title: Technical note: contrast solution density and cross section errors in inhomogeneity-corrected dose calculation for breast balloon brachytherapy.
abstract: OBJECTIVE
  Recent recommendations by the American Association of Physicists in Medicine Task Group 186 emphasize the importance of understanding material properties and their effect on inhomogeneity-corrected dose calculation for brachytherapy. Radiographic contrast is normally injected into breast brachytherapy balloons. In this study, the authors independently estimate properties of contrast solution that were expected to be incorrectly specified in a commercial brachytherapy dose calculation algorithm.
  
  
  METHODS
  The mass density and atomic weight fractions of a clinical formulation of radiographic contrast solution were determined using manufacturers' data. The mass density was verified through measurement and compared with the density obtained by the treatment planning system's CT calibration. The atomic weight fractions were used to determine the photon interaction cross section of the contrast solution for a commercial high-dose-rate (HDR) brachytherapy source and compared with that of muscle.
  
  
  RESULTS
  The density of contrast solution was 10% less than that obtained from the CT calibration. The cross section of the contrast solution for the HDR source was 1.2% greater than that of muscle. Both errors could be addressed by overriding the density of the contrast solution in the treatment planning system.
  
  
  CONCLUSIONS
  The authors estimate the error in mass density and cross section parameters used by a commercial brachytherapy dose calculation algorithm for radiographic contrast used in a clinical breast brachytherapy practice. This approach is adaptable to other clinics seeking to evaluate dose calculation errors and determine appropriate density override values if desired.
authors.affiliation: Department of Radiation Oncology, University of Medicine and Dentistry of New Jersey, NJ, USA. kimlh@umdnj.edu
authors.forename: Leonard H
authors.initials: LH
authors.lastname: Kim
authors.forename: Miao
authors.initials: M
authors.lastname: Zhang
authors.forename: Roger W
authors.initials: RW
authors.lastname: Howell
authors.forename: Ning J
authors.initials: NJ
authors.lastname: Yue
authors.forename: Atif J
authors.initials: AJ
authors.lastname: Khan
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D003287:Contrast Media / Q000737:chemistry*; D006785:Hospitals, University; D006801:Humans; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D012996:Solutions; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media; D012996:Solutions