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Fig 2. A, Axial source image through a surgical clip at the basilar tip demonstrates artifacts directed along the long axis of the clip as the result of the increased attenuation through that axis. B, The coronal multiplanar reconstruction image does not demonstrate many artifacts, despite the degradation of the axial source image, but the area immediately adjacent to the clip is not optimally imaged. C, With optimal threshold settings, in a 3D volume-rendered image viewed from the posterior and inferior aspect clips at the basilar tip, a small residual is evident (arrow), projecting off the left and posterior aspect of the aneurysm neck. Note that the orientation of this image is close to the projection for a Towne view routinely used for diagnostic evaluation of the posterior circulation, except that the CTA is being viewed from behind. D, Frontal "transfascial" view from catheter-based DSA demonstrates a double attenuation (arrow) that is suggestive of a residual aneurysm remnant. E, Towne view similar to the projection from the volume-rendered CTA, but now viewed from the front, demonstrates the small "dog ear" residual (arrow) on the left, measuring approximately 2 mm.
