Designing long-T2 suppression pulses for ultrashort echo time imaging

Ultrashort echo time (UTE) imaging has shown promise as a technique for imaging tissues with T-2 values of a few milliseconds or less. These tissues, such as tendons, menisci, and cortical bone, are normally invisible in conventional magnetic resonance imaging techniques but have signal in LITE imaging. They are difficult to visualize because they are often obscured by tissues with longer T-2 values. In this article, new long-T-2 suppression RF pulses that improve the contrast of short-T-2 species are introduced. These pulses are improvements over previous long-T-2 suppression pulses that suffered from poor off-resonance characteristics or T-2, sensitivity. Short-T-2 tissue contrast can also be improved by suppressing fat in some applications. Dual-band long-T-2 suppression pulses that additionally suppress fat are also introduced. Simulations, along with phantom and in vivo experiments using 2D and 3D LITE imaging, demonstrate the feasibility, improved contrast, and improved sensitivity of these new long-T-2 suppression pulses. The resulting images show predominantly short-T-2 species, while most long-T-2 species are suppressed.