An individual in vivo monitor using seven Germanium detectors with a total
area of 24,000 mm(2) was prepared for Pb-210 skull measurements. System cal
ibration with anthropomorphic head phantoms and a straightforward efficienc
y estimation yielded a minimum detectable activity (MDA) of 6.7 Bq and a lo
wer limit of detection (LLD) of 14 Bq (CL: 95%). Two selected persons were
measured for 1 h each to reconstruct their cumulative radon exposure. From
the added pulse height spectrum a Pb-210 activity in the skull of 3.1+/-7.2
Bq (result with 95%-CL) was estimated, but clear conclusions on their rado
n exposure using a new metabolism model of lead in man could not be drawn.
Further improvements in the selection of highly exposed persons as well as
head calibration and Lackground reduction are necessary using this attempt
for retrospective exposure reconstruction.