Abstract
Background SASHA and MOLLI T1 mapping sequences can have errors in calculated T1 values when their magnetization preparation pulses do not fully saturate/invert magnetization [1,2]. The commonly used 90°-90°-90° saturation pulse train [3] has poor performance at 3T due to large B1 field inhomogeneities. We propose that a new hard RF pulse train with numerically optimized flip angles [4] will offer superior performance and reduce errors in SASHA T1 values due to incomplete saturation.
Highlights
SASHA and MOLLI T1 mapping sequences can have errors in calculated T1 values when their magnetization preparation pulses do not fully saturate/invert magnetization [1,2]
Flip angles for a 6-pulse train were optimized by minimizing the maximum residual longitudinal magnetization in Bloch equation simulations performed over ranges of values expected at 3T: 40-120% B1 scaling, -240-240 Hz off-resonance, 200-2000 ms T1, and 14 μT B1 strength
A magnetic field gradient was used to produce a range of off-resonance and experiments were repeated with the prescribed pulse train flip angles scaled by 40-120% to emulate B1 inhomogeneity
Summary
SASHA and MOLLI T1 mapping sequences can have errors in calculated T1 values when their magnetization preparation pulses do not fully saturate/invert magnetization [1,2]. The commonly used 90°-90°-90° saturation pulse train [3] has poor performance at 3T due to large B1 field inhomogeneities. We propose that a new hard RF pulse train with numerically optimized flip angles [4] will offer superior performance and reduce errors in SASHA T1 values due to incomplete saturation
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