title: Inverse-planned modulated-arc total-body irradiation.
abstract: OBJECTIVE
  To develop a simple and robust method for inverse-planned total-body irradiation (TBI) that is more comfortable and has better dose homogeneity than the conventional forward-planned techniques and that can be delivered in a standard-sized treatment vault.
  
  
  METHODS
  Modulated-arc TBI (MATBI) utilizes an arc of static open-field beams to irradiate patients as they lay on a stationary couch beneath the gantry, with cerrobend blocks suspended over organs at risk to provide shielding. Prior to treatment, full-body computed tomography (CT) images are acquired of each patient and imported into the PINNACLE(3) planning system, which modulates the monitor units for the open-field beams to optimize the body dose uniformity. The volume of the body within 10% of the prescription dose, V(±10), is used as a metric to evaluate the dose uniformity. For comparison to MATBI, the dose distribution of a conventional forward-planned treatment is also calculated. Quality assurance measurements are acquired before treatment by delivering the plans to a phantom and during treatment with an ionization chamber inside a buildup block, placed between the patient's ankles.
  
  
  RESULTS
  For MATBI, the achieved values of V(±10) were 75.8%, 90.2%, 84.6%, and 79.8% compared to 60.3%, 77.4%, 65.6%, and 68.5% for the conventional TBI technique, respectively. The pretreatment ion chamber measurements in the phantom had an average error of 1.2%. Those acquired during treatment had larger errors, with most points being within 3% of predictions.
  
  
  CONCLUSIONS
  MATBI provides better dose uniformity and comfort than the conventional forward-planned TBI techniques. In addition, the technique can be implemented on most linacs, in standard-sized vaults, without the use of a translating couch.
authors.affiliation: Department of Radiation Oncology, University of California, San Francisco, CA, USA.
authors.forename: Neil
authors.initials: N
authors.lastname: Kirby
authors.forename: Mareike
authors.initials: M
authors.lastname: Held
authors.forename: Olivier
authors.initials: O
authors.lastname: Morin
authors.forename: Shannon
authors.initials: S
authors.lastname: Fogh
authors.forename: Jean
authors.initials: J
authors.lastname: Pouliot
mesh_terms: D019583:Dose Fractionation, Radiation; D006801:Humans; D011786:Quality Control; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012399:Rotation; D013997:Time Factors; D014916:Whole-Body Irradiation / Q000379:methods*