Traveling Wave Approaches for Improved Sensitivity and Spatial Coverage in Continuous-Wave (CW) Electron Paramagnetic Resonance Imaging

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Electron paramagnetic resonance imaging (EPRI) is a low-cost and highly specific imaging technique with significant applications. In medical imaging, EPRI can be used to obtain tissue oxygenation images to identify oxygen-starved areas of tissue. Oxygen-starved areas of cancer are usually more aggressive and harder to treat, so a medical imaging tool to identify hypoxia would be highly useful. A primary advantage of EPRI relative to other medical imaging techniques is the significantly lower cost of its instrumentation. For example, in comparison to magnetic resonance imaging (MRI), EPRI can be performed without using a superconducting magnet. This drastically reduces the cost of constructing, siting, and operating EPRI systems compared to MRI systems. Unlike MRI, however, the technology for using EPRI to perform whole-body human imaging has not yet been developed. One of the primary challenges in further development of EPRI is the difficulty in performing signal excitation at the frequency ranges that are desirable for high-sensitivity imaging. This project addresses this shortcoming by developing novel instrumentations that will ultimately enable EPRI systems to be used for whole-body human imaging. The successful completion of this project has the potential for the development of a low-cost, human imaging technology. Since this technology offers imaging capabilities similar to MRI but at a small fraction of its cost it is expected to significantly reduce the cost of medical diagnostic techniques based on imaging technologies. This will likely contribute towards reducing the cost of overall healthcare services provided to the public in the U.S. and around the world. Additionally, this project has important educational impacts, which include increased participation of under-represented students in research and graduate engineering education, active involvement of undergraduate students in research, mentoring K-12 science teachers and curriculum development, and broad dissemination of research results to the public.The overall objective of this project is to develop new techniques for continuous-wave (CW) electron paramagnetic resonance imaging (EPRI) that enhance its sensitivity and move towards the development of instrumentation capable of whole-body human imaging. Specifically, we propose to develop a traveling-wave (TW) approach for continuous-wave electron-paramagnetic resonance imaging. In the TW approach, RF signal excitation is performed using traveling waves that propagate from a remote antenna or probe inside a waveguide through tissue. In comparison to the conventional reactive near field approach, uniform magnetic fields across a much larger volume can be realized using the TW approach. Therefore, the development of the continuous-wave, TW-EPRI is expected to enable both the necessary volumetric coverage and sufficiently high magnetic field strength needed to perform whole-body human imaging. To accomplish this, we will pursue four aims to develop and study novel, low-cost CW, TW-EPRI instrumentation. These include: 1) develop a CW, traveling-wave EPRI system in a parallel plate waveguide environment to demonstrate feasibility for a traveling wave EPRI system; 2) Develop phased-array transmit techniques for improved magnetic field uniformity in high-frequency (300 MHz) continuous-wave, TW-EPRI systems; 3) Integrate the imaging system and develop improved reconstruction algorithms; and 4) Develop techniques for accelerating image acquisition speed and improving the sensitivity of CW, TW-EPRI systems.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.