Delineation of brain AVMs on MR-angiography for the purpose of stereotactic radiosurgery

Purpose: To assess the dosimetric consequences of brain arteriovenous malformation (bAVM) delineation on magnetic resonance angiography (MRA) for the purpose of stereotactic radiosurgery. Methods and Materials: Three observers contoured a bAVM in 20 patients, using digital subtraction angiography (V-DSA) and three-dimensional time-of-flight MRA (V-MRA). Displacement between contours was calculated. Agreement and differences between observers and imaging modalities were assessed. A standardized treatment plan with dynamic conformal arcs was generated and dosimetric coverage of all contours and the volume of normal brain tissue within the high dose region was determined. Results: The generalized reliability coefficient was "fair" for target volume (0.79), but "poor" for displacement (0.35). V-MRA was larger than V-DSA (5.0 vs. 4.0 mL, p = 0.001). No difference in displacement was found (2.8 vs. 2.5 mm, p = 0.156). Dosimetric coverage of V-MRA Was 62.9% (95% CI, 56.9-68.8) when V-DSA was used as planning target volume, and coverage of V-DSA was 83.5% (95% CI, 78.1-88.8) when V-MRA was used for planning (p < 0.001). The mean volume of normal brain within the 80% isodose was larger when the bAVM was delineated on MRA (0.7 vs. 1.0 mL (p = 0.02) for targets <= 3 mL and 3.7 vs. 7.0 mL (p = 0.01) for targets > 3 mL). Conclusions: Brain arteriovenous malformations delineated on MRA are larger and more randomly displaced. However, for bAVMs <= 3 mL, the difference in volume of normal brain tissue within the high-dose region does not seem to be clinically relevant. Therefore, MRA-images might be used as the sole imaging modality for the radiosurgical treatment of bAVMs <= 3 mL when the bAVM is located in a noneloquent position. (c) 2007 Elsevier Inc.