title: Optimal normal tissue sparing in craniospinal axis irradiation using IMRT with daily intrafractionally modulated junction(s).
abstract: OBJECTIVE
  To develop a treatment technique for craniospinal irradiation using intensity-modulated radiotherapy (IMRT) with improved dose homogeneity at the field junction(s), increased target volume conformity, and minimized dose to the organs at risk (OARs).
  
  
  METHODS
  Five patients with high-risk medulloblastoma underwent CT simulation in supine position. For each patient, an IMRT plan with daily intrafractionally modulated junction(s) was generated, as well as a treatment plan based on conventional three-dimensional planning (3DCRT). A dose of 39.6 Gy in 22 daily fractions of 1.8 Gy was prescribed. Dose-volume parameters for target volumes and OARs were compared for the two techniques.
  
  
  RESULTS
  The maximum dose with IMRT was <107% in all patients. V<95 and V>107 were <1 cm3 for IMRT compared with 3-9 cm3 for the craniospinal and 26-43 cm3 for the spinal-spinal junction with 3DCRT. These observations corresponded with a lower homogeneity index and a higher conformity index for the spinal planning target volume with IMRT. IMRT provided considerable sparing of acute and late reacting tissues. V75 for the esophagus, gastroesophageal junction, and intestine was 81%, 81%, and 22% with 3DCRT versus 5%, 0%, and 1% with IMRT, respectively. V75 for the heart and thyroid was 42% and 32% vs. 0% with IMRT.
  
  
  CONCLUSIONS
  IMRT with daily intrafractionally modulated junction results in a superior target coverage and junction homogeneity compared with 3DCRT. A significant dose reduction can be obtained for acute as well as late-reacting tissues.
authors.affiliation: Department of Radiation Oncology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Johannes M A M
authors.initials: JM
authors.lastname: Kusters
authors.forename: Rob J W
authors.initials: RJ
authors.lastname: Louwe
authors.forename: Peter G M
authors.initials: PG
authors.lastname: van Kollenburg
authors.forename: Martina C
authors.initials: MC
authors.lastname: Kunze-Busch
authors.forename: Corrie E M
authors.initials: CE
authors.lastname: Gidding
authors.forename: Erik J
authors.initials: EJ
authors.lastname: van Lindert
authors.forename: Johannes H A M
authors.initials: JH
authors.lastname: Kaanders
authors.forename: Geert O R J
authors.initials: GO
authors.lastname: Janssens
mesh_terms: D000293:Adolescent; D001269:Atlanto-Occipital Joint / Q000528:radiation effects; D002528:Cerebellar Neoplasms / Q000532:radiotherapy*; D002648:Child; D002675:Child, Preschool; D016371:Cranial Irradiation / Q000379:methods*; D019583:Dose Fractionation, Radiation; D004943:Esophagogastric Junction / Q000528:radiation effects; D004947:Esophagus / Q000528:radiation effects; D006321:Heart / Q000528:radiation effects; D006801:Humans; D007422:Intestines / Q000528:radiation effects; D008527:Medulloblastoma / Q000532:radiotherapy*; D058958:Organs at Risk / Q000528:radiation effects*; D011832:Radiation Injuries / Q000517:prevention & control*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D013131:Spine / Q000528:radiation effects*; D013270:Stomach / Q000528:radiation effects; D013961:Thyroid Gland / Q000528:radiation effects; D055815:Young Adult