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Groundbreaking 2D and 3D Dosimetry Techniques Using Scintillating Fibers and Tomographic Reconstruction

M Goulet

M Goulet*, L Archambault, L Beaulieu, L Gingras, Centre Hospitalier Univ de Quebec (CHUQ), Quebec, QC

TU-A-BRB-1 Tuesday 8:00:00 AM - 9:55:00 AM Room: Ballroom B

Purpose: To present the novel concept of tomodosimetry, i.e. the tomographic reconstruction of the dose projections obtained using long scintillating fibers, and its application to 2D and 3D dosimetry.

Methods: 2D configuration: 50 scintillating fibers were aligned on a 20cm diameter disk inside a 30cm diameter rotating masonite phantom. 18 dose projections (8 MU each) were measured for each radiation field over a 180 degrees rotation of the phantom. 3D configuration: 128 long scintillating fibers were simulated inside a 20cm diameter, 20cm long cylindrical water-equivalent phantom. The fibers were placed at various angles on the surface of two cylindrical regions of radius 7.5 and 3.75cm. Using the predicted dose from Pinnacle3, we simulated a 360 degrees rotation of the phantom along its principal axis, collecting the scintillation light from the fibers at each 5 degrees. Both prototypes: the dose in each scintillating fiber plane was reconstructed using a total variation minimization reconstruction iterative algorithm at a resolution of 1x1mm², and was interpolated in the 3D volume between in each cylindrical plane in the 3D prototype.

Results: Absolute measured dose differences in the 2D configuration were on average below 1% in the high dose low gradient region of each field. Absolute doses differences calculated inside the inner cylindrical region were on average of 0.5% and 1.3% of the isocenter dose for a 10x10cm² field and an IMRT segment, respectively. 3%/3mm gamma tests conducted in both configurations in the isocenter plane achieved a success rate of more than 99% of the dose pixels for the region over 50% of the maximum dose.

Conclusions: This work demonstrates the potential of scintillating fiber based tomographic 2D and 3D dosimeters. This methodology allows for millimeter resolution dosimetry in a whole 2D plane or 3D volumes in real-time using only a limited number of detectors.

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