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Updated: May 11, 2026
A Whole Body Dosimetry Protocol for Peptide-Receptor Radionuclide Therapy (PRRT): 2D Planar Image and Hybrid 2D+3D SPECT/CT Image Methods
Published on: April 24, 2020
Multiple vertebrae improves precision in image-based bone marrow absorbed dose estimation in [177Lu]Lu-DOTATATE
Katja Smits1, Frida Westerbergh2, Jens Hemmingsson2
1Department of Medical Radiation Sciences, Institute of Clinical Sciences, Sahlgrenska Academy at University of Gothenburg, Gula Stråket 2B, 413 45, Gothenburg, Sweden. katja.smits@gu.se.
Background:
The bone marrow is a critical dose limiting organ in patients receiving radionuclide therapy, but image-based bone marrow dosimetry is not routinely performed in clinical practice. High noise levels and the limited number of vertebral cavities used in bone marrow absorbed dose calculations make absorbed dose estimates susceptible to large uncertainties. This study explores the effects of the number of included vertebrae, partial volume effects, and reconstruction parameters on image-based bone marrow absorbed dose calculations. We included sixteen patients with advanced neuroendocrine tumors treated with [177Lu]Lu-DOTATATE. Bone marrow absorbed dose estimates and their precision were analyzed based on the number of vertebrae included in the calculation. Additional evaluations were performed using both measured (Lung-Spine phantom with spherical inserts) and simulated (digital XCAT phantom) SPECT data, with noise levels matching patients' bone marrow.
Results:
Increasing the number of vertebrae from one to six improved precision in absorbed doses, reducing the coefficient of variation (COV) from 34 to 6.2%. Only minor differences (0.1%) in bone marrow absorbed dose were observed when adjusting reconstruction parameters from 1 subset, 60 iterations, to 12 subsets, 5 iterations. In the Lung-Spine phantom, smaller volumes (4 mL) were more sensitive to noise than larger volumes (16 mL), with COVs of 36% and 17%, respectively, at 60 updates. In the XCAT phantom, a decrease in recovery was observed in vertebrae near high-uptake regions (L5: 0.63, L1: 0.29), at 60 updates at the highest noise level.
Conclusion:
Including multiple lesion-free vertebrae enhances precision in image-based bone marrow absorbed dose calculations. Nevertheless, careful selection of vertebrae is important, as closely located high-uptake areas can bias absorbed dose estimates. Applying partial volume correction could mitigate spill-out effects, further improving accuracy. Additionally, the minimal differences between reconstruction parameters suggest that bone marrow absorbed dose estimates remain stable across subset configurations.
