Multiple energy detector

• US 10,156,642 B2
• Filed: 03/02/2016
• Issued: 12/18/2018
• Est. Priority Date: 03/04/2015
• Status: Active Grant

• Current Assignee: Rapiscan Systems Incorporated (OSI Systems Incorporated)
• Original Assignee: Rapiscan Systems Incorporated (OSI Systems Incorporated)
• Inventors: Morton, Edward James
• Primary Examiner(s): Porta, David
• Assistant Examiner(s): VU, MINDY D
• Application Number:
  US15/058,802
• Publication Number:
  US 20160259067A1
• Time in Patent Office: 1,021 Days
• CPC Class Codes: G01T 1/20 with scintillation detectors
• CPC Class Codes: G01T 1/20184 Detector read-out circuitry, e.g. for clearing of traps, compensating for traps or compensating for direct hits
• CPC Class Codes: G01T 1/2023 Selection of materials see provisionally also G01T1/202
• CPC Class Codes: G01T 1/208 Circuits specially adapted for scintillation detectors, e.g. for the photo-multiplier section

Abstract

The present specification describes an improved multi-energy radiation detector. In one embodiment, the signal generated by the detection medium is converted to digital form directly at the point of signal collection. This avoids the need for power intensive high bandwidth amplifiers and analog-to-digital converters, as it integrates the sensing device and signal processing onto the same silicon substrate to reduce the number of components in the system. In one embodiment, a single photon avalanche diode (SPAD) is coupled directly to a threshold detector to achieve an intrinsically low power and low noise detector.

Claims

1. A multi-energy detector for detecting incident radiation, comprising:

a scintillator material adapted to convert the incident radiation into a plurality of optical photons;

an array of pixel circuits, wherein each pixel circuit comprises a single photon avalanche diode (SPAD) coupled to a threshold detector, wherein each SPAD is optically coupled to the scintillator material and adapted to generate a current in response to detecting one or more optical photons, and a threshold detector in electrical communication with the SPAD, wherein the threshold detector configured to generate a digital pulse in response to said current; and

processing electronics for processing the digital pulse from each pixel circuit in said array of pixel circuits and converting said digital pulse into an energy profile of the incident radiation, wherein the processing electronics comprises an accumulator configured to generate a pixel count, a latching register configured to receive the pixel count from the accumulator and store the pixel count, a digital buffer configured to receive the pixel count from the latching register and buffer the pixel count, and a digital pulse processor configured to receive the buffered pixel count from the digital buffer, determine a specific energy value, and transmit the energy value to a range shifter.

2. The multi-energy detector of claim 1, wherein each of said pixel circuits further comprises an active quench circuit, wherein the active quench circuit is configured to reset said SPAD.

3. The multi-energy detector of claim 1, wherein the scintillator material is LYSO crystal.

4. The multi-energy detector of claim 1, wherein said array of pixel circuits and said processing electronics are fabricated on a single CMOS substrate.

5. The multi-energy detector of claim 1 wherein said range shifter is configured to receive said energy value from said digital pulse processor, scale said energy value, and transmit said scaled energy value to a histogrammer.

6. The multi-energy detector of claim 5 wherein said histogrammer is configured to receive said scaled energy value from said range shifter, generate a histogram of said scaled energy value to create energy spectrum data, and transmit said energy spectrum data to a serializer.

7. The multi-energy detector of claim 6 wherein said serializer is configured to receive said energy spectrum data from said histogrammer and transmit said energy spectrum data to an external device for signal analysis and image display.

8. The multi-energy detector of claim 1, wherein the digital pulse processor is configured to determine the specific energy value by searching time sequence data to find an X-ray pulse and its associated pulse height, wherein the pulse height represents a corresponding energy level.

9. The multi-energy detector of claim 1 further comprising a clock, which is used to drive said array of pixel circuits and said processing electronics.

10. The multi-energy detector of claim 9, wherein a frequency of the clock is varied to vary the gain of said multi-energy detector.

11. The multi-energy detector of claim 10, wherein the frequency of the clock is in the range of 100 MHz to 500 MHz.

12. The multi-energy detector of claim 1 wherein the scintillator material is at least one of Lu_1.8Y_0.2SiO₅(Ce) (LYSO), lutetium oxyorthosilicate (LSO), gadolinium oxyorthosilicate (GSO), or lanthanum Bromide (LaBr).

13. The multi-energy detector of claim 1 further comprising a pair of flip flop latches, wherein the threshold detector is configured to transmit a to the pair of flip flop latches for obtaining the digital pulse.

14. The multi-energy detector of claim 1 wherein the threshold detector is a field effect transistor (FET) which is configured to change state as a result of a charge injection from the SPAD.

15. The multi-energy detector of claim 1 further comprising an active quench circuit coupled with the SPAD, wherein the active quench circuit is adapted to reset the SPAD after a detection of a photon.

16. The multi-energy detector of claim 1, wherein the SPAD, the scintillator material, and the threshold detector are each configured onto a single CMOS substrate.