A nonmagnetic micropositioner for displacement measurement validation in the MRI environment

OBJECTIVE: The purpose of this study was to implement a nonmagnetic micropositioner in the MRI environment to validate displacement estimates of magnetic resonance acoustic radiation force imaging (MR-ARFI). METHODS: The micropositioner consisted of a stage driven by a piezoelectric stepper motor in closed-loop operation with an optical quadrature encoder. A 100-gram agar gel phantom was prepared, and three MR-ARFI pulse sequences were used to generate displacement maps. MR-ARFI measured displacements were compared to ground truth data from the optical encoder. RESULTS: but exhibited scaling biases that may have been due to the experimental setup. CONCLUSION: The proposed instrument can potentially improve the accuracy and precision of MR-ARFI-based applications, including focused ultrasound dosimetry and mechanical biomarker imaging.