title: Optimization of PET/CT image quality using the GE 'Sharp IR' point-spread function reconstruction algorithm.
abstract: OBJECTIVE
  The objective of this study was to quantify any improvement with the GE 'Sharp IR' point-spread function (PSF) reconstruction algorithm in addition to ordered subsets expectation maximum (OSEM) and time-of-flight (TOF) reconstruction algorithms and establish the optimum parameters to be used in clinical studies.
  
  
  METHODS
  We conducted a range of experiments using the National Electrical Manufacturers Association image quality phantom filled with a 4 : 1 signal-to-background ratio. We scanned the phantom using the GE Discovery 690 PET/CT scanner. We varied iteration number and Gaussian filtration. Results were compared for OSEM, OSEM+TOF and OSEM+TOF+PSF reconstructions. A sample of 15 whole-body fluorine-18-fluorodeoxyglucose were reconstructed with OSEM+TOF and OSEM+TOF+PSF using a selection of optimum reconstruction parameters determined in phantom studies. Clinicians qualitatively ranked their preferred images to choose optimum parameters.
  
  
  RESULTS
  The addition of PSF improved signal-to-noise ratios (SNRs), contrast, hot contrast recovery coefficients and noise over OSEM and OSEM+TOF reconstruction algorithms. SNRs were the highest at two iterations and with 0 or 2 mm filters with OSEM+TOF+PSF reconstruction in all phantom studies. Clinicians generally favoured OSEM+TOF+PSF reconstruction with three iterations and a 2 mm filter.
  
  
  CONCLUSIONS
  PSF reconstruction significantly improved image quality for both clinical and phantom studies. We recommended the optimum reconstruction parameters using three iterations, 24 subsets and a 2 mm filter, which improved SNRs by up to 28.8% for small lesions (P<0.05).
authors.affiliation: aDepartment of Nuclear Medicine, Cambridge University Hospitals Foundation Trust, Cambridge bDepartment of Medical Physics, Queen Elizabeth Hospital, Gateshead, UK.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Vennart
authors.forename: Nicholas
authors.initials: N
authors.lastname: Bird
authors.forename: John
authors.initials: J
authors.lastname: Buscombe
authors.forename: Heok K
authors.initials: HK
authors.lastname: Cheow
authors.forename: Ewa
authors.initials: E
authors.lastname: Nowosinska
authors.forename: Sarah
authors.initials: S
authors.lastname: Heard
mesh_terms: D000465:Algorithms; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D000072078:Positron Emission Tomography Computed Tomography; D011786:Quality Control