Radiochromic film thickness correction with convergent cone- beam optical CT scanner

8th International Conference on 3D Radiation Dosimetry

Jordan, Kevin^1

London Health Sciences Centre, Department Medical Biophysics, Western University, London

ON, Canada^1

关键词: Active films;    Dose distributions;    Narrow band sources;    Non-uniformities;    Optical computed tomography;    Radiochromic film;    Relative thickness;    Transmission images;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/573/1/012059/pdf
DOI  :  10.1088/1742-6596/573/1/012059

来源: IOP

【 摘 要 】

A cone-beam optical computed tomography (CT) scanner was modified by replacing the diffuse planar yellow light emitting diode (LED) source with violet and red LEDs and a large Fresnel lens. The narrow band sources provided transmission images of radiochromic EBT2 film at 420 and 633 nm, with air as a reference. The dose image was not detectable with the violet source. This demonstrated spectral independence of the two images. Assuming attenuation at 420 nm was dominated by absorption from yellow dye in the active film layer allowed a relative thickness image to be calculated. By scaling the 633 nm optical density image for relative thickness, non-uniformities in the recorded dose distribution due to film thickness variations, were removed.