Multi-Modality-Imaging for Radiosurgery Planning of Arteriovenous Malformations

Abstract

For arteriovenous malformations (AVMs) radiosurgery (RS) is a well-established treatment option. The needed high precise dose application is depending on the availability of imaging data sets with superior image quality that can be superimposed using an image fusion algorithm. Digital subtraction angiography (DSA) has to be integrated because it is a mandatory tool for RS planning procedure. In 34 patients suffering from an AVM various MR data sets including T1-weighted series and TOF angiographies (time of flight) were used together with the stereotactically localized CT and DSA data sets radiosurgery planning. All available image data sets were fused onto the CT data set using an automatic image fusion algorithm, in order to define the AVM nidus very precisely. The nidus was outlined in both localized DSA projections resulting in a DSA volume. Subsequently this DSA volume of the AVM has been adapted by inclusion of all available CT and MRI informations slice by slice resulting in the final target volume. We investigate in which cases the DSA volume and the finally treated target volume of the AVM were in agreement. The used thin-slice MR data sets (1–2 mm slice width) have been precisely fused onto the stereotactically localized treatment planning CT. The finally treated target volume was compared with the DSA volume of the AVM nidus as follows: In 19 cases the final target volume was larger than the DSA volume, in 6 it was smaller and 5 it was approximately equal. The difference was significant (Wilcoxon test: difference 0.005). In 4 cases outlining the AVM was not possible without DSA. In 5 patients a two- or three-vessel DSA was needed, since there were different AVM compartments. In cases where previously a partial embolization had been undergone, the use of superimposed CT sets with, and without, contrast medium was important in order to define the completely embolized partial volumes that were not subject to treatment. The inclusion of the DSA images enabled a better identification of those arterialized veins that did not belong to the nidus. The exact 3-dimensional definition of the AVM nidus has been realized safely by integrating all available imaging modalities. The stereotactic DSA data acquisition remains a crucial tool for safe nidus definition in radiosurgery treatment planning.