Fast 3D UTE in vivo T1 and T∗2 mapping of fast relaxing knee tissues at 3 T

Abstract

Purpose

UTE MR imaging captures quantitative signals in fast-relaxing tissues, enabling anatomical visualization and quantitative assessment of T1 and relaxation times. However, the clinical application of quantitative UTE MRI is limited by long acquisition times. Therefore, this study introduces a novel UTE-based method for T1 and

mapping, achieving submillimeter resolution in less than 10 min. Theory and Methods

The method employs a dual-echo acquisition for fast mapping, augmented by an additional acquisition with different T1 weighting. This second scan enables the computation of signal ratios between scans with different T1-weighting. These measured signal ratios are then compared to a lookup table containing distinct ratios, corresponding to discrete T1 values. The approach was validated in phantom solutions mimicking various T1 and

times and applied in vivo to quantify relaxation times across different knee tissue compartments in healthy individuals. Results

The method demonstrated its reliability for T1 and quantification in rapidly relaxing tissues (1–11 ms). However, it exhibited a tendency to underestimate

in skeletal muscle. This limitation arises from the chosen TEs being inadequate to capture slow signal decays. In accordance with the findings of preceding studies, this in vivo study identified three distinct T1 categories of tissue characterized by short (adipose tissue), moderate (ligaments, tendons, and menisci), and long (skeletal muscle) T1 values. Conclusion

The presented technique for combined T1 and mapping enables relaxometry in rapidly relaxing tissues, indicating potential for advanced tissue characterization in clinical settings.