Volume localized shift selective13C spectroscopy using pulsed rotating frame transfer sequences with windows (PRAWN)

Abstract

Some novel techniques for volume localized, chemical shift selective 13C spectroscopy are described in this work. These techniques are based on rotating frame J cross polarization and are reported for both direct and indirect modes of 13C detection. The performance of two selective mixing sequences, viz., pulsed rotating frame transfer sequences with windows (PRAWN) and PRAWN-π has been studied systematically with different liquid and gel phantoms. Two different front-end modules are used for volume localization, viz., point resolved spectroscopy (PRESS) and localized distortionless enhancement by polarization transfer (LODEPT). It is shown experimentally that both the selective J cross polarization sequences can operate efficiently with very low radiofrequency duty cycle; further, they have considerable tolerance to Hartmann-Hahn mismatch. A simple theoretical analysis is also presented to understand J cross-polarization dynamics at low RF field amplitudes. Finally, the performance of LODEPT-PRAWN-π is demonstrated for the selective detection of saturated fat in pigeon egg in indirect detection mode. Magn Reson Med, 2011