Speaker
Dr
David P McElroy
(Sunnybrook and Women's College Health Science Centre, University of Toronto)
Description
The Silicon Photomultiplier (SiPM) is a novel, compact detector which shows great
promise for use in MR compatible PET systems and other high resolution PET scanners
for dedicated imaging applications. Like avalanche photodiodes (APDs), SiPMs are
insensitive to magnetic fields, however they have the additional advantage of an
extremely high intrinsic gain (about 1M), eliminating the need for preamplifiers and
the accompanying shielding necessary for use in the bore of an MR scanner. They are
also much faster than APDs, resulting in better coincidence timing resolution, and
operate at a relatively low voltage (40 – 45 V). In addition, their compact size
allows SiPMs to be used to extract depth of interaction information from
scintillation crystals. A prototype detector is currently under investigation at the
University of Toronto. The 1 mm x 1 mm active area of the SiPM consists of an array
of 1440 individual avalanche photodiodes (microcells) operated in Geiger mode. Each
microcell measures 20 microns x 30 microns, and all are manufactured on the same
silicon substrate (pitch 25 microns x 35 microns) and connected in parallel through
integrated quenching resistors. The output signal of the SiPM is thus the sum of the
standardised signals from the individual microcells, and is proportional to the
number of detected light photons, provided the number of light photons does not
exceed the number of individual microcells. The detector prototype was operated
without a preamplifier, and the output signal was sent directly to a shaping
amplifier. Preliminary measurements made using 2 mm diameter LYSO crystals of
varying length and an FDG source show encouraging results, from which a physical
model of the next generation of multi-element SiPM detectors will be developed that
should be well suited for use in a high performance MR compatible PET scanner.
Author
Dr
David P McElroy
(Sunnybrook and Women's College Health Science Centre, University of Toronto)
Co-authors
Dr
Alla Reznik
(Sunnybrook and Women's College Health Science Centre)
Prof.
John A Rowlands
(Sunnybrook and Women's College Health Science Centre, University of Toronto)
Prof.
Valeri Saveliev
(Obninsk State University of Atomic Energy)