Off-resonance proton dispersion imaging of 17ρ-enriched tissue phantoms

Abstract

Proton T(1ρ) dispersion imaging is a recently described method for indirect detection of 17O. However, clinical implementation of this technique is hindered by the requirement for a high-amplitude spin-locking field (δB1 > 1 kHz) that exceeds current limitations in specific absorption rate (SAR). Here, a strategy is offered for circumventing high SAR in Y(ip) dispersion imaging of 17O through the use of low-amplitude off-resonance spin-locking pulses (γB1 < 300 Hz). Proton spinlattice relaxation times in the off-resonance rotating frame were measured In H217O-enriched tissue phantoms. On- and off-resonance T(1ρ) dispersion imaging was implemented at 2 T using a spin-locking preparatory pulse cluster appended to a standard spin-echo sequence. On- and off-resonance dispersion images exhibited similar 17O-based image contrast. Magnetization transfer effects did not depend on 17O concentration and had no effect on image contrast. In conclusion, off- resonance proton T(1ρ) dispersion Imaging shows promise as a safe, sensitive technique for generating 17O-based T(1ρ) contrast without exceeding SAR limitations.