Edge artifacts in PSF based PET reconstruction in relation to the reconstruction parameters

Objectives We investigated the properties of edge artifacts in PSF based PET reconstruction to examine the relationship between edge artifacts and the reconstruction parameters.

Methods We used a cone shaped phantom (20 mm largest diameter × 115 mm length) filled with an ¹⁸F solution (5.23 kBq/mL). PET data were then acquired in a three-dimensional list mode for 10 minutes using a Biograph mCT. PET images were reconstructed using baseline ordered-subsets expectation maximization (OSEM) and OSEM with the point-spread function (PSF) algorithm. The pixel sizes used were 0.5, 1.0, 2.0, 3.0 and 4.0 mm. The post-filter of full width at half maximum (FWHM) was 0, 1.0, 2.0, and 3.0 mm. The PET images were analyzed using the maximum count (Cmax).

Results Regarding the OSEM reconstruction image, no overshoot was observed. Regarding the OSEM+PSF reconstruction image, the highest overshoot, namely a 45% overestimation, was observed at a 6.0 mm diameter using the pixel size 1.0 mm and 0 mm of FWHM (no filter). As the pixel size and post-filter FWHM increases, overshoot appeared with a larger diameter.

Conclusions PSF based reconstruction results in different degrees of edge artifacts in relation to the pixel size and post-filter FWHM.