Handling of radioisotopes may cause external and internal contamination to occupational workers while using radiation for medical purposes. This research aims to monitor the internal hazard of occupational workers who handle 131I. Two methods are used: in vivo or direct method and in vitro or indirect method. https://www.roneverhart.com/NeOn-Zero-Lefty-M390-BLADE-TITANIUM-HANDLE-MRBS-p11472/