Room: Davidson Ballroom A
Purpose: Energy modulated radiation therapy (EMRT) is a proposed radiotherapy technique that dynamically changes the photon spectra during treatment. Compared to the historical technique that blends the penetration capabilities of a 6MV x-ray spectrum with those of a higher energy spectrum (â‰¥10 MV), EMRT aims to include lower energy spectra (<6 MV) to provide steeper depth dose gradients and sharper penumbra. It is hypothesized that blending these spectra combinations, EMRT will provide more conformal treatment plans and a reduction in the total integral dose.
Methods: A prototype EMRT inverse planning algorithm has been implemented based on a proposed modification of a conventional radiotherapy device. Monte Carlo (MC) simulations were performed to generate profiles and depth dose distributions. For each beam angle, the optimization uses either the conventional 6MV photons or a lower energy spectra (e.g., 400 keV photons). The optimization uses nonnegative least square optimization to find an initial solution, then iteratively optimizes the plan based on DVH constraints.
Results: A head-to-head comparison was made between EMRT optimized plans and plans that only used 6MV IMRT. Examples were constructed using brain and whole breast treatments. These scenarios require: 1.) sharp dose gradients (e.g., tumors that abut the brainstem) and 2.) homogenous coverage to complex curvatures that are located nearby sensitive structures (e.g. left-sided whole breast). This study demonstrated that with the ability to incorporate lower energy spectra, EMRT plans will outperform a conventional 6MV plans.
Conclusion: EMRT provides control of beam penetration and penumbra via dynamic modulation of the energy spectra. This additional dimension to intensity modulated radiotherapy allows EMRT to deliver enhanced treatments when tight penumbra are required and when the total integral dose to a volume needs to be controlled. Ongoing work will demonstrate how to implement dynamic energy modulation using a clinical linear accelerator.
Funding Support, Disclosures, and Conflict of Interest: Research Agreement with Verus Research, Albuquerque NM
Not Applicable / None Entered.