METHODS
In this study, 19 patients with AVM diagnosis who underwent SRS with FFF and VMAT technique between 2014 and 2022 were evaluated. The clinical features and radiotherapy planning data of the patients were analyzed. The treatment response was evaluated with angiography/MR angiography results performed at 6, 12, and 24 months after SRS. The duration until the treatment response, side effects, and the factors affecting them were examined.

RESULTS
The median age of the patients was 33 (12-64) years. Embolization was performed before SRS in 12 patients, while seven received SRS only. Nine patients were treated with 6X-FFF and 10 with 10X-FFF energy. The median PTV was 7.30 cc (1.20?37.60). The median treatment dose was 20 Gy (15-20 Gy). Median follow-up was 20 (5-81) months. Symptoms disappeared after the treatment in twelve patients (63%) and the median time to symptom disappearance was 4.5 (1-12) months. Median follow-up was 20 (5?1) months. Complete obliteration was seen in twelve patients and median time to obliteration was 11.5 (3?31) months. Partial obliteration was achieved in five patients. Based on the radiological evaluation, the obliteration rates were 6/18 (33%), 6/14 (43%), and 8/13 (62%) at 6, 12, and 24 months, respectively. Complete obliteration was obtained in six patients who reached a 3-year follow-up period. Brain necrosis was observed in three patients (16%) at 11, 27, and 30 months.

CONCLUSION
In patients diagnosed with AVM, the treatment outcomes of SRS with LINAC-based FFF are similar to those achieved with other systems. A longer follow-up period is required for evaluating the side effects. Keywords : Arteriovenous malformation; filter-free energies; LINAC; stereotactic radiosurgery