Abstract:
The present specification describes a compact, hand-held probe or device that uses the principle of X-ray backscatter to provide immediate feedback to an operator about the presence of scattering and absorbing materials, items or objects behind concealing barriers irradiated by ionizing radiation, such as X-rays. Feedback is provided in the form of a changing audible tone whereby the pitch or frequency of the tone varies depending on the type of scattering material, item or object. Additionally or alternatively, the operator obtains a visual scan image on a screen by scanning the beam around a suspect area or anomaly.

Description:
CROSS-REFERENCE 
       [0001]    The present application relies on U.S. Patent Provisional Application No. 62/136,299, entitled “Handheld Portable Backscatter Inspection System” and filed on Mar. 20, 2015, for priority. 
         [0002]    The present application also relies on U.S. Patent Provisional Application No. 62/136,305, entitled “Handheld Portable Backscatter Inspection System” and filed on Mar. 20, 2015, for priority. 
         [0003]    The present application also relies on U.S. Patent Provisional Application No. 62/136,315, entitled “Handheld Portable Backscatter Inspection System” and filed on Mar. 20, 2015, for priority. 
         [0004]    The present application also relies on U.S. Patent Provisional Application No. 62/136,322, entitled “Handheld Portable Backscatter Inspection System” and filed on Mar. 20, 2015, for priority. 
         [0005]    The present application also relies on U.S. Patent Provisional Application No. 62/136,362, entitled “Handheld Portable Backscatter Inspection System” and filed on Mar. 20, 2015, for priority. 
         [0006]    All of the above-mentioned applications are herein incorporated by reference in their entirety. 
     
    
     FIELD 
       [0007]    The present specification generally relates to a portable backscatter scanning system, and in particular, relates to a system which can be carried by an operator by hand to sites of inspection, including confined locations, and subsequently used to scan for detection of concealed materials and objects. 
       BACKGROUND 
       [0008]    Materials, such as narcotics, explosives or currency, and objects, such as weapons or people, are concealed within or behind barriers with the intention that the materials or objects remain undetected by routine or targeted security checks. 
         [0009]    Today, scanning devices are well known which use a variety of sensing methods to detect concealed materials and objects. These scanning devices include transmission X-ray imaging systems, Compton scatter-based backscatter imaging systems, chemical sniffing trace detection equipment, thermal imaging camera systems and so on. Such scanning devices may be used alone or in combination to provide a comprehensive level of security. However, such devices tend either to be large and expensive (e.g. transmission X-ray imaging systems) or insensitive to carefully hidden materials (e.g. trace detection equipment and camera systems) which means that their utility is restricted to certain high throughput situations such as sea ports and land borders, airport checkpoints and so on. 
         [0010]    Therefore, what is needed is a compact, light-weight, portable and hand-held system or device that can be maneuvered to reach relatively inaccessible locations and scan behind concealing barriers that are otherwise opaque against chemical and optical probes. Such a system or device should be able to provide immediate feedback if a suspicious material, object or anomaly is detected and should allow an operator to obtain information about the concealed material or object, for threat resolution, without the need to breach the concealing barrier. 
       SUMMARY 
       [0011]    In some embodiments, the present specification discloses a method for scanning an object by projecting a shaped X-ray beam from a hand-held imaging device, where the device includes a housing enclosing an X-ray tube that emits the shaped X-ray beam, a plurality of detectors for generating scan data corresponding to a plurality of detected X-ray beams scattered from the object, a processor in communication with a gyroscope and an accelerometer, and an acquisition system in communication with a speaker, a display, the processor and the plurality of detectors. In some embodiments, the method includes using the processor for calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object; using the processor for calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and using the processor to generate an image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0012]    In some embodiments, the shaped X-ray beam is a pencil beam. 
         [0013]    In some embodiments, the shaped X-ray beam is a cone beam. 
         [0014]    In some embodiments, the shaped X-ray beam is a fan beam. 
         [0015]    In some embodiments, the shaped X-ray beam is a single-axis rotating beam. 
         [0016]    In some embodiments, the shaped X-ray beam is a dual-axis rotating beam. 
         [0017]    In some embodiments, the hand-held imaging device is swept to scan the object using a coarse scanning pattern to identify at least one anomaly, with reference to the object, prior to calculating said plurality of active pixels, calculating said time duration and generating said image. Optionally, the anomaly is identified based on a change in audible tone generated by the speaker. Optionally, the processor and speaker are adapted to generate said audible tone such that a pitch or frequency of said audible tone varies in proportion to said scan data. 
         [0018]    Optionally, upon identification of said at least one anomaly, the hand-held imaging device is swept to scan the object using a fine scanning pattern for calculating said plurality of active pixels, calculating said time duration and generating said image. 
         [0019]    In some embodiments, the processor receives second data which is generated by the accelerometer and is indicative of a movement of the shaped X-ray beam being projected on the object. In some embodiments, the method includes based on said second data: using the processor for calculating a plurality of active pixels corresponding to a new location of interaction of the shaped X-ray beam on the object; using the processor for calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and using the processor for generating an updated image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0020]    In some embodiments, the new location is associated with an updated first data generated by the gyroscope, and wherein said updated first data is indicative of a new direction of the shaped X-ray beam being projected on the object. 
         [0021]    In some embodiments, the acquisition system sums said detected scan data over a sampling duration ranging between 0.01 ms and 100 ms. 
         [0022]    In some embodiments, the acquisition system sums said detected scan data over a sampling duration of 1 ms. 
         [0023]    In some embodiments, a voltage of the X-ray tube ranges between 30 kV and 100 kV. 
         [0024]    In some embodiments, a current of the X-ray tube ranges between 0.1 mA and 5 mA. 
         [0025]    In some embodiments, the location is associated with a first data generated by the gyroscope, and wherein said first data is indicative of a direction of the shaped X-ray beam being projected on the object. 
         [0026]    In some embodiments, the present specification discloses a system for a hand-held imaging device for scanning an object by projecting a shaped X-ray beam. In some embodiments, the system includes a housing having a central longitudinal axis and including: a plurality of detectors for generating scan data corresponding to a plurality of detected X-ray beams scattered from the object; a gyroscope; an accelerometer; an acquisition system in communication with a display and said plurality of detectors; and a processor in communication with said gyroscope, said accelerometer and said acquisition system. In some embodiments, said processor is configured for: calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object; calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and generating an image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0027]    In some embodiments, the shaped X-ray beam is a pencil beam. 
         [0028]    In some embodiments, the shaped X-ray beam is a cone beam. 
         [0029]    In some embodiments, the shaped X-ray beam is a fan beam. 
         [0030]    In some embodiments, the shaped X-ray beam is a single-axis rotating beam. 
         [0031]    In some embodiments, the shaped X-ray beam is a dual-axis rotating beam. 
         [0032]    In some embodiments, the housing has an upper surface, a base opposite and parallel to said upper surface, a front surface, a rear surface opposite and parallel to said front surface, a first side and a second side opposite and parallel to said first side, and wherein said upper surface has at least one handle. Optionally, the housing is configured as a first cuboid, bearing said front surface, which tapers along the central longitudinal axis into a trapezoidal prism culminating in said rear surface. 
         [0033]    Optionally, the shaped X-ray beam emerges through an opening at a center of said front surface in a direction substantially perpendicular to said front surface. Optionally, the plurality of detectors are positioned adjacent to and behind said front surface surrounding said opening at the center of said front surface. 
         [0034]    In some embodiments, the system includes a speaker, wherein said processor and speaker are adapted to generate an audible tone such that a pitch or frequency of said audible tone varies in proportion to said scan data. 
         [0035]    Optionally, the housing further comprises a plurality of vanes for collimating a plurality of X-ray beams scattered from the object. Optionally, said plurality of vanes are arranged in planes that are substantially parallel to each other. Optionally, said plurality of vanes are arranged in planes that are substantially parallel to each other and in a direction substantially perpendicular to an orientation of a plane of a fan beam. Optionally, said plurality of vanes is arranged in planes in a substantially diverging orientation with respect to each other. Optionally, said plurality of vanes is arranged in planes in a substantially converging orientation with respect to each other. 
         [0036]    Optionally, the housing further comprises a grid of a plurality of collimator elements for collimating a plurality of X-ray beams scattered from the object. Still optionally, said grid comprises first and second sets of a plurality of combs, each of said plurality of combs having teeth, wherein the teeth of said first set of combs in a first direction interlock with the teeth of said second set of combs in a second direction, and wherein said second direction is substantially orthogonal to said first direction. Optionally, said teeth are arranged in planar directions substantially parallel to an orientation of said shaped X-ray beam. Still optionally, said teeth are arranged in planar directions substantially parallel to each other. Optionally, said teeth are arranged in planar orientations that are substantially divergent with respect to each other. Optionally, said teeth are arranged in planar orientations that are substantially convergent with respect to each other. Optionally, each of said plurality of detectors maps to an area on the object, wherein said area is defined by a solid angle of a cone beam and an acceptance angle of each of said plurality of collimator elements. 
         [0037]    Optionally, the housing further comprises a first rotating collimator having a first transmission pattern and a second rotating collimator having a second transmission pattern, said first and second transmission patterns defining said shaped X-ray beam. Optionally, said first transmission pattern defines a radial position of a pencil beam while said second transmission pattern defines an azimuthal angle of said pencil beam. Optionally, said first and second collimators rotate in lock step with each other, and wherein said first collimator rotates at a first speed while said second collimator rotates at a second speed. Optionally, said second speed is greater than said first speed. Optionally, said first and second collimators are substantially circular disks having differing radii. Optionally, said first and second collimators are substantially circular disks having equal radii. Optionally, said first transmission pattern is a slit extending in a spirally curved configuration from a point proximate to a center point of said first collimator to a point proximate to a circumference of said first collimator, and wherein said second transmission pattern is a slit extending radially from a point proximate to a center of said second collimator to a point proximate to a circumference of said second collimator. 
         [0038]    Optionally, said housing further comprises a rotating collimator having a transmission pattern defining the shaped X-ray beam, the rotating collimator supported and partially surrounded by an oscillating shaped cradle. Optionally, said collimator rotates at a speed ranging between 100 to 5000 RPM. Optionally, said collimator rotates at a speed of 2000 RPM. Optionally, said rotating collimator causes said shaped X-ray beam to sweep a trajectory in a substantially vertical plane such that a focal spot of said shaped X-ray beam is in a plane of said rotating collimator and on a central longitudinal axis of said housing, and wherein said oscillating shaped cradle causes said shaped X-ray beam to sweep left to right, repeatedly, over said substantially vertical plane. Optionally, said collimator is a substantially circular disk having a first radius while said shaped cradle is substantially semi-circular having a second radius, and wherein said second radius is greater than said first radius. Optionally, said collimator is a substantially circular disk having a radius while said shaped cradle is substantially ‘U’ or ‘C’ shaped. Optionally, said transmission pattern is an opening at a point between a center and a circumference of said collimator, and wherein said rotating and oscillating movements together cause said shaped X-ray beam to move in a raster pattern over a two dimensional area of the object. 
         [0039]    In some embodiments, the present specification is directed toward a method of scanning an object by projecting a shaped X-ray beam from a hand-held imaging device. In some embodiments, the device includes a housing enclosing an X-ray tube that emits the shaped X-ray beam, a plurality of detectors for generating scan data corresponding to a plurality of detected X-ray beams scattered from the object, a processor in communication with a gyroscope and an accelerometer, and an acquisition system in communication with a speaker, a display, said processor and said plurality of detectors. In some embodiments, the method includes receiving first data by the processor, wherein said first data is generated by the gyroscope and is indicative of a direction of the shaped X-ray beam being projected on the object; using the processor for calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object, wherein said location is associated with said first data; using the processor for calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and using the processor for generating an image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0040]    In some embodiments, the shaped X-ray beam is in the form of a pencil beam. 
         [0041]    In some embodiments, the hand-held imaging device is swept to scan the object using a coarse scanning pattern to identify at least one anomaly, with reference to the object, prior to receiving said first data, calculating said plurality of active pixels, calculating said time duration and generating said image. Optionally, the anomaly is identified based on a change in audible tone generated by the speaker. Still optionally, a pitch or frequency of said audible tone is proportional to said generated scan data. 
         [0042]    Optionally, upon identification of said at least one anomaly, the hand-held imaging device is swept to scan the object using a fine scanning pattern for receiving said first data, calculating said plurality of active pixels, calculating said time duration and generating said image. Optionally, the method further includes receiving second data by the processor, wherein said second data is generated by the accelerometer and is indicative of a movement of the shaped X-ray beam being projected on the object. In some embodiments, based on said second data, the method includes receiving updated first data by the processor indicative of a new direction of the shaped X-ray beam being projected on the object; using the processor for calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object, wherein said location is associated with said updated first data indicative of the new direction; using the processor for calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and using the processor for generating an updated image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0043]    In some embodiments, the acquisition system sums said detected scan data over a sampling duration ranging between 0.01 ms and 100 ms. 
         [0044]    In some embodiments, the acquisition system sums said detected scan data over a sampling duration of 1 ms. 
         [0045]    In some embodiments, a voltage of the X-ray tube ranges between 30 kV and 100 kV. 
         [0046]    In some embodiments, a current of the X-ray tube ranges between 0.1 mA and 5 mA. 
         [0047]    In some embodiments, the present specification is directed towards a system for a hand-held imaging device for scanning an object by projecting a shaped X-ray beam, where the device includes a housing having a central longitudinal axis. In some embodiments, the housing includes a plurality of detectors for generating scan data corresponding to a plurality of detected X-ray beams scattered from the object; a gyroscope; an accelerometer; an acquisition system in communication with a speaker, a display and said plurality of detectors; and a processor in communication with said gyroscope, said accelerometer and said acquisition system. In some embodiments, said processor is configured for receiving first data generated by the gyroscope and indicative of a direction of the shaped X-ray beam being projected on the object; calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object, wherein said location is associated with said first data; calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and generating an image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0048]    In some embodiments, the shaped X-ray beam is in the form of a pencil beam. 
         [0049]    In some embodiments, the housing has an upper surface, a base opposite and parallel to said upper surface, a front surface, a rear surface opposite and parallel to said front surface, a first side and a second side opposite and parallel to said first side, and wherein said upper surface has at least one handle. Optionally, the housing is configured as a first cuboid, bearing said front surface, which tapers along the central longitudinal axis into a second cuboid culminating in said rear surface. Optionally, the shaped X-ray beam emerges through an opening at a center of said front surface in a direction substantially perpendicular to said front surface. Optionally, the plurality of detectors are positioned adjacent to and behind said front surface surrounding said opening at the center of said front surface. Optionally, there are four sets of detectors. 
         [0050]    In some embodiments, the present specification is directed towards a method of scanning an object by projecting a shaped X-ray beam from a hand-held imaging device. In some embodiments, the device includes a housing enclosing an X-ray tube that emits the shaped X-ray beam, a plurality of vanes for collimating a plurality of X-ray beams scattered from the object, a plurality of detectors for generating scan data corresponding to the plurality of collimated X-ray beams detected by said plurality of detectors, a processor in communication with a gyroscope and an accelerometer, and an acquisition system in communication with a speaker, a display, said processor and said plurality of detectors. In some embodiments, the method includes using the processor for calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object; using the processor for calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and using the processor for generating an image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0051]    In some embodiments, the shaped X-ray beam is in the form of a fan beam. 
         [0052]    In some embodiments, the hand-held imaging device is swept to scan the object using a coarse scanning pattern to identify at least one anomaly, with reference to the object, prior to calculating said plurality of active pixels, calculating said time duration and generating said image. Optionally, the one anomaly is identified based on a change in audible tone generated by the speaker. Still optionally, a pitch or frequency of said audible tone is proportional to said generated scan data. Optionally, upon identification of said at least one anomaly, the hand-held imaging device is swept to scan the object using a fine scanning pattern for calculating said plurality of active pixels, calculating said time duration and generating said image. Still optionally, the method further includes receiving second data by the processor, wherein said second data is generated by the accelerometer and is indicative of a movement of the shaped X-ray beam being projected on the object and wherein based on said second data using the processor for calculating a plurality of active pixels corresponding to a new location of interaction of the shaped X-ray beam on the object; using the processor for calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and using the processor for generating an updated image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. Optionally, the new location is associated with an updated first data generated by the gyroscope, and wherein said updated first data is indicative of a new direction of the shaped X-ray beam being projected on the object. 
         [0053]    In some embodiments, the acquisition system sums said detected scan data over a sampling duration of 1 ms. 
         [0054]    In some embodiments, a voltage of the X-ray tube ranges between 30 kV and 100 kV. 
         [0055]    In some embodiments, a current of the X-ray tube ranges between 0.1 mA and 5 mA. 
         [0056]    In some embodiments, the location is associated with a first data generated by the gyroscope, and wherein said first data is indicative of a direction of the shaped X-ray beam being projected on the object. 
         [0057]    In some embodiments, the present specification discloses a system for a hand-held imaging device for scanning an object by projecting a shaped X-ray beam, where the device includes a housing having a central longitudinal axis. In some embodiments, the housing includes a plurality of vanes for collimating a plurality of X-ray beams scattered from the object; 
         [0058]    a plurality of detectors for generating scan data corresponding to the plurality of collimated X-ray beams detected by said plurality of detectors; a gyroscope; an accelerometer; an acquisition system in communication with a speaker, a display and said plurality of detectors; and a processor in communication with said gyroscope, said accelerometer and said acquisition system. In some embodiments, the processor is configured for calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object; calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and generating an image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0059]    In some embodiments, the shaped X-ray beam is in the form of a fan beam. 
         [0060]    In some embodiments, the hand-held imaging device is swept to scan the object using a coarse scanning pattern to identify at least one anomaly, with reference to the object, prior to said processor calculating said plurality of active pixels, calculating said time duration and generating said image. Optionally, the anomaly is identified based on a change in audible tone generated by the speaker. Still optionally, a pitch or frequency of said audible tone is proportional to said generated scan data. Optionally, upon identification of said at least one anomaly, the hand-held imaging device is swept to scan the object using a fine scanning pattern for calculating said plurality of active pixels, calculating said time duration and generating said image. 
         [0061]    In some embodiments, the housing has an upper surface, a base opposite and parallel to said upper surface, a front surface, a rear surface opposite and parallel to said front surface, a first side and a second side opposite and parallel to said first side, and wherein said upper surface has at least one handle. Optionally, the housing is configured as a first cuboid, bearing said front surface, which tapers along the central longitudinal axis into a second cuboid culminating in said rear surface. Optionally, the shaped X-ray beam emerges through an opening at a center of said front surface in a direction substantially perpendicular to said front surface. Optionally, the plurality of detectors are positioned adjacent to and behind said front surface surrounding said opening at the center of said front surface, and wherein said plurality of vanes are positioned in front of said plurality of detectors and behind said front surface. 
         [0062]    In some embodiments, the plurality of detectors include four sets of detectors. 
         [0063]    In some embodiments, planes of said plurality of vanes are arranged in a direction substantially perpendicular to an orientation of a plane of said fan beam. Optionally, planes of said plurality of vanes are arranged one of substantially parallel to each other, in a substantially diverging orientation with respect to each other, and in a substantially converging orientation with respect to each other. 
         [0064]    In some embodiments, the present specification discloses a method for scanning an object by projecting a shaped X-ray beam from a hand-held imaging device. In some embodiments, the device includes a housing enclosing an X-ray tube that emits the shaped X-ray beam, a grid of a plurality of collimator elements for collimating a plurality of X-ray beams scattered from the object, a plurality of detectors for generating scan data corresponding to the plurality of collimated X-ray beams detected by said plurality of detectors, a processor in communication with a gyroscope and an accelerometer, and an acquisition system in communication with a speaker, a display, said processor and said plurality of detectors. In some embodiments, the method includes using the processor for calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object; using the processor for calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and using the processor for generating an image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0065]    In some embodiments, the shaped X-ray beam is in the form of a cone beam. 
         [0066]    In some embodiments, the hand-held imaging device is swept to scan the object using a coarse scanning pattern to identify at least one anomaly, with reference to the object, prior to calculating said plurality of active pixels, calculating said time duration and generating said image. Optionally, the anomaly is identified based on a change in audible tone generated by the speaker. Still optionally, a pitch or frequency of said audible tone is proportional to said generated scan data. Optionally, upon identification of said at least one anomaly, the hand-held imaging device is swept to scan the object using a fine scanning pattern for calculating said plurality of active pixels, calculating said time duration and generating said image. Still optionally, the method further includes receiving second data by the processor, wherein said second data is generated by the accelerometer and is indicative of a movement of the shaped X-ray beam being projected on the object and wherein based on said second data the method includes using the processor for calculating a plurality of active pixels corresponding to a new location of interaction of the shaped X-ray beam on the object; using the processor for calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and using the processor for generating an updated image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. Still optionally, the new location is associated with an updated first data generated by the gyroscope, and wherein said updated first data is indicative of a new direction of the shaped X-ray beam being projected on the object. 
         [0067]    In some embodiments, the acquisition system sums said detected scan data over a sampling duration ranging between 0.01 ms and 100 ms. 
         [0068]    In some embodiments, the acquisition system sums said detected scan data over a sampling duration of 1 ms. 
         [0069]    In some embodiments, a voltage of the X-ray tube ranges between 30 kV and 100 kV. 
         [0070]    In some embodiments, a current of the X-ray tube ranges between 0.1 mA and 5 mA. 
         [0071]    In some embodiments, the location is associated with a first data generated by the gyroscope, and wherein said first data is indicative of a direction of the shaped X-ray beam being projected on the object. 
         [0072]    In some embodiments, the present specification discloses a system for a hand-held imaging device for scanning an object by projecting a shaped X-ray beam, where the device includes a housing having a central longitudinal axis and including a grid of a plurality of collimator elements for collimating a plurality of X-ray beams scattered from the object; a plurality of detectors for generating scan data corresponding to the plurality of collimated X-ray beams detected by said plurality of detectors; a gyroscope; an accelerometer; an acquisition system in communication with a speaker, a display and said plurality of detectors; and a processor in communication with said gyroscope, said accelerometer and said acquisition system. In some embodiments, the processor is configured for calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object; calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and generating an image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0073]    In some embodiments, the shaped X-ray beam is in the form of a cone beam. 
         [0074]    In some embodiments, the housing has an upper surface, a base opposite and parallel to said upper surface, a front surface, a rear surface opposite and parallel to said front surface, a first side and a second side opposite and parallel to said first side, and wherein said upper surface has at least one handle. Optionally, the housing is configured as a first cuboid, bearing said front surface, which tapers along the central longitudinal axis into a second cuboid culminating in said rear surface. Optionally, the shaped X-ray beam emerges through an opening at a center of said front surface in a direction substantially perpendicular to said front surface. Optionally, the plurality of detectors are positioned adjacent to and behind said front surface surrounding said opening at the center of said front surface, and wherein said grid is positioned behind said front surface and in front of said plurality of detectors such that at least one of said plurality of detectors is present per said collimator element. 
         [0075]    In some embodiments, the grid comprises first and second sets of a plurality of combs, each of said plurality of combs having teeth, wherein the teeth of said first set of combs in a first direction interlock with the teeth of said second set of combs in a second direction, and wherein said second direction is substantially orthogonal to said first direction. Optionally, planes of said teeth are arranged in one of a direction substantially parallel to an orientation of said shaped X-ray beam, substantially parallel to each other, substantially diverging orientation with respect to each other, and substantially converging orientation with respect to each other. 
         [0076]    In some embodiments, each of said plurality of detectors maps to an area on the object, wherein said area is defined by a solid angle of said cone beam and an acceptance angle of each of said plurality of collimator elements. 
         [0077]    In some embodiments, the present specification discloses a method for scanning an object by projecting a shaped X-ray beam from a hand-held imaging device. In some embodiments, the device includes a housing enclosing an X-ray tube that emits the shaped X-ray beam, a first rotating collimator having a first transmission pattern and a second rotating collimator having a second transmission pattern, said first and second transmission patterns defining said shaped X-ray beam, a plurality of detectors for generating scan data corresponding to a plurality of detected X-ray beams, a processor in communication with a gyroscope and an accelerometer, and an acquisition system in communication with a speaker, a display, said processor and said plurality of detectors. In some embodiments, the method includes using the processor for calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object; using the processor for calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and using the processor for generating an image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0078]    In some embodiments, the shaped X-ray beam is in the form of a pencil beam. Optionally, the first transmission pattern defines a radial position of said pencil beam while said second transmission pattern defines an azimuthal angle of said pencil beam. 
         [0079]    In some embodiments, the hand-held imaging device is swept to scan the object using a coarse scanning pattern to identify at least one anomaly, with reference to the object, prior to calculating said plurality of active pixels, calculating said time duration and generating said image. Optionally, the anomaly is identified based on a change in audible tone generated by the speaker. Still optionally, a pitch or frequency of said audible tone is proportional to said generated scan data. Optionally, upon identification of said at least one anomaly, the hand-held imaging device is swept to scan the object using a fine scanning pattern for calculating said plurality of active pixels, calculating said time duration and generating said image. 
         [0080]    In some embodiments, the method further includes receiving second data by the processor, wherein said second data is generated by the accelerometer and is indicative of a movement of the shaped X-ray beam being projected on the object and wherein based on said second data the method includes using the processor for calculating a plurality of active pixels corresponding to a new location of interaction of the shaped X-ray beam on the object; using the processor for calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and using the processor for generating an updated image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. Optionally, the new location is associated with an updated first data generated by the gyroscope, and wherein said updated first data is indicative of a new direction of the shaped X-ray beam being projected on the object. 
         [0081]    In some embodiments, the acquisition system sums said detected scan data over a sampling duration ranging between 0.01 ms and 100 ms. 
         [0082]    In some embodiments, the acquisition system sums said detected scan data over a sampling duration of 1 ms. 
         [0083]    In some embodiments, a voltage of the X-ray tube ranges between 30 kV and 100 kV. 
         [0084]    In some embodiments, a current of the X-ray tube ranges between 0.1 mA and 5 mA. 
         [0085]    In some embodiments, the location is associated with a first data generated by the gyroscope, and wherein said first data is indicative of a direction of the shaped X-ray beam being projected on the object. 
         [0086]    In some embodiments, the present specification discloses a system for a hand-held imaging device for scanning an object by projecting a shaped X-ray beam, where the device includes a housing having a central longitudinal axis. In some embodiments, the housing includes a first rotating collimator having a first transmission pattern and a second rotating collimator having a second transmission pattern, said first and second transmission patterns defining said shaped X-ray beam; a plurality of detectors for generating scan data corresponding to a plurality of detected X-ray beams; a gyroscope; an accelerometer; an acquisition system in communication with a speaker, a display and said plurality of detectors; and a processor in communication with said gyroscope, said accelerometer and said acquisition system. In some embodiments, the processor is configured for calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object; calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and generating an image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0087]    In some embodiments, the shaped X-ray beam is in the form of a pencil beam. Optionally, the first transmission pattern defines a radial position of said pencil beam while said second transmission pattern defines an azimuthal angle of said pencil beam. 
         [0088]    In some embodiments, the first and second collimators rotate in lock step with each other, and wherein said first collimator rotates at a first speed while said second collimator rotates at a second speed. Optionally, the second speed is greater than said first speed. 
         [0089]    In some embodiments, the first and second collimators are substantially circular disks having differing radii. 
         [0090]    In some embodiments, the first and second collimators are substantially circular disks having same radii. 
         [0091]    In some embodiments, the first transmission pattern is a slit extending in a spirally curved configuration from a point proximate a center of said first collimator to a point proximate a circumference of said first collimator, and wherein said second transmission pattern is a slit extending radially from a point proximate a center of said second collimator to a point proximate a circumference of said second collimator. 
         [0092]    In some embodiments, the housing has an upper surface, a base opposite and parallel to said upper surface, a front surface, a rear surface opposite and parallel to said front surface, a first side and a second side opposite and parallel to said first side, and wherein said upper surface has at least one handle. Optionally, the housing is configured as a first cuboid, bearing said front surface, which tapers along the central longitudinal axis into a second cuboid culminating in said rear surface. Optionally, the shaped X-ray beam emerges through an opening at a center of said front surface in a direction substantially perpendicular to said front surface. Optionally, the plurality of detectors are positioned adjacent to and behind said front surface surrounding said opening at the center of said front surface. Optionally, the first collimator is arranged coaxially in front of said second collimator along a central longitudinal axis of said housing, and wherein said first and second collimators are positioned between said opening of said front surface and an opening of said X-ray tube. 
         [0093]    In some embodiments, the present specification discloses a method for scanning an object by projecting a shaped X-ray beam from a hand-held imaging device. In some embodiments, the device includes a housing enclosing an X-ray tube that emits the shaped X-ray beam, a rotating collimator having a transmission pattern defining said shaped X-ray beam, said rotating collimator supported and partially surrounded by an oscillating shaped cradle, a plurality of detectors for generating scan data corresponding to a plurality of detected X-ray beams, a processor in communication with a gyroscope and an accelerometer, and an acquisition system in communication with a speaker, a display, said processor and said plurality of detectors. In some embodiments, the method includes using the processor for calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object; using the processor for calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and using the processor for generating an image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0094]    In some embodiments, the shaped X-ray beam is in the form of a pencil beam. 
         [0095]    In some embodiments, the hand-held imaging device is swept to scan the object using a coarse scanning pattern to identify at least one anomaly, with reference to the object, prior to calculating said plurality of active pixels, calculating said time duration and generating said image. Optionally, the anomaly is identified based on a change in audible tone generated by the speaker. Still optionally, a pitch or frequency of said audible tone is proportional to said generated scan data. Optionally, upon identification of said at least one anomaly, the hand-held imaging device is swept to scan the object using a fine scanning pattern for calculating said plurality of active pixels, calculating said time duration and generating said image. 
         [0096]    In some embodiments, the method further includes receiving second data by the processor, wherein said second data is generated by the accelerometer and is indicative of a movement of the shaped X-ray beam being projected on the object and wherein based on said second data the method includes using the processor for calculating a plurality of active pixels corresponding to a new location of interaction of the shaped X-ray beam on the object; using the processor for calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and using the processor for generating an updated image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. Optionally, the new location is associated with an updated first data generated by the gyroscope, and wherein said updated first data is indicative of a new direction of the shaped X-ray beam being projected on the object. 
         [0097]    In some embodiments, the acquisition system sums said detected scan data over a sampling duration ranging between 0.01 ms and 100 ms. 
         [0098]    In some embodiments, the acquisition system sums said detected scan data over a sampling duration of 1 ms. 
         [0099]    In some embodiments, a voltage of the X-ray tube ranges between 30 kV and 100 kV. 
         [0100]    In some embodiments, a current of the X-ray tube ranges between 0.1 mA and 5 mA. 
         [0101]    In some embodiments, the location is associated with a first data generated by the gyroscope, and wherein said first data is indicative of a direction of the shaped X-ray beam being projected on the object. 
         [0102]    In some embodiments, the present specification discloses a system for a hand-held imaging device for scanning an object by projecting a shaped X-ray beam, where the device includes a housing having a central longitudinal axis. In some embodiments, the housing includes a rotating collimator having a transmission pattern defining said shaped X-ray beam, said rotating collimator supported and partially surrounded by an oscillating shaped cradle; a plurality of detectors for generating scan data corresponding to a plurality of detected X-ray beams; a gyroscope; an accelerometer; an acquisition system in communication with a speaker, a display and said plurality of detectors; and a processor in communication with said gyroscope, said accelerometer and said acquisition system. In some embodiments, the processor is configured for calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object; calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and generating an image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0103]    In some embodiments, the shaped X-ray beam is in the form of a pencil beam. 
         [0104]    In some embodiments, the collimator rotates at a speed ranging between 100 to 5000 RPM. In some embodiments, the collimator rotates at a speed of 2000 RPM. 
         [0105]    In some embodiments, the rotating collimator causes said shaped X-ray beam to sweep a trajectory in a substantially vertical plane such that a focal spot of said shaped X-ray beam is in a plane of said rotating collimator and on a central longitudinal axis of said housing, and wherein said oscillating shaped cradle causes said shaped X-ray beam to sweep left to right, repeatedly, over said substantially vertical plane. 
         [0106]    In some embodiments, the collimator is a substantially circular disk having a first radius while said shaped cradle is substantially semi-circular having a second radius, and wherein said second radius is greater than said first radius. 
         [0107]    In some embodiments, the collimator is a substantially circular disk having a radius while said shaped cradle is substantially ‘U’ or ‘C’ shaped. 
         [0108]    In some embodiments, the transmission pattern is an opening at a point between a center and a circumference of said collimator, and wherein said rotating and said oscillating movements together cause said shaped X-ray beam to move in a raster pattern over a two dimensional area of the object. 
         [0109]    In some embodiments, the housing has an upper surface, a base opposite and parallel to said upper surface, a front surface, a rear surface opposite and parallel to said front surface, a first side and a second side opposite and parallel to said first side, and wherein said upper surface has at least one handle. Optionally, the housing is configured as a first cuboid, bearing said front surface, which tapers along the central longitudinal axis into a second cuboid culminating in said rear surface. Optionally, the shaped X-ray beam emerges through an opening at a center of said front surface in a direction substantially perpendicular to said front surface. Still optionally, the plurality of detectors are positioned adjacent to and behind said front surface surrounding said opening at the center of said front surface. Still optionally, respective centers of said collimator and said shaped cradle are substantially coaxial with a central longitudinal axis of said housing, and wherein said collimator and said shaped cradle are positioned between said opening of said front surface and an opening of said X-ray tube. 
         [0110]    The aforementioned and other embodiments of the present specification shall be described in greater depth in the drawings and detailed description provided below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0111]    These and other features and advantages of the present specification will be appreciated, as they become better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
           [0112]      FIG. 1A  is a perspective view of a hand-held portable scanning device, in accordance with an embodiment of the present specification; 
           [0113]      FIG. 1B  is a vertical cross-sectional view of the hand-held portable scanning device of  FIG. 1A ; 
           [0114]      FIG. 1C  illustrates the hand-held portable scanning device of the present specification projecting an X-ray beam over an object under inspection, in an embodiment; 
           [0115]      FIG. 2A  is a perspective view of a hand-held portable scanning device, in accordance with another embodiment of the present specification; 
           [0116]      FIG. 2B  is a vertical cross-sectional view of the hand-held portable scanning device of  FIG. 2A ; 
           [0117]      FIG. 2C  illustrates the hand-held portable scanning device of the present specification projecting an X-ray beam over an object under inspection, in an embodiment; 
           [0118]      FIG. 3A  is a perspective view of a hand-held portable scanning device, in accordance with another embodiment of the present specification; 
           [0119]      FIG. 3B  is a vertical cross-sectional view of the hand-held portable scanning device of  FIG. 3A ; 
           [0120]      FIG. 3C  illustrates the hand-held portable scanning device of the present specification projecting an X-ray beam over an object under inspection, in an embodiment; 
           [0121]      FIG. 3D  illustrates a collimator grid fabricated by assembling or arranging a plurality of combs having a plurality of teeth, in accordance with an embodiment; 
           [0122]      FIG. 3E  illustrates a sensing module formed by coupling an array of detectors to a card with a single signal control and readout cable, in accordance with an embodiment; 
           [0123]      FIG. 3F  illustrates a collimator grid coupled to a sensing module, in accordance with an embodiment; 
           [0124]      FIG. 4A  is a perspective view of a hand-held portable scanning device, in accordance with yet another embodiment of the present specification; 
           [0125]      FIG. 4B  is a vertical cross-sectional view of the hand-held portable scanning device of  FIG. 4A ; 
           [0126]      FIG. 4C  illustrates first and second collimator disks having first and second transmission patterns, respectively, in accordance with an embodiment; 
           [0127]      FIG. 4D  illustrates various exemplary positions of a moving or sweeping pencil X-ray beam defined by first and second transmission patterns of the first and second collimator disks shown in  FIG. 4C ; 
           [0128]      FIG. 4E  illustrates a motor driven assembly of first and second gears which, in turn, rotate the first and second collimator disks, shown in  FIG. 4C ; 
           [0129]      FIG. 4F  illustrates two sets of free running drive wheels or gears used to support the first and second collimator disks, shown in  FIG. 4C ; 
           [0130]      FIG. 4G  illustrates the hand-held portable scanning device of the present specification projecting an X-ray beam over an object under inspection, in an embodiment; 
           [0131]      FIG. 5A  is a perspective view of a hand-held portable scanning device, in accordance with still another embodiment of the present specification; 
           [0132]      FIG. 5B  is a vertical cross-sectional view of the hand-held portable scanning device of  FIG. 5A ; 
           [0133]      FIG. 5C  is a front view of a motor driven collimator assembly comprising a collimator and support or cradle, in accordance with an embodiment; 
           [0134]      FIG. 5D  is a side view of the motor driven collimator assembly of  FIG. 1C ; 
           [0135]      FIG. 5E  is a substantially spherical head portion of an X-ray tube positioned within the collimator assembly, in accordance with an embodiment; 
           [0136]      FIG. 5F  illustrates the hand-held portable scanning device of the present specification projecting an X-ray beam over an object under inspection, in an embodiment; 
           [0137]      FIG. 6A  is a block diagram illustrating a data acquisition system and a processing element in data communication with a plurality of detectors, a collimator motor, an azimuth motor, and a rotary encoder, in an embodiment of the present specification; 
           [0138]      FIG. 6B  is a block diagram illustrating a data acquisition system and a processing element in data communication with a plurality of detectors, a gyroscope and an accelerometer, in an embodiment of the present specification; and, 
           [0139]      FIG. 7  is a flow chart illustrating exemplary steps of a method of scanning an object using the hand-held portable device of the present specification. 
       
    
    
     DETAILED DESCRIPTION 
       [0140]    In some embodiments, the present specification discloses a system for scanning an object by projecting a shaped X-ray beam from a hand-held imaging device, where the device includes a housing enclosing an X-ray tube that emits the shaped X-ray beam, a plurality of detectors for generating scan data, a processor in communication with a gyroscope and an accelerometer, and an acquisition system. In some embodiments, the method includes using the processor for calculating a plurality of active pixels corresponding to a location of interaction of the shaped X-ray beam on the object; using the processor for calculating a time duration, at each of said plurality of active pixels, for which the shaped X-ray beam is present over each of said plurality of active pixels; and using the processor for generating an image, on said display, of the object after correcting the scan data, at each of said plurality of active pixels, using said time duration. 
         [0141]    In some embodiments, the shaped X-ray beam is a pencil beam. 
         [0142]    In some embodiments, the shaped X-ray beam is a cone beam. 
         [0143]    In some embodiments, the shaped X-ray beam is a fan beam. 
         [0144]    In some embodiments, the shaped X-ray beam is a single-axis rotating beam. 
         [0145]    In some embodiments, the shaped X-ray beam is a dual-axis rotating beam. 
         [0146]    The present specification is directed towards multiple embodiments. The following disclosure is provided in order to enable a person having ordinary skill in the art to practice the invention. Language used in this specification should not be interpreted as a general disavowal of any one specific embodiment or used to limit the claims beyond the meaning of the terms used therein. The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Also, the terminology and phraseology used is for the purpose of describing exemplary embodiments and should not be considered limiting. Thus, the present invention is to be accorded the widest scope encompassing numerous alternatives, modifications and equivalents consistent with the principles and features disclosed. For purpose of clarity, details relating to technical material that is known in the technical fields related to the invention have not been described in detail so as not to unnecessarily obscure the present invention. In the description and claims of the application, each of the words “comprise” “include” and “have”, and forms thereof, are not necessarily limited to members in a list with which the words may be associated. 
         [0147]    Pencil Beam 
         [0148]      FIG. 1A  illustrates an embodiment of a hand-held portable X-ray based scanning system  100 , also referred to as an imaging system or device, for use in screening objects such as, but not limited to, baggage, containers/boxes, and other similar items for threat materials, items or people concealed therein. The system  100  is configured, in one embodiment, in the form of an enclosure or housing  105  having an upper surface  110 , a base (not visible in  FIG. 1A , but opposite, and substantially parallel to, the upper surface  110 ), a front surface  114 , a rear surface (not visible in  FIG. 1A , but opposite, and parallel to, the front surface  114 ), a first side  118 , and a second side (not visible in  FIG. 1A , but opposite, and parallel to, the first side  118 ). In accordance with one embodiment, the size and weight of system  100  is optimized for enabling an operator to conveniently hold and maneuver the housing  105  while scanning an object under inspection. In one embodiment, housing  105  is in the form of a first cuboid  125  (bearing the front surface  114 ) that tapers, along a central longitudinal axis  130 , into a second cuboid  135  culminating in the rear surface. In accordance with an embodiment, a height ‘H’ of the first cuboid  125  is greater than a height ‘h’ of the second cuboid  135 . It should, however, be appreciated that the shape of the housing  105  can be cylindrical, conical, pyramidal or any other suitable shape in various embodiments. Specifically, in one embodiment, housing  105  is in the form of a first cuboid  125  that attaches, at a back face and along a central longitudinal axis  130 , to a first trapezoidal prism  118  that tapers and, at its back face, attaches a second trapezoidal prism  135 . 
         [0149]    At least one handle  112  is provided on, for example, the upper surface  110  to allow the operator to hold the housing  105  conveniently in one or both hands and manipulate the device  100  to point the front surface  114  towards and at different regions on the object under inspection. In alternate embodiments one or more handles are provided on one or more areas or regions such as the upper surface  110 , the base, the first side  118  and/or the second side so that single-handed or two-handed operation of device  100  is facilitated, depending on what is easiest for the operator. 
         [0150]    Conventionally, X-rays are generated using a thermionic source of electrons, such as a hot tungsten wire in vacuum. The thermionic electrons are then accelerated in an electric field towards an anode or target at a high electrical potential relative to the electron source. Typically the anode is made from a refractory metal of high atomic number, such as tungsten or molybdenum. When electrons hit the anode at high potential, X-rays are created as the electrons lose energy in the anode material. Typically it is through the photoelectric and Bremsstrahlung interactions by which the electrons lose their energy and so create X-rays. The net result is a broad spectrum of X-ray energies, from close to zero up to the maximum energy of the accelerated electrons. 
         [0151]    The principles described above are applicable throughout each of the embodiments described in the present specification and will not be repeated with respect to each embodiment. 
         [0152]    Referring now to  FIGS. 1A and 1B , the housing  105  comprises an X-ray tube  140  whose anode  141 , also referred to as a target, emits a spatially localized X-ray beam  145  through an opening  142 , also referred to as an aperture. At least one shield  143 , formed of an X-ray absorptive material, such as tungsten or uranium, surrounds and encloses anode  141  to absorb stray radiation emitted from anode  141 . Opening  142 , defined through shield  143 , is provided with a size and thickness which enables opening  142  to act as a collimator in forming or shaping and limiting the X-ray radiation, emitted from anode  141 , into a shaped beam of X-rays  145 . In one embodiment, X-ray beam  145  is shaped into a pencil beam. 
         [0153]    A cathode and heater filament assembly (enclosed within housing  105 ) is held at a substantial potential difference (using a chargeable battery also enclosed within the housing  105 ) with reference to anode  141  by a kilovolt power supply (wrapped around at least one tube shielding  143 , in one embodiment). This potential difference causes thermionic electrons freed by the heated cathode (heated using the heater filament) to be directed and drawn to anode  141  at sufficiently high velocity to result in the generation of X-ray beam  145 . 
         [0154]    In accordance with an embodiment, shaped X-ray beam  145  emerges through an opening  144  at the center of front surface  114  of housing  105 , in a direction substantially perpendicular to front surface  114 . At least one or a plurality of X-ray backscatter detectors  150 , also referred to as sensors, are positioned adjacent to and behind front surface  114  such that they surround the area or region of emergence of X-ray beam  145  at opening  144  and cover a substantial area of front surface  114  in order to maximize detected backscatter signal. An embodiment of the present specification comprises four sets of detectors  150 . In other embodiments, a different number of detectors  150  may be utilized. 
         [0155]    In accordance with an aspect, detectors  150  advantageously comprise high density inorganic scintillators (such as NaI, BGO, LYSO, CsI) coupled to a suitable optical readout such as a photomultiplier tube, an array of semiconductor photomultipliers or an array of photodiodes. Other detector types include inorganic scintillators (such as poly-vinyl toluene) coupled to photomultiplier tubes or room temperature semiconductor detectors (such as CdTe, CdZnTe, TlBr, HgI). As will be evident to one skilled in the art, many detector topologies are possible, such as, but not limited to, square segmented, circular segmented or annular, while the endeavor is to balance cost against complexity and overall detection efficiency. The detector surface adapted to received scattered X-ray radiation is positioned proximate the front surface  114  of housing  105 . 
         [0156]    Also, detectors  150  can be operated in a plurality of ways. For example, each detector can be operated in a pulse-counting, energy discriminating mode to build up an energy spectrum of the interacting X-rays, whereby these spectra are sampled over short scanning periods to build up a map of count rate and associated energy spectrum for each scatter source point location on the surface of the object under inspection. As an example, assume that the operator is scanning the beam at a rate of 0.2 m/second over the surface of the object and the projected X-ray beam width at the object is 10 mm. Therefore, in an embodiment, the update rate is equal to a movement of half the X-ray beam width (5 mm in this case) corresponding to a dwell time of (5 mm)/(200 mm/s)=25 ms. The energy distribution in the spectrum is analyzed to find those X-rays of higher energy which are more likely to have come from a greater depth in the object compared to those at lower energy which are more likely to have come from the surface of the object. It is also possible to separate out those photons whose energy is higher than the maximum emitted from the X-ray tube since these are either summed events (in which more than one scattered X-ray interacted in the detector at the same time) or are events due to naturally occurring background radiation. In either case, these are used to compensate for artifacts that would otherwise be present in the signal data. 
         [0157]    It should be noted that the maximum energy of the X-rays produced by X-ray tube  140  determines the ability of these X-rays to penetrate into the object under inspection—that is, the higher the maximum X-ray energy, the more penetration can be achieved. Similarly, the higher the energy of the scattered X-ray photon, the more likely it is to escape through the object under inspection back to an X-ray detector  150 . Therefore, in accordance with an aspect it is desirable to have high X-ray energy to maximize depth of inspection within the object. 
         [0158]    To improve signal quality, device  100  of the present specification maximizes the number of scattered X-rays that are detected within a given signal integration or sampling period. The number of scattered X-rays for a given type of object under inspection is dependent on the number of X-rays that are incident on the object under inspection directly from the X-ray source. In the case of a fixed tube voltage, it is the anode current that affects the size of the scattered X-ray signal—that is, the higher the anode current, the greater the scattered signal. Most detection systems, such as the detectors  150 , are operated close to the Gaussian point whereby the variance in the signal is equal to the mean value of the signal. For example, if the mean number of scattered X-rays reaching the detector in a certain counting period were 100, then the variance would be 100 and the standard deviation would be square root of 100 (=10). Signal-to-noise ratio (SNR) is defined as mean divided by standard deviation, therefore, SNR in this example would be 100/10=10. 
         [0159]    Therefore, in a preferred embodiment, device  100  has high X-ray tube voltage (to improve penetration performance) and high anode current (to improve signal-to-noise ratio in the scattered X-ray signal). However, such a combination of factors will result in a device which is likely to be heavy due to the physical size of the X-ray tube components (to provide suitable clearance and creepage distance in the high voltage components) and the associated radiation shielding that will be needed to collimate the primary shaped beam and to shield the operator and radiation detectors from stray radiation from the X-ray tube target. Therefore, in various embodiments the tube voltage of the X-ray tube  140  ranges between 30 kV and 100 kV with tube currents ranging between 0.1 mA and 5 mA. 
         [0160]    During operation, as shown in  FIG. 1C , shaped X-ray beam  145  interacts with an object  160  under inspection, to produce scattered X-rays  146 . As shown, object  160  conceals therein, an item, person or material  161 . Scattered X-rays  146  are detected by the detectors  150  to produce scan data signal whose intensity is related to the effective atomic number (Z) near to the surface of object  160 . 
         [0161]    Compton scattering describes the interaction of an X-ray photon with an electron that is generally thought of as being at rest. Here, the angle of the exit X-ray photon is related to the direction of the incoming X-ray photon according to the Compton scattering equation: 
         [0000]    
       
         
           
             
               
                 λ 
                 ′ 
               
               - 
               λ 
             
             = 
             
               
                 h 
                 
                   
                     m 
                     e 
                   
                    
                   c 
                 
               
                
               
                 ( 
                 
                   1 
                   - 
                   
                     cos 
                      
                     
                       ( 
                       θ 
                       ) 
                     
                   
                 
                 ) 
               
             
           
         
       
     
         [0000]    where λ=incident photon energy, λ′=exit photon energy, me=mass of the electron and θ=angle between incident and exit photon directions. Thus, the energy of the scattered X-ray is always less than the incident X-ray, the energy being dependent on both the scattering angle and the incident X-ray photon energy. 
         [0162]    The above principles related to Compton scattering described here are applicable throughout each of the embodiments described in the present specification and will not be repeated with respect to each embodiment. 
       Fan Beam 
       [0163]      FIG. 2A  illustrates another embodiment of a hand-held portable X-ray based scanning system  200 , also referred to as an imaging system or device, for use in screening objects such as, but not limited to, baggage, containers/boxes, and other items for threat materials, items or people concealed therein. In embodiments, components of system  200 , such as—a housing  205 , an upper surface  210 , a base, a handle  212 , a front surface  214 , a rear surface, a first side  218 , a second side, a first cuboid  225 , a central longitudinal axis  230 , and a second cuboid (or trapezoidal prism)  235 —are configured similar to corresponding components described above in context of  FIG. 1A . These components, and the associated variations, are not described herein as they have been described in detail above. 
         [0164]    Referring now to  FIGS. 2A and 2B , housing  205  comprises an X-ray tube  240  whose anode  241 , also referred to as a target, emits a spatially localized X-ray beam  245  through an opening  242 , also referred to as an aperture. A shield  243 , formed of an X-ray absorptive material, such as tungsten or uranium, surrounds anode  241  so as to absorb stray radiation emitted from anode  241 . Opening  242  is provided with a size and thickness which enables opening  242  to act as a collimator in forming or shaping and limiting the X-ray radiation, emitted from anode  241 , into a shaped beam of X-rays  245 . In one embodiment, X-ray beam  245  is fan shaped. 
         [0165]    A cathode and heater filament assembly (not shown) may be configured, similar to embodiments described in above relation to the pencil beam embodiment. Similarly, energy of the X-rays and signal quality can be maintained in a manner described above in context of the pencil beam embodiments. 
         [0166]    A plurality of collimator vanes, blades, fins or plates  255  are positioned in front of detectors  250  and behind front surface  214 , resulting in the formation of a plurality of collimation elements  256  between adjacent collimator vanes  255 . In one embodiment, the planes of the plurality of collimator vanes  255  are arranged or configured in a direction substantially perpendicular to the orientation of shaped X-ray beam  245  (that is, to the plane of fan beam  245 ) or substantially perpendicular to the front surface of the housing. In some embodiments, plurality of collimator vanes  255  are arranged in a parallel configuration, wherein planes of vanes  255  are substantially parallel to each other, such that a vertical dimension, such as height, of a vertical region is viewed through collimators  255  to be of the same size as the extent or height ‘H’ of front surface  214 . In some embodiments, collimator vanes  255  are alternatively arranged in a focused configuration, wherein the planes of vanes  255  together form a diverging or converging orientation, such that collimator vanes  255  view either a smaller or larger of the vertical dimension, such as height, of the vertical region than the extent or the height ‘H’ of front surface  214 . 
         [0167]    In various embodiments, detectors  250  are arranged behind collimator vanes  255  such that at least one of detectors  250  is present per collimation element  256  in order to create a one-dimensional linear image. 
         [0168]    During operation, as shown in  FIG. 2C , shaped X-ray beam  245  interacts with an object  260  under inspection, to produce scattered X-rays  246 . As shown, object  260  conceals therein, an item, person or material  261 . Scattered X-rays  246  are collimated by the plurality of collimator vanes  255  and are then detected by detectors  250  to produce scan data signal whose intensity is related to the effective atomic number (Z) near to the surface of object  260 . In accordance with an embodiment, each detector  250  maps to a specific focus area (of the object  260 ) which is defined by a width of X-ray fan beam  245  and an acceptance angle of the individual collimator vanes  255 . 
       Cone Beam 
       [0169]      FIG. 3A  illustrates another embodiment of a hand-held portable X-ray based scanning system  300 , also referred to as an imaging system or device, for use in screening objects such as, but not limited to, baggage, containers/boxes, and other similar items for threat materials, items or people concealed therein. In embodiments, components of system  300 , such as—a housing  305 , an upper surface  310 , a base, a handle  312 , a front surface  314 , a rear surface, a first side  318 , a second side, a first cuboid  325 , a central longitudinal axis  330 , and a second cuboid (or trapezoidal prism)  335 —are configured similar to corresponding components described above in context of  FIG. 1A . These components, and associated variations, are not described herein as they have been described in detail above. 
         [0170]    Referring now to  FIGS. 3A and 3B , housing  305  comprises an X-ray tube  340  whose anode  341 , also referred to as a target, emits a spatially localized X-ray beam  345  through an opening  342 , also referred to as an aperture. Housing  305  may include corresponding components such as a shield  343 , configured in a manner disclosed above in context of  FIGS. 1A and 1B . In one embodiment, X-ray beam  345  is cone shaped. 
         [0171]    A cathode and heater filament assembly may be configured, similar to embodiments described in above relation to the pencil beam embodiment. 
         [0172]    In accordance with an embodiment, shaped X-ray beam  345  emerges through an opening  344  at the center of front surface  314 , in a direction substantially perpendicular to front surface  314 . A plurality of X-ray backscatter detectors  350  are configured and operated similar to detectors  150  already described in context of  FIGS. 1A and 1B . As shown in  FIG. 3E , in accordance with an embodiment, an array of ‘m’ rows×‘n’ columns of detectors  350  are arranged onto a modular daughter card  351  with a single signal control and readout cable  352  to form a sensing module  353 . 
         [0173]    Similarly, the energy of the X-rays and signal quality can be maintained in a manner described above in context of the pencil beam embodiments. 
         [0174]    Referring now to  FIGS. 3A, 3D through 3F , in accordance with an embodiment of the present specification, a collimator grid  355  is positioned in front of detectors  350  and behind front surface  314 . Collimator grid  355  comprises a plurality of combs  365   a ,  365   b , made of a suitable attenuating material (such as tungsten, molybdenum or steel), each of plurality of combs  365   a ,  365   b  including a plurality of teeth  370   a ,  370   b . In accordance with an embodiment, plurality of combs  365   a ,  365   b  are assembled or arranged such that teeth  370   a  of a first set of combs  365   a  in a first direction  371   a  interlock with teeth  370   b  of a second set of combs  365   b  in a second direction  371   b  to thereby generate the collimator grid  355  having a plurality of grid collimators or collimator elements  374 . In one embodiment, second direction  371   b  is generally or approximately traverse or orthogonal to first direction  371   a . In accordance with an embodiment, the first set comprises ‘m’ number of combs  365   a  while the second set comprises ‘n’ number of combs  365   b  to generate a collimator grid  355  that has ‘m×n’ matrix of substantially rectangular grid collimators  374  at top surface  375 . 
         [0175]    In one embodiment, the planes of teeth  370   a ,  370   b , forming the grid collimators or collimator elements  374 , are in a direction substantially parallel to the orientation of the shaped X-ray beam  345  (that is, cone shaped beam  345 ) or perpendicular to the front surface of the housing. In some embodiments, the plurality of grid collimators or collimator elements  374  are arranged in a parallel configuration, wherein the planes of teeth  370   a ,  370   b  are substantially parallel to each other, such that a vertical dimension, such as height, of a vertical region is viewed through the collimators  374  to be of the same size as the extent or height ‘H’ of front surface  314 . In some embodiments, the plurality of grid collimators or collimator elements  374  are alternatively arranged in a focused configuration, wherein the planes of teeth  370   a ,  370   b  together form a diverging or converging orientation, such that the collimator elements  374  view either a smaller or larger of the vertical dimension, such as height, of the vertical region than the extent or the height ‘H’ of front surface  314 . In still various embodiments, the plurality of grid collimators or collimator elements  374  is arranged in a combination of parallel and focused configurations. 
         [0176]    In various embodiments, detectors  350  are arranged behind the interlocking collimator structure or collimator grid  355  such that at least one of detectors  350  is present per collimator element or grid collimator  374  in order to create a two-dimensional scan image. As shown in  FIG. 3F , collimator grid  355  is coupled to sensing module  353  (comprising the detector module  350  coupled to the daughter card  351  with the signal control and readout cable  352 ) such that the array of ‘m x n’ detectors  350  are positioned behind grid  355 . 
         [0177]    During operation, as shown in  FIG. 3C , shaped X-ray beam  345  interacts with an object  360  under inspection to produce scattered X-rays  346 . As shown, object  360  conceals therein, an item or material  361 . Scattered X-rays  346  is collimated by the plurality of grid collimators or collimator elements  374  and is then detected by the detectors  350  to produce scan data signal whose intensity is related to the effective atomic number (Z) near to the surface of object  360 . In accordance with an embodiment, each detector  350  maps to a specific focus area (of the object  360 ) which is defined by a solid angle of X-ray cone beam  345  and an acceptance angle of the individual collimator elements or grid collimators  374 . 
         [0178]    Conventional backscatter imaging systems typically use a tightly collimated pencil beam of X-rays and an un-collimated large area detector (referred to as “pencil beam geometry”) compared to the use of the collimated cone-shaped beam of X-rays and collimated detectors (referred to as “cone beam geometry”) in accordance with an aspect of the present specification. With reference to  FIG. 3A , the handheld device of the present specification has, in one embodiment, an outer diameter of 192 mm (considering a circular cross-section of the housing  105 ) of front surface  314  and is located at a distance of 100 mm from the object under inspection. Detector element  350  is, in an embodiment, 3 mm×3 mm with the X-ray source (X-ray tube  140 ) located a further 30 mm behind detector array  350  to provide room for radiation shielding around the source. In this embodiment, a total of 4096 detector elements are employed (to create a 64 pixel by 64 pixel image) with an equivalent dwell time of 500 microseconds for pencil beam geometry. 
         [0179]    To establish the relative efficiency of the pencil beam versus cone beam configuration, it is useful to calculate the relative solid angles of the whole detector face (pencil beam) and of a single detector to the equivalent inspection area as scanned by the pencil beam (for the cone beam case). This calculation shows that the solid angle for the collimated detector (used in cone beam geometry) is 290 times smaller than for the whole detector face (used in pencil beam geometry). 
         [0180]    Taking the assumed pencil beam dwell time of 500 microseconds and multiplying by the number of pixel locations to form an image (4096 in this case) yields an estimated image formation time in pencil beam geometry of 2 seconds. The calculation in the case of the cone beam geometry of the present specification suggests that the dwell time should be 290 times longer than for the pencil beam case to achieve equivalent image statistics, but with a single exposure since all pixel data is collected in parallel. Also, in the case of the cone beam geometry, the image exposure time is more than 50% less than an equivalent pencil beam. This yields an image exposure time in a range of 0.03 seconds 0.1 seconds. Therefore, near real-time two-dimensional image inspection is possible using Compton backscatter inspection in the cone beam geometry of the present specification. 
       Single-Axis Rotating Beam 
       [0181]      FIG. 4A  illustrates an embodiment of a hand-held portable X-ray based scanning system  400 , also referred to as an imaging system or device, for use in screening objects such as, but not limited to, baggage, containers/boxes, and other similar items for threat materials, items or people concealed therein. In embodiments, components of system  400 , such as—a housing  405 , an upper surface  410 , a base, a handle  412 , a front surface  414 , a rear surface, a first side  418 , a second side, a first cuboid  425 , a central longitudinal axis  430 , and a second cuboid (or trapezoidal prism)  435 —are configured similar to corresponding components described above in context of  FIG. 1A . These components, and associated variations, are not described herein as they have been described in detail above. 
         [0182]    Referring now to  FIGS. 4A and 4B , housing  405  comprises an X-ray tube  440  whose anode  441 , also referred to as a target, emits a spatially localized X-ray beam  445   a  through an opening  442 , also referred to as an aperture. A shield  443 , formed of an X-ray absorptive material, such as tungsten or uranium, surrounds anode  441  to absorb stray radiation emitted from anode  441 . Opening  442  is defined through a highly absorbing block or material (typically tungsten, steel and/or lead) to limit the X-ray radiation, emitted from anode  441 , and allow the X-ray radiation to emanate from X-ray tube  440  in the form of beam  445   a  of X-rays. A cathode and heater filament assembly may be configured, similar to embodiments described in above relation to the pencil beam embodiment. 
         [0183]    In accordance with an embodiment of the present specification, X-ray beam  445   a  is collimated by a collimator assembly  470 , enclosed within housing  405 , to generate a shaped X-ray beam  445   b . In one embodiment, X-ray beam  445   b  is shaped into a pencil beam. In accordance with an embodiment, shaped X-ray beam  445   b  emerges through an opening  444  at the center of front surface  414 , in a direction substantially perpendicular to front surface  414 . A plurality of X-ray backscatter detectors  450  are positioned adjacent to and behind front surface  414  such that they surround the area or region of emergence of X-ray beam  445   b  at opening  444  and cover a substantial area of front surface  414  in order to maximize detected backscatter signal. An embodiment of the present specification comprises four sets of detectors  450 , also referred to as sensors. 
         [0184]    An embodiment of collimator assembly  470  comprises a first collimator  472 , also referred to as a first limiting element, arranged coaxially in front of a second collimator  474 , also referred to as a second limiting element. In one embodiment first and second collimators  472 ,  474  are positioned between openings  443  and  444  such that collimator assembly  470  defines, shapes, or forms X-ray beam  445   a  into the shaped X-ray beam  445   b.    
         [0185]    Referring now to  FIGS. 4A through 4F , in one embodiment, first and second collimators  472 ,  474  are substantially circular disks having differing or same radii. In an embodiment, the respective centers of the first and second collimators  472 ,  474  are coaxial with the central longitudinal axis  430  of housing  405 . First collimator  472  has a first transmission pattern in the form of a through slit  473  extending in a spirally curved configuration from a point proximate center  475  to a point proximate the circumference of element  472 . Second collimator  474  has a second transmission pattern in the form of through slit  477  extending radially from a point proximate center  476  to a point proximate the circumference of element  474 . Thus, when two collimators  472 ,  474  are concurrently rotating, the respective first and second transmission patterns or slits  473 ,  477  generate or define the scanning X-ray pencil beam  445   b  across the surface of the object under inspection. 
         [0186]    In accordance with an embodiment, the first transmission pattern  473  defines a radial position of pencil beam  445   b  while the second transmission pattern  477  defines an azimuthal angle of pencil beam  445   b . For example, as shown in  FIG. 4D , when collimators  472 ,  474  (the two collimator disks  472 ,  474  are visible as a single disk since they are shown overlapping each other in  FIG. 4D ) are rotated relative to each other the position of pencil beam  445   b  moves or sweeps from a position  480   a  at the circumference to a position  480   d  at the coaxial centers  475 ,  476  (of the collimators  472 ,  474 ) through intermediate positions  480   b  and  480   c.    
         [0187]      FIG. 4E  illustrates a motor  485  driving the first and second collimators  472 ,  474  using a first and a second gear or drive wheels  486 ,  487  respectively. As would be evident to those of ordinary skill in the art, gears  486 ,  487 , also referred to as drive wheels, engage with mating gear teeth fabricated on the respective circumferences of two collimator disks  472 ,  474 . In accordance with an embodiment, first and second gears  486 ,  487  rotate the collimator disks  472 ,  474  such that two collimators  472 ,  474  are in lock step with each other but rotate at varying speeds to form beam  445   a  into the shaped X-ray beam  445   b . In one embodiment, collimator disk  474  rotates more quickly compared to the speed of rotation of collimator disk  472 . In one embodiment, collimator disk  472  rotates more quickly compared to the speed of rotation of collimator disk  474 . In one embodiment, the drive wheel or gears  486 ,  487  affixed to a common spindle (not visible) are driven by motor  485  to rotate collimator disks  472 ,  474  while two sets of additional free running wheels  488 ,  489  (not driven by motor  485 ), shown in  FIG. 4F , support collimator disks  472 ,  474  to maintain their position or orientation relative to X-ray tube  440  (or opening  442 ). 
         [0188]    A plurality of X-ray backscatter detectors  450  are configured and operated similar to detectors  150  already described in context of  FIGS. 1A and 1B . Similarly, energy of the X-rays and signal quality can be maintained in a manner described earlier in context of the pencil beam embodiments. 
         [0189]    During operation, as shown in  FIG. 4G , shaped X-ray beam  445   b  interacts with an object  460  under inspection to produce scattered X-rays  446 . As shown, object  460  conceals therein, an item or material  461 . Scattered X-rays  446  are then detected by detectors  450  to produce scan data signal whose intensity is related to the effective atomic number (Z) near to the surface of object  460 . Any one or more of the aforementioned collimation systems can be combined with this single-axis rotating beam embodiment to effectively detect scattered X-rays. 
       Dual-Axis Rotating Beam 
       [0190]      FIG. 5A  illustrates another embodiment of a hand-held portable X-ray based scanning system  500 , also referred to as an imaging system or device, for use in screening objects such as, but not limited to, baggage, containers/boxes, and other similar items for threat materials, items or people concealed therein. In embodiments, components of system  500 , such as—a housing  505 , an upper surface  510 , a base, a handle  512 , a front surface  514 , a rear surface, a first side  518 , a second side, a first cuboid  525 , a central longitudinal axis  530 , and a second cuboid (or trapezoidal prism)  535 —are configured similar to corresponding components described above in context of  FIG. 1A . These components, and associated variations, are not described here to avoid repetition. 
         [0191]    Referring now to  FIGS. 5A and 5B , housing  505  comprises an X-ray tube  540  (shown separated out from housing  505  in  FIG. 5B ) whose anode  541 , also referred to as a target, emits a spatially localized X-ray beam  545   a  through an opening  542 , also referred to as an aperture. A shield  543 , formed of an X-ray absorptive material, such as tungsten, steel, lead or uranium, is disposed to surround and enclose anode  541  to absorb stray radiation emitted from anode  541 . Further, the anode is surrounded by a highly absorbing block or material  593  (typically tungsten, steel and/or lead) through which opening  542  is defined. In an embodiment, opening  542  is a cone beam collimator slot and defines the overall area for X-ray emission, emitted from anode  541  in the form of beam  545   a , with the moving collimator parts described below. In some embodiments, opening  542  is shaped so that X-ray beam  545   a  emanates as a cone beam. Also, in an embodiment, the head portion of X-ray tube  540 , comprising opening  542 , is shaped in a substantially spherical form. A cathode and heater filament assembly (not shown) may be configured, similar to embodiments described in above relation to the pencil beam embodiment. 
         [0192]    An embodiment of collimator assembly  570  comprises a collimator  572 , also referred to as a limiting element, partially surrounded by a shaped support or cradle element  574 . In various embodiments, support or cradle  574  has a substantially semi-circular, ‘U’ or ‘C’ shape. In an embodiment, collimator  572  is a circular disk having a first radius. In one embodiment, where cradle  574  is substantially semi-circular shaped, it has a second radius, greater than the first radius, so that cradle  574  partially encompasses collimator  572 . In accordance with an embodiment collimator  572  and cradle  574  are positioned between openings  543  and  544  such that a movement of collimator assembly  570  defines, shapes or forms X-ray beam  545   a  into pencil shaped X-ray beam  545   b.    
         [0193]    Referring now to  FIGS. 5A through 5E , in one embodiment, the respective centers of collimator  572  and cradle  574  are substantially coaxial with central longitudinal axis  530  of housing  505 . Collimator  572  has a transmission pattern in the form of a through opening  573  at a point between the center and the circumference of element  572 . Collimator  572  is rotatable, about central longitudinal axis  530 , through a bearing  582  supported by shaped cradle  574 . Cradle  574  is fixed to pivoting mounts that allow cradle  572  to be oscillated about a vertical axis  532 . In accordance with an aspect of the present specification, a motor  585  rotates or spins collimator  572 , at a speed, about central longitudinal axis  530  while the supporting element or cradle  574  vibrates or oscillates, from side to side, about vertical axis  532  thereby causing the rotating or spinning collimator  572  to also vibrate or oscillate. In various embodiments, collimator  572  rotates at a speed ranging between 100 to 5000 RPM. In one embodiment, collimator  572  speed is 2000 RPM. 
         [0194]    Rotating collimator  572  defines pencil beam  545   b  that sweeps a trajectory in a substantially vertical plane where the X-ray focal spot is in the plane of collimator  572  and on longitudinal axis  530  of bearing  582 . The vibratory or oscillatory movement of cradle  574  and therefore that of collimator  572  causes pencil beam  545   b  to sweep over the substantially vertical plane moving from left to right and back again. The combined effect of the rotatory or spinning and oscillatory or vibratory movement of the collimator assembly  570  is one where pencil beam  545   b  moves in a raster pattern over a two dimensional area of the object under inspection. FIG.  5 E shows X-ray tube  540  positioned within the moving collimator assembly  570  so that the substantially spherical shaped head portion  590  of X-ray tube  540 , comprising opening  542 , and rotating collimator  572  (supported by cradle  574 ) enable tight radiation collimation as X-ray beam  545   b  is scanned. The substantially spherical shaped head portion  590  of X-ray tube  540  allows the rotating and rocking or oscillating collimator  572  to efficiently move around head  590  with minimum radiation leakage. 
         [0195]    A plurality of X-ray backscatter detectors  550  are configured and operated similar to detectors  150  already described in context of  FIGS. 1A and 1B . Similarly, energy of the X-rays and signal quality can be maintained in a manner described earlier in context of the pencil beam embodiments. 
         [0196]    In one embodiment, detectors  550  are scintillator based detector arrays with light guide readout to photomultiplier tubes. 
         [0197]    During operation, as shown in  FIG. 5F , shaped X-ray beam  545   b  interacts with an object  560  under inspection to produce scattered X-rays  546 . As shown, object  560  conceals therein, an item or material  561 . Scattered X-rays  546  are then detected by detectors  550  to produce scan data signal whose intensity is related to the effective atomic number (Z) near to the surface of object  560 . Any one or a combination of the collimation systems disclosed above may be combined with this embodiment. 
         [0198]    The position of the collimators is used to accurately correct images. Referring to  FIG. 6A , a plurality of sensors  640  (corresponding to at least one of the detectors or detector systems mentioned in the embodiments above) is used to acquire data and communicate that data to a data acquisition system (DAQ)  610 . DAQ  610 , in turn, controls motor drivers responsible for creating collimator motion. Such motors include an azimuth motor  675  and a collimator motor  670 . Rotary encoders  680  monitor the absolute position of the collimators and supply that information to DAQ  610  which, in turn, uses it to correct an acquired image based upon such position data. 
         [0199]    As shown in  FIG. 6B , in another embodiment, scan data  605  produced by plurality of detectors  645  (corresponding to at least one of the detectors or detector systems mentioned in the embodiments above) is accumulated into DAQ  610  wherein scan data  605  is summed within appropriate or optimal sampling time slots, time bins, or time periods. It should be appreciated that the shorter the sampling time period the noisier is the collected scan data but the more accurate or focused it is in terms of spatial location. In various embodiments scan data  605  sampling time slots, time bins, or time periods vary between 0.01 ms and 100 ms. In one embodiment, scan data  605  sampling time slot or time period is of 1 ms duration. A processing element  650 , such as a microprocessor or a digital signal processor (DSP), is in data communication with DAQ  610  to perform a plurality of analyses or calculations using at least scan data  605 . In one embodiment, scan data  605  is analyzed by comparing a mean scan signal level calculated over one or more temporal sampling periods with a background reference level. The bigger the difference between the sampled signal and the background level, the more substantial is the scattering object. 
         [0200]    In accordance with an embodiment where a fan beam is utilized, the analysis is computed behind each of the plurality of collimator vanes  255  ( FIGS. 2A, 2B ), independently, in order to enable spatial localization and detection of even small anomalies. In further embodiments, to improve signal-to-noise ratio, the intensity of detected scatter signal  605  is estimated over all detectors  645  (corresponding to at least one of the detectors or detector systems mentioned in the embodiments above) by calculating a weighted sum of the pixel based and total signal data analysis. 
         [0201]    In accordance with an aspect of the present specification, for each of the embodiments (illustrated in  FIGS. 6A and 6B ) disclosed above, the detected scatter scan data  605  is utilized to generate an alarm or feedback for the operator. In various embodiments the alarm or feedback is in the form of an audible tone and/or a scan image of the object under inspection. Accordingly, detected scatter scan data  605  is converted, using a speaker  615 , into an audible tone or alarm, the pitch or frequency of which, in one embodiment, is directly proportional to the scatter signal. For example, speaker  615  emits a background tone at about 100 Hz with an average signal of 1000 detected scatter X-rays producing a frequency of about 400 Hz. Thus, a scattering object which generates a signal of 500 detected scatter X-rays would produce a tone at about 250 Hz. It will be appreciated by one of ordinary skill in the art that alternative mapping between detected scatter signal and audible tone or alarm can be envisioned, such as one which provides an exponential increase in tone, pitch or frequency to provide greater contrast for low scattering objects than for high scattering ones. 
         [0202]    The probability of an X-ray photon interacting with the object under inspection depends strongly on the atomic number of the object—that is, the higher the atomic number the higher the probability of interaction. Similarly, the probability of absorbing a Compton scattered X-ray also depends strongly on the atomic number of the object under inspection. Therefore, it is known by those skilled in the art that the Compton backscatter signal is highest for low atomic number materials such as organic materials and people and is smallest for high atomic number materials such as steel and lead. 
         [0203]    Additionally or alternatively, the scan image of the object under inspection is displayed on at least one display  620 . A visual feedback, such as the scan image, is advantageous to enable the operator to notice subtle differences between one scattering object and another since the human visual system has a natural ability at identifying shapes and associating these shapes with specific threats (such as a gun or a knife). Referring to  FIG. 6B , in order to form the scan image, an embodiment of the present specification includes a 3D gyroscope  625  and/or a 3D accelerometer  630  within the respective housings. 3D gyroscope  625  is used to track a first data stream indicative of an absolute position or pointing direction of the X-ray beam or hand-held device in 3D space, while 3D accelerometer  630  tracks a second data stream indicative of rapid relative movements of the X-ray beam in 3D space. In accordance with an embodiment, the first and second data streams are input into and combined by processing element  650  to generate position or coordinates  640  of the X-ray beam at all times during scanning operation, even in response to rapid movement of the beam or hand-held device (in embodiments described above) by the operator. 
         [0204]    According to an aspect of the present specification, each position or coordinate of the X-ray beam in 3D space has associated plurality of active pixels that correspond to the particular spatial location, on the object under inspection, where the X-ray beam is interacting. These active pixels are located within a matrix of other potentially active pixels which together constitute an image. In a practical scenario, it is reasonable to assume that the operator will sweep the X-ray beam over the object more than once causing multiple scan frames to contribute to a pixel in the image. Therefore, in order to ensure a quantitative image, the brightness or scan data of each pixel is corrected by the total X-ray beam dwell time at that pixel location. This dwell time is calculated over all periods that the X-ray beam is present over each active pixel. 
         [0205]    The number of X-rays reaching the object under inspection is defined by the X-ray beam collimator aperture and beam divergence. The area of the object under inspection that is covered by the X-ray beam is then determined by the distance of the X-ray source from the object under inspection—that is, the larger the distance the larger the area of the object covered by the X-ray beam. The number of scattered X-rays that return to the detector is inversely proportional to the distance between the object under inspection and the detector array. Thus, in one operating condition, the hand-held device of the present specification as described in various embodiments above is held close to the object under inspection, so that the area of the object irradiated by the X-ray beam is small and the fraction of the scattered signal collected by the detector is high. 
         [0206]      FIG. 7  is a flow chart illustrating a plurality of exemplary steps of a method of scanning an object using an X-ray beam projected by the hand-held portable device of the present specification. At  705 , an operator first sweeps the X-ray beam onto the object using a coarse scanning pattern during which a change in audible tone is used as the primary feedback to identify anomalies with reference to the object. The coarse scanning pattern, in one embodiment, refers to a fairly quick scanning or sweeping movement of the X-ray beam over the surface of the object, referred to as the general scanning area, where the coarse scanning pattern is defined as having a first density of X-ray coverage over the general scanning area. If no anomaly is identified, at  710 , then the scan of the object is stopped, at  712 , and a new scan session for another object can begin, if required. However, if an anomaly is identified, at  710 , the operator then proceeds to make fine scanning patterns or relatively slower movements of the X-ray beam around the anomalous area, at  715 , where the fine scanning pattern is defined as having a second density of X-ray coverage over the anomalous area. It should be appreciated that the anomalous area is smaller than, but positioned within, the general scanning area. It should also be appreciated that the second density (associated with the fine scanning pattern) is greater than the first density (associated with the coarse scanning pattern). 
         [0207]    On initiating the fine sweep scanning of the object, the followings tasks are performed: at  716 , data is received from a 3D gyroscope representing a direction of pointing of the X-ray beam projected onto the object; at  717  a plurality of active pixels corresponding to the direction of the X-ray beam are calculated; at  718 , a dwell time of the X-ray beam at each of the active pixels is calculated; and at  719 , a scan image after correcting the scan data signal is generated, at each of the active pixels, using the dwell time. At  720 , data from a 3D accelerometer is obtained to check if there is a movement of the X-ray beam relative to the direction of the X-ray beam obtained at  716 . If there is no movement of the X-ray beam detected, at  723 , then the steps  717  to  720  are repeated (till a movement of the X-ray beam is detected). 
         [0208]    However, if a movement of the X-ray beam is detected, at  723 , then the following tasks are performed: at  725 , data is received from the 3D gyroscope representing a new direction of the X-ray beam due to the movement of the X-ray beam; at  726 , a plurality of active new pixels corresponding to the new direction of the X-ray beam are calculated; at  727 , a dwell time of the X-ray beam at each of the active new pixels is calculated; and at  728 , an updated scan image is generated after applying the dwell time correction to the scan data signal at each active pixel. 
         [0209]    At  730 , data from the 3D accelerometer is obtained again to check if there is a continued movement of the X-ray beam. If it is determined at  733  that the X-ray beam is still moving or being swept over the object, then steps  725  to  730  are repeated (till the X-ray beam sweeping movement stops). However, in case there is no detected movement of the projected X-ray beam at  733 , then at  735  a check is performed to determine whether the scanning has to be stopped (and therefore, move to  740 ) or another scanning session or event should begin from 705 onwards. The scan image generated at  719  and/or  728  is visually analyzed by the operator to determine further features of the anomaly and declare the anomaly as benign or threat. 
         [0210]    In various embodiments of the present specification, the hand-held device of the present specification, such as those in embodiments described above, includes a laser-beam range finder or any other suitable optical sensor beam, known to persons of ordinary skill in the art, is used to propagate an optical, visible light or laser beam along the central path of the X-ray beam (for example, by deflecting a laser beam using a thin gold coated Mylar film reflector in the X-ray beam path). The directed optical or laser beam is used to calculate the distance of the hand-held device from the object under inspection so that the surface of the object can be reconstructed in three-dimensional (3D) space (using the measured distance to the surface of the object taken in combination with the gyroscope and/or accelerometer data) in order to create an X-ray image that wraps around the three-dimensional surface of the object under inspection. Such a three-dimensional view can help the image interpreter or operator to better identify or estimate the exact location of the anomaly or threat object, area or region. 
         [0211]    The above examples are merely illustrative of the many applications of the system of present specification. Although only a few embodiments of the present invention have been described herein, it should be understood that the present invention might be embodied in many other specific forms without departing from the spirit or scope of the invention. Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention may be modified within the scope of the appended claims.