Program Information
A Novel Direction Modulated Brachytherapy (DMBT) Concept Tandem Applicator with Dynamic Shielding Using 169Yb Source for Cervical Cancer Brachytherapy
H Safigholi1*, D Han2 , S Mashouf1 , A Shaaer3 , A S. Meigooni4 , W Song1 , (1) Department of Medical Physics,Sunnybrook Health Science Center, University of Toronto, Toronto, ON, (2) Department of Radiation Oncology, University of California San Francisco, San Francisco, CA (3) Department of Biomedical Physics, Ryerson University, Toronto, ON, (4)Department of Radiation Therapy, Comprehensive Cancer centers of Nevada, Nevada, Las Vegas
Presentations
TU-C3-GePD-T-1 (Tuesday, August 1, 2017) 10:30 AM - 11:00 AM Room: Therapy ePoster Lounge
Purpose: To propose and evaluate a novel design concept tandem applicator utilizing dynamic shielding for delivering high-dose-rate brachytherapy of cervical cancer with 169Yb source.
Methods: In 2014, we proposed a static direction modulated brachytherapy(S-DMBT) tandem applicator designed for IGABT of cervical cancer. The design has 6 peripheral holes of 1.3-mm width, grooved along a 5.4-mm diameter nonmagnetic tungsten-alloy rod(18.0g/cc). In this study, a new DMBT concept applicator with dynamic shielding (D-DMBT) which has a single central hole with a small window that acts to collimate a highly directional beam is proposed. This shield is then assumed to dynamically rotate to deliver an arc-therapy while modulating intensity at each angular dwell position to generate customized dose distribution. The S-DMBT and six angular windows of D-DMBT designs(i.e., 20,33,53,60,90, and 120-degrees) in combination with the169Yb source are MC simulated and imported into an in-house developed inverse planning code to generate treatment plans for a single representative patient case, along with a conventional tandem-and-ring “reference” plan. All plans were normalized to the same CTVHR D90. The D2cm3 for OAR such as bladder, rectum, and sigmoid, and D98 and D10 for CTVHR were compared to reference plan.
Results: As expected, the beam directionality (angular narrowness) increased as the window angle decreased. For S-DMBT and D-DMBT, the generated plans were of higher quality than that of reference plans. For smaller collimation angles(<60◦), the generation of hot spots in the target were more frequent and greater in magnitude. The bladder D2cm3 decreased by -3.3%,-4.28%,-5.71%,-6.33%,-8.74%,-9.63%, and -9.28% for the 20,33,53,60,90,120-degrees of D-DMBT and S-DMBT tandem-and-ring, respectively. The corresponding values for the rectum(sigmoid) were -2.28%(-0.62%), -1.32%(-2.42%), -1.16%(-2.8%), -3.25%(-7.14%), -4.57%(-8.01%), -5.65%(-8.39%), and -6.13%(-7.14%), respectively.
Conclusion: We have proposed a novel design concept tandem applicator that can generate highly conformal dose distributions tailored for patient-specific anatomy, to be used with IGABT.
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