Agus Priatna PHD, Presenter: Research Consultant, Siemens AG

John Kotyk PhD, Abstract Co-Author: Consultant, Amgen Inc

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

Marilyn J. Siegel MD, Abstract Co-Author: Research Consultant, Siemens AG Speakers Bureau, Siemens AG

In conclusion, for the pediatric MR elastography application the optimal driver amplitude in terms of elastogram quality and patient comfort, is much smaller than in the typical adult. An amplitude range of 10%-20% results in good liver MR Elastography in the pediatric population.

MR Elastography has become clinically valuable for evaluating liver diseases such as cystic fibrosis or necrosis. MR Elastography generates images of the relative stiffness of the liver tissues by imaging the shear wave propagation generated by an external wave generator or driver. For pediatric applications, it is critical to adjust the amplitude or the strength of the wave generated by the driver for both patient comfort and size, while simultaneously providing good elastography data. In this abstract, we study the range of driver amplitudes in pediatric population that provide good elastograms while maximizing patient comfort.

MR Elastography data was acquired in 3 pediatric subjects ages 10 to 15 years old, on a 1.5T MAGNETOM Avanto (Siemens Healthcare, Erlangen, Germany), using a gradient-recalled echo based MR Elastography sequence.  The sequence was acquired in a single 20 second breath-hold. Imaging parameters were: motion encoding through slice, 256x64 acquisition matrix. A 60Hz mechanical wave was generated by the Mayo Clinic Resoundant-38A6 device. Amplitude of the driver was varied from 50% to 10% of the maximum amplitude. The applicator of the MRE device was placed at the anterior wall of the chest.

For typical adults, the amplitude applied to generate good elastogram in clinical setting usually ranges from 40-60%. For pediatric patients, we found a driver amplitude range of 10% to 20% generates sufficient wave propagation with improved patient comfort. The amplitude of 10 % provides the most patient comfort and still shows good elastrogram. In our study, we found that phase images acquired with the 10% amplitude in 10 year old patient shows less intravoxel phase dispersion (IVPD) near the chest wall than that of the amplitude 15%. Amplitudes higher than 15% resulted in increasing IVPD near the chest wall

Priatna, A, Kotyk, J, Bolster, B, Siegel, M, Adjustment of the Active Driver Amplitude for Pediatric MR Elastography of the Liver.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11008051.html