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Published on: June 8, 2018
Irreversible Electroporation: Defining the MRI Appearance of the Ablation Zone With Histopathologic Correlation in a
Ely R Felker1, Isabel Dregely1, Dong Jin Chung1
11 Department of Radiology, Ronald Reagan-UCLA Medical Center, 757 Westwood Plaza, Ste 1638, Los Angeles, CA 90095.
Objective:
The purpose of this study is to evaluate the MRI appearance of the irreversible electroporation zone in porcine liver, with histopathologic correlation.
Materials And Methods:
Nine irreversible electroporation ablations were percutaneously created in two Yorkshire pigs. Irreversible electroporation was performed with a bipolar 16-gauge electrode with 3-cm exposure tip and fixed 8-mm interpolar distance. Gadoxetate disodium-enhanced 3-T MRI was performed 50 hours after irreversible electroporation. Livers were harvested immediately after MRI for histopathologic analysis. Ablation zone size was measured on each pulse sequence and correlated with pathologic ablation zone size. Qualitative MRI features of the ablation zone were assessed, and contrast-to-noise ratios (CNRs) were calculated. Statistical analysis included Pearson correlation and t tests.
Results:
Histopathologically, three distinct layers were present in the irreversible electroporation ablation zone: an inner layer of coagulative necrosis (hyperintense at T1- and T2-weighted imaging and nonenhancing), a middle layer of congestion and hemorrhage (hypointense at T1-weighted imaging, hyperintense at T2-weighted imaging and DWI, and progressively enhancing but hypointense at the hepatobiliary phase), and a peripheral layer of inflammation (hyperintense at the arterial phase but isointense at all other sequences). The hepatobiliary phase ablation zone size showed the highest correlation with the pathologic ablation zone size (r = 0.973). This correlation was significant (p < 0.001). T2-weighted imaging had the highest lesion-to-normal tissue CNR.
Conclusion:
The irreversible electroporation ablation zone contains three distinct histopathologic zones, each with unique MRI features. T2-weighted imaging had the highest CNR, and the hepatobiliary phase had the strongest correlation with ablation zone size.
Insights
This study reveals distinct MRI features for irreversible electroporation (IRE) ablation zones in porcine liver. The hepatobiliary phase best correlates with ablation size, while T2-weighted imaging offers the highest contrast.
Area of Science:
- Radiology
- Medical Imaging
- Interventional Radiology
Background:
- Irreversible electroporation (IRE) is an emerging ablation technique.
- Accurate assessment of IRE ablation zones is crucial for treatment monitoring.
- Histopathologic correlation is essential for validating imaging findings.
Purpose of the Study:
- To evaluate the magnetic resonance imaging (MRI) appearance of the irreversible electroporation (IRE) zone in porcine liver.
- To correlate MRI findings with histopathologic results.
- To identify optimal MRI sequences for assessing IRE ablation zones.
Main Methods:
- Percutaneous IRE ablations were created in porcine livers.
- Gadoxetate disodium-enhanced 3-T MRI was performed 50 hours post-ablation.
- Ablation zone size and contrast-to-noise ratios (CNRs) were measured and correlated with histopathology.
Main Results:
- The IRE ablation zone exhibited three distinct histopathologic layers with unique MRI signal characteristics.
- The hepatobiliary phase MRI demonstrated the highest correlation (r=0.973) with pathologic ablation zone size.
- T2-weighted imaging yielded the highest lesion-to-normal tissue CNR.
Conclusions:
- The IRE ablation zone comprises three histopathologically distinct layers with characteristic MRI signatures.
- Hepatobiliary phase MRI is highly accurate for determining IRE ablation zone size.
- T2-weighted imaging is optimal for visualizing the ablation zone due to superior CNR.
