Clinical evaluation of PET image reconstruction using a spatial resolution model

Abstract Purpose PET image resolution is variable across the measured field-of-view and described by the point spread function (PSF). When accounting for the PSF during PET image reconstruction image resolution is improved and partial volume effects are reduced. Here, we evaluate the effect of PSF-based reconstruction on lesion quantification in routine clinical whole-body (WB) PET/CT imaging. Materials and methods 41 oncology patients were referred for a WB-PET/CT examination (Biograph 40 TruePoint). Emission data were acquired at 2.5 min/bed at 1 h pi of 400 MBq [18F]-FDG. Attenuation-corrected PET images were reconstructed on 336 × 336-matrices using: ( R 1) standard AW-OSEM (4 iter, 8 subsets, 4 mm Gaussian) and ( R 2) AW-OSEM with PSF (3 iter, 21 subsets, 2 mm). Blinded and randomised reading of R 1- and R 2-PET images was performed. Individual lesions were located and counted independently on both sets of images. The relative change in PET quantification (SUVmax , SUVmean , volume) of lesions seen on R 1 and R 2 is reported as ( R 2 − R 1)/ R 1. Furthermore, SUVmax and SUVmean was measured for a 3 cm spherical norm region in the right lobe of the healthy liver for R 1 and R 2. Results Clinical reading revealed 91 and 103 positive lesions for R 1 and R 2, respectively. For all lesions SUVmax ( R 2) was higher than SUVmax ( R 1). Regression analysis indicated that the relative increase in SUVmax (and SUVmean ) decreased with lesion size, whilst it increased with increasing radial distance from the centre of the field of view (FOV). There was no significant difference in SUVmean in homogenous liver tissue between R 1 and R 2. Conclusion In whole-body FDG-PET/CT using routine clinical protocols, PSF-based PET reconstruction increases lesion detection and affects SUVmax measurements compared to standard AW-OSEM PET reconstruction.