Visualizing ex vivo radiofrequency and microwave ablation zones using electrode vibration elastography

Area of Science:

• Medical imaging
• Elastography
• Thermal ablation

Background:

• Electrode vibration elastography is an emerging shear wave imaging technique.
• Previous studies demonstrated its utility in delineating radiofrequency (RF) ablations.
• No prior studies have investigated its use for microwave (MW) ablations or radiological-pathological correlations with multiple observers.

Purpose of the Study:

• To evaluate the ability of electrode vibration elastography to visualize thermal ablation zones, specifically RF and MW ablations.
• To compare the delineation of ablation zones using shear wave velocity and maximum displacement images.
• To assess radiological-pathological correlations and interobserver variability.

Main Methods:

• RF and MW ablations were created in ex vivo bovine liver tissue.
• Elastographic images (shear wave velocity and maximum displacement) were compared to gross pathology.
• Overlap and interobserver variability were quantified using similarity measures.

Main Results:

• Elastographic imaging demonstrated correlation with gross pathology for both RF and MW ablations.
• Correlation of area estimates was higher for RF ablations (Pearson's r = 0.79–0.90) compared to MW ablations (Pearson's r = 0.54–0.70).
• Absolute relative differences in area between elastography and pathology ranged from 16.0% to 23.1%.

Conclusions:

• A statistically significant radiological-pathological correlation was observed, though correlation coefficients were lower for MW ablations compared to other imaging techniques.
• Multiple observers provided consistent delineations of thermal ablation zones.
• Electrode vibration elastography shows promise for imaging thermal ablations, but technique refinement is needed for clinical monitoring.