Projection presaturation. II. Single-shot localization of multiple regions of interest

Abstract Spatial localization of multidimensional regions of interest (ROIs) whose spins remain unaffected during the localization procedure is important for many applications of magnetic resonance imaging and spectroscopy. In this paper we generalize and extend our previously developed localization technique called projection presaturation based on selective spatial presaturation to localize one or more off-center ROIs. An analytical method based on the small-tip-angle approximation is presented to design the RF pulses to localize the ROIs whose shape and size can be tailored to match in vivo targets permitting spectroscopic or imaging studies to be performed from such targets under identical physiological conditions. Experimental results demonstrate the efficacy of the method. The technique is accurate even for off center localization and does not suffer from the limitations of T 2 or T 2 ∗ dephasing common to localization techniques based on selective excitation. It can be easily implemented on any existing commercial NMR scanner as it does not require any special imaging hardware. Applications of the technique to suppress aliasing and flow artifacts in NMR imaging are demonstrated. Other potential applications of the method include in vivo localized spectroscopy/ relaxometry, small field of view imaging, background signal suppression in flow and vascular imaging, and flow tagging.