Portable NMR for bedside clinical applications

Abstract

Magnetic Resonance Imaging is a powerful technique for medical diagnosis, providing clinicians and researchers with a wealth of information about the state of the body. However, conventional MRI systems are complex and expensive limiting their accessibility, particularly in rural and lower-income areas. To address this, we propose the use of single-sided NMR relaxometry systems, which measure the same contrast mechanisms used in MRI. These have lower requirements for the strength and homogeneity of the magnetic field, allowing them to be cheaper, smaller and portable.

In this thesis, a single-sided NMR system is developed for measurement in the brain. An array of permanent magnets was simulated and optimised to produce a magnetic field with a sweet spot that targets the brain. This allowed NMR signals to be excited and detected from this region, measuring the effect of relaxation and diffusion. Measurements of conventional MRI contrast mechanisms (T1, T2 and ADC) in phantoms were tested, giving results that agreed with conventional NMR/MRI systems. These benchtop experiments provided confidence in the results from the system.

Following the phantom experiments, two series of animal experiments were completed to test the feasibility of the system for monitoring or diagnosis in the brain. The first explored measuring changes in T2 during systemic hypoxia. The second series of experiments tested the system in ischemic stroke, a condition where early diagnosis and treatment is critical. Signal changes were observed in both experiments that agreed with the expected change. The results in this thesis show that single-sided NMR systems have the potential to be used for clinical application.