Systems and methods for radiation detection with improved event type discrimination

Patent metadata

Field	Value
Publication number	US-10145967-B2
Application number	US-201615337885-A
Country	US
Kind code	B2
Filing date	Oct 28, 2016
Priority date	Oct 21, 2016
Publication date	Dec 4, 2018
Grant date	Dec 4, 2018

Abstract

Described herein are radiation detection systems and methods that provide improved discrimination between different types of radioactive events. The use of multiple discriminator settings based on pulse curve shape, rather than a single setting, is surprisingly found to improve discrimination between alpha and beta events. Results demonstrate significantly lowered % spill with minimal loss of efficiency due to the enhanced discrimination. These systems and methods are particularly important in the detection of extremely low-level alpha and beta events, and in the identification and quantification of isotopes with difficult-to-distinguish pulse shapes.

First claim

What is claimed is:

1. A method for quantifying two or more kinds of radionuclides present in a test sample, the method comprising:
for each of a plurality of finite detected radioactive events in the test sample, obtaining, by a processor of a computing device, a measure of pulse shape, where the measure is a function of pulse intensity and pulse duration;
sorting, by the processor, each of the finite detected radioactive events according to its measure of pulse shape into one of at least three categories using distinct first and second discriminator settings, where the event is identified as originating from a first kind of radionuclide if its measure of pulse shape has a value below the first discriminator setting, the event is identified as originating from a second kind of radionuclide if its measure of pulse shape has a value above the second discriminator setting, and the event is identified as indeterminate if its measure of pulse shape has a value between the first and second-discriminator settings; and
displaying, by the processor, a measure of the first kind of radionuclide and a measure of the second kind of radionuclide.

2. The method of claim 1 , wherein the two or more kinds of radionuclides comprise a beta emitter and an alpha emitter.

3. The method of claim 1 , wherein each of the plurality of finite detected radioactive events has an associated signal of detected light intensity measured as a function of time by a liquid scintillation counter from which the measure of pulse shape is determined.

4. The method of claim 1 , wherein the measure of pulse shape is or is a function of a measure of pulse or tail area divided by pulse amplitude.

5. The method of claim 1 , wherein the event is identified as originating from a beta emitter if its measure of pulse shape has a value below the first discriminator setting and the event is identified as originating from an alpha emitter if its measure of pulse shape has a value above the second discriminator setting, where the first discriminator setting is lower than the second discriminator setting.

6. The method of claim 1 , wherein the sorted events include a non-zero number of events in each of three categories—events originating from the first kind of radionuclide, events originating from the second kind of radionuclide, and indeterminate events.

7. The method of claim 1 , wherein the measure of the first kind of radionuclide is or is a function of a sum of sorted events having a measure of pulse shape value below the first discriminator setting, and the measure of the second kind of radionuclide is or is a function of a sum of sorted events having a measure of pulse shape value above the second discriminator setting.

8. A method for applying discriminator settings in the quantification of radionuclides present in a test sample comprising at least a first and second radionuclide that are of different kinds, the method comprising:
receiving, by a processor of a computing device, data corresponding to a measure of pulse shape for each of a plurality of finite detected radioactive events in a first calibration sample comprising a first calibration radionuclide that is the same kind of emitter as and is or is similar to the first radionuclide in the test sample;
receiving, by the processor, data corresponding to a measure of pulse shape for each of a plurality of finite detected radioactive events in a second calibration sample comprising a second calibration radionuclide that is the same kind of emitter as and is or is similar to the second radionuclide in the test sample;
displaying, by the processor, a graphical representation of differentiated radioactive events corresponding to the first and second calibration samples as a function of corresponding measure of pulse shape;
displaying, by the processor, a graphical user interface element allowing adjustment of one or both of a first discriminator setting, and a second discriminator setting, and where an event is identified as originating from the first radionuclide if its measure of pulse shape has a value below the first discriminator setting, the event is identified as originating from the second radionuclide if its measure of pulse shape has a value above the second discriminator setting, and the event is identified as indeterminate if its measure of pulse shape has a value between the first and second discriminator settings;
receiving, by the processor, a selection by a user of a setting of the graphical user interface element defining the first and second discriminator settings;
determining and displaying, by the processor, a measure of spill and/or a measure of efficiency for each of the first and second calibration radionuclides given the user-selected setting of the graphical user interface element;
receiving, by the processor, an adjusted setting of the graphical user interface element corresponding to one or both of an adjusted first discriminator setting, and an adjusted second discriminator setting;
determining and displaying, by the processor, a measure of spill and/or a measure of efficiency for each of the first and second calibration radionuclides according to the adjusted setting of the graphical user interface element;
obtaining, by the processor, for each of a plurality of finite detected radioactive events in the test sample, a measure of pulse shape;
sorting, by the processor, each of the finite detected radioactive events in the test sample according to its measure of pulse shape using the adjusted setting of the graphical user interface element; and
displaying, by the processor, a measure of the first radionuclide in the test sample and the second radionuclide in the test sample according to the adjusted setting of the graphical user interface element.

9. The method of claim 8 , wherein each of the plurality of finite detected radioactive events in at least one of (i) the first calibration sample, (ii) the second calibration sample, and (iii) the test sample has an associated signal of detected light intensity measured as a function of time by a liquid scintillation counter from which the measure of pulse shape is determined.

10. The method of claim 8 , wherein the first calibration sample does not comprise any radionuclide other than the first calibration radionuclide and/or wherein the second calibration sample does not comprise any radionuclide other than the second calibration radionuclide.

11. The method of claim 8 , wherein the adjusted setting is a user-adjusted setting.

12. The method of claim 8 , comprising sorting, by the processor, each of the finite detected radioactive events according to its measure of pulse shape into one of at least three categories using distinct first and second discriminator settings, where the event is identified as originating from a first kind of radionuclide if its measure of pulse shape has a value below the adjusted first discriminator setting, the event is identified as originating from a second kind of radionuclide if its measure of pulse shape has a value above the adjusted second discriminator setting, and the event is identified as indeterminate if its measure of pulse shape has a value between the adjusted first and the adjusted second discriminator settings.

13. A method for automatically optimizing discriminator settings in the quantification of radionuclides present in a test sample comprising at least a first and second radionuclide that are of different kinds, the method comprising:
receiving, by a processor of a computing device, data corresponding to a measure of pulse shape for each of a plurality of finite detected radioactive events in a first calibration sample comprising

Assignees

• Perkinelmer Health Sci Inc

Inventors

• Belobraydich Michael
• Harazin Richard

Classifications

• G01T1/204

  the detector being a liquid · CPC title

• G01T1/208 Primary

  Circuits specially adapted for scintillation detectors, e.g. for the photo-multiplier section · CPC title

• G01T1/178 Primary

  for measuring specific activity in the presence of other radioactive substances, e.g. natural, in the air or in liquids such as rain water · CPC title

• G01N15/1429

  Signal processing · CPC title