Key result
Experimental MWA SAR diverges considerably from computer simulations once tissue temperatures exceed 100 °C.
Experimental measurement of SAR during microwave ablation reveals changes at high temperatures not captured by standard simulations, suggesting the need for updated dielectric properties in computational models.
Simulations may underestimate SAR changes above 100 °C during ablation; leaves open refinement of dielectric properties in computational models.
INTRODUCTION: For computational models of microwave ablation (MWA), knowledge of the antenna design is necessary, but the proprietary design of clinical applicators is often unknown. We characterised the specific absorption rate (SAR) during MWA experimentally and compared to a multi-physics simulation. METHODS: An infrared (IR) camera was used to measure SAR during MWA within a split ex vivo liver model. Perseon Medical's short-tip (ST) or long-tip (LT) MWA antenna were placed on top of a tissue sample (n = 6), and microwave power (15 W) was applied for 6 min, while intermittently interrupting power. Tissue surface temperature was recorded via IR camera (3.3 fps, 320 × 240 resolution). SAR was calculated intermittently based on temperature slope before and after power interruption. Temperature and SAR data were compared to simulation results. RESULTS: Experimentally measured SAR changed considerably once tissue temperatures exceeded 100 °C, contrary to simulation results. The ablation zone diameters were 1.28 cm and 1.30 ± 0.03 cm (transverse), and 2.10 cm and 2.66 ± -0.22 cm (axial), for simulation and experiment, respectively. The average difference in temperature between the simulation and experiment were 5.6 °C (ST) and 6.2 °C (LT). Dice coefficients for 1000 W/kg SAR iso-contour were 0.74 ± 0.01 (ST) and 0.77 (± 0.03) (LT), suggesting good agreement of SAR contours. CONCLUSION: We experimentally demonstrated changes in SAR during MWA ablation, which were not present in simulation, suggesting inaccuracies in dielectric properties. The measured SAR may be used in simplified computer simulations to predict tissue temperature when the antenna geometry is unknown.
No takes yet. Share an insight, caveat, or question.
Deshazer et al. (2016) studied Microwave ablation (ex vivo liver model) (n=6). Microwave ablation (short-tip or long-tip antenna) vs. Computer simulation was evaluated on Specific absorption rate (SAR) and temperature. Experimentally measured specific absorption rate during microwave ablation changed considerably once tissue temperatures exceeded 100 °C, contrary to computer simulation results.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: