Dynamic threshold for scintillation camera
US4475042A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 15, 1981 |
| Grant date | Oct 2, 1984 |
| Priority date | — |
| Expiry date | Jun 15, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01T1/1642
- WIPO fieldEnvironmental technology
- WIPO sectorChemistry
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 rati…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.