BR112023016847B1 - SYSTEMS AND METHODS FOR ELIMINATION OF CROSSTALK IN SCANNING SYSTEMS WITH MULTIPLE X-RAY SOURCES - Google Patents

Abstract

SYSTEMS AND METHODS FOR ELIMINATION OF CROSS-TALK IN SCANNING SYSTEMS WITH MULTIPLE X-RAY SOURCES. This descriptive report describes a system for eliminating X-ray crosstalk between a plurality of X-ray scanning systems and passive radiation detectors. The system includes a frequency generator for generating a common operating frequency, a high energy X-ray source or scanning system coupled to the frequency generator for receiving the common operating frequency and configured to modify the pulse repetition frequency of the high energy X-ray source or scanning system to synchronize with the common operating frequency, and a low energy X-ray scanning system and/or passive radiation detection system coupled to the frequency generator for receiving the common operating frequency and having a processing module configured to remove data associated with the common operating frequency at a time instant if the high energy X-ray source or scanning system has emitted X-rays at the time instant.

Description

CROSS-REFERENCE

[001] This application is based primarily on U.S. Provisional Patent Application No. 63/152,721, entitled “Systems and Methods for Eliminating Cross-Talk Signals in One or More Scanning Systems Having Multiple X-Ray Sources,” filed Feb. 23, 2021, which is incorporated herein by full reference.

FIELD

[002] This specification relates generally to the field of X-ray scanning systems. More specifically, this specification provides systems and methods for eliminating unwanted interference, often referred to as crosstalk, between co-located X-ray scanners, X-ray systems, nearby passive radiation portal monitors, or any system with multiple X-ray sources.

FUNDAMENTALS

[003] Many conventional X-ray scanning systems include one or more low-energy (LE) X-ray scanning systems with operating energies ranging from 120 KeV to 750 KeV. These systems typically generate scan images using a time-multiplexed detection method, where X-ray data is continuously collected throughout the duration of a scan. In addition, conventional X-ray scanning systems may include one or more passive Gamma/Neutron Radiation Portal Monitors (RPM) that also capture data continuously—recording background data when the scanning zone is vacated and recording live data when the object under investigation passes through the detection panel.

[004] In some X-ray system operational scenarios, such as portal-based systems, gantry-based systems, or mobile systems, one or more high-energy (HE) X-ray transmission scanning systems are configured to operate in proximity to, but independently of, the LE X-ray scanning system (backscatter system) and RPM scanning systems. Alternatively, the HE X-ray scanning system is directly coupled to a LE X-ray backscatter or RPM scanning subsystem as part of a "co-located" product.

[005] Typically, HE X-ray scanning systems comprise X-ray sources, such as a cyclic particle accelerator (Betatron) or a linear particle accelerator (LINAC), with operating energies ranging from 750KeV to 10MeV. The detectors employed in both LE X-ray backscatter systems and RPMs are sensitive to these higher energy X-rays. As a result, for both HE and LE X-ray scanning units and RPM subsystems, operating in dose proximity, such as a physical separation of less than 1000 meters, there is a high probability of high energy X-rays being observed in the low energy backscatter image or contributing to the signal measured in an RPM subsystem. HE X-ray-based scanning platforms are typically operated in a pulsed mode, with each X-ray pulse having a duration of approximately 4 microseconds (μs). Additionally, HE X-ray sources such as LINACs can operate at pulse repetition frequencies up to several kilohertz. For example, the sources can operate at 1 kHz, which would result in a high-energy X-ray pulse every 1 ms.

[006] As a result of this HE X-ray pulse, closely located LE X-ray backscatter and RPM subsystems may record an undesirable contribution to their intrinsic measurement signal, resulting in corrupted data, incorrectly calculated results, and/or image degradation. Specifically, backscatter imaging systems, operating with a typical data capture window time per pixel of 10 microseconds, may display one illuminated pixel or a series of bright pixels, depending on the decay characteristics of the backscatter detector material and the data acquisition configuration. Similarly, RPM systems may detect a higher than expected signal count, which may breach a defined intensity threshold for alarm.

[007] In cases where there are only a few HE X-ray transmission systems located in close proximity to the dose of the LE X-ray backscatter and RPM subsystems, and if the HE X-ray dose per pulse or pulse intensity is high, then conventional "above threshold" pulse removal or filtering techniques may be employed to identify the unwanted signal and remove the data from the resulting image or intensity calculation. This can be handled without knowledge or consideration of the timing properties of the X-ray system.

[008] In cases where there are multiple HE X-ray transmission systems located at various distances relative to and/or in close proximity to the LE X-ray and/or RPM imaging subsystems, possibly operating at different X-ray dose outputs through dynamic dose modulation techniques or low-dose "custom" imaging methodologies, then the detected unwanted crosstalk signal(s) may become indistinguishable from that expected from a LE X-ray backscatter or RPM imaging subsystem. At the same time, if each HE X-ray transmission system were pulsing asynchronously at a different pulse repetition frequency (PRF), this would result in a large number of unwanted interference patterns being received by the X-ray detector(s) and/or LE RPM, significantly increasing the difficulty with which the unwanted signal can be removed and, as a result, reducing the overall detection efficiency of the LE RPM and X-ray imaging subsystem(s). Unfortunately, in these cases, an "above threshold" pulse removal or filtering technique applied to the backscatter and RPM detection data, when the systems are operating in close proximity to one or more high-energy systems, cannot be applied because the magnitude of the crosstalk signal varies depending on which of the potentially multiple HE X-ray transmission systems are firing X-rays, the dose output of each system, and their relative physical locations.

[009] Therefore, there is a need for systems and methods that efficiently remove HE X-ray interference or crosstalk signals generated by one or more HE X-ray scanning systems from images obtained on LE X-ray backscatter scanning systems and from data captured on RPM imaging subsystems operating in proximity to one or more HE X-ray scanning systems.

[010] There is also a need for systems and methods for removing crosstalk, enabling a LE X-ray backscatter or RPM imaging subsystem to recognize or determine when HE X-ray systems are firing X-rays, so that the LE X-ray backscatter system and/or RPM imaging subsystem can efficiently remove unwanted high-energy signals that, given distance and other attenuating factors, may not appear very different from expected signals.

[011] In addition, there is a need to align the pulse repetition frequency of multiple HE X-ray scanning system sources to a common operating frequency. The resulting alignment of HE X-ray pulses reduces the effective unwanted detection rate and/or the number of crosstalk signal interference patterns in other adjacent imaging systems, ensuring that they maintain minimum detection performance and operational efficiency.

SUMMARY

[012] The following embodiments and aspects thereof are described and illustrated together with systems, tools and methods intended to be exemplary and illustrative, not limitative in scope. The present application describes numerous embodiments.

[013] The present descriptive report describes a system for eliminating X-ray crosstalk between a plurality of X-ray scanning systems having at least one high-energy X-ray source and at least one low-energy X-ray scanning system, the system comprising: a frequency generator configured to generate a common operating frequency; the at least one high-energy X-ray source coupled to the frequency generator, the at least one high-energy X-ray source comprising a first processing module for receiving the common operating frequency and configured to generate a pulse repetition frequency of the at least one high-energy X-ray source to be synchronous with the common operating frequency; and at least one low energy X-ray scanning system coupled to the frequency generator to receive the common operating frequency, the at least one low energy X-ray scanning system comprising a second processing module configured to remove data associated with the common operating frequency at a first time point if at least one high energy X-ray source has emitted X-rays at the first time point. Optionally, the system further comprises at least one radiation portal monitor coupled to the frequency generator to receive the common operating frequency, the at least one radiation portal monitor comprising a third processing module configured to remove data associated with the common operating frequency at a second time point if at least one high energy X-ray system has emitted X-rays at the second time point.

[014] Optionally, the system further comprises a radiation portal monitor (RPM), the RPM comprising a passive radiation detector for detecting and measuring radiation emitted by radioactive materials in the absence of any stimuli, and the RPM being a fixed site scanning system or a portable scanning system.

[015] Optionally, the system further comprises a high energy X-ray scanning system comprising at least one high energy X-ray source, wherein the at least one high energy X-ray source is a linear accelerator and wherein the high energy X-ray scanning system is a fixed location scanning system or a portable scanning system.

[016] Optionally, the system further comprises an X-ray backscatter scanning system, the X-ray backscatter scanning system comprising at least one low energy X-ray source and the low energy X-ray scanning system being a fixed location scanning system or a portable scanning system.

[017] Optionally, the at least one high energy X-ray source is a linear accelerator and the at least one high energy X-ray source is adapted to synchronize a pulse repetition frequency (PRF) of the linear accelerator with the common operating frequency.

[018] Optionally, the at least one high-energy X-ray source and the at least one low-energy X-ray scanning system are located within a predefined distance of each other. Optionally, the predefined distance is 1000 meters or less.

[019] Optionally, at least one high energy X-ray source and at least one RPM system are located within a predefined distance of each other. Optionally, the predefined distance is 1000 meters or less.

[020] Optionally, the at least one high energy X-ray source comprises transmission system linear accelerator control and data capture electronics and data distribution hardware.

[021] Optionally, the at least one low energy X-ray source comprises data distribution hardware and backscatter system data capture electronics.

[022] This specification also describes a method for eliminating crosstalk between a plurality of X-ray scanning systems having at least one high-energy X-ray source and at least one low-energy X-ray system, the method comprising: using a frequency generator to generate a common operating frequency; communicating the common operating frequency to at least one high-energy X-ray source; synchronizing the pulse repetition frequency of the high-energy X-ray source with the common operating frequency; communicating the common operating frequency to at least one low-energy X-ray scanning system; and using the common operating frequency to remove crosstalk data associated with at least one high-energy X-ray source from scanning data captured by at least one low-energy X-ray system.

[023] Optionally, the method further comprises communicating the common operating frequency to at least one passive radiation detection system. Optionally, the method further comprises using the common operating frequency to remove crosstalk data associated with at least one high energy X-ray source from scanning data captured by at least one passive radiation detection system. Optionally, the at least one high energy X-ray scanning system and the at least one passive radiation detection system are located within a predefined distance of each other. Optionally, the predefined distance is 1000 meters or less.

[024] Optionally, the method further comprises synthesizing individual high-energy X-ray pulse repetition frequency values that are synchronized with integer and non-integer divisions of the common operating frequency.

[025] Optionally, the method further comprises removing unwanted signal associated with crosstalk data corresponding to the common operating frequency of an image generated by a low energy X-ray scanning system comprising at least one low energy X-ray source.

[026] Optionally, the at least one high-energy X-ray source comprises a linear accelerator.

[027] Optionally, at least one low-energy X-ray source is integrated into an X-ray backscatter scanning system.

[028] Optionally, at least one high-energy X-ray source and at least one low-energy X-ray source are located within a predefined distance of each other. Optionally, the predefined distance is 1000 meters or less.

[029] Optionally, the method further comprises modulating the pulse repetition frequency of the at least one high energy X-ray source in order to accommodate at least one of a varying speed of an object being scanned as it passes through a portal system or a speed of the at least one high energy X-ray source moving along the tracks of a gantry system.

[030] In some embodiments, the present specification also describes a system for eliminating X-ray crosstalk between a plurality of X-ray scanning systems having at least one high energy X-ray source and at least one low energy X-ray scanning system or RPM, the system comprising: a frequency generator configured to generate a common operating frequency; the at least one high energy X-ray source coupled to the frequency generator to receive the common operating frequency, the at least one high energy X-ray source comprising a first processing module configured to modify a pulse repetition frequency of the at least one high energy X-ray source to synchronize with the common operating frequency; and at least one low energy X-ray scanning system coupled to the master frequency generator to receive the common operating frequency, the at least one low energy X-ray system comprising a second processing module configured to remove data associated with crosstalk interference received at a first time instant if at least one high energy X-ray source has emitted X-rays at the first time instant.

[031] Optionally, the system further comprises at least one passive radiation detector coupled to the frequency generator, wherein the at least one passive radiation detector is configured to receive the common operating frequency and wherein the at least one passive radiation detector comprises a third processing module configured to remove data associated with the common operating frequency at a second time point if at least one high energy X-ray system has emitted X-rays at the second time point.

[032] Optionally, the system comprises a Radiation Portal Monitor (RPM), the RPM comprising the passive radiation detector and the RPM being a fixed site scanning system or a portable scanning system.

[033] Optionally, the system further comprises a high energy X-ray scanning system comprising at least one high energy X-ray source, wherein the at least one high energy X-ray source is a linear accelerator and wherein the high energy X-ray scanning system is a fixed location scanning system or a portable scanning system.

[034] Optionally, the system further comprises an X-ray backscatter scanning system, the X-ray backscatter scanning system comprising at least one low energy X-ray source and the low energy X-ray scanning system being a fixed location scanning system or a portable scanning system.

[035] Optionally, the at least one high energy X-ray source is a linear accelerator and wherein the at least one high energy X-ray source is adapted to synchronize a pulse repetition frequency (PRF) of the linear accelerator with the common operating frequency.

[036] Optionally, the common operating frequency is used to mitigate X-ray crosstalk in the X-ray backscatter scanning system. Optionally, the common operating frequency is used to mitigate X-ray crosstalk in the RPM.

[037] Optionally, at least one high-energy X-ray source and at least one low-energy X-ray scanning system are located within a predefined distance of each other. Optionally, the predefined distance is 1000 meters or less.

[038] Optionally, at least one high energy X-ray scanning system and at least one RPM system are located within a predefined distance of each other.

[039] Optionally, the default distance is 1000 meters or less.

[040] Optionally, at least one high energy X-ray scanning system and at least one low energy X-ray scanning system are coupled to the main frequency generator using any one or a combination of electrical, fiber optic, or wireless communication systems.

[041] Optionally, at least one high energy X-ray scanning system and at least one RPM system are coupled to the master frequency generator using any one or a combination of electrical, fiber optic, or wireless communication systems.

[042] Optionally, the at least one high energy X-ray source comprises the transmission system linear accelerator control and data capture electronics and data distribution hardware.

[043] Optionally, at least one low energy X-ray scanning system comprises data distribution hardware and backscatter system data capture electronics.

[044] Optionally, the at least one RPM system comprises data distribution hardware and RPM system data capture electronics.

[045] In some embodiments, the present disclosure describes a method for eliminating crosstalk between a plurality of X-ray scanning systems having at least one high-energy X-ray source and at least one low-energy X-ray scanning system, the method comprising: using a frequency generator to generate a common operating frequency; communicating the common operating frequency to the at least one high-energy X-ray source; synchronizing the pulse repetition frequency of the high-energy X-ray source with the common operating frequency; communicating the common operating frequency to the at least one low-energy X-ray scanning system; and using the common operating frequency to remove crosstalk data associated with the at least one high-energy X-ray source from scan data captured by the at least one low-energy X-ray system.

[046] Optionally, the method further comprises modulating the pulse repetition frequency of the at least one high energy X-ray source in order to accommodate different imaging scenarios, such as the varying speed of the object being scanned as it passes through a Portal System, or the speed of the high energy X-ray source moving along the tracks of a Gantry System.

[047] Optionally, said communication is carried out via fiber optic cables.

[048] Optionally, the method further comprises communicating the common operating frequency to at least one passive radiation detection system.

[049] Optionally, the method further comprises using the common operating frequency to remove crosstalk data associated with at least one high energy X-ray source from scan data captured by at least one passive radiation detection system.

[050] Optionally, at least one high-energy X-ray scanning system and at least one passive radiation detection system are located within a predefined distance of each other. Optionally, the predefined distance is 1000 meters or less.

[051] Optionally, the method further comprises synthesizing individual high-energy X-ray pulse repetition frequency values that are synchronized with integer and non-integer divisions of the common operating frequency.

[052] Optionally, the method further comprises removing unwanted signal associated with crosstalk data corresponding to the common operating frequency of an image generated by a low energy X-ray scanning system comprising at least one low energy X-ray source.

[053] Optionally, the at least one high energy X-ray source comprises a linear accelerator.

[054] Optionally, at least one low-energy X-ray source is integrated into an X-ray backscatter scanning system.

[055] Optionally, at least one high-energy X-ray source and at least one low-energy X-ray source are located within a predefined distance of each other. Optionally, the predefined distance is 1000 meters or less.

[056] The above-mentioned embodiments and other embodiments of this descriptive report shall be described in greater depth in the drawings and in the detailed description provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

[057] These and other features and advantages of the present specification will be further appreciated as they become better understood with reference to the following detailed description when considered in connection with the accompanying drawings: Fig. 1A is a block diagram of a crosstalk removal system in accordance with one embodiment of the present specification; Fig. 1B illustrates an exemplary LINAC-based high-energy X-ray cargo inspection system that may be used with the methods and systems described herein in one embodiment; Fig. 1C illustrates an exemplary low-energy X-ray backscatter cargo inspection system that may be used with the methods and systems described herein in one embodiment; Fig. 1D is a top view schematic representation of the inspection system shown in Fig. 1C; 1E illustrates an example of an X-ray backscatter system 150 that may be employed beneath a vehicle for under-chassis inspection, which may be used with the methods and systems described herein in one embodiment; FIG. 1F illustrates another view of the X-ray backscatter system 150 shown in FIG. 1E; FIG. 1G shows a view of a co-located fixed-site X-ray imaging system that combines both high-energy transmission and low-energy backscatter imaging within the same inspection platform, which may be used with the methods and systems described herein in one embodiment; FIG. 1H shows a view of a mobile X-ray scanning system that combines a high-energy transmission imaging system, a low-energy backscatter imaging system, and a passive radiation detection system within the same inspection platform that can be used with the methods and systems described herein in one embodiment; FIG. 1I shows a self-contained fixed-site passive neutron/gamma radiation portal monitor (RPM) solution that can be deployed in close proximity to a high-energy or low-energy X-ray imaging system; FIG. 2A illustrates a first schematic implementation of a crosstalk removal system in accordance with one embodiment of the present specification; FIG. 2B is a schematic representation of a second implementation of a crosstalk removal system in accordance with one embodiment of the present specification; 2C is a schematic representation of a third implementation of a crosstalk removal system, according to an embodiment of the present disclosure; FIG. 3A provides a visual representation of the relationship between multiple individual high-energy X-ray source pulse repetition frequencies and a common operating frequency, according to an embodiment of the present disclosure; FIG. 3B provides a visual representation of the synchronization of multiple individual high-energy X-ray source pulse repetition frequencies differentiated with respect to a common operating frequency, according to an embodiment of the present disclosure; FIG. 4A shows a first scan image obtained by a low-energy backscatter X-ray inspection system located in proximity to a plurality of high-energy transmission X-ray inspection systems; 4B shows a second scanning image obtained by a low-energy backscatter X-ray inspection system located in proximity to a plurality of high-energy X-ray transmission inspection systems; FIG. 5 illustrates a backscatter signal captured by a low-energy backscatter X-ray scanning system located in proximity to a high-energy X-ray scanning system; FIG. 6A illustrates an exemplary system deployment scenario, according to one embodiment of the present disclosure; FIG. 6B illustrates another exemplary system deployment scenario, according to one embodiment of the present disclosure; and FIG. 7 is a flowchart of a plurality of exemplary steps of a method of eliminating crosstalk between a plurality of X-ray scanning systems, according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

[058] In one embodiment, the present disclosure provides a system and method for removing X-ray crosstalk between high-energy X-ray scanning platforms, such as linear accelerator X-ray (LINAC)-based scanning systems, and low-energy X-ray backscatter scanning systems or radiation portal monitors (RPMs). In various embodiments, the RPMs comprise passive radiation detector equipment designed for the detection and measurement of radiation emitted by radioactive materials in the absence of any stimuli.

[059] The present specification is directed to multiple embodiments. The following specification is provided to enable one skilled in the art to practice the invention. The language used in this specification should not be construed as a general negation of any specific embodiment or used to limit the claims beyond the meaning of the terms used therein. The general principles set forth herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Furthermore, the terminology and phraseology used are for the purpose of describing exemplary embodiments and are not to be construed as limiting. Accordingly, the present invention should be given the broadest scope encompassing numerous alternatives, modifications, and equivalents consistent with the principles and features disclosed. For purposes 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.

[060] In the description and claims of the application, each of the words "comprises," "includes," and "has," and forms thereof, are not necessarily limited to members in a list with which the words may be associated. It should be noted here that any feature or component described in association with a specific embodiment may be used and implemented with any other embodiment, unless clearly indicated otherwise.

[061] As used herein, the indefinite articles "a" and "an" mean "at least one" or "one or more" unless the context clearly indicates otherwise.

[062] In various embodiments, the system, particularly each of the modules, components or generators described herein, includes at least one processor capable of processing programmatic instructions, having a memory capable of storing programmatic instructions and employing software comprised of a plurality of programmatic instructions for executing the processes described herein. In various embodiments, a computing device may be employed to receive and process data signals and image data and may include an input/output controller, at least one communication interface and a system memory. The system memory includes at least one random access memory (RAM) and at least one read-only memory (ROM). These elements are in communication with a central processing unit (CPU) to enable operation of the computing device. In various embodiments, the computing device may be a conventional stand-alone computer or, alternatively, the functions of the computing device may be distributed across a network of multiple computer systems and architectures. In embodiments, the computing device is capable of executing programmatic instructions. In some embodiments, the execution of a plurality of sequences of instructions or programmatic codes, which are stored in one or more non-volatile memories, enabling or causing the CPU of the computing device to execute or enable various functions, processes, and algorithms, such as, for example, performing image reconstruction for display on a screen. In alternative embodiments, hard-wired circuits may be used in place of, or in combination with, software instructions for implementing the systems processes and methods described in this application. In some embodiments, one or more programmable embedded microcontrollers and FPGA (Field Programmable Gate Array)-based circuit boards may be used in place of, or in combination with, software instructions for implementing the systems processes and methods described in this application. Thus, the systems and methods described are not limited to any specific combination of hardware and software.

[063] It should further be appreciated that each device may have wireless and/or wired receivers and transmitters capable of sending and transmitting data, at least one processor capable of processing programmatic instructions, memory capable of storing programmatic instructions, and software comprising a plurality of programmatic instructions for executing the processes described herein.

[064] As used herein, the term "crosstalk" refers to the unwanted detection, in a first system (such as a low-energy backscatter X-ray system or RPM imaging subsystem), of X-ray signals generated by a second system (such as a high-energy LINAC system).

[065] A low-energy (LE) X-ray scanning system is defined as an X-ray scanning system with an X-ray source operating at energies ranging from 120 KeV to 750 KeV. A high-energy (HE) X-ray scanning system is defined as an X-ray scanning system with an X-ray source operating at energies ranging from 750 KeV to 10 MeV.

[066] It should further be appreciated that, in a preferred embodiment, the presently described inventions are only implemented when more than 1 HE X-ray source is operated within 1000 meters of a LE X-ray source and/or RPM imaging subsystem and where the HE X-ray sources are pulsing asynchronously, have different X-ray dose outputs, or implement low-dose "custom" imaging methodologies.

[067] Fig. 1A is a block diagram of a crosstalk removal system 101, according to an embodiment of the present disclosure. The system 101 comprises a master pulse frequency generator 102 that, in some embodiments, is configured to generate a common operating frequency and synchronize a plurality of LINAC-based high-energy X-ray inspection systems 104 (1 through n) to the common operating frequency. The master pulse frequency generator 102 is further configured to communicate the common operating frequency to a plurality of low-energy X-ray backscatter systems 106 (1 through n) and, optionally, a plurality of RPM imaging subsystems 107 (1 through n) for removing X-ray crosstalk. Thus, in embodiments, the plurality of LINAC-based high-energy X-ray inspection systems 104 (1 through n), the plurality of low-energy X-ray backscatter systems 106 (1 through n), and the plurality of RPM imaging subsystems 107 (1 through n) are coupled (utilizing any one or a combination of electrical, fiber optic, or wireless communication systems) to the master pulse frequency generator 102 and configured to receive the common operating frequency.

[068] In embodiments, a range of LINAC pulse repetition frequencies (PRFs) may be generated based on the common operating frequency. Thus, each of the range of LINAC PRFs is synchronized to the common operating frequency. In some embodiments, each plurality of LINAC-based high energy X-ray inspection systems 104 (1-n) includes a processing module configured to modify or generate a PRF of each plurality of high energy X-ray inspection systems in order to synchronize to the common operating frequency. In embodiments, an electronic subsystem of the LINAC (of each of the high energy X-ray inspection systems 104 (1-n)) is configured to determine whether the common operating frequency should be received in order to synchronize the PRF. Consequently, each of the X-ray sources has an independent operating processing module adapted to establish a set of pulse frequencies and, separate from them, is in data communication with a single frequency generator configured to generate a common operating frequency.

[069] It should be appreciated that, in various embodiments, the master pulse frequency generator 102 is physically separate or distinct from a frequency generator that is typically intrinsic and integrated into the LINAC of each of the plurality of LINAC-based high energy X-ray inspection systems 104 (1 through n).

[070] In some embodiments, each plurality of low energy X-ray backscatter systems 106 (1 to n) includes a processing module configured to remove data associated with the common operating frequency at a time instant, T, if any of the high energy X-ray inspection systems has emitted X-rays at the time instant, T.

[071] In some embodiments, each plurality of RPM imaging subsystems (1 to n) includes a processing module configured to remove data associated with the common operating frequency at a time instant, t, if any of the high energy X-ray systems has emitted X-rays at the time instant, t.

[072] The systems and methods of this specification can be used to remove crosstalk from backscatter, RPM, and multi-energy X-ray inspection systems such as those disclosed in United States Patent Nos. 7,505,556; 7,218,704; 7,099,434; 9,841,386; 7,593,506; 7,400,701; 7,551,715; 7,924,979; 7,551,718; 8,345,819; 8,824,632; 8532,823; 8,884,236; 8,903,045; 9,146,201; 9,535,019; 9,285,488; 9,659,343; 9,958,569; 9,841,386; 8,325,871; 8,993,970; and 7,555,099, all of which are incorporated herein by reference. In various embodiments, the systems and methods of this specification may be employed in static/fixed and mobile scanning systems/solutions and in wired or wireless configurations.

[073] Fig. 1B illustrates an exemplary LINAC-based high-energy X-ray cargo inspection system that may be used with the methods and systems described herein. As shown, the cargo inspection system 130 comprises a high-energy radiation source 105 for irradiating an object under inspection 110 with a vertically divergent fan beam of radiation 115. The high-energy radiation source 105 may be, but is not limited to, a linear accelerator (LINAC) or Betatron. In embodiments, the LINAC or any other source provides a radiation dose sufficient for imaging containers and cargo. In one embodiment, the energy and dose output of the LINAC or any other source range, respectively, from 750keV to 10MeV and from 0.07 Gy/min to 15 Gy/min.

[074] The choice of source type, its intensity and energy output depends on the sensitivity of the detectors, the radiographic charge density in the space between the source and the detectors, radiation safety considerations and operational requirements such as inspection speed. One skilled in the art would appreciate the factors that need to be considered for selection of a radiation source type depending on the inspection requirements. In one embodiment, where the object under inspection 110 is a large container or car that highly attenuates the X-ray beam, the radiation may be from an X-ray source operating at an energy ranging from approximately 750 keV to 10 MeV or more. In one embodiment, the object under inspection 110 may be a vehicle, truck, railcar or other container for transporting cargo, passenger baggage or general belongings.

[075] The cargo inspection system 130 further comprises a detector array 120, preferably positioned behind the object under inspection 110 and used for detecting radiation transmitted through the object under inspection 110. The detectors 120 may be formed by a stack of crystals that generate analog signals when X-rays are incident upon them, with the signal intensity proportional to the amount of beam attenuation at the object under inspection 110. In one embodiment, the X-ray beam detector array consists of a linear array of solid state crystal diode type detectors. A typical array uses scintillating cadmium tungstate crystals to absorb X-rays transmitted through the object under inspection 110 and to convert the absorbed X-rays into visible light photons. Crystals such as bismuth sprout, sodium iodide or other suitable crystals may alternatively be used as known to one of skill in the art. The crystals may be directly coupled to a suitable detector, such as a photodiode or photomultiplier. The detector photodiodes may be arranged linearly, whereby unity gain devices provide advantages over photomultipliers in terms of operating range, linearity, and detector-detector matching. In another embodiment, an area detector is used as an alternative to linear array detectors. Such an area detector could be a scintillating strip, such as cesium iodide or other materials known in the art, viewed by a suitable camera or optically coupled to a charge-coupled device (CCD).

[076] It would be apparent to those skilled in the art that the cargo inspection system 130 shown in Fig. 1B is but one example of an inspection system employing high energy X-ray sources, such as, but not limited to, a LINAC or Betatron. The present disclosure provides a system and method for removing crosstalk between a plurality of different system configurations employing high energy X-ray sources, low energy X-ray sources, and passive radiation detection monitors.

[077] Scatter imaging, in which X-rays are scattered by a material (typically in a generally backward direction), offers several unique inspection capabilities and operational features. Scatter imaging allows images to be obtained even when the imaged object is accessible from only one side. Furthermore, since the scatter signal falls off very rapidly with increasing depth into the object, backscatter images effectively represent a "slice" of the object's feature from the side closest to the X-ray source, thereby reducing the image clutter problems that can confound transmission images. The Compton effect, which dominates X-ray scattering in the low-energy range (120 keV to 750 keV), dominates the interaction of X-rays with dense, low-atomic-number (low-Z) materials. Narcotic drugs tend to produce bright signatures in a backscatter image, as do organic explosives, making backscatter imaging a useful imaging modality for bomb or drug detection. Finally, the requirements for aligning the X-ray beam with detectors or collimation devices are less stringent than for transmission imaging, thus enabling rapid deployment in a wide range of inspection scenarios.

[078] Fig. 1C illustrates an example of a low-energy X-ray backscatter cargo inspection system. Fig. 1C is an exploded perspective view of a mobile X-ray backscatter cargo inspection system deployed on a truck capable of traveling on the road and scanning an enclosure, such as a vehicle or cargo container, while one or both of the inspection system and the enclosure are in motion. Fig. 1D is a top view schematic representation of the inspection system shown in Fig. 1C. With reference to Figs. 1C and 1D, the X-ray backscatter detectors 100 are mounted on a mobile platform 10, or carriage, typically capable of traveling over a large object to be inspected, such as a vehicle or cargo container 12. The carriage 10 is characterized by an enclosure 14, presently the body of a van, shown in Fig. 1C in a cross-sectional view, to allow representation of other components of the inspection system. The carriage 10 may incorporate many alternative embodiments, including but not limited to gasoline, diesel, electric, propane, battery, fuel cell or hydrogen powered motor vehicles (including vans, trucks or the like), tracked vehicles, sleds, trailers, cranes or other equipment capable of being set in motion, preferably self-propelled, as well as including railed and electrically powered vehicles.

[079] Contained within the housing 14 of the transport 10 is a source 30 including the X-ray tube 32 (shown in Fig. 1D) and the cutter 34. The source energies are typically in the range of 120 keV to 750 keV, so the cutter 34 may be smaller than that employed in systems in which higher energy X-rays are employed. The cutter 34 may be a rotating perforated hub, or a wheel with transmission spokes, or any number of means known in the art for generating flying spot beams that typically lie in a plane approximately orthogonal to the direction 20 of motion. The X-ray tube 32 shown in Fig. 1D, by way of example, is a panoramic style X-ray tube capable of generating wide angle beams and, further, may be rotatable to permit scanning on both sides of the carriage 10. The rotatable rim 34, with apertures 36 and 38, emits a pencil beam 24, thereby permitting inspection of objects possibly on both sides of the carriage 10, herein referred to as "bilateral" inspection. However, all sources are encompassed within the scope of the present invention when employed in the manner described herein. The X-ray source 30 and detectors 100 may be oriented to permit scanning of the "driver's side," "passenger's side," or both sides of the carriage simultaneously. Various means are known in the art for mechanically or electronically scanning a beam of penetrating radiation, including, for example, the rotating cutter wheel 34 depicted in Fig. 1D, or electronic scanning is described in detail, for example, in U.S. Pat. No. 6,421,420, issued July 16, 2002, which is incorporated herein by reference.

[080] Backscatter detector modules 100 are carried by carriage 10 and typically enclosed within closure body 14 and hidden from view from outside carriage 10. They may also be carried outside carriage 10 for particular applications within the scope of the present invention. Detector modules 100 contain detectors for detecting penetrating radiation from source 30 that has interacted with and scattered from the contents of inspected object 12. The scattering source may be characterized as anomalous to the nature of the person or item being scanned. Thus, a person carrying explosives may be detected based on locally enhanced X-ray scattering. A specified characteristic of the scattering, such as a particular location or arrangement relative to the inspected object, may be ensured in order to determine threat levels of the object.

[081] Inspection of the object 12 may be conducted by an operator disposed within the carriage 10 or, alternatively, by an operator disposed remotely. For inspection, the object 12 may be held in a stationary condition, with the carriage 10 traversing the object along direction 20 (forward or backward); alternatively, the inspection may be conducted while the carriage 10 and the inspected object 12 are in motion. In yet another mode, referred to as a "portal mode", the inspection system is stationary and the inspection object is transported by the inspection system. When the inspection object is a person, the person may be required to pass through the carriage 10 slowly, preferably in both directions, so that both sides of the person may be subjected to inspection. In a "stationary mode", both the inspection system and the object being scanned are stationary, and a vehicle-mounted X-ray scanning method, configured as part of the inspection system itself, is employed to create in effect horizontal and vertical scanning to generate a backscattered X-ray image. Such methods may include the use of an x-y translation stage, electronically steered X-ray sources (as described, for example, in U.S. Pat. No. 6,421,420), or other means.

[082] The relative motion of the transport 10 and the object 12 may be carefully controlled or may be monitored by the sensor 18 employing any of a variety of sensing methods, such as radar, ultrasonic, or optical, including laser detection or LIDAR, all provided as examples only, in order to detect the relative speed of the transport 10 relative to the object 12. A signal provided by the sensor 18 is employed by the controller 40 in one or more of the following embodiments: the speed of the vehicle may be regulated or, alternatively, the pixel recording may be corrected to compensate for vehicle speed anomalies in order to produce distortion-free, aspect-ratio-free backscatter X-ray images. Relevant techniques include, but are not limited to: the use of high-precision speed sensing devices to accurately measure vehicle speed at low ranges (0.5 to 10 miles per hour); the use of low speed (0.5 to 10 miles per hour) electronic and/or software-based motors and/or transmission controls; and the use of custom vehicle drive train gear designs that simultaneously produce low vehicle scanning speed while maintaining the ability to provide viable speed ranges up to at least 55 miles per hour. In one embodiment, the conveyor speed 10 does not affect scan quality since the scan data capture rate is fixed by a rotational speed of the chipper wheel 34. Thus, in embodiments, for a backscatter X-ray inspection system as described herein, pixel registration is corrected to remove any unwanted/corrupted data from the scan data using the common operating frequency signal as described herein. The common operating frequency signal is used to identify the corrupted data, and then the artifact is removed using one or more predefined image processing algorithms in a processing module as described in this document.

[083] Fig. 1E illustrates an example of an X-ray backscatter system 150 that may be deployed beneath a vehicle for under-chassis inspection. Fig. 1F illustrates another view of the X-ray backscatter system 150 shown in Fig. 1E. Inspection of the underside of vehicles by a portable X-ray backscatter system presents special problems. The road clearance of cars is no more than 8 inches and may be as small as 6 inches. Fixed inspection systems, such as portals, may place a detector on the ground or the detector may be placed on the ground. An X-ray source (such as, for example, an X-ray tube) employed in the under-chassis backscatter system 150 may consist of an electromagnetic scanner 152 that directs an electron beam through an anode. The electromagnetic scanner 152 is driven by the electronic module 154. The X-rays generated by the source are collimated by a linear array of apertures 156 that span, for example, 30 inches of the underside in one pass. Detectors 158 are mounted on each side of the X-ray tube so as to detect X-rays backscattered from the vehicle 162. Power supplies, pulse and image processors may be appropriately mounted. The chassis 164 of the backscatter inspection system 150 on wheels 166 may be adapted to be maneuvered under the vehicle 162 by motor or manual control.

[084] Fig. 1G is a view of a co-located fixed-site X-ray imaging system 170 that combines high-energy transmission and low-energy backscatter imaging on the same inspection platform. Fig. 1H shows a view of a mobile X-ray scanning system 175 that combines a high-energy transmission imaging system 176, a low-energy backscatter imaging system 177, and a passive radiation detection system 178 within the same inspection platform. FIG. 1I shows a self-contained fixed-site passive neutron/gamma radiation portal monitor solution 180 (RPM imaging subsystem) that may be deployed in proximity to a high-energy or low-energy X-ray imaging system.

[085] Referring again to Fig. 1A, in embodiments, the plurality of LINAC-based high-energy X-ray inspection systems 104 are programmed to emit X-rays synchronized with the common operating frequency generated by the master pulse frequency generator 102. Limiting the number of high-energy X-ray frequencies generated by a common operating frequency restricts to unity the number of different interference patterns that may occur in the plurality of low-energy X-ray or RPM inspection systems 106,107. This also results in simplification of the crosstalk removal process due to the presence of a single known interference pattern.

[086] The common operating frequency signal generated by the master pulse frequency generator 102 is also communicated to each plurality of low energy X-ray backscatter inspection systems 106, while, using image processing algorithms, a significant portion of crosstalk can be eliminated or removed from the inspection images produced by each of the backscatter inspection systems 106 when high energy X-rays are present. By limiting the crosstalk reduction to only when high energy X-rays are present, unnecessary processing and/or corruption of backscatter scan images is eliminated, thereby avoiding degradation of image performance and reduced detection capabilities.

[087] In embodiments, in order to ensure that a generic image quality remains smooth and without sharp edges/distortions, adjacent signal values are averaged. This method successfully removes all crosstalk present within low power inspection systems. However, such crosstalk removal may result in deterioration of image quality in some regions of the produced images. For example, in the case of a vehicle being scanned by a backscatter inspection system, anything on the vehicle that generates a specific signal (equal to an interference pulse) may not be captured in the scanned image. However, since the frequency of interference pulses is low when compared to a data capture rate of the backscatter system, the interference pulses appear infrequently and therefore the data loss is not significant. In an exemplary backscatter system with a sampling rate of lüms per line at 400Hz pps, a corresponding LINAC operates for a period of 2μs every 25ms, impacting only one or two pixels. Therefore, the data loss is equal to a maximum of 2 pixels per 2500 data points (or 0.08%).

[088] In one embodiment, the master pulse frequency generator 102 becomes operational whenever two or more of the high energy X-ray inspection systems 104 and low energy X-ray inspection systems 106 located within a predefined distance of each other are operational. In embodiments where two or more of the high energy X-ray inspection systems 104 and low energy X-ray inspection systems 106 are co-located and are part of a screening system, the predefined distance between the systems 104, 106 may be as short as 5 meters (15 feet). In embodiments, where two or more of the high energy X-ray inspection systems 104 and low energy X-ray inspection systems 106 are operating in series with respect to each other, but are decoupled (i.e., the scanning tunnels of said systems are aligned, but with a gap between them), the preset distance may be greater than approximately 33 meters or 1000 feet. In embodiments, where two or more of the high energy X-ray inspection systems 104 and low energy X-ray inspection systems 106 are decoupled, offset, and operating within shielding walls, the preset distance may be less than 50 m (150 feet). Furthermore, in embodiments, the preset distance may increase based on a dose output of the high energy X-ray inspection system 104. It should be noted that the aforementioned distances are exemplary and apply to portal-based systems. In the case of high penetration gantry systems, the distances may be even greater in these configurations.

[089] In some embodiments, the fiber optic cables are configured to enable communication between the master pulse frequency generator 102, the LINAC-based high-energy X-ray inspection systems 104, the low-energy X-ray backscatter systems 106, and the RPM subsystems 107. As is known, fiber optic transmission offers greater bandwidth capabilities, long-distance operation, increased safety, and improved resistance to electromagnetic interference compared to other transmission media. In embodiments, because the individual X-ray inspection systems may be operating from different power sources and may be located at varying distances ranging up to meters from each other (as described previously), the use of fiber optic communications provides for continuous and rapid operation of the system 101.

[090] It should be appreciated that inspection systems such as, but not limited to, inspection systems with drive-through scanning capability or occupied driver's cabin scanning capability require sophisticated crosstalk removal techniques.

[091] Fig. 2A is a first schematic implementation diagram of a crosstalk removal system 200a, according to an embodiment of the present disclosure. The system 200a comprises a BEAT_MASTER 202 (also referred to as a 'common operating frequency generation unit') that includes an ND-CONCENTRATOR 204 configured to operate as a master frequency generator together with a plurality of ND-FOCUSES 206 to provide a common operating frequency with the remainder of the system 200a. In one embodiment, the ND-CONCENTRATOR 204 is configured as a programmable embedded microcontroller and FPGA-based circuit board that utilizes on-board crystal oscillators for generating timing signals. In one embodiment, the ND-FOCUS 206 is an electronic board configured to communicate via fiber optic cable and operate as a source/master and sink/slave of the common operating frequency.

[092] The system 200a also comprises two high energy X-ray inspection systems 208 and 210, each of which, in one embodiment, comprises an ND-FOCUS 206 configured to receive the common operating frequency and configured to connect to one or more ND-CONCENTRATORS 204, which, in turn, are configured to operate as the transmission system control and data capture electronics and data distribution hardware. Additionally, system 200a comprises three low-energy X-ray-based backscatter X-ray inspection systems 212, 214, and 216, each of which, in one embodiment, comprises an ND-FOCUS 206 configured to receive the common operating frequency and to connect to one or more eDAQ (electronic data acquisition) backscatter signal processing subsystems 218. System 200a further comprises two Radiation Portal Monitor (RPM) inspection systems 219 and 220, each of which, in one embodiment, comprises an ND-FOCUS 206 configured to receive the common operating frequency and to connect to RPM detector processing electronics 221.

[093] Additionally, a plurality of communication systems 222 allow systems 208, 210, 212, 214, 216, 219, and 220 to be physically separated up to and beyond a distance of 1000 meters as needed, providing low latency communication of the common operating frequency. In various embodiments, communication systems 222 include any one or a combination of electrical, fiber optic, or wireless communication systems.

[094] The common operating frequency generated by the common operating frequency generation unit, also referred to as the master pulse frequency generator above or a beat master, 202 is communicated to each of the high energy X-ray transmission inspection systems 208, 210 such that they are programmed to emit X-rays that are synchronous with the common operating frequency generated by the master pulse frequency generator. The common operating frequency generated by the beat master 202 is also communicated to each of the low energy X-ray backscatter inspection systems 212, 214, 216, allowing the presence of crosstalk to be alleviated from inspection images produced by the backscatter systems 212, 214, 216 via the backscatter system's data acquisition electronics 218 and image processing algorithms.

[095] The common operating frequency generated by beat master 202 is also communicated to each of RPM subsystems 219 and 220, allowing the presence of crosstalk to be mitigated using techniques such as suppression to remove the contribution of the crosstalk signal to the measured RPM data. Thus, system 200a is configured to have a separate beat master 202 that communicates a common operating frequency to two nearby high-energy X-ray transmission systems 208, 210, three nearby low-energy X-ray backscatter systems 212, 214, 216, and two nearby RPM systems 219, 220.

[096] Fig. 2B is a schematic representation of a second implementation of a crosstalk removal system 200b, according to an embodiment of the present disclosure. The system 200b is configured to have the high energy X-ray transmission system 208 and the low energy X-ray backscatter system 212 "co-located", meaning that the two systems 208, 212 are integrated into a single screening solution. System 208 is the only high energy X-ray transmission system within the overall site and as such the BEAT_MASTER 202 is integrated “inside” the high energy X-ray transmission platform 208. System 200b also features three separate dose proximity inspection stations comprising a low energy X-ray backscatter unit 214 and two RPM units 219, 220 that receive the common operating frequency signal from the beat master 202 in the co-located system. Other elements such as the ND-CONCENTRATOR 204, ND-FOCUS 206, eDAQ (data acquisition electronics) backscatter signal processing subsystems 218, RPM detector processing electronics 221, and communication systems 222 were discussed previously with reference to system 200a.

[097] Fig. 2C is a schematic representation of a third implementation of a crosstalk removal system 200c, in accordance with an embodiment of the present disclosure. The system 200c is configured to have a first high energy transmission system 208 proximate to a second high energy X-ray transmission system 210 proximate to a stand-alone RPM unit 219. In embodiments, a first beat master 202a and a second beat master 202b are employed, both integrated within each of the respective high energy X-ray transmission systems 208, 210. If the first high energy X-ray transmission system 208 is operational, then it assumes the role of master frequency generator and is configured to communicate the common operating frequency to the second high energy X-ray transmission system 210 and the RPM unit 219 via the ND-FOCUS boards 206 and communication systems 222 (such as, but not limited to, fiber optic cable connections). However, if the first high energy X-ray transmission system 208 is not energized or operational, then the second high energy X-ray transmission system 210 assumes the role of master frequency generator and is configured to communicate the common operating frequency to the first high energy X-ray transmission system 208 via the ND-FOCUS boards 206 and communication systems 222. In this case, the RPM unit 219 continues to receive the common operating frequency when either or both of the first and second high energy X-ray transmission systems 208, 210 are operational. Other elements, such as the ND-CONCENTRATOR 204 and RPM detector processing electronics 221 were discussed previously with reference to system 200a.

[098] Fig. 3A provides a visual representation of the relationship between multiple different individual high energy X-ray source pulse repetition frequencies and a common operating frequency, in accordance with one embodiment of the present disclosure. Fig. 3A shows a timing diagram 300 of the relationship between the common operating frequency and any individual high energy X-ray source pulse repetition frequency. In embodiments, a maximum common operating frequency signal 301 is generated within a beat master, as previously described. A first plurality of timing diagrams 302 show exemplary LINAC PRF (Pulse Repetition Frequency) setpoints that may be established or achieved through integer division of the maximum common operating frequency. A second plurality of timing diagrams 303 show exemplary LINAC PRF setpoints that may be established or achieved through non-integer division. In embodiments, the frequencies/signals/operation of an individual X-ray source are not modified within the X-ray source itself. In embodiments, the frequency of the signal that is sent to the X-ray source, or LINAC, that triggers the generation of the X-ray pulse (or X-ray burst) is modified. On each rising edge of the signal, the X-ray source will generate an X-ray pulse. The frequency of the trigger signal is the Pulse Repetition Frequency (PRF).

[099] Fig. 3B provides a visual representation of the synchronization of multiple different individual high-energy X-ray source pulse repetition frequencies to a common operating frequency, in accordance with one embodiment of the present disclosure. In embodiments, a common operating frequency signal 301 is generated within the beat master 305, as previously described. The common operating frequency 301 is communicated to at least one processing module 310 that is associated with at least one X-ray source, or LINAC, thereby generating a PRF trigger signal 315. This signal is then communicated to the LINAC 320, resulting in an X-ray pulse output 325. Thus, in embodiments, the processing module that is coupled to each high energy X-ray source receives the common operating frequency and then generates a LINAC trigger timing pulse generation frequency signal that is synchronized with the common operating frequency (LINAC_PRF_TRIGGER_SIGNAL). The interval between LINAC trigger times will vary depending on the required X-ray pulse repetition frequency of the system being employed.

[0100] Fig. 4A shows a scan image 400a obtained by a low energy backscatter X-ray inspection system located in proximity to a plurality of high energy X-ray transmission inspection systems, each individual high energy X-ray transmission system being pulsing asynchronously and a significant impact of crosstalk image corruption can be seen. The large number of white spot artifacts 402 result from the plurality of interference patterns resulting from the incoherent summation of multiple pulse repetition frequencies of the high energy X-ray sources. While it is possible to remove such data using the techniques described above, the overall quality of the resulting image would be reduced due to the significant number of pixels corrected.

[0101] Fig. 4B shows a scan image 400b obtained by a low energy backscatter X-ray inspection system located in proximity to a plurality of high energy X-ray transmission inspection systems, with each individual high energy X-ray transmission system pulsing in synchronization. The effect of a crosstalk removal algorithm has been disabled from approximately half of image 400b for comparative illustration. As shown, image 400b comprises a first portion 404 and a second portion 406. Second portion 406 illustrates crosstalk due to multiple synchronized high energy transmission systems operating in proximity to the low energy backscatter system from which image 400b is obtained. In embodiments, the crosstalk signal visible in second portion 406 occurs due to interference of operating frequencies of the low and high energy X-ray systems and is dependent on the relative frequency of operation between the systems. The crosstalk in the second portion 406 is visible as a sequence of bright pixels 408, making the image portion 406 unclear and unsuitable for detecting any threatening items that may be present in the object being scanned, although less impacted than when the multiple systems are operating asynchronously (as shown in Fig. 4A). The first portion 404 appears brighter than the second portion 406 as crosstalk due to the multiple high-power transmission systems operating in close proximity has been removed using the systems and methods described herein.

[0102] Fig. 5 illustrates a backscatter signal 504 captured by a low-energy backscatter X-ray scanning system located in proximity to a high-energy X-ray scanning system. As can be seen, the backscatter signal 502 is indicative of an unwanted signal originating from a LINAC-based high-energy X-ray transmission system. Conventional methods that rely on the magnitude of this pulse for removal of unwanted signals cannot be relied upon for mitigation due to the possibility of dose change, changing distances of co-located systems, and the asynchronous operation of multiple high-energy X-ray sources. In embodiments, the use of a common operating frequency distributed to the low power backscatter scanning system and RPM subsystem, in proximity to the high power scanning system, ensures that the crosstalk signal 502 occurs at a known time, thereby reducing the number of interference patterns to a single one and allowing the implementation of mitigation techniques in low power backscatter and RPM systems.

[0103] Fig. 6A illustrates an exemplary system deployment scenario 600a, in accordance with one embodiment of the present disclosure. As shown in Fig. 6A, a self-contained low-energy X-ray backscatter system 605 is co-located in proximity to a high-energy X-ray transmission system 610 and a low-energy X-ray backscatter system 630. In deployment scenario 600, a beat master (i.e., a master pulse generator unit) resides within the high-energy X-ray transmission system 610, and the common operating frequency (generated by the beat master) is distributed to the nearby and co-located low-energy X-ray backscatter system 630, as well as to the adjacent self-contained low-energy X-ray backscatter system 605.

[0104] Fig. 6B illustrates another exemplary system 600b deployment scenario, in accordance with an embodiment of the present disclosure. As shown in Fig. 6B, six high-energy X-ray transmission systems 611, 612, 613, 614, 615, and 616 (hereinafter, collectively referred to as “611-616”) and four low-energy X-ray backscatter systems 621, 622, 623, and 624 (hereinafter, collectively referred to as “621-624”) are located in close proximity. Consequently, there is interference from each of the six high-energy X-ray transmission systems 611-616 to each of the four low-energy X-ray backscatter systems 621-624. In some embodiments, the six high energy X-ray transmission systems 611-616 are also capable of operating at a very low X-ray dose or in “Cab-Scan” mode to support driver-occupied scanning. Each of the six high energy X-ray transmission systems 611-616 requires synchronous source triggering to avoid interference with adjacent and nearby low energy X-ray backscatter systems. Thus, in some embodiments, a beat master 635 (i.e., a master pulse generating unit) is provided in a building adjacent to deployment scenario 600b to generate a common operating frequency, along with a single ND_FOCUS (i.e., auxiliary unit) for each of the six high energy X-ray transmission systems 611-616 and each of the four low energy X-ray backscatter systems 621-624. This causes high energy X-ray transmission systems 611-616 to be employed at the common operating frequency and low energy X-ray backscatter systems 621-624 to receive data to cancel out the interfering signal at the common operating frequency (received via, for example, fiber optic cables).

[0105] Fig. 7 is a flowchart of a plurality of exemplary steps of a method for eliminating crosstalk between a plurality of X-ray scanning systems, according to some embodiments of the present disclosure. In step 702, a master frequency generator is configured to generate a common operating frequency. In step 704, the generated common operating frequency is communicated to at least one high-energy X-ray scanning system. In some embodiments, the at least one high-energy X-ray scanning system consists of a LINAC-based X-ray scanning platform. In various embodiments, the at least one high-energy X-ray scanning system is fixed or mobile/portable.

[0106] In step 706, a pulse repetition frequency of an X-ray source of the at least one high-energy X-ray scanning system is synchronized with the common operating frequency. In embodiments, individual high-energy X-ray PRF (Pulse Repetition Frequency) values are synthesized such that they are synchronized with integer and non-integer divisions of the common operating frequency.

[0107] In some embodiments, the pulse repetition frequency of the X-ray source of the at least one high-energy X-ray scanning system is modulated in order to accommodate different imaging/scanning scenarios, such as, for example, varying a speed of the object being scanned as it passes through a high-energy X-ray scanning system configured as a portal system or varying the speed of the X-ray source moving along the tracks of a high-energy X-ray scanning system configured as a gantry system.

[0108] In step 708, the generated common operating frequency is communicated to at least one low-energy X-ray scanning system and/or at least one passive radiation detection system. In some embodiments, the at least one high-energy X-ray scanning system and the at least one low-energy X-ray scanning system are located within a predefined distance of each other. In some embodiments, the at least one high-energy X-ray scanning system and the at least one passive radiation detection system are located within a predefined distance of each other. In some embodiments, the at least one high-energy X-ray scanning system, the at least one low-energy X-ray scanning system, and the at least one passive radiation detection system are located within a predefined distance of each other. Several additional exemplary deployment scenarios have been described with reference to Figs. 2A, 2B, 2C, 6A, and 6B. In some modalities, the default distance is less than 1000 meters.

[0109] In some embodiments, the at least one low energy X-ray scanning system is an X-ray backscatter scanning system. In some embodiments, the at least one passive radiation detection system is a Radiation Portal Monitor (RPM). In various embodiments, the generated common operating frequency is communicated using any one or a combination of electrical, fiber optic, or wireless communication systems.

[0110] In step 710, the common operating frequency is used to remove crosstalk data associated with at least one high-energy X-ray scanning system from scan data captured by at least one low-energy X-ray scanning system and/or at least one passive radiation detection system. In some embodiments, unwanted signal associated with crosstalk data corresponding to the common operating frequency is removed from an image generated by the low-energy X-ray scanning system. In some embodiments, crosstalk data corresponding to the common operating frequency is removed from scan data captured from the at least one passive radiation detection system.

[0111] The above examples are merely illustrative of the many applications of the system and method of the present specification. Although only a few embodiments of the present invention have been described herein, it should be understood that the present invention may be embodied in many other specific formats without departing from the spirit or scope of the invention. Therefore, the present examples and embodiments should be considered as illustrative and not restrictive, and the invention may be modified within the scope of the appended claims.

Claims (24)

1. A system for eliminating X-ray crosstalk between a plurality of X-ray scanning systems having at least one high energy X-ray source and at least one low energy X-ray scanning system, the system comprising: a frequency generator configured to generate a common operating frequency; the at least one high energy X-ray source coupled to the frequency generator, the at least one high energy X-ray source comprising a first processing module for receiving the common operating frequency and configured to generate a pulse repetition frequency from the at least one high energy X-ray source to be synchronous with the common operating frequency; and the at least one low energy X-ray scanning system coupled to the frequency generator to receive the common operating frequency, the at least one low energy X-ray scanning system comprising a second processing module configured to remove data associated with the common operating frequency at a first time instant if the at least one high energy X-ray source has emitted X-rays at the first time instant. 2. The system of claim 1 further comprising at least one radiation portal monitor coupled to the frequency generator for receiving the common operating frequency and wherein the at least one radiation portal monitor comprises a third processing module configured to remove data associated with the common operating frequency at a second time point if the at least one high energy X-ray system has emitted X-rays at the second time point. 3. The system of claim 2, further comprising a radiation portal monitor (RPM), the RPM comprising a passive radiation detector for detecting and measuring radiation emitted by radioactive materials in the absence of any stimuli, and the RPM being a fixed site scanning system or a portable scanning system. 4. The system of claim 1 further comprising a high energy X-ray scanning system comprising at least one high energy X-ray source, wherein the at least one high energy X-ray source is a linear accelerator and wherein the high energy X-ray scanning system is a fixed location scanning system or a portable scanning system. 5. The system of claim 1 further comprising an X-ray backscatter scanning system, wherein the X-ray backscatter scanning system comprises at least one low energy X-ray source and wherein the low energy X-ray scanning system is a fixed location scanning system or a portable scanning system. 6. The system of claim 1, wherein the at least one high-energy X-ray source is a linear accelerator and wherein the at least one high-energy X-ray source is adapted for synchronizing a pulse repetition frequency (PRF) of the linear accelerator with the common operating frequency. 7. The system of claim 1 wherein the at least one high-energy X-ray source and the at least one low-energy X-ray scanning system are located within a predefined distance of each other. 8. The system of claim 7, wherein the preset distance is 1000 meters or less. 9. The system of claim 1 wherein the at least one high energy X-ray source and the at least one RPM system are located within a predefined distance of each other. 10. The system of claim 9, wherein the preset distance is 1000 meters or less. 11. The system of claim 1 wherein the at least one high energy X-ray source comprises linear accelerator control, transmission system, and data capture electronics and data distribution hardware. 12. The system of claim 1, wherein the at least one low energy X-ray source comprises data distribution hardware and backscatter system data capture electronics. 13. A method for eliminating crosstalk between a plurality of X-ray scanning systems having at least one high energy X-ray source and at least one low energy X-ray system, the method comprising: utilizing a frequency generator to generate a common operating frequency; communicating the common operating frequency to the at least one high energy X-ray source; synchronizing the pulse repetition frequency of the high energy X-ray source with the common operating frequency; communicating the common operating frequency to the at least one low energy X-ray scanning system; and utilizing the common operating frequency to remove crosstalk data associated with the at least one high energy X-ray source from scan data captured by the at least one low energy X-ray system. 14. The method of claim 13, further comprising communicating the operating frequency in common to at least one passive radiation detection system. 15. The method of claim 14, further comprising utilizing the common operating frequency to remove crosstalk data associated with the at least one high energy X-ray source from scan data captured by the at least one passive radiation detection system. 16. The method of claim 14, wherein the at least one high-energy X-ray scanning system and the at least one passive radiation detection system are located within a predefined distance of each other. 17. The method of claim 16, wherein the preset distance is 1000 meters or less. 18. The method of claim 13, further comprising synthesizing individual high-energy X-ray pulse repetition frequency values that are synchronized with integer and non-integer divisions of the common operating frequency. 19. The method of claim 13, further comprising removing unwanted signal associated with crosstalk data corresponding to the common operating frequency of an image generated by a low-energy X-ray scanning system comprising at least one low-energy X-ray source. 20. The method of claim 13, wherein the at least one high-energy X-ray source comprises a linear accelerator. 21. The method of claim 13, wherein the at least one low-energy X-ray source is integrated into an X-ray backscatter scanning system. 22. The method of claim 13, wherein the at least one high-energy X-ray source and the at least one low-energy X-ray source are located within a predefined distance of each other. 23. The method of claim 22, wherein the preset distance is 1000 meters or less. 24. The method of claim 13, further comprising modulating the pulse repetition frequency of the at least one high energy X-ray source to accommodate at least one of a varying speed of an object being scanned as it passes through a portal system or a speed of the at least one high energy X-ray source moving along the tracks of a gantry system.