Gamma knife radiosurgery of intracranial arteriovenous malformations using only magnetic resonance imaging for target delineation

Keywords: arteriovenous malformation, technique, gamma knife, outcome, magnetic resonance imaging

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     Cerebral angiography is an invasive procedure associated with risks and complications, especially for patients who have to undergo it more than once as in the case of AVMs (for diagnosis, possible embolization, pre-radiosurgery for targeting delineation, post-radiosurgery to confirm occlusion and possibly may need to repeat all or some of the previous steps in case of incomplete obliteration or for staged radiosurgical treatment). 
     In this study, we aimed to assess whether AVMs could be treated safely and efficiently utilizing only MR imaging for target delineation during gamma knife radiosurgery, without the need for performing stereotactic angiography.
     Between November 2001 and November 2008, gamma knife radiosurgery was performed on 243 consecutive patients with intracranial AVMs.
     All patients in the study had undergone pretreatment angiography. On treatment day AVM delineation was done on the stereotactic MRI scans with preoperative angiography images at hand. One hundred and thirty seven patients were available for follow up. The follow up duration was 8-99 months (mean 34 months). The AVM volume ranged from 0.2 cc to 14 cc (mean 3.7±2.9 cc). The prescription dose given was 16-35 Gy (mean 24±3 Gy).
     Of the 137 patients with documented follow up, 84 underwent angiographic evaluation. In this group, 74 patients (88%) showed complete angiographic obliteration of their AVMs. Residual nidus was demonstrated angiographically in 10 patients. From these six patients underwent retreatment. Twenty patients (15%) either developed new neurological deficit or experienced worsening of pre-existing deficit. This was due to the development of perinidal edema in all cases. In only 2 cases was the deficit permanent (0.01%), while it was temporary in the remaining cases.
     This was a retrospective study.
     This is the largest report using frame-based MRI as the sole imaging modality for AVM target delineation in gamma knife radiosurgery. 
     MRI directed AVM radiosurgery appears to be safe and efficient.


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