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Quantitative MR-guided transient shear wave imaging for tissue elasticity assessment

Elastography is an efficient alternative to the traditional palpation method of assessing tissue stiffness. Magnetic resonance imaging (MRI) provides a three-dimensional (3D) high-resolution view of the surrounding anatomy during interventions. Therefore, the development of MRI-based elastographic strategies is desirable for multiple clinical applications. In this work, we developed a new transient magnetic resonance elastography (t-MRE) protocol that improved visualization of transient shear wave propagation and applied this protocol to quantify tissue elasticity in vitro using tissue-mimicking phantoms. The MRE data were cross-validated with measurements acquired under ultrasound (US) guidance and mechanical testing (MT). Following a three-pulse excitation, the t-MRE protocol was applied to visualize planar shear waves propagating 2 to 30 mm away from the excitation location. Differences in shear modulus on the order of 1 kPa were reliably detected and estimates of shear elasticity by US-based elastography and MT differed by less than 7% of the MT gold standard value. Moreover, biologically-relevant inclusions were detected in tissue-mimicking phantoms and mapped in 3D by t-MRE.