Objective To study the radiation level in the surrounding of patients undergoing 99Tcm-MDP SPECT bone imaging and associated influencing factors and provide experimental data for the radiation safety of personnel around the patients.Methods A total of 367 patients undergoing whole-body bone imaging in Cancer Hospital,Chinese Academy of Medical Sciences were investigated to measure the ambient dose equivalent rate around the patients at different time and different distances from the patients,analyze the variations of ambient dose equivalent rate with time and distances,estimate the dose level at different distances around the patients,and evaluate the radiation dose to personnel around the patients.Results The ambient dose equivalent rate around the patient decreased exponentially with time;the effective half-life of 99Tcm in patients' body increased with time.The ambient dose equivalent rate varied by power function with increasing distance within 4 meters from the patient with the mean power value of -1.45.The radiation levels were 238.3 μSv at 0.5 m,99.7 μSv at 1 m,and 61.8 μSv at 1.5 m from the patient undergoing 99Tcm injection to its vanishing in patients' body.At different time points,the radiation doses at 0.5 m off the patient for 10 min were:9.9,3.0,1.9 μSv at 0,3 and 6 h,respectively.Conclusions The ambient dose equivalent rate around the patients undergoing 99Tcm-MDP SPECT bone imaging decrease rapidly with increasing time and distance.The patients can cause a certain degree of exposures to the surrounding personnel,but the exposure level is far lower than the relevant national standards.It is suggested that the patients should not receive other types of diagnosis and treatments spending lot of time and in close contact with medical staff while bone imaging being conducted on the same day.