title: Intensity-modulated arc therapy for pediatric posterior fossa tumors.
abstract: OBJECTIVE
  To compare intensity-modulated arc therapy (IMAT) to noncoplanar intensity-modulated radiation therapy (IMRT) in the treatment of pediatric posterior fossa tumors.
  
  
  METHODS
  Nine pediatric patients with posterior fossa tumors, mean age 9 years (range, 6-15 years), treated using IMRT were chosen for this comparative planning study because of their tumor location. Each patient's treatment was replanned to receive 54 Gy to the planning target volume (PTV) using five different methods: eight-field noncoplanar IMRT, single coplanar IMAT, double coplanar IMAT, single noncoplanar IMAT, and double noncoplanar IMAT. For each method, the dose to 95% of the PTV was held constant, and the doses to surrounding critical structures were minimized. The different plans were compared based on conformity, total linear accelerator dose monitor units, and dose to surrounding normal tissues, including the entire body, whole brain, temporal lobes, brainstem, and cochleae.
  
  
  RESULTS
  The doses to the target and critical structures for the various IMAT methods were not statistically different in comparison with the noncoplanar IMRT plan, with the following exceptions: the cochlear doses were higher and whole brain dose was lower for coplanar IMAT plans; the cochleae and temporal lobe doses were lower and conformity increased for noncoplanar IMAT plans. The advantage of the noncoplanar IMAT plan was enhanced by doubling the treatment arc.
  
  
  CONCLUSIONS
  Noncoplanar IMAT results in superior treatment plans when compared to noncoplanar IMRT for the treatment of posterior fossa tumors. IMAT should be considered alongside IMRT when treatment of this site is indicated.
authors.affiliation: Department of Radiological Sciences, St Jude Children's Research Hospital, Memphis, TN 38120, USA. chris.beltran@stjude.org
authors.forename: Chris
authors.initials: C
authors.lastname: Beltran
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gray
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Merchant
mesh_terms: D000293:Adolescent; D001921:Brain / Q000000981:diagnostic imaging / Q000528:radiation effects; D002528:Cerebellar Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D002648:Child; D003051:Cochlea / Q000000981:diagnostic imaging / Q000528:radiation effects; D006801:Humans; D015192:Infratentorial Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy; D008527:Medulloblastoma / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects; D011832:Radiation Injuries / Q000517:prevention & control; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D047368:Tumor Burden