Use of digital front end electronics for optimization of a modular PET detector

• Main Authors: Cutler, P.D., Hoffman, E.J.
• Format: Conference Proceeding
• Language: English
• Subjects: Bismuth; Crystals; Detectors; Hardware; Image edge detection; Image reconstruction; Microprogramming; Photomultipliers; Spatial resolution; Statistics
• DOI: 10.1109/NSSMIC.1991.259183

The sensitivity and resolution of a novel modular bismuth germanate (BGO) detector and its associated front-end electronics were characterized. The detector is a 6*8 matrix of BGO elements 3.5*6.25 mm, coupled to two dual-channel Hamamatsu photomultiplier tubes. Sensitivity varied by 50-70% and resolution by 20-25% from center to edge of the detector, depending on lower threshold. Specialized hardware and firmware in this detector system enable sensitivity and resolution to be balanced to achieve a more uniform response. The ability of this system to achieve uniform detector sensitivity by adjusting individual crystal thresholds was measured. While achieving balanced detector sensitivity, this technique increased overall sensitivity by 42%. Average intrinsic spatial resolution for a block changed from 3.25 mm to 3.5 mm when thresholds were adjusted. Correction of modulating detector sensitivity in projection data by postacquisition scaling amplifies noise in reconstructed emission and transmission images. Possible improvement in image noise by balancing the sensitivity of all crystals in a block was simulated. Improvement in image noise in simulated emission images was 23%, of which 16% was due to improved statistics and 7% to removal of detector sensitivity modulation.< >