As is typical with cyclotrons, the beam initially has a Gaussian shape, which looks like this:
Friday, June 10, 2011
Beam Shaping 101
On our way to the proton center today, I got a call saying the machine was having problems, and my treatment would be delayed. It only ended up being about an hour and a half later than expected, but they made up for it by taking me to the beam control room to meet two of the physicists who run things. I got to hear all about how the beam is shaped before it arrives at my brain.
As is typical with cyclotrons, the beam initially has a Gaussian shape, which looks like this:
where the height represents the number of protons in that part of the beam. We'd really prefer a uniform beam, since this will be easier to shape into the particular distribution we want, conforming to the tumor being treated. To do this, they send the beam through a lead lens, to get a beam that looks like this:
where the color indicates the speed of the protons, blue being the slowest. This still isn't ideal, since we no longer have uniform velocity, so the beam is also sent through a plastic lens, which slows the protons without spreading them out:
Now we have a beam that's uniform both in velocity and in density, ready to be sent into my head.
As is typical with cyclotrons, the beam initially has a Gaussian shape, which looks like this:
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What's the X-axis in these graphs?
ReplyDeleteThe x-axis is the position within the beam. Really, it should be 3-D, but these are just the center slice. You could imagine spinning them around the center axis to get the real shape.
ReplyDeleteI was going to ask the same question, thinking originally that the x-axis was energy. Of course, this would make the second plot contradictory.
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