Library generation for detection and identification of shielded radioisotopes
View Patent ↗A method, logic and system are provided for generating data representing all possible materials that may be present when monitoring a region or space for a radioisotope of interest. All possible materials with which a radioisotope material may interact are grouped or categorized into one of a plurality of material groups. Each material group is further subdivided into a plurality of subgroups based on atomic number of a material. First data is stored for each of the subgroups of each of the plurality of material groups, where the first data represents an interaction between a representative material for a corresponding subgroup and radiation at a plurality of energy levels. Second data is stored representing spectral characteristics of each radioisotope of interest at the plurality of energy levels. For a radioisotope of interest, a computation is made to produce spectrum data resulting from an interaction between of the radioisotope of interest using the second data with the first data for each of the plurality of subgroups in each material group. The spectrum data is then stored in a library for later use in the field with the output from a detector. Spectrum data is stored for the particular detector to be used in the field, and to this end, such detector-specific spectrum library data may be adjusted to account for a detector's quantum efficiency and resolution characteristics.
1. A method for determining and indicating the presence of a radioisotope threat, the method comprising:
at a computer device, receiving spectral data associated with a region or space captured by a detector for detecting radioisotopes;
adjusting the captured spectral data by quantum efficiency values of a quantum efficiency value matrix based on the detector;
comparing the adjusted spectral data with library stored spectral data, the library stored spectral data being created by:
grouping possible materials with which a radioisotope interacts into one of a plurality of material groups;
subdividing each of the plurality of material groups into a plurality of subgroups based on atomic number and/or electron affinity of a material;
generating first data for each of the subgroups of each of the plurality of material groups, wherein the first data comprises a plurality of values each represents an interaction between a selected representative material for a corresponding subgroup and radiation at one of a plurality of energy levels;
generating second data representing spectral characteristics of each radioisotope of interest at the plurality of energy levels; and
for each radioisotope of interest, computing spectrum data representing an interaction between the radioisotope of interest using the second data with the first data for each of the plurality of subgroups in each material group to create library stored spectral data to be stored in a library; and
based on the comparison, generating either a signal indicating a threat or generating a signal indicating a non-threat.
2. The method of claim 1 , wherein computing the spectrum data further comprises computing interaction between the second data for each radioisotope of interest and the first data for one or more combinations of the plurality of subgroups.
3. The method of claim 1 , wherein adjusting the captured spectral data further comprises adjusting the captured spectral data for resolution of the detector.
4. The method of claim 1 , wherein generating the first data further comprises generating data for a matrix for each subgroup in a material group, wherein the matrix represents an interaction between radiation and a material that is grouped into that subgroup at the plurality of energy levels.
5. The method of claim 4 , wherein generating the data for the matrix for each subgroup in a material group further comprises generating a matrix M, where
M
=
[
E
1
,
1
E
1
,
2
E
i
,
j
…
E
1
,
n
E
2
,
1
E
2
,
2
…
E
2
,
n
…
…
…
…
E
n
,
n
]
,
in which E i,j represents the Monte Carlo Neutron and Photon (MCNP)-calculated value at an “i th ” row representing one of the energy levels and a “j th ” column representing a representative material in one of the subgroups, wherein the MCNP calculated value results from transport of a mono-energetic source of energy E i through the material.
6. The method of claim 5 , wherein generating the second data comprises generating data for a vector {right arrow over (β)} for each radioisotope of interest that represents a spectrum of radioisotope of interest in a vacuum, where
β
→
=
[
a
1
a
2
…
a
n
]
,
and a 1 , a 2 , . . . , a n are spectrum amplitude in energy bins E 1 , . . . E n , respectively.
7. The method of claim 6 , wherein computing the spectrum data further comprises computing P=M{right arrow over (β)} where P is the spectrum data.
8. The method of claim 7 , wherein computing the spectrum data further comprises computing the spectrum data for the interaction of a material of a density ρ and a thickness r as P=M Γ {right arrow over (β)}, where Γ=αρr, and α is a non-negative integer.
9. The method of claim 8 , wherein computing the spectrum data further comprises computing interaction between a single radioisotope and each of the subgroups comprises computing
P
=
∏
j
∈
κ
M
j
Γ
j
β
→
,
where κ is a set material matrices M j for all of the subgroups j across all the material groups.
10. The method of claim 9 , wherein computing the spectrum data further comprises computing interaction between a plurality of radioisotopes of interest and each of the subgroups comprises computing
P
=
∑
i
=
1
J
δ
i
∏
j
∈
κ
M
j
Γ
j
β
→
i
,
where δ i is a weighted fraction of the radiation by each of the individual J radioisotope of interest represented {right arrow over (β)} i .
11. The method of claim 1 , further comprising identifying the radioisotope of interest by name or other identifier when a signal indicating a threat is generated.
12. One or more non-transitory processor-readable media encoded with instructions to determine and indicate presence of a radioisotope threat that, when executed by a processor, cause the processor to:
receive spectral data associated with a region or space captured by a detector for detecting radioisotopes;
adjust the captured spectral data by quantum efficiency values of a quantum efficiency value matrix based on the detector;
compare the adjusted spectral data with library stored spectral data, the library stored spectral data being created by:
grouping possible materials with which a radioisotope interacts into one of a plurality of material groups;
subdividing each of the plurality of material groups into a plurality of subgroups based on atomic number and/or electron affinity of a material;
generating first data for each of the subgroups of each of the plurality of material groups, wherein the first data comprises a plurality of values each represents an interaction between a selected representative material for a corresponding subgroup and radiation at one of a plurality of energy levels;
generating second data representing spectral characteristics of each radioisotope of interest at the plurality of energy levels; and
for each radioisotope of interest, computing spectrum data representing an interaction between the radioisotope of interest using the second data with the first data for each of the plurality of subgroups in each material group to create library stored spectral data to be stored in a library; and
based on the comparison, generate either a signal indicating a threat or generating a signal indicating a non-threat.
13. The one or more non-transitory processor-readable media of claim 12 , wherein instructions for computing the spectrum data comprises instructions for computing interaction between the second data for each radioisotope of interest and the first data for one or more combinations of the plurality of subgroups.
14. The one or more non-transitory processor-readable media of claim 12 , wherein instructions for adjusting the captured spectral data further comprises adjusting the captured spectral data for resolution of the detector.
15. The one or more non-transitory processor-readable media of claim 12 , wherein instructions for generating the first data comprises instructions for generating a matrix for each subgroup in a material group, wherein the matrix represents an interaction between radiation and a material that is grouped into that subgroup at the plurality of energy levels.
16. The one or more non-transitory processor-readable media of claim 15 , wherein instructions for generating the matrix for each subgroup in a material group further comprises instruction for generating a matrix M, where
M
=
[
E
1
,
1
E
1
,
2
E
i
,
j
…
E
1
,
n
E
2
,
1
E
2
,
2
…
E
2
,
n
…
…
…
…
E
n
,
n
]
,
in which E i,j represents the Monte Carlo Neutron and Photon (MCNP)-calculated value at an “i th ” row representing one of the energy levels and a “j th ” column representing a representative material in one of the subgroups, wherein the MCNP calculated value results from transport of a mono-energetic source of energy E i through the material.
17. The one or more non-transitory processor-readable media of claim 16 , wherein instructions for generating the second data further comprises instructions for generating data for a vector {right arrow over (β)} for each radioisotope of interest that represents a spectrum of radioisotope of interest in a vacuum, where
β
→
=
[
a
1
a
2
…
a
n
]
,
and a 1 , a 2 , . . . , a n are spectrum amplitude in energy bins E 1 , . . . E n , respectively.
18. The one or more non-transitory processor-readable media of claim 17 , wherein instructions for computing the spectrum data further comprises instructions for computing P=M{right arrow over (β)} where P is the spectrum data.
19. The one or more non-transitory processor-readable media of claim 18 , wherein the logic for computing the spectrum data further comprises instructions for computing the spectrum data for the interaction of a material of a density ρ and a thickness r as P=M Γ {right arrow over (β)}, where Γ=αρr, and α is a non-negative integer.
20. The one or more non-transitory processor-readable media of claim 19 , wherein instructions for computing the spectrum data further comprises instructions for computing interaction between a plurality of radioisotopes of interest and each of the subgroups comprises computing
P
=
∑
i
=
1
J
δ
i
∏
j
∈
κ
M
j
Γ
j
β
→
i
,
where δ i is a weighted fraction of the radiation by each of the individual J radioisotope of interest represented {right arrow over (β)} i .
21. A system for determining and indicating the presence of a radioisotope threat, comprising:
a memory storing computer executable instructions; and
a computer processor coupled to the memory and configured to execute the computer executable instructions to:
adjust the captured spectral data by quantum efficiency values of a quantum efficiency value matrix based on the detector;
compare the adjusted spectral data with library stored spectral data, the library stored spectral data being created by:
grouping possible materials with which a radioisotope interacts into one of a plurality of material groups;
subdividing each of the plurality of material groups into a plurality of subgroups based on atomic number and/or electron affinity of a material;
generating first data for each of the subgroups of each of the plurality of material groups, wherein the first data comprises a plurality of values each represents an interaction between a selected representative material for a corresponding subgroup and radiation at one of a plurality of energy levels;
generating second data representing spectral characteristics of each radioisotope of interest at the plurality of energy levels; and
for each radioisotope of interest, computing spectrum data representing an interaction between the radioisotope of interest using the second data with the first data for each of the plurality of subgroups in each material group to create library stored spectral data to be stored in a library; and
based on the comparison, generate either a signal indicating a threat or generating a signal indicating a non-threat.
22. The system of claim 21 , wherein computing the spectrum data further comprises computing interaction between the second data for each radioisotope of interest and the first data for one or more combinations of the plurality of subgroups.
23. The system of claim 21 , wherein to adjust the captured spectral data further comprises to adjust the captured spectral data for resolution of the detector.
24. The system of claim 21 , wherein generating the first data further comprises generating data for a matrix for each subgroup in a material group, wherein the matrix represents an interaction between radiation and a material that is grouped into that subgroup at the plurality of energy levels.
25. The system of claim 24 , wherein generating the data for the matrix for each subgroup in a material group further comprises generating a matrix M, where
M
=
[
E
1
,
1
E
1
,
2
E
i
,
j
…
E
1
,
n
E
2
,
1
E
2
,
2
…
E
2
,
n
…
…
…
…
E
n
,
n
]
,
in which E i,j represents the Monte Carlo Neutron and Photon (MCNP)-calculated value at an “i th ” row representing one of the energy levels and a “j th ” column representing a representative material in one of the subgroups, wherein the MCNP calculated value results from transport of a mono-energetic source of energy E i through the material.