Radiation therapy from radioactive sources placed inside the body. A radiation oncologist can implant radioactive material directly into the tumor or very close to it. Radioactive sources can also be placed within body cavities, such as the uterine cervix.

Bragg peak:

The burst of energy released by protons when they reach the end of their path in the body, presumably at the site of a tumor. In proton therapy, the Bragg peak can be placed at any depth in the tissue, according to the depth of the tumor.

Consultation visit:

Initial evaluation by radiation oncologist.

Conventional radiation therapy:

Radiation therapy with X-rays and electrons produced by linear accelerators or radioisotopes such as cesium, iridium, iodine, palladium, etc., used for brachytherapy.

Entrance dose: 

The radiation dose deposited in normal tissues before the radiation reaches the tumor.


Particles commonly used in traditional radiation therapy. Electrons do not travel far into tissue, so they are effective only for superficial tumors.

Exit dose: 

The radiation dose deposited in normal tissues beyond the tumor.

Integral dose: 

The unwanted entrance and exit dose.

Local therapy:

A cancer treatment - usually radiation or surgery - that affects only the tumor and the area close to it.


The breaking away of cancer cells from the original tumor, settling elsewhere in the body and forming a new tumor.


The spread of cancer from one part of the body to another.

Pencil beam scanning:

A proton therapy delivery technique that deposits radiation in the tumor layer by layer, like a painter’s brush strokes. It conforms to the specific shape of a tumor and can be adjusted for intensity to achieve the desired dose distribution.


A specific treatment or series of treatments developed to treat cancer.


Positively charged particles used in proton therapy to destroy cancerous cells.

Proton therapy:

The use of protons - instead of X-rays - in radiation therapy to more specifically target tumors with a lower risk to healthy tissue.

Radiation therapy: 

Treatment by the use of radiation. Radiation therapy is used in the treatment of approximately half of all cancer cases.

Simulation visit: 

During the patient visit prior to treatment, we use MRI, CT, and/or PET-CT images and dose calculating software to precisely locate the cancer and prepare a personalized treatment plan that works best for the patient.

Therapeutic ratio:

The probability of tumor eradication as compared to the risks and side effects of a cancer treatment.

Therapeutic Ratio = probability of tumor eradication/probability of treatment complication


Harm caused to healthy tissue by inadvertent exposure to radiation.


A mass caused by a concentration of cells, either benign or malignant.

UF Health Proton Therapy Institute Experts consulting

Proton therapy is effective in treating many cancer types.

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