Fast localized calibration for spatial-spectral excitation without fly-back gradients

Spiral MRI requires fat suppression because fat and other off-resonant spins are blurred. For fast cardiac spiral MRI at 3T, spectral-spatial water-only excitation is often used. Standard spectral-spatial pulses apply a fly-back gradient, limiting how thin the slices can be (>4mm). Without fly-back gradients slices can be as thin as ~1.7mm, but require a phase calibration for the radiofrequency sub-pulses with inverted gradients due to system imperfections. Here we propose and test a fast (<1s), localized pre scan enabling thin-slice water only excitation. As a potential application we show spiral multi-slice coronary angiography images acquired in a single breath-hold.