Speaker
Description
In positron emission tomography, dense Cherenkov radiators provide an
opportunity for high gamma detection efficiency and excellent CTR.
However, because only a few tens of Cherenkov photons follow a gamma
interaction in the radiator, the detection efficiency and the energy
resolution of a pure Cherenkov detector are an issue. We study gamma
detection efficiency and CTR of PbF$_2$ based detectors with different
surface treatments and photo-detectors (SiPMs with realistic PDE and 70
ps FWHM SPTR) covering one, two, or all crystal faces. We investigate
the potential performance of a full-size Cherenkov PET using the NEMA NU
2-2018 standard and compare image quality with a reference scanner -
Siemens Biograph Vision PET scanner - with the geometry of Cherenkov
scanners based on that of the reference scanner. Monte Carlo simulations
were performed on a super-computing network using GATE, and CASToR was
used for TOF-OSEM image reconstruction. Normalization, scatter, random,
and attenuation correction factors were included in the reconstruction.
Cherenkov scanner with 1-sided readout had similar TOF performance (~210
ps CTR-FWHM) and achieved very similar image quality as the reference
scanner. By using 2-sided (SiPMs at the sides of the crystal) or 6-sided
detector designs with better coincidence detection efficiency and ~120
ps CTR-FWHM, even better image quality was achieved. The main limitation
of our simulation study is not including the noise in the simulation -
especially the dark count events of the SiPMs. We demonstrate that even
though pure Cherenkov scanners have basically no energy resolution, the
scatter fraction is around 50%, compared to 33% with the reference
scanner, and is not prohibitively large. Images comparable to the
state-of-the-art clinical PET scanner can be achieved due to improved
efficiency and CTR attainable with PbF$_2$. Low-cost Cherenkov detectors
could become especially interesting for total-body scanners.
