Limitations of angiographic target localization in planning radiosurgical treatment.

Planning radiosurgical treatment for cerebral arteriovenous malformations requires accurate definition of the true tridimensional size and shape of the nidus. Over- or underestimation of these parameters may result in undue irradiation of normal brain tissue or suboptimal irradiation coverage of the malformation leading to treatment failure. Angiography is not an ideal database for radiosurgery of arteriovenous malformations. Its shortcomings include planar representation of a tridimensional volume and simultaneous visualization of feeding arteries and draining veins overlapping with the nidus and obscuring its outline. Two illustrative clinical cases of these angiographic inadequacies are presented. Stereotactic, contrast-enhanced computed tomography may provide, in selected cases, better spatial definition of the nidus and superior anatomic detail for the final design of the radiosurgical isodose distribution.