Authors :
Presenting Author: Sirisha Nouduri, B.S. – University of Pittsburgh School of Medicine
Francesco Cardinale, MD – “Claudio Munari” Center for Epilepsy Surgery
Faical Isbaine, PhD – DIXI Medical
John Gale, PhD – DIXI Medical and Neurolab
Jorge González-Martínez, MD,PhD – University of Pittsburgh Medical School
Rationale:
Stereoelectroencephalography (SEEG) is the standard of care for localizing the epileptogenic zone (EZ) in patients with drug-resistant epilepsy when non-invasive modalities are inconclusive. In both European practice and a growing number of U.S. centers, SEEG-guided radiofrequency thermal coagulation (RF-TC) has emerged as a minimally invasive option that also provides real-time validation of the presumed EZ. By leveraging the implanted SEEG electrodes, RF-TC enables focal ablation of epileptogenic tissue at the bedside, often immediately before electrode explantation. Despite its increasing use, RF-TC remains underutilized in part due to the lack of standardized parameters governing lesion size and reproducibility. A critical translational gap exists in understanding how ablation impedance and duration interact to influence lesion geometry. To address this, our study employs a reproducible egg-white model to systematically evaluate how these parameters affect lesion dimensions—an essential step toward optimizing protocols and expanding its integration into clinical workflows.
Methods:
These experiments were conducted using a proprietary DIXI RF generator (non-FDA approved) and egg-white bench model maintained at 37°C ± 1°C. RF-TC lesions were created using the DIXI MICRODEEP electrodes by setting the RF power output to 5.7W, and ablation durations to 30, 60, 90 and 120 seconds(s). For each ablation time, the dimensions and impedances were recorded. All analyses were conducted with MATLAB (Mathworks, Natick, MA, USA) and Prism (Version 9.4.0, Graphpad Software LLC, San Diego, CA, USA).
Results:
A total of 75 ablations were performed across the 4 groups of durations. The mean width and length (W/L) measured was 2.2/5.0 mm, 2.4/5.8 mm, 2.5/5.9 mm and 2.7/6.3 mm respectively for the 30s, 60s, 90s and 120s duration groups. The measured impedances ranged from 326 to 380 Ω. Two-way ANOVAs demonstrated that both duration and impedance factored in lesion diameter and length (p< 0.01 for each independent factor for both two-way ANOVA’s). Furthermore, a multiway ANOVA revealed a trend of increasing lesion width with longer ablation durations; this trend was significant for the lesion diameter generated by the 120s group relative to the 30s and 60s duration group (p< 0.001 and p< 0.05 respectively). Linear regression analysis further indicated that, in all groups except the 120s group, lesion diameter increased with higher contact impedance. This suggests that, in the 120s condition, the lesion continued to form on lower impedance contacts as a function of time.
Conclusions:
Our findings indicate that contact impedance and ablation duration significantly affect the length and width of ablations generated. Our results indicate that during ablation durations of 120s, higher impedance contacts appeared to reach saturation, while lower impedance contacts continued to grow, suggesting an impedance dependent response. The egg-white model, while common in RF-TC studies is far from being equivalent to the brain complexity, as such modeling and in-vivo studies are needed to better understand the biophysics of RF-TC.
Funding:
Dixi Medical USA