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B 1 ‐insensitive T 2 preparation for improved coronary magnetic resonance angiography at 3 T
Author(s) -
Nezafat Reza,
Stuber Matthias,
Ouwerkerk Ronald,
Gharib Ahmed M.,
Desai Milind Y.,
Pettigrew Roderic I.
Publication year - 2006
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.20835
Subject(s) - adiabatic process , nuclear magnetic resonance , magnetization , pulse (music) , magnetic resonance imaging , pulse sequence , coronary angiography , dimension (graph theory) , coronary arteries , wavelength , magnetic resonance angiography , flip angle , materials science , phase (matter) , radio frequency , physics , magnetic field , nuclear medicine , optics , medicine , mathematics , radiology , artery , computer science , telecommunications , cardiology , myocardial infarction , quantum mechanics , detector , thermodynamics , pure mathematics
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.