How Does Proton Therapy Work?
The cancer-seeking proton beam at the Roberts
Proton Therapy Center begins inside a cyclotron,
a machine that, at just slightly bigger than an
SUV, weighs 220-tons – as
much as a 747 jetliner. The cyclotron uses enormously
powerful magnets to strip protons from the hydrogen
atoms in water and accelerate them to higher and
higher velocity around a circular path, like cars
on a racetrack.
When the protons reach their top speed and highest energy, they're directed out of the cyclotron by other magnets into a beamline, an airless tube that runs for about the length of a football field. At various points along the beamline, the proton beam is channeled by other magnets into five treatment rooms, four of them equipped with a 90-ton gantry, a rotating steel structure that moves around the patient to aim the beam at any angle. (The fifth treatment room uses a "fixed beam," around which the patient is positioned as needed.) This extensive space – where as many as 200 patients will be treated each day once the center reaches full capacity — makes the Roberts Proton Therapy Center the largest such center in the world.
Inside the treatment room, in the "nozzle" where the proton beam exits the beamline, a device called a multileaf collimator precisely tunes the energy of the beam and actually shapes it to match the unique profile of the individual patient's tumor, so that the most effective dose can be delivered exactly where it's needed. The Roberts Proton Therapy Center will be the only proton therapy center in the world that uses the cutting-edge multileaf collimator to individually shape the proton beam to fit each patient's tumor.