Arteriovenous Malformation Radiosurgery: Evolution of the Technique

Abstract

Object: In our department, radiosurgery as been employed for managing arteriovenous malformations (AVMs) since 1984. An original, LINAC based, isocentric, multiple converging arcs technique has been utilized for treating 642 patients until December 2002. Since January 2003, an image-guided robotic radiosurgery apparatus (the Cyberknife) has been utilized in clinical practice. A modification of the treatment planning procedure was developed in order to include angiography in target volume definition. Technique: The technique is based on image fusion between CT and 3D rotational angiography. The image fusion procedure employs a mutual information maximization algorithm, the maximization of entropy correlation coefficient, to take into account translation, rotation, linear scaling and angular deformation. Results: The new procedure allowed the employ of the Cyberknife in a series of 113 patients affected by AVMs. In large (>10 ml) and spinal AVMs, prescribed radiation dose has been delivered in 2 fractions. One patient suffered for adverse effects due to irradiation. Two bleeding occurrences have been observed so far in treated patients. In small sized (<2.5 ml) AVM (26 patients) one-year complete obliteration rate is 46%. Conclusions: In small AVMs the Cyberknife frameless radiosurgery procedure seems to afford the same good results obtained with frame-based isocentric techniques. Since, in large AVMs, target volume dose homogeneity may influence the tendency to bleed, the employ of the new radiosurgery robotic apparatus, with its highly homogeneous irradiation distribution into the target, might decrease the risk of bleeding after radiosur gery.