Energy dependent gain correction

Claim 3

A medical imaging system comprising: (a) a radiation source (10); (b) a radiation responsive detector array (14) spaced sufficiently from the source (10) to accommodate the interposition of an object (P) in a space between the source (10) and the detector array (14); (c) scanning means (24) for effecting relative scanning motion between the detector array (14) and an object (P) when said object (P) is located in said object space; and (d) power means for actuating the source to direct radiation through the object space and toward the detector array; characterised in that the system further includes: (e) circuitry coupled to the detector array for determining the beam quality of radiation incident on the detector array; (f) correction means coupled to said detector and said circuitry for correcting the detector array response to incident radiation, said correction being a function of the beam quality of said incident radiation; and (g) imaging circuitry coupled to the correction means for producing an image representative of corrected detector array response to incident radiation.

Claim 4

A medical imaging system comprising: (a) a radiation source (10); (b) a radiation responsive detector array (14) spaced sufficiently from the source (10) to accommodate the interposition of an object (P) in a space between the source (10) and the detector array (14); (c) scanning means (24) for effecting relative scanning motion between the detector array (14) and an object (P) when said object (P) is located in said object space; and (d) power means for actuating the source to direct radiation through the object space and toward the detector array; characterised in that the system further includes: (e) circuitry coupled to the detector array for determining the beam quality of radiation incident on the detector array; (f) correction means coupled to said detector and said circuitry for correcting the detector array response to incident radiation, said correction being a function of the beam quality of said incident radiation; and (g) imaging circuitry coupled to the correction means for producing an image representative of corrected detector array response to incident radiation.

Claim 5

A system according to Claim 2 wherein said correction means comprises: (a) means for storing a set of calibration signals representative of the detectors response to variations in beam quality; (b) a function generator coupled to said detector and said storage means for combining a set of image signals representative of radiation transmitted through the object under examination with said calibration signal set to produce a gain correction function; and (c) modifying circuitry coupled to said function generator and said detector for modifying the image signal set by the gain correction function to producea gain corrected detector response.

Claim 6

An imaging system compising: a radiation source (10), a detector (14), and imaging circuitry coupled to the detector for producing a representation of a pattern of radiation incident on the detector characterised by: (a) means coupled to the detector (14) for determining beam quality of the radiation incident on the detector(14); and (b) correction means coupled to the detector (14) and the beam quality determining means for correcting the detector response to the incident radiation, said correction being a function of beam quality of the incident radiation.

Claim 7

An imaging system compising: a radiation source (10), a detector (14), and imaging circuitry coupled to the detector for producing a representation of a pattern of radiation incident on the detector characterised by: (a) means coupled to the detector (14) for determining beam quality of the radiation incident on the detector(14); and (b) correction means coupled to the detector (14) and the beam quality determining means for correcting the detector response to the incident radiation, said correction being a function of beam quality of the incident radiation.

Claim 10

A method according to Claim 5 wherein said gain correction function is dependent on the energy distribution of the incident radiation.

Claim 13

A method according to Claim 7 wherein said gain correction function is represented by a Taylor series expansion.

Claim 14

A method according to Claim 8 wherein said Taylor series expansion is represented by the formula: where A o , A l and A 2 are constants of a given detector; PIX L0, PIX HI represent low and high energy pixel values at a given pixel location; RGf PIX L0, Ref PIX HI represent low and high energy pixel values at a given pixel location at reference beam hardness at calibration.

Claim 15

An imaging system comprising a radiation source(10). a detector (14), and imaging circuitry coupled to the detector for producing a representation of a pattern of radiation incident on the detector characterised by: (a) means for measuring an initial detector response to incident radiation; (b) means for deriving a detector gain normalization factor, said factor being a function of the beam quality of the incident radiation; and (c) means for deriving a gain corrected detector response by applying said normalization factor to said initial detector response.

Claim 16

An imaging system comprising a radiation source(10). a detector (14), and imaging circuitry coupled to the detector for producing a representation of a pattern of radiation incident on the detector characterised by: (a) means for measuring an initial detector response to incident radiation; (b) means for deriving a detector gain normalization factor, said factor being a function of the beam quality of the incident radiation; and (c) means for deriving a gain corrected detector response by applying said normalization factor to said initial detector response.

Claim 17

A digital radiography system characterised in that it comprises:- (a) a radiation source (10) for directing radiation along a path; (b) a radiation detector (14) spaced from the source to receive radiation from said source (10) and to produce signals indicating beam quality of the incident radiation; (c) means (96, 98) for storing a first set of signals representative of said detectors response to variations in beam quality; (d) means (94) for producing a gain correction function, said means comprising: (i) first receiving means coupled to said storage means (96, 98) for receiving said first set of signals; (ii) second receiving means coupled to the detector (14) for receiving a second set of signals representative of radiation transmitted through an object under examination; (iii) a function generator for combining said first signal set with said second signal set as a function of the respective beam qualities; (e) means (102) for combining said second set of signals with said gain correction function to produce gain corrected signals; and (f) imaging circuitry for receiving said gain corrected signals for producing a representation of a pattern of radiation incident on the detectors.

Claim 18

A digital radiography system characterised in that it comprises:- (a) a radiation source (10) for directing radiation along a path; (b) a radiation detector (14) spaced from the source to receive radiation from said source (10) and to produce signals indicating beam quality of the incident radiation; (c) means (96, 98) for storing a first set of signals representative of said detectors response to variations in beam quality; (d) means (94) for producing a gain correction function, said means comprising: (i) first receiving means coupled to said storage means (96, 98) for receiving said first set of signals; (ii) second receiving means coupled to the detector (14) for receiving a second set of signals representative of radiation transmitted through an object under examination; (iii) a function generator for combining said first signal set with said second signal set as a function of the respective beam qualities; (e) means (102) for combining said second set of signals with said gain correction function to produce gain corrected signals; and (f) imaging circuitry for receiving said gain corrected signals for producing a representation of a pattern of radiation incident on the detectors.

Claim 19

A system according to Claim 11 wherein said detector (14) comprises a plurality of individual detector elements.

Claim 20

An imaging system comprising: (a) a radiation source (10); (b) an array of detector elements (14) facing the source (10) each element being responsive to incident radiation to produce an electrical signal indicative of said radiation characterised by: (c) circuitry (94) coupled to said detector elements and responsive to said electrical signals for determining the spectral distribution of the incident radiation; (d) a function generator (94) coupled to said circuitry for producing a detector gain correction signal, said signal being a function of the spectral distribution of the incident radiation; (e) correction circuitry (102) coupled to said detector elements (14) and to said function generator (94) for generating a gain corrected electrical signal by combining the electrical signals and the gain correction signal; and (f) imaging circuitry coupled to said correction circuitry and responsive to said gain corrected electrical signals for producing a representation of a pattern of said incident radiation.

Claim 21

An imaging system comprising: (a) a radiation source (10); (b) an array of detector elements (14) facing the source (10) each element being responsive to incident radiation to produce an electrical signal indicative of said radiation characterised by: (c) circuitry (94) coupled to said detector elements and responsive to said electrical signals for determining the spectral distribution of the incident radiation; (d) a function generator (94) coupled to said circuitry for producing a detector gain correction signal, said signal being a function of the spectral distribution of the incident radiation; (e) correction circuitry (102) coupled to said detector elements (14) and to said function generator (94) for generating a gain corrected electrical signal by combining the electrical signals and the gain correction signal; and (f) imaging circuitry coupled to said correction circuitry and responsive to said gain corrected electrical signals for producing a representation of a pattern of said incident radiation.

Claim 22

An imaging system according to Claim 12 wherein the gain corrected electrical signal is generated substantially simultaneously to the production of said incident radiation pattern representation.