Three-Dimensional Magnetic Resonance Angiography in the Planning of Aneurysm Surgery

Magnetic resonance angiography image guidance for the microsurgical clipping of intracranial aneurysms: a report of two cases

To describe the integration of magnetic resonance angiography (MRA) in neuronavigation procedures for microsurgery of intracranial aneurysms. MRA was combined with standard magnetic resonance image (MRI) acquisition in the image-guided planning for the microsurgical clipping of a saccular aneurysm in two patients (one 3-mm large middle cerebral artery and one 8-mm large pericallosal artery aneurysm, diagnosed by catheter angiography in both patients) using two different neurosurgical navigation systems. Conventional 3-D T1-weighted MRI with gadolinium and MRA pulse sequences were acquired in frameless stereotactic conditions the day before surgery and thereafter registered, allowing the definition a minimally invasive straight trajectory to the aneurysm neck. MRA-guided neurosurgery allowed a direct approach to the aneurysms at their proper location, reducing the invasiveness of the approach by tailoring the bone opening and reducing the duration and extension of brain retraction. The technique also avoided unnecessary dissection and exposure of the main trunks and collateral vessels. The aneurysms were successfully eradicated without complication. Integration of MRA in the planning and neuronavigation procedure for intracranial aneurysms may minimize the morbidity related to the surgical approach. This technique may be applicable more routinely using standard neuronavigation equipment.

Three-dimensional rotational angiography guidance for aneurysm surgery

Object

The aim of this study was to investigate the feasibility of integrating three-dimensional rotational angiography (3D-RA) data into a surgical navigation system and to assess its accuracy and potential clinical benefit.

Methods

The study cohort consisted of 16 patients with 16 intracranial aneurysms who had been scheduled for routine or emergency surgery. Rotational angiography data were exported using a virtual reality modeling language file format and imported into the BrainLAB VectorVision2 image-guided surgery equipment. During 3D-RA the position of the head was measured using a special headframe. The authors also determined the accuracy of 3D-RA image guidance and the clinical benefit as judged by the surgeon, including, for example, early identification of branching vessels and the aneurysm.

There was good correspondence between the 3D-RA–based navigation data and the intraoperative vascular anatomy in all cases, with a maximum error of 9° of angulation and 9° of rotation. In eight cases, the surgeon determined that the 3D-RA image guidance facilitated the surgical procedure by predicting the location of the aneurysm or the origin of a branching artery that had been covered by brain tissue and blood clots.

Conclusions

The integration of 3D-RA into surgical navigation systems is feasible, but it currently requires a new perspective-registration technique. The intraoperative 3D view provides useful information about the vascular anatomy and may improve the quality of aneurysm surgery in selected cases.

Detection of the residual lumen of intracranial aneurysms immediately after coil embolization by three-dimensional digital subtraction angiographic virtual endoscopic imaging

OBJECTIVE

Detection of a small residual lumen after coil embolization is often difficult because of the coil mass and the overlap of the cerebral arteries. The purpose of this study was to assess the usefulness of virtual endoscopic (VE) analysis of three-dimensional digital subtraction angiographic (DSA) images for evaluation of aneurysmal occlusion immediately after the procedure.

METHODS

Twenty-seven intracranial aneurysms were treated with coil embolization using a three-dimensional DSA system. Biplane and rotational DSA scanning was performed before and immediately after the procedures. VE images were obtained at a separate workstation, after transfer of the rotational images. Two-dimensional (2D) DSA images and VE images obtained after the procedure were assessed with respect to aneurysmal occlusion. Morphological outcomes and other factors, including location, size, volumetric ratio (coil volume/aneurysm volume), and residual sites, were also evaluated.

RESULTS

Seven aneurysms were evaluated as complete occlusion (CO) on both 2D DSA images and VE images. Twelve aneurysms exhibited residual lumina on both 2D DSA images and VE images. Five aneurysms were evaluated as CO on 2D DSA images and as incomplete occlusion on VE images. There were no recurrences among the aneurysms that were evaluated as CO on VE images. Two of five aneurysms that were evaluated as CO on 2D DSA images and as incomplete occlusion on VE images demonstrated regrowth in follow-up examinations. Residual sites and volumetric ratios were correlated with aneurysmal regrowth.

CONCLUSION

VE imaging can demonstrate a residual lumen more frequently than can 2D DSA imaging and is useful for evaluating aneurysmal occlusion after coil embolization.

Three-dimensional reconstructed images after rotational angiography in the evaluation of intracranial aneurysms: surgical correlation

OBJECTIVE

To evaluate the diagnostic accuracy of three-dimensional reconstructed images from rotational digital subtraction angiography in the surgical treatment of intracranial aneurysms.

METHODS

Twenty-two patients with 34 intracranial aneurysms underwent biplane angiography (40 degrees per s, 4.5 degrees per image, 8.8 frames per s). Three-dimensional (3-D) reconstructed images were obtained at a separate Advantage 3.1 workstation (General Electric, Milwaukee, WI) after the rotational images were transferred. The available visualization techniques included maximum intensity projection, shaded surface display, and virtual endoluminal view. All images were evaluated in correlation with intrasurgical visual data recorded on digital videotapes.

RESULTS

3-D reconstructed images correlated well with surgical findings. The shape of the aneurysms, their neck size, and their relationships to the parent vessels and other branches were depicted clearly, especially compared with images obtained by two-dimensional conventional digital subtraction angiography and magnetic resonance angiography.

CONCLUSION

3-D digital subtraction angiography enables the surgeon to understand the 3-D structure of lesions and is very useful in planning the surgical treatment of cerebral aneurysms.