Imaging and T2 relaxometry of short-T2 connective tissues in the knee using ultrashort echo-time double-echo steady-state (UTEDESS)

PurposeTo develop a radial, double-echo steady-state (DESS) sequence with ultra-short echo-time (UTE) capabilities for T-2 measurement of short-T-2 tissues along with simultaneous rapid, signal-to-noise ratio (SNR)-efficient, and high-isotropic-resolution morphological knee imaging. MethodsTHe 3D radial UTE readouts were incorporated into DESS, termed UTEDESS. Multiple-echo-time UTEDESS was used for performing T-2 relaxometry for short-T-2 tendons, ligaments, and menisci; and for Dixon water-fat imaging. In vivo T-2 estimate repeatability and SNR efficiency for UTEDESS and Cartesian DESS were compared. The impact of coil combination methods on short-T-2 measurements was evaluated by means of simulations. UTEDESS T-2 measurements were compared with T-2 measurements from Cartesian DESS, multi-echo spin-echo (MESE), and fast spin-echo (FSE). ResultsUTEDESS produced isotropic resolution images with high SNR efficiency in all short-T-2 tissues. Simulations and experiments demonstrated that sum-of-squares coil combinations overestimated short-T-2 measurements. UTEDESS measurements of meniscal T-2 were comparable to DESS, MESE, and FSE measurements while the tendon and ligament measurements were less biased than those from Cartesian DESS. Average UTEDESS T-2 repeatability variation was under 10% in all tissues. ConclusionThe T-2 measurements of short-T-2 tissues and high-resolution morphological imaging provided by UTEDESS makes it promising for studying the whole knee, both in routine clinical examinations and longitudinal studies. Magn Reson Med 78:2136-2148, 2017. (c) 2017 International Society for Magnetic Resonance in Medicine.