About Proton Therapy

Proton radiation treatment, or proton beam therapy, is the most precise and advanced form of radiation therapy available today. It is a painless, non-invasive treatment that allows patients to maintain their quality of life and quickly resume normal activities. This is because proton therapy allows physicians to deliver full or higher treatment dosages that destroy the main tumor site without causing harm to surrounding healthy tissue or organs.

What Makes Proton Therapy Better?

Proton therapy is a better than standard radiation therapy for cancer because it is more precise and causes less damage to a patient’s body. Conventional radiation therapy uses photons, X-rays, to attack cancerous and noncancerous tumors.

Photon beams carry a low radiation charge and have a much lower mass than proton beams. As a consequence, much of a photon beam’s energy is deposited in the healthy tissue surrounding a tumor causing side effects and unnecessary tissue damage while sometimes not even reaching the tumor with an adequate dose of radiation.
In contrast, protons carry a charge and have a greater mass than photons. This allows them to be energized to specific velocities. As the protons travel through the body they slow down as they interact with electrons. When they have slowed down sufficiently, they release a burst of energy. By regulating the velocity of the protons, a physician can design the proton radiation treatment so this burst occurs at the precise site of the cancer or benign tumor, minimizing damage to healthy tissue.

The greater control offered by proton radiation is also what allows physicians to offer superior treatment management. It also contributes to the quicker recovery times and minimal side effects. Though proton therapy treatment is painless and non-invasive there are some potential side effects including nausea, vomiting or diarrhea.

History of Proton Radiation Treatment

Using high-energy protons for medical treatment was first proposed in 1946. Less than 10 years later, protons were first used to treat patients with certain cancers. Research and laboratory applications increased rapidly within the next 30 years. However, it was not until
the John M. Slater Proton Therapy and Research Center became operational that the full benefits of proton therapy could be offered to cancer patients of all types.

Built by U.S. Department of Energy’s Fermi National Accelerator Laboratory (Fermilab) physicists and engineers, LLUMC’s accelerator is the world's smallest variable-energy proton synchrotron. It is designed to deliver a beam of energy sufficient to reach the deepest tumors in patients. Proton radiation treatment is notably valuable for treating localized, isolated, solid tumors that may spread to other areas of the body.

How Proton Therapy Works

Learning more about how protons therapy works will allow you to understand how it can help you.

Each proton begins its journey at an injector located within an electric field. In the field, hydrogen atoms are separated into negatively charged electrons and positively charged protons. The protons are then sent through a vacuum tube within a pre-accelerator. This process boosts their energy to two million electron volts.

The protons continue in the vacuum tube and begin their high-speed journey in the synchrotron. They travel around the synchrotron about 10 million times per second. Each time they circulate, a radiofrequency cavity within the ring delivers a boost of energy. This increases the protons' energy to between 70 and 250 million electron volts. The voltage achieved is enough to place them at any depth within the human body.

After leaving the synchrotron, the protons move through a beam transport system, continuing in the vacuum tube through a series of steering and focusing magnets that guide them to the four treatment rooms at the Proton Treatment Center.

The equipment in the treatment rooms vary based on the conditions treated. One treatment room has a stationary beam with two branches – one branch for irradiating eye tumors and the other for central nervous system tumors and tumors of the head and neck. The other three treatment rooms have gantries – wheels 35 feet in diameter that revolve around the patient to direct the beam to exactly where it is needed. From the patient's perspective, all that is visible is a revolving, cone-shaped aiming device. A fifth room, used for beam calibration and basic research, contains three additional beam lines.

Each treatment room has a guidance system to direct the beam used to treat the patient. The guidance system monitors the beam until it enters the patient and positions it to conform to the size and shape of the.

The beam delivery system, or nozzle, is the last device the protons travel through before entering the body. The nozzle shapes and spreads out the proton beam in three dimensions. Radiation oncologists must determine location, shape and tissue density of the target tumor before determining the number of protons to be delivered. They must also calculate the depth that the protons must travel in order to calculate the speed and shape of the beam. These decisions render a beam that is highly accurate and practically ‘tailor made’ for a specific treatment.  After leaving the nozzle, the protons enter the patient's body.