Water–fat separation in spiral magnetic resonance fingerprinting for high temporal resolution tissue relaxation time quantification in muscle

Abstract

Purpose: To minimize the known biases introduced by fat in rapid T 1 and T 2 quantification in muscle using a single-run magnetic resonance fingerprinting (MRF) water-fat separation sequence. Methods: The single-run MRF acquisition uses an alternating in-phase/out-of-phase TE pattern to achieve water-fat separation based on a 2-point DIXON method.Conjugate phase reconstruction and fat deblurring were applied to correct for B 0 inhomogeneities and chemical shift blurring. Water and fat signals were matched to the on-resonance MRF dictionary. The method was first tested in a multicompartment phantom. To test whether the approach is capable of measuring small in vivo dynamic changes in relaxation times, experiments were run in 9 healthy volunteers; parameter values were compared with and without water-fat separation during muscle recovery after plantar flexion exercise. Results: Phantom results show the robustness of the water-fat resolving MRF approach to undersampling. Parameter maps in volunteers show a significant (P < .01) increase in T 1 (105 ± 94 ms) and decrease in T 2 (14 ± 6 ms) when using water-fat-separated MRF, suggesting improved parameter quantification by reducing the well-known biases introduced by fat. Exercise results showed smooth T 1 and T 2 recovery curves. Conclusion: Water-fat separation using conjugate phase reconstruction is possible within a single-run MRF scan. This technique can be used to rapidly map relaxation times in studies requiring dynamic scanning, in which the presence of fat is problematic. K E Y W O R D Sconjugate phase reconstruction, exercise, fat, magnetic resonance fingerprinting, muscle, spiral | 647 KOOLSTRA eT AL.

Multi‐parametric liver tissue characterization using MR fingerprinting: Simultaneous T1, T2, T2*, and fat fraction mapping

“…Chemical shift based approaches 18,39 usually enforce B 0 field smoothness for robust estimation and water-fat separation. Previously proposed water-fat MRF works have used these approaches 16,40,41 but mapped less parameters and required an additional (separately acquired) B 1 map.…”

Skeletal muscle magnetic resonance imaging in Pompe disease

“…Recently, the quantitative contribution of the water signal to the overall MRI has been assessed using a detailed analysis of the signal decay in multiple T2w images 27,28 . Valuable advances in MRI and imaging technology now allow for the quantitative and simultaneous mapping of fat fraction, T1, and T2 using magnetic resonance fingerprinting (MRF) 29‐31 . MRF allows quantitative acquisition in an extremely short time.…”

“…Studies performed in muscular dystrophy patients identified a change in PCr/Pi ratio with decreased PCr and increased Pi in affected muscles. Interestingly, PDEs are increased earlier in the disease process and therefore they are considered a good marker of acute muscle damage 25 31 14 31 …”

“…27,28 Valuable advances in MRI and imaging technology now allow for the quantitative and simultaneous mapping of fat fraction, T1, and T2 using magnetic resonance fingerprinting (MRF). [29][30][31] MRF allows quantitative acquisition in an extremely short time. In general, these quantitative imaging sequences allow for specific quantification of the fat present in muscles and are thus useful for natural history studies or clinical trials.…”

“…25 31 P spectroscopy has also been used to study muscle metabolism in glycogenoses, such as McArdle disease, showing decreased resting values of PCr / (PCr + Pi) and increased pH levels during exercise. 14 31 P spectroscopy has been used to study murine models of Pompe disease, and these findings are summarized later in this study (see section 7).…”