Dosimetric comparison of different treatment modalities for stereotactic radiosurgery of arteriovenous malformations and acoustic neuromas

Purpose: We investigated the influence of beam modulation on treatment planning by comparing four available stereotactic radiosurgery (SRS) modalities: Gamma-Knife-Perfexion, Novalis-Tx Dynamic-Conformal-Arc (DCA) and Dynamic-Multileaf-Collimation-Intensity-Modulated-radiotherapy (DMLC-IMRT), and Cyberknife. Material and methods: Patients with arteriovenous malformation (n = 10) or acoustic neuromas (n = 5) were planned with different treatment modalities. Paddick conformity index (CI), dose heterogeneity (D-H), gradient index (GI) and beam-on time were used as dosimetric indices. Results: Gamma-Knife-Perfexion can achieve high degree of conformity (CI = 0.77 +/- 0.04) with limited low-doses (GI = 2.59 +/- 0.10) surrounding the inhomogeneous dose distribution (D-H = 0.84 +/- 0.05) at the cost of treatment time (68.1 min +/- 27.5). Novalis-Tx-DCA improved this inhomogeneity (D-H = 0.30 +/- 0.03) and treatment time (16.8 min +/- 2.2) at the cost of conformity (CI = 0.66 +/- 0.04) and Novalis-TX-DMLC-IMRT improved the DCA CI (CI = 0.68 +/- 0.04) and inhomogeneity (D-H = 0.18 +/- 0.05) at the cost of low-doses (GI = 3.94 +/- 0.92) and treatment time (21.7 min +/- 3.4) (p < 0.01). Cyberknife achieved comparable conformity (CI = 0.77 +/- 0.06) at the cost of low-doses (GI = 3.48 +/- 0.47) surrounding the homogeneous (D-H = 0.22 +/- 0.02) dose distribution and treatment time (28.4 min +/- 8.1) (p < 0.01). Conclusions: Gamma-Knife-Perfexion will comply with all SRS constraints (high conformity while minimizing low-dose spread). Multiple focal entries (Gamma-Knife-Perfexion and Cyberknife) will achieve better conformity than High-Definition-MLC of Novalis-Tx at the cost of treatment time. Non-isocentric beams (Cyberknife) or IMRT-beams (Novalis-Tx-DMLC-IMRT) will spread more low-dose than multiple isocenters (Gamma-Knife-Perfexion) or dynamic arcs (Novalis-Tx-DCA). Inverse planning and modulated fluences (Novalis-Tx-DMLC-IMRT and CyberKnife) will deliver the most homogeneous treatment. Furthermore, Linac-based systems (Novalis and Cyberknife) can perform image verification at the time of treatment delivery. (C) 2012 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 106 (2013) 192-197