Proton vs. Conventional Radiation

Why are protons so much more precise? (My understanding)

I'm comparing proton radiation with conventional, photon or xray, radiation. I've also seen some literature about carbon radiation, but have not had a chance to research it and know too little about it to comment here.

Protons are more precise primarily because they are "particles". Conventional radiation uses "waves". Waves of energy move through human tissue and cannot be stopped. On the other hand, protons can be "stopped" by firing them into tissue of known density at a speed that will cause them to slow down and stop at a precise point. Beyond that, protons do not give off much of their energy until they stop. Then, they give it all up in a hurry. On the other hand photons, (conventional radiation), give up most of their energy as soon as they encounter human tissue. Then they keep right on going and exit out the other side. See the graph below.


Pretend that the "Depth in Water" is the "Depth in your Body". It's close enough to make the point. Imagine that the Y-axis represents your skin where the radiation enters your body. As you go further to the right on the X-axis, you are moving deeper into your body.

The first curve you see is the photons or conventional radiation. Note that they give up most of their energy, (read - 'radiate the tissue'), within the first two centimeters of entering your body. Then, they continue doing so at a lesser and lesser level all the way through your tissue until they finally exit the other side.

The next four curves represent protons. Note that they give off very little of their energy, or radiation, until they get to their programmed depth and then they 'explode' and die. Note especially that they are not going out your back. The way the doctors and physicists cover the whole target is to 'laminate' or 'stack' the proton beams so that they each stop at the appropriate depth to cover the entire target.

There are a couple of terms here that are used in the profession. "Entry Dose" and "Exit Dose".

Note that with conventional radiation, there is a huge entry dose and that is probably not where the target is. Then the energy is largely dissipated before ever reaching the target and it keeps on giving off radiation or energy until it passes out of your body. That's the exit dose.

With the protons there is an entry dose, but it is very low by comparison. As the protons get close to their target and begin to slow, you can see that they very rapidly give up all of their energy and then die. They do not keep going out the other side of your body. No exit dose at all.

That means that the explosion of energy or radiation is concentrated on the target. In this case, the target is your cancer. Because of those curves, known as Bragg Peaks, you can see that they are able to concentrate much higher doses of radiation right on the target without affecting nearby tissues.

Kill, Fang, Kill!!!