A three-field breast treatment technique with precise geometric matching using multileaf collimator–equipped linear accelerators

Abstract

Purpose Many authors have studied the problems associated with the three-field breast treatment, yet the proposed solutions present their own difficulties. This study presents a technique that overcomes these difficulties, reduces scatter to the contralateral breast, and improves setup reproducibility. Methods and materials Patients are set up with both arms raised superiorly on a breast board. A precise field-match is achieved by rotating the couch and collimator of the tangents, while the supraclavicular field is half-beam blocked using an independent jaw. The posterior borders of the tangents are conformally defined by multileaf collimation. Measurements were performed to verify the field matching and evaluate scatter doses. Results A smooth dose transition was found at the match line at all depths. Corner blocks and lower wedges were not used, which reduced the scatter to the contralateral breast compared with our prior technique. Conclusion The technique achieves a precise match while removing constraints on the tangents’ length and decreasing scatter dose. Procedures for simulation, planning, and treatment have been devised, along with a new patient setup routine incorporating orthogonal setup films and tattoos. This technique has been successfully implemented in routine treatment since September 2001. A program calculating the setup parameters is available at our website.