Radiant energy – Invisible radiant energy responsive electric signalling – With or including a luminophor
Patent
1978-06-19
1980-09-16
Smith, Alfred E.
Radiant energy
Invisible radiant energy responsive electric signalling
With or including a luminophor
250369, G01T 120, G01T 1208
Patent
active
042232210
ABSTRACT:
A two-stage system for enhancing the imaging uniformity of a scintillation camera is disclosed. The camera includes means for detecting radiation events and for producing radiation count signals indicating the location and energy level of individual detected radiation events. The uniformity correction system compensates for imprecision in the camera's indication of both radiation event regional image count density and event energy level. Compensation for energy indication errors is done by a first stage, prior to a second stage correction for residual nonuniformity in regional image count density. The operations of both stages are carried out in real time for each individual radiation count, independently of the production of other counts.
The first stage location and stores a representation of the respective peaks of the detected energy pulse height distribution for each of a plurality of regions in the camera's field of view. This regional profile of the camera's energy response characteristic is used to successively realign for each count the pulse height energy window defined by the camera imaging circuitry, to align the window over the respective energy peak for each count as a function of the count's location indication.
The second uniformity correction stage, a flood correction circuit, produces and stores a profile of regional variation in the image count density indicated by the camera in response to a uniform radiation flood over its field. This stored information is used for calculating regional count density correction factors for different regions of the camera field. The correction factors are used for controlling the ratio of radiation counts corresponding to each region which are actually imaged, thus eliminating residual nonuniformity caused by nonuniform regional image count density produced by the camera.
No scintillation camera is capable of producing radiation count signals which define either the location or the energy level of radiation events with absolute precision. Minute inaccuracies in the location, and energy level decoding cause nonuniformity in the image count density of the scintillation camera systems.
The uniformity of image count density of a scintillation camera detector can be degraded by factors including inaccuracies in energy level decoding, inaccuracies in location (x-y) decoding, nonlinearity), regional variations in detector sensitivity, and other factors.
REFERENCES:
patent: 3878373 (1975-04-01), Blum
patent: 4095108 (1978-06-01), Inbar et al.
patent: 4115694 (1978-09-01), Lange et al.
patent: 4151416 (1979-04-01), Richey et al.
"Correction Automatique de la defendance en position de l'energie" (compte rendu 11.sup.e Collogue International, sur la fixation renale du Hg radioactif, Paris, 24-25, Oct. 1975).
Benenson Gary
Gambini Michael R.
Howell Janice A.
Picker Corporation
Smith Alfred E.
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