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Quantitative Imaging of 177Lu in the Presence of 90Y for Peptide Receptor Radionuclide Therapy: A Simulation Study

C Miller1*, A Rahmim12, C Uribe-munoz34, A Celler4, (1) Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, CA (2) Department of Integrative Oncology, BC Cancer Research Centre, Vancouver, BC, CA (3) PET Functional Imaging, BC Cancer Research Centre, Vancouver BC, CA (4) Department of Radiology, University of British Columbia, Vancouver, BC, CA


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Dual-isotope peptide receptor radionuclide therapy using DOTATATE labeled with ¹77Lu and ?°Y is a promising treatment for neuroendocrine tumours. In order to not exceed dose limits to critical organs while optimizing tumour control, personalized dosimetry should be performed. If identical biodistributions of ¹77Lu- and ?°Y-DOTATATE are assumed, dose estimates for ¹77Lu and ?°Y can be done using ¹77Lu SPECT imaging. However, Bremsstrahlung photons created by ?°Y might cloud the ¹77Lu distribution, posing a challenge for activity quantification. The aim of this work is to determine if dosimetry based on quantitative imaging of ¹77Lu in the presence of ?°Y is possible.

Methods: Monte Carlo GATE simulations of spheres filled with ¹77Lu, ?°Y, or both placed in a cylindrical water phantom were created. Images were generated with a simulated Siemens SPECT camera. Eighteen concentrations of ¹77Lu and/or ?°Y placed in the spheres and two background activities for each concentration were simulated. Two different scatter window widths for triple energy window scatter correction (TEW-SC) were investigated. The quantification error and contrast to noise ratios (CNRs) were determined for every configuration.

Results: Quantification error of ¹77Lu remained within ±6% for all configurations and concentrations of ¹77Lu and ?°Y. The presence of ?°Y increased the accuracy of quantification due to the reduction of errors associated with TEW-SC. Better accuracy was achieved with a narrower scatter window width. The presence of ?°Y did not impact the CNRs in any configuration, and all CNRs were well above the threshold of 5 suggested by the Rose Criterion.

Conclusion: Our study indicates that quantitative imaging of ¹77Lu in the presence of ?°Y may provide more accurate results than imaging ¹77Lu alone. The presence of ?°Y also does not negatively impact image noise. In summary, ?°Y does not negatively affect quantitative imaging and dosimetry in dual-isotope PRRT.

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Quantitative Imaging, SPECT, Dosimetry


IM- SPECT : Monte Carlo Modeling

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