Systems and methods for improved atomic-number based material discrimination
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Publication Number
US-11822041-B2
Publication Date
2023-11-21
Expiration Date
Abstract
The present specification discloses a covert mobile inspection vehicle with a backscatter X-ray scanning system that has an X-ray source and detectors for obtaining a radiographic image of an object outside the vehicle. The systems preferably include at least one sensor for determining a distance from at least one of the detectors to points on the surface of the object being scanned, a processor for processing the obtained radiographic image by using the determined distance of the object to obtain an atomic number of each material contained in the object, and one or more sensors to obtain surveillance data from a predefined area surrounding the vehicle.
Core Innovation
The invention provides an inspection system that includes an X-ray source configured to emit X-ray beams, at least one collimator to generate a fan-beam from the emitted X-ray beams, and a plurality of detectors configured to acquire data representative of a backscatter radiographic image of an object located proximate to the inspection system. A processor processes the backscatter radiographic image data by determining a boundary of each region of the backscatter radiographic image and calculating values indicative of energies of pixels present in each region.
For each region, the processor calculates a function of energies of pixels present in each region and compares an output of the function to a predetermined scale. The predetermined scale is configured such that a first value of the output corresponds to a low Z material and a second value of the output corresponds to a high Z material, thereby enabling material discrimination from region-based pixel energy statistics in the backscatter radiographic image.
In further described implementations, determining a boundary of each region uses a statistical filter to define true region boundaries, and the energies-indicative value and the function of energies are computed from pixel energies using region statistics such as standard deviation and mean, including a product of standard deviation and mean. The region-based processing is further described as using adaptive region based averaging to improve statistics at larger distances, with optional distance-based color coding, while the overall system is described as integrating the backscatter processing with an automated real-time detection processor and multi-modality surveillance sensors.
Claims Coverage
The independent claim covers an inspection system that performs region-based pixel-energy processing on backscatter radiographic images acquired using fan-beam collimation and multiple detectors, and maps a function of pixel-energy statistics to a predetermined low-Z versus high-Z scale. The coverage includes additional limitations in dependent claims refining the energies metric, the energies function, the scaled comparison, and example detector and X-ray source constraints.
Fan-beam backscatter inspection system with multiple detectors
An inspection system comprising an X-ray source configured to emit X-ray beams, at least one collimator to generate a fan-beam from the emitted X-ray beams, a plurality of detectors configured to acquire data representative of a backscatter radiographic image of an object located proximate to the inspection system.
Region boundary determination and pixel energy processing
A processor configured to process the data representative of the backscatter radiographic image by determining a boundary of each region of the backscatter radiographic image, calculating a value indicative of energies of pixels present in each region, and calculating a function of energies of pixels present in each region.
Predetermined low-Z/high-Z scale from function output
The processor compares an output of the function to a predetermined scale wherein a first value of the output corresponds to a low Z material and a second value of the output corresponds to a high Z material.
Standard deviation of pixel energies per region
The value indicative of energies of pixels is the standard deviation of pixel energies present in each region.
Product function of standard deviation and mean energy
The function of energies is a product of the standard deviation and a mean of the energies of pixels present in each region.
Scaled comparison mapping to low-Z versus high-Z
Comparing the output of the function includes comparing the product to a predetermined scale wherein the first output value is low and the second output value is high.
Semiconductor detector material selection
The plurality of detectors comprise at least one semiconductor material selected from CdTe, CdZnTe, HgI, or HPGe.
X-ray tube cathode-anode potential difference range
The X-ray source comprises an X-ray tube with a cathode-anode potential difference in a range of 160 kV to 320 kV.
Overall claim coverage centers on backscatter radiographic inspection using fan-beam collimation and multiple detectors, followed by region boundary determination and computation of pixel-energy statistics to generate a function output that is mapped to a predetermined low-Z versus high-Z material scale. Dependent claims further specify the energies metric, the energies function, and example detector semiconductor materials and an X-ray tube voltage range.
Stated Advantages
Documented Applications
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