Millimeter-Wave Heating in In Vitro Studies: Effect of Convection in Continuous and Pulse-Modulated Regimes

Area of Science:

• Bioelectromagnetics
• Thermal Physics
• Electromagnetic Wave Propagation

Background:

• Millimeter waves (MMW) exhibit shallow penetration and non-uniform illumination in in vitro settings.
• Non-uniform specific absorption rate (SAR) distributions induce convective currents in liquids.
• These convective currents significantly influence transient and steady-state temperature distributions.

Purpose of the Study:

• To analyze the effect of convection on temperature dynamics during MMW exposure.
• To investigate MMW exposure in continuous-wave (CW) and pulsed-wave (PW) amplitude-modulated regimes.
• To understand how liquid volume and pulse duration affect MMW-induced thermal effects.

Main Methods:

• Utilized micro-thermocouples to measure temperature changes.
• Exposed liquid samples to MMW in CW and PW regimes.
• Varied MMW specific absorption rate (SAR), liquid volume, and pulse duration to observe effects.

Main Results:

• Temperature rise kinetics showed a peak preceding convection, shifting to shorter times with increased SAR.
• Liquid volume influenced convection, with larger volumes triggering it earlier and showing faster cooling post-exposure.
• In PW regimes, pulse duration affected heat pulse amplitude and cooling rate, altering average temperature.

Conclusions:

• Convection plays a critical role in MMW-induced temperature dynamics in liquids.
• Liquid volume and MMW exposure parameters (SAR, pulse duration) are key factors modulating convective heat transfer.
• Findings are crucial for accurate thermal dosimetry and understanding MMW-tissue interactions.