Detection device for detecting photons and method therefore

Patent metadata

Field	Value
Publication number	US-9759822-B2
Application number	US-201415038768-A
Country	US
Kind code	B2
Filing date	Nov 20, 2014
Priority date	Nov 27, 2013
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

The present invention relates to a detection device ( 6 ) for detecting photons emitted by a radiation source ( 2 ). The detection device ( 6 ) is configured to detect the photons during a first time period. The detection device ( 6 ) comprises a sensor ( 10 ) having an intermediate direct conversion material for converting photons into electrons and holes, a shaping element ( 20 ), and a compensation unit ( 450 , INT, 950 ). The compensation unit ( 450 , INT, 950 ) is adapted to provide a compensation signal based on the electrical pulse and on a photoconductive gain of said sensor ( 10 ). The core of the invention is to provide circuits to reduce artifacts due to inherent errors with direct conversion detectors in spectral computed tomography by determining a compensation current, by detecting or monitoring a baseline restorer feedback signal, or by ignoring signals above the baseline level.

First claim

The invention claimed is:

1. A detection device for detecting photons emitted by a radiation source, wherein the detection device is configured to detect the photons during a first time period, the detection device comprising:
a sensor comprising an anode, a cathode and an intermediate direct conversion material for converting photons into electrons and holes,
a shaping element adapted to convert a charge pulse generated by a photon into an electrical pulse, and
a compensation unit coupled between an output of the shaping element and an input of the shaping element,
wherein the compensation unit comprises a photoconductive gain providing circuitry, wherein said photoconductive gain providing circuitry is configured to provide a photoconductive gain for said sensor,
wherein the compensation unit further comprises a second-time-period current providing unit, wherein said second-time-period current providing unit is configured to provide a current from said sensor during at least a second time period, wherein said second time period is shorter than said first time period,
wherein the compensation unit is adapted to provide a compensation signal to said shaping element,
wherein said compensation signal is based on the current from said sensor and on the photoconductive gain for said sensor.

2. The detection device according to claim 1 , wherein the compensation unit comprises a first, second, and third current source, and a first and a second transistor; and wherein a source of the first transistor and a source of the second transistor are coupled to the first current source.

3. The detection device according to claim 2 , wherein a drain of the first transistor is coupled to the second current source; wherein a drain of the second transistor is coupled to the third current source; wherein the electrical pulse is provided to a gate of the first transistor; wherein a reference voltage is provided to a gate of the second transistor; and wherein the drain of the second transistor is coupled to the input of the shaping element.

4. The detection device according to claim 2 , wherein the detection device further comprises:
a baseline restorer circuit;
a switching network comprises first, second, third, and fourth switches wherein the baseline restorer circuit is coupled between the first and second switches; and
a current mirror;

wherein the detection device is operable in a first and a second mode; wherein, in the first mode, the first and second switches are closed so that the baseline restorer circuit is operable, the third switch couples a drain of the second transistor to the current mirror, and the fourth switch couples a drain of the first transistor to ground; and wherein, in the second mode, the first and second switches are open, so that the baseline restorer circuit is disconnected and the third switch couples the drain of the second transistor to the drain of the first transistor.

5. The detection device according to claim 2 , wherein the detection device further comprises a fourth current source, wherein the fourth current source is coupled between a drain of the second transistor and a drain of the first transistor.

6. The detection device according to claim 5 , wherein the detection device further comprises a digital-to-analog converter and an integrating channel, wherein the digital-to-analog converter s coupled between an output of the integrating channel and a control input of the fourth current source.

7. The detection device according to claim 1 , wherein the compensation unit further comprises a baseline restorer circuit.

8. The detection device according to claim 1 , wherein the compensation unit comprises a baseline restorer circuit, and a polarization determination unit, wherein the polarization determination unit is adapted to determine a degree of polarization within the sensor from a baseline restorer current from the baseline restorer circuit.

9. The detection device according to claim 8 , wherein the polarization determination unit further comprises an integrator circuit, wherein the integrator circuit is adapted to integrate a baseline restorer current from the baseline restorer circuit and to provide the baseline restorer current to the input of the shaping element.

10. The detection device according to claim 1 , wherein the compensation unit comprises a baseline restorer circuit and a limiter circuit, wherein the limiter circuit is coupled between the output of the shaping element and the input of the baseline restorer circuit.

11. The detection device according to claim 10 , wherein the limiter circuit is adapted to block provision of the electrical pulse to the baseline restorer circuit, if the electrical pulse is above a predetermined threshold.

12. The detection device according to claim 1 , wherein the second time period is within the first time period; wherein the second-time-period current providing unit is configured to measure a pixel current from said sensor during the second time period; and wherein the current from said sensor provided by the second-time-period current providing unit corresponds to said pixel current.

13. A detection method for detecting photons emitted by a radiation source by a detection device during a first time period, the detection method comprising:
providing a sensor comprising an anode, a cathode and an intermediate direct conversion material for converting photons into electrons and holes,
providing a photoconductive gain for said sensor,
converting, with a shaping element, a charge pulse generated by a photon into an electrical pulse,
providing a current from said sensor during at least a second time period, wherein said second time period is shorter than said first time period,
providing a compensation signal to the shaping element, wherein the compensation signal is based on the current from said sensor and on the photoconductive gain for said sensor, and
processing the electrical pulses to form an image.

14. The detection method according to claim 13 , wherein providing a compensation signal comprises determining a degree of polarization within the sensor from a baseline restorer current.

15. The detection method according to claim 13 , wherein providing a compensation signal comprises:
providing the electrical pulse to a limiter circuit and
providing the electrical pulse to a baseline restorer circuit if the limiter circuit determines that the electrical pulse is below a predefined threshold.

Assignees

• Koninklijke Philips Nv

Inventors

• Daerr Heiner
• Herrmann Christoph
• Bergner Frank
• Steadman Booker Roger

Classifications

• G01T1/247 Primary

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

• G01T1/17

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

• G01T1/249

  specially adapted for use in SPECT or PET (SPECT imaging G01T1/1642; PET imaging G01T1/2985; detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects G01V5/20) · CPC title