(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: Magnetic resonance imaging (MRI) plays an important role in diagnostic imaging and quantification of pathologies. A significant push is towards the development of head-only MRI systems which can be driven harder and faster than traditional whole-body MRIs. Unfortunately, in these systems imaging is limited to the brain only. This is true due to their small imaging-region size and compact nature making patient entrance past the shoulders impractical. Therefore, in this work we present a computer simulated design study on a compact gradient coil which can be installed within a head-only MRI system allowing imaging down into the neck and below. Furthermore, experimental water-flow measurements combined with simulated heating and flow measurements were used to determine the optimal wire size for use in all hollow-wire gradients.
Methods: The boundary element method (BEM) was implemented using in-house custom-built MATLAB software. Briefly, in the BEM a target-field profile is chosen, and the current density on an input surface is solved for using a stream function value at each node. Once the stream function is solved for it is contoured giving wire-patterns which best approximate our current density. This is repeated for different potential design combinations giving a gradient coil candidate pool of tens of thousands of possible designs. The chosen gradient design is the candidate with the best balance of all performance parameters. Heating simulations were performed using in-house software solving for flow rate across a hollow conductor coupled with joule-heating simulations.
Results: The shoulder cut-out gradient design presented here provides performance on-par with current head-only MRI gradient coils while allowing the imaging region to be situated further down on the patient.
Conclusion: This work presents a potential gradient coil design which can be machined and fabricated for installation within a head-only MRI system while also presenting insight into optimal wire choices.
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