title: Novel, full 3D scintillation dosimetry using a static plenoptic camera.
abstract: OBJECTIVE
  Patient-specific quality assurance (QA) of dynamic radiotherapy delivery would gain from being performed using a 3D dosimeter. However, 3D dosimeters, such as gels, have many disadvantages limiting to quality assurance, such as tedious read-out procedures and poor reproducibility. The purpose of this work is to develop and validate a novel type of high resolution 3D dosimeter based on the real-time light acquisition of a plastic scintillator volume using a plenoptic camera. This dosimeter would allow for the QA of dynamic radiation therapy techniques such as intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT).
  
  
  METHODS
  A Raytrix R5 plenoptic camera was used to image a 10 × 10 × 10 cm(3) EJ-260 plastic scintillator embedded inside an acrylic phantom at a rate of one acquisition per second. The scintillator volume was irradiated with both an IMRT and VMAT treatment plan on a Clinac iX linear accelerator. The 3D light distribution emitted by the scintillator volume was reconstructed at a 2 mm resolution in all dimensions by back-projecting the light collected by each pixel of the light-field camera using an iterative reconstruction algorithm. The latter was constrained by a beam's eye view projection of the incident dose acquired using the portal imager integrated with the linac and by physical consideration of the dose behavior as a function of depth in the phantom.
  
  
  RESULTS
  The absolute dose difference between the reconstructed 3D dose and the expected dose calculated using the treatment planning software Pinnacle(3) was on average below 1.5% of the maximum dose for both integrated IMRT and VMAT deliveries, and below 3% for each individual IMRT incidences. Dose agreement between the reconstructed 3D dose and a radiochromic film acquisition in the same experimental phantom was on average within 2.1% and 1.2% of the maximum recorded dose for the IMRT and VMAT delivery, respectively.
  
  
  CONCLUSIONS
  Using plenoptic camera technology, the authors were able to perform millimeter resolution, water-equivalent dosimetry of an IMRT and VMAT plan over a whole 3D volume. Since 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 heavier ions.
authors.affiliation: Département de physique, de génie physique et d'optique and Centre de recherche sur le cancer, Université Laval, Québec, Québec G1V 0A6, Canada and Département de radio-oncologie and CRCHU de Québec, CHU de Québec, 11 Côte du Palais, Québec, Québec G1R 2J6, Canada.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Goulet
authors.affiliation: Département de physique, de génie physique et d'optique and Centre de recherche sur le cancer, Université Laval, Québec, Québec G1V 0A6, Canada; Département de radio-oncologie and CRCHU de Québec, CHU de Québec, 11 Côte du Palais, Québec, Québec G1R 2J6, Canada; and Department of Physics, McGill University, Montréal, Québec H3A 0G4, Canada.
authors.forename: Madison
authors.initials: M
authors.lastname: Rilling
authors.affiliation: Département de physique, de génie physique et d'optique and Centre de recherche sur le cancer, Université Laval, Québec, Québec G1V 0A6, Canada and Département de radio-oncologie and CRCHU de Québec, CHU de Québec, 11 Côte du Palais, Québec, Québec G1R 2J6, Canada.
authors.forename: Luc
authors.initials: L
authors.lastname: Gingras
authors.affiliation: Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 94, Houston, Texas 77030.
authors.forename: Sam
authors.initials: S
authors.lastname: Beddar
authors.affiliation: Département de physique, de génie physique et d'optique and Centre de recherche sur le cancer, Université Laval, Québec, Québec G1V 0A6, Canada and Département de radio-oncologie and CRCHU de Québec, CHU de Québec, 11 Côte du Palais, Québec, Québec G1R 2J6, Canada.
authors.forename: Luc
authors.initials: L
authors.lastname: Beaulieu
authors.affiliation: Département de physique, de génie physique et d'optique and Centre de recherche sur le cancer, Université Laval, Québec, Québec G1V 0A6, Canada and Département de radio-oncologie and CRCHU de Québec, CHU de Québec, 11 Côte du Palais, Québec, Québec G1R 2J6, Canada.
authors.forename: Louis
authors.initials: L
authors.lastname: Archambault
mesh_terms: D000465:Algorithms; D001932:Brain Neoplasms / Q000532:radiotherapy; D004867:Equipment Design; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation* / Q000379:methods*; D019047:Phantoms, Imaging; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation / Q000379:methods; D012984:Software
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