title: Critical appraisal of RapidArc radiosurgery with flattening filter free photon beams for benign brain lesions in comparison to GammaKnife: a treatment planning study.
abstract: BACKGROUND
  To evaluate the role of RapidArc (RA) for stereotactic radiosurgery (SRS) of benign brain lesions in comparison to GammaKnife (GK) based technique.
  
  
  METHODS
  Twelve patients with vestibular schwannoma (VS, n = 6) or cavernous sinus meningioma (CSM, n = 6) were planned for both SRS using volumetric modulated arc therapy (VMAT) by RA. 104 MV flattening filter free photon beams with a maximum dose rate of 2400 MU/min were selected. Data were compared against plans optimised for GK. A single dose of 12.5 Gy was prescribed. The primary objective was to assess treatment plan quality. Secondary aim was to appraise treatment efficiency.
  
  
  RESULTS
  For VS, comparing best GK vs. RA plans, homogeneity was 51.7 ± 3.5 vs. 6.4 ± 1.5%; Paddick conformity Index (PCI) resulted 0.81 ± 0.03 vs. 0.84 ± 0.04. Gradient index (PGI) was 2.7 ± 0.2 vs. 3.8 ± 0.6. Mean target dose was 17.1 ± 0.9 vs. 12.9 ± 0.1 Gy. For the brain stem, D(1cm3) was 5.1 ± 2.0 Gy vs 4.8 ± 1.6 Gy. For the ipsilateral cochlea, D(0.1cm3) was 1.7 ± 1.0 Gy vs. 1.8 ± 0.5 Gy. For CSM, homogeneity was 52.3 ± 2.4 vs. 12.4 ± 0.6; PCI: 0.86 ± 0.05 vs. 0.88 ± 0.05; PGI: 2.6 ± 0.1 vs. 3.8 ± 0.5; D(1cm3) to brain stem was 5.4 ± 2.8 Gy vs. 5.2 ± 2.8 Gy; D(0.1cm3) to ipsi-lateral optic nerve was 4.2 ± 2.1 vs. 2.1 ± 1.5 Gy; D(0.1cm3) to optic chiasm was 5.9 ± 3.1 vs. 4.5 ± 2.1 Gy. Treatment time was 53.7 ± 5.8 (64.9 ± 24.3) minutes for GK and 4.8 ± 1.3 (5.0 ± 0.7) minutes for RA for schwannomas (meningiomas).
  
  
  CONCLUSIONS
  SRS with RA and FFF beams revealed to be adequate and comparable to GK in terms of target coverage, homogeneity, organs at risk sparing with some gain in terms of treatment efficiency.
authors.forename: Ufuk
authors.initials: U
authors.lastname: Abacioglu
authors.forename: Zeynep
authors.initials: Z
authors.lastname: Ozen
authors.forename: Meltem
authors.initials: M
authors.lastname: Yilmaz
authors.forename: Alptekin
authors.initials: A
authors.lastname: Arifoglu
authors.forename: Basri
authors.initials: B
authors.lastname: Gunhan
authors.forename: Namik
authors.initials: N
authors.lastname: Kayalilar
authors.forename: Selcuk
authors.initials: S
authors.lastname: Peker
authors.forename: Meric
authors.initials: M
authors.lastname: Sengoz
authors.forename: Salih
authors.initials: S
authors.lastname: Gurdalli
authors.affiliation: Medical Physics Unit, Oncology Institute of Southern Switzerland, 6504 Bellinzona, Switzerland. lucozzi@iosi.ch.
authors.forename: Luca
authors.initials: L
authors.lastname: Cozzi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000473:pathology / Q000601:surgery*; D002426:Cavernous Sinus / Q000473:pathology / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008577:Meningeal Neoplasms / Q000473:pathology / Q000601:surgery; D008579:Meningioma / Q000473:pathology / Q000601:surgery*; D008875:Middle Aged; D009367:Neoplasm Staging; D009464:Neuroma, Acoustic / Q000473:pathology / Q000601:surgery; D058958:Organs at Risk; D017785:Photons; D011379:Prognosis; D016634:Radiosurgery; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D055815:Young Adult