Method for correcting the stacking phenomenon applied to X-ray spectrums acquired using a spectrometric sensor

Patent metadata

Field	Value
Publication number	US-9689994-B2
Application number	US-201013512485-A
Country	US
Kind code	B2
Filing date	Nov 30, 2010
Priority date	Nov 30, 2009
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

A method correcting a measured spectrum of X radiation, according to a number of channels Nc, each channel i corresponding to an energy range between E i and Ei+ΔE i , including: determining function δt i,j (k) determining size of temporal deviation Δt interval separating two interactions with energy E i and E j , stacking of which leads to a detected energy value E k ; determining, from the function δt i,j (k), probability function P i,j (k) that an event counted in a channel k corresponds to a stack of two interactions, respectively of energies E i and E j ; determining, from the probability function P i,j (k), a stack spectrum as a part of the measured spectrum that corresponds only to the stacks alone; and calculating or estimating at least a first corrected spectrum, by the difference between the measured spectrum and the stack spectrum.

First claim

The invention claimed is:

1. A method for correcting a measured spectrum of X radiation according to a number of channels Nc, each channel i corresponding to an energy range between E i and E i +ΔE i , comprising:
determining, using processing circuitry, a function δt i,j (k), which defines a size of a temporal deviation Δt interval, such that two interactions with energy E i and E j temporally separated by Δt are stacked and considered to have a detected energy value E k ;
determining, using the processing circuitry, from the function δt i,j (k), a probability function P i,j (k) that an event counted in a channel k corresponds to a stack of two interactions, respectively, of energies E i and E j ;
calculating, using the processing circuitry, from the probability function P i,j (k), a stack spectrum, which is a part of the measured spectrum that corresponds only to the stack; and
adjusting, using the processing circuitry, the measured spectrum based on a difference between the measured spectrum and the calculated stack spectrum thus forming at least a first corrected spectrum accounting for perturbations present in the measured spectrum due to a stacking phenomenon.

2. The method according to claim 1 , the stack spectrum being calculated from the measured spectrum, exposure time, dead time data, and a minimum duration, separating two photons, below which there is stacking of the two photons and only one of the two photons is detected.

3. The method according to claim 2 , the dead time being determined by simulation or experimentally.

4. The method according to claim 1 , further comprising iteratively calculating N it (N it ≧1) corrected spectrums, each iteration calculating a corrected spectrum of order (n) from a corrected spectrum of order (n−1) or from the measured spectrum if there is no preceding corrected spectrum of order (n−1), by calculating a difference between the corrected spectrum of order (n−1), or the measured spectrum, and the stack spectrum, wherein 1≦n≦N it , n is an integer, and N it corresponds to a number of iterations of said calculating.

5. The method according to claim 4 , further comprising, iterated N it times, with N it ≧1:
calculating, using processing circuitry, a mean stacking probability, as a function of a preceding corrected spectrum Sp cor(n-1) , or of the measured spectrum if there is no preceding corrected spectrum, and exposure time and dead time data;
estimating, using processing circuitry, the stack spectrum, as a function of the preceding corrected spectrum, or of the measured spectrum if there is no preceding corrected spectrum, and the exposure time; and
calculating, using processing circuitry, the corrected spectrum, using the difference between a preceding corrected spectrum or the measured spectrum, and the estimated stack spectrum.

6. The method according to claim 5 , the mean stacking probability being calculated using formula:

P
mean

=

1
-

(

1
-

2
×

T
dead

T
expo

)

∑

j
=
1

N
⁢

⁢
max

⁢

Sp

cor
⁡

(

n
-
1

)

⁡

(
j
)

where Sp cor(n-1) (j) is the value, for the channel j, of the preceding corrected spectrum SP cor(n-1) , or of the measured spectrum if there is no preceding corrected spectrum.

7. The method according to claim 1 , the stack spectrum being calculated using formula:

Emp
⁢

(
k
)

=

∑

i
=
1

Nc

⁢

∑

j
=
i

Nc

⁢

P

i
,
j

⁡

(
k
)

.

8. The method according to claim 7 , wherein:

P

i
,
j

⁡

(
k
)

=

1
-

[

1
-

2
×
δ
⁢

⁢

t

i
,
j

⁡

Assignees

• Rinkel Jean
• Brambilla Andrea
• Dinten Jean-Marc
• Mougel Florent
• Commissariat L Energie Atomique Et Aux Energies Alternatives

Inventors

• Rinkel Jean
• Brambilla Andrea
• Dinten Jean-Marc
• Mougel Florent

Classifications

• G01T1/171 Primary

  Compensation of dead-time counting losses · CPC title