Proton Accelerators Used for Alternative Cancer Treatment

Comparison of dose distributions between IMPT ...

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In the 1970s the US government built a number of cyclotrons across the country. These large circular structures use alternating magnetic currents to accelerate particles through a vacuum chamber at incredibly high speeds.

These beams of high speed particles were used for physics research when they were first built, but the funding for this research has mostly dried up, leaving several multi-million dollar cyclotron facilities sitting unused.

So medical researchers have begun to take over the cyclotrons and utilize them for cancer treatments. The most common form of treatment performed with a cyclotron is proton therapy, where a beam of high-speed protons are shot into the tumor, killing it with radiation.

X-rays and gamma knife treatments deliver radiation to healthy tissue on their way to the tumor, but proton therapy delivers radiation precisely into the body of the tumor, sparing the surrounding tissue. Proton beams deliver their highest radiation doses inside the body, at the center of the tumor, rather than at the surface of the body, like x-rays and traditional radiation treatments.

Proton beams work this way because of the Bragg peak, a certain tissue depth at which the protons release most of their energy. Because the protons are accelerated to incredibly fast speeds, they penetrate some depth into the body before releasing their energy. This allows the proton stream to have a targeted termination, where their energy passes harmlessly through healthy tissue and terminates in the tumor.

This depth can be modulated with the cyclotron, and a Lucite compensator can control the depth of the beam to conform it to the shape of the tumor. A brass aperture also funnels the beam into the shape of the tumor. These Lucite compensators and brass apertures are custom made for each patient to mold to the profile of their tumor. The result is that proton therapy is accurate to within 1 millimeter and can deliver very high levels of radiation to the tumor and next-to-no radiation to the surrounding tissue.

While using a cyclotron to shoot particles into your body at nearly the speed of light might sound risky and painful, the procedure is actually well established and nearly painless. Because of how precisely the radiation is delivered, the procedure is recommended for pediatric tumors and for tumors located deep in the body near vital structures.

In the past 10 years, proton therapy has become a renowned treatment for chondrosarcomas, glioblastomas, prostate tumors, and tumors near the spine. Proton therapy can treat most of these conditions in a few months.

It turns out that putting a piece of your body in front of a stream of particles flying at near the speed of light is not as bad of an idea as you might think.

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