title: Dosimetric study of current treatment options for radiotherapy in retinoblastoma.
abstract: OBJECTIVE
  To determine the best treatment technique for patients with retinoblastoma requiring radiotherapy to the whole eye.
  
  
  METHODS
  Treatment plans for 3 patients with retinoblastoma were developed using 10 radiotherapy techniques including electron beams, photon beam wedge pair (WP), photon beam three-dimensional conformal radiotherapy (3D-CRT), fixed gantry intensity-modulated radiotherapy (IMRT), photon volumetric arc therapy (VMAT), fractionated stereotactic radiotherapy, and helical tomotherapy (HT). Dose-volume analyses were carried out for each technique.
  
  
  RESULTS
  All techniques provided similar target coverage; conformity was highest for VMAT, nine-field (9F) IMRT, and HT (conformity index [CI] = 1.3) and lowest for the WP and two electron techniques (CI = 1.8). The electron techniques had the highest planning target volume dose gradient (131% of maximum dose received [D(max)]), and the CRT techniques had the lowest (103% D(max)) gradient. The volume receiving at least 20 Gy (V(20Gy)) for the ipsilateral bony orbit was lowest for the VMAT and HT techniques (56%) and highest for the CRT techniques (90%). Generally, the electron beam techniques were superior in terms of brain sparing and delivered approximately one-third of the integral dose of the photon techniques.
  
  
  CONCLUSIONS
  Inverse planned image-guided radiotherapy delivered using HT or VMAT gives better conformity index, improved orbital bone and brain sparing, and a lower integral dose than other techniques.
authors.affiliation: Department of Radiation Oncology, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Eman
authors.initials: E
authors.lastname: Eldebawy
authors.forename: William
authors.initials: W
authors.lastname: Parker
authors.forename: Wamied
authors.initials: W
authors.lastname: Abdel Rahman
authors.forename: Carolyn R
authors.initials: CR
authors.lastname: Freeman
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging / Q000528:radiation effects; D002675:Child, Preschool; D004583:Electrons / Q000627:therapeutic use; D006801:Humans; D007223:Infant; D009915:Orbit / Q000000981:diagnostic imaging / Q000528:radiation effects; D059351:Organ Sparing Treatments / Q000379:methods; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects; D017785:Photons / Q000627:therapeutic use; D011832:Radiation Injuries / Q000517:prevention & control; D011859:Radiography; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D019572:Retinal Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D012175:Retinoblastoma / Q000532:radiotherapy* / Q000601:surgery