Capturing fast relaxing spins with SWIFT adiabatic rotating frame spin-lattice relaxation (T1?) mapping.

ABSTRACT: Rotating frame spin-lattice relaxation, with the characteristic time constant T1?, 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 T1? 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 T1? 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 T1? time constant, the measured T1? values obtained with MP-SWIFT and FSE were similar. Conversely, in normal musculoskeletal tissues, T1? values measured with MP-SWIFT were much shorter than the values obtained with FSE. Studies of biological tissue specimens demonstrated that T1?-weighted SWIFT provides higher contrast between normal and diseased tissues relative to conventional acquisitions. Adiabatic T1? mapping with SWIFT readout captures contributions from the otherwise undetected fast relaxing spins, allowing more informative T1? measurements of normal and diseased states.

SUBMITTER: Zhang J 

PROVIDER: S-EPMC4805510 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature