Angiographic technique to precede gamma knife radiosurgery for intracranial arteriovenous malformations.

Stereotactic radiosurgery of small arteriovenous malformations (AVMs) and certain benign and malignant brain tumors using a gamma knife with 201 sources of cobalt-60 has been used to treat 300 patients at our institution since August 1987. This gamma knife-like earlier units developed in Stockholm, Buenos Aires, and Sheffield, England-was designed for closed-skull destruction of selected AVMs and neoplasms [1 , 2]. The site of interest must be precisely localized by means of cerebral angiography (for AVMs), CT, or MR imaging. The three-dimensional coordinates of the target are necessary data required to complete computerized dose planning. By use of imaging data, a final dose plan is formulated that includes the isodose configuration, total dose, and treatment time [3]. The postulated benefit of gamma knife radiosurgery over conventional external beam therapy is the rapid drop-off of radiation just outside the intended focus , thereby sparing the surrounding brain parenchyma potentially damaging radiation (Jungreis CA, personal communication). For precise localization of AVMs , meticulous attention to angiographic technique and patient positioning must be applied. Through initial trial and error, c> n angiographic technique has evolved at our institution that allows both excellent lesion resolution as well as stereotactic coordinate frame visualization. This technique requires changing our routine diagnostic angiographic methods.