title: Multimodality imaging to assess immediate response to irreversible electroporation in a rat liver tumor model.
abstract: OBJECTIVE
  To compare changes on ultrasonographic (US), computed tomographic (CT), and magnetic resonance (MR) images after irreversible electroporation (IRE) ablation of liver and tumor tissues in a rodent hepatoma model.
  
  
  METHODS
  Studies received approval from the institutional animal care and use committee. Forty-eight rats were used, and N1-S1 tumors were implanted in 24. Rats were divided into groups and allocated for studies with each modality. Imaging was performed in normal liver tissues and tumors before and after IRE. MR imaging was performed in one group before and after IRE after hepatic vessel ligation. US images were graded to determine echogenicity changes, CT attenuation was measured (in Hounsfield units), and MR imaging signal-to-noise ratio (SNR) was measured before and after IRE. Student t test was used to compare attenuation and SNR measurements before and after IRE (P < .05 indicated a significant difference).
  
  
  RESULTS
  IRE ablation produced greater alterations to echogenicity in normal tissues than in tumors. Attenuation in ablated liver tissues was reduced compared with that in control tissues (P < .001), while small attenuation differences between ablated (42.11 HU ± 2.11) and control (45.14 HU ± 2.64) tumors trended toward significance (P = .052). SNR in ablated normal tissues was significantly altered after IRE (T1-weighted images: pre-IRE, 145.95 ± 24.32; post-IRE, 97.80 ± 18.03; P = .004; T2-weighted images, pre-IRE, 47.37 ± 18.31; post-IRE, 90.88 ± 37.15; P = .023). In tumors, SNR differences before and after IRE were not significant. No post-IRE signal changes were observed after hepatic vessel ligation.
  
  
  CONCLUSIONS
  IRE induces rapid changes on gray-scale US, unenhanced CT, and MR images. These changes are readily visible and may assist a performing physician to delineate ablation zones from the unablated surrounding parenchyma.
authors.affiliation: From the Department of Bioengineering, University of Illinois at Chicago, Chicago, Ill (Y.Z., A.C.L.); Department of Radiology (Y.Z., S.B.W., J.R.N., Z.Z., D.L.W., D.H.K., A.L.G., F.H.M., R.A.O., A.C.L.) and Robert H. Lurie Comprehensive Cancer Center (A.C.L.), Northwestern University, 737 N Michigan Ave, Suite 1600, Chicago, IL 60611; Department of Radiology, Medical College of Wisconsin, Milwaukee, Wis (S.B.W.); and Department of Biomedical Engineering, Northwestern University, Evanston, Ill (A.C.L.).
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.forename: Sarah B
authors.initials: SB
authors.lastname: White
authors.forename: Jodi R
authors.initials: JR
authors.lastname: Nicolai
authors.forename: Zhuoli
authors.initials: Z
authors.lastname: Zhang
authors.forename: Derek L
authors.initials: DL
authors.lastname: West
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Kim
authors.forename: A Lee
authors.initials: AL
authors.lastname: Goodwin
authors.forename: Frank H
authors.initials: FH
authors.lastname: Miller
authors.forename: Reed A
authors.initials: RA
authors.lastname: Omary
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Larson
mesh_terms: D000818:Animals; D003287:Contrast Media; D004195:Disease Models, Animal; D018274:Electroporation / Q000379:methods*; D008114:Liver Neoplasms, Experimental / Q000473:pathology* / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D064847:Multimodal Imaging; D051381:Rats; D017207:Rats, Sprague-Dawley; D014057:Tomography, X-Ray Computed / Q000379:methods; D014463:Ultrasonography / Q000379:methods
chemical_list: D003287:Contrast Media