A Weighted Head Accelerator Mechanism (WHAM) for visualizing brain rheology using magnetic resonance imaging

Abstract

BackgroundA device for moving the head during MR imaging, called a Weighted Head Accelerator Mechanism (WHAM), rotates the head of a supine subject within programmable rotation limits and acceleration profiles. The WHAM can be used with custom MRI sequences to visualize the deformation and recoil of in vivo brain parenchyma with high temporal resolution, allowing element-wise calculation of strain and shear forces in the brain. Unlike previous devices, the WHAM can be configured to provide a wide range of motion and acceleration profiles. New methodThe WHAM was calibrated using a high-speed camera on a laboratory bench and in 1.5 Tesla and 3.0 Tesla MRI scanners using gel phantoms and human subjects. The MR imaging studies employed a spatial spin-saturation tagging sub-sequence, followed by serial image acquisition. In these studies, 256 images were acquired with a temporal resolution of 2.56 ms. Deformation of the brain was quantified by following the spatial tags in the images. ResultsMR imaging showed that the WHAM drove quantifiable brain motions using g forces less than those typically observed in day-to-day activities, with peak accelerations of ∼250 rad/sec2. Comparison with existing methodsThe peak pre-contact accelerations and velocities achieved by the WHAM device in this study are both higher than devices used in previous studies, while also allowing for modification of these factors. ConclusionsMR imaging performed with the WHAM provides a direct method to visualize and quantify “brain slosh” in response to rotational acceleration. Consequently, this approach might find utility in evaluating strategies to protect the brain from mild traumatic brain injury (mTBI).