Considerations for thermal injury analysis for RF ablation devices

Area of Science:

• Biomedical Engineering
• Computational Modeling
• Medical Physics

Background:

• Accurate estimation of lesion size is critical for radiofrequency ablation (RFA) treatment planning.
• Current computational methods for predicting RFA lesion size lack direct comparative evaluation.
• Three common techniques—iso-temperature contours, cumulative equivalent minutes, and Arrhenius-based thermal injury—are frequently used.

Purpose of the Study:

• To evaluate and compare the accuracy of three computational methods for predicting lesion size in radiofrequency ablation.
• To determine the most physiologically relevant method for estimating thermal injury in RFA applications.

Main Methods:

• A geometric model of a multi-tine ablation electrode was developed.
• Simulations using a hybrid finite element technique calculated temperature and tissue injury profiles.
• Iso-temperature thresholds, cumulative equivalent minutes, and Arrhenius-based formulations (recursive and non-recursive) were applied.

Main Results:

• Iso-temperature and cumulative equivalent minute methods significantly overestimate lesion size compared to recursive thermal injury calculations.
• Non-recursive Arrhenius calculations underestimate lesion volume.
• Recursive thermal injury calculations show strong correlation with in vitro pathologic lesion volume measurements.
• Lesion width and depth are insufficient metrics for characterizing treatment volume with multi-tine devices.

Conclusions:

• Recursive thermal injury calculations provide the most physiologically relevant estimation of lesion size for hepatic tumor RFA.
• Iso-thermal and cumulative equivalent minute methods can lead to significant errors in lesion size estimation.
• Accurate computational modeling is essential for optimizing RFA treatment planning and outcomes.