title: Influences of point-spread function and time-of-flight reconstructions on standardized uptake value of lymph node metastases in FDG-PET.
abstract: OBJECTIVE
  The purpose of this study was to investigate the effects of point-spread function (PSF) and time-of-flight (TOF) on the standardized uptake value (SUV) of lymph node metastasis in FDG-PET/CT.
  
  
  METHODS
  This study evaluated 41 lymph node metastases in 15 patients who had undergone (18)F-FDG PET/CT. The lesion diameters were 2.5 cm or less. The mean short-axis diameter of the lymph nodes was 10.5 ± 3.7 mm (range 4.6-22.8mm). The PET data were reconstructed with baseline OSEM algorithm, with OSEM+PSF, with OSEM+TOF and with OSEM+PSF+TOF. A semi-quantitative analysis was performed using the maximum and mean SUV of lymph node metastases (SUVmax and SUVmean) and mean SUV of normal lung tissue (SUVlung). We also evaluated image quality using the signal-to-noise ratio in the liver (SNRliver).
  
  
  RESULTS
  Both PSF and TOF increased the SUV of lymph node metastases. The combination of PSF and TOF increased the SUVmax by 43.3% and the SUVmean by 31.6% compared with conventional OSEM. By contrast, the SUVlung was not influenced by PSF and TOF. TOF significantly improved the SNRliver.
  
  
  CONCLUSIONS
  PSF and TOF both increased the SUV of lymph node metastases. Although PSF and TOF are considered to improve small-lesion detectability, it is important to be aware that PSF and TOF influence the accuracy of quantitative measurements.
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; Institute of Biomedical Research and Innovation, 2-2, Minatojima-Minamimachi, Chuo-ku, Kobe 650-0047, Japan. Electronic address: golilin5@gmail.com.
authors.forename: Go
authors.initials: G
authors.lastname: Akamatsu
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. Electronic address: kamitsumo@gmail.com.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Mitsumoto
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. Electronic address: bock.0517.tt@gmail.com.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: Department of Medical Technology, Kyushu University Hospital, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. Electronic address: yuji1006@med.kyushu-u.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Tsutsui
authors.affiliation: Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. Electronic address: sbaba127@radiol.med.kyushu-u.ac.jp.
authors.forename: Shingo
authors.initials: S
authors.lastname: Baba
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. Electronic address: msasaki@hs.med.kyushu-u.ac.jp.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Sasaki
mesh_terms: D000465:Algorithms; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008207:Lymphatic Metastasis / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008954:Models, Biological; D015233:Models, Statistical; D049268:Positron-Emission Tomography / Q000379:methods* / Q000592:standards; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: FDG-PET; Lymph node metastasis; Point-spread function; Standardized uptake value; Time-of-flight