title: Fetal dose estimates for (18)F-fluoro-L-thymidine using a pregnant monkey model.
abstract: Estimating the radiation dose received by the fetus from nuclear medicine procedures is important because of the greater sensitivity of rapidly developing fetal tissues to ionizing radiation. (18)F-fluoro-L-thymidine (FLT) uptake is related to cellular proliferation and is currently used to monitor tumor progression and response to therapy. This study was undertaken to estimate-on the basis of biodistribution data obtained by PET/CT in pregnant rhesus monkeys-radiation absorbed dose to a human fetus administered (18)F-FLT.
  
  
  METHODS
  Three pregnant rhesus macaques (gestational age, 113 +/- 8 d) were administered (18)F-FLT and imaged for 2 h on a PET/CT scanner. Time-activity curves for maternal and fetal organs were generated in anatomic regions of interest identified via CT. Doses were estimated using OLINDA/EXM and the 6-mo-pregnant human model.
  
  
  RESULTS
  The extrapolated whole-body maternal dose obtained, 11.4 microGy/MBq, is similar to the previously reported adult female dose of 15.6 microGy/MBq. The estimated total-body dose to a human fetus is 24 microGy/MBq. Significant long-term (18)F-FLT accumulation in fetal liver resulted in a fetal liver dose of 53 microGy/MBq.
  
  
  CONCLUSIONS
  The fetal dose estimate in a 6-mo-pregnant human using (18)F-FLT is slightly greater than that reported for (18)F-FDG. (18)F-FLT trapping in the fetal liver should be considered in the risk-benefit analysis of (18)F-FLT PET examination in pregnant patients.
authors.affiliation: Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA.
authors.forename: Rachel M
authors.initials: RM
authors.lastname: Bartlett
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Nickles
authors.forename: Todd E
authors.initials: TE
authors.lastname: Barnhart
authors.forename: Bradley T
authors.initials: BT
authors.lastname: Christian
authors.forename: James E
authors.initials: JE
authors.lastname: Holden
authors.forename: Onofre T
authors.initials: OT
authors.lastname: DeJesus
mesh_terms: D000328:Adult; D000818:Animals; D015224:Dideoxynucleosides / Q000009:adverse effects*; D005260:Female; D005333:Fetus / Q000000981:diagnostic imaging / Q000528:radiation effects*; D006801:Humans; D023421:Models, Animal; D049268:Positron-Emission Tomography / Q000009:adverse effects*; D011247:Pregnancy; D011829:Radiation Dosage; D019275:Radiopharmaceuticals / Q000009:adverse effects*; D018570:Risk Assessment; D013045:Species Specificity; D014018:Tissue Distribution; D014057:Tomography, X-Ray Computed / Q000009:adverse effects
chemical_list: D015224:Dideoxynucleosides; D019275:Radiopharmaceuticals; C002854:alovudine