Technique for balancing anger cameras using an externally irradiated crystal and single tube data
US5550377A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 20, 1994 |
| Grant date | Aug 27, 1996 |
| Priority date | — |
| Expiry date | Sep 20, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01T1/1648
- WIPO fieldEnvironmental technology
- WIPO sectorChemistry
Abstract
To calibrate a nuclear camera, the scintillation crystal (10) is irradiated with a uniform flood source (34). Scintillation events cause corresponding electrical pulses from photomultiplier tubes (12) that are optically coupled to the scintillation crystal. A selection circuit (40) compares (42) the amplitude or energy of pulses at each coordinate with a median energy and divides the pulses to generate a higher energy image (44) and a lower energy image (46). When the higher and lower energy images are subtracted (50) regions of the difference image (52) with high count densities identify a photomultiplier tube for gain adjustment. A gain adjustment circuit (60) monitors the amplitude of the electrical pulses and the number of pulses with each amplitude from the selected photomultiplier tube to generate a raw data energy distribution curve (FIG. 3). The energy distribution curve is smoothed (70) and the first derivative is taken (72). The curve is filtered (74) to isolate a preselected energy region. The curve is analyzed (92) to determine an energy value corresponding to a centroid (94) of the filtered first derivative curve. The centroid energy value is compared (96) with the cen…
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