US4429226A — Method of and means for improving the resolution …

Claim 1

Independent Claim 173 words

In a gamma camera having a scintillation crystal responsive to radiation stimuli for producing light events at locations where the stimuli interact with the crystal, an array of photomultipliers responsive to a light event for producing individual outputs, circuitry responsive to said outputs for identifying the elemental area of the crystal within which an event occurs, and a matrix whose elements are in one-to-one correspondence with elemental areas of the crystal, the contents of each element in the matrix being incremented when identified by the circuitry and representing the number of events that have occurred within a predetermined period of time within an elemental area of the crystal corresponding to the location of the element in the matrix whereby the contents of the matrix represents the density distribution of light events in the crystal, the improvement comprising: weighting the contents of the elements in the matrix such that the weighted contents of the matrix more closely approaches the actual density distribution of light events as compared to the unweighted contents of the matrix.

Claim 2

Dependent Claim 173 words

In a gamma camera having a scintillation crystal responsive to radiation stimuli for producing light events at locations where the stimuli interact with the crystal, an array of photomultipliers responsive to a light event for producing individual outputs, circuitry responsive to said outputs for identifying the elemental area of the crystal within which an event occurs, and a matrix whose elements are in one-to-one correspondence with elemental areas of the crystal, the contents of each element in the matrix being incremented when identified by the circuitry and representing the number of events that have occurred within a predetermined period of time within an elemental area of the crystal corresponding to the location of the element in the matrix whereby the contents of the matrix represents the density distribution of light events in the crystal, the improvement comprising: weighting the contents of the elements in the matrix such that the weighted contents of the matrix more closely approaches the actual density distribution of light events as compared to the unweighted contents of the matrix.

Claim 3

Dependent Claim 38 words

The improvement of claim 1 wherein the contents of each element is weighted in accordance with the probability that an event, identified as having occurred in a given elemental area to which the element corresponds, actually occurred therein.

Claim 4

Dependent Claim 78 words

The improvement of claim 2 wherein a calibration procedure is utilized, such procedure involving sequentially impinging a calibration beam of gamma rays on each elemental area of the crystal and calculating, for each elemental area, the calibration distance between the actual location of a light event and the location of the event based on the computation circuitry, and selecting for each elemental area of the crystal a confidence factor functionally related to the inverse of the calibration distance.

Claim 5

Dependent Claim 145 words

An improved gamma camera comprising: (a) a camera head including a scintillation crystal responsive to radiation stimuli from a radiation field for producing light events at locations where the stimuli interact with the crystal, and an array of photodetectors responsive to a light event for producing individual outputs; (b) circuitry for processing the individual outputs to identify the elemental area of the crystal within which an event occurs; (c) a storage matrix whose elements are in one-to-one correspondence with the elemental areas of the crystal, the contents of each element in the crystal representing the number of events identified as having occurred within a predetermined period of time within an elemental area of the crystal corresponding to the location of the element in the matrix; and (d) means weighting the contents of the elements in the storage matrix for improving the resolution of the camera.

Claim 6

Dependent Claim 145 words

An improved gamma camera comprising: (a) a camera head including a scintillation crystal responsive to radiation stimuli from a radiation field for producing light events at locations where the stimuli interact with the crystal, and an array of photodetectors responsive to a light event for producing individual outputs; (b) circuitry for processing the individual outputs to identify the elemental area of the crystal within which an event occurs; (c) a storage matrix whose elements are in one-to-one correspondence with the elemental areas of the crystal, the contents of each element in the crystal representing the number of events identified as having occurred within a predetermined period of time within an elemental area of the crystal corresponding to the location of the element in the matrix; and (d) means weighting the contents of the elements in the storage matrix for improving the resolution of the camera.

Claim 7

Dependent Claim 49 words

A gamma camera according to claim 4 where the means weighting the contents of the elements of the storage matrix includes a correction matrix whose elements are in one-to-one correspondence with the elements of the storage matrix, the contents of the elements in the correction matrix constituting the weights.

Claim 8

Dependent Claim 43 words

A gamma camera according to claim 5 wherein the weight of an element of the correction matrix is in accordance with the probability that an event, identified as having occurred in a given elemental area to which the element corresponds, actually occurred therein.

Claim 9

Dependent Claim 23 words

A gamma camera according to claim 5 including means for multiplying the contents of corresponding elements of the storage matrix and correction matrix.

Claim 10

Independent Claim 166 words

A method for improving the resolution of a gamma camera having a scintillation crystal responsive to radiation stimuli from a radiation field for producing light events at locations where the stimuli interact with the crystal, an array of photodetectors responsive to a light event for producing individual outputs, and circuitry for processing the individual outputs to calculate the location of a light event, the method comprising: (a) sequentially impinging a calibration beam of gamma rays on each elemental area of the crystal; (b) using the circuitry for calculating the location of each light event; (c) deriving the average location of events due to impingement of the calibration beam on a given elemental area; (d) calculating the distance between the actual location of events and the average location for each elemental area to establish a calibration distance associated with the elemental area; and (e) assigning a confidence factor to an event in a given elemental area in accordance with the calibration distance associated with the elemental area.

Claim 11

Independent Claim 166 words

A method for improving the resolution of a gamma camera having a scintillation crystal responsive to radiation stimuli from a radiation field for producing light events at locations where the stimuli interact with the crystal, an array of photodetectors responsive to a light event for producing individual outputs, and circuitry for processing the individual outputs to calculate the location of a light event, the method comprising: (a) sequentially impinging a calibration beam of gamma rays on each elemental area of the crystal; (b) using the circuitry for calculating the location of each light event; (c) deriving the average location of events due to impingement of the calibration beam on a given elemental area; (d) calculating the distance between the actual location of events and the average location for each elemental area to establish a calibration distance associated with the elemental area; and (e) assigning a confidence factor to an event in a given elemental area in accordance with the calibration distance associated with the elemental area.

Claim 12

Dependent Claim 20 words

A method according to claim 8 wherein the confidence factor is functionally related to the inverse of the calibration distance.

Claim 13

Dependent Claim 139 words

In a nuclear imaging device having a scintillation crystal responsive to radiation stimuli for producing light events at locations where the stimuli interact with the crystal, an array of photodetectors responsive to a light event for producing a set of individual outputs, circuitry responsive to respective sets of said outputs for computing the coordinates of events, and a matrix whose elements are in one-to-one correspondence with elemental areas of the crystal for recording a representation of the occurrences of events at their calculated coordinates whereby the contents of the matrix represents the density distribution of light events in the crystal, the improvement comprising: weighting the contents of the elements in the memory such that the weighted contents of the memory more closely approaches the actual density distribution of light events as compared to the unweighted contents of the memory.

Claim 14

Dependent Claim 139 words

In a nuclear imaging device having a scintillation crystal responsive to radiation stimuli for producing light events at locations where the stimuli interact with the crystal, an array of photodetectors responsive to a light event for producing a set of individual outputs, circuitry responsive to respective sets of said outputs for computing the coordinates of events, and a matrix whose elements are in one-to-one correspondence with elemental areas of the crystal for recording a representation of the occurrences of events at their calculated coordinates whereby the contents of the matrix represents the density distribution of light events in the crystal, the improvement comprising: weighting the contents of the elements in the memory such that the weighted contents of the memory more closely approaches the actual density distribution of light events as compared to the unweighted contents of the memory.

Claim 15

Dependent Claim 40 words

The improvement of claim 10 wherein the contents of each element is weighted in accordance with a measure of the probability that events, identified as having occurred in a given elemental area to which the element corresponds, actually occurred therein.

Claim 16

Dependent Claim 77 words

The improvement of claim 11 wherein a calibration procedure is utilized, such procedure involving sequentially impinging a calibration beam of gamma rays on elemental areas of the crystal and calculating, for each elemental area, the calibration distance between the actual location of a light event and the location of the event based on the computation circuitry, and selecting for each elemental area of the crystal a confidence factor functionally related to the inverse of the calibration distance.

Claim 17

Independent Claim 136 words

A method for using a gamma camera having a scintillation crystal responsive to radiation stimuli from a radiation field for producing light events at locations where the stimuli interact with the crystal, an array of photodetectors responsive to a light event for producing a distribution of individual outputs, and computation circuitry responsive the distribution of outputs produced by the occurrence of an event for calculating its coordinates, the method comprising: (a) calculating the coordinates of an event from the actual distribution of outputs produced by the photodetectors when a light event occurs in the crystal; (b) associating with the calculated coordinates an average distribution of outputs of the photodetectors representative of the distribution due to the occurrence of a number of events at said calculated coordinates; and (c) cross-correlating the average distribution with said actual distribution.

Claim 18

Independent Claim 136 words

A method for using a gamma camera having a scintillation crystal responsive to radiation stimuli from a radiation field for producing light events at locations where the stimuli interact with the crystal, an array of photodetectors responsive to a light event for producing a distribution of individual outputs, and computation circuitry responsive the distribution of outputs produced by the occurrence of an event for calculating its coordinates, the method comprising: (a) calculating the coordinates of an event from the actual distribution of outputs produced by the photodetectors when a light event occurs in the crystal; (b) associating with the calculated coordinates an average distribution of outputs of the photodetectors representative of the distribution due to the occurrence of a number of events at said calculated coordinates; and (c) cross-correlating the average distribution with said actual distribution.

Claim 19

Dependent Claim 25 words

A method according to claim 13 wherein the average distribution is obtained analytically in accordance with the spatial distribution of the photodetectors on the crystal.

Claim 20

Dependent Claim 41 words

A method according to claim 13 wherein the average distribution is obtained by a calibration process which includes creating a number of events at each of a plurality of locations, and recording the average distribution of outputs for each known location.

Claim 21

Dependent Claim 36 words

A method according to claim 15 wherein the average distribution at the location defined by the calculated coordinates is obtained by interpolation using average distributions at known locations adjacent the location defined by the calculated coordinates.

Claim 22

Dependent Claim 39 words

A method according to claim 15 wherein the known locations are within one motif of a repeated pattern of the array of photodetectors, and the average distribution for locations in other motifs of the pattern are obtained by similarity.

Claim 23

Dependent Claim 32 words

A method according to claim 13 including recording in a memory, at a location determined by the calculated coordinates, a representation of the probability that an event occurred at the calculated coordinates.

Claim 24

Dependent Claim 13 words

A method according to claim 18 including displaying the contents of the memory.

Claim 25

Dependent Claim 87 words

A gamma camera comprising: (a) a gamma camera including a scintillation crystal responsive to radiation stimuli from a radiation field for producing light events at locations where the stimuli interact with the crystal, and an array of photodetectors responsive to a light event for producing a distribution of individual outputs; (b) computation circuitry responsive to the distribution of outputs produced by the occurrence of an event for calculating its coordinates; (c) means for evaluating the probability that the calculated coordinates of an event are its actual coordinates.

Claim 26

Dependent Claim 87 words

A gamma camera comprising: (a) a gamma camera including a scintillation crystal responsive to radiation stimuli from a radiation field for producing light events at locations where the stimuli interact with the crystal, and an array of photodetectors responsive to a light event for producing a distribution of individual outputs; (b) computation circuitry responsive to the distribution of outputs produced by the occurrence of an event for calculating its coordinates; (c) means for evaluating the probability that the calculated coordinates of an event are its actual coordinates.

Claim 27

Dependent Claim 39 words

A gamma camera according to claim 20 including a storage means for storing a representation of the occurrence of an event at its calculated coordinates taking into account the probability that such event actually occurred at the calculated coordinates.

Claim 28

Dependent Claim 16 words

A gamma camera according to claim 21 including means for displaying the contents of said storage.

Claim 29

Dependent Claim 42 words

A gamma camera according to claim 20 including means for storing a representation of the radiation field in terms of the probability that the calculated coordinates of events produced in the crystal by the radiation field actually occurred at the calculated coordinates.

Claim 30

Dependent Claim 18 words

A gamma camera according to claim 23 including means for displaying the stored representation of the radiation field.

Claim 31

Dependent Claim 42 words

A gamma camera according to claim 20 wherein the means for evaluating includes correlation means for cross-correlating a distribution of outputs of the photodetectors caused by an event with a reference distribution of outputs associated with the calculated coordinates of the event.

Claim 32

Dependent Claim 42 words

A gamma camera according to claim 25 wherein the means for evaluating includes a memory for recording, at a location established by the calculated cordinates of an event, an increment whose value is functionally related to the output of the correlation means.

Claim 33

Dependent Claim 43 words

A gamma camera according to claim 26 wherein the memory is a matrix, and recording is carried out by incrementing the memory at the address specified by the calculated coordinates of the event with a function of the output of the correlation means.

Claim 34

Dependent Claim 37 words

A gamma camera according to claim 27 wherein the memory is incemented at addresses adjacent the address specified by said calculated coordinate with a function of the output of the correlation means evaluated at the adjacent addresses.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1987-01-30	1987-08-01	1988-01-31	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1991-01-30	1991-08-01	1992-01-31	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1995-01-30	1995-08-01	1996-01-31	$7700.00	Window Closed / Lapsed

Method of and means for improving the resolution of a gamma camera

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