The effect of hyperthermia-induced tissue conductivity changes on electrical impedance temperature mapping

Area of Science:

• Biophysics
• Medical Physics
• Oncology

Background:

• Tissue electrical conductivity changes with temperature (Tissue Temperature Coefficients, TCS).
• Therapeutic hyperthermia utilizes controlled heating of tissues.
• Non-temperature-related conductivity changes (e.g., edema, cellular alterations) can impede accurate temperature monitoring.

Purpose of the Study:

• To estimate errors in temperature mapping using electrical impedance measurements when non-TC effects are ignored.
• To present a method for differentiating non-TC effects from TC effects using conductance measurements.
• To suggest conductance measurements for monitoring hyperthermia treatments based on cellular changes.

Main Methods:

• Analysis of errors in temperature mapping using electrical impedance measurements in EMT6 tumors (excised and in vivo).
• Development of a method using conductance measurements to distinguish between temperature-dependent and non-temperature-dependent conductivity changes.
• Exploration of conductance measurements for monitoring hyperthermia-induced cellular changes.

Main Results:

• Quantified potential inaccuracies in temperature mapping due to ignoring non-TC effects.
• Demonstrated a technique to differentiate TC effects from non-TC effects, extending the utility of TC-based temperature estimation.
• Established a basis for using conductance measurements to track hyperthermia treatment progression.

Conclusions:

• Ignoring non-TC effects leads to significant errors in hyperthermia temperature mapping.
• A novel method allows for accurate temperature monitoring by distinguishing TC and non-TC effects.
• Conductance measurements offer a promising, temperature-independent approach to monitor hyperthermia treatments.