Surgical strategy for cerebral aneurysms with helical scanning CT

Introduction: 3D-CT angiography (3D-CTA) is a non-invasive imaging modality for cerebral aneurysms. 3D-CTA is helpful in evaluating the configuration of the aneurysm, the surrounding vessels and the inside of the aneurysm dome. Clinical application of this technique to complicated large cerebral aneurysms, showed that anatomical details of cerebral aneurysms such as orifice of aneurysm, intraluminal thrombus, and calcification of the wall could be clearly demonstrated by 3D-CT endoscopic imaging. Using the 3D- imaging method of helical CT, virtual views of various surgical approaches can be obtained and compared preoperatively. This information was found to be very useful for determining difficult aneurysms for coil embolization or direct surgery, including complicated and broad-based aneurysms. Methods: Helical CT scanners (TOSHIBA X-vigor) are used to image intracranial vascular lesions. At present, nearly stereoscopic images at a pixel size of 0.35 x 0.35 x 0.4 mm are obtained by reconstruction under the following conditions: slice thickness, 0.8 mm; couch top speed, 1.0 mm/sec.; 130 kV; 220 mA; visual field, 18 cm in diameter (11 cm after extension) ; pitch, 0.4 mm; and opposed beam interpolation. Results and clinical application: In virtual vascular 3D- CT endoscopy, the lumen of the cerebral aneurysm is displayed by the surface rendering method. Its clinical applications include: (1) Determination of the 3D aneurysm morphology, as well as the dome and the neck region. The smallest detectable lesion was 1.5 mm. (2) Preoperative simulation. (3) Allows the confirmation of parent blood vessels flowing into aneurysms and the sites of blood vessels flowing out of aneurysms and visualization of aneurysmal lumen calcification. Coronal and sagittal sections can demonstrate whether the branches will be derived from aneurysm or aneurysmal neck. One limitation with 3D-CTA is in delineation of perforating arteries which are less than 1.2 mm in diameter. A problem with virtual vascular 3D-CT endoscopic image is that endoscopic findings in the vascular wall are incomplete because of the partial volume effect and pulsation of the aneurysm and vascular wall. Conclusions: Helical scanning CT is an excellent and non invasive diagnostic modality for cerebral aneurysm detection. 3D-CT angiography has distinct advantages for evaluating an aneurysm and for determining of the most appropriate therapeutic modality. More precise and useful images will be obtained by recently developed half-second, submillimeter, real multirow helical CT.