Innovation
Application of External Radiation Therapy
In recent years, external radiation therapy requires submillimeter positional accuracy. To achieve this positional accuracy with radiation therapy equipment, it is up to medical professionals to check the accuracy. This gel dosimeter provides three-dimensional imaging of the "true" dose distribution for efficient, easy-to-understand quality control. Three-dimensional (3D) starshot allows a direct, comprehensive 3D evaluation of spatial radiation accuracy relative to the imaging isocenter*2. Figure 2 shows the displacements in the tests with and without an error.

Figure 2. Beam axes and treatment isocenters are reconstructed in three-dimensional space with and without an intentional error. The blue sphere indicates the area of the treatment isocenter—GA, Gantry angle, CA, Couch angle.
*2 Oshika R, Tachibana H, Seki K, Tachibana R, Moriya S, Sakae T. Technical Notes: Robustness of three-dimensional treatment and imaging isocenter testing using a new gel dosimeter and kilovoltage CBCT. Journal of Applied Clinical Medical Physics. 2024;e14439. doi: 10.1002/acm2.14439
Application to Brachytherapy
In high-dose-rate(HD)brachytherapy, three-dimensional images are acquired using CT and MR, and treatment plans are performed. Highly accurate treatments are provided. However, quality control throughout the entire process needs to be improved, and there is a potential for human error in the clinical workflow of HDR. This gel dosimeter has undergone quality control at your facility using X-ray CT. We provide safe treatment. Figure 3 shows the dosimeter after needle insertions, planning, and irradiation.

Figure 3. Gel dosimeter of dGELTM after irradiation. The blobs indicate the source dwell positions along the needles in the gel.
*3 Yonemura M, Tachibana H, Kojima T, Seki K, Nakaichi T, Rachi T, Tachibana R, Akimoto T. Three-dimensional source position verification in image-guided high-dose-rate brachytherapy using an XCT-based gel dosimeter. Me
vGEL and mGEL
vGEL and mGEL are polymer gel dosimeters for MR imaging. The gel dosimeters have higher sensitivity than VIPET dosimeters and MAGAT, respectively. After irradiation, images can be acquired using MR imaging, and dose distribution evaluation can be performed. We provide a one-stop service for gel fabrication, dose delivery, MR imaging, and analysis. Figure 4 and Figure 5 show examples of brachytherapy*4,5 and external radiotherapy*6, respectively.
Figure 4 Irradiated vGEL
Figure mGEL with a cubic container
*4 Tachibana H, Watanabe Y, Kurokawa S, Maeyama T, Hiroki T, Ikoma H, Hirashima H, Kojima H, Shiinoki T, Tanimoto Y, Shimizu H, Shishido H, Oka Y, Hirose TA, Kinjo M, Morozumi T, Kurooka M, Suzuki H, Saito T, Fujita K, Shirata R, Inada R, Yada R, Yamashita M, Kondo K, Hanada T, Takenaka T, Usui K, Okamoto H, Asakura H, Notake R, Kojima T, Kumazaki Y, Hatanaka S, Kikumura R, Nakajima M, Nakada R, Suzuki R, Mizuno H, Kawamura S, Nakamura M, Akimoto T: Multi-Institutional Study of End-to-End Dose Delivery Quality Assurance Testing for Image-Guided Brachytherapy Using a Gel Dosimeter. Brachytherapy. Vol.21, No. 6, 956-967, 2022. doi: 10.1016/j.brachy.2022.06.006
*5 Kurokawa S, Tachibana H: A real-world assessment of the robustness of gel dosimetry. Radiation Physics and Chemistry. Vol.210, 111009, 2023. doi:10.1016/j.radphyschem.2023.111009
*6 Tachibana H, Hoshino Y, Watanabe Y, Usui K, Mizukami S, Shibukawa S, Kodama T, Tachibana R. Quality assurance of magnetic resonance imaging for a polymer gel dosimeter using a 3D-printed phantom. Radiation Physics and Chemistry. Vol.226, 112196, 2025. doi: 10.1016/j.radphyschem.2024.1121