Continuous high speed tomographic imaging system and method
First Claim
1. A continuous, high speed, tomographic imaging apparatus for detecting target objects contained within a moving package comprising:
- a package conveying system for continuously conveying a package along a line of travel between a conveying system input end and a conveying system output end, first, second and third spaced CT scanning stations relatively spaced along said line of travel and positioned between the conveying system input and output ends for scanning said moving package in three different scan planes relatively spaced along said line of travel, each said CT scanning station including a plurality of spaced, stationary X-ray sources all positioned to project X-ray beams in the same scan plane and a stationary detector array positioned in opposed, spaced relationship to said X-ray sources, said detector array including a plurality of stationary, spaced detectors to receive X-ray beams projected from said X-ray sources in said scan plane and to provide CT data output signals which are a function of the received X-ray beams, said first CT scanning station operating in a scan plane which is vertically oriented relative to said line of travel, said second and third CT scanning stations each operating in a scan plane which is transverse to said line of travel, the X-ray sources of said second CT scanning station projecting beams from the right side of said line of travel to the left side thereof and the X-ray sources of said third CT scanning station projecting beams from the left side of said line of travel to the right side thereof, and a processing and analysis assembly connected to receive said detector CT output signals from the detector arrays of said first, second and third CT scanning stations, said processing and analysis assembly operating to analyze said CT data output signals to identify target objects.
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Abstract
The continuous, high speed, tomographic imaging system moves a closed package containing concealed objects continuously along a conveyor belt past three spaced sensing stations. At each sensing station a plurality of X-ray sources each emit a fan beam in the same scan plane which passes through the package to a plurality of detectors opposite to the X-ray sources. One scan is a vertical perpendicular scan plane relative to the direction of travel of the package along the conveyor belt and the remaining two scan planes are horizontal scan planes at right angles and transverse to the direction of travel. One horizontal scan plane is a left to right scan plane while the remaining scan plane is a right to left scan plane. Each detector provides multiple energy outputs (5) for the same data point in a scan slice, and the detector outputs are stored until all three sensing stations have scanned the same cross sectional view of the package in three directions. Scans are sequentially taken as the package moves continuously through the sensing stations and scanned data corresponding to cross sectional views of the package is accumulated. The stored data is calibrated and normalized and then used in a CT algebraic reconstruction technique. This is a multispectral CT reconstruction, where the density of a reconstructed object is determined by the attenuation which it causes in the scanning X-rays while the atomic number of the object is determined from the multiple energy scan output. In a classifier, the density and atomic number are compared to a stored look up table containing density and atomic number identification values for specific objects to be located.
285 Citations
18 Claims
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1. A continuous, high speed, tomographic imaging apparatus for detecting target objects contained within a moving package comprising:
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a package conveying system for continuously conveying a package along a line of travel between a conveying system input end and a conveying system output end, first, second and third spaced CT scanning stations relatively spaced along said line of travel and positioned between the conveying system input and output ends for scanning said moving package in three different scan planes relatively spaced along said line of travel, each said CT scanning station including a plurality of spaced, stationary X-ray sources all positioned to project X-ray beams in the same scan plane and a stationary detector array positioned in opposed, spaced relationship to said X-ray sources, said detector array including a plurality of stationary, spaced detectors to receive X-ray beams projected from said X-ray sources in said scan plane and to provide CT data output signals which are a function of the received X-ray beams, said first CT scanning station operating in a scan plane which is vertically oriented relative to said line of travel, said second and third CT scanning stations each operating in a scan plane which is transverse to said line of travel, the X-ray sources of said second CT scanning station projecting beams from the right side of said line of travel to the left side thereof and the X-ray sources of said third CT scanning station projecting beams from the left side of said line of travel to the right side thereof, and a processing and analysis assembly connected to receive said detector CT output signals from the detector arrays of said first, second and third CT scanning stations, said processing and analysis assembly operating to analyze said CT data output signals to identify target objects. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for detecting a target object within a continuously moving container comprising the steps of:
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CT scanning the container with a plurality of adjacent X-ray projections to obtain a plurality of CT output signals attenuated by the scanned container, using an ART to create a reconstructed image having a plurality of spaced pixels with a defined pixel interval from said CT output signals including low pass filtering attenuated CT output signals from adjacent X-ray projections to remove variations with wavelengths shorter than twice the pixel interval and reconstructuring said image by modeling attenuation in the image area as the sum of smooth basis functions with diameters of at least two pixel intervals. - View Dependent Claims (17, 18)
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Specification