WO2010114518A1 - Système de balayage pour automobile - Google Patents

Système de balayage pour automobile Download PDF

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Publication number
WO2010114518A1
WO2010114518A1 PCT/US2009/038903 US2009038903W WO2010114518A1 WO 2010114518 A1 WO2010114518 A1 WO 2010114518A1 US 2009038903 W US2009038903 W US 2009038903W WO 2010114518 A1 WO2010114518 A1 WO 2010114518A1
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Prior art keywords
ray
energy
automobile
filter
radiation
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PCT/US2009/038903
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English (en)
Inventor
Steven W. Smith
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Spectrum San Diego, Inc.
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Priority to PCT/US2009/038903 priority Critical patent/WO2010114518A1/fr
Publication of WO2010114518A1 publication Critical patent/WO2010114518A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V5/00—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity
    • G01V5/20—Detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects
    • G01V5/22—Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays
    • G01V5/224—Multiple energy techniques using one type of radiation, e.g. X-rays of different energies
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V5/00—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity
    • G01V5/20—Detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects
    • G01V5/22—Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays
    • G01V5/232—Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays having relative motion between the source, detector and object other than by conveyor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/30—Accessories, mechanical or electrical features
    • G01N2223/313—Accessories, mechanical or electrical features filters, rotating filter disc
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/40—Imaging
    • G01N2223/423—Imaging multispectral imaging-multiple energy imaging

Definitions

  • This invention relates to the x-ray imaging of automobiles to detect explosives, hidden persons, contraband, and other security threats.
  • the present Invention overcomes these limitations of the prior art by providing an apparatus and method capable of acquiring dual-energy transmission x-ray images of automobiles passing through a security checkpoint.
  • a linescan x-ray imaging system is provided in an archway configuration, whereby the automobile being examined drives slowly through a fan beam of x-ray radiation, with the driver and passengers remaining safely within the vehicle.
  • High-energy and low-energy x-ray spectra are alternately selected for the fan beam of radiation, allowing x-ray images of the automobile to be acquired at two separate x- ray energies.
  • the switching spectra are formed by operating the x-ray source at approximately 120KV, and switching the beam filtration material between 0.25" thick copper and 0.030" thick bismuth sheets, or similar elements.
  • Detection of the fan beam of radiation is accomplished with a linear array of detectors, such as Cadmium Tungstate or Caesium Iodide crystals mounted on photodiodes.
  • the dual-energy images are converted to a steel- suppressed image and calibrated for measuring the thickness of organic material.
  • the mass of each organic object in the automobile is subsequently calculated from the calibrated image by summing the pixel values over the projection of the object in the image.
  • Organic masses greater than a specified threshold trigger an alert to security personnel for secondary inspection.
  • the present Invention operates with only a few microRem of radiation exposure to the driver and passengers of the automobile. This radiation exposure is regarded as trivial under radiation protection standards and appropriate for general purpose security examination.
  • One aspect of the present Invention adjusts the output intensity of the x-ray source to match the speed of the automobile, thereby maintaining the highest image quality for the allowable radiation dose.
  • FIG. 1 is an overall schematic depiction in accordance with the present invention.
  • FIG. 2 is a depiction in accordance with the present invention.
  • FIG. 3 is a depiction in accordance with the imaging geometry of the present invention.
  • FIG. 4 is a depiction in accordance with the detector of the present invention.
  • FIG. 5 is a depiction in accordance with one aspect of the present invention.
  • FIG. 6A and FIG 6B are graphs in accordance with the present invention.
  • FIG. 7A and FIG 7B are graphs in accordance with the present invention.
  • FIG. 8 is a graph in accordance with the present invention.
  • FIG. 9 is a flowchart in accordance with one aspect of the present invention. DETAILED DESCRIPTION OF THE INVENTION
  • FIG. 1 shows the overall general operation of the Invention.
  • the scanning apparatus 100 is contained within an archway 101, about ten feet high and ten feet wide, spanning across the roadway 201.
  • the automobile being examined 202 approaches the scanning apparatus and is stopped by a first gate-arm 204.
  • the first gate-arm 204 is raised, allowing the automobile 202 to slowly drive through the archway 101 until stopped by the second gate-arm 205, at a position 203 after the archway 101.
  • An x-ray assembly 103 is mounted at the top of the archway 101, directing a fan beam of x-rays downward to a linear array detector assembly 104, resting on the roadway 201.
  • Automobile motion sensors 106 provide an electronic output of the speed of the automobile 202, 203 as it passes through the archway 101.
  • Support members 102 hold the archway 101 upright and prevent persons on foot from entering the x-ray examination area.
  • the x-ray image data generated by the scanning apparatus 101 is received by computer system 105 in an operator area 206.
  • the computer system 105 processes the data to generate an image on the computer system display monitor, showing objects concealed within the automobile.
  • FIG. 2 shows a more detailed view of the archway 100 of the Invention.
  • X-ray assembly 103 comprises an x-ray source 110 emitting x-rays 125 downward to a linear slit collimator 113, resulting in a fan beam of x-rays 114 passing to the linear array detector 104.
  • a rotating chopper wheel 112 is affixed in the x-ray beam next to the x-ray source 110 and turned by a motor 111.
  • the outlines of a large automobile being screened 202 and a person 207 are shown for size reference.
  • FIG. 3 shows a more detailed description of the x-ray imaging apparatus of the Invention.
  • the x-ray source 110 is of conventional construction, such as having a fixed anode, a 0.065 " x 0.065" focal spot, and operating at about 120 KV and 2 ma.
  • an x-ray tube operating at a selected KV results in an internal electron energy that is numerically the same. For example, it is equivalent to state that an x-ray tube operates at 120 KV, and that it operates with an electron energy of 120 keV.
  • X-ray shielding in the design of x-ray source 110 blocks the x-ray beam 125 from all directions except downward, where it illuminates the linear slit collimator 113.
  • Linear slit collimator 113 consists of a sheet of x- ray opaque material 121, such as lead or tantalum, with an opening 122 to permit the passage of x-rays.
  • the opening 122 is approximately 42 inches long and 0.1 inches wide, and positioned about 2.5 feet below the x-ray source 110.
  • the fan x-ray beam 114 exits the linear slit collimator 113 and propagates to the linear array detector 104, located about 7.5 feet below.
  • the x-ray beam 125 passes through the rotating chopper wheel 112 immediately upon exiting the x-ray source 110.
  • the rotating chopper wheel 112 consists of a copper disk approximately 14 inches in diameter and 0.25" thick.
  • a plurality of bismuth plates 115 are affixed to the rotating chopper wheel 112 at uniformly spaced angular increments. In a preferred embodiment, four to ten such bismuth plates 115 are used, with a thickness of about 0.030", with the copper under each bismuth plate removed. This results in the x-ray beam 125 passing through either 0.25" copper or 0.030" bismuth at any one instant, as the rotating chopper wheel 112 is rotated around a vertical axis 116.
  • Rotation of the rotating chopper wheel 112 is accomplished by an electric motor 111.
  • the rate of rotation is adjusted to provide alternating exposures of about three milliseconds through the copper beam filter followed by three milliseconds through the bismuth beam filter. In a preferred embodiment having six bismuth plates 115 this corresponds to a rotation rate of 1,250 rpm.
  • the combination of the x-ray assembly 103 and the linear slit collimator 113 forms a fan beam of x-rays 114, wherein the x-ray spectrum alternates every three milliseconds between 120 KV with 0.25"copper filtration and 120 KV with 0.030" bismuth filtration.
  • the fan beam of x-rays 114 strikes the active detection area 130 of the linear array detector 104.
  • the active detection area 130 is about 0.6" wide, slightly wider than the 0.595" total width of the fan x-ray beam 114.
  • the linear array detector 104 is folded into a "U" shape. As known in the art, such folded detectors provide the same operation as flat linear array detectors, but have the advantage of being more compact.
  • the active detection area 130 comprises a plurality of detector elements. In one preferred embodiment, 320 detector elements are used with each measuring about 0.6" by 0.6".
  • Each detector element can be formed by one of the known detection techniques, such as scintillators mounted on photodiodes; scintillators mounted on photomuliplier tubes; or direct detection using germanium, silicon, or cadmium zinc telluride devices.
  • each detector element is a 0.6" x 0.6" x 0.150" thick scintillator crystal mounted on a 0.39" x 0.39" photodiode.
  • the scintiallation crystal may be either CsI(Ti) or CdWO4.
  • a white reflective paint is applied to all exposed surfaces of the crystal to maximize light transfer from the scintillator to the photodiode. Readout electronics of such detectors are known in the art.
  • the alignment of the linear slit collimator 113 is critical. Specifically, the focal spot of the x-ray source 110, the opening 122, and the active detection area 130, must remain coplanar. This alignment problem is aggravated by the automobile 202 being required to drive over the linear array detector 104, which may move the detector relative to the other assemblies. Accordingly, in one preferred embodiment a method and apparatus is provided to automatically align the linear slit collimator 113.
  • Linear actuators 120 are affixed to the extreme ends of the linear slit collimator 113 as shown in Fig. 3. Under software control, the first linear actuator moves the first end of the linear slit collimator 121 a distance of about 0.5" in three seconds.
  • FIG. 4 shows the cross-sectional construction of a preferred embodiment of the linear array detector 104.
  • a primary goal of this design is to protect the electronic components forming the active detection area 130 from mechanical damage, while providing a smooth structure that the automobile 202 can drive over.
  • the linear array detector 104 is formed from a solid metal base 131 having a triangular cross-section.
  • the altitude 141 of this triangular cross-section is approximately 0.8", while the width dimension of the base 140 is about eight inches.
  • a recessed channel 133 in the base measures about 0.65' by 0.65" in cross-section, providing a mounting location for the electronic components forming the active detection area 130.
  • a 0.125" thick rubber sheet 132 is affixed over the metal base 131 to exclude dirt and other contamination from the active detection area 130.
  • a preferred embodiment of the present Invention overcomes this limitation by adjusting the intensity of the x-ray beam to match the speed of the automobile.
  • Figure 5 explains this aspect of the Invention.
  • the automobile being inspected 202 moves through the scanning apparatus 100 at some speed, in the range of 1 mph to 20 mph.
  • Automobile motion sensors 106 measure this speed.
  • the automobile motion sensors 106 are one or more video cameras mounted at a location where they can view the automobile 202 as it passes through the scanning apparatus 100.
  • the video signal 150 from the camera therefore consists of a series of images 160 of the automobile 202, with a second image 162 showing the automobile displaced by a relative amount compared to a first image 161.
  • a digital computer 170 measures this displacement in the two images 161, 162 and calculates the speed of the automobile 202 by dividing the displacement distance by the time between images.
  • Digital computer 170 further calculates a mathematical value corresponding to the reciprocal of the speed of the automobile 202 and routes this signal 180 to a radiation intensity control 403.
  • Radiation intensity control 403 adjusts the intensity of the x-ray beam 114 that impinges on automobile 202 according to methods known in the art, such as by changing the x-ray tube current or by moving various thickness of filtration material into and out of the beam path. The following example will explain this operation using a preferred embodiment of controlling the x-ray tube current.
  • the total radiation exposure received by an occupant of the automobile 202 is proportional to current divided by the speed, and will therefore be the same at all speeds between 1 and 20 mph.
  • 2ma / 20 mph produces the same radiation dose as O.lma / lmph.
  • placing approximately three cm of plastic or other organic matter in the beam path will reduce the beam intensity by a factor of two.
  • the effective radiation dose received by occupants of the automobile is calculated as follows. From standard references known in the art, an x-ray tube operating at 120 KV and 2 ma produces a radiation exposure of 0.009 Roentgen per second at a distance of seven feet, the approximate center of the automobile. The conversion between Roentgen and Rem of effective dose is approximately unity at the x-ray energies used in the Invention. The exposure time for any location in the automobile is 0.006 seconds. This exposure time is broken into two halves, corresponding to the two energies needed to make the dual-energy measurement. During both of these halves, the intensity of the beam is reduced by a factor of about ten by filtration material inserted into the beam, as needed to shape the spectra for dual energy imaging.
  • Dual-energy x-ray imaging has long been used in security applications, for example, airport-type baggage scanners.
  • an x-ray beam passing through an object is reduced in intensity according to:
  • Xo is the incident x-ray intensity
  • Xi is the intensity after passing through a material of thickness, t , and density p.
  • the parameter, ⁇ is the mass attenuation coefficient which depends on both the atomic number of the material and the x-ray energy.
  • Airport-type baggage scanners acquire images at two separate x-ray energies, typically about 40 keV and 80 keV. This is accomplished through the use of energy sensitive detectors having a sandwich structure, such as described in U.S. patent 4,626,688 issued to Barns. Two measurements for each pixel are therefore given by the equations:
  • XLo and XHo are the intensities of the incident low and high-energy x-ray beams, respectively;
  • XLi and XHi are the intensities of the low and high-energy x-ray beams after passing through the material, respectively;
  • p is the density of the material;
  • t is the thickness of the material;
  • ⁇ i and ⁇ h are the mass attenuation coefficients of the material at the low and high energies, respectively.
  • the goal of airport-type baggage scanners is to determine the atomic number of the material, or if one more than one element is present, a weighted or "effective" atomic number. This is accomplished by mathematically calculating a "logarithmic division,” represented here by the variable "LD":
  • the logarithmic division measures the ratio of the high to the low-energy mass attenuation coefficients of the object being examined , which is unique for each element. For instance, carbon has a ratio of about 1.28; aluminum 2.8; and iron 6.2. This allows airport- type baggage scanners to identify different atomic elements and display them in different colors on the display monitor.
  • FIG. 6A shows the mass attenuation coefficients of iron 301, which is equivalent to steel for x-ray interactions, along with water 302, which is representative of organic materials. While the curve for water 302 is relatively flat, the curve for iron drastically increases as the energy becomes lower. For instance, at 40 keV the mass attenuation coefficient of iron is 3.55 cm 2 /gm with a density of 7.1 gm/cm 3 . Using equation (1), a 5 mm thickness of iron will reduce the intensity of this x-ray beam to only 0.000003 of its original intensity.
  • the energy of the low-energy beam cannot be higher than about 90 keV. Discriminating between two different materials, steel and water in the present case, requires that the mass attenuation coefficients of the two materials be significantly different at the energy of the low-energy beam, and relatively similar at the energy of the high-energy beam. In Fig. 6A it can be seen that the two curves 301, 302 converge as the energy becomes greater, making the energy placement of the high-energy beam relatively simple. In particular, the energy of the high-energy beam can be at any energy above about 90 keV. However, to achieve a difference in mass attenuation coefficients, the energy of the low- energy beam must be below about 90 keV.
  • the ratio of the two mass attenuation coefficients is about 4.2; at 80 keV it is 3.3, and at 90 keV it is 2.8. As this ratio becomes lower, the ability of the dual-energy measurement to discriminate between the two materials becomes less.
  • the energy of the low-energy x-beam must be placed in the narrow window of about 70 keV to 90 keV to be functional for the inspection of automobiles. If placed at a lower energy the beam will not be able to penetrate the steel of the automobile. If placed at a higher energy insufficient dual-energy information can be obtained to distinguish steel from organic materials.
  • the techniques of the prior art such as used in airport-type baggage scanners, do not and cannot achieve placement of the low- energy beam in this critical window.
  • the present Invention operates within this narrow window by using specific technique factors for generating the x-ray beam.
  • the low-energy filter material must have a high k-edge energy, such as platinum, gold, mercury, thallium, lead, bismuth, and thorium.
  • the x-ray tube must be operated with an electron energy that is greater than the k- edge energy, but less than the k-edge energy plus about 50 keV. This approximately corresponds to operating the x-ray tube between 100 KV and 150KV.
  • the present invention uses a bismuth filter with the x-ray tube operated at 120KV.
  • the logarithmic subtraction used in baggage scanners provide an incorrect measurement when imaging through overlying steel.
  • Logarithmic subtraction reports the effective atomic number of the combination of the explosive and the overlying metal. That is, the presence of the overlying steel corrupts the measurement. Further, this corruption is extreme since the attenuation of steel is far higher than the attenuation of organic material.
  • the present Invention overcomes these limitations of the prior art by providing an apparatus and method of accurately measuring the mass of organic objects concealed within the metal of an automobile.
  • filtration materials between about 0.25" of copper and 0.030" of bismuth, produces the two spectra shown in Fig. 6B.
  • These filtration materials reduce the intensity of the incident x-ray beam by a factor of about ten, and in the process, optimally shape the spectra for the particular problem of inspecting through steel.
  • the spectrum of the high-energy beam 304 is centered at about 100 keV.
  • the spectrum of the low-energy beam 303 is centered at about 80 keV.
  • the bismuth filter 115 has a sharp discontinuity in its spectral filtration at 90.5 keV, a result of the bismuth k-edge at this energy.
  • X-rays above 90.5 keV are highly attenuated, essentially removing them from the spectrum 303.
  • this effect generates a low-energy beam 303 that is ideally placed in the 70 keV to 90 keV window that is critical for automobile inspection.
  • logarithmic subtraction As opposed to the "logarithmic division” previously described and used in prior art security systems.
  • the mathematics of logarithmic subtraction are explained as follows, using the simplified example of mono-energetic x-ray beams.
  • the following equations represent the high and low-energy beams passing through an object composed of both iron and water:
  • XHo and XLo are the incident intensities of the high and low-energy x-ray beams, respectively;
  • XHi and XLi are the intensities of the x-ray beams after passing through the object;
  • ⁇ , ⁇ hw, ⁇ u, and ⁇ lw are the mass attenuation coefficients of iron and water at the high and low x-ray energies, as denoted by the subscripts;
  • P 1 and p w are the densities of iron and water, respectively.
  • Equation (10) and (11) the parameters k and r are shown to simply be constants that depend on the fixed mass attenuation coefficients and density. Equation (9) shows the goal of the logarithmic subtraction; the thickness of the water can be calculated from the measured values and known constants, irregardless of the thickness of metal present. That is, applying equation (9) to each pixel creates an electronic image where the value of each pixel is the thickness of the water, with the corrupting effect of overlying metal completely removed. [037] The above mathematical analysis assumes that mono-energetic x-ray beams are used, making all of the mass attenuation coefficients a fixed value.
  • each detector element in the active detection area 130 will output a sightly different level of electronic signal as a result in variations in the electronic components.
  • the value of the signal from each detector element is measured and stored with the x-ray beam turned off. All future measurements from the Invention are then modified by subtracting the stored values from the measured value to correct for the detector DC offset.
  • XHi is a measured value of the signal from each detector element for the high-energy beam
  • XLi is a measured value of the signal from each detector element for the low-energy beam
  • XSUM is the value of the signal from each detector element for the sum of the high and low-energy beams expressed as an attenuation in dB
  • XDIF is the value of the signal from each detector element for the difference between the high and low-energy beams expressed as an attenuation in dB.
  • XSUM is the measured attenuation, expressed in dB, of the combination of both the high and the low-energy beams.
  • XDIF if the difference between the measured attenuations of the high and the low-energy beams, also expressed in dB.
  • These five points 331-335 define a curve 330 relating the value of XSUM to XDIF for all thickness of iron in the useful range of the invention.
  • this curve 330 is held in a computer array with indexes 0 to 1400, corresponding to the value of XDIF being 0 to 14 dB.
  • the value of the measured points 331-335 are inserted directly into this array, and the points between determined by a curve fit.
  • This array defines the calibration needed to correct for various thickness of iron in the operational images, and therefore will be referred to as the "Iron Correction Factor array", represented by the notation, ICF[ ]. That is, the ICF[ ] array provides a lookup table that converts any measured value of XDIF into the corresponding value of XSUM that would occur if only iron were being measured.
  • the attenuation of the x-ray beams through water can essentially be represented by a single constant.
  • the calibration procedure of a preferred embodiment determines this constant by taking an image of a 4" thick container of water affixed to a 1/8" thick sheet of iron. The values of XSUM and XDIF for this calibration phantom are measured from the acquired image. The value of the calibration constant, k, is then calculated as:
  • the nominal value of k is 0.358 inches per dB.
  • Each pixel in the image of a scanned automobile represented by a value of XSUM and XDIF, is converted into the thickness of water corresponding to that pixel by:
  • the first step is to acquire a dual-energy x-ray image of the vehicle 191.
  • This step comprises generating x-rays of at least two different energies, directing the x-rays through the automobile, and detecting the x-ray that exit the automobile.
  • the x-ray image acquired in this step resides as digital computer data, consisting of a plurality of pixels, with each pixel consisting of measured data for the at least two different energies.
  • the second step is to calculate a steel suppressed image 192.
  • This step is carried out using the previously described logarithmic subtraction. This step may be carried out analytically, as described in equations (5) - (11). Alternatively, it may be carried out through the use of calibrated lookup tables, such as discussed in conjunction with Fig. 8 and the portion of equation (15) denoted by: " [XSUM - ICF(XDIF)]".
  • the steel suppressed image calculated in this step resided as digital computer data, consisting of a plurality of pixels, with the value of each pixel being immune to the effect of steel in the vehicle.
  • the third step is to calibrate the steel suppressed image 193.
  • this step is carried out multiplying each pixel in the steel suppressed image by a calibration factor, referred to as "k", in equations (14) and (15).
  • k a calibration factor
  • each pixel in the calibrated steel suppressed image is a direct measure of the thickness of water, organic, or other non-steel objects present in the vehicle at the location corresponding to the pixel.
  • the fourth step is to determine object boundaries 194.
  • the goal of this step is to identify groups of pixels in the calibrated steel suppressed image that correspond to each of the water, organic, or other non-steel objects present in the vehicle.
  • this comprises thresholding the image to eliminate all regions that have a measured thickness of less than about one inch.
  • groups of pixels are identified in the image that are connected.
  • computer algorithms known in the art as "blob analysis" are used to further refine the object boundaries of each connected group of pixels to most closely correspond to actual objects contained in the vehicle.
  • the pixels that correspond to each object in the vehicle are identified and reside as digital data in a computer.
  • the fifth step is to calculate the mass of each object from its boundaries and the calibrated image 195.
  • the value of each pixel in the calibrated image, calculated in step 3, is the measured thickness of the corresponding object at that pixel location.
  • the boundaries of each object determined in step 4 provide the projected area of the object.
  • this step 195 comprises calculating the mass of each object by summing the values of all pixels contained within the object boundaries, and multiplying by the assumed density of the object.
  • all organic material is assumed to have the characteristics of water, with the density of 1 gm/cm .
  • the result of this step is a list of masses associated with each object in the vehicle, held as digital data in a computer. The assumption that all organic material has the characteristics of water results in an error that is not significant for the purposes and goals of the Invention.
  • the sixth step is the decision: "Does the mass of any object exceed a threshold?" 196.
  • This step comprises a computer comparing each of the object masses calculated in step five with a predetermined mass threshold.
  • This mass threshold depends on the application where the Invention is being deployed. For example, a border checkpoint may set the threshold to 50 pounds to detect the presence of persons hidden in the vehicle. In comparison, the entrance to the underground parking facility of a skyscraper may set the threshold to 500 pounds to detect car bombs.
  • the seventh step is to trigger an alarm 197, if the answer determined in step six is "yes."
  • this alarm consists of an audible sound in the area where a security officer is stationed, along with a visual presentation on a computer monitor indicating the location in the scanned image where the triggering object is located.
  • the above specific descriptions and embodiments have been made to explain the Invention and those skilled in the art will immediately recognize that other embodiments and modifications are within the scope of the Invention. For instance: The x-ray source may use a fixed or rotating target; operate with other combinations and variations of technique factors; be cooled by air, water, or oil; and other embodiments that are known in the art.
  • the x-ray detector may comprise other scintillation crystals or screens; use photomultiplier tubes, other electron multiplication devices, or other light detection technologies known in the art; be mounted in other configurations to prevent damage to the components; or use other x-ray detectors known in the art.
  • Switching the beam filtration may be done by a linear actuator, flat wheel, cylinder, or other mechanical assembly. Modulation of the intensity of the x-ray beam may be accomplished by varying the x-ray tube beam current, KV, or mechanically placing filters in the beam. Computer calculations may be carried out in alternative ways known in the art to achieve the same goals.
  • the selection of beam filtration materials may extend to elements and compounds that have similar characteristics to those stated for the preferred embodiment of copper and bismuth.
  • copper may be replaced by iron, nickel, zinc, silver, molybdenum, or tin, or combinations of these elements.
  • Bismuth may be replaced by, for instance, platinum, gold, mercury, thallium, lead, bismuth, or thorium, or combinations of these elements.
  • Calibration of the Invention may be accomplished by phantoms constructed of steel instead of iron, since iron and steel are essentially equivalent in x-ray characteristics. Further, calibration of the Invention may be made in thicknesses of organic materials other than water, such as plastics or explosives. Variations in the geometric size of the Invention may be made, such as making it large enough to examine trucks and buses.

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  • Analysing Materials By The Use Of Radiation (AREA)

Abstract

Système d'imagerie à rayons X à double énergie conçu pour détecter des objets dissimulés dans une automobile en mouvement. Le fonctionnement à double énergie s'obtient en utilisant une source de rayons X sous une tension constante comprise de 100 - 150 kV, avec commutation en alternance entre deux filtres de faisceau. Le premier filtre est un élément atomique à énergie de bord de zone k tel que le platine, l'or, le mercure, le thallium, le plomb, le bismuth ou le thorium, fournissant un spectre de basse énergie. Le second filtre fournit un spectre haute énergie par durcissement du faisceau. Les faisceaux basse et haute énergie sont reçus par un détecteur de rayons X. Ce signaux détectés sont traités dans un ordinateur numérique qui crée une image sans acier après suppression de l'acier par soustraction logarithmique. L'intensité du faisceau de rayons X est réglée en tant que réciproque de la vitesse mesurée de l'automobile, ce qui fournit un niveau de rayonnement uniforme indépendamment du mouvement de l'automobile. Ainsi, cette invention permet d'obtenir des images d'objets organiques cachés dans des automobiles en mouvement sans les effets détritiques d'une couverture en acier et du mouvement de l'automobile.
PCT/US2009/038903 2009-03-31 2009-03-31 Système de balayage pour automobile WO2010114518A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3772702A3 (fr) * 2016-02-22 2021-05-19 Rapiscan Systems, Inc. Procédés de traitement des images radiographiques

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0059382B1 (fr) * 1981-02-27 1985-08-14 General Electric Company Filtre rotatif pour appareil à rayons X
US4987581A (en) * 1987-11-19 1991-01-22 Bio-Imaging Research, Inc. Cam-controlled automatic dynamic focusing for computed tomography
US20050084073A1 (en) * 2003-10-15 2005-04-21 Seppi Edward J. Multi-energy x-ray source
US20060140341A1 (en) * 2003-06-20 2006-06-29 James Carver Relocatable x-ray imaging system and method for inspecting commercial vehicles and cargo containers
US7386092B2 (en) * 2003-10-16 2008-06-10 Tsinghua University Containers/vehicle inspection system with adjustable radiation x-ray angle

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0059382B1 (fr) * 1981-02-27 1985-08-14 General Electric Company Filtre rotatif pour appareil à rayons X
US4987581A (en) * 1987-11-19 1991-01-22 Bio-Imaging Research, Inc. Cam-controlled automatic dynamic focusing for computed tomography
US20060140341A1 (en) * 2003-06-20 2006-06-29 James Carver Relocatable x-ray imaging system and method for inspecting commercial vehicles and cargo containers
US20050084073A1 (en) * 2003-10-15 2005-04-21 Seppi Edward J. Multi-energy x-ray source
US7386092B2 (en) * 2003-10-16 2008-06-10 Tsinghua University Containers/vehicle inspection system with adjustable radiation x-ray angle

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3772702A3 (fr) * 2016-02-22 2021-05-19 Rapiscan Systems, Inc. Procédés de traitement des images radiographiques
US11287391B2 (en) 2016-02-22 2022-03-29 Rapiscan Systems, Inc. Systems and methods for detecting threats and contraband in cargo

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