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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2013年第4期2卷 117-124页

作者： Akihiro Nakata Kunihiko Tateoka Kazunori Fujimoto yuichi Saito Takuya Nakazawa Tadanori Abe Masaki yano Koichi Sakata 1Department of Medical Physics Graduate School of Medicine Sapporo Medical University Sapporo Japan 4Radiation Therapy Research Institute Social Medical Corporation Teishinkai Sapporo Japan Department of Medical Physics Graduate School of Medicine Sapporo Medical University Sapporo Japan Department of Medical Physics Graduate School of Medicine Sapporo Medical University Sapporo Japan Department of Radiology Sapporo Medical University Sapporo Japan Department of Medical Physics Graduate School of Medicine Sapporo Medical University Sapporo Japan Nikko Memorial Hospital Muroran Japan

The reproducibility of patient setup is an important issue for head and neck cancers treated with intensity-modulated radiation therapy (IMRT). In this study, an image-guided radiation therapy (IGRT) system has been used to minimize the uncertainty of patient setup while standard thermoplastic masks were used to provide adequate immobilization for the head and neck. However, they do not provide sufficient immobilization of the shoulders, which is an important requirement in comprehensive nodal irradiation. Therefore, we investigated the setup and rotational shifts in head and neck cancer patients undergoing IMRT for which this immobilization device had been used together with an IGRT system. The setup and rotational shifts of patients were analyzed using the ExacTrac X-ray 6D IGRT system. The patients were classified as having head and neck tumors in the upper or lower regions. The upper neck nodes included lymph nodal level II while the lower neck nodes included lymph nodal levels III and IV. Clinical data from 227 treatment sessions of 12 head and neck cancer patients were analyzed. The random translational error in inter-and intra-fraction errors of the anterio-posterior (AP) direction might influence the rotational errors of pitch and roll in the upper region. At the same time, the random translational error in the inter-and intra-fraction errors of the AP direction might influence the rotational error of roll in the lower region. We believe that these random translational errors should be considered during treatment. We found variability in random translational errors for different regions in the anatomy of head and neck cancer patients due to rotational shifts. Depending on the location of the primary lesion or the selected nodal treatment targets, these relative positional variations should be considered when setup and rotational shifts are corrected with IGRT systems before treatment.

关键词： IMRT IGRT Radiation Therapy Immobilization Head and Neck Cancer

Solar power sail mission of OKEANOS

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Astrodynamics 2020年第3期4卷 233-248页

作者： Osamu Mori Jun Matsumoto Toshihiro Chujo Masanori Matsushita Hideki Kato Takanao Saiki yuichi Tsuda Jun'ichiro Kawaguchi Fuyuto Terui Yuya Mimasu Go Ono Naoko Ogawa Yuki Takao Yuki Kubo Kaoru Ohashi Ahmed Kiyoshi Sugihara Tatsuaki Okada Takahiro Iwata Hajime yano Japan Aerospace Exploration Agency Sagarmihara 252-5210Japan Tokyo Institute of Technology Tokyo 152-8550Japan The University of Tokyo Tokyo 113-8654Japan Patchedconics LLCSagarmihara 252-5210Japan

The solar power sail is an original Japanese concept in which electric power is generated by thin-film solar cells attached on the solar sail *** Aerospace Exploration Agency(JAXA)successfully demonstrated the world’s first solar power sail technology through IKAROS(Interplanetary Kite-craft Accelerated by Radiation of the Sun)mission in *** demonstrated photon propulsion and power generation using thin-film solar cells during its interplanetary *** up,solar power sails can generate enough power to drive high specific impulse ion thrusters in the outer planetary *** this concept,we propose a landing or sample return mission to directly explore a Jupiter Trojan asteroid using solar power sail-craft OKEANOS(Oversize Kite-craft for Exploration and AstroNautics in the Outer Solar System).After rendezvousing with a Trojan asteroid,a lander separates from OKEANOS to collect samples,and perform in-situ analyses in three proposed mission sequences,including sending samples back to *** paper proposes a system design for OKEANOS and includes analyses of the latest mission.

关键词： solar power sail Trojan asteroid landing in-situ analysis outer solar system OKEANOS

Method for Converting Cone-Beam CT Values into Hounsfield Units for Radiation Treatment Planning

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2017年第4期6卷 361-375页

作者： Tadanori Abe Kunihiko Tateoka yuichi Saito Takuya Nakazawa Masaki yano Kensei Nakata Masanori Someya Masakazu Hori Koichi Sakata Depertment of Radiation Oncology and Medical Physics Graduate School of Medicine Sapporo Medical University Sapporo Japan Department of Radiology KKR Sapporo Medical Center Sapporo Japan Preparatory Office for Proton Therapy Center Radiation Therapy Research Institute Social Medical Corporation Teishinkai Sapporo Japan Department of Radiology National Hospital Organization Hokkaido Cancer Center Sapporo Japan Department of Radiology Kushiro City General Hospital Kushiro Japan Department of Radiation Oncology School of Medicine Sapporo Medical University Sapporo Japan

Cone-beam CT (CBCT) images acquired during radiation treatment can be used to recalculate the dose distribution as well as to confirm the treatment location. However, it is difficult to obtain the electron densities (EDs) necessary for dose calculation from CBCT images because of the effects of scatter contamination during CBCT image acquisition. This paper presents a mathematical method for converting the pixel values of CBCT images (CBCT values) into Hounsfield units (HUs) of radiation treatment simulation CT (simCT) images for use in radiation treatment planning. CBCT values are converted into HUs by matching the histograms of the CBCT values with the histograms of the HUs for each slice via linear scaling of the CBCT values. For prostate cancer and head-and-neck cancer patients, the EDs obtained from converted CBCT values (mCBCT values) show good agreement with the EDs obtained from HUs, within approximately 3.0%, and the dose calculated on the basis of CBCT images shows good agreement with the dose calculated on the basis of the simCT images, within approximately 2.0%. Because the CBCT values are converted for each slice, this conversion method can account for variation in the CBCT values associated with differences in body size, body shape, and inner tissue structures, as well as in longitudinally displaced positions from the isocenter, unlike conventional methods that use electron density phantoms. This method improves on conventional CBCT-ED conversion and shows considerable potential for improving the accuracy of radiation treatment planning using CBCT images.

关键词： Cone-Beam Computed Tomography Hounsfield Unit Electron Density Ra-diation Treatment Planning

Effects of Beam Startup Characteristics on Dose Delivery Accuracy at Low Monitor Units in Step-and-Shoot Intensity Modulated Radiation Therapy

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2013年第1期2卷 1-5页

作者： Kazunori Fujimoto Kunihiko Tateoka Yuji Yaegashi Katsumi Shima Junji Suzuki yuichi Saito Akihiro Nakata Takuya Nakazawa Tadanori Abe Masaki yano Masanori Someya Kensei Nakata Masakazu Hori Masato Hareyama Koichi Sakata Department of Medical Physics Graduate School of Medicine Sapporo Medical University Sapporo Japan Department of Radiology Sapporo Medical University Sapporo Japan Radiation Therapy Research Institute Social Medical Corporation Teishinkai Sapporo Japan

Intensity modulated radiation therapy (IMRT) is a highly accurate technique that is usually implemented in either dynamic or step-and-shoot fashion with many segments each having low monitor units (MUs). The present study evaluated the effects of beam startup characteristics on the dose delivery accuracy for each segment at low MUs for step-and-shoot IMRT with an Elekta Precise accelerator at the highest dose rates. We used a two-dimensional semi-conductor detector for the dose measurements. The field size of each segment was assumed to be 20 ×20 cm2 and each segment was set to deliver 1 - 10 MUs. Our results show a variation in dose delivery accuracy between segments for the same IMRT beam, which can be attributed to the beam startup characteristics. This variability is attributed to the changes in the transient changes in the temperatures of the electron gun filament and the magnetron. That is, the transient increase in the temperature of the filament leads to increasing doses with time and that of the magnetron leads to decreasing doses with time during the first few MUs.

关键词： Startup Performance Step-and-Shoot IMRT Low Monitor Units

Hayabusa2’s station-keeping operation in the proximity of the asteroid Ryugu

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Astrodynamics 2020年第4期4卷 349-375页

作者： Yuto Takei Takanao Saiki Yukio Yamamoto Yuya Mimasu Hiroshi Takeuchi Hitoshi Ikeda Naoko Ogawa Fuyuto Terui Go Ono Kent Yoshikawa Tadateru Takahashi Hirotaka Sawada Chikako Hirose Shota Kikuchi Atsushi Fuji Takahiro Iwata Satoru Nakazawa Masahiko Hayakawa Ryudo Tsukizaki Satoshi Tanaka Masanori Matsushita Osamu Mori Daiki Koda Takanobu Shimada Masanobu Ozaki Masanao Abe Satoshi Hosoda Tatsuaki Okada Hajime yano Takaaki Kato Seiji Yasuda Kota Matsushima Tetsuya Masuda Makoto Yoshikawa yuichi Tsuda Japan Aerospace Exploration Agency Sagarmihara 252-5210Japan The Graduate University for Advanced Studies Sagarmihara 252-5210Japan NEC Aerospace Systems LtdFruchu 183-8502Japan NEC Corporation Puchu 183-8501Japan

The Japanese interplanetary probe Hayabusa2 was launched on December 3,2014 and the probe arrived at the vicinity of asteroid 162173 Ryugu on June 27,*** its 1.4 years of asteroid proximity phase,the probe successfully accomplished numbers of record-breaking achievements including two touchdowns and one artificial cratering experiment,which are highly expected to have secured surface and subsurface samples from the asteroid inside its sample container for the first time in *** Hayabusa2 spacecraft was designed not to orbit but to hover above the asteroid along the sub Earth *** orbital and geometrical configuration allows the spacecraft to utilize its high-gain antennas for telecommunication with the ground station on Earth while pointing its scientific observation and navigation sensors at the *** paper focuses on the regular station-keeping operation of Hayabusa2,which is called“home position”(HP)-keeping ***,together with the spacecraft design,an operation scheme called HP navigation(HPNAV),which includes a daily trajectory control and scientific observations as regular activities,is *** the description on the guidance,navigation,and control design as well as the framework of optical and radiometric navigation,the results of the HP-keeping operation including trajectory estimation and delta-V planning during the entire asteroid proximity phase are summarized and evaluated as a first ***,this paper states that the *** operation in the framework of HPNAV had succeeded without critical incidents,and the number of trajectory control delta-V was planned fficiently throughout the period.

关键词： small body mission station-keeping guidance,navigation,and control(GNC) optical and radiometric navigation