Aperture

Aperture

A metal block containing a hole through which the radiation ( proton) beam passes. Each portal for each patient requires a custom-made aperture. The shape of the hole is the approximate shape of the target being treated by the beam. Every patient has her or his own set of apertures, and no other patients use them.

My MRI and CT Scan created my aperture by allowing the technicians to know the size of my prostate.  The purple above in this example could be my prostate.  If you look at my prostate and look at the picture above in the actual room where the apertures are created see how they look the same.  The proton beam passes through my aperture and treats my prostate.  My treatment treats my prostate and only my prostate.  Spares the other organs which mean less side affects and more quality of life after treatment.  Hope this helps you understand the procedure.

Then when you throw in the physics of this procedure the radiation beam (proton) releases the bulk of its power when it hits the tumor.  I understand nothing about physics.  In fact, I don't ever remember taking any physics class while in high school and I know I didn't take any in college (cause I picked the classes I wanted to enroll in).