title: Absorption, distribution and excretion of intravenously injected (68)Ge/ (68)Ga generator eluate in healthy rats, and estimation of human radiation dosimetry.
abstract: BACKGROUND
  This study evaluated the absorption, distribution, and excretion of Gallium-68 ((68)Ga) radionuclide after a single intravenous (i.v.) injection of (68)Ge/(68)Ga generator eluate in healthy rats. Additionally, human radiation doses were estimated from the rat data.
  
  
  METHODS
  Twenty-one female and 21 male Sprague-Dawley rats were i.v. injected with 47 ± 4 MBq of (68)Ge/(68)Ga generator eluate, and the radioactivity of excised organs was measured using a gamma counter at 5, 30, 60, 120, or 180 min afterwards (n = 3-7 for each time point). The radioactivity concentration and plasma pharmacokinetic parameters were calculated. Subsequently, the estimates for human radiation dosimetry were determined. Additionally, 4 female and 5 male rats were positron emission tomography (PET) imaged for in vivo visualization of biodistribution.
  
  
  RESULTS
  (68)Ga radioactivity was cleared relatively slowly from blood circulation and excreted into the urine, with some retention in the liver and spleen. Notably, the (68)Ga radioactivity in female genital organs, i.e., the uterus and ovaries, was considerable higher compared with male genitals. Extrapolating from the female and male rat (68)Ga data, the estimated effective dose was 0.0308 mSv/MBq for a 57-kg woman and 0.0191 mSv/MBq for a 70-kg man.
  
  
  CONCLUSIONS
  The estimated human radiation burden of the (68)Ge/(68)Ga generator eluate was slightly higher for females and similar for males as compared with somatostatin receptor ligands (68)Ga-DOTANOC, (68)Ga-DOTATOC, and (68)Ga-DOTATATE, which is probably due to the retention in the liver and spleen. Our results revealed some differences between female and male rat data, which, at least in part, may be explained by the small sample size.
authors.affiliation: Turku PET Centre, Turku University Hospital, University of Turku, FI-20521, Turku, Finland, akauti@utu.fi.
authors.forename: Anu
authors.initials: A
authors.lastname: Autio
authors.forename: Helena
authors.initials: H
authors.lastname: Virtanen
authors.forename: Tuula
authors.initials: T
authors.lastname: Tolvanen
authors.forename: Heidi
authors.initials: H
authors.lastname: Liljenbäck
authors.forename: Vesa
authors.initials: V
authors.lastname: Oikonen
authors.forename: Tiina
authors.initials: T
authors.lastname: Saanijoki
authors.forename: Riikka
authors.initials: R
authors.lastname: Siitonen
authors.forename: Meeri
authors.initials: M
authors.lastname: Käkelä
authors.forename: Andrea
authors.initials: A
authors.lastname: Schüssele
authors.forename: Mika
authors.initials: M
authors.lastname: Teräs
authors.forename: Anne
authors.initials: A
authors.lastname: Roivainen