The effect of B1 field inhomogeneity and the nonselective inversion profile on the kinetics of FAIR-based perfusion MRI.
Perfusion imaging with pulsed arterial spin labeling techniques, like flow-sensitive alternating inversion recovery (FAIR), may suffer from inflow of fresh, i.e., unlabeled, spins. Inflow of fresh spins is caused by the arrival of unlabeled spins in the image slice and can lead to underestimation of the perfusion if not taken into account. In this study it was shown that a decrease in B(1) field strength toward the edge of the transmit coil and the consequent reduction in the inversion efficiency leads to a narrowing of the arterial delivery function and a reduction in FAIR signal. Increasing the B(1) amplitude of the adiabatic inversion pulse from 2.3 to 5.7 times its minimum amplitude requirement resulted in an observed increase of 40 to 80% in the rat brain FAIR signal at inflow times longer than 0.65 s. For coils with limited dimensions and significant B(1) inhomogeneity over the perfusion labeling slab, the application of an excessively large B(1) amplitude in combination with adiabatic inversion is recommended to optimize the FAIR perfusion contrast.
Schepers
Janneke
J
Department of Experimental in Vivo NMR, Image Sciences Institute, University Medical Center Utrecht, 3584 CH Utrecht, The Netherlands. j.schepers@chem.uu.nl
van Osch
Matthias J P
MJ
Bartels
Lambertus W
LW
Heukels
Sean N
SN
Viergever
Max A
MA
Nicolay
Klaas
K
D000818:Animals; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003198:Computer Simulation; D003287:Contrast Media / Q000008:administration & dosage; D019786:Gadolinium DTPA / Q000008:administration & dosage; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D051381:Rats; D013113:Spin Labels
D003287:Contrast Media; D013113:Spin Labels; D019786:Gadolinium DTPA