Problem:Amplified Magnetic Resonance Imaging (aMRI) was recently introduced as a new brain motion detection and visualization method. In this work we strive to improve aMRI by incorporating a phase-based motion amplification algorithm.Methods:Phase-based aMRI was developed, validate using digital phantom simulations and compared with EVM-based aMRI in healthy volunteers at 3T. Data were also acquired on a patient with Chiari I malformation, and displacement maps were produced using free form deformation (FFD) of the aMRI output.
Results:Phantom simulations showed that phase-based aMRI has a linear dependence of amplified displacement on true displacement. Amplification was independent of temporal frequency, phantom size, Rician noise, and partial volume effect, but had a slight dependence on phantom shape. Phase-based aMRI supported larger amplification factors than EVM-based aMRI, and was less sensitive to noise and artifacts. Abnormal biomechanics were seen on FFD maps of the Chiari I malformation patient.Conclusion: Phase-based aMRI can be used for quantitative analysis of minute changes in brain motion, and may reveal subtle physiological variations of the brain due to pathology. Preliminary data shows the potential of phase-based aMRI to assess abnormal biomechanics in Chiari I malformation.
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