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Plan Quality Comparison of Brain Metastasis Treated On Gamma Knife Perfexion and Volumetric Modulated Arc Therapy

M Adili

M Adili*, B Muhammad , A Alhamad , S Bamajboor , A Zaila , Prince Sultan Medical Military City, Riyadh, Saudi Arabia


SU-I-GPD-T-610 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To compare plan quality for brain metastatic lesions treated on Gamma Knife Perfexion (GK) with Volumetric Modulated Arc Therapy (VMAT) planned on a non-radiosurgery linear accelerator

Methods: 5 patients with a single and multiple brain metastatic lesions, planned and treated on GK, were re-planned on Eclipse with a single isocenter, 5 to 6 non-coplaner partial arcs using VMAT technique on 2100CD Varian linear accelerator which equipped with Millennium 120 MLC, and maximum doserate of 600MU/min. The size of the target ranges from 0.1 cc to 5.9 cc, and the prescribed dose ranges from 18 to 22Gy. Plans were normalized so that 99% - 100% of the target volume receive 100% of the prescribed dose. Parameters used to analyze the plans were: conformity index (CI) (100% isodose volume/Target volume), gradient index (GI) (50% isodose volume/100% isodose volume), 12, 9 and 3Gy isodose volume (V12, V9 and V3), and beam on time

Results: The VMAT plans showed a lower CI than the GK (1.27 ± 0.16 vs 1.43 ± 0.24), but it has a higher GI (4.81 ± 1.84 vs 2.78 ±0.25). The V12 and V9 were comparable between the two modalities. For the low dose region, GK showed a smaller volume (V3=105 cc vs 179 cc), it has been noticed that low dose region depends on the position and numbers of the treated lesions. The mean beam on time for VMAT was 14 min while for GK at the time of treatment was 115 min

Conclusion: For the range of target volumes used in this comparison, VMAT technique for multiple brain metastasis planned on a non-radiosurgery linear accelerator showed an equivalent plan quality to GK, so it could be an optional treatment modality, bearing in mind the quality of the linear accelerator in terms of accuracy and precision

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