Radiation exposure by [F18]Florbetaben, a new PET tracer for detection of cerebral β-amyloid in Caucasian and Asian healthy volunteers

Objectives Florbetaben is a new PET tracer for detection of β-amyloid in the brain. To assess the radiation exposure upon application of the radioligand, the biodistribution, organ doses (OD) and the effective dose (ED) were determined in two identical clinical phase-1-trials.

Methods Whole body dosimetry of Florbetaben was performed in 17 German# (64.2±5.3yrs.; 9f, 8m) and 18 Japanese## (61.8±4.9yrs.; 7f, 11m) healthy volunteers. Both cohorts were imaged up to 7h post i.v. injection of 300 MBq±20% Florbetaben (specific activity <5 µg tracer mass (TM): n=9#, n=9##; >50 to ≤55 µg TM: n=8#, n=9##) in 3D mode with 8 or 9 bed positions (BP) per frame, 1min/BP, correction for measured attenuation and iterative reconstruction. All relevant organs were defined by volumes of interest. Exponential curves were fitted to the time-activity-data. ODs and ED were calculated using the adult male model# and the 15-year-old male model## (OLINDA).

Results The gallbladder got the highest OD (137.0±54.9#; 152.0±63.5##), followed by the urinary bladder (69.5±21.2#; 122.5±28.4##). The highest contributions to the ED were derived from the lower large intestine (4.21±1.37#; 6.02±1.23##) and the ur. bladder (3.48±1.06#; 6.10±1.42##). The ED by i.v. application of the above radioactive dose equaled 19.3±1.40# and 26.9±1.59##* µSv/MBq (*difference due to different body masses in both cohorts: 73.8±10.4#; 58.8±8.3##kg). No significant difference in both cohorts between the two groups of TMs was found (p>0.05#,##).

Conclusions The ED upon i.v. application of 300 MBq is 5.80±0.42# and 8.08±0.48## mSv. This is within the range of that resulting from application of other [F18]-labeled compounds. These favorable dosimetry data encourage the further development of Florbetaben as a clinical tool for PET imaging of β-amyloid.

Research Support The trial was sponsored by Bayer Healthcare