Purpose: A project is underway to develop a new generation cobalt device capable of delivering IMRT treatments. This has the potential to positively impact the global coverage gap in radiotherapy. One challenge of cobalt beams, however, is the wider penumbra. In the current study, we investigate the effects of Co-source sizes on complex IMRT plans to inform the development of this new device.
Methods: Monte Carlo (MC) simulation was used to generate profile and PDD data for different Co-source sizes which were then used to commission the respective beams in the treatment planning system (TPS). We generated head-and-neck treatment plans and calculated mean dose, max dose, and dose-volume statistics of organs at risk for plans from each source size.
Results: Plans using a smaller source showed improved plan quality in terms of OAR sparing while still maintaining satisfactory PTV coverage, including lower dose to the spinal cord (Dmax < 45 Gy). In most cases, it was possible to achieve better dose sparing of the parotids (Dmean < 26 Gy) and the submandibular glands (Dmean < 26 Gy).
Conclusion: Smaller cobalt source size results in improved dose sparing of OARs. These data will inform source design in the novel Co-IMRT device under development. In the new design, the lower output from a smaller source would be compensated by employing multiple sources concurrently which will also improve treatment times and machine throughput in clinics at resource-limited settings.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by the National Cancer Institute of the National Institutes of Health under Award Number 5UH3 CA211310-04
Co-60, Compensators, Intensity Modulation
Not Applicable / None Entered.