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Normal Brain Irradiation for Intracranial Multiple Metastasis Stereotactic Radiosurgery (SRS): Comparison Between Coplanar and Non-Coplanar Arcs

E Garrigo*, E Aon , D Franco , E falco , C Descamps , Centro Medico Dean Funes, Cordoba, X


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: In SRS multiple metastasis treatments, high plan quality and accurate dose delivery are imperative. Normal brain irraditation becomes highly significant due to patient survival rate . Non-coplanar techniques typically result in plans with improved conformity, but couch rotations may increase normal brain irradiation. The aim of this study was to compare coplanar and non-coplanar RapidArc plans with respect to plan quality and normal brain irradiation.

Methods: Five intracranial multiple metastasis SRS cases were planned using one, two and five lesions with non-coplanar RapidArc (four single arcs, couch 0°, ±45°and 90°) and coplanar RapidArc (four arcs, couch 0°). PTV plan acceptance criteria were such that at least 95% of the PTV should receive the prescribed dose (PD=27Gy) in three fractions and the maximum PTV dose (Dmax) should not exceed 150% of the PD. Organs at risk (OARs) included normal brain minus PTV, brainstem, optic nerves, chiasm, and eyes.

Results: All original coplanar and non-coplanar plans satisfied PTV and OARs plan acceptance criteria. For one, two and five metastasis respectively, PTV mean volume was 4.7cc (1.5,7.9), 7.4cc (3.4,11.6) and 13.5cc (11.4,17.2). The Normal Brain D10cc was 16.5Gy (13.0,19.7), 19.6Gy (18.2,21.7) and 23.2Gy (22.9,23.5) with coplanar treatments and 15.8Gy (12.6,19.4), 19.8Gy (18.6,21.6) and 22.8Gy (22.5,23.2) with non-coplanar treatments. MU number was 2660 (2199,3284) 2777 (2463,2977) 2889 (2778,2992) with coplanar treatments and 2234 (1898,2834), 2444 (2106,3005) 2703 (2470,2883) with non-coplanar treatments.

Conclusion: No differences between either irradiation techniques were noted in terms of normal brain preservation but it was demonstrated that the brain irradiated volume increase with PTV size. Non-coplanar treatments are time-consuming and the probability of losing track system could be a problem. On the other side, non-coplanar treatments take less MU.


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