  The Circular Electron-Positron Collider (CEPC) can also work as a powerful
and excellent synchrotron light source, which can generate high-quality
synchrotron radiation. This synchrotron radiation has potential advantages in
the medical field, with a broad spectrum, with energies ranging from visible
light to x-rays used in conventional radiotherapy, up to several MeV. FLASH
radiotherapy is one of the most advanced radiotherapy modalities. It is a
radiotherapy method that uses ultra-high dose rate irradiation to achieve the
treatment dose in an instant; the ultra-high dose rate used is generally
greater than 40 Gy/s, and this type of radiotherapy can protect normal tissues
well. In this paper, the treatment effect of CEPC synchrotron radiation for
FLASH radiotherapy was evaluated by simulation. First, Geant4 simulation was
used to build a synchrotron radiation radiotherapy beamline station, and then
the dose rate that CEPC can produce was calculated. Then, a physicochemical
model of radiotherapy response kinetics was established, and a large number of
radiotherapy experimental data were comprehensively used to fit and determine
the functional relationship between the treatment effect, dose rate and dose.
Finally, the macroscopic treatment effect of FLASH radiotherapy was predicted
using CEPC synchrotron radiation light through the dose rate and the
above-mentioned functional relationship. The results show that CEPC synchrotron
radiation beam is one of the best beams for FLASH radiotherapy.
