Numerical Simulation on Microwave Rewarming of Cryopreserved Rabbit Kidney with Embedded Superparamagnetic Nanoparticles

BACKGROUND: Rewarming cryopreserved organs without detrimental damages is a task full of challenging, since devitrification-associated thermal stresses can cause uncontrollable injuries. The ideal rewarming method should obtain a uniform thermal field with a rapid warming rate enough to avoid devitrification. Microwave rewarming is considered to be the most promising method to rewarm cryopreserved organs safely. However, it is difficult to accurately predict the rewarming rates and temperature gradients in cryopreserved organs since the coupling of electromagnetic field and temperature field is changing during microwave rewarming process. OBJECTIVE: This study is to evaluate the feasibility of microwave rewarming of cryopreserved rabbit kidney embedded with superparamagnetic nanoparticles in a single-mode resonant cavity (434MHz, TE101 mode). MATERIALS AND METHODS: The Finite Element Method (FEM) was used to calculate the coupling of the electromagnetic field and temperature field in a microwave system composed of a rectangular resonant cavity, an antenna source, and a frozen rabbit kidney with temperature-dependent properties. Heat generated by water molecules and nanoparticles in the electromagnetic field of microwave cavity was calculated. RESULTS: The simulation results showed that, during the rewarming process of the sample phantom without nanoparticles, the rewarming rate was 29.45°C/min and the maximum temperature gradient in the sample was 2.23°C/mm. With nanoparticles embedded in the sample at the same power input to the microwave cavity, the rewarming rate was increased to be 41.38°C/min and the maximum temperature gradient in the sample was 1.93°C/mm. CONCLUSION: The study indicates that the use of nanoparticles increases the rewarming rate and temperature uniformity.