B 1 ‐insensitive T 2 preparation for improved coronary magnetic resonance angiography at 3 T

At 3 T, the effective wavelength of the RF field is comparable to the dimension of the human body, resulting in B 1 standing wave effects and extra variations in phase. This effect is accompanied by an increase in B 0 field inhomogeneity compared to 1.5 T. This combination results in nonuniform magnetization preparation by the composite MLEV weighted T 2 preparation ( T 2 Prep) sequence used for coronary magnetic resonance angiography (MRA). A new adiabatic refocusing T 2 Prep sequence is presented in which the magnetization is tipped into the transverse plane with a hard RF pulse and refocused using a pair of adiabatic fast‐passage RF pulses. The isochromats are subsequently returned to the longitudinal axis using a hard RF pulse. Numerical simulations predict an excellent suppression of artifacts originating from B 1 inhomogeneity while achieving good contrast enhancement between coronary arteries and surrounding tissue. This was confirmed by an in vivo study, in which coronary MR angiograms were obtained without a T 2 Prep, with an MLEV weighted T 2 Prep and the proposed adiabatic T 2 Prep. Improved quantitative and qualitative coronary MRA image measurement was achieved using the adiabatic T 2 Prep at 3 T. Magn Reson Med, 2006. Published 2006 Wiley‐Liss, Inc.