PROTECTION OF A GAMMA RADIATION DETECTOR

• US 20190310384A1
• Filed: 12/21/2017
• Published: 10/10/2019
• Est. Priority Date: 12/21/2016
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: KOK, Christiaan
• Granted Patent: US 11,762,107 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 6/03 Computed tomography [CT] echo-tomography A61B8/14
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/035 Mechanical aspects of CT
• CPC Class Codes: A61B 6/037 Emission tomography
• CPC Class Codes: A61B 6/42 Arrangements for detecting radiation specially adapted for radiation diagnosis
• CPC Class Codes: A61B 6/4208 characterised by using a particular type of detector
• CPC Class Codes: A61B 6/4233 using matrix detectors
• CPC Class Codes: A61B 6/4241 using energy resolving detectors, e.g. photon counting
• CPC Class Codes: A61B 6/4258 for detecting non x-ray radiation, e.g. gamma radiation A61B6/037 takes precedence
• CPC Class Codes: A61B 6/4266 characterised by using a plurality of detector units A61B6/4014 takes precedence
• CPC Class Codes: A61B 6/44 Constructional features of apparatus for radiation diagnosis
• CPC Class Codes: A61B 6/4429 related to the mounting of source units and detector units
• CPC Class Codes: A61B 6/4435 the source unit and the detector unit being coupled by a rigid structure
• CPC Class Codes: A61B 6/4441 the rigid structure being a C-arm or U-arm
• CPC Class Codes: A61B 6/4447 Tiltable gantries
• CPC Class Codes: G01T 1/16 Measuring radiation intensity G01T1/29 takes precedence ; self-powered detectors G01T3/006; using an ionisation chamber filled with a liquid or solid, e.g. frozen liquid, dielectric G01T3/008
• CPC Class Codes: G01T 1/1603 with a combination of at least two different types of detector see provisionally also G01T1/16
• CPC Class Codes: G01T 1/1606 with other specified detectors not provided for in the other sub-groups of G01T1/16 see provisionally also G01T1/16
• CPC Class Codes: G01T 1/161 Applications in the field of nuclear medicine, e.g. in vivo counting apparatus for radiation diagnosis A61B6/00
• CPC Class Codes: G01T 1/1611 using both transmission and emission sources sequentially SPECT imaging G01T1/1642; PET imaging G01T1/2985; detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects G01V5/20
• CPC Class Codes: G01T 1/1612 : with scintillation detectors G01T1/20 takes precedence
• CPC Class Codes: G01T 1/1614 : with semiconductor detectors G01T1/24 takes precedence
• CPC Class Codes: G01T 1/1615 : using both transmission and emission sources simultaneously SPECT imaging G01T1/1642; PET imaging G01T1/2985; detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects G01V5/20
• CPC Class Codes: G01T 1/1617 : with scintillation detectors G01T1/20 takes precedence
• CPC Class Codes: G01T 1/1618 : with semiconductor detectors G01T1/24 takes precedence
• CPC Class Codes: G01T 1/164 : Scintigraphy
• CPC Class Codes: G01T 1/20 : with scintillation detectors
• CPC Class Codes: G01T 1/2002 : Optical details, e.g. reflecting or diffusing layers
• CPC Class Codes: G01T 1/2006 : using a combination of a scintillator and photodetector which measures the means radiation intensity
• CPC Class Codes: G01T 1/2008 : using a combination of different types of scintillation detectors, e.g. phoswich
• CPC Class Codes: G01T 1/2018 : Scintillation-photodiode combinations
• CPC Class Codes: G01T 1/20181 : Stacked detectors, e.g. for measuring energy and positional information using a combination of different types of scintillation detectors, e.g. phoswich detectors, G01T1/2008
• CPC Class Codes: G01T 1/20183 : Arrangements for preventing or correcting crosstalk, e.g. optical or electrical arrangements for correcting crosstalk
• CPC Class Codes: G01T 1/20185 : Coupling means between the photodiode and the scintillator, e.g. optical couplings using adhesives with wavelength-shifting fibres
• CPC Class Codes: G01T 1/24 : with semiconductor detectors
• CPC Class Codes: G01T 1/243 : Modular detectors, e.g. arrays formed from self contained units constructional or manufacturing details H01L25/00
• CPC Class Codes: G01T 1/249 : 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

Abstract

The invention relates to a combined detector (660) comprising a gamma radiation detector (100) and an X-ray radiation detector (661). The gamma radiation detector (100) comprises a gamma scintillator array (101_{x, y}), an optical modulator (102) and a first photodetector array (103_{a, b}) for detecting the first scintillation light generated by the gamma scintillator array (101_{x, y}). The optical modulator (102) is disposed between the gamma scintillator array (101_{x, y}) and the first photodetector array (103_{a, b}) for modulating a transmission of the first scintillation light between the gamma scintillator array (101_{x, y}) and the first photodetector array (103_{a, b}). The optical modulator (102) comprises at least one optical modulator pixel having a cross sectional area (102′) in a plane that is perpendicular to the gamma radiation receiving direction (104). The cross sectional area of each optical modulator pixel (102′) is greater than or equal to the cross sectional area of each photodetector pixel (103′_{a, b}).

Claims

1. A combined detector comprising a gamma radiation detector and an X-ray radiation detector;

the gamma radiation detector comprising;

a gamma scintillator array comprising a plurality of first scintillator elements for generating first scintillation light in response to received gamma quanta;

an optical modulator; and

a first photodetector array for detecting the first scintillation light generated by the gamma scintillator array;

wherein the gamma scintillator array, the optical modulator and the first photodetector array are arranged in a stacked configuration along a gamma radiation receiving direction; and

wherein the optical modulator is disposed between the gamma scintillator array and the first photodetector array for modulating a transmission of the first scintillation light between the gamma scintillator array and the first photodetector array;

wherein the optical modulator comprises at least one optical modulator pixel, the optical modulator pixel having a cross sectional area in a plane that is perpendicular to the gamma radiation receiving direction;

wherein the first photodetector array comprises a plurality of photodetector pixels, each photodetector pixel having a cross sectional area in the plane that is perpendicular to the gamma radiation receiving direction;

wherein the cross sectional area of each optical modulator pixel is greater than or equal to the cross sectional area of each photodetector pixel; and

wherein the X-ray radiation detector is disposed along the gamma radiation receiving direction and on the opposite side of the gamma scintillator array to the first photodetector array.

2. The combined detector according to claim 1 wherein the gamma scintillator array includes a gamma radiation receiving face and an opposing scintillation light output face;

wherein the scintillation light output face is arranged to face the optical modulator;

wherein the gamma radiation detector further comprises a gamma radiation collimator for collimating gamma quanta; and

wherein the gamma radiation receiving face of the gamma scintillator array is arranged to face the gamma radiation collimator.

3. The combined detector according to claim 1 wherein the optical modulator is configured to modulate the transmission of the first scintillation light between the gamma scintillator array and the first photodetector array by modulating at least one of i) the absorption ii) the reflection and iii) the scattering, of the first scintillation light.

4. The combined detector according to claim 1 wherein the optical modulator comprises either i) a liquid crystal device ii) an electrochromic device iii) a MEMS device iv) an electrowetting device v) an electrophoretic device.

5. The combined detector according to claim 1 wherein the X-ray radiation detector comprises either:

an X-ray scintillator array comprising a plurality of second scintillator elements for generating second scintillation light in response to received X-ray quanta;

a second photodetector array for detecting the second scintillation light;

wherein the second photodetector array is in optical communication with the second scintillator elements of the X-ray scintillator array for detecting the second scintillation light; and

wherein the X-ray scintillator array and the second photodetector array are arranged in a stacked configuration along the gamma radiation receiving direction;

or

an array of direct conversion X-ray detector elements;

wherein each direct conversion X-ray detector element is configured to generate electrical signals in response to received X-ray quanta; and

wherein the array of direct conversion X-ray detector elements is arranged in a stacked configuration along the gamma radiation receiving direction.

6. The combined detector according to claim 5 wherein the X-ray radiation detector further comprises an X-ray anti-scatter grid;

wherein the X-ray anti-scatter grid is disposed along the gamma radiation receiving direction and on the opposite side of the X-ray radiation detector to the gamma radiation detector.

7. The combined detector according to claim 6 wherein the X-ray radiation detector forms part of a CT imaging detector.

8. Imaging arrangement comprising the combined detector according to claim 1 and:

an X-ray source; and

a control unit;

wherein the control unit is in communication with the X-ray source and the optical modulator and is configured to control the optical transmission of the optical modulator in synchronization with the emission of X-ray radiation from the X-ray source.

9. Imaging arrangement according to claim 8 wherein the synchronization comprises switching the optical modulator between a first transmission state and a second transmission state;

wherein the first transmission state provides a higher transmission of first scintillation light than the second transmission state;

and wherein the optical modulator is configured to have the second transmission state during a period when the X-ray source emits X-ray radiation.

12. Normalization method for determining electrical offset signals of the first photodetector array of the combined detector of claim 1;

the normalization method comprising the steps of;

switching the optical modulator into an optically blocking state, such that the transmission of the first scintillation light between the gamma scintillator array and the first photodetector array is inhibited; and

measuring, whilst the optical modulator is in the optical blocking state, electrical offset signals generated by the first photodetector array.

13. Imaging method for use with the combined detector of claim 1;

the imaging method comprising the steps of;

measuring, with the normalization method for determining electrical offset signals generated by the first photodetector array whilst the optical modulator is in the optical blocking state;

switching the optical modulator into an optically transmitting state, such that the transmission of the first scintillation light between the gamma scintillator array and the first photodetector array is higher than the transmission in the optical blocking state;

measuring electrical data signals generated by the first photodetector array whilst the optical modulator is in the optically transmitting state, the electrical data signals corresponding to a distribution of a radiotracer in a region of interest;

subtracting the electrical offset signals from the corresponding electrical data signals to generate difference data electrical signals; and

reconstructing a nuclear image corresponding to the distribution of the radiotracer in the region of interest based on the difference data electrical signals.

14. Method for identifying faulty pixels of the first photodetector array of the combined detector of claim 1, the method comprising the steps of:

switching the optical modulator into an optically blocking state, such that the transmission of the first scintillation light between the gamma scintillator array and the first photodetector array is inhibited;

measuring, whilst the optical modulator is in the optical blocking state, electrical offset signals generated by the first photodetector array;

comparing each electrical offset signal with an expected offset signal range; and

associating one or more photodetector pixels of the first photodetector array that have an electrical offset signal that lies outside the predetermined range with a faulty status.

10. Imaging configuration comprising:

a gamma radiation detector

an X-ray source;

an X-ray detector; and

a control unit;

the gamma radiation detector comprising;

a gamma scintillator array comprising a plurality of first scintillator elements for generating first scintillation light in response to received gamma quanta;

an optical modulator; and

a first photodetector array for detecting the first scintillation light generated by the gamma scintillator array;

wherein the gamma scintillator array, the optical modulator and the first photodetector array are arranged in a stacked configuration along a gamma radiation receiving direction; and

wherein the optical modulator (102) is disposed between the gamma scintillator array and the first photodetector array for modulating a transmission of the first scintillation light between the gamma scintillator array and the first photodetector array;

wherein the optical modulator comprises at least one optical modulator pixel, the optical modulator pixel having a cross sectional area in a plane that is perpendicular to the gamma radiation receiving direction;

wherein the first photodetector array comprises a plurality of photodetector pixels, each photodetector pixel having a cross sectional area in the plane that is perpendicular to the gamma radiation receiving direction; and

wherein the cross sectional area of each optical modulator pixel is greater than or equal to the cross sectional area of each photodetector pixel;

wherein the X-ray source and X-ray detector define a field of view; and

wherein the gamma radiation detector is positioned relative to the X-ray detector for generating gamma image data from a region that at least partially overlaps with the field of view;

wherein the control unit is in communication with the X-ray source and the optical modulator and is configured to control the optical transmission of the optical modulator in synchronization with the emission of X-ray radiation from the X-ray source.

11. Computer program product comprising instructions which when executed by a processor cause the control unit of the imaging arrangement or of the imaging configuration of claim 10, to switch the optical modulator between a first transmission state and a second transmission state;

wherein the first transmission state provides a higher transmission of first scintillation light than the second transmission state;

and such that the optical modulator has the second transmission state during a period when the X-ray source emits X-ray radiation.