INSCAPE · Innovating the Next-generation Specialized CBCT for Adaptive Proton thErapy

Proton radiotherapy has better healthy tissue sparing than conventional photon therapy due to protons' peaked depth-dose profile. However, the sensitivity of protons to anatomical and setup variations can result in delivery errors, potentially leading to tumor underdosage or healthy tissue overdosage. Online adaptive proton therapy (OAPT) improves delivery accuracy by daily adapting the treatment plan based on newly acquired images. Despite the well-established advantages and recent scientific advances through the H2020 MSCA International Training Network RAPTOR, OAPT has not yet become clinical practice, primarily because the quality of current onboard imaging is insufficient for proton dose calculation.This project aims to design the next-generation onboard cone-beam CT (CBCT) for proton therapy gantries to achieve sufficient image quality for proton dose calculation. Hardware upgrades for a current CBCT will be tested in silico by developing a Monte-Carlo (MC) simulation platform in Gate. First, the current CBCT will be modeled in collaboration with a manufacturer and the model will be validated experimentally. Then, an image reconstruction software will be implemented, using open-source libraries, which can be extended to support the hardware upgrades (e.g. reconstruction for dual-energy). Lastly, hardware upgrades will be simulated in the MC platform, including dual-energy CBCT, dynamic collimation, photon counting detectors and systems speeding up CBCT rotation to avoid motion artifacts. All upgrades will be evaluated with various virtual phantoms and evaluation will be performed in image space and dosimetrically.The project will show the dosimetric impact of these CBCT hardware upgrades, allowing the proton therapy community to understand the changes required to make on-board CBCT ready for online adaptation. Overcoming this critical step will enable widespread clinical adoption of OAPT, enhancing the clinical benefits of proton therapy.