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Session: Radiopharmaceutical Imaging and Dosimetry [Return to Session]

Investigating Spatiotemporal Distribution of Chain Alpha Emitters in Intra- and Inter- Cellular Spaces for Targeted Radiotherapy

R Khan1*, J Grafe2, (1) Howard University, Howard University Hospital, Washington, DC, (2) Ryerson University, Toronto, ON, Canada


MO-E115-IePD-F5-6 (Monday, 7/11/2022) 1:15 PM - 1:45 PM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 5

Purpose: Molecular targeted radionuclide therapy when employed in selective patient population can provide disease control at acceptable normal tissue toxicity, and has a promise of better outcomes especially for metastatic and diffused disease. The temporal distribution in and around the targeted and normal tissue cells is critically important both for the treatment outcome and toxicity to healthy cells. Radioactive decay of two chain alpha emitters in a homogeneous medium are simulated in this preliminary work.

Methods: Chain alpha emitters used in radiopharmaceutical treatment such as Actinium 225, and Radium 223 were modelled in the center of a homogenous volume (2cm×2cm×2cm) of water via Geant4 Monte Carlo simulation. To evaluate the energy produced by each of the radioactive series, the interactions probabilities of all emitted particles and recoiling nuclides in the medium were overridden to zero. Energy, momentum balance and various secondary radiation such as betas, alphas, and gammas were scored in the preliminary study employing evaluated nuclear structure datafile (ENSDF).

Results: The chain alpha emission leads to a cumulative kinetic energy up to 27.7 MeV for ²²⁵Ac and 26.3 MeV for ²²³Ra per decay chain. The gammas range from 0.1 -1.8 MeV, and 0.1-1.3 MeV; alphas 5–8.4 MeV, and 5–7.4 MeV; recoils 100-170 keV, and 100–140 keV respectively for ²²⁵Ac, and ²²³Ra. In addition to alphas, daughter recoils and their transport in the medium constitute damage. At this point, all possible decay states of radionuclides were comprehensively included in our simulations.

Conclusion: In this study we validated the release of energy as alphas, light charged particles, gammas, and nuclear recoils because of series decay of two popular alpha sources ²²⁵Ac and ²²³Ra emitters as discrete lines. The next step will be to evaluate micro distribution of energy at various locations of interest around the target medium incorporating temporal effects.


Not Applicable / None Entered.


TH- Radiobiology(RBio)/Biology(Bio): Bio- tissue and microenvironment

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