ERI: Magnetic Resonance Imaging of Acoustic Fields for Ultrasound-Based CNS Regeneration

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Approximately 41 million people within the United States suffer disability. These disabilities place a large burden on individuals, their families, and society as a whole. Technologies that can induce neuron restoration and rehabilitation are a critical national health priority. However, restoration or rehabilitation in the central nervous system is particularly hard to accomplish because human neurons regenerate slowly or not at all and it is difficult to deliver helpful drugs through the blood brain barrier. Meanwhile, recently developing brain surgical technologies, called focused ultrasound, possess many characteristics of an ideal neural rehabilitation technology because focused ultrasound can induce changes in brain tissue at specific places and times without harming surrounding tissues and are thought to safely open the blood-brain barrier. Development of these technologies is slowed by the inability to non-destructively measure the ultrasound pressure field inside a living subject. This makes it hard to control which ultrasound-brain tissue effect one might induce during therapy. The goal of this project is to accelerate the development of ultrasound-based neural rehabilitation technology by building devices that can non-destructively measure ultrasound pressure fields in living subjects. When completed, the device will allow doctors and researchers to measure and control the ultrasound field and, thereby, the specific ultrasound-brain interaction induced during therapy.This proposal will design, prototype, and validate a novel ultrasound-encoding electromagnet that can be inserted into a magnetic resonance imaging (MRI) scanner and encode acoustic longitudinal displacement fields into MR images of living subjects. The displacement data can then be used to estimate acoustic parameters such as pressure and sound speed inside the subject. If successful, the new information provided by this electromagnet insert will enhance the scientific rigor of ongoing and future ultrasound neuromodulation therapy studies. The project will be conducted in the following three phases: 1) design, 2) prototype, and 3) validation. The design phase will use simulation software to evaluate two electromagnet designs against design criteria such as the encoding capability of the electromagnet at 2 cm distance, Lorentz forces exerted on the device, and heating during operation. During the prototyping phase, the device will be constructed and evaluated against the performance criteria predicted during the design phase. The effects of the device on MRI image quality will also be assessed. If the device meets established performance criteria, then, during the validation phase of the project, the electromagnet will be used to estimate acoustic pressure fields induced in a tissue-mimicking gel object. Upon completion of these three phases, this project will produce a novel device that can non-destructively measure acoustic pressure fields in water-based objects and can be readily applied to ultrasound-based nerve rehabilitation studies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.