Treatment planning for brain AVM radiosurgery procedures: current imaging modalities

Historically, angiography was one of the first diagnostic methods to allow for visualization of neurovascular structures. It has been and still is ver y useful for precise evaluation of vascular pathology and is one of the mai n elements in treatment planning for radiosurgical targets. rt is tile only imaging method that gives insight into the angioarchitecture of a cerebral arteriovenous malformation, possibly reducing the target volume. Construct ion of frames (Leksell, Fisher) that are compatible with cross-sectional im aging methods, such as CT and MRI allowed there use for planning of stereot actical treatment for brain cerebral arteriovenous malformations. The advan tages of these methods are given by the fact, that they are less invasive a nd that they allow visualization of neurovascular structures and surroundin g cerebral structures. Further evolution of the cross-sectional imaging tec hniques allowed reconstruction of the image data in different planes and se gmentation of structure es such as vessels. Use of special algorithms allow visualization of the image data, i.e. surface rendering with 3D images of vascular structures However, such images allow no detailed insight into the angioarchitecture of a cerebral arteriovenous malformation and give rather a view of the whole volume, i.e. a "tumor" aspect of the cerebral arteriov enous malformation. Similar images are currently also obtained with digital substraction angiography using rotational image acquisitions and image pos tprocessing allowing 3D reconstruction of angiographical image data. The different image evaluation methods are thus complementary all giving us eful information for treatment planning Therefore it would be useful to dev elop the possibility to integrate the information obtained by these modalit ies. Image fusion require identification of fiducial marks, went can be per formed with application of external marks or by using internal anatomical m arks. Recent developments allow now use of vascular structure es as fidiuci al marks to obtain image fusion. This paper reports on the evolution of ste reotactical planning performed on 541 patients over a period of eight years .