MLEM Reconstructed Image Resolution from the LabPET Animal Scanner

Background: PET image resolution is a function of scanner intrinsic resolution and reconstruction method. The purpose of this study was to measure reconstructed image resolution vs. MLEM iterations on the new LabPET 3.6 animal scanner. Methods: A Micro Deluxetrade hot rods phantom filled with an ¹⁸F solution was scanned for 60 min, and images were reconstructed using 10 to 1000 MLEM iterations. To estimate the image resolution, peak activity values were measured for each rod and compared to the theoretical values of partial-volume recovery obtained by convolving a 2D-Gaussian model with circles of the known rod diameters. Results were confirmed visually by convolving the estimated Gaussian model with a high resolution CT image. Results: FWHM image resolution improved from 2.1 to 1.3 mm with 10 to 1000 MLEM iterations. CT image convolution with this Gaussian model faithfully reproduced the measured resolution in images reconstructed with 200 MLEM iterations. Conclusion: Initial measurement of the LabPET transverse image resolution is consistent with that expected from a system with individual detector readout.