Feasibility of a quality assurance system for electromagnetic field therapy

This study was designed to evaluate the effectiveness of a newly developed quality assurance system for electromagnetic field therapy called tumor treating fields therapy, which uses an alternating electric field to treat cancer based on an intermediate frequency of 100–300 kHz. The quality assurance system for electromagnetic field therapy consisted of a water phantom, a probe, and a digital data acquisition (DAQ) board. Low intensity alternating electric fields (200 kHz, 0–.1 V/cm) were created within the water phantom using a function generator and a high voltage amplifier. The electric potential formed inside the water phantom was measured using the probe and DAQ board. The electric field intensity was derived by measuring the electric potential at the 190 points (19 × 10 cm²) of the midplane. Accuracy was evaluated by gamma index analysis, which compared the measured electric field and the simulation result. The mean difference between the simulation result and the measured electric potentials within the water phantom was 0.31 V. The gamma passing rate for the tolerance levels of 0.5 V/5 mm was 95.5% for electric potential comparison showing good agreement between simulation and experimental results. The mean difference between the electric field distribution within the water phantom and the simulated values was 0.09 V/cm and the gamma passing rate for the tolerance levels of (0.2 V/cm)/5 mm was ~ 97.3%. These results confirmed the feasibility of the quality assurance system for electromagnetic field therapy.