Invited. Application of MR in stereotactic radiosurgery

Abstract

Radiosurgery, a bladeless brain surgery without opening skull, requires higher imaging accuracy as compared to microsurgery. Accordingly, we must refine the ways we use the MR scanner and interpret the obtained images. A well tuned and regularly calibrated MR scanner provides excellent images, which allow us to define detailed intracranial structures without distortion. This enables us to obtain a reliable imaging diagnosis despite the fact that pathologic diagnosis is not available in many radiosurgical patients. Due to its three-dimensional imaging and excellence in tissue and spatial contrast, MR is important in exploring new radiosurgical indications. Large arteriovenous malformations (AVM), dural AVM of cavernous sinus and trigeminal neuralgia are some of the successful examples. By using MR, longitudinal investigation of radiosurgical effects becomes feasible. For tumors, the longitudinal studies are important in optimization of dose selection. For AVM, MR is reliable in verification of radiosurgical result. The reliability is comparable to conventional x-ray angiography. Application of MR enhances the essence of noninvasiveness of radiosurgery.

Arteriovenous Malformation Surrounding the Trigeminal Nerve-Case Report-

“…When choosing radiosurgery as therapeutic option, stereotactic planning may be difficult for lesions associated with SAH located close to the brain stem. 2,3,21) AVMs cannot be obliterated immediately after radiosurgery 23) since the mechanism of radiation-induced blood vessel obliteration is gradual occlusion of the vessels, which remain in situ. Moreover, radiosurgery may not prevent significant rebleeding after this treatment.…”

A Methodology for Validating a New Imaging Modality with Respect to a Gold Standard Imagery: Example of the Use of 3DRA and MRI for AVM Delineation

“…For these reasons, several groups have attempted to supplement conventional angiography with true 3D data for defining the vascular lesion: MRI helps to exclude vulnerable tissues, MR angiography is a fast, non invasive 3D imaging that provides information on vascular and parenchymal brain anatomy important for optimal dose planning [6,5]. 3DRA has been also used for AVM delineation with promising results [3].…”

“…Though used by several groups for AVM delineations [6,5], the clinical superiority of MRI over DSA has never been proved. These previous experimental studies concerned small patient series.…”

Effect of fiducial marker defects on stereotactic target localization in the Leksell stereotactic system

“…Usually, MR images are preferred to CT images in intracranial stereotactic procedures because they provide better anatomical resolution [8,20]. We used the Leksell MR Indicator (Elekta Instruments AB, Stockholm, Sweden) combined with the Leksell Coordinate Frame Model G (Elekta Instruments AB, Stockholm, Sweden) ( Fig.…”