title: Dosimetric comparison of different treatment modalities for stereotactic radiosurgery of arteriovenous malformations and acoustic neuromas.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  Patients with arteriovenous malformation (n = 10) or acoustic neuromas (n = 5) were planned with different treatment modalities. Paddick conformity index (CI), dose heterogeneity (DH), 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 (28.4min±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.
authors.affiliation: Department of Radiotherapy, Universitair Ziekenhuis Brussel, Brussel, Belgium. thierry.gevaert@uzbrussel.be
authors.forename: Thierry
authors.initials: T
authors.lastname: Gevaert
authors.forename: Marc
authors.initials: M
authors.lastname: Levivier
authors.forename: Thomas
authors.initials: T
authors.lastname: Lacornerie
authors.forename: Dirk
authors.initials: D
authors.lastname: Verellen
authors.forename: Benedikt
authors.initials: B
authors.lastname: Engels
authors.forename: Nick
authors.initials: N
authors.lastname: Reynaert
authors.forename: Koen
authors.initials: K
authors.lastname: Tournel
authors.forename: Michael
authors.initials: M
authors.lastname: Duchateau
authors.forename: Truus
authors.initials: T
authors.lastname: Reynders
authors.forename: Tom
authors.initials: T
authors.lastname: Depuydt
authors.forename: Christine
authors.initials: C
authors.lastname: Collen
authors.forename: Eric
authors.initials: E
authors.lastname: Lartigau
authors.forename: Mark
authors.initials: M
authors.lastname: De Ridder
mesh_terms: D001165:Arteriovenous Malformations / Q000601:surgery*; D006801:Humans; D009464:Neuroma, Acoustic / Q000601:surgery*; D016634:Radiosurgery; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted