Capturing fast relaxing spins with SWIFT adiabatic rotating frame spin–lattice relaxation (T1ρ) mapping. (26th January 2016)

• Record Type: Journal Article
• Authors: Zhang, J.; Nissi, M.J.; Idiyatullin, D.; Michaeli, S.; Garwood, M.; Ellermann, J.
• Is Part Of: NMR in biomedicine. Volume 29:Number 4(2016:Apr.)
• Page Start: 420
• Page End: 430
• Publication Date: 2016-01-26
• Subjects: rotating frame relaxation -- bound water -- ultrashort T2 -- SWIFT -- relaxometry -- musculoskeletal; Nuclear magnetic resonance -- Periodicals; Magnetic Resonance Spectroscopy -- Periodicals; 574
• DOI: 10.1002/nbm.3474
• Languages: English
• ISSNs: 0952-3480

Abstract

Abstract : Rotating frame spin–lattice relaxation, with the characteristic time constant T 1ρ, provides a means to access motion‐restricted (slow) spin dynamics in MRI. As a result of their restricted motion, these spins are sometimes characterized by a short transverse relaxation time constant T 2 and thus can be difficult to detect directly with conventional image acquisition techniques. Here, we introduce an approach for three‐dimensional adiabatic T 1ρ mapping based on a magnetization‐prepared sweep imaging with Fourier transformation (MP‐SWIFT) sequence, which captures signal from almost all water spin populations, including the extremely fast relaxing pool. A semi‐analytical procedure for T 1ρ mapping is described. Experiments on phantoms and musculoskeletal tissue specimens (tendon, articular and epiphyseal cartilages) were performed at 9.4 T for both the MP‐SWIFT and fast spin echo (FSE) read outs. In the phantom with liquids having fast molecular tumbling and a single‐valued T 1ρ time constant, the measured T 1ρ values obtained with MP‐SWIFT and FSE were similar. Conversely, in normal musculoskeletal tissues, T 1ρ values measured with MP‐SWIFT were much shorter than the values obtained with FSE. Studies of biological tissue specimens demonstrated that T 1ρ ‐weighted SWIFT provides higher contrast between normal and diseased tissues relative to conventional acquisitions. Adiabatic T 1ρ mapping with SWIFT readout captures contributions from the otherwise undetected fast relaxing spins, allowing more informative T 1ρ measurements of normal and diseased states. Copyright © 2016 John Wiley & Sons, Ltd. Abstract : An approach for 3D adiabatic T 1ρ mapping based on a magnetization prepared Sweep Imagingwith Fourier Transformation (MP‐SWIFT) sequence which captures signal from almost all waterspin populations including the extremely fast relaxing pool was introduced. In phantom with fastmolecular tumbling and single‐valued T 1ρ time constant, the measured T 1ρ values obtained withMP‐SWIFT and FSE are similar. Conversely, in normal musculoskeletal tissues, T 1ρ valuesmeasured with MP‐SWIFT are much shorter than obtained with FSE and have increased contrastbetween normal and diseased tissues.