Enhancing the Cherenkov Light Image Quality Using Fluorescent Dye for Radiation Therapy
Abstract
Purpose
To study the feasibility of enhancing the Cherenkov light (CL) image of a high-energy photon beam by an opaque cloth containing fluorescent dye.
Methods
A 25-cm3 water bath (WB) was placed on the Varian True Beam linear accelerator treatment couch. A 10MV FFF photon beam with an 8x5-cm2 field size irradiated the phantom at a 90-degree gantry angle. A scientific CMOS camera (PCO.Panda 4.2) positioned 100cm from the WB captured an image of the photon beam from the direction lateral to the beam. A digital color camera (Canon EOS 6D) positioned 80cm from the WB captured photos of the photon beam as well. The shutter durations were 0.1 and 1 seconds for the PCO and Canon cameras, respectively. Thin cotton sheets with varying amounts of fluorescein dye were hung on the wall facing the camera. The fluorescence effects were studied on the photographic images of the radiation beam produced by CL on the cotton cloth. Additional measurements evaluated the impact of fluorescence on fluorescein levels in cotton and the type of dyes, by simulating CL imaging experiments using a flashlight with white light and RGB colors as a visible-light source.
Results
The high-energy photon beam shape, which was visible, became unrecognizable in the photos with a cotton sheet. By adding an optimal amount of fluorescein dye to the cotton sheet, the beam became visible again. Color image analysis showed that the image intensity enhancement was due to the fluorescent dye, which converted shorter-wavelength Cherenkov photons to longer wavelengths in the green or red ranges.
Conclusion
We demonstrated that CL can be used for imaging and dosimetry even when a patient wears opaque clothing by applying fluorescent chemicals to the clothing, which compensate for photon attenuation by emitting additional photons.