title: Multileaf collimation in the treatment of the intact breast.
abstract: OBJECTIVE
  To compare multileaf-collimator beam shaping and conventional metal-alloy blocking in irradiation of the intact breast after breast-conserving surgery.
  
  
  METHODS
  Transmission dose was measured in a phantom, by using both types of blocking with 6- and 15-MV photon beams. Buildup data were collected, using a 6-MV photon beam, comparing open fields to various beam modifiers.
  
  
  RESULTS
  Contralateral breast transmission was reduced with the multileaf collimator from 4% to 1%. With the jaws and multileaf collimator, the primary beam component of 0.5% was eliminated. Buildup data for the multileaf collimator most closely resembled the surface dose when a blocking tray is not used and were slightly lower than those for the conventional mounted blocks. This relates to the use of the lower of the two sets of wedges on the multileaf collimator, which is closer to the patient and thus enhances the surface dose relative to the dose with an open field and no wedge.
  
  
  CONCLUSIONS
  Multileaf-collimator blocking for primary breast treatment is similar to conventional blocking, and the transition from one technique to another should be uneventful. The transmission dose to the contralateral breast is decreased with the multileaf collimator.
authors.affiliation: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
authors.forename: B
authors.initials: B
authors.lastname: McCormick
authors.forename: Y C
authors.initials: YC
authors.lastname: Lo
authors.forename: T
authors.initials: T
authors.lastname: LoSasso
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008875:Middle Aged; D011878:Radiotherapy / Q000295:instrumentation; D011879:Radiotherapy Dosage; D018714:Radiotherapy, Adjuvant