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Novel Full 3D Water-Equivalent Dosimetry Technique Using a Single Light-Field Camera for Photons, Electrons and Ion-Beams Dosimetry


M Goulet

M Goulet1*, L Gingras1, S Beddar2, L Beaulieu3, L Archambault4, (1) CHU de Quebec, Quebec, QC, (2) MD Anderson Cancer Ctr., Houston, TX, (3) Centre Hospitalier Univ de Quebec, Quebec, QC, (4) CHUQ Pavillon Hotel-Dieu de Quebec, Quebec, QC

TU-C-108-2 Tuesday 10:30AM - 12:30PM Room: 108

Purpose: Using an array of micro-lenses coupled with its active sensor, a light-field camera samples the incoming optical photons in both the spatial and angular domain. This work presents the proof-of-concept and experimental validation of a 3D dosimeter based on the reconstruction of the light pattern emitted from a plastic scintillator volume and recorded using a light-field camera. Using a single, fixed camera device, this technology enables real-time, multi-plane experimental measurement of static and dynamic radiotherapy delivery.
Method: A Raytrix R5 light-field camera was used to image a 10x10x10cm³ EJ-260 plastic scintillator immersed in a water tank and irradiated with both square field and small MLC segments on a Clinac iX linear accelerator. The 3D light distribution emitted by the scintillator volume was reconstructed at a 5mm resolution in all dimensions by backprojecting the light collected by each pixel of the light-field camera using a total variation minimization iterative reconstruction algorithm.
Results: Signal contamination by Cerenkov emission was evaluated to less than 0.5% of the collected scintillation light for all field investigated, and as such Cerenkov light filtration was deemed unnecessary. Light-field acquisition rate of at least 1 frame per second was achieved by the camera at a 600MU/min dose rate. The absolute dose difference between the reconstructed 3D dose and the expected dose calculated using the treatment planning software Pinnacle3 was on average below 3% for square fields and 5% for MLC segments in the high dose, low gradient region of each acquired field.
Conclusions: Millimeter resolution dosimetry over an entire 3D volume is achievable in real-time using a single light-field camera. Because no moving parts are required in the dosimeter, the incident dose distribution can be acquired as a function of time, thus enabling the validation of static and dynamic radiation delivery with photons, electrons and ions.

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