Huygens' based re-simulation for enabling MRI adaptive hyperthermia

OBJECTIVE: The efficacy of hyperthermia treatment (HT) is closely linked to the achieved temperature distribution. Patient-specific hyperthermia treatment planning (HTP) is employed to optimize heating, however its effectiveness is hindered by challenges in replicating the planned patient positioning during treatment. A promising alternative is the rapid re-simulation of electric fields based on the actual patient anatomy within the applicator, as visualized by magnetic resonance imaging (MRI). However, current full-wave HTP methods are too slow to incorporate MRI data in real-time, and patients cannot be kept waiting long between being scanned and treated. 

Approach: We investigated the potential of the Huygens' principle to accelerate HTP. Full-wave simulations were performed in Sim4Life using both cylindrical phantoms and also twelve patient models within the MRCollar applicator. Optimization targeted the highest target-to-hotspot quotient (THQ). These simulations were used to evaluate the Huygens' approach as a fast simulation method and in compensating for patient displacement.

Main results: Simulation times were significantly reduced - from 92 minutes to 4.5 minutes - without compromising accuracy. Accurate source modelling required a patient-shaped muscle-equivalent load. Following re-simulation, THQ bias decreased from 43.6% to 4.3%.

Significance: Applying the Huygens' approach in electromagnetic simulations enables online adaptive HT by recalculating electric fields at the actual treatment position. This method mitigates the impact of positioning inaccuracies, reducing THQ bias to -3.6% and achieving an average THQ error of only -0.6%.&#xD.