title: Room scatter effects in Total Skin Electron Irradiation: Monte Carlo simulation study.
abstract: OBJECTIVE
  Total Skin Electron Irradiation (TSEI) is a complex technique which usually involves the use of large electron fields and the dual-field approach. In this situation, many electrons scattered from the treatment room floor are produced. However, no investigations of the effect of scattered electrons in TSEI treatments have been reported. The purpose of this work was to study the contribution of floor scattered electrons to skin dose during TSEI treatment using Monte Carlo (MC) simulations.
  
  
  METHODS
  All MC simulations were performed with the EGSnrc code. Influence of beam energy, dual-field angle, and floor material on the contribution of floor scatter was investigated. Spectrum of the scattered electrons was calculated. Measurements of dose profile were performed in order to verify MC calculations.
  
  
  RESULTS
  Floor scatter dependency on the floor material was observed (at 20 cm from the floor, scatter contribution was about 21%, 18%, 15%, and 12% for iron, concrete, PVC, and water, respectively). Although total dose profiles exhibited slight variation as functions of beam energy and dual-field angle, no dependence of the floor scatter contribution on the beam energy or dual-field angle was found. The spectrum of the scattered electrons was almost uniform between a few hundred KeV to 4 MeV, and then decreased linearly to 6 MeV.
  
  
  CONCLUSIONS
  For the TSEI technique, dose contribution due to the electrons scattered from the room floor may be clinically significant and should be taken into account during design and commissioning phases. MC calculations can be used for this task.
authors.affiliation: Division of Oncology, Rambam Health Care Campus, Haifa, Israel.
authors.forename: Alexander
authors.initials: A
authors.lastname: Nevelsky
authors.affiliation: Division of Oncology, Rambam Health Care Campus, Haifa, Israel.
authors.forename: Egor
authors.initials: E
authors.lastname: Borzov
authors.affiliation: Division of Oncology, Rambam Health Care Campus, Haifa, Israel.
authors.forename: Shahar
authors.initials: S
authors.lastname: Daniel
authors.affiliation: Division of Oncology, Rambam Health Care Campus, Haifa, Israel.
authors.forename: Raquel
authors.initials: R
authors.lastname: Bar-Deroma
mesh_terms: D003198:Computer Simulation; D004583:Electrons; D006801:Humans; D009010:Monte Carlo Method; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012542:Scattering, Radiation; D012867:Skin / Q000528:radiation effects*
keywords: Monte Carlo simulation; Total Skin Electron Irradiation; dosimetry