Recent Trends in Internal Exposure Dose Calculation Methods in Nuclear Medicine Therapy—Comprehensive Review of Monte Carlo, MIRD, Imaging, and Software—

Hiroshi Watabe; 渡部浩司; Tatsuhiko Sato; 佐藤達彦; Tetsuya Sakashita; 坂下哲哉; Naoyuki Ukon; 右近直之; Miho Shidahara; 志田原美保

doi:10.3769/radioisotopes.750204

核医学治療における内部被ばく線量計算法の最近の動向—モンテカルロ法・MIRD法・イメージング・ソフトウェアの包括的レビュー—Recent Trends in Internal Exposure Dose Calculation Methods in Nuclear Medicine Therapy—Comprehensive Review of Monte Carlo, MIRD, Imaging, and Software—

渡部浩司¹，佐藤達彦^2,3，坂下哲哉⁴，右近直之⁵，志田原美保⁶Hiroshi Watabe¹, Tatsuhiko Sato^2,3, Tetsuya Sakashita⁴, Naoyuki Ukon⁵, Miho Shidahara⁶

¹ 東北大学先端量子ビーム科学研究センターResearch Center for Accelerator and Radioisotope Science, Tohoku University

² 日本原子力研究開発機構Japan Atomic Energy Agency

³ 大阪大学The University of Osaka

⁴ 量子科学技術研究開発機構National Institutes for Quantum Science and Technology (QST)

⁵ 福島県立医科大学先端臨床研究センターAdvanced Clinical Research Center, Fukushima Medical University

⁶ 東北大学大学院工学研究科Graduate School of Engineering, Tohoku University

発行日：2026年7月15日Published: July 15, 2026

セラノスティクスの進展に伴い，核医学治療における内部被ばく線量評価の重要性が世界的に高まっている。本稿では，この分野の最近の動向を統合し概説する。具体的には，高精度な個別線量評価を可能にするモンテカルロ法（RT-PHITS），MIRD法の基礎と最新ツール（MIRDcalc），計算精度の鍵となる定量画像およびTime-Integrated Activity（TIA）の取得，そして臨床実装が進む線量計算ソフトウェアの現状について解説する。

Internal exposure dose estimation in nuclear medicine has a long history, but it is currently attracting unprecedented attention due to the rapid global development of new radiopharmaceuticals for theranostics. This paper integrates recent trends in internal dosimetry methods in Japan and globally. We review the fundamental principles and latest developments in four key areas: (1) Monte Carlo methods, focusing on the RT-PHITS system for precise individual dosimetry; (2) the MIRD method, detailing its basic concepts and the new “MIRDcalc” software; (3) quantitative imaging and Time-Integrated Activity (TIA) acquisition essential for accurate dosimetry; and (4) the current status of commercial dosimetry software supporting clinical workflows. This comprehensive review aims to provide a perspective on the new era of high-precision internal dosimetry.

Key words: internal dosimetry; nuclear medicine therapy; Monte Carlo; MIRD; imaging; software

RADIOISOTOPES

資料Materials (Data)