横川 航平 (ヨコカワ コウヘイ)

北海道大学病院 中央診療施設等助教
Last Updated :2024/12/06

■研究者基本情報

学位

  • 博士(工学), 北海道大学

Researchmap個人ページ

研究者番号

  • 70916527

研究キーワード

  • 医学物理
  • 放射線治療

研究分野

  • ライフサイエンス, 放射線科学, 陽子線治療
  • ライフサイエンス, 放射線科学, 医学物理

■経歴

経歴

  • 2021年06月 - 現在
    北海道大学病院, 医学物理部, 医学物理士
  • 2020年04月 - 2021年05月
    北海道大学工学研究院, 応用量子科学部門 医工連携放射線医学物理分野, 博士研究員

学歴

  • 2020年03月, 北海道大学, 大学院工学院, 量子理工学専攻 博士後期課程, 日本国

■研究活動情報

受賞

  • 2021年04月, 日本医学物理学会, JSMP121大会長賞(Cypos賞)シルバー               
    A method for evaluating the achievement probabilities of prescribed dose criteria under arbitrary respiratory motion in particle therapy
  • 2021年02月, 日本原子力学会北海道支部, 支部奨励賞               
    A method for evaluating the achievement probabilities of dose criteria under respiratory-motion in proton beam spot-scanning method
  • 2017年02月, 日本原子力学会北海道支部, 支部奨励賞               
    Forming a uniform 3-D dose distribution using by a deformed Bragg curve in spot-scanning method of low-energy beam region

論文

  • Investigation of interfractional range variation owing to anatomical changes with beam directions based on water equivalent thickness in proton therapy for pancreatic cancer.
    Yuhei Kikkawa, Hideaki Ueda, Yusuke Uchinami, Norio Katoh, Hidefumi Aoyama, Yoichi M Ito, Kohei Yokokawa, Ye Chen, Taeko Matsuura, Naoki Miyamoto, Seishin Takao
    Journal of radiation research, 2024年10月08日, [国際誌]
    英語, 研究論文(学術雑誌), To assess the interfractional anatomical range variations (ARVs) with beam directions and their impact on dose distribution in intensity modulated proton therapy, we analyzed water equivalent thickness (WET) from 10 patients with pancreatic cancer. The distributions of the interfractional WET difference ($\Delta{\mathrm{WET } }^{\theta }$) across 360° were visualized using polar histograms. Interfractional ARVs were evaluated using the mean absolute error and ΔWET pass rate, indicating the percentage of $\Delta \mathrm{WE},{\mathrm{T } }^{\theta }$ < thresholds. The impact on dose distribution in proton therapy was evaluated based on two treatment plans for 40 Gy(RBE)/5 fractions: 'Plan A', using two beam angles, in which the target was closest to the body surface among four perpendicular directions; and 'Plan B', using two beam angles with small ARVs. Analysis revealed individual variations in angular trends of interfractional ARVs. Three distinct trends were identified: Group 1 exhibited small ARVs around posterior directions; Group 2 exhibited small ARVs except ~60°; Group 3 demonstrated minimal ARVs only ~90°. In dose evaluation, while 150° and 210° were selected in Plan B for 9 out of 10 patients, for the remaining patient, 60° and 90° were chosen. Comparing dose volume histogram parameters for all patients, Plan B significantly reduced target coverage loss while maintaining organ-at-risk sparing comparable to Plan A. These results demonstrated that selecting beam angles with small interfractional ARVs for each patient enhances the robustness of dose distribution, reducing target coverage loss.
  • Application of motion prediction based on a long short-term memory network for imaging dose reduction in real-time tumor-tracking radiation therapy.
    Kazuki Numakura, Seishin Takao, Taeko Matsuura, Kouhei Yokokawa, Ye Chen, Yusuke Uchinami, Hiroshi Taguchi, Norio Katoh, Hidefumi Aoyama, Satoshi Tomioka, Naoki Miyamoto
    Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB), 125, 104507, 104507, 2024年09月, [国際誌]
    英語, 研究論文(学術雑誌), PURPOSE: To demonstrate the possibility of using a lower imaging rate while maintaining acceptable accuracy by applying motion prediction to minimize the imaging dose in real-time image-guided radiation therapy. METHODS: Time-series of three-dimensional internal marker positions obtained from 98 patients in liver stereotactic body radiation therapy were used to train and test the long-short-term memory (LSTM) network. For real-time imaging, the root mean squared error (RMSE) of the prediction on three-dimensional marker position made by LSTM, the residual motion of the target under respiratory-gated irradiation, and irradiation efficiency were evaluated. In the evaluation of the residual motion, the system-specific latency was assumed to be 100 ms. RESULTS: Except for outliers in the superior-inferior (SI) direction, the median/maximum values of the RMSE for imaging rates of 7.5, 5.0, and 2.5 frames per second (fps) were 0.8/1.3, 0.9/1.6, and 1.2/2.4 mm, respectively. The median/maximum residual motion in the SI direction at an imaging rate of 15.0 fps without prediction of the marker position, which is a typical clinical setting, was 2.3/3.6 mm. For rates of 7.5, 5.0, and 2.5 fps with prediction, the corresponding values were 2.0/2.6, 2.2/3.3, and 2.4/3.9 mm, respectively. There was no significant difference between the irradiation efficiency with and that without prediction of the marker position. The geometrical accuracy at lower frame rates with prediction applied was superior or comparable to that at 15 fps without prediction. In comparison with the current clinical setting for real-time image-guided radiation therapy, which uses an imaging rate of 15.0 fps without prediction, it may be possible to reduce the imaging dose by half or more. CONCLUSIONS: Motion prediction can effectively lower the frame rate and minimize the imaging dose in real-time image-guided radiation therapy.
  • Clinical application of real-time tumor-tracking for stereotactic volumetric modulated arc therapy for liver tumors.
    Naoki Miyamoto, Norio Katoh, Takahiro Kanehira, Kohei Yokokawa, Ryusuke Suzuki, Yusuke Uchinami, Hiroshi Taguchi, Daisuke Abo, Hidefumi Aoyama
    Physics and imaging in radiation oncology, 31, 100623, 100623, 2024年07月, [国際誌]
    英語, 研究論文(学術雑誌), Real-time tumor-tracking volumetric modulated arc therapy (RT-VMAT) enabling beam-gating based on continuous X-ray tracking of the three-dimensional position of internal markers is relevant for moving tumors. Dose-volume characteristics and treatment time were evaluated in ten consecutive patients who underwent liver stereotactic body radiation therapy with RT-VMAT. Target dose conformity and sparing of the stomach and the intestine were improved comparing RT-VMAT with RT-3D conformal radiotherapy. The mean treatment time for each fraction was less than 10 min. RT-VMAT could be effective, especially for targets located adjacent to organs at risk.
  • Technical note: Application of an optical hydrophone to ionoacoustic range detection in a tissue-mimicking agar phantom.
    Shota Sueyasu, Koki Kasamatsu, Taisuke Takayanagi, Ye Chen, Yasutoshi Kuriyama, Yoshihiro Ishi, Tomonori Uesugi, Wolfgang Rohringer, Mehmet Burcin Unlu, Nobuki Kudo, Kohei Yokokawa, Seishin Takao, Naoki Miyamoto, Taeko Matsuura
    Medical physics, 2023年12月21日, [国際誌]
    英語, 研究論文(学術雑誌), BACKGROUND: Ionoacoustics is a promising approach to reduce the range uncertainty in proton therapy. A miniature-sized optical hydrophone (OH) was used as a measuring device to detect weak ionoacoustic signals with a high signal-to-noise ratio in water. However, further development is necessary to prevent wave distortion because of nearby acoustic impedance discontinuities while detection is conducted on the patient's skin. PURPOSE: A prototype of the probe head attached to an OH was fabricated and the required dimensions were experimentally investigated using a 100-MeV proton beam from a fixed-field alternating gradient accelerator and k-Wave simulations. The beam range of the proton in a tissue-mimicking phantom was estimated by measuring γ-waves and spherical ionoacoustic waves with resonant frequency (SPIRE). METHODS: Four sizes of probe heads were fabricated from agar blocks for the OH. Using the prototype, the γ-wave was detected at distal and lateral positions to the Bragg peak on the phantom surface for proton beams delivered at seven positions. For SPIRE, independent measurements were performed at distal on- and off-axis positions. The range positions were estimated by solving the linear equation using the sensitive matrix for the γ-wave and linear fitting of the correlation curve for SPIRE; they were compared with those measured using a film. RESULTS: The first peak of the γ-wave was undistorted with the 3 × 3 × 3-cm3 probe head used at the on-axis and 3-cm off-axis positions. The range positions estimated by the γ-wave agreed with the film-based range in the depth direction (the maximum deviation was 0.7 mm), although a 0.6-2.1 mm deviation was observed in the lateral direction. For SPIRE, the deviation was <1 mm for the two measurement positions. CONCLUSIONS: The attachment of a relatively small-sized probe head allowed the OH to measure the beam range on the phantom surface.
  • Predicting the daily gastrointestinal doses of stereotactic body radiation therapy for pancreatic cancer based on the shortest distance between the tumor and the gastrointestinal tract using daily computed tomography images
    Yusuke Uchinami, Takahiro Kanehira, Keiji Nakazato, Yoshihiro Fujita, Fuki Koizumi, Shuhei Takahashi, Manami Otsuka, Koichi Yasuda, Hiroshi Taguchi, Kentaro Nishioka, Naoki Miyamoto, Kohei Yokokawa, Ryusuke Suzuki, Keiji Kobashi, Keita Takahashi, Norio Katoh, Hidefumi Aoyama
    BJR|Open, 5, 1, British Institute of Radiology, 2023年08月
    研究論文(学術雑誌), Objectives:

    We aimed to investigate whether daily computed tomography (CT) images could predict the daily gastroduodenal, small intestine, and large intestine doses of stereotactic body radiation therapy (SBRT) for pancreatic cancer based on the shortest distance between the gross tumor volume (GTV) and gastrointestinal (GI) tract.

    Methods:

    Twelve patients with pancreatic cancer received SBRT of 40 Gy in five fractions. We recalculated the reference clinical SBRT plan (PLANref) using daily CT images and calculated the shortest distance from the GTV to each GI tract. The maximum dose delivered to 0.5 cc (D0.5cc) was evaluated for each planning at-risk volume of the GI tract. Spearman’s correlation test was used to determine the association between the daily change in the shortest distance (Δshortest distance) and the ratio of ΔD0.5cc dose to D0.5cc dose in PLANref (ΔD0.5cc/PLANref) for quantitative analysis.

    Results:

    The median shortest distance in PLANref was 0 mm in the gastroduodenum (interquartile range, 0–2.7), 16.7 mm in the small intestine (10.0–23.7), and 16.7 mm in the large intestine (8.3–28.1 mm). The D0.5cc of PLANref in the gastroduodenum was >30 Gy in all patients, with 10 (83.3%) having the highest dose. A significant association was found between the Δshortest distance and ΔD0.5cc/ PLANref in the small or large intestine (p < 0.001) but not in the gastroduodenum (p = 0.404).

    Conclusions:

    The gastroduodenum had a higher D0.5cc and predicting the daily dose was difficult. Daily dose calculations of the GI tract are recommended for safe SBRT.

    Advances in knowledge:

    This study aimed to predict the daily doses in SBRT for pancreatic cancer from the shortest distance between the GTV and the gastrointestinal tract. Daily changes in the shortest distance can predict the daily dose to the small or large intestines, but not to the gastroduodenum.
  • Evaluation of short-term gastrointestinal motion and its impact on dosimetric parameters in stereotactic body radiation therapy for pancreatic cancer
    Yusuke Uchinami, Takahiro Kanehira, Yoshihiro Fujita, Naoki Miyamoto, Kohei Yokokawa, Fuki Koizumi, Motoyasu Shido, Shuhei Takahashi, Manami Otsuka, Koichi Yasuda, Hiroshi Taguchi, Keiji Nakazato, Keiji Kobashi, Norio Katoh, Hidefumi Aoyama
    Clinical and Translational Radiation Oncology, 39, 100576, 100576, Elsevier BV, 2023年03月, [査読有り], [国際誌]
    英語, 研究論文(学術雑誌), BACKGROUND: The aim of this study is to quantify the short-term motion of the gastrointestinal tract (GI-tract) and its impact on dosimetric parameters in stereotactic body radiation therapy (SBRT) for pancreatic cancer. METHODS: The analyzed patients were eleven pancreatic cancer patients treated with SBRT or proton beam therapy. To ensure a fair analysis, the simulation SBRT plan was generated on the planning CT in all patients with the dose prescription of 40 Gy in 5 fractions. The GI-tract motion (stomach, duodenum, small and large intestine) was evaluated using three CT images scanned at spontaneous expiration. After fiducial-based rigid image registration, the contours in each CT image were generated and transferred to the planning CT, then the organ motion was evaluated. Planning at risk volumes (PRV) of each GI-tract were generated by adding 5 mm margins, and the volume receiving at least 33 Gy (V33) < 0.5 cm3 was evaluated as the dose constraint. RESULTS: The median interval between the first and last CT scans was 736 s (interquartile range, IQR:624-986). To compensate for the GI-tract motion based on the planning CT, the necessary median margin was 8.0 mm (IQR: 8.0-10.0) for the duodenum and 14.0 mm (12.0-16.0) for the small intestine. Compared to the planned V33 with the worst case, the median V33 in the PRV of the duodenum significantly increased from 0.20 cm3 (IQR: 0.02-0.26) to 0.33 cm3 (0.10-0.59) at Wilcoxon signed-rank test (p = 0.031). CONCLUSION: The short-term motions of the GI-tract lead to high dose differences.
  • Technical Note: Performance evaluation of volumetric imaging based on motion modeling by principal component analysis
    Suzuka Asano, Keishi Oseki, Seishin Takao, Koichi Miyazaki, Kohei Yokokawa, Taeko Matsuura, Hiroshi Taguchi, Norio Katoh, Hidefumi Aoyama, Kikuo Umegaki, Naoki Miyamoto
    Medical Physics, 50, 2, 993, 999, Wiley, 2022年12月03日, [査読有り], [国際誌]
    英語, 研究論文(学術雑誌), PURPOSE: To quantitatively evaluate the achievable performance of volumetric imaging based on lung motion modeling by principal component analysis (PCA). METHODS: In volumetric imaging based on PCA, internal deformation was represented as a linear combination of the eigenvectors derived by PCA of the deformation vector fields evaluated from patient-specific four-dimensional-computed tomography (4DCT) datasets. The volumetric image was synthesized by warping the reference CT image with a deformation vector field which was evaluated using optimal principal component coefficients (PCs). Larger PCs were hypothesized to reproduce deformations larger than those included in the original 4DCT dataset. To evaluate the reproducibility of PCA-reconstructed volumetric images synthesized to be close to the ground truth as possible, mean absolute error (MAE), structure similarity index measure (SSIM) and discrepancy of diaphragm position were evaluated using 22 4DCT datasets of nine patients. RESULTS: Mean MAE and SSIM values for the PCA-reconstructed volumetric images were approximately 80 HU and 0.88, respectively, regardless of the respiratory phase. In most test cases including the data of which motion range was exceeding that of the modeling data, the positional error of diaphragm was less than 5 mm. The results suggested that large deformations not included in the modeling 4DCT dataset could be reproduced. Furthermore, since the first PC correlated with the displacement of the diaphragm position, the first eigenvector became the dominant factor representing the respiration-associated deformations. However, other PCs did not necessarily change with the same trend as the first PC, and no correlation was observed between the coefficients. Hence, randomly allocating or sampling these PCs in expanded ranges may be applicable to reasonably generate an augmented dataset with various deformations. CONCLUSIONS: Reasonable accuracy of image synthesis comparable to those in the previous research were shown by using clinical data. These results indicate the potential of PCA-based volumetric imaging for clinical applications.
  • Real-time CT image generation based on voxel-by-voxel modeling of internal deformation by utilizing the displacement of fiducial markers.
    Risa Hayashi, Koichi Miyazaki, Seishin Takao, Kohei Yokokawa, Sodai Tanaka, Taeko Matsuura, Hiroshi Taguchi, Norio Katoh, Shinichi Shimizu, Kikuo Umegaki, Naoki Miyamoto
    Medical physics, 48, 9, 5311, 5326, 2021年07月14日, [査読有り], [国際誌]
    英語, 研究論文(学術雑誌), PURPOSE: To show the feasibility of real-time CT image generation technique utilizing internal fiducial markers that facilitate the evaluation of internal deformation. METHODS: In the proposed method, linear regression model that can derive internal deformation from the displacement of fiducial markers is built for each voxel in the training process before the treatment session. Marker displacement and internal deformation are derived from the four-dimensional computed tomography (4DCT) dataset. In the treatment session, the three-dimensional deformation vector field is derived according to the marker displacement, which is monitored by the real-time imaging system. The whole CT image can be synthesized by deforming the reference CT image with a deformation vector field in real-time. To show the feasibility of the technique, image synthesis accuracy, and tumor localization accuracy were evaluated using dataset generated by extended NURBS-Based Cardiac-Torso (XCAT) phantom and clinical 4DCT datasets from six patients, containing ten CT datasets each. In the validation with XCAT phantom, motion range of the tumor in training data and validation data were about 10 and 15 mm, respectively, so as to simulate motion variation between 4DCT acquisition and treatment session. In the validation with patient 4DCT dataset, eight CT datasets from the 4DCT dataset were used in the training process. Two excluded inhale CT datasets can be regarded as the datasets with large deformations more than training dataset. CT images were generated for each respiratory phase using the corresponding marker displacement. Root mean squared error (RMSE), normalized RMSE (NRMSE) and structural similarity index measure (SSIM) between the original CT images and the synthesized CT images were evaluated as the quantitative indices of the accuracy of image synthesis. The accuracy of tumor localization was also evaluated. RESULTS: In the validation with XCAT phantom, the mean NRMSE, SSIM and three-dimensional tumor localization error were 7.5±1.1%, 0.95±0.02 and 0.4±0.3 mm, respectively. In the validation with patient 4DCT dataset, the mean RMSE, NRMSE, SSIM and three-dimensional tumor localization error in six patients were 73.7±19.6 HU, 9.2±2.6%, 0.88±0.04 and 0.8±0.6 mm, respectively. These results suggest that the accuracy of the proposed technique is adequate when the respiratory motion is within the range of the training dataset. In the evaluation with a marker displacement larger than that of the training dataset, the mean RMSE, NRMSE, and tumor localization error were about 100 HU, 13%, and less than 2.0 mm, respectively, except for one case having large motion variation. The performance of the proposed method was similar to those of previous studies. Processing time to generate the volumetric image was less than 100 ms. CONCLUSION: We have shown the feasibility of the real-time CT image generation technique for volumetric imaging.
  • Dynamic gating window technique for the reduction of dosimetric error in respiratory‐gated spot‐scanning particle therapy: An initial phantom study using patient tumor trajectory data
    Naoki Miyamoto, Kouhei Yokokawa, Seishin Takao, Taeko Matsuura, Sodai Tanaka, Shinichi Shimizu, Hiroki Shirato, Kikuo Umegaki
    Journal of Applied Clinical Medical Physics, 21, 4, 13, 21, Wiley, 2020年04月, [査読有り], [国際誌]
    英語, 研究論文(学術雑誌), Spot-scanning particle therapy possesses advantages, such as high conformity to the target and efficient energy utilization compared with those of the passive scattering irradiation technique. However, this irradiation technique is sensitive to target motion. In the current clinical situation, some motion management techniques, such as respiratory-gated irradiation, which uses an external or internal surrogate, have been clinically applied. In surrogate-based gating, the size of the gating window is fixed during the treatment in the current treatment system. In this study, we propose a dynamic gating window technique, which optimizes the size of gating window for each spot by considering a possible dosimetric error. The effectiveness of the dynamic gating window technique was evaluated by simulating irradiation using a moving target in a water phantom. In dosimetric characteristics comparison, the dynamic gating window technique exhibited better performance in all evaluation volumes with different effective depths compared with that of the fixed gate approach. The variation of dosimetric characteristics according to the target depth was small in dynamic gate compared to fixed gate. These results suggest that the dynamic gating window technique can maintain an acceptable dose distribution regardless of the target depth. The overall gating efficiency of the dynamic gate was approximately equal or greater than that of the fixed gating window. In dynamic gate, as the target depth becomes shallower, the gating efficiency will be reduced, although dosimetric characteristics will be maintained regardless of the target depth. The results of this study suggest that the proposed gating technique may potentially improve the dose distribution. However, additional evaluations should be undertaken in the future to determine clinical applicability by assuming the specifications of the treatment system and clinical situation.
  • A new SOBP-formation method by superposing specially shaped Bragg curves formed by a mini-ridge filter for spot scanning in proton beam therapy
    K. Yokokawa, M. Furusaka, T. Matsuura, S. Hirayama, K. Umegaki
    Physica Medica, 67, 70, 76, Elsevier BV, 2019年11月, [査読有り], [筆頭著者]
    英語, 研究論文(学術雑誌)

講演・口頭発表等

  • 膵がん定位放射線治療におけるVMATを用いたプランライブラリ内包型治療計画法の検討               
    横川航平, 宮本直樹, 金平孝博, 鈴木隆介, 松尾勇斗, 宮崎智彦, 打浪雄介, 田口大志, 加藤徳雄, 青山英史
    第37回高精度放射線外部照射部会学会, 2024年03月02日, 日本語, 口頭発表(一般)
  • 呼吸性移動の存在下における粒子線治療時の線量基準の達成確率評価手法               
    K. Yokokawa, K. Kobashi, N. Miyamoto, K. Umegaki
    第121回日本医学物理学会学術大会, 2021年04月, 英語, 口頭発表(一般)
  • 呼吸性移動の存在下における陽子線スポットスキャニング照射時の治療計画の線量基準の達成確率評価方法               
    K. Yokokawa, K. Kobashi, N. Miyamoto, K. Miyazaki, K. Umegaki
    日本原子力学会北海道支部第38回研究発表会, 2021年02月, 日本語, 口頭発表(一般)
  • スポットスキャニング陽子線治療における可変ゲーティング法を用いた線量誤差の低減               
    横川航平, 宮本直樹, 高尾聖心, 松浦妙子, 田中創大, 清水伸一, 白土博樹, 梅垣菊男
    日本放射線腫瘍学会第33回学術大会, 2020年10月, 日本語, 口頭発表(一般)
  • 呼吸同期スポットスキャニング粒子線治療における線量誤差低減のための動的ゲートウィンドウ技術               
    K. Yokokawa, N. Miyamoto, S. Takao, T. Matsuura, S. Tanaka, S. Shimizu, H. Shirato, K. Umegaki
    第119回日本医学物理学会学術大会, 2020年05月, 英語

所属学協会

  • 日本放射線腫瘍学会               
  • 日本医学物理学会               

共同研究・競争的資金等の研究課題

担当教育組織