Ultrashort TE imaging with off‐resonance saturation contrast (UTE‐OSC)

Short T 2 species such as the Achilles tendon and cortical bone cannot be imaged with conventional MR sequences. They have a much broader absorption lineshape than long T 2 species, therefore they are more sensitive to an appropriately placed off‐resonance irradiation. In this work, a technique termed ultrashort TE (UTE) with off‐resonance saturation contrast (UTE‐OSC) is proposed to image short T 2 species. A high power saturation pulse was placed +1 to +2 kHz off the water peak to preferentially saturate signals from short T 2 species, leaving long T 2 water and fat signals largely unaffected. The subtraction of UTE images with and without an off‐resonance saturation pulse effectively suppresses long T 2 water and fat signals, creating high contrast for short T 2 species. The UTE‐OSC technique was validated on a phantom, and applied to bone samples and healthy volunteers on a clinical 3T scanner. High‐contrast images of the Achilles tendon and cortical bone were generated with a high contrast‐to‐noise ratio (CNR) of the order of 12 to 20 between short T 2 and long T 2 species within a total scan time of 4 to 10 min. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.