How Dosimetry Helps Shape Your Proton Therapy Treatment Plan


It only takes a few minutes for patients to receive their daily proton therapy treatment.  However, for each treatment course, there have been hours of prior planning to develop the best treatment plan according to the radiation oncologist’s prescription.  Dosimetry plays a vital role in proton therapy, helping to create a unique treatment plan comprising of the exact dose,  beam angles and patient positioning aspects required to deliver the dose to the target volume.

Protons are positively charged particles that have a unique range of penetration into the patient’s body.  This is characterized by the Bragg Peak.  The Bragg Peak occurs at the point where the highest dose of radiation is delivered to the patient’s body.  Dosimetrists use physics software tools to determine how to formulate the proton beam energy and intensity in order for the Bragg Peak to occur at the site of the tumor.  With protons, there is minimal entrance dose and no exit dose.  The Bragg Peak happens at the tumor because the protons stop, which makes proton radiation therapy so precise.

Bragg peak shows how proton therapy releases maximum energy at tumor siteThe dosimetry team works closely with the medical physicists and the radiation oncologists to determine the exact physics behind every single proton beam received by patients.  No two treatment plans are the same.  Treatments are completely customized based on the individual’s tumor, body and other factors.

One of the most important goals for our dosimetry team is to find the best treatment plan for every individual patient, with the goal of minimizing radiation to healthy tissue and critical organs.  They do this using pencil beam scanning technology, where the beam of radiation is just millimeters wide. It can be controlled in position and depth in order to bypass nearby organs and target the tumor directly.  The precision of pencil beam scanning, in conjunction with the dosimetrists’ proton therapy treatment plan, ensures that patients receive less radiation outside the target areas. This reduces side effects, while maintaining the patient’s quality of life during and after treatment.

Provision’s team of Dosimetrists in Knoxville is led by Valerie Coffman, a board-certified dosimetrist with more than five years of experience in proton dosimetry. Including Valerie, Provision has a team of four board-certified dosimetrists, one jr. dosimetrist and two dosimetry interns. The dosimetry team works in close collaboration with three board-certified medical physicists, two jr. physicists, one physics assistant and one physics resident.

In Nashville, Provision’s team of dosimetrists is led by Joe Simmons, a board-certified dosimetrist with more than 15 years of experience in proton dosimetry. Including Joe, the Nashville team has three board-certified dosimetrists, one dosimetrist, and one dosimetry intern. They work closely with three board-certified medical physicists and one physics assistant.

Together, our team of medical dosimetry and physics teams work to ensure that our proton therapy patients receive the best treatment plans possible, based on the prescribed radiation dose from our radiation oncology team.


As part of the Provision CARES Cancer Network, Provision CARES Proton Therapy has locations in Knoxville and Nashville, Tenn. If you or someone you know has cancer, we encourage you to call a Provision treatment center near you. One of our Cancer Care Experts can speak to you about your specific diagnosis and help determine if proton therapy is right for you.