Multi-layer x-ray detector for diagnostic imaging

• US 6,553,092 B1
• Filed: 03/07/2000
• Issued: 04/22/2003
• Est. Priority Date: 03/07/2000
• Status: Expired due to Term

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Mattson, Rodney A., Shapiro, Olga
• Primary Examiner(s): Dunn, Drew A.
• Assistant Examiner(s): Kao, Glen
• Application Number:
  US09/519,704
• Time in Patent Office: 1,141 Days
• Field of Search: 378/19, 250/368, 250/483.1, 250/367, 250/370.09, 250/370.11
• US Class Current: 378/19
• CPC Class Codes: G01T 1/20183 Arrangements for preventing or correcting crosstalk, e.g. optical or electrical arrangements for correcting crosstalk
• CPC Class Codes: G01T 1/20185 Coupling means between the photodiode and the scintillator, e.g. optical couplings using adhesives with wavelength-shifting fibres

Abstract

X-rays from an x-ray tube (16) pass through an examination region (14) and are detected by a single or two-dimensional x-ray detector (20). The x-ray detector (20) includes an array (22) of photodiodes, CCD devices, or other opto-electrical transducer elements. A matching array (24) of transparent scintillator crystals, e.g., CdWO₄, is supported on and optically coupled to the photoelectric transducer array. A layer (26) of a high efficiency scintillator with a good spectral match with the opto-electrical transducer array but with limited light transmissiveness is optically coupled to the transparent scintillator array. The layer (26) is preferably zinc selenide ZnSe (Te). Electrical signals from the transducer array are reconstructed (32) into an image representation and converted into a human-readable display (38). To reduce cross-talk, the zinc selenide layer is etched with pits (40), sliced into strips (26′), cut into rectangles (26″), or has channels (44) cut into it. Scatter grids (46) are advantageously received in the channels. Alternately, the zinc selenide can be powdered, encased in a transparent binder, and applied as a coating layer (26″′) to the individual transparent scintillator elements.

Claims

1. In a medical diagnostic imaging system which generates images from x-rays propagating from a radiation source to a radiation detector, the radiation detector comprising:

a multi-layer scintillator including upper scintillating layers of relatively longer emission wavelength and lower x-ray absorption, at least one of the upper layers being doped zinc selenide, and lower scintillating layers of higher x-ray absorption and shorter emission wavelength which are substantially transparent to the light emitted by the upper layers, the upper and lower layers being aligned and arranged serially along a path of x-ray propagation and presenting a substantially equal cross section to x-rays propagating along the path; and

a light sensitive array optically coupled to a lowest of the lower scintillating layers for viewing the multi-layer scintillator and combining the optical outputs of its multi-layers into an analog output which is adapted for reconstruction into a diagnostic image.

2. The radiation detector as set forth in claim 1 wherein the zinc selenide is in powdered form and is incorporated into a sheet of transparent resin.

3. The radiation detector as set forth in claim 1 wherein one of the lower scintillating layers includes a layer of monocrystalline cadmium tungstate.

4. In a medical diagnostic imaging system which generates images from x-rays propagating from a radiation source to a radiation detector, the radiation detector comprising:

a multi-layer scintillator including;

an upper non-segmented scintillating layer of zinc selenide doped with tellurium, and

a two-dimensional array of scintillators arranged to form a lower scintillating layer with higher z-ray absorption and shorter emission wavelength than tellurium doped zinc selenide and which is substantially transparent to the light emitted by the tellurium doped zinc selenide layer,the upper and sower layer being arranged serially along a path of x-ray propagation and presenting a substantially equal cross section to x-rays propagating along the path; and

a two-dimensional array of opto-electric transducers, each transducer optically coupled to one of the scintillators of the lower scintillating layer, each of the opto-electric transducers combining the optical outputs from the upper scintillating layer and a corresponding one of the scintillators of the lower scintillating layer into an electrical output signal which is adapted for reconstruction into a diagnostic image.

5. The radiation detector as set forth in claim 4 wherein the upper scintillating layer:

includes;

powdered doped zinc selenide scintillator material dispersed in a transparent binder.

6. The radiation detector system as set forth in claim 4 wherein the upper scintillating layer includes a series of parallel channels.

8. The radiation detector system as set forth in claim 4 wherein the upper scintillating layer includes particulate zinc selenide doped with tellurium scintillator dispersed in a light transmissive binder.

7. The medical diagnostic imaging system as set forth in claimed further including x-ray scatter grids received and supported in the channels.

9. In a medical diagnostic by imaging system which generates images from x-rays propagating from a radiation source to a radiation detector, the radiation detector comprising:

a multi-layer scintillator including an upper scintillating layer of monocrystalline doped zinc selenide, and at least one lower scintillating layer defined by a two-dimensional array of cadmium tungstate scintillator tiles each of which has higher x-ray absorption and shorter emission wavelength than the doped zinc selenide and each of which is substantially transparent to the light emitted by the upper layer, the upper and lower layers being arranged along a path of x-ray propagation and presenting a substantially equal cross section to x-rays propagating along the path; and

,

a two-dimensional array of photodiodes, each photodiode optically coupled to a corresponding one of the scintillator tiles of the lower layer for converting an optical output of the corresponding scintillator tile and an optical contribution from the upper layer into an electrical output signal which is adapted for reconstruction into a diagnostic image.

10. In a diagnostic imaging system which generates images from x-rays propagating from a radiation source to a radiation detector, the radiation detector comprising:

a multi-layer scintillator including upper scintillating layers of relatively longer emission wavelength and lower x-ray absorption, at least one of the upper layers being doped zinc selenide, and lower scintillating layers of higher x-ray absorption and shorter emission wavelength which are substantially transparent to the light emitted by the upper layers; and

an array of silicon photodetectors with a spectral response peak in a range of 600-1000 nanometers optically coupled to a lowest of the lower scintillating layers for viewing the multi-layer scintillator and combining optical outputs of its multi-layers into an electrical output which is adapted for reconstruction into a diagnostic image.

11. A radiographic examination system comprising:

an x-ray source for projecting x-rays through an examination region;

an x-ray detector disposed across the examination region from the x-ray source, the x-ray detector including;

a unitary doped zinc selenide scintillation layer which is etched in a two-dimensional first grid pattern to promote internal scattering of light within the zinc selenide layer, the zinc selenide scintillation layer converting x-rays into light,

a two-dimensional array of light transmissive scintillators arranged in a second grid pattern and disposed below the zinc selenide scintillation layer to conduct the light from the zinc selenide scintillation layer and to convert x-rays that passed through the zinc selenide scintillator into light, and

a two-dimensional array of opto-electrical transducers arranged in a third grid pattern, the first, second, and third grid patterns directly overlaying each other, such that the opto-electrical transducers convert light from the zinc selenide scintillator layer and the light transmissive scintillator array into electrical signals.

12. A radiographic examination system comprising:

an x-ray source for projecting x-rays across an examination region;

an x-ray detector disposed across the x-ray examination region from the x-ray source, the x-ray detector including;

an array of opto-electrical elements,

an array of light transmissive scintillators disposed on and optically coupled to the array of opto-electrical elements such that each of the opto-electrical elements converts light received from a corresponding transmissive scintillator into an electrical output signal, and

a layer of higher efficiency scintillator material optically coupled to the transmissive scintillator array, a grid of pits being defined in a surface of the higher efficiency scintillator layer opposite the transmissive scintillator array to induce scatter, the higher efficiency scintillator layer being a scintillator material of limited opacity, higher x-ray conversion efficiency than the transmissive scintillators, and having a better optical match to a peak sensitivity spectrum of the opto-electrical transducers than the transmissive scintillators.

13. The radiographic examination system as set forth in claim 12 wherein the higher efficiency scintillator layer is a ceramic scintillator layer.

14. A radiographic examination system comprising:

an x-ray source for projecting x-rays across an examination region;

an x-ray detector disposed across the x-ray examination region from the x-ray source, the x-ray detector including;

an array of opto-electrical elements,

an array of light transmissive scintillators disposed on and optically coupled to the array of opto-electrical elements such that each of the opto-electrical elements converts light received from a corresponding transmissive scintillator into an electrical output signal, and

a high efficiency scintillator layer divided into one of strips and rectangles which are dimensionally mismatched to the array of light transmissive scintillators and are optically coupled to the light transmissive scintillator array, the higher efficiency scintillator layer being a scintillator material of limited opacity, higher x-ray conversion efficiency than the transmissive scintillators, and having a better optical match to a peak sensitivity spectrum of the opto-electrical transducers than the transmissive scintillators.