Irreversible Electroporation: Defining the MRI Appearance of the Ablation Zone With Histopathologic Correlation in a Porcine Liver Model.
OBJECTIVE
The purpose of this study is to evaluate the MRI appearance of the irreversible electroporation zone in porcine liver, with histopathologic correlation.


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.


CONCLUSIONS
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.
1 Department of Radiology, Ronald Reagan-UCLA Medical Center, 757 Westwood Plaza, Ste 1638, Los Angeles, CA 90095.
Ely R
ER
Felker
1 Department of Radiology, Ronald Reagan-UCLA Medical Center, 757 Westwood Plaza, Ste 1638, Los Angeles, CA 90095.
Isabel
I
Dregely
1 Department of Radiology, Ronald Reagan-UCLA Medical Center, 757 Westwood Plaza, Ste 1638, Los Angeles, CA 90095.
Dong Jin
DJ
Chung
1 Department of Radiology, Ronald Reagan-UCLA Medical Center, 757 Westwood Plaza, Ste 1638, Los Angeles, CA 90095.
Kyunghyun
K
Sung
1 Department of Radiology, Ronald Reagan-UCLA Medical Center, 757 Westwood Plaza, Ste 1638, Los Angeles, CA 90095.
Ferdnand C
FC
Osuagwu
2 Department of Pathology, David Geffen School of Medicine, Los Angeles, CA.
Charles
C
Lassman
3 Department of Biostatistics, UCLA School of Public Health, Los Angeles, CA.
James
J
Sayre
1 Department of Radiology, Ronald Reagan-UCLA Medical Center, 757 Westwood Plaza, Ste 1638, Los Angeles, CA 90095.
Holden
H
Wu
1 Department of Radiology, Ronald Reagan-UCLA Medical Center, 757 Westwood Plaza, Ste 1638, Los Angeles, CA 90095.
David S
DS
Lu
D000818:Animals; D003287:Contrast Media; D018274:Electroporation / Q000379:methods*; D019786:Gadolinium DTPA; D020287:In Situ Nick-End Labeling; D008099:Liver / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D023421:Models, Animal; D009336:Necrosis; D013552:Swine
D003287:Contrast Media; C073590:gadolinium ethoxybenzyl DTPA; D019786:Gadolinium DTPA
MRI; gadoxetate disodium; histopathology; irreversible electroporation; liver