X-ray computed tomography (CT) system for detecting thin objects

• US 5,712,926 A
• Filed: 10/20/1994
• Issued: 01/27/1998
• Est. Priority Date: 10/20/1994
• Status: Expired due to Term

• Current Assignee: L-3 Communications Security & Detection Systems, Inc. (Leidos Holdings, Inc.)
• Original Assignee: Lockheed Martin Specialty Components, Inc.
• Inventors: Eberhard, Jeffrey Wayne, Hsiao, Meng-Ling
• Primary Examiner(s): Mancuso, Joseph
• Assistant Examiner(s): DEL ROSSO, GERARD DOMNICK
• Application Number:
  US08/325,145
• Time in Patent Office: 1,195 Days
• Field of Search: 382/100, 382/131, 382/154, 378/4, 378/20, 378/57, 378/62, 250/390.01, 250/390.04, 250/390.06
• US Class Current: 382/205
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]
• CPC Class Codes: G01V 5/226 using tomography

Abstract

A technique to ascertain the presence or absence of an object in a three-dimensional volume, such as explosives in the side walls of luggage. The technique involves radiation scanning the three-dimensional volume to determine a property of each of a plurality of voxels representing the three-dimensional volume and to identify voxels having similar values of the property to identify a contiguous group of voxels having the similar values. Then, the contiguous group of voxels is identified as containing the object if a characteristic (such as mass and/or volume) of the contiguous group has a predetermined value.

Claims

1. A method of detecting an explosive comprising the steps of:

(a) scanning a three-dimensional volume to determine the density of each of a plurality of voxels representing the three-dimensional volume;

(b) connecting and labeling voxels of the plurality of voxels which have similar densities;

(c) determining the volume of each contiguous region of voxels having similar densities;

(d) comparing the volume of each such contiguous region to a first threshold and identifying each such contiguous region which exceeds the first threshold as a suspect region;

(e) determining the mass of each suspect region; and

(f) comparing the mass of each suspect region to a second threshold and identifying each suspect region which exceeds the second threshold as a region potentially containing an explosive.

2. A method as set forth in claim 1 further comprising the step of:

after step (f), further inspecting the three-dimensional volume to confirm the presence of an explosive.

3. A method as set forth in claim 2, wherein the further inspection includes manual inspection.

4. A method as set forth in claim 2, wherein the further inspection includes neutron interrogation.

6. A method as set forth in claim 1, wherein in step (b) differences between a density of a given voxel and densities of voxels in planes above and below said given voxel, are employed to evaluate contiguity of said plurality of voxels.

5. An apparatus to detect an explosive, comprising:

(a) a scanner to scan a three-dimensional volume to determine the density of each of a plurality of voxels representing the three-dimensional volume; and

(b) a processor which includes

(1) a contiguity identification module to connect and label voxels of the plurality of voxels which have similar densities; and

(2) an object identification module to

(i) determine the volume of each contiguous region of voxels having similar densities;

(ii) compare the volume of each such contiguous region to a first threshold and to identify each such contiguous region which exceeds the first threshold as a suspect region;

(iii) determine the mass of each suspect region; and

(iv) compare the mass of each suspect region to a second threshold and to identify each suspect region which exceeds the second threshold as a region potentially containing an explosive.