title: Delivery validation of an automated modulated electron radiotherapy plan.
abstract: OBJECTIVE
  Modulated electron radiation therapy (MERT) represents an active area of interest that offers the potential to improve healthy tissue sparing in treatment of certain cancer cases. Challenges remain however in accurate beamlet dose calculation, plan optimization, collimation method, and delivery accuracy. In this work, the authors investigate the accuracy and efficiency of an end-to-end MERT plan and automated delivery method.
  
  
  METHODS
  Treatment planning was initiated on a previously treated whole breast irradiation case including an electron boost. All dose calculations were performed using Monte Carlo methods and beam weights were determined using a research-based treatment planning system capable of inverse optimization. The plan was delivered to radiochromic film placed in a water equivalent phantom for verification, using an automated motorized tertiary collimator.
  
  
  RESULTS
  The automated delivery, which covered four electron energies, 196 subfields, and 6183 total MU was completed in 25.8 min, including 6.2 min of beam-on time. The remainder of the delivery time was spent on collimator leaf motion and the automated interfacing with the accelerator in service mode. Comparison of the planned and delivered film dose gave 3%/3mm gamma pass rates of 62.1%, 99.8%, 97.8%, 98.3%, and 98.7% for the 9, 12, 16, and 20 MeV, and combined energy deliveries, respectively. Delivery was also performed with a MapCHECK device and resulted in 3%/3 mm gamma pass rates of 88.8%, 86.1%, 89.4%, and 94.8% for the 9, 12, 16, and 20 MeV energies, respectively.
  
  
  CONCLUSIONS
  Results of the authors' study showed that an accurate delivery utilizing an add-on tertiary electron collimator is possible using Monte Carlo calculated plans and inverse optimization, which brings MERT closer to becoming a viable option for physicians in treating superficial malignancies.
authors.affiliation: Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Québec H3G 1A4, Canada.
authors.forename: T
authors.initials: T
authors.lastname: Connell
authors.affiliation: Medical Physics Department, Saskatoon Cancer Centre, 20 Campus Drive, Saskatoon, Saskatchewan S7N 4H4, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Alexander
authors.affiliation: Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Québec H3G 1A4, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Papaconstadopoulos
authors.affiliation: Medical Physics Department, McGill University Health Centre, Montreal, Québec H3G 1A4, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Serban
authors.affiliation: Department of Radiation Oncology, Jewish General Hospital, Montréal, Québec H3T 1E2, Canada and Medical Physics Unit, McGill University, Montreal, Québec H3G 1A4, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Devic
authors.affiliation: Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Québec H3G 1A4, Canada and Medical Physics Department, McGill University Health Centre, Montreal, Québec H3G 1A4, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Seuntjens
mesh_terms: D001940:Breast / Q000528:radiation effects; D001943:Breast Neoplasms / Q000532:radiotherapy; D004583:Electrons / Q000627:therapeutic use*; D005373:Film Dosimetry; D006801:Humans; D008954:Models, Biological; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011878:Radiotherapy / Q000295:instrumentation / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014867:Water
chemical_list: D014867:Water