Iranian Journal of Nuclear Medicine

Iranian Journal of Nuclear Medicine

Accurate radiation dosimetry of [64Cu]Cu-DOTATOC using the Monte Carlo simulation

Articles in Press

Document Type : Original Article

Authors
Milad Peer-Firozjaei 1
Nasim Vahidfar 2
Mohsen Bakhshi Kashi 2
Peyman Sheikhzadeh 2, 3, 4
1 Student Research Committee, Babol University of Medical Sciences, Babol, Iran
2 Department of Nuclear Medicine, Imam Khomeini Hospital Complex, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
3 Department of Biomedical Physics and Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
4 Research Center for Nuclear Medicine, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran
10.22034/irjnm.2026.130326.1711
Abstract
Introduction: Copper-64 labeled DOTATOC ([64Cu]Cu-DOTATOC) is an emerging theranostic agent for neuroendocrine tumors (NETs), offering both high-resolution PET imaging and therapeutic potential. Accurate patient-specific dosimetry is critical to balance diagnostic benefits with radiation safety. This study aimed to perform voxel-based internal dosimetry of [64Cu]Cu-DOTATOC using Monte Carlo simulations, enabling precise three-dimensional absorbed dose estimation in normal organs and tumor nodules.
Methods: PET/CT images from patient imaged at two time points post-injection of [64Cu]Cu-DOTATOC were analyzed. Anatomical segmentation was performed, and time–activity curves were fitted with bi-exponential models. GATE v8.1 Monte Carlo simulations incorporating the full ⁶⁴Cu decay spectrum were employed to calculate mean absorbed dose rates (Gy/s) at the voxel level. Absorbed doses were derived by integrating residence times, and dose–volume histograms (DVHs) were generated for nodules and organs-at-risk.
Results: The highest absorbed doses per unit activity were observed in the colon (0.1063 mGy/MBq), gallbladder (0.0522 mGy/MBq), and liver (0.0475 mGy/MBq). Tumor nodules exhibited heterogeneous absorbed doses (0.0287 vs. 0.0083 mGy/MBq), influenced by surrounding organ activity. DVHs provided insight into dose heterogeneity, highlighting regions receiving elevated doses compared with organ means.
Conclusion: In this study, a voxel-level Monte Carlo–based dosimetry framework for [64Cu]Cu-DOTATOC PET/CT imaging was implemented and applied to a patient-specific dataset. The results demonstrate the capability of the proposed method to estimate spatial absorbed dose distribution and generate dose–volume histograms for organs and nodules. Future studies with multi-timepoint imaging and larger patient cohorts are warranted.
Keywords
Copper-64
DOTATOC
Voxel-based dosimetry
Monte Carlo simulation
PET/CT
Subjects
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Iranian Journal of Nuclear Medicine

Articles in Press, Accepted Manuscript
Available Online from 02 August 2026