Radiant energy – Invisible radiant energy responsive electric signalling – With or including a luminophor
Patent
1981-06-15
1984-10-02
Howell, Janice A.
Radiant energy
Invisible radiant energy responsive electric signalling
With or including a luminophor
250369, G01T 120
Patent
active
044750420
ABSTRACT:
An improved threshold preamplifier circuit is disclosed for use with the event X, Y position detection circuitry of a scintillation camera. Threshold amplifiers, having a common threshold voltage that is set as a function of the energy of the incident scintillation event, control the respective preamplified photomultiplier tube output signals so that signals from tubes close to the event receive greater weight in the X, Y position analysis than signals from distant tubes. In a preferred embodiment, the threshold voltage is determined by the output of a summing amplifier which sums an unthresholded energy signal Z.sub.nt which represents the total energy of the incident event, an integrated energy signal Z.sub.u which represents the integrated value of the unthresholded energy signal Z.sub.nt, and a constant voltage which represents the preselected zero energy level threshold biasing voltage. Variable resistors control the relative contributions to the summing amplifier input of the Z.sub.nt and Z.sub.u energy signals. The invention overcomes the shortcoming of prior art constant threshold voltage circuits that the size of displayed images (determined by the computation of X, Y ratios using thresholded energy signals Z.sub.t) varies for detection of events caused by multiple energy isotopes and dual isotopes with different energies.
REFERENCES:
patent: 3011057 (1961-11-01), Anger
patent: 3732419 (1973-05-01), Kulberg et al.
patent: 3984689 (1976-10-01), Arseneau
patent: 4071762 (1978-01-01), Lange et al.
patent: 4142102 (1979-02-01), Lange
Howell Janice A.
Milde Jr. Karl F.
Siemens Gammasonics Inc.
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