Energy window selection for a radiation signal processing system

Claim 3

A method as claimed in claim 1 further comprising converting the corrected spatial positions of the elements to apparent spatial positions and storing the energy level window values so as to be accessible by the apparent positions of detected radiation events.

Claim 4

A method as claimed in claim 1 or 2 wherein the step of determining the energy level distributions comprises determining an energy histogram by counting the radiation events at each of a plurality of discrete energy levels within each corrected spatial element.

Claim 5

A method as claimed in claim 3 comprising determining the peak centroid of each histogram; defining an energy window about the peak centroid for at least one element to set a standard number of acceptable energy events for all the elements; and adapting the energy window of each remaining element to cause each element to accept a count of radiation events substantially equal to the standard.

Claim 6

A method as claimed in claim 4 wherein the adapting step includes determining for each element whether the window must be widened or narrowed and then progressively adjusting the window in the appropriate direction.

Claim 7

Radiation imaging apparatus comprising: (a) detector means capable of producing an output signal representing the corrected orthogonal spatial coordinates and energy level of a radiation event; (b) means for determining the energy level distribution of corrected radiation events within each of a plurality of corrected spatial elements; and (c) means for determining for each of said elements the energy window to be accepted in response to a flood image such that every element accepts substantially the same number of events.

Claim 8

Radiation imaging apparatus comprising: (a) detector means capable of producing an output signal representing the corrected orthogonal spatial coordinates and energy level of a radiation event; (b) means for determining the energy level distribution of corrected radiation events within each of a plurality of corrected spatial elements; and (c) means for determining for each of said elements the energy window to be accepted in response to a flood image such that every element accepts substantially the same number of events.

Claim 9

Apparatus as claimed in claim 6 wherein the detector means comprises means capable of producing an output signal representing apparent orthogonal spatial position coordinates and the associated energy level for each detected radiation event and means for translating detected events from their apparent spatial position to a corrected spatial position.

Claim 10

Apparatus as claimed in claim 6 or 7 wherein the means for determining the energy level distribution comprises means for obtaining a histogram of detected radiation events for each corrected spatial element in response to a flood image of known energy level.

Claim 11

Apparatus as claimed in claim 8 wherein the means for determining the energy windows comprises means for determining the point about which a photopeak is generally centered of each said histogram; means for defining an energy window about said point for at least one element to set a standard number of acceptable radiation events for the elements; and means for adapting the energy windows of the elements to cause each element to accept a count of radiation events substantially equal to the standard.

Claim 12

1 0. An improved signal processing system including improved calibration apparatus for use with a radiation imaging apparatus, comprising: (a) a radiation transducer for producing signals representative of the apparent orthogonal spatial coordinates and of the energy level of detected radiation events; (b) means operative in a spatial calibration mode for storing corrected spatial coordinates corresponding to a plurality of predetermined apparent spatial coordinates relative to selected detected radiation events; (c) means for translating apparent spatial coordinates to corrected spatial coordinates, said translating means communicating with said means for storing; (d) means for interpolating the corrected spatial coordinates of the detected radiation events occurring within the space bounded by said stored corrected spatial coordinates to produce precise corrected spatial coordinates; (e) means operative in an energy level calibration mode using coordinates derived from said translating means for obtaining a histogram for each corrected spatial element; (f) means operative in said energy level calibration mode for setting a window of acceptable energy levels; (g) means operative in said energy level calibration node for determining the number of counts in response to a flood image occurring within said window for each corrected spatial element; ; (h) means operative in said energy level calibration mode for progressively adapting the window for each element until all of said elements accept substantially the same number of counts in response to the flood image; (i) means operative in said energy level calibration node for storing one or more of said windows as a function of apparent spatial coordinates; (j) means for comparing the energy level of the transducer signals of the detected radiation events to the windows corresponding to the apparent spatial coordinates of the events; and (k) output means for producing an output signal, said output means being responsive to said transducer signals and to said comparing means so that only those transducer signals occurring within the windows contribute to form said output signal.

Claim 13

1 0. An improved signal processing system including improved calibration apparatus for use with a radiation imaging apparatus, comprising: (a) a radiation transducer for producing signals representative of the apparent orthogonal spatial coordinates and of the energy level of detected radiation events; (b) means operative in a spatial calibration mode for storing corrected spatial coordinates corresponding to a plurality of predetermined apparent spatial coordinates relative to selected detected radiation events; (c) means for translating apparent spatial coordinates to corrected spatial coordinates, said translating means communicating with said means for storing; (d) means for interpolating the corrected spatial coordinates of the detected radiation events occurring within the space bounded by said stored corrected spatial coordinates to produce precise corrected spatial coordinates; (e) means operative in an energy level calibration mode using coordinates derived from said translating means for obtaining a histogram for each corrected spatial element; (f) means operative in said energy level calibration mode for setting a window of acceptable energy levels; (g) means operative in said energy level calibration node for determining the number of counts in response to a flood image occurring within said window for each corrected spatial element; ; (h) means operative in said energy level calibration mode for progressively adapting the window for each element until all of said elements accept substantially the same number of counts in response to the flood image; (i) means operative in said energy level calibration node for storing one or more of said windows as a function of apparent spatial coordinates; (j) means for comparing the energy level of the transducer signals of the detected radiation events to the windows corresponding to the apparent spatial coordinates of the events; and (k) output means for producing an output signal, said output means being responsive to said transducer signals and to said comparing means so that only those transducer signals occurring within the windows contribute to form said output signal.

Claim 18

A signal processing system for use with a radiation imaging apparatus having detector means for producing an output signal representing apparent orthogonal spatial coordinates and the associated energy level of a radiation event, comprising: means for determining the energy level distribution and peak energy content of radiation events occurring within predetermined elements in response to an image of known energy level, each of said elements being defined as a predetermined portion of the apparent image field; and means for determining an energy window to be accepted for each element in response to a flood image such that every element accepts substantially the same number of events in response to a flood image.

Claim 19

A signal processing system for use with a radiation imaging apparatus having detector means for producing an output signal representing apparent orthogonal spatial coordinates and the associated energy level of a radiation event, comprising: means for determining the energy level distribution and peak energy content of radiation events occurring within predetermined elements in response to an image of known energy level, each of said elements being defined as a predetermined portion of the apparent image field; and means for determining an energy window to be accepted for each element in response to a flood image such that every element accepts substantially the same number of events in response to a flood image.