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

[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.

[发布机构] 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