Two dimensional photon counting position encoder system and process

• US 4,743,764 A
• Filed: 12/04/1984
• Issued: 05/10/1988
• Est. Priority Date: 12/04/1984
• Status: Expired due to Term

• Current Assignee: Siemens Medical Solutions USA Incorporated (Siemens AG)
• Original Assignee: Computer Technology and Imaging Incorporated
• Inventors: Douglas, Terry D., Casey, Michael E., Nutt, Ronald
• Primary Examiner(s): Howell, Janice A.
• Application Number:
  US06/677,931
• Time in Patent Office: 1,253 Days
• Field of Search: 250/363 S, 250/363 SB, 250/368, 250/505.1, 250/367
• US Class Current: 250/363.03
• CPC Class Codes: G01T 1/202 the detector being a crystal
• CPC Class Codes: G01T 1/2985 In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis); using external radiation sources A61B6/02

Abstract

A two dimensional photon position encoder system (10) and process which includes a detector (20) for enhancing the spatial resolution of the situs of the origin of incident photons of gamma rays. A plurality of scintillator material members (22) interact with the incident photons and produce a quantifiable number of photons which exit the scintillation material members. A tuned light guide (68) having a plurality of radiation barriers (92) of predetermined lengths define slots which are operatively associated with one of the scintillator material members. Photons exiting the scintillator material members (22) enter an operatively associated slot in said slotted light guide. These slots (90) serve to enhance the predictability of the statistical distribution of photons along the length of the slotted light guide (68). A detector (20) detects the distribution of the photons at preselected locations along the length of the slotted light guide. In one embodiment, this detector (20) comprises a photomultiplier (70) which gathers information concerning the photoelectrons which are then counted. The statistical distribution of these photoelectrons is processed by an improved pattern recognition technique such that the positioning information can be determined.

Claims

1. A two dimensional photon position encoder system, including a scintillation detector which enhances the spatial resolution of the situs of the origin of photons incident thereon, position encoder system comprising:

a plurality of scintillator material members which interact with incident gamma rays to produce a quantifiable number of photons;

a tuned light guide having a plurality of optical barriers of predetermined lengths which define slots, each of said slots being operatively associated with one of said scintillator material members whereby photons exiting said scintillator material members enter an operatively associated slot in said slotted light guide, said slots having a preselected depth to control the distribution of photons along the axial and transaxial dimensions of said slotted light guide; and

means operatively associated with said light guide at a location remote from said scintillator material members for detecting the distribution of said photons at preselected locations on said slotted light guide whereby said gamma rays produce optical photons which are distributed by said tuned light guide in a controlled statistical pattern and are detected by said means for detecting the distribution of said photons.

2. The two-dimensional photon position encoder cover system of claim 1 wherein said means for detecting said photons comprises a plurality of photomultipliers each of said photomultipliers being operatively associated with selected slots of said slotted light guide for counting photons exiting said slotted light guide at preselected locations along the length thereof, the number of said photomultipliers being less than the number of said scintillator material members.

3. The two-dimensional photon position encoder system of claim 1 wherein said scintillator material members comprise bismuth germanate crystals which are arranged in an array having a preselected number of crystals in each column and each row of said array.

4. A scintillation detector comprising:

a plurality of scintillator material members which interact with incident radiation to produce a quantifiable number of photons, said scintillator material members being arranged in an array having a preselected number of members in each column and row of said array;

a tuned light guide operatively associated with said scintillator material members, said light guide including a plurality of barriers defining a preselected number of slots, at least one slot being operatively associated with at least one of said scintillator material members whereby photons exiting said members enter said slots in said light guide, said slots having a preselected and adjustable depth to control the variable statistical distribution of said photons as said photons pass through said light guide; and

a plurality of photomultipliers operatively associated with said light guide for counting photons exiting preselected sections of said light guide.

5. The scintillator detector of claim 4 wherein the number of said photomultipliers is less than the number of said scintillator material members.

6. The scintillator detector of claim 4 wherein said scintillator material members comprise bismuth germanate crystals.

7. A positron emission tomography process for sensing and quantitatively measuring biochemical and/or physiological changes in a living organism in which a radioactive compound, including a radioactive isotopes are administered to such living organism such that positrons are emitted from the isotopes as the isotopes are metabolized in the organism, each emitted positron encountering an electron such that both are annihilated causing the emission of gamma rays taking the form of two photons, which are emitted from the situs of the annihilation in opposite directions (180 degrees), said process comprising:

positioning a plurality of scintillator material members in an array such that said photons are incident thereon and produce a quantifiable number of photons which exit said scintillator material members array in response to the interaction of photons on said scintillator material members;

controlling the statistical distribution of exiting sections of the said scintillator material members array with a tuned light guide;

detecting the distribution of said photons exiting said light guide at preselected sectional locations on said light guide whereby said distribution of said photons exiting said light guide is a quantitative measure of said biochemical and/or physiocal changes in said living organism; and

comparing the information regarding the counted photons with a preselected statistical distribution of photon counts to determine the position of the scintillation event whereby such position information can be fed to a computer to produce a tomographic image.

8. A positron emission tomography process for sensing and quantitively measuring biochemical and/or physiological changes in a living organism in which a radioactive compound, including a radioactive isotopes are administered to such living organism such that positrons are emitted from the isotopes as the isotopes are metabolized in the organism, each emitted positron encountering an electron such that both are annihilated causing the emission of gamma rays taking the form of two photons, whcih are emitted from the situs of the annhilation in opposite directions (180 degrees), said process comprising:

positioning a plurality of scintilator material members in an array having a eight scintillator material members in each column and four scintillator members in each column such that said photons are incident thereon and produce a quantifiable number of photons which exit said scintillator material members array in response to the interaction of photons on said scintillator material members;

controlling the statistical distribution of photons exiting sections of the said scintillator material members array with a tuned light guide; and

detecting the distribution of said photons exiting said light guide at preselected sectional locations on said light guide whereby said distribution of said photons exiting asid light guide is a quantitative measure of said biochemical and/or physlogical changes in said living organism.

9. A scintillation detector comprising:

a plurality of crystals fabricated from a scintillation material, said crystals being optically isolated from each other and arranged in an array having a selected number of rows and columns, said crystals defining a first two dimensional face upon which photons are incident and an oppoiste two dimensional face through which photons exit said crystal array;

a tuned light guide operatively associated with said crystals, said light guide including a plurality of barriers defining a preselected number of slots, each of said slots being operatively associated with at least one of said crystals, said light guide defining a first face which optically connected with the opposite face of said crystal array such that each slot registers with each crystal whereby photons exiting said crystals enter the registering slot in said light guide, asid light guide defining an opposite face through which photons exit said light guide, said slots therein having a preselected and adjustable depth to control the variable statistical distribution of said photons as said photons traveling through said light guide exit said opposite face thereof; and

a plurality of photomultipliers operatively associated with said opposite face of said light guide through which said photons travel in a controlled statistical distribution pattern, said photomultipliers being arranged in an array having a selected number of columns and rows, the array of said photomultipliers having a lesser number of elements than the array of said crystals, whereby the detection of the statistical distribution of said photons provides information which uniquely defines the location of a scintillation event.