title: Factors affecting standardized uptake value (SUV) of positron emission tomography (PET) imaging with l8F-FDG.
abstract: OBJECTIVE
  The purpose of the study was to study factors affecting SUV of PET imaging with 18F-FDG.
  
  
  METHODS
  PET/CT Biograph 64 was used to acquire the data. A NEMA PET phantom with 6 spheres varying in diameter from 10 to 37 mm was used to mimic the human body and tumors. Background activity of 18F in the phantom was 0.14 microCi/ml and tumor-to-background ratios (TBR) of 2:1, 5:1 and 10:1 were studied. For each TBR, thirty sinograms were acquired with 3-min scan durations. Different scan durations varying from 3 to 20 min using a TBR of 5:1 were studied and three datasets of each scan time were collected Sinograms were reconstructed using the Ordered Subset Expectation Maximization (OSEM) algorithm with 5 mm Full-Width-at-Half-Maximum (FWHM) Gaussian filtering. Sinograms at TBR of 5:1 were reconstructed by varying the number of iterative updates of OSEM (N) from 8 to 168 and SUVavg and SUVmax were measured. The percentage of underestimation of SUVs was used to study the effect of tumor size and TBR. Intraclass correlation coefficient (ICC) was used to test the reliability of SUVmax with different scan durations.
  
  
  RESULTS
  The results showed that both the SUVavg and SUVmax rapidly increased when N was <48 and slightly increased afterwards. At TBRs ranging from 2:l to 10:1, the percentages of underestimation of SUVmax ranged from 8.17 to 22.46 and that of SUVavg were ranged from 41.44 to 52.33 for 37-mm sphere and from 40.38 to 54.52 and from 48.97 to 67.73 for 10-mm sphere respectively. Different scan durations gave reliable SUVs(max) with ICC of 0.996.
  
  
  CONCLUSIONS
  SUVs increased as N increased The percentage of underestimation of the SUV depended on tumor size and TBR. Scan duration did not affect SUVs.
authors.affiliation: Department of Radiological Technology, Faculty of Medical Technology, Mahidol University, Bangkok, Thailand.
authors.forename: Kanyalak
authors.initials: K
authors.lastname: Wiyaporn
authors.forename: Chiraporn
authors.initials: C
authors.lastname: Tocharoenchai
authors.forename: Pawana
authors.initials: P
authors.lastname: Pusuwan
authors.forename: Tawatchai
authors.initials: T
authors.lastname: Ekjeen
authors.forename: Suraphong
authors.initials: S
authors.lastname: Leaungwutiwong
authors.forename: Suchera
authors.initials: S
authors.lastname: Thanyarak
mesh_terms: D000465:Algorithms; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019047:Phantoms, Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D014055:Tomography, Emission-Computed / Q000706:statistics & numerical data*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18