Optical-CT 3D Dosimetry Using Fresnel Lenses with Minimal Refractive-Index Matching Fluid.

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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.





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Bache, Steven, Javian Malcolm, John Adamovics and Mark Oldham (2016). Optical-CT 3D Dosimetry Using Fresnel Lenses with Minimal Refractive-Index Matching Fluid. PLoS One, 11(3). p. e0152606. 10.1371/journal.pone.0152606 Retrieved from https://hdl.handle.net/10161/12017.

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Steven Bache

Assistant Consulting Professor in the Department of Radiology

Steve is an Imaging Physicist specializing in Computed Tomography in the Clinical Imaging Physics Group. His primary clinical role is in CT protocol design, image quality and radiation dosimetry troubleshooting, with a commitment to radiology research design and implementation. His clinical duties also include radiography, nuclear medicine, mammography, and fluoroscopy modalities.


Mark Oldham

Professor of Radiation Oncology

Dr Oldham is the Director of the Duke Medical Physics MS/PhD Graduate Program, and Professor in the Department of Radiation Oncology, with a secondary appointment in the Physics Department at Duke. 

Main current research interests include: FLASH radiation therapy, exploring FLASH mechanisms utilizing the Duke High Intensity Gamma Source (HIGS), a nuclear research accelerator on the Duke campus.  Recent work selected for best in Physics at the annual AAPM meeting.  Radiation and Immunotherapy utilizing mini-grids. Radiation Therapy Enhanced by Cherenkov photo-Activation (RECA) and Comprehensive 3D dosimetry.

Dr Oldham has patented and published on several novel radiation treatment techniques (including XPACT and RECA - Radiotherapy Enhanced by Cherenkov photo-Activation) with exiting potential to invoke systemic anti-cancer immunogenic response.  A phase I clinical trial of XPACT is underway.  The lab has pioneered novel pre-clinical treatment capabilities including mini-beam grids, and ultra-high-resolution IMRT.  The lab has also developed novel optical imaging techniques for high-resolution 3D imaging of vascular networks and fluorescent gene expression in un-sectioned tissue samples.

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