title: Optical-CT 3D Dosimetry Using Fresnel Lenses with Minimal Refractive-Index Matching Fluid.
abstract: Telecentric optical computed tomography (optical-CT) is a state-of-the-art method for visualizing and quantifying 3-dimensional dose distributions in radiochromic dosimeters. In this work a prototype telecentric system (DFOS-Duke Fresnel Optical-CT Scanner) is evaluated which incorporates two substantial design changes: the use of Fresnel lenses (reducing lens costs from $10-30K t0 $1-3K) and the use of a 'solid tank' (which reduces noise, and the volume of refractively matched fluid from 1 ltr to 10 cc). The efficacy of DFOS was evaluated by direct comparison against commissioned scanners in our lab. Measured dose distributions from all systems were compared against the predicted dose distributions from a commissioned treatment planning system (TPS). Three treatment plans were investigated including a simple four-field box treatment, a multiple small field delivery, and a complex IMRT treatment. Dosimeters were imaged within 2 h post irradiation, using consistent scanning techniques (360 projections acquired at 1 degree intervals, reconstruction at 2mm). DFOS efficacy was evaluated through inspection of dose line-profiles, and 2D and 3D dose and gamma maps. DFOS/TPS gamma pass rates with 3%/3mm dose difference/distance-to-agreement criteria ranged from 89.3% to 92.2%, compared to from 95.6% to 99.0% obtained with the commissioned system. The 3D gamma pass rate between the commissioned system and DFOS was 98.2%. The typical noise rates in DFOS reconstructions were up to 3%, compared to under 2% for the commissioned system. In conclusion, while the introduction of a solid tank proved advantageous with regards to cost and convenience, further work is required to improve the image quality and dose reconstruction accuracy of the new DFOS optical-CT system.
authors.affiliation: Duke University Medical Physics Graduate Program, Durham, NC, 27705, United States of America.
authors.forename: Steven
authors.initials: S
authors.lastname: Bache
authors.affiliation: Duke University Medical Physics Graduate Program, Durham, NC, 27705, United States of America.
authors.forename: Javian
authors.initials: J
authors.lastname: Malcolm
authors.affiliation: Department of Chemistry, Rider University, Lawrenceville, NJ, 08648, United States of America.
authors.forename: John
authors.initials: J
authors.lastname: Adamovics
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, NC, 27710, United States of America.
authors.forename: Mark
authors.initials: M
authors.lastname: Oldham
mesh_terms: D016477:Artifacts; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D021621:Imaging, Three-Dimensional; D007909:Lenses; D011874:Radiometry; D012031:Refractometry; D012996:Solutions; D014057:Tomography, X-Ray Computed
chemical_list: D012996:Solutions