Signal processing method for gamma-ray semiconductor sensor

Claim 1

A method of estimating spatial and energy parameters of gamma rays interacting with a semiconductor detector, wherein a slab of semiconductor material is positioned in a field of view of an aperture imaging system to receive gamma rays from a gamma-ray emitting source, said semiconductor material being capable of absorbing incident gamma rays; wherein said slab of semiconductor material is subjected to an electric field between an electrode attached to a side of the slab exposed to radiation and a plurality of electrodes attached to another side of the slab, whereby the slab is partitioned into a corresponding plurality of sensor-cell pixels individually capable of producing an electric current pulse when a gamma ray is absorbed within a pixel; wherein a monolithic multiplexer is coupled to said plurality of electrodes for the read-out of electric pulses generated in each of said pixels as a result of gamma-ray absorption events; and wherein the current-pulse output of each pixel is integrated during each step of operation of said monolithic multiplexer by accumulation in a corresponding capacitor means that is discharged at predetermined times producing a voltage signal through a single-output channel of the multiplexer and that is then reset for charging during a next step of operation; said method comprising the following steps: (a) comparing said voltage signal for each pixel to a corresponding predetermined threshold signal and identifying all pixels having an above-threshold voltage signal; (b) identifying clusters of adjacent pixels having above-threshold voltage signals and selecting a pixel within each cluster as a central pixel for the cluster; (c) summing all voltage signals of adjacent pixels within a predetermined range of said central pixel to produce a cumulative voltage signal for the cluster and assigning said cumulative voltage signal to the central pixel of the cluster; and (d) processing the cumulative voltage signal generated in step (c) for each cluster as an output signal associated with a spatial coordinate of said corresponding central pixel for constructing an image of the gamma-ray emitting source.

Claim 2

A method of estimating spatial and energy parameters of gamma rays interacting with a semiconductor detector, wherein a slab of semiconductor material is positioned in a field of view of an aperture imaging system to receive gamma rays from a gamma-ray emitting source, said semiconductor material being capable of absorbing incident gamma rays; wherein said slab of semiconductor material is subjected to an electric field between an electrode attached to a side of the slab exposed to radiation and a plurality of electrodes attached to another side of the slab, whereby the slab is partitioned into a corresponding plurality of sensor-cell pixels individually capable of producing an electric current pulse when a gamma ray is absorbed within a pixel; wherein a monolithic multiplexer is coupled to said plurality of electrodes for the read-out of electric pulses generated in each of said pixels as a result of gamma-ray absorption events; and wherein the current-pulse output of each pixel is integrated during each step of operation of said monolithic multiplexer by accumulation in a corresponding capacitor means that is discharged at predetermined times producing a voltage signal through a single-output channel of the multiplexer and that is then reset for charging during a next step of operation; said method comprising the following steps: (a) comparing said voltage signal for each pixel to a corresponding predetermined threshold signal and identifying all pixels having an above-threshold voltage signal; (b) identifying clusters of adjacent pixels having above-threshold voltage signals and selecting a pixel within each cluster as a central pixel for the cluster; (c) summing all voltage signals of adjacent pixels within a predetermined range of said central pixel to produce a cumulative voltage signal for the cluster and assigning said cumulative voltage signal to the central pixel of the cluster; and (d) processing the cumulative voltage signal generated in step (c) for each cluster as an output signal associated with a spatial coordinate of said corresponding central pixel for constructing an image of the gamma-ray emitting source.

Claim 7

A method of estimating spatial-coordinate and energy parameters of gamma rays interacting with a semiconductor detector for which a probability distribution is known relating spatial and energy parameters of each interaction event, wherein a slab of semiconductor material is positioned in a field of view of an aperture imaging system to receive gamma rays from a gamma-ray emitting source, said semiconductor material being capable of absorbing incident gamma rays; wherein said slab of semiconductor material is subjected to an electric field between an electrode attached to a side of the slab exposed to radiation and a plurality of electrodes attached to another side of the slab, whereby the slab is partitioned into a corresponding plurality of sensor-cell pixels individually capable of producing an electric current pulse when a gamma ray is absorbed within a pixel; wherein a monolithic multiplexer is coupled to said plurality of electrodes for the read-out of electric pulses generated in each of said pixels as a result of gamma-ray absorption events; and wherein the current-pulse output of each pixel is integrated during each step of operation of said monolithic multiplexer by accumulation in a corresponding capacitor means that is discharged at predetermined times producing a voltage signal through a single-output channel of the multiplexer and that is then reset for charging during a next step of operation; said method comprising the following steps: (a) comparing said voltage signal for each pixel to a corresponding predetermined threshold signal and identifying all pixels having an above-threshold voltage signal; (b) identifying clusters of adjacent pixels having above-threshold voltage signals; and, for each such cluster, recording the voltage signal and coordinate position of a predetermined number of adjacent pixels within a predetermined range of pixels intersecting said cluster; (c) utilizing said probability distribution for gamma rays interacting with the semiconductor detector to calculate a maximum-likelihood estimate of a spatial coordinate and an energy level for each gamma-ray interaction event recorded within each cluster; and (d) processing the spatial coordinate and energy level for each recorded gamma-ray interaction event generated in step (c) for each cluster as output signals for constructing an image of the gamma-ray emitting source.

Claim 8

A method of estimating spatial-coordinate and energy parameters of gamma rays interacting with a semiconductor detector for which a probability distribution is known relating spatial and energy parameters of each interaction event, wherein a slab of semiconductor material is positioned in a field of view of an aperture imaging system to receive gamma rays from a gamma-ray emitting source, said semiconductor material being capable of absorbing incident gamma rays; wherein said slab of semiconductor material is subjected to an electric field between an electrode attached to a side of the slab exposed to radiation and a plurality of electrodes attached to another side of the slab, whereby the slab is partitioned into a corresponding plurality of sensor-cell pixels individually capable of producing an electric current pulse when a gamma ray is absorbed within a pixel; wherein a monolithic multiplexer is coupled to said plurality of electrodes for the read-out of electric pulses generated in each of said pixels as a result of gamma-ray absorption events; and wherein the current-pulse output of each pixel is integrated during each step of operation of said monolithic multiplexer by accumulation in a corresponding capacitor means that is discharged at predetermined times producing a voltage signal through a single-output channel of the multiplexer and that is then reset for charging during a next step of operation; said method comprising the following steps: (a) comparing said voltage signal for each pixel to a corresponding predetermined threshold signal and identifying all pixels having an above-threshold voltage signal; (b) identifying clusters of adjacent pixels having above-threshold voltage signals; and, for each such cluster, recording the voltage signal and coordinate position of a predetermined number of adjacent pixels within a predetermined range of pixels intersecting said cluster; (c) utilizing said probability distribution for gamma rays interacting with the semiconductor detector to calculate a maximum-likelihood estimate of a spatial coordinate and an energy level for each gamma-ray interaction event recorded within each cluster; and (d) processing the spatial coordinate and energy level for each recorded gamma-ray interaction event generated in step (c) for each cluster as output signals for constructing an image of the gamma-ray emitting source.

Claim 14

A method of estimating a spatial and an energy distribution of a fluence of gamma rays interacting with a semiconductor detector when a probability distribution is known relating spatial and energy parameters of each interaction event, wherein a slab of semiconductor material is positioned in a field of view of an aperture imaging system to receive gamma rays from a gamma-ray emitting source, said semiconductor material being capable of absorbing incident gamma rays; wherein said slab of semiconductor material is subjected to an electric field between an electrode attached to a side of the slab exposed to radiation and a plurality of electrodes attached to another side of the slab, whereby the slab is partitioned into a corresponding plurality of sensor-cell pixels individually capable of producing an electric current pulse when a gamma ray is absorbed within a pixel; wherein a monolithic multiplexer is coupled to said plurality of electrodes for the read-out of electric pulses generated in each of said pixels as a result of gamma-ray absorption events; and wherein the current-pulse output of each pixel is integrated during each step of operation of said monolithic multiplexer by accumulation in a corresponding capacitor means that is discharged at predetermined times producing a voltage signal through a single-output channel of the multiplexer and that is then reset for charging during a next step of operation; said method comprising the following steps: (a) comparing said voltage signal for each pixel to a corresponding predetermined threshold signal and identifying all pixels having an above-threshold voltage signal; (b) identifying clusters of adjacent pixels having above-threshold voltage signals and recording the voltage signal and coordinate position of a predetermined number of adjacent pixels within a predetermined range of pixels intersecting said cluster; (c) utilizing said probability distribution for gamma rays interacting with the semiconductor detector to calculate a maximum-likelihood estimate of a spatial distribution and an energy distribution of a fluence of recorded gamma-ray interaction events; and (d) processing said spatial distribution and energy distribution of a fluence of recorded gamma-ray interaction events generated in step (c) for constructing an image of the gamma-ray emitting source.

Claim 15

A method of estimating a spatial and an energy distribution of a fluence of gamma rays interacting with a semiconductor detector when a probability distribution is known relating spatial and energy parameters of each interaction event, wherein a slab of semiconductor material is positioned in a field of view of an aperture imaging system to receive gamma rays from a gamma-ray emitting source, said semiconductor material being capable of absorbing incident gamma rays; wherein said slab of semiconductor material is subjected to an electric field between an electrode attached to a side of the slab exposed to radiation and a plurality of electrodes attached to another side of the slab, whereby the slab is partitioned into a corresponding plurality of sensor-cell pixels individually capable of producing an electric current pulse when a gamma ray is absorbed within a pixel; wherein a monolithic multiplexer is coupled to said plurality of electrodes for the read-out of electric pulses generated in each of said pixels as a result of gamma-ray absorption events; and wherein the current-pulse output of each pixel is integrated during each step of operation of said monolithic multiplexer by accumulation in a corresponding capacitor means that is discharged at predetermined times producing a voltage signal through a single-output channel of the multiplexer and that is then reset for charging during a next step of operation; said method comprising the following steps: (a) comparing said voltage signal for each pixel to a corresponding predetermined threshold signal and identifying all pixels having an above-threshold voltage signal; (b) identifying clusters of adjacent pixels having above-threshold voltage signals and recording the voltage signal and coordinate position of a predetermined number of adjacent pixels within a predetermined range of pixels intersecting said cluster; (c) utilizing said probability distribution for gamma rays interacting with the semiconductor detector to calculate a maximum-likelihood estimate of a spatial distribution and an energy distribution of a fluence of recorded gamma-ray interaction events; and (d) processing said spatial distribution and energy distribution of a fluence of recorded gamma-ray interaction events generated in step (c) for constructing an image of the gamma-ray emitting source.