  Although the Cherenkov light contains mostly short-wavelength components, it
is beneficial in the aspect of imaging to visualize it in the second
near-infrared (NIR-II) window. In this study, Cherenkov imaging was performed
within the NIR-II range on megavolt X-ray beams delivered by a medical linear
accelerator. A shielding system was used to reduce the noises of the NIR-II
image, enabling high quality signal acquisition. It was demonstrated that the
NIR-II Cherenkov imaging is potentially a tool for radiotherapy dosimetry, and
correlates well with different parameters. The NIR-II Cherenkov imaging is less
susceptible to scattering, while more susceptible to absorption, compared with
the visible-near-infrared imaging. Finally, a mouse was used to demonstrate
this technology on animals. These results indicate the potentials to apply
NIR-II Cherenkov imaging in the practice of radiotherapy.
