T. ScARAbino, T. Popolizio, A. STRAnieRi, A. MAggiAleTTi, A. CARRieRo, N. MAggiAleTTi, U. SAlvolini
Magnetic resonance angiography (MRA) is a well-established non-invasive technique for imaging the intra-cranial vasculature, particularly large calibre arteries and veins, and detecting changes in vessel calibre and/ or course (Figs. 5.1,5.2). It is generally performed without administration of paramagnetic contrast media.
Drawbacks with respect to conventional angiography are lower spatial and, above all, temporal resolution.
The quality of MR angiographic images has recently been improved even in lower field systems by the advent of surface or phased array coils with a higher signal/noise ratio (SNR) and shorter echo times (TE) made possible by stronger gradients, new pulse sequences with optimized SNR, and longer acquisition times (given that a fourfold increase in examination time doubles the SNR).
Fig. 5.1. Normal arterial circulation: high-definition 3D TOF image at 3.0 T (matrix 1,024X512, FOV240 mm, slice thickness 1 mm) (a); detail of the circle of Willis, especially of the posterior circle (b); also note detail of the right middle cerebral artery branches (c)
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