MR imaging with ultrashort TE (UTE) pulse sequences: Basic principles

The background to the clinical use of ultrashort TE (UTE) pulse sequences is reviewed. Tissues are divided into those with a majority of short T-2 relaxation components and those with a minority of them. Features of the basic physics relevant to UTE imaging are described including the fact when the radiofrequency pulse duration is of the order of T-2, rotation of tissue magnetization into the transverse plane is incomplete. Consequences of the broad linewidth of short T-2 components are discussed including their partial saturation by off-resonance fat suppression pulses and multislice imaging. The basic UTE pulse sequence with its half excitation pulse and radial imaging from the center of k-space is described together with options that suppress fat and/or long T-2 components. Features of the imaging of cortical bone, tendons, ligaments, menisci and periosteum and other tissues are illustrated. (C) 2004 The College of Radiographers. Published by Elsevier Ltd. All rights reserved.