Comparison of echo-planar sequences for perfusion-weighted MRI: which is best?
We compared gradient-echo (GRE), spin-echo (SE) and stimulated-echo (STE) echo-planar imaging sequences for perfusion-weighted imaging at different field strengths. Focal cerebral ischaemia was induced by endovascular occlusion of the middle cerebral artery in eight rats. MR was performed at 4.7 T or 2.35 T. With each sequence, we acquired data sets before, during and after bolus injection of Gd-DTPA with a time resolution of 1.2 s per image. The perfusion-weighted images were assessed with regard to image quality, artefacts, signal-to-noise ratio (SNR), and signal-at-tenuation-to-noise ratio (delta SNR) of the non-ischaemic tissue. Visual assessment showed GRE-EPI images acquired at 4.7 T to suffer from distortion due to susceptibility artefacts. Artefacts were less marked with the SE and STE series. The GRE-EPI sequence gave the highest SNR and delta SNR. At 2.35 T, the SNR of the STE sequences was less than 3 and therefore did not allow construction of reliable signal-time curves. SE-EPI was best suited for perfusion-weighted imaging at high field strength thanks to its minimal distortion artefacts and high SNR. Using lower field strengths (2.35 T and less), susceptibility artefacts are reduced; GRE-EPI sequences are then best suited, because they have the highest SNR and T2* sensitivity.
Heiland
S
S
Department of Neuroradiology, University of Heidelberg Medical School, Germany.
Kreibich
W
W
Reith
W
W
Benner
T
T
Dörfler
A
A
Forsting
M
M
Sartor
K
K
D000818:Animals; D001921:Brain / Q000098:blood supply; D002545:Brain Ischemia / Q000175:diagnosis*; D003287:Contrast Media; D017352:Echo-Planar Imaging / Q000295:instrumentation*; D019786:Gadolinium DTPA; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D051381:Rats; D017208:Rats, Wistar; D012039:Regional Blood Flow / Q000502:physiology; D012680:Sensitivity and Specificity
D003287:Contrast Media; D019786:Gadolinium DTPA