Patent Publication Number: US-2020300791-A1

Title: Multi-tiered systems and methods for composition analysis

Description:
RELATED INVENTIONS 
     This application claims priority to U.S. Provisional Application Ser. No. 62/820,046, entitled “Multi-Tiered Systems and Methods for Composition Analysis,” filed Mar. 18, 2019, the subject matter of which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates generally to systems and methods for inspection and diagnostic imaging, for example to identify explosives or other harmful materials. 
     Non-invasive screening of packages and luggage with high specificity for explosive material is an important priority for aviation and/or other security. As the number of air travelers increases, the number of false alarm events also increases, resulting in flight delays and negative passenger experience. Further, current approaches may not be as adaptable as desirable to evolving threats. 
     To address the baggage inspection issue, current aviation industry practice relies on a two-tiered inspection operation, first requiring all bags to go through a first-tier explosive detection system (EDS) tuned for high sensitivity and then transfering to the secondary tier the luggage that triggered alarms. Generally, two main approaches that are currently used for secondary inspection include a first approach of detecting trace quantities of molecules of explosive released in air or dispersed on surfaces, and a second approach relying on specific outcomes of x-rays interacting with an object being investigated, such as absorption, scattering, or diffraction of x-rays. Explosive trace detectors are based on ion spectrometry techniques. Such approaches, however, may be defeated by some new classes of explosives or by sealing against release of vapors. Further, collection of samples by contact or non-contact methods has a large variability in different environments and presents a challenge. With respect to the use of x-rays for secondary screening, the acquired data may be limited to material density and effective atomic number per voxel, leaving ambiguity in differentiating explosives from some types of common materials. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, a diagnostic system is provided that includes a primary detection system, a secondary detection system, and at least one processor. The primary detection system is configured to acquire initial data of an object being analyzed. The secondary detection system includes at least one neutron source and at least one gamma-ray detector or neutron detector. The at least one detector is configured to acquire spectral emission data from the object generated responsive to neutrons provided by the at least one neutron source. The at least one processor is configured to acquire, from the primary detection system, the initial data from the object; determine a sub-portion of the object for further analysis using the initial data; direct at least one neutron beam burst from the at least one neutron source toward the sub-portion; acquire, from the secondary detection system, the spectral gamma-ray emission data from the object; and determine a presence of a substance using the spectral emission data (e.g., determine with a sufficient probability confidence that the emission detected is compatible with a harmful (e.g., explosive) material hypothesis). The determination may be repeated or continued until the probability is above a threshold (for example, 95% or higher) set by the operator as signifying with sufficient confidence the presence of a harmful or contraband substance. 
     In another embodiment, a method is provided that includes acquiring initial data of an object being analyzed via a primary detection system. The method also includes determining a sub-portion of the object for further analysis using the initial data, and directing at least one neutron from at least one neutron source of a secondary detection system toward the sub-portion of the object. Further, the method includes acquiring spectral emission data from the object via at least one detector of the secondary detection system, and determining a presence of a substance using the spectral emission data. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  provides a schematic block diagram of a diagnostic system in accordance with various embodiments. 
         FIG. 2  provides a schematic view of a system including plural detectors in accordance with various embodiments. 
         FIG. 3  provides an example view of a neutron beam footprint in accordance with various embodiments. 
         FIG. 4  provides an example of a graph depicting ratios of different chemical elements in benign and harmful materials. 
         FIG. 5  provides a flowchart of a method in accordance with various embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description of certain embodiments will be better understood when read in conjunction with the appended drawings. To the extent that the figures illustrate diagrams of the functional blocks of various embodiments, the functional blocks are not necessarily indicative of the division between hardware circuitry. For example, one or more of the functional blocks (e.g., processors or memories) may be implemented in a single piece of hardware (e.g., a general purpose signal processor or a block of random access memory, hard disk, or the like) or multiple pieces of hardware. Similarly, the programs may be stand alone programs, may be incorporated as subroutines in an operating system, may be functions in an installed software package, and the like. It should be understood that the various embodiments are not limited to the arrangements and instrumentality shown in the drawings. 
     As used herein, the terms “system,” “unit,” or “module” may include a hardware and/or software system that operates to perform one or more functions. For example, a module, unit, or system may include a computer processor, controller, or other logic-based device that performs operations based on instructions stored on a tangible and non-transitory computer readable storage medium, such as a computer memory. Alternatively, a module, unit, or system may include a hard-wired device that performs operations based on hard-wired logic of the device. Various modules or units shown in the attached figures may represent the hardware that operates based on software or hardwired instructions, the software that directs hardware to perform the operations, or a combination thereof. 
     “Systems,” “units,” or “modules” may include or represent hardware and associated instructions (e.g., software stored on a tangible and non-transitory computer readable storage medium, such as a computer hard drive, ROM, RAM, or the like) that perform one or more operations described herein. The hardware may include electronic circuits that include and/or are connected to one or more logic-based devices, such as microprocessors, processors, controllers, or the like. These devices may be off-the-shelf devices that are appropriately programmed or instructed to perform operations described herein from the instructions described above. Additionally or alternatively, one or more of these devices may be hard-wired with logic circuits to perform these operations. 
     As used herein, an element or step recited in the singular and preceded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular property may include additional elements not having that property. 
     Various embodiments provide a multi-tiered approach to detection of one or more materials, such as explosives. For example, in various embodiments, objects are first processed through a first-tier explosive detection system (EDS) tuned for high sensitivity (e.g, a primary detection system), and then only objects that triggered an alarm are transferred to a subsequent tier (e.g., a secondary detection system) for further examination. The subsequent tier or secondary detection system is configured to detect explosive substances with extremely high specificity, thus distinguishing explosive substances with high confidence from benign materials. One challenge for such systems is the prevalence in explosives of low-Z chemical elements (e.g., N,  0 , C) with similar concentrations in common substances, as illustrated in  FIG. 4 . 
     To achieve high specificity for secondary screening and to help defeat any concealing countermeasures, various embodiments use an intelligent active interrogation system, probing luggage, packages, and/or other objects with pulses of fast neutrons to detect high energy gamma rays emerging from nuclear reactions with nitrogen, carbon, and oxygen. In conjunction with prior data from primary screening, the composition of the object may be predicted with high accuracy. 
     In various embodiments, a trade-off between radioprotection concerns and the benefit of deep penetration of neutrons and high energy gamma rays is addressed by adopting a dose-sensitive, intelligent operation of a neutron generator source. For example, data from a primary screening (e.g., x-ray) may be utilized to start neutron probing only on a particular volume or region of an object identified as suspicious by the primary screening. Further, various embodiments employ a multi-step, on-off operation of a neutron source, such as by turning the neutron source on for a scout shot, turning off and analyzing data detected in response to the scout shot, deciding whether to proceed based on the analyzed data, and iterating until a desired confidence level is achieved, (e.g., as discussed in [ 0005 ] herein). The multi-step interrogation of the material reduces both the radiation dose near the secondary inspection system during operation and the potential delayed radioactivity induced in specific chemical elements that may be present in the object. 
     Various embodiments utilize the detection of prompt gamma rays in the energy range from about 4 to 11 MeV as offering improved signal to noise ratio for simultaneous nitrogen, carbon, and oxygen detection. Such a range is above the normal K-Th-U (potassium-thorium-uranium) gamma background, while high sensitivity detection of multi-MeV gammas from neutron-induced reactions is feasible using commercially available large scintillators coupled to photomultipliers or other types of photosensors. 
       FIG. 1  provides a schematic block view of a diagnostic and inspection system  100  formed in accordance with various embodiments. The diagnostic system  100  includes a primary detection system  110 , a secondary detection system  120  (which includes at least one neutron source  130  and at least one detector  140 ), and a processing unit  150 . Generally, the diagnostic and inspection system  100  is used to identify the presence of one or more materials or compositions, such as explosives, narcotics, contraband, etc. For example, the diagnostic system  100  may be deployed at an airport or shipping facility, and used to inspect luggage and/or packages passing through the airport or shipping facility. The diagnostic system  100  is configured as a tiered system, including a first tier represented by the primary detection system  110  and a second tier represented by the secondary detection system  120 . In various embodiments, the primary detection system  110  may be utilized to determine the possible presence of a material of interest as well as a particular volume of an examined item where the material of interest is located, and the secondary detection system  120  used to analyze the particular volume identified to confirm whether or not the material of interest is actually present. 
     In the illustrated embodiment, the primary detection system  110  is configured to acquire initial data of an object  102  (e.g., package or item of luggage) being analyzed. In various embodiments, the primary detection system  110  may be an x-ray system. The primary detection system  110  may be used to acquire the initial data, which may include data indicating whether there is a risk of an explosive or other harmful material within the object  102 , as well as data describing, defining, or corresponding to the location of the potential harmful material within a sub-area and/or sub-volume of object  102 . In the illustrated embodiment, sub-portion  104  of the object  102  indicates a location within the object  102  for which a potentially harmful material has been indicated by the primary detection system  110 , with the primary detection system  110  utilized to determine the location and size of the sub-portion  104 . If no potentially harmful materials are identified by the primary detection system  110 , the object  102  may be further processed without being examined with the secondary detection system  120 . 
     It may be noted that, in various embodiments, the initial data comprises depth data (e.g., identifying the location of portions of interest at a depth within the volume of the object  102 ), allowing improved positioning of the object  102  within the secondary detection system  120  and/or improved directing or shaping of the neutron beam from the secondary detection system  120 . 
     The depicted secondary detection system  120  includes a neutron source  130  and a detector  140 . It may be noted that in various embodiments, more than one neutron source  130  and/or more than one detector  140  may be employed. Generally the neutron source  130  is used to direct neutrons (e.g., via a neutron beam) toward the sub-portion  104  of the object  102 . For example, the neutron source  130  may include or have associated therewith a source collimator  132  for directing neutrons emitted from the neutron source  130 . 
     The detector  140  is configured to acquire spectral gamma-ray emission data from the object that is generated responsive to neutrons provided by the neutron source  130 . In some embodiments, the detector  140  includes a detector scintillator  143  configured to generate light photons in response to photon or gamma ray impacts, and also include a photodetector  144  for detecting the light generated by the detector scintillator  143 . 
     In various embodiments, the secondary detection system  120  (e.g., the detector  140 ) includes a neutron trap structure to help improve gamma detector sensitivity and to reduce spurious secondary gamma rays from an uncollided neutron beam transmitted through the object  102 . For example, in the embodiment depicted in  FIG. 1 , the detector  140  includes a neutron trap  145 . The depicted neutron trap  145  has three different layers—a first layer  146 , a second layer  147 , and a third layer  148 . Each layer includes one or more corresponding materials configured to absorb or react with particular types of neutrons and/or gamma rays. For example, in the illustrated embodiment, the first layer  146  includes first materials that reduce fast neutron energy, the second layer  147  includes second materials that absorb slowed down neutrons, and the third layer  148  includes third materials that absorb energy of gamma rays emitted in the process of neutron capture. 
     As discussed herein, in various embodiments more than one neutron source  130  and/or more than one detector  140  may be employed. For example, in various embodiments, the diagnostic system  100  includes plural detectors  140  configured to at least partially surround the object  102 .  FIG. 2  provides a schematic view of an embodiment of the diagnostic system  100  including plural detectors  140 . As seen in  FIG. 2 , the diagnostic system includes detectors  140   a ,  140   b ,  140   c , and  140   d  arranged as a semi-ring disposed about the object  102 . It may be noted that other shapes (e.g., an “L” or “V” shape) may be used, or that a complete ring surrounding the object entirely may be used in various embodiments. Use of additional detectors helps to acquire more data (e.g., to improve signal-to-noise ratio) and may also be used to provide additional directionality data of emissions from the object  102 . Additionally or alternatively, the diagnostic system  100  may include plural neutron sources. For example, the example diagnostic system  100  depicted in  FIG. 2  includes two neutron sources—neutron source  130   a  and neutron source  130   b . Plural neutron sources in various embodiments may be positioned around the object  102  for optimal positioning and/or direction of multiple neutron beams toward the sub-portion  104 . 
     It may be noted that in various embodiments, data from the detector  140  is only used for determining spectral data, in which case spatial or directional data describing the shape of the sub-portion  104  may not be required. Accordingly, in such embodiments, collimation of gamma rays impacting the detector  140  of the secondary detection system  120  may be avoided to allow for increased or maximum numbers of detected events by the detector  140 . However, in other embodiments, spatial data describing the sub-portion  104  from the detector  140  may be desirable. Accordingly, in some embodiments, one or more detectors  140  include a corresponding detector collimator, wherein the secondary detections system acquires secondary spatial data in addition to the spectral emission data. For example, as seen in  FIG. 2 , some of the detectors  140  (but not all in the illustrated embodiment) include or have associated therewith a detector collimator  142  configured to control the direction of gamma rays impacting the corresponding detector  140 , by limiting the angles from which impacting rays may approach the corresponding detector  140 . In other embodiments, each detector  140  may have an associated collimator  142 , while in other embodiments, no detectors  140  may have an associated collimator  142 . 
     In various embodiments, the secondary detection system  120  may be configured to position the object  102  in a preferred or ideal position for accurate and/or efficient scanning (e.g., to position the sub-portion  104  in a desired spatial relationship with one or more neutron beams emitted by the secondary detection system  120 ). For example, in the embodiment illustrated in  FIG. 2 , the secondary detection system  120  includes a translation system  222  (e.g., a system including a belt, rail, or other linear translation guide) and a rotation system  224  (e.g., a system including a turntable) configured to align the object  102  (e.g., the sub-portion  104 ) with a neutron beam emitted from the secondary detection system  120 . Spatial data from the initial data acquired via the primary detection system  110  may be used to determine a preferred or optimal position for examination by the secondary detection system  120 . 
     Returning to  FIG. 1 , the processing unit  150  includes at least one processor. In the illustrated embodiment, the processing unit  150  is operably coupled to the primary detection system  110  and secondary detection system  120 , and receives data from the primary detection system  110  and the secondary detection system  120  as well as provides commands signals to control the operation of the primary detection system  110  and the secondary detection system  120 . In various embodiments the processing unit  150  includes processing circuitry configured to perform one or more tasks, functions, or steps discussed herein. It may be noted that “processing unit” as used herein is not intended to necessarily be limited to a single processor or computer. For example, the processing unit  150  may include multiple processors, ASIC&#39;s, FPGA&#39;s, and/or computers, which may be integrated in a common housing or unit, or which may distributed among various units or housings. It may be noted that operations performed by the processing unit  150  (e.g., operations corresponding to process flows or methods discussed herein, or aspects thereof) may be sufficiently complex that the operations may not be performed by a human being within a reasonable time period. For example, the determination or identification of materials or compositions based on data acquired via the detector  140  may rely on or utilize computations that may not be completed by a person within a reasonable time period. The depicted processing unit  150  includes a memory  152 . The memory  152  may include one or more computer readable storage media. The memory  152 , for example, may store acquired emission data, results of intermediate processing steps, or the like. Further, the process flows and/or flowcharts discussed herein (or aspects thereof) may represent one or more sets of instructions that are stored in the memory  152  for direction of operations of the diagnostic system  100 . 
     The depicted processing unit  150  is configured (e.g., programmed) to acquire the initial data from the object  102  via the primary detection system  110 . For example, the processing unit  150  in various embodiments provides control signals to direct operations of the primary detection system  110  and receives data signals from the primary detection system  110  (e.g., signals from a detector of an x-ray system). 
     The processing unit  150  then determines or identifies the sub-portion  104  of the object  102  for further analysis using the initial data. For example, x-ray data may provide an indication of substantial or significant risk of an explosive device in a particular area or volume of the object  102 . The processing unit  150 , using the data received via the primary detection system  110 , determines which portion or portions of the object  102  have the risk or potential for explosives or other harmful materials and identifies or defines the sub-portion  104  within the entire volume of the object  102 . In various embodiments, the sub-portion  104  may be defined in 2 dimensions (as a cross-section throughout a dimension of the object  102 ), or in 3 dimensions (as a volume at a specified ranges of depths along three dimensions of the object  102 ). 
     The processing unit  150  is also configured to direct at least one neutron beam from the neutron source  130  toward the sub-portion  104 . For example, in various embodiments, the processing unit  150  is configured to control the secondary detection system  120  to acquire the spectral emission data in an energy range from about 4 MeV to about 11 MeV. The processing unit  150  may send control signals to the neutron source  130  to control the energy of emissions for the neutron source  130 . As discussed herein, such a range in various embodiments offers improved signal to noise ratio for simultaneous nitrogen, carbon, and oxygen detection. 
     As another example, in various embodiments, the processing unit  150  may control the source collimator  132  to shape the neutron beam emitted from the source collimator  132  and direct the neutron beam toward the sub-portion  104 . In various embodiments, the secondary detection system  120  is configured to focus at least one neutron beam to a footprint complementary to the sub-portion  104 . For example, the processing unit  150  may provide control signals to the source collimator  132  to control the position of one or more blades defining one or more apertures to provide the desired footprint for the neutron beam.  FIG. 3  provides an example of such a footprint. In the example of  FIG. 3 , the sub-portion  104  defines a square shape, and the footprint  300  of the neutron beam is a square slightly larger (e.g., 5% or 10% larger in various embodiments) than the square defined by the sub-portion  104 . In other embodiments, the footprint may be configured to precisely match the shape of the sub-portion  104  (or as closely as practically achievable). Generally, the closer the footprint  300  matches the sub-portion  104 , the better the signal-to-noise ratio. Spatial data from the initial data acquired via the primary detection system  110  may be used to determine the desired footprint. 
     Exposure to the neutron beam results in emission of neutrons and/or gamma rays from the sub-portion  104  of the object  102 , providing spectral emission data describing the response of the sub-portion  104  to the neutron beam at different energy levels along a spectrum of energy levels, which may be detected by the detector  140  of the secondary detection system  120 . The spectral emission data may be represented by a chart or graph plotting event counts or gamma yield per neutron on one axis and gamma energy levels on another axis. The processing unit  150  then acquires the spectral emission data from the sub-portion  104  of the object  102  via the secondary detection system  120 . For example, in various embodiments, the processing unit  150  provides control signals to direct operations of the secondary detection system  120  and receives data signals from the secondary detection system  120 . It may be noted that exposing only the sub-portion  104  of the object  102  to the neutron beam helps reduce the time and expense of testing, as well as reducing the amount of dose released instantaneously and in delayed activation. Using the spectral emission data, the processing unit  150  next determines the probability of presence of a substance that is either harmful or benign. In various embodiments, the processing unit may calculate, based on a physical model employing the initial data, possible secondary detector output responses if different material compositions, including explosive or benign materials, occupy the sub-portion of the object, and compare the spectral emission data from the secondary detection system with the possible secondary detector output responses to identify a possible match. 
     For example, an explosive or other harmful material may have a known response along a spectrum of energies which may be catalogued as a spectral emission signature along with spectral emission signatures of other explosives or harmful substances. The processing unit  150  may store such signatures in a database (e.g., in memory  152 ) or be communicably coupled with an external source that includes a catalog of such signatures. The processing unit  150  may then compare the acquired spectral emission data with the signatures in the catalog or database, and, if the signature or profile of the acquired spectral emission data matches one or more catalogued signatures of harmful materials, identify the sub-portion  104  as having a harmful material. 
     It may be noted that, in various embodiments, the processing unit  150  is configured to determine (e.g., determine with a sufficient probability or at a sufficient confidence level) the presence of the substance based on a spectral signature corresponding to a ratio of two or more materials. For example, a ratio of densities of C, N, and O has been identified, as shown in FIG. 4, which is reproduced from FIG. 4 of “Neutron-Activated Gamma-Emission: Technology Review” by Marc Litz, Christopher Waits, and Jennifer Mullins, Army Research Laboratory, January 2012, the entire subject matter of which is hereby incorporated by reference in its entirety. Use of such ratios in various embodiments improves the ability to distinguish between explosives and harmless materials. 
     It may be noted that the processing unit  150  is depicted for ease of illustration as a single block; however, the processing unit  150  may include a number of processors housed in more than one physical unit. For example, the processing unit  150  may include one or more processors located in the same unit or structure as the primary detection system  110  and/or the neutron source  130  and/or the neutron detector  140 , additionally or alternatively to a separately housed unit. Further, aspects of the processing unit  150  may be located remote from the detection system. Further it may be noted that the processing unit  150  may be configured to operate autonomously (e.g., without operator intervention), or may operate using interaction with an operator (e.g., by providing prompts and/or receiving commands from an operator). 
     It may be noted that some materials produce a relatively high level of radioactivity when exposed to a neutron beam, and it may be desirable not to irradiate such materials with a neutron beam. Accordingly, in various embodiments, the diagnostic system  100  is configured to identify instances of potentially excessive radiation and to use alternative methods of examination. For example, in various embodiments, the processing unit  150  is configured to perform a scout examination of the object  102  (e.g., of the sub-portion  104 ) with the secondary detection system  120  using a first, lower intensity of neutron beam. Then, the processing unit  150  determines a radioactivity level of emissions from the object  102  corresponding to the first low intensity. The processing unit  150  next determines whether or not to perform a diagnostic examination with the secondary detection system  120  using a second, higher intensity based on the radioactivity level determined using the scout examination. For example, if the radioactivity level from the scout scan exceeds a predetermined threshold, the object  102  may be determined as having a significant or substantial risk of excessive radiation, and the object  102  may be removed from the secondary detection system  120  and examined using a different technique. Accordingly, excessive radiation levels may be avoided. 
     It may further be noted that in various embodiments the processing unit  150  may use additional data in connection with the spectral emission data to help identify substances (e.g., potentially harmful substances such as explosives). For example, in various embodiments, the primary detection system is an x-ray detection system, and the processing unit  150  is configured (e.g., programmed) to acquire spatial data and supplemental data as parts of the initial data acquired via the primary detection system  110 . The processing unit  150  may be configured to use the spatial data to determine the sub-portion  104  of the object  102 , and to use the supplemental data from the primary detection system  110  along with the spectral emission data from the secondary detection system  120  to determine the presence of the substance. For example, the spatial data of the initial data may include a description of locations of potentially hazardous materials defining a volume or cross-sectional area of the object  102 , while the supplemental data of the initial data from the primary detection system  110  may include data describing or corresponding to attenuation of x-rays within the object  102 , which may be utilized by the processing unit  150  in conjunction with the spectral emission data from the secondary detection system  120  to identify the presence of a potentially harmful material such as an explosive. 
     Additionally or alternatively, in various embodiments, the processing unit  150  is configured to determine a shape of the object  102  (e.g., a shape of an item within the sub-portion  104  of the object  102 ) using the initial data from the primary detector system. Further, the processing unit  150  may determine expected spectral data based on the shape, and compare the expected spectral data with the acquired spectral emission data. For example, if a bottle shape is identified within the object  102  (e.g., within the sub-portion  104 ), the processing unit  150  may determine expected spectral data that corresponds to water or other liquids expected to be contained within a bottle. The processing unit  150  may then compare the actually acquired spectral emission data with the expected data, and if the two are different, the contents of the bottle may be identified as suspicious, and further examination performed on the bottle. 
       FIG. 5  provides a flowchart of a method  500  in accordance with various embodiments. The method  500 , for example, may employ or be performed by structures or aspects of various embodiments (e.g., systems and/or methods and/or process flows) discussed herein. In various embodiments, certain steps may be omitted or added, certain steps may be combined, certain steps may be performed concurrently, certain steps may be split into multiple steps, certain steps may be performed in a different order, or certain steps or series of steps may be re-performed in an iterative fashion. In various embodiments, portions, aspects, and/or variations of the method  500  may be able to be used as one or more algorithms to direct hardware (e.g., one or more aspects of the processing unit  150 ) to perform one or more operations described herein. 
     At  502 , initial data is acquired of an object being analyzed with a primary detection system (e.g., primary detection system  110 ). The primary detection system, for example, may be an x-ray or CT system. In the illustrated embodiment, at  504 , both spatial data (e.g., data corresponding to location within the object of potentially hazardous materials) and supplemental data (e.g., data regarding attenuation of the object) are acquired with the primary detection system. 
     At  506 , a sub-portion of the object is determined for further analysis using the initial data. The sub-portion defines or corresponds to a portion of the object that has been identified has having a potential risk for having one or more designated substances (e.g., explosives). The size, shape, and/or location of the sub-portion may be determined in various embodiments using spatial data of the initial data. After identification of the sub-portion, the object may be transferred to a secondary detection system (e.g, secondary detection system  120 ). If no potentially hazardous materials are identified, the object may be approved for further processing or distribution without being analyzed by the secondary detection system. 
     At  508 , a scout examination is performed with the secondary detection system. For example, the secondary detection system may direct a first lower intensity neutron beam toward the object. At  510 , a radioactivity level corresponding to the first low intensity is determined. At  512 , it is determined whether or not to perform a diagnostic examination with the secondary detection system using a second, higher intensity based on the radioactivity level determined using the scout examination. For example, if the radioactivity level exceeds a predetermined threshold, the secondary detection system may not be used for a diagnostic examination. If the secondary detection system is not to be used, the method  500  proceeds to  514 , and an alternative inspection process is performed. If the secondary detection system is to be used, the method  500  proceeds to  516 . 
     At  516 , at least one neutron beam from at least one neutron source (e.g., neutron source  130 ) is directed toward the identified sub-portion of the object. In the illustrated embodiment, at  518 , the at least one neutron beam is focused to a footprint complementary to the sub-portion (e.g., using a source collimator such as source collimator  132 ). 
     At  520 , spectral emission data is acquired from the object via at least one detector (e.g., detector  140 ) of the secondary detection system. At  522 , the presence (or absence) of a substance is determined using the spectral emission data. The presence of the substance may be determined, for example, using determined ratios of materials (e.g., C, N, O) as discussed herein. Depending on the determination at  522 , subsequent processing of the object may be determined. For example, if explosives are identified, the object may be identified as having explosives and appropriately handled. If no explosives are identified, the object may be passed along to the next inspection step. 
     It should be noted that the various embodiments may be implemented in hardware, software or a combination thereof. The various embodiments and/or components, for example, the modules, or components and controllers therein, also may be implemented as part of one or more computers or processors. The computer or processor may include a computing device, an input device, a display unit and an interface, for example, for accessing the Internet. The computer or processor may include a microprocessor. The microprocessor may be connected to a communication bus. The computer or processor may also include a memory. The memory may include Random Access Memory (RAM) and Read Only Memory (ROM). The computer or processor further may include a storage device, which may be a hard disk drive or a removable storage drive such as a solid-state drive, optical disk drive, and the like. The storage device may also be other similar means for loading computer programs or other instructions into the computer or processor. 
     As used herein, the term “computer” or “module” may include any processor-based or microprocessor-based system including systems using microcontrollers, reduced instruction set computers (RISC), ASICs, logic circuits, and any other circuit or processor capable of executing the functions described herein. The above examples are exemplary only, and are thus not intended to limit in any way the definition and/or meaning of the term “computer”. 
     The computer or processor executes a set of instructions that are stored in one or more storage elements, in order to process input data. The storage elements may also store data or other information as desired or needed. The storage element may be in the form of an information source or a physical memory element within a processing machine. 
     The set of instructions may include various commands that instruct the computer or processor as a processing machine to perform specific operations such as the methods and processes of the various embodiments. The set of instructions may be in the form of a software program. The software may be in various forms such as system software or application software and which may be embodied as a tangible and non-transitory computer readable medium. Further, the software may be in the form of a collection of separate programs or modules, a program module within a larger program or a portion of a program module. The software also may include modular programming in the form of object-oriented programming. The processing of input data by the processing machine may be in response to operator commands, or in response to results of previous processing, or in response to a request made by another processing machine. 
     As used herein, a structure, limitation, or element that is “configured to” perform a task or operation is particularly structurally formed, constructed, or adapted in a manner corresponding to the task or operation. For purposes of clarity and the avoidance of doubt, an object that is merely capable of being modified to perform the task or operation is not “configured to” perform the task or operation as used herein. Instead, the use of “configured to” as used herein denotes structural adaptations or characteristics, and denotes structural requirements of any structure, limitation, or element that is described as being “configured to” perform the task or operation. For example, a processing unit, processor, or computer that is “configured to” perform a task or operation may be understood as being particularly structured to perform the task or operation (e.g., having one or more programs or instructions stored thereon or used in conjunction therewith tailored or intended to perform the task or operation, and/or having an arrangement of processing circuitry tailored or intended to perform the task or operation). For the purposes of clarity and the avoidance of doubt, a general purpose computer (which may become “configured to” perform the task or operation if appropriately programmed) is not “configured to” perform a task or operation unless or until specifically programmed or structurally modified to perform the task or operation. 
     As used herein, the terms “software” and “firmware” are interchangeable, and include any computer program stored in memory for execution by a computer, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above memory types are exemplary only, and are thus not limiting as to the types of memory usable for storage of a computer program. 
     It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the various embodiments without departing from their scope. While the dimensions and types of materials described herein are intended to define the parameters of the various embodiments, they are by no means limiting and are merely exemplary. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the various embodiments should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112(f) unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure. 
     This written description uses examples to disclose the various embodiments, including the best mode, and also to enable any person skilled in the art to practice the various embodiments, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the various embodiments is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if the examples have structural elements that do not differ from the literal language of the claims, or the examples include equivalent structural elements with insubstantial differences from the literal languages of the claims.