The effect of edge artifacts on quantification of Positron Emission Tomography

We examined the quantitative effect of the edge artifacts caused by using a point spread function (PSF) system model for Positron Emission Tomography (PET) image reconstruction. Two phantoms were used in this study. The first phantom was a new small PET phantom that was used to measure the quantitative effects. The cylindrical phantom had 5 hot cylinder inserts with different diameters and was scanned with different hot insert-to-background ratios. Results showed that the region of interest (ROI) mean value (equal diameters for ROIs and cylinders) of PSF-OSEM was higher than that of OSEM without PSF model due to better resolution recovery, and the total activity was preserved in all images. However the ROI maximum value of PSF-OSEM could be significantly higher than the true value, and this overshoot depends on both the cylinder size and the concentration ratio. The largest effect was observed with the 8mm diameter cylinder insert at the highest concentration ratio. The second phantom was a Hoffman brain phantom, which was used to display the effect visually without quantitative measurements.