Ria Mazumder, Presenter: Nothing to Disclose

Brian Raterman, Abstract Co-Author: Nothing to Disclose

Ning Jin, Abstract Co-Author: Employee ,Siemens AG

Bradley D. Bolster PhD, Abstract Co-Author: Employee, Siemens AG Stockholder, Siemens AG

Richard D. White MD, Abstract Co-Author: Consultant, Biomedical Systems

Bradley Clymer PhD, Abstract Co-Author: Nothing to Disclose

Orlando Paul Simonetti PhD, Abstract Co-Author: Consultant, Siemens AG Consultant, General Electric Company

Arunark Kolipaka PhD, Abstract Co-Author: Support, Siemens AG

To evaluate a rapid acquisition technique to noninvasively quantitate liver stiffness using MR Elastography (MRE).

In vivo liver MRE was performed on 6 normal volunteers on a 1.5T MRI scanner (Avanto, Siemens Healthcare, Germany). The volunteers were positioned supine and feet first in the scanner. A standard gradient echo (GRE) MRE sequence (MREs) and a rapid GRE MRE sequence (MREr) were used to acquire an axial slice covering a major portion of the liver. Mechanical waves were introduced into the liver by a pneumatic driver system. MRE is a phase contrast MRI technique in which a bipolar motion encoding gradient (MEG) changing its polarity every other TR synchronized with the external vibrations is used to obtain images of tissue motion. For continuous vibrations, the TR=integer # of cycles of external vibrations (CEV). Currently, MREs uses a TR=3 CEV of 60Hz, resulting in a long breath hold time of 21s for one slice. To halve the acquisition time, we set the TR=1.5 CEV of 60Hz, do not alternate the polarity of the MEG for every other TR. The resulting MREr technique reduces the breath hold time to 11s. For both the MREs and MREr sequences, imaging parameters were set identically to TE=21.4ms; FOV=40cm; α=22o(MREs),16o(MREr); slice thickness=5mm; matrix=128x64; GRAPPA acceleration factor of 2; vibration frequency=60Hz; 4 MRE time offsets; and MEG of 16.67ms duration (60Hz) was applied to measure the through-plane tissue motion. The axial through-plane wave images for each volunteer were automatically generated on-line using a standard inversion algorithm. Stiffness maps were displayed with a confidence map to measure the mean stiffness of the liver. The mean stiffness values obtained using MREs and MREr are compared using a paired student’s t-test to test for significant differences (P<0.05) between the two acquisitions.

The mean stiffness values obtained from the entire group of all volunteers using MREs and MREr are 2.11±0.5kPa and 2.12±0.5kPa respectively.  No significant difference (P=0.83)  was found between stiffness values obtained using MREs and MREr.

We have developed a rapid liver MRE acquisition technique which reduces the scan time to half that of the standard acquisition.

MR Elastography is a useful noninvasive technique to diagnose different stages of liver fibrosis based on stiffness measurements, which can avoid the use of biopsies.

Mazumder, R, Raterman, B, Jin, N, Bolster, B, White, R, Clymer, B, Simonetti, O, Kolipaka, A, Rapid Acquisition Technique for MR Elastography of the Liver.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043588.html