Capturing fast relaxing spins with SWIFT adiabatic rotating frame spin-lattice relaxation (T) mapping

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10 Scopus citations

Abstract

Rotating frame spin-lattice relaxation, with the characteristic time constant T, 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 T2 and thus can be difficult to detect directly with conventional image acquisition techniques. Here, we introduce an approach for three-dimensional adiabatic T 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 mapping is described. Experiments on phantoms and musculoskeletal tissue specimens (tendon, articular and epiphyseal cartilages) were performed at 9.4T 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 time constant, the measured T values obtained with MP-SWIFT and FSE were similar. Conversely, in normal musculoskeletal tissues, T values measured with MP-SWIFT were much shorter than the values obtained with FSE. Studies of biological tissue specimens demonstrated that T-weighted SWIFT provides higher contrast between normal and diseased tissues relative to conventional acquisitions. Adiabatic T mapping with SWIFT readout captures contributions from the otherwise undetected fast relaxing spins, allowing more informative T measurements of normal and diseased states.

Original languageEnglish (US)
Pages (from-to)420-430
Number of pages11
JournalNMR in biomedicine
Volume29
Issue number4
DOIs
StatePublished - Apr 1 2016

Bibliographical note

Publisher Copyright:
© 2016 John Wiley & Sons, Ltd.

Keywords

  • Bound water
  • Musculoskeletal
  • Relaxometry
  • Rotating frame relaxation
  • SWIFT
  • Ultrashort T

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