| 研究実績の概要 |
The aim of this study in FY2014 was to investigate the impact of tissue inhomogeneity on dose distributions in CT-image-based intracavitary brachytherapy (ICBT) for cervical cancer using Monte Carlo simulations.
A Particle and Heavy Ion Transport code System was employed for the Monte Carlo simulations. The calculation of two dose distributions in a CT image for a cervical cancer patient and in a water phantom, which has the same size with the CT image, was performed by positioning an encapsulated 192Ir source (HDR 192Ir model mHDR-v2r) with an air kerma strength of 40,000 U at the first dwell position of a tandem in the CT image and the water phantom. A billion histories were delivered to the CT image and the phantom. Cut-off energies of photon, electron, and positron were set as 1 keV, 0.512 MeV, and 0.512 MeV, respectively. The gamma evaluation was used for evaluating the difference between the two dose distributions.
Gamma pass rates (3 mm/3%) between two dose distributions of the CT image and water phantom in the axial, sagittal, and coronal views were 32.55% , 39.31%, 49.98 %, respectively, for the whole calculation space. This study revealed that the impact of the tissue inhomogeneity on dose distributions could not be negligible for CT-image-based intracavitary brachytherapy (ICBT) for cervical cancer.
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| 今後の研究の推進方策 |
Since we developed an approach for simulating intracavitary brachytherapy using 192Ir and computed tomography (CT) images of patients in FY2014, we are going to develop a whole system including a mobile gamma camera in FY2015. Furthermore, we will develop a framework for identifying regions of a tumor and organs at risk. In addition, an approach for image registration between CT and magnetic resonance images.
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