Magnetic resonance angiography with gadolinium (Gd-DTPA) versus baseline magnetic resonance angiography in the study of the intracranial circulation]

The authors evaluated the role of GdDTPA in magnetic resonance angiography (MRA) of intracranial vessels. Fifteen patients affected with different conditions underwent MRA of intracranial vessels before and after paramagnetic contrast medium infusion. A superconductive 1.5-T magnet (Magnetom Siemens) was used, and a head circular coil, together with the 3DFT TOF technique. The enhanced exam was performed following the infusion of 0.2 ml/kg of GdDTPA in about 2 minutes, with simultaneous MRA image acquisition. To compare enhanced with unenhanced images relative to signal intensity, the signal increase at the basilar artery and carotid sinus was studied, together with signal-to-noise (S/N) ratio and spatial resolution. During acquisition, enhanced MRA images at the basilar artery showed a mean intensity value of 423.8 +/- 33.2 vs 357.8 +/- 53.2 of unenhanced scans; a statistically significant difference (p < 0.05; p < 0.01) was observed in favor of enhanced images. At the carotid sinus, enhanced MRA showed 184.5 +/- 28.4 mean intensity value vs 190.5 +/- 19.8 of unenhanced exams; no statistically significant difference was observed (p < 0.05; p < 0.01) in favor of unenhanced exams. At the basilar artery the S/N ratio of baseline exams was 1.9 vs 2.2 for enhanced scans; at the carotid sinus S/N ratio was 2.4 (unenhanced) vs 2.3 (enhanced). Thus, MRA allowed better visualization of peripheral branches of arterial (95.6%) and venous vessels, which unenhanced scans always failed to depict; on the other hand, enhanced images exhibited poorer definition of arterial vessels which were never isolated from the background. The simultaneous visualization of arterial and venous vessels, of choroid plexus and mucosae, affect the quality of enhanced angiograms. At present, GdDTPA is the sole contrast medium suitable for MRA intracranial vessels even though, due to its pharmacokinetic features, it is not the optimum medium.