The effect of the rotational orientation of circular photomultipliers in a PET camera block detector design

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:513173

Uribe, J; Wong, Wai-Hoi; Hu, Guoju ^[1]

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1. Univ. of Texas MD Anderson Cancer Center, Houston, TX (United States); and others

This is a study of the effects of geometric asymmetries in circular photomultipliers (PMT) on the design of PET position-sensitive block detectors. The dynodes of linear-focus circular PMT`s are asymmetric relative to the axis of the photocathode, despite the rotational symmetry of the photocathode. Hence, there are regional photocathode differences in the anode signal, which affect the decoding characteristics of position sensitive block detectors. This orientation effect, as well as the effect of introducing light diffusers, are studied in a block detector design (BGO) using the PMT-quadrant-sharing configuration. The PMT studied is the Philips XP-1911 (19mm diameter). Seven symmetrical and representative orientations of the four decoding PMT were investigated, as well as one asymmetric orientation. The measurements performed include block-composite pulse-height spectra and crystal decoding maps. Two orientation effects were observed: (A) distortion variation in decoding maps, and (B) decoding resolution variation. The introduction of circular plastic pieces, used as light diffusers, prove to be useful by improving the decoding of crystals on the periphery of the detector block and minimizing distortion in the decoding map. These measurements have shown optimal PMT orientations for the PMT-quadrant-sharing design, as well as for conventional block designs.

• OSTI ID: 513173
• Report Number(s): CONF-961123--
• Country of Publication: United States
• Language: English

Related Subjects

44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
GEOMETRY
ORIENTATION
PHOTOCATHODES
PHOTOMULTIPLIERS
POSITION SENSITIVE DETECTORS
POSITRON COMPUTED TOMOGRAPHY