Possibility of aneurysmal clipping with CT angiography. Is DSA necessary in the evaluation of cerebral aneurysms?

The authors investigated whether aneurysmal clipping is feasible on the basis of information provided solely with CT angiography (CTA) and in which cases with cerebral aneurysms digital subtraction angiography (DSA) is necessary. Between January 1995 and August 1997, 42 cerebral aneurysms in 29 cases were diagnosed with CTA. During the same period, DSA was performed on 15 cases with 24 cerebral aneurysms for some reason. CTA images were obtained using a SOMATOM PLUS-S CT scanner after the high dose infusion of a non-ionic iodinated contrast medium. The three-dimensional images were reconstructed with the both surface and volume rendering methods. Seventeen patients who had 22 cerebral aneurysms underwent direct surgery. Three-dimensional reconstruction images of CTA were well corresponding to intraoperative findings. In particular, CTA images provided better information with respect to the actual shape and the growing direction of the aneurysm, anatomical relationship with parent artery, its branches and surrounding bony structures, and depiction of intramural calcification, as compared to DSA. However, CTA did not possess the resolution sufficient to detect perforators less than 1 mm in diameter. For evaluation of hemodynamics during the proximal occlusion, CTA did not suffice. From these results, exploration and direct clipping of cerebral aneurysms located on the anterior part of the circle of Willis are feasible only with referring to CTA images. In cases with large-sized aneurysms more than 14 mm in diameter, however, DSA is indispensable to hemodynamic evaluation for the potential of intraoperative temporary arterial occlusion. (author)