rrc185, I decided very quickly to have proton radiation therapy rather than photon radiation. The radiation oncologist described how precise the targeting of the proton beam is compared to photon therapy and thus has the potential for much less collateral damage to nearby healthy tissue. My wife and I also went on a tour of the radiation facility at Mayo (the GLOW tour) where a physicist explained the process using very informative videos. The very narrow beam is precisely aimed at numerous points on the tumor over the course of the treatments. The calculations for the targeting process are very detailed and complex. A great deal of time is spent planning the process and adjusting as necessary. They showed my wife about halfway through treatment how distinct the line on my cheek inside my mouth was where the beam was entering to hit the tumor. She said it looked like it had been drawn with a ruler. I have had side effects from it but they haven’t been a a major ongoing disruption. Hope this helps