Recent Study on the Feasibility of High Spatial Resolution Working Modes for Renovated Clinical PET Scanner

This is a feasibility study on improving the spatial resolution of clinical PET, by slightly renovating the
PET scanner design such that high spatial resolution working modes (HSRWM) are achievable.
Introduction: The poor spatial resolution of prevalent PET imaging has restrained its sensitivity in
imaging small lesions, e.g. early-stage cancers or small metastasis. This drawback is caused by 2
essential requirements in clinic: A relatively large diameter (e.g. 80cm) for PET scanner to accumulate
patients, and sizeable scintillator detectors to maintain a reasonable collecting efficiency. In recent
decade more efforts focused on improvement of detector resolution, e.g. digital PET, since the
request on ring diameter is fundamental.
Methods: The novel concept of equivalent position of imaging was proposed for the first time. A
typical static PET scan can be virtually considered as superposition of m equivalent sub-scans at m
different equivalent imaging positions, when the scanner ring is systematically adjusted its angular
orientation within one detector size. In this case each detector is virtually divided into m equal subdetectors,
without physical minimizing the detector size. The contributions of those sub-scans are
analytical by an m x m matrix. The time for performing a high-resolution scan could be comparable to
a typical PET scan, as long as the Poisson noises are insignificant to low-uptake voxels.
Discussion: Three dimensional modeling for imaging at different m were also conducted. As a result,
for a typical scanner design e.g. 80cm in diameter with 18F as tracers, the spatial resolution of double
sub-scans (m =2) is 2.56mm, and 2.19mm for triple sub-scans (m=3). Scanning at high m (m>2) will
slightly drop contrast resolution, hence m=2 is preferably recommended.
Conclusion: As a compatible approach to digital PET and other technological renovation, the novel
HSRWM design is feasible, enabling PET to image small lesions in clinic.