Calibration and evaluation of a transportable in vivo monitoring system for accident monitoring of internal contamination.

A transportable in vivo monitoring system has been constructed and calibrated. The system uses two hyper pure germanium detectors--one for measuring whole body activities, by measuring activity in the torso, and the second for determining activities of radioiodine in the thyroid. The optimum counting geometries have been determined and the system has been calibrated for subjects of different ages and builds. The complete system is transported in two trailers which are pulled by ordinary motor vehicles. The minimum detectable activity (MDA) for 137Cs in whole body for a 10 min counting interval at the 95% confidence level is 200 Bq. The MDA for a count of 131I in thyroid is 20 Bq. The system is capable of detecting activities that are equivalent to a dose of 1 mSv for a wide range of radionuclides.