Annual Report 2024
Division of Functional Imaging
Anri Inaki, Mitsuyoshi Yoshimoto, Chikayo Ide, Hirofumi Fujii, Tadayuki Takahashi, Sakiko Yasuda
Introduction
We conduct research on nuclear medicine diagnostics, therapies, and the development of radiotheranostic agents that combine these approaches, as well as imaging technologies.
Research Activities
We have advanced non-clinical research using the alpha-emitting radionuclides At-211 and Ac-225. In experimental cancer treatments employing antibodies labeled with At-211, we confirmed that the therapeutic efficacy of At-211-labeled antibody treatment improves by using radical scavengers to prevent antibody degradation. Additionally, we experimentally demonstrated that polyethylene filter paper, previously used in unsealed radionuclide experiments to prevent environmental contamination, is ineffective for At-211, and we raised awareness among users regarding this issue.
In experimental cancer treatments using Ac-225-labeled peptides, we confirmed that high quality Ac-225 is required to achieve sufficient therapeutic efficacy. Meanwhile, in collaboration with industry partners, we developed a technique for producing Ac-225 with minimal isotopic contamination using electron beams from accelerators.
To facilitate practical dose assessment for alpha radiation therapy, we also explored high-performance semiconductor gamma cameras for in vivo imaging of alpha-emitting radionuclides.
Furthermore, we created materials that clearly explain daily life precautions for patients undergoing nuclear medicine diagnostics and therapies. To address the shortage of nuclear medicine therapy rooms for existing I-131 and Lu-177 treatments, we conducted research on efficient radionuclide containment methods.
Clinical Trials
We managed clinical research on radiotheranostics using a CA9-targeting ligand (peptide formulation) for renal clear cell carcinoma. We also planned clinical research on radiotheranostics using a CLDN18.2-targeting ligand (peptide formulation) for gastric carcinoma, which is scheduled to be conducted next fiscal year.
Education
We provided research guidance, including animal experiments, to graduate students specializing in medicine, radiological technology, and science and engineering. Additionally, we offered guidance to physicians and students from other universities.
Future Prospects
Since nearly 100% of the radioactive isotopes used in nuclear medicine diagnostics and therapies are imported, we are advancing technical evaluations for domestic production. In parallel, we aim to develop devices that contribute to the broader adoption of nuclear medicine therapies.
List of papers published in 2024
Journal
1. Sagara H, Inoue K, Mano C, Kajiwara H, Nagai Y, Fujii H, Inaki A. Usefulness of a new anthropomorphic phantom simulating the chest and abdomen regions in PET tests. Annals of nuclear medicine, 39:303-312, 2025
2. Katsuragawa M, Yagishita A, Takeda S, Minami T, Ohnuki K, Fujii H, Takahashi T. CdTe XG-Cam: A new high-resolution x-ray and gamma-ray camera for studies of the pharmacokinetics of radiopharmaceuticals in small animals. Medical physics, 51:5308-5320, 2024
3. Yoshimoto M, Hayakawa T, Yamaguchi M, Kimura S, Fujii H. αvβ3 integrin-targeted magnetic resonance imaging in a pancreatic cancer mouse model using RGD-modified liposomes encapsulated with Fe-deferoxamine. PloS one, 19:e0310984, 2024
4. Yoshimoto M, Washiyama K, Ohnuki K, Doi A, Inokuchi M, Kojima M, Miller BW, Yoshii Y, Inaki A, Fujii H. Long-Term Therapeutic Effects of (225)Ac-DOTA-E[c(RGDfK)](2) Induced by Radiosensitization via G2/M Arrest in Pancreatic Ductal Adenocarcinoma. Pharmaceutics, 17:9, 2024