title: Verifying monitor unit calculations for tangential whole breast fields in 3-dimensional planning.
abstract: An essential component of quality assurance in radiation therapy is verifying the accuracy of monitor unit calculations. For tangential breast fields, monitor unit differences between primary calculations and second checks are usually larger than considered acceptable at other anatomical sites. A simple model to reconcile the differences between sophisticated and simple algorithms is presented, based on estimating the the volume irradiated by the field, replacing the breast contour with a rectangular block having an equal volume but a new field width which provides almost equivalent scatter to the prescription point. This analysis can also assist the treatment planning physicist in selecting a tolerance window for verifying monitor unit calculations for tangential breast fields.
authors.affiliation: Department of Medical Physics, Tom Baker Cancer Centre.|Department of Oncology, University of Calgary.|Department of Physics and Astronomy, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Ian
authors.initials: I
authors.lastname: Kay
authors.affiliation: Department of Medical Physics, Tom Baker Cancer Centre.|Department of Oncology, University of Calgary.|Department of Physics and Astronomy, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Tyler
authors.initials: T
authors.lastname: Meyer
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008954:Models, Biological; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012062:Relative Biological Effectiveness; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity