title: Clinical evaluation of PET image reconstruction using a spatial resolution model.
abstract: OBJECTIVE
  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.
  
  
  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 hpi of 400 MBq [18F]-FDG. Attenuation-corrected PET images were reconstructed on 336 × 336-matrices using: (R1) standard AW-OSEM (4 iter, 8 subsets, 4 mm Gaussian) and (R2) AW-OSEM with PSF (3 iter, 21 subsets, 2 mm). 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 (SUVmax, SUVmean, volume) of lesions seen on R1 and R2 is reported as (R2-R1)/R1. Furthermore, SUVmax and SUVmean was measured for a 3 cm 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 SUVmax (R2) was higher than SUVmax (R1). 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 R1 and R2.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Flemming Littrup
authors.initials: FL
authors.lastname: Andersen
authors.forename: Thomas Levin
authors.initials: TL
authors.lastname: Klausen
authors.forename: Annika
authors.initials: A
authors.lastname: Loft
authors.forename: Thomas
authors.initials: T
authors.lastname: Beyer
authors.forename: Søren
authors.initials: S
authors.lastname: Holm
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D003198:Computer Simulation; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009369:Neoplasms / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D051598:Whole Body Imaging / Q000379:methods*; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18