Integration of rotatable tandem applicator to conventional ovoid applicator toward complete framework of intensity modulated brachytherapy (IMBT) for cervical cancer |
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| Institution: | 1. Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, South Korea;2. Department of Radiation Oncology, Asan Medical Center, Seoul, South Korea;3. Proton Therapy Center, National Cancer Center, Goyang, South Korea;1. Radiation Application Research School, Nuclear Science and Technology Research Institute (NSTRI), Tehran, Iran;2. Department of Medical Radiation Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran;3. Medical Physics Department, School of Medicine, Iran University of Medical Sciences, P.O. Box: 14155-6183 Tehran, Iran;1. Trillium Health Partners, Peel Regional Cancer Centre, Mississauga, ON, Canada;2. University of Toronto, Department of Radiation Oncology, Toronto, ON, Canada;3. University of Ryerson, Department of Physics, Toronto, Canada;4. Sunnybrook Health Sciences Centre, Toronto, Canada;5. York University, Department of Physics and Astronomy, Toronto, ON, Canada;1. Department of Medical Physics, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku Tokyo 104-0045, Japan;2. Department of Radiological Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, 7-2-10, Higashioku, Arakawa-ku Tokyo 116-8551, Japan;3. Division of Research and Development for Boron Neutron Capture Therapy, National Cancer Center Exploratory Oncology Research & Clinical Trial Center, Tsukiji 5-1-1, Chuo-ku, Tokyo 104-0045, Japan;4. Department of Radiation Oncology, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku Tokyo 104-0045, Japan;1. AOU Careggi, Medical Physics Unit, Florence, Italy;2. University of Florence-Department of Experimental and Clinical Biomedical Sciences “Mario Serio”, Florence, Italy;3. AOU Careggi, Radiotherapy Unit, Florence, Italy;4. Santa Maria Annunziata Hospital, Radiation Oncology Unit, Florence, Italy;1. Department of Medical Physics and Radiation Protection, Hospital Universitario La Paz, Madrid, Spain;2. Servicio de Radiofísica y Protección Radiológica, ESI/OSI Donostialdea, Donostia, Spain;3. Department of Nuclear Medicine, Hospital Universitario La Paz, Madrid, Spain;4. Servicio de Radiofísica y Protección Radiológica. Hospital Universitario Rey Juan Carlos, Madrid, Spain;5. Independent researcher, Madrid, Spain |
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| Abstract: | A new tandem applicator with tungsten shield for Ir-192 radiation source used in intra-cavitary brachytherapy (ICBT) enabled intensity modulated brachytherapy (IMBT) in cervical cancer treatment through fluence-modulation by rotating shield. Our previous work employed group-wise and element-wise sparsity constraints for plan optimization of tandem applicator to minimizes the number of activated angles and source dwell points for delivery efficiency. It, however, did not incorporate the ovoid applicators into the optimizing process, which is generally used to prevent cancer recurrence. To integrate ovoid applicators to the new tandem applicator, this work proposed a comprehensive framework that modifies 1) dose deposition matrix for inverse planning, and 2) plan optimizing algorithm. The dose deposition matrix was newly formulated by the Monte-Carlo simulated dose distribution for 10 positions of ovoid applicators, followed by combining those with tandem-associated dose deposition matrix. The plan optimizing algorithm decomposed entire elements into tandem and ovoid applicators, which were governed by different constraints adaptive to specified plan objectives. The integrated framework was compared against conventional ICBT, and IMBT with tandem only for three patients with asymmetric dose distributions. Integrated IMBT framework resulted in the most optimal plans. Including fluence-modulation by rotating-shield outperformed conventional ICBT in dose sparing to critical organs. Adopting ovoid applicators to the optimization yielded more conformal dose distribution around inferior, laterally expanded region of target volume. The resulting plans reduced D5cc and D2cc by 30.9% and 27.8% for critical organs over conventional ICBT, and by 20.6% and 21.5% for target volume over IMBT with tandem only. |
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| Keywords: | Intensity modulated brachytherapy (IMBT) Intra-cavitary brachytherapy (ICBT) Rotating shield Inverse planning Plan optimization |
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