History of Proton Therapy
The advancements of proton technology as a treatment option for cancer are exciting, but not new. The idea of using protons in medical treatment was first suggested in 1946 by physicist Robert R. Wilson, Ph.D. The first attempts to use proton radiation to treat patients began in the 1950s in nuclear physics research facilities, but applications were limited to few areas of the body.
In the late 1970s, imaging advancements coupled with the development of sophisticated computers and improved accelerator and treatment delivery technology made proton therapy more viable for routine medical applications, such as cancer treatment. Only in recent years has it become possible to develop proton beam facilities in conjunction with established medical centers.
In 2006, MD Anderson opened the Proton Therapy Center and began treating patients with one of the most advanced and innovative technologies available: proton therapy.
At that time, the center was one of only three in the nation and the first of its kind integrated within a comprehensive cancer hospital , giving patients the benefit of a powerful technology with fewer side effects, all delivered by world-renowned cancer specialists. Today, the center remains one of only thirteen proton therapy centers nationally – and still the only at one of the nation’s the top cancer centers.
The advantage of proton therapy (also called proton beam therapy) is that the physician can control where the proton releases the bulk of its cancer-fighting energy. As the protons move through the body, they slow down and interact with electrons, and release energy. The point where the highest energy release occurs is the “Bragg peak.” A physician can designate the Bragg peak’s location, causing the most damage to the targeted tumor cells. A proton beam conforms to the shape and depth of a tumor, while sparing healthy tissues and organs.
How does it work?
The best way to understand how proton therapy works is to take a look at the physics and engineering inside the proton accelerator, or the synchrotron, and the beam delivery system.
•The proton begins its journey at the ion source. Within fractions of a second, hydrogen atoms are separated into negatively charged electrons and positively charged protons.
•The protons are injected via a vacuum tube into a linear accelerator and in only a few microseconds, the protons’ energy reaches 7 million electron volts.
•Proton beams stay in the vacuum tube as they enter the synchrotron, where acceleration increases their energy to a total of 70 million to 250 million electron volts, enough to place them at any depth within the patient’s body.
•After leaving the synchrotron, the protons move through a beam-transport system comprised of a series of magnets that shape, focus and direct the proton beam to the appropriate treatment room.
•To ensure that each patient receives the prescribed treatment safely and efficiently, the facility is controlled by a network of computers and safety systems. The gantry can revolve 360 degrees, allowing the beam to be delivered at any angle.
•As protons come through the nozzle, a custom-made device (the aperture) shapes the beam of protons, and another custom-made device (the compensator) shapes the protons into three dimensions, delivering them to the depth of the tumor.
•At maximum energy, a proton beam travels 125,000 miles per second, which is equivalent to the two-thirds the speed of light.
•From the hydrogen canister to the patient, a proton typically travels 313,000 miles.