Energy and position sensitive radiation detectors

• US 5,783,829 A
• Filed: 11/06/1996
• Issued: 07/21/1998
• Est. Priority Date: 11/06/1995
• Status: Expired due to Fees

• Current Assignee: Ralph D. Pinto, University of Virginia
• Original Assignee: University of Virginia
• Inventors: Bengis, Daniel Van Horn, Sealock, Richard, Rondon-Aramayo, Oscar
• Primary Examiner(s): Porta, David P.
• Application Number:
  US08/744,763
• Time in Patent Office: 622 Days
• Field of Search: 250/366, 250/367, 250/368, 250/369
• US Class Current: 250/367
• CPC Class Codes: G01T 1/20 with scintillation detectors
• CPC Class Codes: G01T 1/20185 Coupling means between the photodiode and the scintillator, e.g. optical couplings using adhesives with wavelength-shifting fibres
• CPC Class Codes: G01T 1/20187 Position of the scintillator with respect to the photodiode, e.g. photodiode surrounding the crystal, the crystal surrounding the photodiode, shape or size of the scintillator
• CPC Class Codes: G01T 1/202 the detector being a crystal

Abstract

A device and a method for determining the interaction position and energy measurement of a radiation detector. A plurality of waveshifting optical fiber are positioned on the surface of a scintillator which is subjected to incident radiation causing the release of photons of a first wavelength from the scintillator which are absorbed by the optical fiber with a portion of the released photons being reemitted from one end of the fibers. The reemitted photons are measured and the centroid of the distribution of these measured photons is determined in order to provide an indication of the interaction position of incident radiation. A measurement of photons generated by the incident radiation which pass through the fibers but which are not transported down said fibers provide an indication of the energy of the incident radiation. In a further embodiment, a crossed wire anode photomultiplier is used in conjunction with a plurality of scintillating fibers embedded in grooves on both sides of the scintillator in order to provide an accurate position for the centroid of a more extended distribution of incident photons. Furthermore a designed neural network extracts, from the crossed wire anode photomultiplier output pulses, a linear position to provide real time imaging.

Claims

1. A method for detecting the interaction position of incident radiation comprising the steps of:

positioning a plurality of wave-shifting optical fibers on one surface of a scintillator;

subjecting said scintillator to radiation which causes, in said scintillator, the release of photons of a first wavelength from said scintillator which are absorbed by said plurality of wave-shifting optical fibers;

measuring photons of a second wavelength reemitted from one end of each of said fibers;

forming a representation of the distribution of reemitted photons for each of said wave-shifting optical fiber; and

determining a position where said radiation strikes said scintillator as a function of the centroid of the distribution of detected photons.

2. The method according to claim 1 wherein the width of said distribution is a function of the distance between the interaction point of said incident radiation and said plurality of fibers.

3. The method according to claim 2 comprising the further steps of:

providing at least one light detection device proximal to said plurality of wave-shifting optical fibers;

measuring, by means of said at least one light detection device, photons generated by said incident radiation, which pass through said plurality of fibers together with reemitted, wave-shifted photons which escape from said fibers in order to provide a measure of the energy of said incident radiation.

4. A device for measuring the interaction position of incident radiation, comprising:

a scintillator for emitting light of a first frequency in response to incident radiation;

a plurality of wave-shifting optical fibers positioned adjacent to each other on a surface of said scintillator;

first means for measuring light reemitted by each of said plurality of wave-shifting optical fibers in response to said emitted light from said scintillator wherein said first means for measuring includes a means for determining the distribution of reemitted light along the said plurality of optical fibers in order to provide a determination of the position at which incident radiation interacted with said scintillator.

5. The device according to claim 4 further comprising a second measurement means for measuring said emitted light which passes through said plurality of optical fibers and is not reemitted from said optical fibers plus light reemitted from said optical fibers but not transported to ends of said optical fibers in order to provide a measurement of the energy of said incident radiation.

6. The device according to claim 5 wherein said second measurement means is at least one photomultiplier or at least one-photodiode.

7. A position-sensitive radiation detector, comprising:

at least one set of a plurality of wave-shifting optical fibers positioned proximal to a respective surface of a scintillator positioned to receive an incident radiation;

at least one first photomultiplier positioned to receive light reemitted from one end of each of said plurality of optical fibers from each respective set of optical fibers;

a second photomultiplier positioned proximal to a length of one of said at least one set of wave-shifting optical fibers for receiving light from said scintillator which passes through said one set of optical fibers whereby said at least one first photomultiplier provides a measurement of a position of incident radiation on said scintillator and wherein said one second photomultiplier provides a measurement of the energy of said incident radiation.

8. A position-sensitive radiation detector, comprising:

at least one set of a plurality of waveshifting optical fibers positioned proximal to a respective surface of a scintillator positioned to receive incident radiation;

at least one crossed wired anode photomultiplier respectively associated with said at least one set of waveshifting optical fibers, said at least one crossed wire anode photomultiplier providing four output signals;

means for measuring said four output signals and providing position resolution for the centroid of an extended distribution of incident photons provided by said scintillator and delivered by said plurality of waveshifting fibers of each of said at least one set in order to establish an interaction position of said incident radiation on said scintillator.

9. The device according to claim 8 wherein said means for measuring said four output signals include a neural network circuit including an input node, a bias input, and a single, linear output wherein said input node receives two of said outputs of said crossed wire anode and wherein said linear output provides a real time image measurement.

10. The device according to claim 9 wherein said neural network circuit includes three separate networks for performing measurement on a region of said detector and a fourth network which classifies said input pulses for one of said three networks.