T '(2) mapping of the brain from water-unsuppressed H-1-MRSI and turbo spin-echo data

Purpose: To obtain high-quality T'(2) maps of brain tissues from water-unsuppressed magnetic resonance spectroscopic imaging (MRSI) and turbo spin-echo (TSE) data. Methods: T'(2) mapping can be achieved using 11 mapping from water-unsuppressed MRST data and T-2 mapping from TSE data. However, T*(2) mapping often suffers from signal dephasing and distortions caused by B-0 field inhomogeneity; T-2 measurements may be biased due to system imperfections, especially for T-2-weighted image with small number of TEs. In this work, we corrected the B-0 field inhomogeneity effect on T*(2) mapping using a subspace model-based method, incorporating pre-learned spectral basis functions of the water signals. T-2 estimation bias was corrected using a TE-adjustment method, which modeled the deviation between measured and reference T-2 decays as TE shifts. Results: In vivo experiments were performed to evaluate the performance of the proposed method. High-quality T*(2) maps were obtained in the presence of large field inhomogeneity in the prefrontal cortex. Bias in T-2 measurements obtained from TSE data was effectively reduced. Based on the T*(2) and T-2 measurements produced by the proposed method, high-quality T'(2) maps were obtained, along with neurometabolite maps, from MRSI and TSE data that were acquired in about 9 min. The results obtained from acute stroke and glioma patients demonstrated the feasibility of the proposed method in the clinical setting. Conclusions: High-quality T'(2) maps can be obtained from water-unsuppressed H-1-MRSI and TSE data using the proposed method. With further development, this method may lay a foundation for simultaneously imaging oxygenation and neurometabolic alterations of brain disorders.