Theoretical Sensitivities of SWIFT and the Ideal Sequence (Delta Pulse-Acquire) for Ultra-Short T2

Robert Daniel O'Connell¹, Steen Moeller¹, Djaudat Idiyatullin¹, Curt Corum¹, Michael Garwood¹

A comparison is made between infinitely short RF pulses (delta), hard pulses and SWIFT using the Ernst energy equation and Bloch simulations. Simulation results are reported for each pulse sequence for on- and off-resonance systems at T1=T2. The SWIFT, delta pulse, and long T1,2 on-resonance hard-pulse sequences are described by the Ernst equations. On-resonance hard pulses have signal energy loss for short T1,2. Off-resonance hard pulses are not described by the Ernst equations. In addition to being unaffected by resonance offsets, for any flip angle the SWIFT sequence results in having a signal energy peak at shorter T1,2 than the other sequences.