Comparison of optimized soft-tissue suppression schemes for ultrashort echo time MRI

Abstract

Ultrashort echo time (UTE) imaging with soft-tissue suppression reveals short-T2 components (typically hundreds of microseconds to milliseconds) ordinarily not captured or obscured by long-T2 tissue signals on the order of tens of milliseconds or longer. Therefore, the technique enables visualization and quantification of short-T2 proton signals such as those in highly collagenated connective tissues. This work compares the performance of the three most commonly used long-T2 suppression UTE sequences, i.e., echo subtraction (dual-echo UTE), saturation via dual-band saturation pulses (dual-band UTE), and inversion by adiabatic inversion pulses (IR-UTE) at 3 T, via Bloch simulations and experimentally in vivo in the lower extremities of test subjects. For unbiased performance comparison, the acquisition parameters are optimized individually for each sequence to maximize short-T2 signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) between short- and long-T2 components. Results show excellent short-T2 contrast which is achieved with these optimized sequences. A combination of dual-band UTE with dual-echo UTE provides good short-T 2 SNR and CNR with less sensitivity to B1 homogeneity. IR-UTE has the lowest short-T2 SNR efficiency but provides highly uniform short-T2 contrast and is well suited for imaging short-T 2 species with relatively short T1 such as bone water. Copyright © 2011 Wiley Periodicals, Inc.