Sodium relaxometry using 23 Na MR fingerprinting: A proof of concept

Source abstract

Purpose To evaluate the feasibility of 23 Na MR fingerprinting (MRF) for simultaneous quantification of T 1 , , , in addition to ΔB 0 . Methods A framework for sodium relaxometry using MRF at 7T was developed, allowing simultaneous measurement of relaxation times and inhomogeneities in the static field. The technique distinguishes between bi‐ and monoexponential transverse relaxation and was validated in simulations with respect to the ground truth. In phantom measurements, a resolution of 2 × 2 × 12 mm 3 was achieved within 1 h acquisition time, and the resulting parameter maps were compared to results from reference methods. Relaxation times in five healthy volunteers were measured with a resolution of 4 × 4 × 12 mm 3 . Results Phantom experiments revealed an agreement between the relaxation times obtained via 23 Na‐MRF and the reference methods. In white matter, a longitudinal relaxation constant of T 1 = 38.9 ± 4.8 ms was found, while values of = 29.2 ± 4.9 ms and = 4.7 ± 1.2 ms were found for the long and short component of the transverse relaxation. In cerebrospinal fluid, T 1 was 67.7 ± 6.3 ms and = 41.5 ± 3.4 ms. Conclusion This work demonstrates the feasibility of 23 Na‐MRF for relaxometry in sodium MRI in both phantom and in vivo studies. Simultaneous quantification of T 1 , , , and ΔB 0 was possible within a 1 h measurement time.