Abstract #2386

Off-resonance and B1+ Resilience of Relaxation Along a Fictitious Field (RAFF) pulses

Roeland Christiaan Naaktgeboren¹, Chiara Coletti², Christal van de Steeg-Henzen³, and Sebastian Weingärtner²

¹Department of Imaging Physics, Delft University of Technology, Delft, Netherlands, ²Delft University of Technology, Delft, Netherlands, ³HollandPTC, Delft, Netherlands

Synopsis

Keywords: Pulse Sequence Design, Cartilage, RAFF

Spin-lock relaxation times can provide valuable markers for pathological remodelling, but their acquisition with constant amplitude spin-lock pulses is limited by SAR and sensitive to field inhomogeneities. Relaxation along a Fictitious Field (RAFF) can be used to measure spin-lock relaxation with reduced SAR burden. In this work, we evaluate the resilience of RAFF against field B₀ and B⁺₁ field inhomogeneities. Yet another RAFF (yaRAFF) pulse is introduced for fictitious field spin-locking with increased effective field strength. yaRAFF shows >5.9% reduced susceptibility for field inhomogeneities compared with RAFF in simulations and phantom measurements. In vivo images of yaRAFF in the calf show higher precision for small off-resonances, the mapping quality for large off-resonance is maintained for in phantom and in vivo T_RAFF2 times at 3T.

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