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Benefit of T1 reduction for magnetic resonance coronary angiography: A numerical simulation and phantom study
Author(s) -
Johansson Lars O.,
Fischer Stefan E.,
Lorenz Christine H.
Publication year - 1999
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/(sici)1522-2586(199904)9:4<552::aid-jmri7>3.0.co;2-5
Subject(s) - imaging phantom , flip angle , signal (programming language) , magnetic resonance imaging , angiography , magnetic resonance angiography , artifact (error) , steady state (chemistry) , nuclear magnetic resonance , medicine , nuclear medicine , computer science , radiology , physics , chemistry , artificial intelligence , programming language
Contrast agents have dramatically improved magnetic resonance angiography (MRA) of the abdominal and peripheral arteries. The imaging technique for these applications is usually a steady‐state acquisition, for which the relationship between T1 in blood and the MR signal is well known. However, in electrocardiography‐triggered angiography with limited acquisition windows, this relationship is more complex. Therefore the purpose of this work is to define the relationship between the T1 in blood and the MR signal amplitude in three‐dimensional magnetic resonance coronary angiography (3D‐MRCA). Simulations were performed using equations describing the MR signal in both steady‐state and triggered acquisition schemes. Triggered acquisition schemes use flip‐angle sweeps to maintain a constant signal during the acquisition. In this study, the effect of the flip angle sweep was calculated as a function of T1. The results show that the effect of T1 shortening in contrast‐enhanced 3D‐MRCA differs substantially from that in conventional contrast‐enhanced MRA. The triggered acquisition allows unsaturated blood to enter the volume between the acquisitions and thereby gives a much higher signal at long T1s than does steady‐state acquisition. Therefore, to gain a benefit in signal amplitude with contrast agents for 3D‐MRCA using gradient‐echo sequences, the T1 in blood may have to be as low as 50 msec. In addition, when using a prepulse to null myocardium, the results indicate the need for a large difference in T1 between blood and myocardium to avoid signal loss in blood. J. Magn. Reson. Imaging 1999;9:552–556. © 1999 Wiley‐Liss, Inc.