Liat Appelbaum MD, Presenter: Nothing to Disclose

Eli Ben David, Abstract Co-Author: Nothing to Disclose

Jacob Sosna MD, Abstract Co-Author: Consultant, ActiViews Ltd Research grant, Koninklijke Philips Electronics NV

Isaac Nissenbaum BSc, Abstract Co-Author: Nothing to Disclose

S. Nahum Goldberg MD, Abstract Co-Author: Consultant, AngioDynamics, Inc, Fremont, CA Research support, AngioDynamics, Inc, Fremont, CA

To characterize post ablation ultrasound findings following irreversible electroporation (IRE) in order to determine their utility for accurately determining the ablation margins.

IRE ablation (n = 54) was performed in-vivo in 16 pig livers using two 18g electroporation electrodes of 2 cm tip exposure with 1.5 cm inter-electrode spacing and a Nanoknife generator (Angiodynamics, Fremont, CA). Energy deposition was applied at 2,250 - 3,000 V (pulse length = 50-100 μsec; pulse repetition 50-100). Ablations were performed under ultrasound guidance (HD11, Phillips), with images recorded during the ablation and at defined intervals 1 min to 2 hr post procedure. Zones of ablation were determined at gross and histopathology obtained from animals sacrificed 2 -3 hr post-IRE. Samples were paraffin embedded, H&E stained, and examined microscopically. Dimensions of ablation and ultrasound findings were compared and subject to statistical analysis.

The ablation zone appeared within 20 – 50 pulse repetitions of IRE energy as a hypoechoic oval area with well demarcated margins. Over the initial 5 – 20 min post-IRE, this zone, however, reduced in size from 3.3 ± 0.4 cm to 2.9 ± 0.4 cm (p < 0.01), became progressively more isoechoic, and hence less well depicted. Subsequently, 41 ± 19 min post-IRE (20 – 90min range), a 3.8 ± 1.2 mm peripheral hyperechoic rim (2-7 mm range) developed. The final dimensions of the outer margin of this rim provided greatest accuracy (± 2 mm) and tightest correlation (r2 = 0.70) with gross pathologic findings (2.9 ± 0.2 x 1.6 ± 0.2 x 2.4 ± 0.9cm; width, depth, height, respectively). Histology demonstrated widened sinusoidal spaces and hemorrhagic infiltrate on a bed of hepatocytes with pyknotic nuclei throughout the treatment zone.

Acute post-IRE ultrasound findings are dynamic and evolve. The ablation zone can be best predicted by measuring the external hyperechoic rim that forms 20-90 min after the ablation, possibly due to hemorrhagic infiltration via widened sinusoids.

Characterizing and understanding the ultrasound findings of IRE ablation will enable us to best determine how they can be used for procedure monitoring and follow-up.

Appelbaum, L, Ben David, E, Sosna, J, Nissenbaum, I, Goldberg, S, Ultrasound Findings Following Irreversible Electroporation Ablation: Radiologic-Pathologic Correlation  .  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9013560.html