LONGITUDINAL DRIVER BASED MAGNETIC RESONANCE ELASTOGRAPHY
Keerthivasan, Mahesh Bharath
Magnetic Resonance Elastography (MRE) is a non-invasive imaging technique
used to determine the elastic properties of biological tissues. It can be used to
aid the diagnosis of pathologies (such as tumors and fibrosis) which result in the
variation of tissue stiffness.
In this thesis, a MR elastography system was developed for use in a clinical
setting. A pressure-based longitudinal driver was built to generate the shear waves.
An elastography pulse sequence with motion encoding gradients was designed based
on the gradient-echo and the spin-echo sequences. The pulse sequence included
the ability to switch the motion encoding along any of the three coordinate axes
depending on the direction of motion to be measured. Wave images were obtained
by acquiring phase data for different time offsets in the motion cycle. An elastogram
was computed from the phase data using the Local Frequency Estimation (LFE)
algorithm.
The validity of the method was experimentally verified using silicone and agar
gel phantoms of varying stiffnesses. The performance of the gradient-echo and
spin-echo sequences were investigated for different motion encoding gradient parameters.
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