'Relationship between thermal dose and cell death for "rapid" ablative and "slow" hyperthermic heating'

Area of Science:

• Oncology
• Biophysics
• Cell Biology

Background:

• Thermal isoeffective dose (TID) is crucial for predicting biological effects of thermal therapies.
• Classical TID methods are not well-validated for rapid thermal ablation (>55°C).
• Accurate dosimetry is needed for both hyperthermic and ablative thermal exposures.

Purpose of the Study:

• To compare classical TID quantification with a temperature-adjusted method for predicting cell survival.
• To validate a novel dosimetry approach for rapid thermal ablation.
• To improve the prediction of biological effects from varying thermal exposure strategies.

Main Methods:

• In vitro cell survival assays (MTT) were performed on colon cancer cell lines (HCT116, HT29).
• Cells were exposed to hyperthermic (>2 min, <50°C) and rapid ablative (<10 sec, >55°C) thermal treatments.
• Thermal isoeffective dose was calculated using a constant (R_CEM>43°_C=0.5) and a temperature-dependent Arrhenius model (R_CEM(T)).

Main Results:

• Rapid exposures at 340-550 CEM₄₃ (R_CEM>43°_C=0.5) resulted in 12±6% viability, while slow exposures led to undetectable viability.
• Arrhenius analysis yielded R_CEM=0.42*e^0.0041*T, which better predicted cell survival than the constant R_CEM>43°_C=0.5.
• Cell viability was undetectable above 305±10 CEM₄₃ using the revised temperature-adjusted TID.

Conclusions:

• A temperature-adjusted TID, informed by Arrhenius kinetics, provides a consistent, heating-strategy-independent predictor of cell viability.
• This revised dosimetry approach improves the accuracy of predicting biological effects from ablative thermal exposures.
• The findings support the use of temperature-adjusted TID for more precise thermal therapy planning.