Enabling estimation of an initial point of interaction of an x-ray photon in a photon-counting x-ray detector

Patent metadata

Field	Value
Publication number	US-11054371-B2
Application number	US-201916653200-A
Country	US
Kind code	B2
Filing date	Oct 15, 2019
Priority date	Nov 19, 2018
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

The disclosed method enables estimating an initial point of interaction of an x-ray photon in a photon-counting x-ray detector, based on a number of x-ray detector sub-modules or wafers, each including detector elements. The x-ray detector sub-modules are oriented in edge-on geometry with the edge directed towards the x-ray source, assuming the x-rays enter through the edge. Each detector sub-module or wafer has a thickness with two opposite sides of different potentials to enable charge drift towards the side, where the detector elements, also referred to as pixels, are arranged. Basically, the method includes: determining an estimate of charge diffusion originating from a Compton interaction or an interaction through photoeffect related to the x-ray photon in a detector sub-module or wafer of the x-ray detector; and estimating the initial point of interaction along the thickness of the detector sub-module based on the determined estimate of charge diffusion.

First claim

The invention claimed is:

1. A method for enabling estimation of an initial point of interaction of an x-ray photon in a photon-counting x-ray detector, which is based on a plurality of x-ray detector sub-modules or wafers, each of the x-ray detector sub-modules or wafers including detector elements distributed over the detector sub-module or wafer in two directions including the direction of the incoming x-rays, the x-ray detector sub-modules being oriented in edge-on geometry with the edge directed towards an x-ray source, assuming the x-rays enter through the edge, each detector sub-module or wafer having a thickness with two opposite sides of different potentials to enable charge drift towards the side, where the detector elements that are pixels are arranged, the method comprising:
determining an estimate of charge diffusion originating from a Compton interaction or an interaction through photoeffect related to the x-ray photon in a detector sub-module or wafer of the x-ray detector, the estimate of charge diffusion being determined by measuring or estimating one or more of a shape and a width of the charge diffusion based on indicated current caused by moving electron-hole pairs originating from the Compton interaction or the interaction through photoeffect, as detected by the detector elements that are distributed over the x-ray detector sub-module or wafer in the two directions including the direction of the incoming x-rays; and
estimating the initial point of interaction along the thickness of the detector sub-module based on the determined estimate of one or more of the shape and the width of the charge diffusion.

2. The method of claim 1 , wherein the method is performed for determining, for each of one or more of (i) a number of incident x-ray photons and (ii) a number of x-ray detector sub-modules, a corresponding estimate of charge diffusion, and for determining an estimate of the initial point of interaction of the incident x-ray photon in the respective x-ray detector sub-module.

3. The method of claim 1 , wherein the charge diffusion is represented by a charge cloud, and the estimate of charge diffusion is determined by measuring or estimating one or more of the shape and the width of the charge cloud.

4. The method of claim 3 , wherein the initial point of interaction of the incident x-ray photon along the thickness of the detector sub-module is estimated based on the measured width of the cloud and the integrated charge of the cloud.

5. The method of claim 1 , wherein the estimating the initial point of interaction along the thickness of the detector sub-module comprises:
determining an estimate of a distance, along the thickness of the x-ray detector sub-module, between the point of detection of the x-ray photon in the x-ray detector sub-module and the initial point of interaction based on the estimate of charge diffusion, and
determining the estimate of the initial point of interaction based on the point of detection and the determined estimate of a distance along the thickness of the detector sub-module.

6. The method of claim 5 , wherein the width of the charge diffusion is measured or estimated, and the distance between the point of detection and the initial point of interaction is determined based on the measured width of the charge diffusion or distribution.

7. The method of claim 1 , further comprising determining an estimate of the point of interaction of the incident x-ray photon in at least one of the two directions (x, z) over which the detector elements are distributed on a main side of the x-ray detector sub-module or wafer.

8. The method of claim 7 , wherein the determining the estimate of the point of interaction of the incident x-ray photon in at least one of the two directions (x, z) over which the detector elements are distributed on the main side is performed based on information of a charge cloud profile in one or both of the two directions (x, z) over which the detector elements are distributed on the main side of the x-ray detector sub-module or wafer.

9. The method of claim 8 , further comprising determining the charge cloud profile, performing curve fitting and finding out where the curve has its peak and identifying the peak as the point of interaction in a particular direction.

10. The method of claim 7 , wherein the determining the estimate of the point of interaction of the incident x-ray photon in at least one of the two directions (x, z) over which the detector elements are distributed on the main side is performed by identifying the pixel that has detected the highest charge as the point of interaction.

11. The method of claim 1 , wherein the charge diffusion is represented by a charge cloud, and the detector elements distributed over the x-ray detector sub-module or wafer on a main side provide an array of pixels, where the pixels are smaller than the charge cloud to be resolved.

12. A system for enabling estimation of an initial point of interaction of an x-ray photon in a photon-counting x-ray detector, which is based on a plurality of x-ray detector sub-modules or wafers, each of the x-ray detector sub-modules or wafers including detector elements distributed over the detector sub-module or wafer in two directions including the direction of the incoming x-rays, the x-ray detector sub-modules being oriented in edge-on geometry with the edge directed towards an x-ray source, assuming the x-rays enter through the edge, each detector sub-module or wafer having a thickness with two opposite sides of different potentials to enable charge drift towards the side, where the detector elements that are pixels are arranged, the system comprising:
at least one processor configured to
determine an estimate of charge diffusion originating from a Compton interaction or an interaction through photoeffect related to the x-ray photon in a detector sub-module or wafer of the x-ray detector, the estimate of charge diffusion being determined by measuring or estimating one or more of a shape and a width of the charge diffusion based on indicated current caused by moving electron-hole pairs originating from the Compton interaction or the interaction through photoeffect, as detected by the detector elements distributed over the x-ray detector sub-module or wafer, and
estimate the initial point of interaction along the thickness of the detector sub-module based on the determined estimate of one or more of the shape and the width of the charge diffusion.

13. The system of claim 12 , wherein the at least one processor is configured to determine, for each of one or more of (i) a number of incident x-ray photons and (ii) a number of x-ray detector sub-modules, a corresponding estimate of charge diffusion, and to determine an estimate of the initial point of interaction of the incident x-ray photon in the respective x-ray detector sub-module.

14. The system of claim 12 , wherein the charge diffusion is represented by a charge cloud, and the system is configured to determine the estimate of charge diffusion by measuring or estimating one or more of the shape and the width of the charge cloud.

15. The system of claim 14 , wherein the system is configured to estimate the initial point of interaction of the incident x-ray photon along the thickness of the detector sub-module based on the measured width of the cloud and the integrated charge of the cloud.

16. The system of claim 12 , wherein the at least one processor is configured to
determine an estimate of a distance, along the thickness of the x-ray detector sub-module, between the point of detection of the x-ray photon in the x-ray de

Assignees

• Prismatic Sensors Ab

Inventors

• Danielsson Mats

Classifications

• G01T1/247 Primary

  Detector read-out circuitry (for processing gain or off-set correction H04N) · CPC title

• G01N23/046 Primary

  using tomography, e.g. computed tomography [CT] · CPC title

• G01T1/241

  Electrode arrangements, e.g. continuous or parallel strips or the like · CPC title

• G01T1/2928

  using solid state detectors · CPC title