Shielded source detection and activity correction system
View Patent ↗The method of analyzing the measured radiation spectra to estimate the identified nuclide activities using a designated efficiency calibration based on average expected geometry and using spectral characteristics to flag significant shielding that would otherwise skew said nuclide activities (FIG. 5 ). And providing an estimation of activity correction factor or attenuation factor for each affected nuclide ( 200 ).
1. A method of analyzing measured radiation spectra to determine an estimated nuclide attenuation factor for use in nuclide activity measurements, the method steps comprising:
obtaining a whole spectrum peak-to-total counts ratio for at least one nuclide source from at least one radiation detector spectrometer device;
comparing the whole spectrum peak-to-total counts ratio to a general threshold to determine the presence of significant shielding;
calculating a photopeak scattering metric on a per nuclide photopeak basis using the amount of excess counts in the scattered continuum regions immediately below and immediately above the peak energy region, relative to the net peak area for the nuclide; and
indexing the photopeak scattering metric by energy to an expected shielding response function to yield an estimated attenuation factor to correct the nuclide activity measurements.
2. The method of claim 1 wherein the threshold is a value ranging from approximately 0.1 to 0.05.
3. The method of claim 1 , the method steps further comprising:
comparing measured relative scattering characteristics to expected values for a range of shielding conditions to yield the estimated attenuation factor.
4. The method of claim 1 , the method steps further comprising:
estimating the attenuation factor using the parameterized relationship of the following characterization equation:
Attenuation
Factor
=
ⅇ
Slope
(
%
Fraction
-
Offset
)
,
where
Offset
=
AF
[
6
]
×
Energy
AF
[
7
]
Slope
=
{
AF
[
1
]
+
AF
[
2
]
×
ⅇ
AF
[
3
]
×
Energy
,
Energy
<
500
keV
AF
[
4
]
+
AF
[
5
]
×
Energy
,
Energy
≥
500
keV
.
5. The method of claim 1 , wherein the threshold is derived using the detector device intrinsic peak-to-total calibration value applicable for an unshielded source.
6. The method of claim 1 , the method steps further comprising:
analyzing the energy dependent scattering differential response by comparing measured relative scattering characteristics to expected values for a-range of shielding conditions to yield the estimated attenuation factor.
7. The method of claim 1 wherein the threshold is derived from a worst case energy calculation for the nuclide.
8. The method of claim 1 wherein the threshold is indexed by the weighted average energy of the spectrum photopeaks for the nuclide.
9. A computer software program tangibly embodied in a computer readable medium, the program including machine-readable instructions executable by a computer processor to perform a method of analyzing measured radiation spectra to determine an estimated nuclide attenuation factor for use in nuclide activity measurements, the program steps comprising:
obtaining a whole spectrum peak-to-total counts ratio for at least one nuclide source from at least one radiation detector spectrometer device;
comparing the whole spectrum peak-to-total counts ratio to a general threshold to determine the presence of significant shielding;
calculating a photopeak scattering metric on a per nuclide photopeak basis using the amount of excess counts in the scattered continuum regions immediately below and immediately above the peak energy region, relative to the net peak area for the nuclide; and
indexing the photopeak scattering metric by energy to an expected shielding response function to yield an estimated attenuation factor to correct the nuclide activity measurements.
10. The computer software program of claim 9 wherein the threshold is a value ranging from approximately 0.1 to 0.05.
11. The computer software program of claim 9 , the program steps further comprising:
comparing measured relative scattering characteristics to expected values for a range of shielding conditions to yield the estimated attenuation factor.
12. The computer software program of claim 9 , the program steps further comprising:
estimating the attenuation factor using the parameterized relationship of the following characterization equation:
Attenuation
Factor
=
ⅇ
Slope
(
%
Fraction
-
Offset
)
,
where
Offset
=
AF
[
6
]
×
Energy
AF
[
7
]
Slope
=
{
AF
[
1
]
+
AF
[
2
]
×
ⅇ
AF
[
3
]
×
Energy
,
Energy
<
500
keV
AF
[
4
]
+
AF
[
5
]
×
Energy
,
Energy
≥
500
keV
.
13. The method of claim 9 , wherein the threshold is derived using the detector device intrinsic peak-to-total calibration value applicable for, an unshielded source.
14. The method of claim 9 , the method steps further comprising:
analyzing the energy dependent scattering differential response by comparing measured relative scattering characteristics to expected values for a range of shielding conditions to yield the estimated attenuation factor.
15. The method of claim 9 wherein the threshold is derived from a worst case energy calculation for the nuclide.
16. The method of claim 9 wherein the threshold is indexed by the weighted average energy of the spectrum photopeaks for the nuclide.
17. A method of analyzing measured radiation spectra to determine an estimated nuclide attenuation factor for use in nuclide activity measurements, the method steps comprising:
obtaining a whole spectrum peak-to-total counts ratio for at least one nuclide source from at least one radiation detector spectrometer device;
calculating a photopeak scattering metric on a per nuclide photopeak basis using the amount of excess counts in the scattered continuum regions immediately below and immediately above the peak energy region, relative to the net peak area for the nuclide; and
indexing the photopeak scattering metric by energy to an expected shielding response function to yield an estimated attenuation factor to correct the nuclide activity measurements.
18. The method of claim 17 , the method steps further comprising:
comparing the whole spectrum peak-to-total counts ratio to a general threshold to determine the presence of significant shielding.
19. The method of claim 18 , wherein the threshold is derived using the detector device intrinsic peak-to-total calibration value applicable for an unshielded source.
20. The method of claim 18 wherein the threshold is derived from a worst case energy calculation for the nuclide.
21. The method of claim 18 wherein the threshold is indexed by the weighted average energy of the spectrum photopeaks for the nuclide.
22. The method of claim 17 , the method steps further comprising:
comparing measured relative scattering characteristics to expected values for a range of shielding conditions to yield the estimated attenuation factor.
23. The method of claim 17 , the method steps further comprising:
estimating the attenuation factor using the parameterized relationship of the following characterization equation:
Attenuation
Factor
=
ⅇ
Slope
(
%
Fraction
-
Offset
)
,
where
Offset
=
AF
[
6
]
×
Energy
AF
[
7
]
Slope
=
{
AF
[
1
]
+
AF
[
2
]
×
ⅇ
AF
[
3
]
×
Energy
,
Energy
<
500
keV
AF
[
4
]
+
AF
[
5
]
×
Energy
,
Energy
≥
500
keV
.
24. The method of claim 17 , the method steps further comprising:
analyzing the energy dependent scattering differential response by comparing measured relative scattering characteristics to expected values for a range of shielding conditions to yield the estimated attenuation factor.
25. A computer software program tangibly embodied in a computer readable medium, the program including machine-readable instructions executable by a computer processor to perform a method of analyzing measured, radiation spectra to determine an estimated nuclide attenuation factor for use in nuclide activity measurements, the program steps comprising:
obtaining a whole spectrum peak-to-total counts ratio for at least one nuclide source from at least one radiation detector spectrometer device;
calculating a photopeak scattering metric on a per nuclide photopeak basis using the amount of excess counts in the scattered continuum regions immediately below and immediately above the peak energy region, relative to the net peak area for the nuclide; and
indexing the photopeak scattering metric by energy to an expected shielding response function to yield an estimated attenuation factor to correct the nuclide activity measurements.
26. The computer software program of claim 25 , the program steps further comprising:
comparing the whole spectrum peak-to-total counts ratio to a general threshold to determine the presence of significant shielding.
27. The computer software program of claim 26 , wherein the threshold is derived using the detector device intrinsic peak-to-total calibration value applicable for an unshielded source.
28. The computer software program of claim 26 wherein the threshold is derived from a worst case energy calculation for the nuclide.
29. The computer software program of claim 26 wherein the threshold is indexed by the weighted average energy of the spectrum photopeaks for the nuclide.
30. The computer software program of claim 25 , the program steps further comprising:
comparing measured relative scattering characteristics to expected values for a range of shielding conditions to yield the estimated attenuation factor.
31. The computer software program of claim 25 , the program steps further comprising:
estimating the attenuation factor using the parameterized relationship of the following characterization equation:
Attenuation
Factor
=
ⅇ
Slope
(
%
Fraction
-
Offset
)
,
where
Offset
=
AF
[
6
]
×
Energy
AF
[
7
]
Slope
=
{
AF
[
1
]
+
AF
[
2
]
×
ⅇ
AF
[
3
]
×
Energy
,
Energy
<
500
keV
AF
[
4
]
+
AF
[
5
]
×
Energy
,
Energy
≥
500
keV
.
32. The computer software program of claim 25 , the program steps further comprising:
analyzing the energy dependent scattering differential response by comparing measured relative scattering characteristics to expected values for a range of shielding conditions to yield the estimated attenuation factor.