title: Improvement in PET/CT image quality in overweight patients with PSF and TOF.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effect of the point spread function (PSF) and time of flight (TOF) on PET/CT images of overweight patients in relation to the iteration number and the acquisition time.
  
  
  METHODS
  This study consisted of a phantom study and a clinical study. The NEMA IEC body phantom and a 40 cm diameter large phantom (LG phantom) simulating an overweight patient were used in this study. Both phantoms were filled with (18)F solution with a sphere to background ratio of 4:1. The PET data were reconstructed with the baseline ordered-subsets expectation maximization (OSEM) algorithm, with the OSEM + PSF model, with the OSEM + TOF model and with the OSEM + PSF + TOF model. The clinical study was a retrospective analysis of 66 patients who underwent (18)F-FDG PET/CT. The image quality was evaluated using the background variability (coefficient of variance, CVphantom and CVliver) and the contrast (CONTHOT and SNR).
  
  
  RESULTS
  In phantom study, the CVphantom of the LG phantom was higher than that of the NEMA phantom. The PSF decreased the CVphantom of the LG phantom to the NEMA phantom level. The TOF information accelerated the CVphantom plateau earlier. The best relationship between the CVphantom and the CONTHOT was observed for the OSEM + PSF + TOF. In clinical study, the combination of PSF and TOF decreased the CVliver for overweight patients to that for normal weight patients while it increased the SNR similarly between two patient groups.
  
  
  CONCLUSIONS
  The combination of the PSF and TOF correction improved the image quality of the LG phantom and overweight patients.
authors.affiliation: Division of Medical Quantum Science, Department of Health Sciences, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Taniguchi
authors.forename: Go
authors.initials: G
authors.lastname: Akamatsu
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Kasahara
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Mitsumoto
authors.forename: Shingo
authors.initials: S
authors.lastname: Baba
authors.forename: Yuji
authors.initials: Y
authors.lastname: Tsutsui
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Himuro
authors.forename: Shohei
authors.initials: S
authors.lastname: Mikasa
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kidera
authors.forename: Masayuki
authors.initials: M
authors.lastname: Sasaki
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D064847:Multimodal Imaging / Q000295:instrumentation / Q000379:methods; D050177:Overweight / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation / Q000379:methods*; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18