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Comparison of MR Image Quality of Various Brachytherapy Applicators for Cervical Cancer

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A Soliman

A Soliman1*, A Elzibak1 , A Fatemi1 , H Safigholi1 , D Han1,2 , E Leung1 , A Ravi1 , W Song1 , (1) Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario, (2) University of California, San Diego, La Jolla, California


SU-E-T-208 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To compare the quality of Magnetic Resonance (MR) images of a recently-proposed novel direction-modulated brachytherapy (DMBT) tandem applicator against two conventional clinical applicators, using the current MRI clinical protocol.

Methods: Three tandem applicators were compared: (1) tungsten-based DMBT applicator, (2) conventional plastic applicator and (3) conventional stainless steel applicator. Physical dimensions were 5.4, 3.8 and 3.2 for tandems (1), (2) and (3), respectively. Each applicator was placed in the same water-phantom and independently scanned using the same parameters and coil settings on a 1.5 T 450w GE scanner. Images were acquired using T2-weighted turbo-spin-echo (TSE) with 8-channel body coil. Acquisition parameters were TR/TE =7000/108 ms; acquisition matrix = 320 x 256; 30 slices with 4 mm thickness and 0.5 gap; pixel bandwidth = 122 Hz and voxel size = 0.5 x 0.625 mm2 and number of excitations (NEX) = 4. Multiple acquisitions were obtained in para-sagittal and para-axial views (with respect to the tandem axis) for each applicator. Diameters of the tandem were measured at multiple angles and multiple locations and compared to the physical dimensions of the corresponding tandems.

Results: Minimal susceptibility artifact was observed with the DMBT and the plastic tandems. The stainless steel tandem produced significantly larger artifact than the first two tandems. The average diameter of the DMBT applicator measured 5.94 ± 0.3 mm. The average diameter of the plastic tandem measured 3.9 ± 0.1 mm. The maximum extent of artifact was 1.5 mm and 0.7 mm for DMBT and plastic tandems, respectively. The susceptibility artifact induced by the stainless steel tandem prevented the measurement of its diameter, and the edges of the tandem could not be identified in any acquisition.

Conclusion: This work demonstrated that the plastic and the tungsten-based DMBT tandem applicators are both suitable for MRI-guided brachytherapy of cervical cancer.

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