Author: Payman Hejazi, Faraz Kalantari, Milad Peer-Firozjaei, Romina Pourhashem, Ehsan Tajikmansoury 👨🔬
Affiliation: Department of Radiobiology and Medical Physics, Babol University of Medical Sciences, Department of Radiation Oncology, University of Arkansas for Medical Sciences (UAMS), Department of Medical Physics, Semnan University of Medical Sciences, Department of Medical Physics, Semnan University of Medical Sciences, Semnan, Iran, Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine 🌍
Purpose:
Pretreatment biodistribution imaging play a crucial role in optimizing tumors and organ absorbed doses estimation in radionuclide therapy. Surrogating radionuclides for more efficient treatment planning is essential. This study evaluates the feasibility of estimating the 177Lu-DOTATATE dose distribution from 68Ga-DOTATATE imaging in preclinical mouse model. By eliminating the need for pre-treatment injections phase, this approach could potentially minimize the radiation dose during radionuclide therapy while maintaining treatment efficacy.
Methods:
Normal C57BL/6 mice underwent high-resolution µPET/CT and µSPECT/CT imaging following injection of 68Ga-DOTATATE and 177Lu-DOTATATE, respectively. Radionuclide dose concentration collected were also measured in key organs (spleen, kidneys, lungs, and liver) post-sacrifice to validate imaging results. Absorbed dose distributions for both radiopharmaceuticals were calculated using GATE Monte Carlo (MC) simulations based on CT-acquired anatomical data. Correlation analysis was performed to assess the relationship between the dose distributions of 68Ga-DOTATATE and 177Lu-DOTATATE.
Results:
Both imaging and organ dose analysis revealed a strong correlation between the absorbed dose distributions of 177Lu-DOTATATE and Ga-DOTATATE in major organs. GATE MC simulations demonstrated that the 68Ga-DOTATATE dose distribution patterns could reliably predict those of 177Lu-DOTATATE with minimal deviation (<10%) in high-uptake organs. These findings support the use of 68Ga-DOTATATE PET imaging as a non-invasive surrogate for dose planning.
Conclusion:
This study highlights the potential of 68Ga-DOTATATE imaging to predict 177Lu-DOTATATE dose distributions using GATE MC simulations. The proposed approach could eliminate the need for pre-treatment injections, thereby reducing unnecessary radiation exposure while maintaining effective radionuclide therapy planning.