Kyunghyun Sung PhD, Presenter: Nothing to Disclose

Holden H. Wu PhD, Abstract Co-Author: Nothing to Disclose

Ferdnand Chisom Osuagwu MD, Abstract Co-Author: Nothing to Disclose

Dong-Jin Chung MD, Abstract Co-Author: Nothing to Disclose

Charles R. Lassman MD, Abstract Co-Author: Nothing to Disclose

David Shin-Kuo Lu MD, Abstract Co-Author: Consultant, Covidien AG Speaker, Covidien AG Consultant, Johnson & Johnson Research Grant, Johnson & Johnson Consultant, Bayer AG Research Grant, Bayer AG Speaker, Bayer AG

To characterize T1 relaxation time of porcine liver treated with irreversible electroporation (IRE) and to optimize T1 contrast for depicting IRE ablation zones using 3T MRI.

Eight IRE ablation zones were created percutaneously under the combined ultrasound and CT guidance in two Yorkshire pigs. MR imaging was performed 50 hours after the IRE procedure using a 3.0T MRI scanner (Siemens Magnetom Trio). Pigs were immediately sacrificed after MRI for gross pathology sectioning with routine and vital histology stains. We measured T1 relaxation time in porcine liver using variable flip angle (VFA) imaging before and after injecting contrast agent (gadoxetate disodium; Gd-EOB-DTPA). Both pre- and post-contrast T1-weighted images were obtained by using a 3D RF-spoiled gradient echo sequence with multiple flip angles (2°, 5°, 10°, 15°), covering the whole liver volume (spatial resolution = 1.8X1.8X2.5 mm3). T1 maps were computed using the reference region VFA (RR-VFA) method, which compensated for transmit RF (B1+) field variation. MRI analysis was performed in OsiriX using our in-house software plug-ins. We reformatted 3D MR images to fully cover both short- and long-axis of each IRE ablation zone, and the short-axis diameter, measured by post-contrast 15° T1w MRI, was compared with the pathologically determined size. All results are presented as mean ± standard deviation.

For pre-contrast, T1 values in normal liver are 773±54ms, while T1 values in IRE zones are 998±247ms. For post-contrast, T1 values in normal liver are 285ms (20min delay) and 149ms (30min delay), while T1 values in IRE zones are 573±174ms (20min delay; n=6) and 744±41ms (30min delay; n=2). All eight IRE zones are clearly visible on both T1w MRI and T1 maps at 3T, and post-contrast 15° T1w MRI has the best T1 contrast for depicting IRE ablation zones (see Fig 1). The measured size of IRE zones is 12.5±1.1mm on pathology and 12.1±0.9mm on T1w MRI, where the average difference between two is -2.5%.  

We have investigated T1 relaxation time after IRE procedure pre- and post-contrast in porcine liver and have shown optimized T1w MRI can accurately depict IRE ablation zone size using histopathologic correlation.

IRE is a new technique for minimally invasive and non-thermal tissue ablation, and our study can be used to optimally create T1 contrast to depict IRE ablation zones.

Sung, K, Wu, H, Osuagwu, F, Chung, D, Lassman, C, Lu, D, Characterization of T1 Relaxation Time in Porcine Liver Treated with Irreversible Electroporation Using 3T MRI.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14015347.html