Several (online) adaptive radiotherapy techniques have been developed to maximize healthy tissue sparing in the presence of interfractional or intrafractional motion during SBRT. Adaptive radiotherapy results in increased treatment complexity and may be susceptible to motion-delivery interplay. To guarantee the quality and safety of these treatments, motion phantoms with integrated time-resolved dosimeters are required.

Currently, available phantoms and dosimeters are often not suitable to validate adaptive treatments on an MR-linac due to a lack of MR-compatibility or a motion component. An alternative dosimeter is an MR-compatible and time-resolved plastic scintillation dosimeter (PSD). The PSD’s scintillator emits an optical photon flux proportional to the received energy when it is excited by ionizing radiation.

However, a single PSD would provide insufficient volume coverage to validate an adaptive workflow. To improve this coverage, we developed the novel MRI⁴ᴰ scintillator cassette together with IBA QUASAR (London, ON) and Medscint (Quebec City QC, Canada). This device combines radiochromic film with four PSDs. Furthermore, it seamlessly integrates with the IBA QUASAR MRI⁴ᴰ Motion Phantom, providing simultaneous spatial, temporal, and motion-included dosimetry.

In this webinar, we will demonstrate the suitability of the HYPERSCINT RP-200 scintillation dosimetry research platform in a 1.5 T MR-linac. Then we will also show the performance of the new commercially available MRI⁴ᴰ scintillator cassette.

Prescilla Uijtewaal is a final-year PhD candidate at the University Medical Center Utrecht (UMCU) in the Netherlands under the supervision of Dr Martin Fast. She obtained her master’s degree in biomedical engineering at the Technical University Delft. In her current work, Prescilla investigates the feasibility and dosimetric benefits of MR-guided MLC tracking on the MR-linac. Additionally, she focuses on the validation of online adaptive radiotherapy workflows by developing and testing a PSD-based QA device. Her work is published in renowned, peer-reviewed, international journals. She also presented on MR-guided MLC tracking and dosimetry-focussed work at recent ESTRO and AAPM meetings.