title: Radiation dosimetry of beta-amyloid tracers 11C-PiB and 18F-BAY94-9172.
abstract: Beta-amyloid (Abeta) imaging has great potential to aid in the diagnosis of Alzheimer disease and the development of therapeutics. The radiation dosimetry of Abeta radioligands may influence their application; therefore, we calculated and compared the effective doses (EDs) of 11C-PiB and a new 18F-labeled ligand, 18F-BAY94-9172.
  
  
  METHODS
  Attenuation-corrected whole-body scans were performed at 0, 15, 30, 45, and 60 min after injection of 350+/-28 MBq (mean+/-SD) of 11C-PiB in 6 subjects and at 0, 20, 60, 120, and 180 min after injection of 319+/-27 MBq of 18F-BAY94-9172 in 3 subjects. Coregistered CT was used to define volumes of interest (VOIs) on the PET images. The source organs were the brain, lungs, liver, kidneys, spleen, and vertebrae. The VOIs for the contents of the gallbladder, urinary bladder, lower large intestine, upper large intestine, and small intestine were also defined. Total activity in each organ at each time point was calculated by use of reference organ volumes. The resultant time-activity curves were fitted with constrained exponential fits, and cumulated activities were determined. A dynamic bladder voiding model was used. The OLINDA/EXM program was used to calculate the whole-body EDs from the acquired data.
  
  
  RESULTS
  For 11C-PiB, the highest absorbed doses were in the gallbladder wall (44.80+/-29.30 microGy/MBq), urinary bladder wall (26.30+/-8.50 microGy/MBq), liver (19.88+/-3.58 microGy/MBq), and kidneys (12.92+/-3.37 microGy/MBq). The ED was 5.29+/-0.66 microSv/MBq. For 18F-BAY94-9172, the highest doses were also in the gallbladder wall (132.40+/-43.40 microGy/MBq), urinary bladder wall (24.77+/-7.36 microGy/MBq), and liver (39.07+/-8.31 microGy/MBq). The ED was 14.67+/-1.39 microSv/MBq.
  
  
  CONCLUSIONS
  The estimated organ doses for 11C-PiB were comparable to those reported in earlier research. With the doses used in published studies (300-700 MBq), the EDs would range from 1.6 to 3.7 mSv. The ED of 18F-BAY94-9172 was 30% lower than that of 18F-FDG and, at the published dose of 300 MBq, would yield an ED of 4.4 mSv. The dosimetry of both Abeta radioligands is suitable for clinical and research applications.
authors.affiliation: Centre for Positron Emission Tomography, Austin Hospital, Heidelberg, Victoria, Australia. graeme.okeefe@petnm.unimelb.edu.au
authors.forename: Graeme J
authors.initials: GJ
authors.lastname: O'Keefe
authors.forename: Timothy H
authors.initials: TH
authors.lastname: Saunder
authors.forename: Steven
authors.initials: S
authors.lastname: Ng
authors.forename: Uwe
authors.initials: U
authors.lastname: Ackerman
authors.forename: Henri J
authors.initials: HJ
authors.lastname: Tochon-Danguy
authors.forename: J Gordon
authors.initials: JG
authors.lastname: Chan
authors.forename: Sylvia
authors.initials: S
authors.lastname: Gong
authors.forename: Thomas
authors.initials: T
authors.lastname: Dyrks
authors.forename: Stefanie
authors.initials: S
authors.lastname: Lindemann
authors.forename: Gerhard
authors.initials: G
authors.lastname: Holl
authors.forename: Ludger
authors.initials: L
authors.lastname: Dinkelborg
authors.forename: Victor
authors.initials: V
authors.lastname: Villemagne
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Rowe
mesh_terms: D000368:Aged; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000814:Aniline Compounds / Q000493:pharmacokinetics; D052160:Benzothiazoles / Q000493:pharmacokinetics; D002250:Carbon Radioisotopes / Q000493:pharmacokinetics; D005260:Female; D005462:Fluorine Radioisotopes / Q000493:pharmacokinetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D049268:Positron-Emission Tomography; D011874:Radiometry; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D013267:Stilbenes / Q000493:pharmacokinetics; D013844:Thiazoles; D014018:Tissue Distribution
chemical_list: C475519:2-(4'-(methylamino)phenyl)-6-hydroxybenzothiazole; D016229:Amyloid beta-Peptides; D000814:Aniline Compounds; D052160:Benzothiazoles; D002250:Carbon Radioisotopes; D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D013267:Stilbenes; D013844:Thiazoles; C527756:4-(N-methylamino)-4'-(2-(2-(2-fluoroethoxy)ethoxy)ethoxy)stilbene