Proton Therapy Basics

Approximately 60 percent of cancer patients receive a course of radiation as part of their treatment plan and traditional radiation is an excellent option for most. However, as many as 30 percent of these patients could benefit from proton therapy. Unlike conventional radiation therapy that uses X-rays, which penetrates through the body, proton therapy releases energy within the target to deliver a maximum radiation dose that stops directly at the tumor site. This enables our physicians to target your cancer cells with pinpoint accuracy while sparing normal, healthy tissue in the rest of your body.

Proton therapy is a painless outpatient treatment given daily over a series of weeks. Each appointment typically lasts less than an hour with the actual treatment time (the time it takes to deliver the proton beam) taking only minutes. For some patients, it can be an alternative to conventional radiation, chemotherapy or surgery or be used in conjunction with one or more of these treatment methods.

The treatment can be applied to localized, solid tumors that have not spread to other parts of the body.

How it works


Protons are positively charged particles in the nucleus of an atom. Protons and X-rays are similar in that they both destroy cells, but protons have the advantage of depositing little radiation going into the body and stopping at the tumor site.

Physicians are therefore able to maximize the cancer killing dose of radiation with less risk of damage to the rest of the body. Patients are better able to tolerate treatment and less likely to experience side-effects during treatment and in the future such as secondary cancers caused by the initial therapy.

The accuracy of proton therapy allows us to:

  • Provide a higher dose of radiation while protecting healthy tissues surrounding the tumor
  • Treat some cancers that traditional radiation cannot
  • Combine with other treatments like chemotherapy
  • Give to patients who have already had conventional radiation therapy
  • Treat pediatric patients while minimizing long-term side effects
  • Just like with X-ray radiation, proton therapy is also provided as an outpatient procedure

Bottom line: Maximum dose, minimum damage

Cutting-edge technology

The Varian ProBeam® Proton Therapy System at MPTC is one of the most advanced systems in the world.

It uses a 90-ton cyclotron to accelerate protons to two thirds the speed of light, sending them down a beamline the length of football field and into one of five treatment rooms.

Four of five of our treatment rooms feature a rotational gantry. This hidden 3-story tall machine helps move the treatment nozzle up to 360 degrees into the precise position to deliver your treatment.

The beam is delivered without sound or pain in a matter of minutes with millimeter precision.

Pencil beam precision

MPTC is also one of only a handful of centers in the country to have a fully integrated system of volumetrically image-guided proton therapy (IGPT) and intensity-modulated proton therapy (IMPT). Along with pencil-beam scanning, these technologies allow for the most accurate application of proton radiation to the tumor. Physicians can direct the proton beam to the exact shape and size of the tumor by ‘painting’ on the dose layer-by-layer, like a 3-D printer. Its precision provides a broader use of proton therapy for difficult tumors near highly sensitive vital organs such as the spine or brain.

Maryland Proton Treatment Center is one of the few centers in the world to feature pencil beam scanning in all five treatment rooms.


Proton Therapy Basics

Proton Therapy for Pediatric Patients


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