Abstract
The 100-mW Tsing-Hua Mobile Educational Reactor, originally designed for educational and training purposes, has been converted for in vivo prompt gamma-ray activation medical diagnosis. New experimental parts and equipment have been installed to localize the external neutron beam and reduce the phantom radiation doses to the irradiated organ. The sensitivity to internal toxic and essential elements in vivo is improved by a factor of 4 and the total doses are reduced by a factor of 2 compared to those obtained in preliminary studies using the original configuration.