Radiation source position detection method, radiation source position detection system and radiation source position detection probe

• US 6,862,087 B2
• Filed: 05/20/2003
• Issued: 03/01/2005
• Est. Priority Date: 05/20/2002
• Status: Active Grant

• Current Assignee: Japan Aerospace Exploration Agency, Mitsubishi Heavy Industries, Ltd.
• Original Assignee: Japan Aerospace Exploration Agency, Mitsubishi Heavy Industries, Ltd.
• Inventors: Masuko, Ryouchi, Kuroda, Yoshikatsu, Takahashi, Tadayuki, Watanabe, Shin
• Primary Examiner(s): Gregory, Bernarr E.
• Assistant Examiner(s): ANDREA, BRIAN K
• Application Number:
  US10/441,024
• Publication Number:
  US 20040037394A1
• Time in Patent Office: 651 Days
• Field of Search: 356 501- 515, 356/141.1, 250/201.6, 250/390.12, 250/370.1
• US Class Current: 356/141.1
• CPC Class Codes: A61B 2090/392 Radioactive markers
• CPC Class Codes: A61B 6/4429 related to the mounting of source units and detector units
• CPC Class Codes: A61B 6/547 involving tracking of position of the device or parts of the device
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: G01T 1/169 Exploration, location of contaminated surface areas
• CPC Class Codes: G01T 1/2907 Angle determination; Directional detectors; Telescopes prospecting by the use of nuclear radiation, e.g. of natural or induced radioactivity G01V5/00

Abstract

A radiation source position detection system is provided, wherein three radiation detectors are arranged at different positions. Based on radiations incident to each of the radiation detectors, curved surfaces where a radiation source exists are calculated. By solving equations of each of the curved surfaces simultaneously, the position of the radiation source is detected.

Claims

1. A method of detecting a radiation source position, comprising:

detecting a radiation from a radiation source at three or more different detection positions with a detector which includes a plurality of detection plates arranged in predetermined space relations respectively;

estimating at least three curved surfaces where the radiation source exists by calculating a function to minimize a value of chi-square with respect to each of the detection position respectively, the value of chi-square using each of the number of radiations incident to each detection plates and each of the predetermined space relations; and

acquiring the position of the radiation source based on said each estimated curved surface.

2. A method of detecting a radiation source position according to claim 1,

wherein the position of the radiation source is acquired by an analysis method in which equations of the at least three curved surfaces are simultaneously solved, a method of numeral calculation in which ratio of count for each of the detection plates with the radiation source arranged at a plurality of given positions is determined by simulation and a method based on a calibration test in which a relation between ratio count for each of the detection plates with the radiation source arranged at a plurality to given positions is determined by actual measurement.

3. A method of detecting a radiation source position, comprising:

detecting a radiation from a radiation source at three or more different detection positions with a detector which includes a plurality of detection plates arranged in predetermined space relations respectively;

estimating at least three curved surfaces where the radiation source exists by calculating a function to minimize a value of chi-square with respect to at least different three directions respectively, the value of chi-square using each of the number of radiations incident to each detection plates and each of the predetermined space relations; and

acquiring the position of the radiation source based on said each estimated curved surface.

4. A method of detecting a radiation source position according to claim 3,

wherein the position of the radiation source is acquired by an analysis method in which equations of the at least three curved surfaces are simultaneously solved, a method of numerical calculation in which ratio of count for each of the detection plates with the radiation source arranged at a plurality to given positions is determined by simulation, and a method based on a calibration test in which a relation between ratio count for each of the detection plates with the radiation source arranged at a plurality to given positions is determined by actual measurement.

5. A radiation source position detection system comprising:

at least three radiation detectors each of which includes a plurality of detection plates arranged in predetermined space relations respectively and detects incident radiations b each detection plate;

an estimation unit which estimates at least three curved surfaces where the radiation source exists by calculating a function to minimize a value of chi-square with respect to each of the detection position, the value of chi-square using each of the number of radiations incident to each detection plates and each of the predetermined space relations; and

position acquisition units which acquires the position of the radiation source based on said each estimated curved surfaces.

6. A radiation source position detection system according to claim 5,

wherein the position of the radiation source is acquired by an analysis method in which equations of the at least three curved surfaces are simultaneously solved, a method of numeral calculation in which ratio of count for each of the detection plates with the radiation source arranged at a plurality to given positions is determined by simulation, and a method based on a calibration test in which a relation between ratio count for each of the detection plates with the radiation source arranged at a plurality to given positions is determined by actual measurement.

7. A radiation source position detection system according to claim 6, wherein said each detection plate is composed of a semiconductor or a scintillator.

8. A radiation source position detection system comprising:

radiation detectors which detects an incident radiation along different first, second and third directions, respectively;

estimation unit which estimate a first curved surface, a second curved surface, and a third curved surface where the radiation source exists, by calculating a function to minimize a value of chi-square with respect to first, second, and third directions respectively, the value or chi-square using each of the number of radiations incident to each detection plates and each of the predetermined relations; and

position acquisition units which acquire the position of the radiation source based on each of the curved surf aces estimated by each of the estimation unit.

9. A radiation source position detection system according to claim 8;

wherein the radiation detectors each includes a first layer having a first detection plate; and

a second layer arranged in predetermined spaced relation in a front or subsequent stage of the first layer and having second, third and fourth detection plates, the radiation incident from the first direction is detected by a first detection unit including the first detection plate and the second detection plate, the radiation incident from the second direction is detected by a second detection unit including the first detection plate and the third detection plate, and the radiation incident from the third direction is detected by a third detection unit including the first detection plate and the fourth detection plate, and

said each estimation unit detects the number of radiations incident to each detection plate;

estimates the first curved surface where the radiation source exists, based on the number of the radiations incident to said each detection plate configuring the first detection unit and the distance between the first detection plate and the second detection plate;

estimates the second curved surface where the radiation source exists, based on the number of the radiations incident to said each detection plate configuring the second detection unit and the distance between the first detection plate and the third detection plate; and

estimates the third curved surface where the radiation source exists, based on the number of the radiations incident to said each detection plate configuring the third detection unit and the distance between the first detection plate and the fourth detection plate.

10. A radiation source position detection system according to claim 9, wherein each of the first to fourth detection plates includes a semiconductor or a scintillator.

11. A radiation source position detection system according to claim 8;

wherein the radiation detectors each includes;

a first detection plate;

a second detection plate arranged in a first spaced relation with the first detection; and

a third detection plate arranged in a second spaced relation with the first detection plate and having a center axis different from that of the first detection plate and the second detection plate, the radiation ray incident from the first direction is detected by a first detection unit including the first detection plate and the second detection plate, the radiation ray incident from the second direction is detected by a second detection unit including the first detection plate and the third detection plate, and the radiation ray incident from the third direction is detected by a third detection unit including the second detection plate and the third detection plate, and

said estimation unit detects the number of radiations incident to each detection plate;

estimates the first curved surface where the radiation source exists, based on the number of the radiations incident to said each detection plate configuring the first detection unit and the distance between the first detection plate and the second detection plate;

estimates the second curved surface where the radiation source exists, based on the number of the radiations incident to said each detection plate configuring the second detection unit and the distance between the first detection plate and the third detection plate; and

estimates the third curved surface where the radiation source exists, based on the number of the radiations incident to said each detection plate configuring the third detection unit and the distance between the second detection plate and the third detection plate.

12. A radiation source position detection system according to claim 11, wherein each of the first to third detection plates includes a semiconductor or scintillator.

13. A radiation detection probe for detecting incident radiations along different first, second and third directions, comprising:

a first layer having a first detection plate; and

a second layer arranged in a predetermined spaced relation in a front or subsequent stages of the first layer and having second, third and fourth detection plates,

wherein the incident radiations are detected along the first direction by a first detection unit including the first detection plate and the second detection plate, along the second direction by a second detection unit including the first detection plate and the third detection plate, and along the third direction by a third detection unit including the first detection plate and the fourth detection plate, respectively.

14. A radiation detection probe according to claim 13, wherein each of the first to fourth detection plates includes a semiconductor or a scintillator.

15. A radiation detection probe for detecting incident radiations along different first, second and third directions, comprising:

a first detection plate;

a second detection plate arranged in a first spaced relation with the first detection plate; and

a third detection plate arranged in a second spaced relation with the first detection plate and having a shape or a center axis different from that of the first detection plate and the second detection plate,

wherein the incident radiations are detected along the first direction by a first detection unit including the first detection plate and the second detection plate, along the second direction by a second detection unit including the first detection plate and the third detection plate, and along the third direction by a third detection unit including the second detection plate and the third detection plate, respectively.

16. A radiation source position detection probe according to claim 15, wherein each of the first to third detection plates includes a semiconductor and a scintillator.