Computer-generated microsurgical anatomy of the basilar artery bifurcation. Technical note

CRANIOTOMY AND CLIPPING OF INTRACRANIAL ANEURYSM IN A STEREOSCOPIC VIRTUAL REALITY ENVIRONMENT

OBJECTIVE

The release of results of International Subarachnoid Aneurysm Trial in 2003 caused a shift in the paradigm of management of ruptured intracranial aneurysms. The cases selected for microsurgical clipping nowadays are usually those patients with aneurysms that are not suitable for embolization, and are often complex and difficult. We devised an innovative application of operative planning and training for craniotomy and microsurgical clipping of intracranial aneurysms in a stereoscopic virtual reality environment.

METHODS

Patient-specific Digital Imaging and Communications in Medicine data from computed tomographic angiography of the intracranial circulation and cranium were transferred to the workstation (Dextroscope; Volume Interactions Pte. Ltd., Singapore, Singapore). An aneurysm clip database was loaded into the patient data set. Three-dimensional volume rendering was followed by data coregistration and fusion.

RESULTS

Virtual head positioning and craniotomy were carried out to simulate the microscopic visualization. Clip selection could be carried out with reference to the angle of application. This allows one to see the exposure and degree of obliteration of an aneurysm with the various angles of approach.

CONCLUSION

The virtual craniotomy and microsurgical clipping application simulated the operative environment. Its role in neurosurgical training is encouraging and should be further developed.

How to make a three-dimensional surgical illustration of cerebral vessels with a personal computer: technical note

OBJECTIVE

To introduce a method of making three-dimensional (3-D) illustrations of cerebral vessels with a personal computer.

METHODS

We generated the 3-D images from only two views of conventional angiograms (anteroposterior and lateral views) with a personal computer, two commercial software programs, and an image scanner.

RESULTS

This method was applied to 10 consecutive cases of cerebral aneurysms. 3-D images were made in a few hours, and they contributed to assessing vascular structures of an aneurysm complex.

CONCLUSION

This method is useful for discussing surgical strategies preoperatively. Our method may be used in any facility where conventional angiography, personal computers, and 3-D software are available.

Simulation of the surgical manipulation involved in clipping a basilar artery aneurysm: concepts of virtual clipping. Technical note

Despite recent advances in three-dimensional imaging based on a voxel-rendering method, these techniques do not simulate the morphological changes that occur during surgery. The authors' goal was to develop a computer-graphics model to simulate the manipulation that occurs during surgery when clipping a cerebral aneurysm. The authors developed an application program to interpolate the contours of models of an artery and an aneurysm clip. The center of displacement was determined inside the arterial model. The directions of displacement were changed to simulate saccular and broad-neck aneurysms, and the intensity of displacement was calculated by using a cosine-based formula. The morphological changes in a saccular aneurysm that may occur during clipping were calculated in x, y, and z coordinates by using sine- and cosine-based formulas. Clip movement was integrated with the aneurysm model, thus simulating the manipulation used during clipping of a cerebral aneurysm. Surgery performed to clip a basilar artery (BA) aneurysm via the transsylvian approach was simulated, in which displacement of the internal carotid artery and clipping of the BA aneurysm were necessary. The movements of an aneurysm clip and clip applicator were designed to represent those occurring when a surgeon actually manipulates a BA aneurysm. The authors have named this methodological tool "virtual clipping." Use of this tool would assist the preoperative choice of clipping style and selection of the best clip.