Evaluation of cerebral aneurysms with MR-angiography - Our experience and a review of the literature

One of the most widely studied applications of magnetic resonance angiography is the evaluation of?cerebral aneurysms. In many cases it is possible to obtain images similar to those of digital arteriography, but technical drawbacks (low signal/noise ratio and low flow signal due to turbolence) often limit the technique so that if is not a real alternative to digital arteriography in all cases. It is commonly held that high-field MR equipment and 3D TOF acquisition methods are needed to minimize these technical limitations. in this article we compare the results of MR-angiography and digital arteriography both in our ser ies and in all the cases published to date studied with high-filed MR-equipment and 3D TOF; acquisition method (496 cases). In our department we studied 39 aneurysms (6 giant) in 30 patients. We compared MR-angiography scans (method: 3D TOE Magnetization Transfer Contrast Tilted Optimized Nonsaturating Excitation) with digital arteriography images. The studies of giant aneurysms were done with three pulse sequences: 2D TOF 30 TOF and 3D TOF post contrast medium administration (Gd-DTPA). MR-angiography and digital arteriography show similar results for lesion identification, sire and, to a lesser degree fundus orientation and adjacent vessels spasm evaluation, whereas MR images were less diagnostic in the evaluation of the aneurysm neck and the relation gf adjacent arteries. Due to its high sensitivity MR-angiography, is an important screening technique for cerebral aneurysms because it can also evaluate very small lesions (2-3 mm). Major disvantages are still the poor correlation with digital arteriography for neck evaluation (low signal of turbulent flow) and for the visualization of adjacent vessels (impossibility to obtain a progressive visualization of arterial vessels with MR angiography, that is possible instead with digital arteriography). In spite of these disadvantages in marry cases it is possible to obtain an accurate visualization of the aneurysm and for this reason MR angiography has become an important pre-surgical aid to obtain many images of the lesion in every spatial plane permitting evaluation of the aneurysm in the most helpful projection (also axial). Since evaluation of giant aneurysms is penalized by TOF methods due to slow flow into the lesion, we show that the highest flow signal is obtained with post-contrast 30 TOF pulse sequences.