Author: Niels Bassler, Jonathan Bortfeldt, Davide Boscaini, Francesco Evangelista, Guyue Hu, Ze Huang, Margarita Kozak, Julie Lascaud, Giulio Lovatti, Eero Lönnqvist, Jasper Nijkamp, Munetaka Nitta, Prasannakumar Palaniappan, Katia Parodi, Marco Pinto, Per R. Poulsen, Marco Riboldi, Babak Sharifi, Brita Singers Sørensen, Peter Thirolf 👨🔬
Affiliation: Department of Medical Physics, Ludwig-Maximilians-Universität München (LMU Munich), Ludwig-Maximilians Universität, Danish Centre for Particle Therapy, Aarhus University Hospital, Department of Medical Physics, Ludwig-Maximilians-Universität (LMU) München, Department of Experimental Clinical Oncology, Aarhus University, Department of Oncology, Aarhus University Hospital 🌍
Purpose: To perform the first in vivo application of a novel small animal radiation research platform combining on-board image-guidance with multi-field intensity modulated spot scanning delivery [1] in a pilot normal tissue toxicity study.
Methods: A cohort of 9 mice underwent pre-treatment imaging at an off-site research spectral cone-beam computed tomography (CBCT) system [2] in the same upright position as for later treatment. Plans were calculated with a research version of µRayStation using as input validated phase spaces of the focused horizontal beams of ~1 mm spot size (sigma) and 20-50 MeV energy, produced by the platform from a 70 MeV clinical beam. Conversion of CT numbers to density and stopping power was based on a calibration phantom and previously evaluated mice images, complemented by multiple on-board proton radiographies acquired just before treatment for validation of the tissue water equivalent thickness. The proton radiographies were also used for setup via 2D-3D co-registration to the CBCT. Median doses (D50%) from 30 to 50 Gy(RBE) were delivered in one or two fields to different volumes/locations of the lungs spot-by-spot, using remote-controlled stages for beam-target shifts. During irradiation in-beam positron-emission-tomography was used to compare the updated (every 60 s) reconstructed images with predictions from β+-emitter maps calculated by µRayStation. Follow-up spectral CBCT images for toxicity assessment are still ongoing.
Results: On-board imaging, position correction and multi-field spot scanning irradiation could be done for each anesthetized mouse within the set limit of ~60 min. This presentation will review the main components of the workflow and prior in-phantom validation.
Conclusion: While the follow-up study is still ongoing, we could show experimentally that the SIRMIO platform can be safely used for image-guided proton spot scanning irradiation, opening new prospects in precision preclinical research.
[1] Parodi et al, Acta Oncol 2019
[2] Bal et al, Tomography 2024