Two‐dimensional spatially selective spin inversion and spin‐echo refocusing with a single nuclear magnetic resonance pulse Available to Purchase

A new class of nuclear magnetic resonance (NMR) pulses that provides simultaneous spatially selective inversion of nuclear spins in two dimensions following a single pulse application is described and demonstrated. The two‐dimensional selective pulses consist of a single square‐ or amplitude‐modulated π rf pulse applied in the presence of an amplitude‐modulated magnetic field gradient that reorients through the two dimensions during the rf pulse. For example, square and Gaussian rf pulses produce sharply peaked sombrero‐, egg‐carton‐, and stalagmite‐shaped profiles of spin inversion in the xz plane when applied in the presence of a gradient that rotates or describes a figure eight in the xz plane. The theoretical profiles, computed by numerical integration of the Bloch equation, are in good agreement with experimental results obtained by incorporating the pulses into a conventional NMR imaging sequence. The pulses are directly applicable to restricted field‐of‐view high‐resolution imaging for the amelioration of aliasing signal artifacts, and when combined with one‐dimensional localized phosphorus (³¹P) chemical shift spectroscopy techniques that employ surface detection coils, should permit complete three‐dimensionally localized ³¹P NMR spectroscopy. The π pulses provide similar two‐dimensional spatial selectivity of the transverse nuclear magnetization when used for refocusing Hahn spin echoes.