To assess the radiation exposure of the investigator during navigated fusion of nuclear medicine images with ultrasound after application of I-124. Dosimetry with two different types of thermoluminescent detectors (TLD) was performed in 25 patients. The dose rate at the patient's neck was measured with a calibrated dose rate meter (DRM) and served as the standard of reference. The average exposure per investigation at the patient's neck measured by LiF:Mg,Cu,P TLDs (cumulative: 212 μSv), LiF:Mg,Ti TLDs (cumulative: 112 μSv) and DRM (cumulative: 150.3 μSv). The radiation exposure of the hand during navigated fusion of nuclear medicine imaging with 124I and ultrasound with a mean duration of 13 min is low and comparable between different methods. Yearly examinations are not expected to add a relevant cumulative risk.