gms | German Medical Science

High-resolution three-dimensional (3D) images delivered in real-time have only recently been added to neurosurgical image guidance. This study has been conducted in order to determine clinical applications and limitations.

Two hundred and eighty neurosurgical patients participated in this clinical investigation. Pathologies included various supra- and infratentorial lesions, tumors of the skull base, and lesions of the superior cervical region. The infrared navigation system employed was based on software that is capable of reconstructing volume-rendered, freely rotating, real-time images from 3D MRI or CT data sets (Image Guidance Laboratories, Stanford, CA). Opacity modulation of surfaces, fly-through video mode, and microscopic image injection were used in almost all cases.

Volumetric rendering of 3D images was accomplished within ten to fifteen minutes including image registration for navigation. Individual anatomy was visualized in 3D images up to a resolution of 2mm for well delineated structures. Smaller and less discernable structures, such as the cranial nerves were not readily rendered. As compared to mental reconstruction of tri-axial 2D images, 3D imaging was superior for fast orientation in complex morphology (gyri, sulci, sinuses, Circle of Willis), especially in cases where rotation of the operative field of view was necessary during the approach. Virtual and real microscopic individual anatomy could permanently be correlated during surgery and for planning (déjà vue) with the advantage of integrating invisible features like functional properties, hidden structures and landmarks in the virtual 3D image.

Image-guidance on the basis of three-dimensional images cannot replace anatomical knowledge and experience. Moreover, even with the most advanced systems, depiction of anatomical detail is limited by image resolution and tissue contrast. With respect to the individual patient anatomy, 3D image guidance offers the advantage of a true déjà vue experience for the surgeon. It relieves him of the task of having to mentally reconstruct and rotate tri-axial 2D images and provides additional information on the operative field that is otherwise invisible and inaccessible.