title: Impact of point spread function reconstruction on quantitative 18F-FDG-PET/CT imaging parameters and inter-reader reproducibility in solid tumors.
abstract: BACKGROUND
  This study aims to determine the impact of point-spread function (PSF) reconstruction on quantitative PET/computed tomography (CT) indices and the inter-reader reproducibility of these measurements.
  
  
  METHODS
  The study was approved by the Institutional Review Board under a waiver of informed consent. A total of 42 oncology patients with 85 lesions (all ≥ 2 cm) were included. The PET/CT images were reconstructed with PSF (OSEM+TOF, 2i, 21s, all-pass filter) and without PSF (OSEM+TOF, 2i, 21s, 5 mm Gaussian). For each lesion, the maximum, mean, and peak standardized uptake values (SUV), total lesion glycolysis (TLG), and metabolic tumor volume (MTV) were measured by two readers (R1 and R2) using a semiautomatic gradient segmentation method. Intraclass correlation coefficient (ICC) and Bland-Altman analyses were performed.
  
  
  RESULTS
  There was excellent correlation between non-PSF and PSF reconstruction PET/CT values (ICC ≥ 0.96 for all parameters, P < 0.0001). Comparison of PSF with non-PSF images showed a mean bias (percentage change) of +11.97% (R1) and +11.94% (R2) for SUV max, +7.63% (R1) and +7.82% (R2) for SUV mean, +7.45% (R1) and +7.37% (R2) for SUV peak, -0.82% (R1) and -0.1% (R2) for TLG, and -6.68% (R1) and -5.65% (R2) for MTV. PSF reconstruction resulted in a decrease in MTV in 77.6% (R1) and 83.5% (R2) of lesions. Percentage changes in PSF versus non-PSF indices were not related to the site of the lesions (P > 0.05). Close agreement was observed between two readers (ICC ranged between 0.9 and 1.0, P < 0.0001).
  
  
  CONCLUSIONS
  The PSF reconstruction increased the SUV max, SUV mean, and SUV peak, as expected, whereas it tended to produce lower values for MTV and had variable effect on TLG. This can be attributed to the ability of PSF reconstruction to better discern tumor uptake from activity spill-out.
authors.affiliation: aRussell H. Morgan Department of Radiology and Radiological Sciences bDepartment of Oncology of Johns Hopkins School of Medicine cDepartment of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
authors.forename: Sara
authors.initials: S
authors.lastname: Sheikhbahaei
authors.forename: Charles
authors.initials: C
authors.lastname: Marcus
authors.forename: Rick
authors.initials: R
authors.lastname: Wray
authors.forename: Arman
authors.initials: A
authors.lastname: Rahmim
authors.forename: Martin A
authors.initials: MA
authors.lastname: Lodge
authors.forename: Rathan M
authors.initials: RM
authors.lastname: Subramaniam
mesh_terms: D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009369:Neoplasms / Q000000981:diagnostic imaging*; D015588:Observer Variation; D049268:Positron-Emission Tomography; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
chemical_list: D019788:Fluorodeoxyglucose F18