain  305 . 
         [0051]      FIG. 4  is a perspective view of a radiation shield  400  having eight strip curtains  401 ,  402 ,  403 ,  404 ,  405 ,  406 ,  407 ,  408 , with each strip curtain arranged in a chevron pattern that has a predetermined curtain angle, according to another embodiment of the invention. In  FIG. 4 , the eight non-planar shielding curtains  401 ,  402 ,  403 ,  404 ,  405 ,  406 ,  407 ,  408 , each formed of a plurality of slats  414 , are arranged on a plurality of curtain supports  412  that are coupled with a frame as described above. The slats  414  hang suspended above a conveyor belt  416 , which may move objects in either direction indicated by the double-ended direction arrow  430 . Additionally, the eight strip curtains  401 ,  402 ,  403 ,  404 ,  405 ,  406 ,  407 ,  408  are nested. As used herein, “nested” refers to an arrangement in which an apex of one strip curtain is positioned between a base and apex of another longitudinally aligned strip curtain, as illustratively shown in  FIGS. 3 and 4 . Depending on the embodiment, two or more strip curtains may be nested in single or multiple groupings. By way of example,  FIG. 3  illustrates multiple groupings of nested pairs of strip curtains, while  FIG. 4  illustrates a single grouping of nested strip curtains. On the other hand, the strip curtains illustrated in  FIG. 2  would not be considered nested since the apex of each succeeding strip curtain is positioned outside of the base of the next adjacent strip curtain. 
         [0052]    Referring now to  FIG. 5 , a example of an inspection system  500  is shown with its housing and shielding curtains removed for clarity. It will be appreciated that the embodiments of the non-planar strip curtains described herein may be positioned between the entrance  508  of the inspection system  500  and the scanner  503 , and between the scanner  503  and the exit  518  of the inspection system  500 . 
         [0053]    The inspection system  500  may be configured to include one or more of the new non-planar shielding curtains described herein. The inspection system  500  includes a CT scanner  503  having a rotatable gantry  502 . As used herein, “inspection system” refers to a machine having a scanner that scans an object to obtain scan data that is characteristic of the object (and/or its contents), and/or that analyzes the scan data using a computer to determine whether the object comprises and/or contains one or more alarm objects. 
         [0054]    The rotatable gantry  502  has an opening  504  therein, through which packages or bags  516  may pass. The rotatable gantry  502  houses an x-ray source  506  as well as a detector assembly  508  having scintillator arrays comprised of scintillator cells. A conveyor system  510  is also provided. The conveyor system  510  includes a conveyor belt  512  supported by structure  514  to automatically and continuously pass packages or bags  516  to be scanned through opening  504 . Directional arrow  520  indicates the direction in which the conveyor belt  512  rotates. 
         [0055]    Objects  516  are fed through opening  504  by conveyor belt  512 . Imaging data is then acquired, and the conveyor belt  512  transfers the packages  516  from the gantry opening  504  in a controlled and continuous manner. As a result, inspectors, baggage handlers, and other security personnel may non-invasively inspect the contents of packages  516  for alarm objects. The term “alarm object” refers to any substance or thing that an inspection system is configured to detect. Non-limiting examples of alarm objects include explosives, illegal drugs, hazardous substances, product components, and the like. Additional aspects of the inspection system  500  are described below with reference to  FIGS. 5 and 6 . 
         [0056]      FIG. 6  is a block schematic diagram of a scanner that may be used in an inspection system configured according to an embodiment of the invention. Referring to  FIGS. 5 and 6  together, the inspection system  500  may be an explosive detection system that includes an x-ray CT scanner. As used herein, “explosive detection system” refers to a particular category of inspection system, configured to detect explosives in baggage. 
         [0057]    Referring again to  FIGS. 5 and 6 , the x-ray CT scanner includes a circular, movable gantry  502 . An x-ray source  506  attached to the gantry  502  projects a fan beam of x-rays  517  across the interior of the gantry  502  to a detector array  508  that is also attached to the gantry  502 . The detector array  508  is formed by a plurality of detector modules  521 , which together sense the projected x-rays that pass through an object  516 . Each detector module  521  comprises an array of pixel elements (pixels). Each pixel comprises in part a photosensitive element, such as a photodiode, and one or more charge storage devices, such as capacitors. Each pixel produces an electrical signal that represents the intensity of an impinging x-ray beam and hence the attenuated beam as it passes through the object  516 . During a scan to acquire x-ray projection data, gantry  502  and the components mounted thereon rotate about a center of rotation  524 . 
         [0058]    Rotation of gantry  502  and the operation of x-ray source  506  are governed by a control mechanism  526  of the inspection system  500 . Control mechanism  526  includes an x-ray controller  528  that provides power and timing signals to an x-ray source  506  and a gantry motor controller  530  that controls the rotational speed and position of gantry  502 . A data acquisition system (DAS)  532  in control mechanism  526  samples analog data from detectors  521  and converts the data to digital signals for subsequent processing. An image reconstructor  534  receives sampled and digitized x-ray data from DAS  532  and performs high-speed reconstruction. The reconstructed image is applied as an input to a computer  536 , which stores the image in a mass storage device  538 . 
         [0059]    Computer  536  also receives commands and scanning parameters from an operator via console  540  that has a keyboard. An associated display  542  allows the operator to observe the reconstructed image and other data from computer  536 . The operator supplied commands and parameters that are used by computer  536  to provide control signals and information to DAS  532 , x-ray controller  528 , and gantry motor controller  530 . In addition, computer  536  operates a conveyor motor controller  544 , which controls a conveyor belt  512  to position object  516  within the gantry  502 . Particularly, conveyor belt  512  moves portions of the object  516  through the gantry opening  504 . 
         [0060]      FIG. 7  is a flowchart of an embodiment of a method  700  of constructing a radiation shield. The method  700  may include a step  701  of gathering a plurality of slats of radiation attenuating material. The gathering step  701  may include ordering, constructing, and/or receiving one or more slats that each comprise a radiation attenuating material. The method  700  may further include a step  702  of disposing the slats to form a strip curtain having a non-planar shape. The step  702  may include one or more additional steps, such as, but not limited to: coupling each of the slats with a curtain support; coupling each curtain support with a frame, among other steps. The method  700  may further include a step  703  of positioning the strip curtain to cover an opening of a scanner. The opening of the scanner may be an entrance opening or an exit opening through which objects pass when traveling into or out of a scanning area of the scanner. 
         [0061]    The construction and arrangement of the curtain shielding assembly, and/or an inspection system that includes an embodiment of the curtain shielding assembly, as described herein and shown in the appended figures, is illustrative only. Although only a few embodiments of the invention have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g. variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the appended claims. 
         [0062]    Accordingly, all such modifications are intended to be included within the scope of the present invention as defined in the appended claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the embodiments of the invention as expressed in the appended claims.