Split energy radiation detection

• US 5,138,167 A
• Filed: 01/23/1991
• Issued: 08/11/1992
• Est. Priority Date: 01/23/1991
• Status: Expired due to Term

• Current Assignee: Board of Trustees of The University of Alabama For The University of Alabama In Birmingham The University Station Birmingham Al 35294
• Original Assignee: University of Alabama At Birmingham (University of Alabama System)
• Inventors: Barnes, Gary T.
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US07/649,362
• Time in Patent Office: 566 Days
• Field of Search: 250/363.02, 250/370.01, 250/370.06, 250/370.09, 250/370.11, 378/156
• US Class Current: 250/370.01
• 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 1/20182 Modular detectors, e.g. tiled scintillators or tiled photodiodes stacked detectors G01T1/20181
• 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 1/202 the detector being a crystal

Abstract

An energy discriminating apparatus and method is disclosed for use in connection with digital radiography and fluoroscopy. In use of the detection system and method an x-ray source is actuated to direct x-rays through a patient'"'"'s body, the x-rays including both higher and lower energy radiation. A first detector element, including a plurality of segments, is positioned opposite the source to receive and respond predominantly to x-rays in a lower energy range, the remaining x-rays, being generally of higher energy, passing through the first detector element. A second detector element, also including a plurality of segments, each segment including a phosphor coating layer and a sensor, is positioned to receive and respond to the higher energy radiation passing through the first element. The sensors are coupled respectively to each detector element segment for substantially simultaneously sensing the response and spatial location, relative to the detector elements, of radiation to which each detector element respectively responds. A filter element is interposed between the first and second detectors to enhance discrimination in the energy response of the respective detector elements. Particular preferred detector phosphor materials are identified. The sensors produce separately and simultaneously information representing patterns of relatively lower and higher energy emergent from the patient'"'"'s body. Digital data processing and conversion equipment responds to the sensors to produce digital information representing each of said images, which can be digitally processed to enhance image characteristics. Rare earth tantalates and semiconductor materials can also be used as radiation detection layers.

Claims

1. An energy discriminating radiation detector comprising:

a) a first element comprising a first material of a kind which is preferentially responsive to penetrative radiation of a first energy range, said response being defined by a first characteristic, said first characteristic defining a first peak radiation absorptive energy value;

b) a second element comprising a second material different from said first material and of a kind which is preferentially responsive to penetrative radiation of a second energy range said response being defined by a second characteristic, said second energy range extending higher than said first energy range, said second characteristic defining a second peak radiation absorptive energy value higher than said first peak energy value, said second element being positioned to receive radiation which has penetrated through a portion of said first element, and

c) a filter of penetrative radiation interposed between said first and second elements, said filter comprising material and having thickness such that said filter exhibits a main radiation attenuation roll off with respect to energy, said roll off occurring at an energy value lower than said second peak value.

2. The detector of claim 1 wherein:

said roll off occurs substantially between said first and second peak values.

3. A dual layer radiation detector comprising:

a) a first portion aligned to receive penetrative radiation from a source;

b) a second portion aligned with said first portion to receive radiation from said source subsequent to its passage through said first portion, said second portion comprising a material different from that of said first portion, and

c) a radiation filtration layer interposed between said first and second portions, said radiation filtration layer comprising a portion of one or more materials having an atomic number of between 24 and 58, and being approximately 0.2 to 1.0 millimeters in thickness.

4. An energy discriminating radiation detector comprising:

a) a first component comprising a first quantity of semiconductor material which is preferentially responsive to body-penetrative radiation of a first energy range;

b) a second component comprising a quantity of semiconductor material which is preferentially responsive to penetrative radiation of a second energy range extending higher than said first energy range, said second component being positioned to receive radiation which has penetrated through a portion of said first component, and

c) means coupled to said first and second components to produce electrical signals representing an image of radiation when incident on said first and second components.

5. A radiation detector system comprising:

a) a source for propagating radiation along a path;

b) a detector assembly spaced from said source and interposed in said second path, said detector assembly comprising;

i) a first portion of said semiconductor material interposed in said path;

ii) a second portion of semiconductor material interposed in said path and aligned with said first portion behind said first portion with respect to said source, and

c) means coupled to said first and second portions of semiconductor material for producing an electrical representation of radiation when incident on said detector assembly.

6. The system of claim 5, wherein said first and second portions comprise material selected from the group including lead oxide, mercuric iodide, gallium arsenide, cadmium telluride, germanium and silicon.

7. The system of claim 5, wherein:

a) said first portion comprises germanium, and

b) said second portion comprises lead oxide.

8. The system of claim 5, wherein:

a) said first portion comprises germanium, and

b) said second portion comprises mercuric iodide.

9. The system of claim 5, wherein:

a) said first portion comprises gallium arsenide, and

b) said second portion comprises lead oxide.

10. The system of claim 5, wherein:

a) said first portion comprises gallium arsenide, and

b) said second portion comprises mercuric iodide.

11. The system of claim 5, wherein:

a) said first portion comprises cadmium telluride, and

b) said second portion comprises lead oxide.

12. An energy discriminating radiation detector comprising:

a) a first component comprising a first material of a first kind which is preferentially responsive to penetrative radiation of a first energy range;

b) a second component comprising a rare earth tantalate material and aligned to receive penetrative radiation subsequent to its passage through said first component, and

c) means coupled to said first and second components to produce electrical signals representing an image of radiation when incident respectively on said first and second components.

13. The detector of claim 12, wherein said rare earth tantalate is selected from the group of yttrium tantalate, gadolinium tantalate and lutetium tantalate.

14. The detector of claim 13, wherein said first component comprises yttrium oxysulfide.

15. An energy discriminating radiation imaging system comprising:

a) a source for causing propagation of penetrative radiation through a portion of a subject to emerge therefrom in a pattern;

b) an energy discriminating radiation detector located to receive said- pattern of penetrative radiation, said detector comprising;

i) first material of a first kind which is preferentially responsive to penetrative radiation of a first energy range, said first material having a primary radiation absorber comprising an element having an atomic number in the range of 37 to 57;

ii) a second material different in kind from said first material and of a kind which is preferentially responsive to penetrative radiation of a second energy range extending higher than said first energy range, said second material being positioned to receive radiation which has penetrated through a portion of said first material, said second material having a primary radiation absorber comprising an element having an atomic number in the range of 56 to 83, and

iii) means coupled to said first and second materials to produce electric signals representing radiation response by said first and second materials.