Abnormally high diffuse activity on bone scintigram. The importance of exposure time for its recognition.

When the bone scintigram reveals high diffuse skeletal activity, it may be misinterpreted as normal. Some authors have reported such scintigrams in articles entitled "Significance of absent or faint kidney sign on bone scan" and "False negative bone scintigram". Three cases with bone metastasis showing high diffuse skeletal activity are presented in this paper. The recognition of abnormally high diffuse skeletal activity on bone scintigrams is discussed. The exposure time of all three cases was short when compared with normal cases, when the bone image was taken with a preset count. Therefore, exposure time is very important for objective differentiation between the cases showing high diffuse skeletal activity and normal cases.