title: Dose perturbation induced by radiographic contrast inside brachytherapy balloon applicators.
abstract: Phantom measurements and Monte Carlo calculations have been performed for the purpose of characterizing the dose perturbation caused by radiographic contrast inside the MammoSite breast brachytherapy applicator. Specifically, the dose perturbation is quantified as a heterogeneity correction factor (HCF) for various balloon radii and contrast concentration levels. The dose perturbation is larger for larger balloon radii and higher contrast concentrations. Based on a validated Monte Carlo simulation, the calculated HCF values are 0.99 for a 2 cm radius balloon and 0.98 for a 3 cm radius balloon at 6% contrast concentration levels, and 0.89 and 0.87 for 2 and 3 cm radius balloons, respectively, at 100% contrast concentrations. For a typical implanted balloon radius of 2.4 cm, the HCF values decrease from 0.99 at 6% contrast concentration to 0.90 at 100% contrast concentration. For balloons implanted in patients at our institution, the mean HCF is 0.99, corresponding to a dose reduction of approximately 1%. The contrast effect results in a systematic reduction in the delivered dose, therefore the minimal amount of radiographic contrast necessary should be used.
authors.affiliation: Department of Medical Physics and Radiation Oncology, Rush University Medical Center, Chicago, Illinois 60612, USA. michael_c_kirk@rush.edu
authors.forename: Michael C
authors.initials: MC
authors.lastname: Kirk
authors.forename: Wen C
authors.initials: WC
authors.lastname: Hsi
authors.forename: James C H
authors.initials: JC
authors.lastname: Chu
authors.forename: Honquan
authors.initials: H
authors.lastname: Niu
authors.forename: Zenan
authors.initials: Z
authors.lastname: Hu
authors.forename: Damian
authors.initials: D
authors.lastname: Bernard
authors.forename: Adam
authors.initials: A
authors.lastname: Dickler
authors.forename: Cam
authors.initials: C
authors.lastname: Nguyen
mesh_terms: D000792:Angiography / Q000379:methods; D001918:Brachytherapy / Q000379:methods*; D002404:Catheterization / Q000379:methods*; D003287:Contrast Media; D006801:Humans; D019047:Phantoms, Imaging; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage
chemical_list: D003287:Contrast Media