High resolution radiation detector

• US 4,303,860 A
• Filed: 07/30/1979
• Issued: 12/01/1981
• Est. Priority Date: 07/30/1979
• Status: Expired due to Term

• Current Assignee: Trust C.O. American
• Original Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Inventors: Benveniste, Victor M., Bjorkholm, Paul J.
• Primary Examiner(s): Smith, Aflred E.
• Assistant Examiner(s): Fields, Carolyn E.
• Application Number:
  US06/061,739
• Time in Patent Office: 855 Days
• Field of Search: 250/367, 250/368, 250/366, 250/363 R, 250/363 S, 250/370
• US Class Current: 250/363.02
• CPC Class Codes: G01T 1/1644 using an array of optically separate scintillation elements permitting direct location of scintillations G01T1/1645 takes precedence
• CPC Class Codes: G01T 1/20181 Stacked detectors, e.g. for measuring energy and positional information using a combination of different types of scintillation detectors, e.g. phoswich detectors, G01T1/2008
• 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 1/20186 Position of the photodiode with respect to the incoming radiation, e.g. in the front of, below or sideways the scintillator

Abstract

A high resolution detector having a scintillation crystal for receiving incident X-rays at a front face and interacting with the radiation to generate corresponding visible light radiation. Silicon photodiode arrays are positioned on top and bottom lateral faces of the scintillation crystal to receive the visible light that is radiated laterally with respect to the direction of propagation of the incident X-rays. Photodiode elements in each photodiode array extend from the forward face of the scintillation crystal in the direction of propagation of the incident X-rays. The length of the photodiode elements determines the radiation stopping power of the high resolution detector and the height of the front face of the scintillation crystal determines the resolution of the detector. The height of the forward face of the crystal may be made small with respect to the length of the photodiode elements to provide a detector having high resolution and high radiation stopping power.

Claims

1. A high resolution radiation detecting apparatus for generating electrical signals representative of the intensity of incident primary radiation, the apparatus comprising:

at least one scintillation crystal for receiving primary radiation and generating corresponding secondary radiation, said at least one scintillation crystal including a front face for receiving incident primary radiation, a back face opposite said front face and top and bottom emission faces for emitting at least a portion of said secondary radiation, the distance between said front and back faces being sufficiently great to allow a desired portion of said primary radiation to be stopped by said at least one scintillation crystal, and the distance between said top and bottom emission faces being sufficiently small to minimize the scattering of said secondary radiation within said scintillation crystal before the secondary radiation is emitted from the crystal;

detector means including a plurality of radiation detecting elements, each element having means for generating an electrical signal representative of the intensity of incident secondary radiation; and

coupling means for passing the secondary radiation emitted from areas of at least one of said emission faces to associated detecting elements.

2. The apparatus of claim 1 wherein said detector means includes at least one solid state detector and said radiation detecting elements are photodiodes of the solid state detector.

3. The apparatus of claim 1 wherein said detector means includes:

a first plurality of solid state detector devices, each device having a plurality of said radiation detecting elements, the devices arranged in a spaced relation with respect to one another along said top emission face of the scintillation crystal, and

a second plurality of solid state detector devices, each device having a plurality of said radiation detecting elements, the devices arranged in a spaced relation with respect to one another along said bottom emission face at positions opposite the spaces defined for the devices of the top emission face and overlapping on either side of the spaces.

4. The apparatus of claim 1 wherein said coupling means includes a coupling grease disposed between said detector means and the surface of said at least one emission face for reducing the lateral spreading of the secondary radiation that passes from the emission face to the detector means.

5. The apparatus of claim 1 wherein said coupling means includes optical fibers for optically connecting said detector means and the surface of said at least one emission face.

6. The apparatus of claim 1 wherein the dimension of said at least one scintillation crystal between said front face and said back face is greater than the dimension of said crystal between said top and bottom emission faces.

7. An improved radiant energy imaging apparatus of a type wherein a source of high energy radiation generates an associated beam of radiation and the beam is moved to irradiate successive cross-sections of a target body and the radiation that is transmitted through the body is converted to video signals for display, the improvement comprising:

a scintillation crystal positioned adjacent said body and having a front face for receiving the transmitted radiation, the crystal extending a particular distance in the direction of propagation of said transmitted radiation for interacting with a desired portion of the transmitted radiation and generating corresponding light radiation that is emitted from a top and a bottom lateral emission face of the crystal, the distance between said top and bottom lateral emission faces being sufficiently small to minimize the scattering of said light radiation within the scintillation crystal before the light radiation is emitted from the crystal; and

detector means for receiving the emitted light radiation from at least one of said emission faces and generating electrical signals corresponding to the intensity of the emitted light radiation, the detector means including a plurality of radiation detecting elements, each element for receiving the secondary radiation emitted from an associated area of said at least one emission face.

8. The radiant energy imaging apparatus of claim 7 including means for generating a fan beam of high energy radiation to pass through a cross-sectional portion of said body and irradiate the length of said scintillation crystal.

9. The radiant energy imaging apparatus of claim 7 including means for generating a pencil beam of high energy radiation and transversely scanning said pencil beam across said body and along the length of said scintillation crystal to produce a cross-sectional scan of the body.

10. The radiant energy imaging apparatus of claim 7 wherein said detector means includes, a first plurality of solid state detectors positioned in a spaced relation along the length of the top lateral emission face of the scintillation crystal, and a second plurality of solid state detectors arranged along the length of the bottom lateral emission face of the scintillation crystal in a spaced relation at positions opposite the spaces defined for the detectors of the top emission face and overlapping on either side of the spaces.

11. The radiant energy imaging apparatus of claim 10 wherein each of said solid state detectors includes a plurality of said detecting elements for detecting emitted light radiation and generating corresponding electrical signals, each detecting element extending from the front of its associated lateral emission face in the direction of propagation of said transmitted radiation.

12. The radiant energy imaging apparatus of claim 10 including optical coupling means disposed between said solid state detectors and said scintillation crystal for reducing the lateral spreading of the light radiation that passes from the scintillation crystal to the solid state detectors.