Delicate animal experiments and microdose clinical trials using short-lived radioisotopes require rapid preparation with high accuracy and careful attention to safety within a limited timeframe. We have developed an open-style electrowetting on dielectric device containing dimple structures for the rapid preparation of radiolabelled reagents. The device was demonstrated by automatic preparation of a 99mTc-DTPA with high chelation efficiency (99.7 ± 0.13%). Additionally, we demonstrated the single photon emission computed tomography (SPECT)/Computed tomography (CT) imaging of mouse kidney using the 99mTc-DTPA prepared with the EWOD device. The obtained organ tomographic images were sufficient for the evaluation of mouse models for specific diseases. These results indicate that manual radiolabelling for small amount of nuclear medicine can be replaced by a process using the proposed EWOD device as a human error reduction technique.