title: Volumetric modulated arc-based hypofractionated stereotactic radiotherapy for the treatment of selected intracranial arteriovenous malformations: dosimetric report and early clinical experience.
abstract: OBJECTIVE
  To evaluate, with a dosimetric and clinical feasibility study, RapidArc (a volumetric modulated arc technique) for hypofractionated stereotactic radiotherapy treatment of large arteriovenous malformations (AVMs).
  
  
  METHODS
  Nine patients were subject to multimodality imaging (magnetic resonance, computed tomography, and digital subtraction angiography) to determine nidus and target volumes, as well as involved organs at risk (optical structures, inner ear, brain stem). Plans for multiple intensity-modulated arcs with a single isocenter were optimized for a fractionation of 25 Gy in 5 fractions. All plans were optimized for 6-MV photon beams. Dose-volume histograms were analyzed to assess plan quality. Delivery parameters were reported to appraise technical features of RapidArc, and pretreatment quality assurance measurements were carried out to report on quality of delivery.
  
  
  RESULTS
  Average size of AVM nidus was 26.2 cm(3), and RapidArc plans provided complete target coverage with minimal overdosage (V(100%) = 100% and V(110%) < 1%) and excellent homogeneity (<6%). Organs at risk were highly spared. The D(1%) to chiasm, eyes, lenses, optic nerves, and brainstem (mean ± SD) was 6.4 ± 8.3, 1.9 ± 3.8, 2.3 ± 2.2, 0.7 ± 0.9, 4.4 ± 7.2, 12.2 ± 9.6 Gy, respectively. Conformity index (CI(95%)) was 2.2 ± 0.1. The number of monitor units per gray was 277 ± 45, total beam-on time was 2.5 ± 0.3 min. Planning vs. delivery γ pass rate was 98.3% ± 0.9%. None of the patients developed acute toxicity. With a median follow-up of 9 months, 3 patients presented with deterioration of symptoms and were found to have postradiation changes but responded symptomatically to steroids. These patients continue to do well on follow-up. One patient developed headache and seizures, which was attributed to intracranial bleed, confirmed on imaging.
  
  
  CONCLUSIONS
  Hypofractionated stereotactic radiotherapy can be successfully delivered using the RapidArc form of volumetric arc technology for intracranial AVMs. The quality of delivery and calculated parameters are in agreement with each other and are in line with published reports for other sites.
authors.affiliation: Yashoda Super Specialty Hospital, Hyderabad, India.
authors.forename: Sai
authors.initials: S
authors.lastname: Subramanian
authors.forename: Chilukuri
authors.initials: C
authors.lastname: Srinivas
authors.forename: K
authors.initials: K
authors.lastname: Ramalingam
authors.forename: M
authors.initials: M
authors.lastname: Babaiah
authors.forename: S Thirumalai
authors.initials: ST
authors.lastname: Swamy
authors.forename: G
authors.initials: G
authors.lastname: Arun
authors.forename: M
authors.initials: M
authors.lastname: Kathirvel
authors.forename: S
authors.initials: S
authors.lastname: Ashok
authors.forename: Alessandro
authors.initials: A
authors.lastname: Clivio
authors.forename: Antonella
authors.initials: A
authors.lastname: Fogliata
authors.forename: Giorgia
authors.initials: G
authors.lastname: Nicolini
authors.forename: K Srinivasa
authors.initials: KS
authors.lastname: Rao
authors.forename: T Pratap
authors.initials: TP
authors.lastname: Reddy
authors.forename: Jotwani
authors.initials: J
authors.lastname: Amit
authors.forename: Eugenio
authors.initials: E
authors.lastname: Vanetti
authors.forename: Luca
authors.initials: L
authors.lastname: Cozzi
mesh_terms: D000328:Adult; D015901:Angiography, Digital Subtraction; D001933:Brain Stem / Q000528:radiation effects; D007758:Ear, Inner / Q000528:radiation effects; D005123:Eye / Q000528:radiation effects; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000175:diagnosis / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects; D011832:Radiation Injuries / Q000188:drug therapy / Q000517:prevention & control; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D013256:Steroids / Q000627:therapeutic use; D014057:Tomography, X-Ray Computed; D055815:Young Adult
chemical_list: D013256:Steroids