Amplified magnetic resonance imaging (aMRI)

A mid-sagittal, cardiac-gated, bSSFP image of a healthy subject’s brain before and after motion-amplification post-processing is applied. Brain tissue motion induced by cardiac pulsatility is too subtle for direct visualization, but can be clearly seen using the aMRI technique. 

This work describes a new method called amplified Magnetic Resonance Imaging (aMRI), which uses Eulerian Video Magnification to amplify the subtle spatial variations in cardiac-gated brain MRI scans and enables better visualization of brain motion.

The aMRI method takes retrospective cardiac-gated cine MRI data as input, applies a spatial decomposition, followed by temporal filtering and frequency-selective amplification of the MRI cardiac-gated frames before synthesizing a motion-amplified cine data set. This approach reveals deformations of the brain parenchyma and displacements of arteries due to cardiac pulsatility, especially in the brainstem, cerebellum, and spinal cord. aMRI has the potential for widespread clinical use since it can amplify and characterize small, often barely perceptible motion and can visualize the biomechanical response of tissues using the heartbeat as an endogenous mechanical driver.

The aMRI method can also be appreciated in this video.

Holdsworth SJ, Rahimi M, Ni W, Zaharchuk G, Moseley M.  Amplified Magnetic Resonance Imaging (aMRI), Magnetic Resonance in Medicine (2016). DOI: 10.1002/mrm.26142

Online Article