Evaluating tissue changes with ultrasound during radiofrequency ablation

Area of Science:

• Medical Imaging
• Biomedical Engineering
• Ultrasound Technology

Background:

• Radiofrequency (RF) ablation is a medical procedure used to remove or destroy abnormal tissue.
• Monitoring tissue changes during RF ablation is crucial for effective treatment and patient safety.
• Current methods for monitoring RF ablation may have limitations in real-time assessment of tissue response.

Purpose of the Study:

• To investigate the correlation between ultrasound echo frequency shifts and tissue temperature elevations during RF ablation.
• To estimate tissue changes, specifically ablation size, by analyzing these frequency shifts.
• To explore the potential of ultrasound as a real-time monitoring tool for RF ablation.

Main Methods:

• Experiments were conducted on tissue-mimicking phantoms and in-vitro turkey breast using a modified RF ablation system.
• Intermittent RF energy was applied, with continuous temperature measurement at the electrode tip.
• Ultrasound B-mode images and raw data were acquired, and an algorithm was used to measure spectral shifts in echo signals.
• The relationship between applied voltage, temperature, frequency shifts, and ablated area width was analyzed.

Main Results:

• Phantom experiments demonstrated positive frequency shifts with increasing temperature, dependent on the heating rate.
• A strong linear relationship (R(2) > 0.96) was observed between RF voltage and heated area width based on frequency changes.
• In-vitro experiments showed a significant correlation (R(2) = 0.84) between coagulated area width and the region of significant frequency shifts.
• A weaker correlation (R(2) = 0.4) was found between coagulated area width and direct temperature elevation.

Conclusions:

• Echo frequency shifts during RF ablation are correlated with both temperature elevations and the resulting ablated tissue dimensions.
• Ultrasound-based measurement of echo frequency shifts shows promise for real-time monitoring of RF heating and induced coagulation.
• Further research and validation are needed to fully establish ultrasound as a tool for intraoperative guidance in RF ablation procedures.