Dose perturbation induced by radiographic contrast inside brachytherapy balloon applicators.
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.
Kirk
Michael C
MC
Department of Medical Physics and Radiation Oncology, Rush University Medical Center, Chicago, Illinois 60612, USA. michael_c_kirk@rush.edu
Hsi
Wen C
WC
Chu
James C H
JC
Niu
Honquan
H
Hu
Zenan
Z
Bernard
Damian
D
Dickler
Adam
A
Nguyen
Cam
C
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
D003287:Contrast Media