Single-Sided Magnet System for Quantitative MR Relaxometry and Preclinical In-Vivo Monitoring

• Published in: IEEE transactions on biomedical engineering Vol. 70; no. 2; pp. 671 - 680
• Main Authors: Thomas, Dion G., Tzeng, Yu-Chieh, Galvosas, Petrik, Harrison, Freya G., Berry, Mary J., Teal, Paul D., Galvin, Sean D., Obruchkov, Sergei I.
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.02.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Animals; Biomedical measurement; Brain; Diffusion coefficient; Diffusion Magnetic Resonance Imaging - methods; Field strength; Homogeneity; Humans; Hypoxia; Hypoxia, Brain; Magnetic field measurement; Magnetic fields; Magnetic heads; Magnetic induction; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Magnetic Resonance Spectroscopy - methods; Magnets; Medical imaging; Monitoring; Neuroimaging; NMR; Nuclear magnetic resonance; Parameters; Permanent magnets; relaxometry; Sheep; single-sided NMR; tissue oxygenation
• ISSN: 0018-9294; 1558-2531
• DOI: 10.1109/TBME.2022.3200626

Objective: We have developed a single-sided magnet system that allows Magnetic Resonance relaxation and diffusion parameters to be measured. Methods: A single-sided magnet system has been developed, using an array of permanent magnets. The magnet positions are optimised to produce a B 0 magnetic field with a spot that is relatively homogenous and can project into a sample. NMR relaxometry experiments are used to measure quantitative parameters such as T 2 , T 1 and apparent diffusion coefficient (ADC) on samples on the benchtop. To explore preclinical application, we test whether it can detect changes during acute global cerebral hypoxia in an ovine model. Results: The magnet produces a 0.2 T field projected into the sample. Measurements of benchtop samples show that it can measure T 1 , T 2 and ADC, producing trends and values that are in line with literature measurements. In-vivo studies show a decrease in T 2 during cerebral hypoxia that recovers following normoxia. Conclusion: The single-sided MR system has the potential to allow non-invasive measurements of the brain. We also demonstrate that it can operate in a pre-clinical environment, allowing T 2 to be monitored during brain tissue hypoxia. Significance: MRI is a powerful technique for non-invasive diagnosis in the brain, but its application has been limited by the requirements for magnetic field strength and homogeneity that imaging methods have. The technology described in this study provides a portable alternative to acquiring clinically significant MR parameters without the need for traditional imaging equipment.