Fig. 4.

The TPS calculated PDD curves are shown for photon beams at $\mathrm{SSD}=100\mathrm{cm}$. The first 0.8 cm of dose deposition contains the only relevant contribution to Cherenkov light that can be emitted from tissue, given that deeper Cherenkov light is largely attenuated as it exits the surface. For each energy, a linear approximation is quite accurate in this shallow depth range.