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Updated: May 11, 2026
Differentiating Functional Roles of Gene Expression from Immune and Non-immune Cells in Mouse Colitis by Bone Marrow Transplantation
Published on: October 1, 2012
Small-scale bone marrow dosimetry study for 225Ac
Stephen Tronchin1, Jake Forster1, Kevin Hickson2
1Department of Physics, The University of Adelaide, Adelaide, SA 5005, Australia; Medical Physics & Radiation Safety, South Australia Medical Imaging, Adelaide, SA 5000, Australia.
Background:
Targeted alpha therapy (TAT) with 225Ac-labelled radiopharmaceuticals is a growing therapeutic option for the treatment of various cancers. Due to the short range of alpha particles in tissue, the absorbed dose can be non-uniform on a microscopic scale. Therefore, understanding bone marrow toxicity in TAT requires small-scale dosimetry.
Method:
We developed a voxelised trabecular bone model, based off µCT slices, with a voxel size of (37 × 37 × 37) µm3. A small-scale dosimetry study was performed to assess the marrow toxicity from uptake of unlabelled 225Ac in the trabecular bone. The Particle and Heavy Ion Transport Code System (PHITS) was used to simulate the decays and score the absorbed dose to each voxel from the alpha and beta emissions of the 225Ac decay chain.
Results:
For the alpha decays on the trabecular surface, 43 % of the marrow voxels were irradiated. The maximum voxel dose for the marrow was 1.1 Gy, and the mean non-zero voxel dose was 0.2 Gy (σ = 0.2 Gy). The beta-emissions from the trabecular surface irradiated all the marrow voxels, with a mean voxel dose of 3.9 mGy (σ = 1.7 mGy).
Conclusion:
Our model demonstrated a non-uniform absorbed dose profile to the red marrow due to alpha emissions on the trabecular bone surface. The alpha emissions irradiated less than half of the marrow voxels,while the beta emissions irradiated all marrow voxels. This could potentially suggest a lower marrow toxicity from alpha-emitters compared to beta-emitters when skeletal metastases are present.
