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Fast in vivo 23 Na imaging and mapping using accelerated 2D‐FID UTE magnetic resonance spectroscopic imaging at 3 T: Proof of concept and reliability study

2020; Wiley; Volume: 85; Issue: 4 Linguagem: Inglês

10.1002/mrm.28576

1522-2594

Ahmad A. Alhulail, Pingyu Xia, Xin Shen, Miranda Nichols, Srijyotsna Volety, Nicholas Farley, M. Albert Thomas, Armin M. Nagel, Ulrike Dydak, Uzay E. Emir,

MRI in cancer diagnosis

Purpose To implement an accelerated MR‐acquisition method allowing to map relaxation and absolute concentration of sodium within skeletal muscles at 3T. Methods A fast‐UTE‐2D density‐weighted concentric‐ring‐trajectory 23 Na‐MRSI technique was used to acquire 64 time points of FID with a spectral bandwidth of 312.5 Hz with an in‐plane resolution of 2.5 × 2.5 mm 2 in ~15 min. The fast‐relaxing 23 Na signal was localized with a single‐shot, inversion‐recovery‐based, non‐echo (SIRENE) outer volume suppression (OVS) method. The sequence was verified using simulation and phantom studies before implementing it in human calf muscles. To evaluate the 2D‐SIRENE‐MRSI (UTE = 0.55 ms) imaging performance, it was compared to a 3D‐MRI (UTE = 0.3 ms) sequence. Both data sets were acquired within 2 same‐day sessions to assess repeatability. The values were fitted voxel‐by‐voxel using a biexponential model for the 2D‐MRSI data. Finally, intra‐subject coefficients of variation (CV) were estimated. Results The MRSI‐FID data allowed us to map the fast and slow components of in the calf muscles. The spatial distributions of 23 Na concentration for both MRSI and 3D‐MRI acquisitions were significantly correlated ( P < .001). The test–retest analysis rendered high repeatability for MRSI with a CV of 5%. The mean in muscles was 0.7 ± 0.1 ms (contribution fraction = 37%), whereas was 13.2 ± 0.2 ms (63%). The mean absolute muscle 23 Na concentration calculated from the ‐corrected data was 28.6 ± 3.3 mM. Conclusion The proposed MRSI technique is a reliable technique to map sodium’s absolute concentration and within a clinically acceptable scan time at 3T.