Ultra-low-field R1 mapping at 0.2 mT obtained by field-cycling imaging correlates with cerebral small vessel disease burden.

OBJECTIVES: Field-cycling imaging (FCI) provides access to a unique regime of molecular dynamics across multiple ultra-low magnetic field strengths below 0.2 Tesla. This first proof-of-concept study aimed to determine whether ultra-low-field R1 mapping obtained using FCI is sensitive to the presence and burden of cerebral small vessel disease. MATERIALS AND METHODS: FCI was performed on 39 participants at field strengths of 0.2, 2, 20 and 200 mTesla, acquiring a single image slice. Sensitivity and specificity to discriminate the presence or absence of moderate or severe SVD by 1) two independent rater examinations of R1 maps, 2) R1 histogram features, and 3) deep learning classification were examined. RESULTS: Radiological review of co-registered 3 T MRI FLAIR volumes resulted in a final split cohort of 16:21 participants between a disease group and control group identified with and without moderate or severe WMHs, respectively. From FCI, the two groups were discriminated by Rater 1, Rater 2, best histogram feature, and best deep learning classification with sensitivity and specificity values of (0.81; 0.86), (0.88; 0.52), (0.94; 0.90), and (0.67; 1.00), respectively. DISCUSSION: Quantitative ultra-low multi-field R1 mapping performed using FCI has diagnostic potential to detect brain tissue changes arising from cerebral small vessel disease.