ID: 2300

• Title:
  Real-Time Monitoring of Ablation Growth with Rapid Impedance Spectroscopy
  
  Authors:
  

  Campelo, Sabrina - Virginia Tech, USA
  
  Salameh, Zaid - Virginia Tech, USA
  
  Santos Gomes da Silva, Pedro - Universidade Federal de Santa Catarina, Brazil
  
  Davalos, Rafael - Virginia Tech, Georgia Tech, USA

  
  
  Abstract:
  Introduction: High-Frequency Irreversible Electroporation (H-FIRE) utilizes the application of intense biphasic pulsed electric fields, inducing nanoscale structural defects in cell membranes. This process yields a precisely localized tissue ablation zone and may be used to specifically eliminate malignant tissues. Despite the many advancements in electroporation-based ablation techniques, one of the major clinical challenges that remains is the absence of a real-time mechanism that can reliably indicate an acceptable end time to treatment. In addressing this challenge, a novel technology referred to as Fourier Analysis Spectroscopy (FAST) has been previously proposed [1]. The primary goal behind FAST is to leverage real-time electrical impedance spectroscopy (EIS) for monitoring the progression of the ablation growth. In the context of this investigation, we aim to maximize ablation growth while concurrently surveilling potential thermal effects.
  
  
  
  Materials and Methods: H-FIRE ablation was performed on ex vivo perfused porcine liver tissue using a single-insertion bipolar probe. To monitor the treatment's progress, a specialized rapid EIS waveform was integrated between individual H-FIRE bursts allowing for continuous tracking of electrical impedance changes across frequencies ranging from approximately 1 kHz to 1 MHz. Six hours following treatment, the liver tissues were stained with triphenyl tetrazolium chloride, sliced, and ablation lesions were measured. A variety of burst number protocols were utilized to generate different sized ablation lesions, allowing for us to correlate the size of the ablation lesions and the corresponding changes in low-frequency impedance. Additionally, temperature was monitored and corelated with changes in high-frequency impedance changes.
  
  
  
  Results and Discussion: In liver tissue, 10, 25, 50, 60, 100, and 300 bursts were applied with ablation areas of 0.69 ± 0.34 cm2, 1.58 ± 0.32 cm2, 1.69 ± 0.59 cm2, 1.65 ± 0.41 cm2, 1.90± 0.53 cm2, and 1.53 ± 0.34 cm2 respectively. Our correlation analysis revealed a statistically significant positive correlation between low-frequency impedance change and ablation size (r = 0.4108, p = 0.0104). Nonlinear regression with exponential functions were employed to determine a correlation between ablation saturation and impedance saturation. The time constant tau for ablation growth (3τ) and the 95% impedance saturation were within each of their respective 90% confidence intervals, signifying a direct correlation between the two. The exponential coefficient tau for ablation and the tau for impedance change were 31.07 ± 3.34 and 32.37 ± 14.03 respectively. Additionally, another correlation study revealed a statistically significant positive correlation between high-frequency impedance changes and an increase in temperature during treatment (r = 0.5457, p = 0.0001).
  
  
  
  Conclusion: These preliminary results suggest that we may we able to successfully incorporate FAST technology during a treatment to monitor both ablation growth and rises in temperature in real-time.
  
  
  
  
  
  
  
  
  
  Keywords:
  electroporation, electrical impedance spectroscopy
  
  Refs:
  [1] Lorenzo MF, IEEE TBME 2020, 68(5) p:1536-1546
  
  Topic 1:
  6. Cancer treatment and tumor ablation
  
  Topic 2:
  13. Pulsed power devices and methods