title: Repeatability of gallium-68 DOTATOC positron emission tomographic imaging in neuroendocrine tumors.
abstract: OBJECTIVE
  To evaluate the repeatability of gallium-68 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic (DOTA)-D-Phe1-Try3-octreotide (68Ga-DOTATOC) positron emission tomography (PET) in neuroendocrine tumors.
  
  
  METHODS
  Five patients with neuroendocrine tumors were imaged with 68Ga-DOTATOC PET twice within 5 days. Maximum and mean standardized uptake values (SUVmax and SUVmean) and kinetic parameters (K-Patlak and K-influx) of target lesions were measured. The repeatability of these measurements was investigated.
  
  
  RESULTS
  Forty-seven target lesions were identified on whole-body PET and 21 lesions on dynamic images. There was excellent repeatability with intraclass correlation coefficient of 0.99 for SUVmax, SUVmean, and K-Patlak, and 0.85 for K-influx. The median absolute percent differences and the interquartile ranges (IQR) between 2 scans for SUVmax and SUVmean were 7.4% (IQR, 14.1%) and 9.3% (IQR, 10.6%), respectively. The median absolute percent differences for K-Patlak and K-influx were 12.5% (IQR, 12.6%) and 29.9% (IQR, 22.4%), respectively. The SUVmax of target lesions did not differ by more than 25% between the 2 scans.
  
  
  CONCLUSIONS
  68Ga-DOTATOC PET imaging of neuroendocrine tumors is highly reproducible. A difference of more than 25% in SUVmax represents a change that is larger than the measurement error observed on repeated studies and should reflect a significant change in the biological character of the tumor.
authors.affiliation: Department of Radiology, University of Iowa Carver College of Medicine, Iowa City, IA 52241, USA. yusuf-menda@uiowa.edu
authors.forename: Yusuf
authors.initials: Y
authors.lastname: Menda
authors.forename: Laura L Boles
authors.initials: LL
authors.lastname: Ponto
authors.forename: Michael K
authors.initials: MK
authors.lastname: Schultz
authors.forename: Gideon K D
authors.initials: GK
authors.lastname: Zamba
authors.forename: G Leonard
authors.initials: GL
authors.lastname: Watkins
authors.forename: David L
authors.initials: DL
authors.lastname: Bushnell
authors.forename: Mark T
authors.initials: MT
authors.lastname: Madsen
authors.forename: John J
authors.initials: JJ
authors.lastname: Sunderland
authors.forename: Michael M
authors.initials: MM
authors.lastname: Graham
authors.forename: Thomas M
authors.initials: TM
authors.lastname: O'Dorisio
authors.forename: M Sue
authors.initials: MS
authors.lastname: O'Dorisio
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005710:Gallium Radioisotopes; D006801:Humans; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000175:diagnosis*; D015282:Octreotide / Q000031:analogs & derivatives*; D009942:Organometallic Compounds; D049268:Positron-Emission Tomography / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: C499142:Ga(III)-DOTATOC; D005710:Gallium Radioisotopes; D009942:Organometallic Compounds; D015282:Octreotide