Investigation of a low-cost optical-CT system with minimal refractive index-matching fluid

8th International Conference on 3D Radiation Dosimetry

Bache, S.^1 ; Malcolm, J.^1 ; Adamovics, J.^2 ; Oldham, M.^3

Duke University Medical Physics Graduate Program, 2424 Erwin Rd, Durham

NC

27705, United States^1

Department of Chemistry and Biology, Rider University, Lawrenceville

NJ

08648, United States^2

Department of Radiation Oncology Physics, Duke University Medical Center, Durham

NC

27710, United States^3

关键词: Differential absorption;    Dose distributions;    Gold standards;    Optical computed tomography;    Parallel beam geometry;    Projection image;    Refractive index matching;    Treatment planning;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/573/1/012052/pdf
DOI  :  10.1088/1742-6596/573/1/012052

来源: IOP

【 摘 要 】

Optical computed tomography (optical-CT) is a method for visualizing 3dimensional dose distributions in radiochromic dosimeters. Projection images are acquired by collimating a visible light point source into parallel-beam geometry and imaging differential absorption through the sample dosimeter. Practical challenges involved in optical-CT imaging were addressed through the investigation of an in-house Fresnel-based optical-CT system with considerably less refractive index-matching fluid. The "DFOS" (Duke Fresnel-based Optical- CT System) system differed from current optical-CT systems by replacing cumbersome convex telecentric lenses with a lighter and much less expensive Fresnel system. A second major modification was the replacement of the refractive index-matching fluid bath with a solid polyurethane tank. PRESAGE radiochromic dosimeters were irradiated with orthogonal parallel-opposed treatments and dose distributions were readout by the DFOS system and compared to both treatment planning software prediction and two other in-house optical-CT systems. Gamma index passing rate at the 3%/3mm threshold in relation to Eclipse treatment planning software for the treatment was 92.2%%, compared to 96.8% and 95.6% for two other systems featuring a traditional setup. The DFOS system showed promise for 3D dosimetry, but the performance is still substantially inferior at present to the gold-standard systems.