Clinical evaluation of PET image reconstruction using a spatial resolution model

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 2.5min/bed at 1hpi of 400 MBq [18F]-FDG. Attenuation-corrected PET images were reconstructed on 336×336-matrices using: (R1) standard AW-OSEM (4 iter, 8 subsets, 4mm Gaussian) and (R2) AW-OSEM with PSF (3 iter, 21 subsets, 2mm). Blinded and randomised reading of R1- and R2-PET images was performed. Individual lesions were located and counted independently on both sets of images. The relative change in PET quantification (SUV(max), SUV(mean), volume) of lesions seen on R1 and R2 is reported as (R2-R1)/R1. Furthermore, SUV(max) and SUV(mean) was measured for a 3cm spherical norm region in the right lobe of the healthy liver for R1 and R2. RESULTS: Clinical reading revealed 91 and 103 positive lesions for R1 and R2, respectively. For all lesions SUV(max) (R2) was higher than SUV(max) (R1). Regression analysis indicated that the relative increase in SUV(max) (and SUV(mean)) 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 SUV(mean) in homogenous liver tissue between R1 and R2. CONCLUSION: In whole-body FDG-PET/CT using routine clinical protocols, PSF-based PET reconstruction increases lesion detection and affects SUV(max) measurements compared to standard AW-OSEM PET reconstruction.