OFF-RESONANCE PROTON T-1-RHO DISPERSION IMAGING OF O-17-ENRICHED TISSUE PHANTOMS

Proton T-1 rho dispersion imaging is a recently described method for i ndirect detection of O-17. However, clinical implementation of this te chnique is hindered by the requirement for a high-amplitude spin-locki ng field (gamma B-1 > 1 kHz) that exceeds current limitations in speci fic absorption rate (SAR). Here, a strategy is offered for circumventi ng high SAR in T-1 rho dispersion imaging of O-17 through the use of-l ow-amplitude off-resonance spin-locking pulses (gamma B-1 < 300 Hz). P roton spin-lattice relaxation times in the off-resonance rotating fram e were measured in H-2 O-17-enriched tissue phantoms. On-and off-reson ance T-1 rho dispersion imaging was implemented at 2 T using a spin-lo cking preparatory pulse cluster appended to a standard spin-echo seque nce. On-and off-resonance dispersion images exhibited similar O-17-bas ed image contrast. Magnetization transfer effects did not depend on O- 17 concentration and had no effect on image contrast. In conclusion, o ff-resonance proton T-1 rho dispersion imaging shows promise as a safe , sensitive technique for generating O-17-based T-1 rho contrast witho ut exceeding SAR limitations.