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SU‐E‐T‐523: Investigation of Various MR‐Compatible Shielding Materials for Direction Modulated Brachytherapy (DMBT) Tandem Applicator for Cervical Cancer Treatment
Author(s) -
Safigholi H,
Han D,
Soliman A,
Meigooni A Soleimani,
Scanderbeg D,
Song W
Publication year - 2015
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4924885
Subject(s) - brachytherapy , electromagnetic shielding , materials science , dosimetry , intensity modulation , nuclear medicine , shields , radiation therapy , optics , medicine , radiology , physics , composite material , phase modulation , phase noise
Purpose: To evaluate various shielding materials such as Gold (Au), Osmium (Os), Tantalum (Ta), and Tungsten (W) based alloys for use with a novel intensity modulation capable direction modulated brachytherapy (DMBT) tandem applicator for image guided cervical cancer HDR brachytherapy. Methods: The novel MRI‐compatible DMBT tandem, made from nonmagnetic tungsten‐alloy rod with diameter of 5.4 mm, has 6 symmetric peripheral holes of 1.3 mm diameter with 2.05 mm distance from the center for a high degree intensity modulation capacity. The 0.3 mm thickness of bio‐compatible plastic tubing wraps the tandem. MCNPX was used for Monte Carlo simulations of the shields and the mHDR Ir‐192 V2 source. MC‐generated 3D dose matrices of different shielding materials of Au, Os, Ta, and W with 1 mm3 resolution were imported into an in‐house‐coded inverse optimization planning system to evaluate 19 clinical patient plans. Prescription dose was 15Gy. All plans were normalized to receive the same HRCTV D90. Results: In general, the plan qualities for various shielding materials were similar. The OAR D2cc for bladder was very similar for Au, Os, and Ta with 11.64±2.30Gy. For W, it was very close 11.65±2.30Gy. The sigmoid D2cc was 9.82±2.46Gy for Au and Os while it was 9.84±2.48Gy for Ta and W. The rectum D2cc was 7.44±3.06Gy for Au, 7.43±3.07Gy for Os, 7.48±3.05Gy for Ta, and 7.47±3.05Gy for W. The HRCTV D98 and V100 were very close with 16.37±1.87 Gy and 97.37±1.93 Gy, on average, respectively. Conclusion: Various MRI‐compatible shielding alloys were investigated for the DMBT tandem applicator. The clinical plan qualities were not significantly different among these various alloys, however. Therefore, the candidate metals (or in combination) can be used to select best alloys for MRI image guided cervical cancer brachytherapy using the novel DMBT applicator that is capable of unprecedented level of intensity modulation.