Guard efficiency compensation system and method

Patent metadata

Field	Value
Publication number	US-9297909-B2
Application number	US-201514630047-A
Country	US
Kind code	B2
Filing date	Feb 24, 2015
Priority date	Apr 18, 2014
Publication date	Mar 29, 2016
Grant date	Mar 29, 2016

Abstract

A liquid scintillation counting system employs a guard detector efficiency compensation system to adjust sample event counts to compensate for a non-ideal guard which may not detect all cosmic and environmental gamma background noise events. The system and method determines counts of events detected coincidently by a guard detector subsystem and a sample detector subsystem in one or more energy regions as well as counts of events that are detected by the sample detector subsystem and not coincidently detected by the guard detector subsystem for the respective energy regions. The system and method calculates correction values for the respective energy regions based on the counts of coincident and non-coincident events and the guard efficiency values associated with the respective energy regions, using, for example, a quenched or unquenched sample. The system then applies the calculated correction values to counts for the respective energy regions, to produce corrected sample event counts.

First claim

What is claimed is:

1. A radiation detection system comprising:
a scintillator configured to detect sample events associated with an unknown sample;
a guard detector subsystem configured to detect active guard events;
one or more processors adapted to:
count coincident events that are the sample events and the active guard events detected coincidently in one or more energy regions and count non-coincident events that are the sample events detected when the active guard events are not coincidently detected; and
for each energy region
calculate a compensation guard count based on the count of coincident events and a predetermined guard efficiency value associated with the energy region,
calculate a correction value that is based on the compensation guard count and the counts of coincident events and the count of non-coincident events, and
correct the count of non-coincident events corresponding to the energy region based on the calculated correction value to produce corrected sample event counts.

2. The radiation detection system of claim 1 wherein the scintillator is a liquid scintillator.

3. The radiation detection system of claim 1 wherein the scintillator is a crystal scintillator.

4. The radiation detection system of claim 1 wherein the predetermined guard efficiency value is calculated for the respective energy regions using the count of coincident events and the count of non-coincident events that occur when the system is operating in a controlled environment.

5. The radiation detection system of claim 4 wherein the controlled environment includes a source of known radiation.

6. The radiation detection system of claim 1 wherein the predetermined guard efficiency value for a given energy region is calculated as:

GE
R

=

SP
⁢

⁢

12
R

SP
⁢

⁢

12
R

+

SP
⁢

⁢

11
R

where SP12 R is the count of coincident events, and SP11 R is the count of non-coincident events within the energy region R utilizing a standard sample.

7. The radiation detection system of claim 6 wherein the compensation guard count for a given energy region is:

C
⁢

⁢
G
⁢

⁢

C
R

=

SP
⁢

⁢

12
R

GE
R

.

8. The radiation detection system of claim 7 wherein a number of counts missed by the guard subsystem (GCM R ) is:
GCM R =CGC R −SP12 R .

9. The radiation detection system of claim 8 wherein the correction value is a background reduction factor (BRF R ) that is calculated as:

B
⁢

⁢
R
⁢

⁢

F
R

=

1
-

[

GCM
R

SP
⁢

⁢

11
R

]

.

10. The radiation detection system of claim 8 wherein the given energy region is associated with a plurality of channels and the corrected sample event counts are calculated for the respective channels as:
CSP11 n =SP11 n ×BRF R

where CSP11 n is the corrected counts of non-coincident events for channel n in the energy region R.

11. The radiation detection system of claim 1 wherein guard compensation correction may be adjusted based on modifying the guard efficiency value.

12. The radiation detection system of claim 1 wherein the predetermined guard efficiency value associated with each energy region is calculated utilizing a sample that is unquenched.

13. The radiation detection system of claim 1 wherein the predetermined guard efficiency value associated with each energy region is calculated utilizing a sample with a selected quench level.

14. A radiation detection system comprising:
a liquid scintillator configured to detect events in a beta spectrum;
a crystal scintillator guard configured to detect events in a gamma spectrum;
one or more processors adapted to:
mathematically transform the gamma spectrum into a spectrum that follows a Compton backscatter profile that approximates a SP12 spectrum; and
count coincident events between the beta spectrum and the transformed gamma spectrum for one or more energy regions and count non-coincident events that are only in the beta spectrum; and
for each energy region
calculate a compensation crystal scintillator guard count based on the count of coincident events and a predetermined crystal scintillator guard efficiency value associated with the energy region,
calculate a correction value that is based on the compensation crystal scintillator guard count and the counts of coincident and non-coincident events, and
correct counts of non-coincident events in the beta spectrum and corresponding to the energy region based on the calculated correction value.

15. A radiation detection system comprising:
a scintillator configured to detect sample events;
a guard detector subsystem configured to detect active guard events;
one or more processors adapted to:
count coincident events that are the sam

Assignees

• Perkinelmer Health Sci Inc

Inventors

• Harazin Richard R

Classifications

• G01T1/204

  the detector being a liquid · CPC title

• G01T1/208

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

• G01T1/2026 Primary

  Well-type detectors · CPC title

• G01T1/2006 Primary

  using a combination of a scintillator and photodetector which measures the means radiation intensity · CPC title

• G01T1/202

  the detector being a crystal · CPC title