Challenge Numerical beam simulation techniques used in MR-guided focused ultrasound surgery (MRgFUS) for patient treatment planning rely on accurate tissue properties in order to predict the location and shape of the beam’s focus.

Current Approaches Use table value estimates of tissue properties as in vivo tissue properties cannot be measured.Figure below shows the difference in beam propagation predictions when using tissue properties reported in literature for human breast tissue (left image- lower value, right image-higher value for the reported range of tissue properties).

Approach In this paper we present an inverse parameter estimation technique that non-invasively determines patient-specific tissue acoustic properties (speed of sound and attenuation) using a pre-treatment low-level ultrasound heating pulse and MRI temperature monitoring.

Results The inverse parameter estimation technique resulted in accurate ultrasound property values (within 5 % of those obtained by the through-transmission method). Following these validation experiments, the technique was used to measure tissue acoustic properties for the first time in in-vivo experiments and measure changes in tissue acoustic properties after MRgFUS treatment.

Awards for this Work

2010-Recipient of the Young Investigator Award at the 2nd International Symposium on MR-guided Focused Ultrasound, Washington, DC, USA

2010-Recipient of the New Investigator Award at the Society of Thermal Medicine Annual Meeting in Clearwater, Florida

Published Results

U Vyas, A Payne, N Todd, DL Parker, RB Roemer, DA Christensen, “Non-invasive patient-specific acoustic property estimation for MR-guided focused ultrasound surgery”, AIP Conference Proceedings 1481, 419, 2012

Urvi Vyas, Allison Payne, Nick Todd, Dennis L. Parker, Bob Roemer, Douglas A. Christensen,” Change in attenuation coefficient with MRgFUS treatment in in-vivo rabbit thigh with MRTI derived specific absorption rate patterns”, International Society of Magnetic Resonance in Medicine, Montreal, 2011

Urvi Vyas, Allison Payne, Nick Todd, Dennis Parker, Bob Roemer and Douglas Christensen, “A new technique for measuring changes in tissue acoustic properties using MR temperature mapping”, Society for Thermal Medicine, Clearwater Beach, Florida, April, 2010.