X-ray detector with csi:ti conversion layer

• US 20050199819A1
• Filed: 05/16/2003
• Published: 09/15/2005
• Est. Priority Date: 05/29/2002
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Wieczorek, Herfried Karl
• Granted Patent: US 7,608,836 B2
• Time in Patent Office: Days
• US Class Current: 250/370.11
• CPC Class Codes: G01T 1/20 with scintillation detectors
• CPC Class Codes: G01T 1/20183 Arrangements for preventing or correcting crosstalk, e.g. optical or electrical arrangements for correcting crosstalk

Abstract

An x-ray detector comprises a conversion layer for converting x-radiation into optical radiation. Photosensitive elements notably photodiodes to derive electronic signals from the optical radiation received by the photosensitive elements. The conversion layer contains Caesium-iodide doped with Thallium (CsI:Tl); the Caesium-iodide doped with Thallium is ultrapure and the Tl-doping level is in the range of 0.25-1.00 at %.

Claims

1. An x-ray detector comprising

a conversion layer for converting x-radiation into optical radiation,

a plurality of photosensitive elements to derive electronic signals from the optical radiation,

the conversion layer containing cesium-iodide doped with thallium (CsI:

Tl),

wherein

the cesium-iodide doped with thallium is ultrapure and

the Tl-doping level is in the range of 0.25-1.00 at %.

2. An x-ray detector as claimed in claim 1, wherein the Tl-doping level is spatially homogeneous.

3. An x-ray detector as claimed in claim 1 wherein the Tl-doping level depends on the thickness of the conversion layer.

4. An x-ray detector as claimed in claim 1, wherein the Tl-doping level depends on the spatial distribution, in particular on the lateral distribution of the Tl-doping level in the conversion layer.

5. An apparatus for detecting x-rays, comprising:

a conversion layer for converting x-radiation into optical radiation, the conversion layer including cesium iodide doped with from 0.25% to 1.00% of thallium; and

a plurality of photosensitive elements configured to derive electronic signals from the optical radiation.

6. The apparatus of claim 5, wherein the optical radiation has a wavelength of at least 400 nanometers and not more than 700 nanometers.

7. The apparatus of claim 5, wherein the conversion layer is substantially free of indium.

8. The apparatus of claim 7, wherein the conversion layer contains an amount of indium in a concentration no greater than 500 parts per million.

9. The apparatus of claim 7, wherein the conversion layer contains an amount of indium in a concentration no greater than 100 parts per million.

10. The apparatus of claim 7, wherein the conversion layer contains an amount of indium in a concentration no greater than 10 parts per million.

11. The apparatus of claim 7, wherein the conversion layer contains an amount of indium in a concentration no greater than 5 parts per million.

12. The apparatus of claim 7, wherein the plurality of photosensitive elements comprise elements selected from the group consisting of photodiodes and phototransistors.

13. The apparatus of claim 12, further comprising:

an x-radiation source for emitting x-rays;

a patient support;

a computed tomography device for creating images based at least in part on the electronic signals derived from the photosensitive elements; and

a display for presenting images to an operator of the apparatus.

14. The apparatus of claim 7, wherein the thickness of the conversion layer is at least 300 μ

m and no greater than 1,000 μ

m.

15. The apparatus of claim 14, wherein the conversion layer comprises a plurality of columnar crystals.

16. A method of forming medical images comprising the steps of:

generating x-rays;

transmitting the x-rays through an examination region;

detecting the transmitted x-rays using an x-ray detector that includes a conversion layer configured to convert x-rays into optical radiation in the range of about 400 to 700 nanometers, the conversion layer comprising cesium iodide doped with from 0.25% to 1% of thallium and further comprising no more than 500 parts per million of indium;

using the detected x-rays to create an electrical signal that is indicative of the detected x-rays; and

using the created electrical signal to form a medical image.

18. The method of claim 16, wherein the conversion layer of the x-ray detector comprises no more than 100 parts per million of indium.

19. The method of claim 16, wherein the conversion layer of the x-ray detector comprises no more than 10 parts per million of indium.

20. The method of claim 16, wherein the conversion layer of the x-ray detector comprises no more than 5 parts per million of indium.

17. The method of claim 17, wherein the medical image is created by computed tomography.