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Radiation Oncology At St. Joseph's

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Radiation oncology is the field of cancer treatment that involves the administration of therapeutic radiation, essentially high-energy waves or streams of particles configured into specific doses.

High-dose but carefully monitored and measured radiation therapy kills cancer cells with minimal or no effect on surrounding healthy tissue and is used to treat many kinds of cancer. According to the American Society for Radiation Oncology (ASTRO), three cancers – breast cancer, prostate cancer, and lung cancer – make up 56 percent of all patients receiving radiation therapy. ASTRO also points out that at least 75 percent of patients are treated with the intent to cure cancer, rather than control the growth or relieve symptoms like pain.


Radiation oncologists are cancer specialists who focus on treating the disease with radiation therapy, and they are a critical part of a multidisciplinary team that cares for patients at Dignity Health. Along with medical oncologists, other medical specialists, nurses, technologists and other support staff at Dignity Health, radiation oncologists are highly trained and often acclaimed by other health care professionals and medical organizations. The radiation oncology medical director at Dignity Health, Aidnag Diaz, MD, brings a wealth of experience to his work here. Click here to meet the radiation oncology physician team.

Philosophy of Care

The philosophy of the radiation oncology department at Dignity Health is simple: patients will receive the highest quality of care while also receiving the highest level of compassion, as we treat the cancer together. Our goal is to help you get better. We will also try to provide answers to all of your questions about your treatment.


At Dignity Health, patients may be treated with one of several radiation modalities, or therapeutic methods, using advanced technologies depending on what their radiation oncologist prescribes. Whichever treatment is recommended, you will not receive your first radiation therapy treatment at your first visit. At that visit or possibly a subsequent visit, you will have a CT scan and measurements will be taken so that the therapy dosages and intensities can be precisely crafted to your needs. At your following visit, you will begin to undergo your treatment.

Here is information from experts at Dignity Health and the National Cancer Institute about the different types of radiation treatments available:

  • Brachytherapy
  • True Beam™ Linear Accelerator
  • External beam radiation
  • Image-guided radiotherapy (IGRT)
  • Intensity-modulated radiation therapy (IMRT)
  • Stereotactic radiosurgery
  • Stereotactic body radiation therapy


In general, radiation therapy can be delivered externally or internally.  When radiation is delivered internally or directly into or adjacent to the tumor, it is called brachytherapy.  Brachytherapy is divided into low-dose-rate (LDR) brachytherapy (permanent, radioactive seeds) or high-dose-rate (HDR) brachytherapy.  

  • Low-Dose Rate (LDR) Brachytherapy is internal radiation, delivered through a device that resembles seeds, ribbons or wires and is implanted into the body. 
  • High-Dose Rate (HDR) Brachytherapy at the the Dignity Health – Cancer Institute at St. Joseph's Hospital and Medical Center is used for the treatment of cancers of the skin, head and neck, breast, uterus, cervix, and prostate as well as others.  With HDR brachytherapy, we insert small plastic tubes into the tumor region, deliver high doses of radiation directly into the cancer, and remove the tubes prior to sending patients home without anything radioactive left inside.  This approach allows us to treat cancers from the “inside out,” which in turn allows us to safely escalate the radiation dose to the cancer while minimizing dose to the surrounding normal tissues.  HDR brachytherapy offers a safe, precise, and highly effective treatment modality when utilized in selected cancers by well-trained physicians.  

Brachytherapy is a way to treat cancer from the inside out. Patients benefit from this type of treatment because the high-energy waves used in radiation therapy are able to kill fast-growing cancer cells while minimizing damage to healthy tissue.

True Beam™ Linear Accelerator is the tool that serves as the foundation for several different types of non-invasive radiation therapy. A linear accelerator is a large machine that aims radiation at the cancer. The machine moves around you without touching you and doesn’t hurt. It doesn’t make you radioactive and the radiation can’t be seen, felt, or smelled. The linear accelerator is used with these forms of treatment:

  • External beam radiation. This is a common cancer treatment that uses high doses of radiation to destroy cancer cells and shrink tumors.
  • Image-guided radiotherapy (IGRT) is a procedure that relies on a machine like a linear accelerator along with a computer to create a picture of a tumor to help guide the radiation beam during radiation therapy. The pictures are made using CT, ultrasound, X-ray, or other imaging techniques. Image-guided radiation therapy makes radiation therapy more accurate and causes less damage to healthy tissue.
  • Intensity-modulated radiation therapy (IMRT) is a type of three-dimensional radiation therapy that also starts with a linear accelerator and uses computer-generated images to show the size and shape of the tumor. Thin beams of radiation of different intensities are aimed at the tumor from many angles. This type of radiation therapy reduces the damage to healthy tissue near the tumor.
  • Stereotactic radiosurgery is a non-invasive treatment for cancerous and non-cancerous tumors in the brain or spinal cord. Using Leksell Gamma Knife® Perfexion™ technology, the treatment delivers beams of high-dose radiation with extreme accuracy and provides a pain-free, non-surgical option for patients who have inoperable or surgically complex tumors.
  • Stereotactic body radiation therapy is a non-invasive treatment for cancerous and non-cancerous tumors outside the central nervous system. The CyberKnife® System technology is use for this type of treatment. Similar to the Gamma Knife® Perfexion™ system, this robotic radiosurgery system treats cancerous and non-cancerous tumors of the kidney, liver, lung, pancreas, prostate, and spine.

Questions to ask your radiation oncologist about your treatment:

  • Why are you recommending this particular treatment for me?
  • How will this treatment help me?
  • How often, and for how long, will I receive treatment?
  • What side effects should I expect? How will these side effects be managed?
  • Is infertility a possibility for me? Can you give me the name of a fertility expert to meet with?
  • What changes might I have after treatment? How long will these changes last?

For more information about radiation oncology, or to make an appointment, call (602) 406-8222.