Oxygen saturation-dependent effects on blood transverse relaxation at low fields

• Published in: Magma (New York, N.Y.) Vol. 35; no. 5; pp. 805 - 815
• Main Authors: Thomas, Dion G., Galvosas, Petrik, Tzeng, Yu-Chieh, Harrison, Freya G., Berry, Mary J., Teal, Paul D., Wright, Graham A., Obruchkov, Sergei
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 02.02.2022
• Subjects: Basic Science - Contrast mechanisms; Biomedical Engineering and Bioengineering; Computer Appl. in Life Sciences; Health Informatics; Imaging; Medicine; Medicine & Public Health; Radiology; Research Article; Solid State Physics; Oxygenation; Low field; Relaxometry; Blood; CPMG echo interval
• ISSN: 1352-8661; 0968-5243; 1352-8661
• DOI: 10.1007/s10334-021-00993-2

Objective Blood oxygenation can be measured using magnetic resonance using the paramagnetic effect of deoxy-haemoglobin, which decreases the T 2 relaxation time of blood. This T 2 contrast has been well characterised at the B 0 fields used in MRI (1.5 T and above). However, few studies have characterised this effect at lower magnetic fields. Here, the feasibility of blood oximetry at low field based on T 2 changes that are within a physiological relevant range is explored. This study could be used for specifying requirements for construction of a monitoring device based on low field permanent magnet systems. Methods A continuous flow circuit was used to control parameters such as oxygen saturation and temperature in a sample of blood. It flowed through a variable field magnet, where CPMG experiments were performed to measure its T 2 . In addition, the oxygen saturation was monitored by an optical sensor for comparison with the T 2 changes. Results These results show that at low B 0 fields, the change in blood T 2 due to oxygenation is small, but still detectable. The data measured at low fields are also in agreement with theoretical models for the oxy-deoxy T 2 effect. Conclusion T 2 changes in blood due to oxygenation were observed at fields as low as 0.1 T. These results suggest that low field NMR relaxometry devices around 0.3 T could be designed to detect changes in blood oxygenation.