Photon counting spectral CT

Patent metadata

Field	Value
Publication number	US-11435488-B2
Application number	US-201917053890-A
Country	US
Kind code	B2
Filing date	May 7, 2019
Priority date	May 8, 2018
Publication date	Sep 6, 2022
Grant date	Sep 6, 2022

Abstract

A radiation detector (100) adapted for detecting leakage currents is disclosed and comprises a direct conversion material (101) for converting incident radiation, at least one first electrode (108) and a plurality of second electrodes (103) connected to surfaces of the direct conversion material (101) for collecting each generated charges upon application of an electric field, at least one current measurement device (201), and a plurality of signal processing chains (210, 220, 230). Each signal processing chain comprises a readout unit (215, 216, 217, 218, 219) for discriminating between energy values with respect to the incident radiation, and a switching element (214) for sending signals on a first signal path (2141) electrically connecting one of the plurality of second electrodes with the readout unit, or on a second signal path electrically connecting the one of the plurality of second electrodes with an input to one of the at least one current measurement devices. A plurality of switching elements is configured to send signals on the second signal path for measuring a leakage current received at a corresponding plurality of second electrodes of the detector in the absence of incident radiation.

First claim

The invention claimed is:

1. A radiation detector configured for detecting leakage currents, comprising:
a direct conversion material for converting incident radiation into charges, the direct conversion material having a first major surface and a second major surface;
at least one first electrode connected to the first major surface of the direct conversion material and a plurality of second electrodes connected to the second major surface of the direct conversion material, each electrode of the at least one first electrode and the plurality of second electrodes being arranged for collecting charges generated in an electric field applied between the first and the second electrodes;
at least one shared current measurement device; and
a plurality of signal processing chains, each signal processing chain of the plurality of signal processing chains comprising:
a discriminator configured to discriminate between energy values with respect to the incident radiation; and
a switch configured to:
send a first signal on a first signal path electrically connecting one electrode of the plurality of second electrodes with the discriminator for discriminating between energy values; and
send a second signal on a second signal path electrically connecting the one electrode of the plurality of second electrodes with an input to the at least one shared current measurement device;

wherein the switches of the plurality of signal processing chains are configured to send, to the at least one shared current measurement device, the second signals from the plurality of second electrodes on the second signal paths for measuring a leakage current received at a corresponding plurality of second electrodes in the absence of incident radiation.

2. The detector according to claim 1 , wherein the direct conversion material is a CZT crystal.

3. The detector according to claim 1 , wherein the plurality of second electrodes are arranged as an array of electrodes on the second major surface.

4. The detector according to claim 1 , further comprising a storage configured to store a measured leakage current.

5. The detector according to claim 1 , wherein the at least one shared current measurement device comprises an analog-to-digital-converter.

6. The detector according to claim 1 , wherein at least one signal processing chain of the plurality of signal processing chains further comprises:
a leakage current detector; and
a leakage current compensator for the first signal sent on the first signal path and for the second signal sent on the second signal path,
wherein an output of the leakage current detector is connected to an input of the leakage current compensator, and
wherein an output of the leakage current compensator is connected to the switch.

7. A detector system, comprising:
a radiation source;
an image reconstructor configured to reconstruct images of an object; and
a plurality of radiation detectors, each radiation detector of the plurality of radiation detectors being configured for detecting leakage currents, each radiation detector of the plurality of radiation detectors comprising:
a direct conversion material for converting incident radiation into charges, the direct conversion material having a first major surface and a second major surface;
at least one first electrode connected to the first major surface of the direct conversion material and a plurality of second electrodes connected to the second major surface of the direct conversion material, each electrode of the at least one first electrode and the plurality of second electrodes being arranged for collecting charges generated in an electric field applied between the first and the second electrodes;
at least one shared current measurement device; and
a plurality of signal processing chains, each signal processing chain of the plurality of signal processing chains comprising:
a discriminator configured to discriminate between energy values with respect to the incident radiation; and
a switch configured to:
send a first signal on a first signal path electrically connecting one electrode of the plurality of second electrodes with the discriminator for discriminating between energy values; and
send a second signal on a second signal path electrically connecting the one electrode of the plurality of second electrodes with an input to the at least one shared current measurement device;

wherein the switches of the plurality of signal processing chains are configured to send, to the at least one shared current measurement device, the second signals from the plurality of second electrodes on the second signal paths for measuring a leakage current received at a corresponding plurality of second electrodes in the absence of incident radiation.

8. The detector system according to claim 7 , wherein the image reconstructor comprises a detector model which uses a measured leakage current for correcting spectral energy shifts.

9. The detector system according to claim 7 , further comprising a display configured to display leakage current distributions of the plurality of detectors.

10. A method for detecting leakage currents in a direct conversion radiation detector, comprising:
providing at least one first electrode connected to a first major surface of a direct conversion material and a plurality of second electrodes connected to the second major surface of the direct conversion material, each electrode of the at least one first electrode and the plurality of second electrodes being arranged for collecting charges generated in an electric field applied between the first and the second electrodes;
converting collected charges to detection signals;
process the detection signals by discriminating between energy values with respect to incident radiation with a plurality of signal processing chains, each signal processing chain of the plurality of signal processing chains comprising a discriminator for discriminating between energy values with respect to the incident radiation;
sending a first signal on a first signal path electrically connecting one electrode of the plurality of second electrodes with the discriminator for discriminating between energy values, and sending a second signal on a second signal path electrically connecting the one electrode of the plurality of second electrodes with an input to one of the at least one shared current measurement devices;
wherein the plurality of switches send, to the at least one shared current measurement device, the second signals from the plurality of second electrodes on the second signal path for measuring a leakage current received at a corresponding plurality of second electrodes in the absence of incident radiation.

11. The method according to claim 10 , further comprising storing a measured leakage current.

12. The method according to claim 10 , further comprising reconstructing images of an object to obtain projection data for radiation traversing the object.

13. The method according to claim 12 , further comprising using a detector model which uses a measured leakage current for correcting spectral energy shifts.

14. The method according to claim 10 , further comprising displaying leakage current distributions.

Assignees

• Koninklijke Philips Nv

Inventors

• Steadman Booker Roger
• Herrmann Christoph Jan
• Erhard Klaus
• Brendel Bernhard Johannes
• Daerr Heiner
• Sossin Artur
• Thran Axel

Classifications

• G01T1/247 Primary

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

• A61B6/032

  Transmission computed tomography [CT] · CPC title

• G01T1/17

  Circuit arrangements not adapted to a particular type of detector {(pulse-selection circuits H03K, G01R)} · CPC title