Reconstruction of radiotherapy dose fields shaped with a multileaf collimator from six projections

Odran Pivot (1) , Laurent Desbat (1) , Simon Rit (2) , Rolf Clackdoyle (1) , Patrick Pittet (3)

1 TIMC-IMAG - Techniques de l'Ingénierie Médicale et de la Complexité - Informatique, Mathématiques et Applications Grenoble - UMR 5525
2 Imagerie Tomographique et Radiothérapie
3 INL - Institut des Nanotechnologies de Lyon

Quality assurance of small dose fields shaped with a multileaf collimator is crucial in x-ray radiotherapy. Tissue-equivalent scintillating fibers (SciFi) can measure a sinogram of the dose field at the detector plane sampled with a few angles and open up the possibility of real-time quality assurance. We investigate the use of such detectors for estimating dose fields obtained with multileaf collimators (MLC). We propose a forward model of the tomographic projection based on geometrical parameters of the MLC and the beam dose. A least squares minimization is then used to identify these parameters. We validate our approach on real data acquired with a prototype SciFi detector measuring six projections of a field generated with a 6 MeV linear accelerator and shaped by nine pairs of leaves. We observe a good fit with the reference gafchromic film.

Domaines: Instrumentations et Détecteurs [physics.ins-det]; Traitement du signal et de l'image [eess.SP]

Odran Pivot, Laurent Desbat, Simon Rit, Rolf Clackdoyle, Patrick Pittet. Reconstruction of radiotherapy dose fields shaped with a multileaf collimator from six projections. 2020 IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC, Oct 2020, virtual, United States. ⟨hal-03145322⟩