Houston Methodist. Leading Medicine.
Houston Methodist. Leading Medicine

Radiation Therapy

Radiation therapy is the use of various forms of radiation to safely and effectively treat cancer and other diseases. Radiation oncologists may use radiation to cure cancer, to control the growth of the cancer or to relieve symptoms, such as pain. Radiation therapy works by damaging cells. Normal cells are able to repair themselves, whereas cancer cells cannot. New techniques also allow doctors to better target the radiation to protect healthy cells. Sometimes radiation therapy is the only treatment a patient needs. At other times it is used in combination with other therapies such as surgery and/or chemotherapy.

Treatment External Beam Radiation Therapy – During external beam radiation therapy, a beam of radiation is directed through the skin to the cancer and the immediate surrounding area in order to destroy the main tumor and any nearby cancer cells. To minimize side effects, the treatments are typically given five days a week, Monday through Friday, for a number of weeks. This allows doctors to get enough radiation into the body to kill the cancer while giving healthily cells time each day to recover.
The radiation beam is usually generated by a machine called a linear accelerator. The linear accelerator, or Linac, is capable of producing high–energy X–rays and electrons for the treatment of cancer. Using high–tech treatment planning software, your treatment team controls the size and shape of the beam, as well as how it is directed at the body, to effectively treat the tumor while sparing the surrounding normal tissue.
Several special types of external beam therapy are discussed in the next sections. These are used for specific types of cancer, and your radiation oncologist will recommend one of these treatments if he or she believes it will help you.

Three–Dimensional Conformal Radiation Therapy (3D–CRT) – Tumors are not regular – they come in different shapes and sizes. Three–dimensional conformal radiation therapy, or 3D–CRT, uses computers and special imaging techniques to show the size, shape and location of the tumor. Computer assisted tomography (CT or CAT scans), magnetic resonance imaging (MR or MRI scans) and/or positron emission tomography (PET scans) are used to create detailed, three-dimensional representations of the tumor and surrounding organs. The radiation oncologist can then precisely tailor the radiation beams to the size and shape of the tumor with multileaf collimators (see picture) or custom fabricated field shaping blocks.

Intensity Modulated Radiation TherapyIntensity Modulated Radiation Therapy, or IMRT, is a specialized form of 3D–CRT that allows radiation to be more exactly shaped to fit the tumor. With IMRT, the radiation beam can be broken up into many "beamlets", and the intensity of each beamlet can be adjusted individually. Using IMRT, it may be possible to further limit the amount of radiation that is received by healthy tissue near the tumor. In some situations, this may also allow a higher dose of radiation to be delivered to the tumor, potentially increasing the chance of a cure.

Volumetric Modulated Arc Therapy or VMAT – This new technology improves upon current IMRT and Tomotherapy treatment delivery techniques. VMAT delivers highly precise treatment much faster than other technologies. Treatments that once took 15–30 minutes can sometimes be accomplished in as little as a single rotation of the machine around the patient, that is, in about 2 minutes. It is also more conformal that current IMRT thus decreasing dose to adjacent normal structures which can possibly decrease side effects. Finally, VMAT gives less scattered dose to the patient which can possibly decrease the chance of developing a secondary cancer in the future.

Image Guided Radiation Therapy – Radiation oncologists use image–guided radiation therapy, or IGRT, to help better deliver the radiation to the cancer since tumors can move between treatments due to differences in organ filling or movements while breathing. IGRT involves conformal radiation treatment guided by imaging, such as CT, ultrasound or X–rays taken in the treatment room just before the patient is given the radiation treatment. All patients first undergo a CT scan as part of the planning process. The imaging information from the CT scan is then transmitted to a computer in the treatment area to allow comparison of the earlier image with the images taken just before treatment. If necessary adjustments can be made to better target the cancer, while avoiding nearby healthy tissue. In some cases, doctors will implant a tiny marker in or near the tumor to pinpoint it for IGRT.

SJMH IGRT Stereotactic RadiotherapyStereotactic radiotherapy is a technique that allows the radiation oncologist to precisely focus beams of radiation to destroy certain types of tumors. Since the beam is so precise, the radiation oncologist may be able to spare more normal healthy tissue. This additional precision is achieved by using very secure immobilization, such as a head frame in the treatment of brain tumors. Sometimes a high dose of stereotactic radiotherapy can be focused upon a tumor outside the brain and given in a few treatments (typically three to eight). This form of treatment is called stereotactic body radiation therapy.

Our Staff

At Houston Methodist San Jacinto Hospital Radiation Therapy and Cancer Center, we understand that the prevention, diagnosis and treatment of cancer extend beyond the patients physical needs. That is why our radiation oncology department employs a range of highly–skilled professional who provide knowledgeable and compassionately care to patients and their families.

Radiation Oncologists

Radiation oncologists are the doctors who will oversee your radiation therapy treatments. These physicians work with the other members of the radiation therapy team to develop and prescribe your treatment plan and make sure that each treatment is given accurately. Your radiation oncologist will also track your progress and adjust the treatment as necessary to make sure you receive the best care. Radiation oncologists help identify and treat any side effects that may occur due to radiation therapy. They work closely with other cancer doctors, including medical oncologists and surgeons, and all members of the radiation oncology team. Radiation oncologists have completed at least four years of college, four years of medical school, one year of general medical training and four years of residency (specialty) training in radiation oncology. They have extensive training in cancer medicine and the safe use of radiation to treat disease. If they pass a special examination, they are certified by the American Board of Radiology. You should ask if your doctor is board certified.

Medical Physicists

Medical physicists work directly with the radiation oncologist during the treatment planning and delivery. They oversee the work of the dosimetrists and help ensure that complex treatments are properly tailored for each patient. Medical physicists develop and direct quality control programs for equipment and procedures. They also make sure that the equipment works properly by taking precise measurements of the radiation beam and performing other safety tests on a regular basis.


Dosimetrists work with the radiation oncologist and medical physicist to carefully calculate the dose of radiation to make sure the tumor get enough radiation. Using computers, they develop a treatment plan that can best destroy the tumor while sparing the health tissue. Dosimetrists are individuals who possess strong mathematical skills and the ability to visualize objects in three–dimensional concepts. They are experienced with computers and possess an understanding of the technical aspects of radiation oncology and medical physics to meticulously derive computerized treatment plans, then communicate these aspects to the radiation oncologist for plan approval and to the radiation therapists for plan implementation. Following meeting specific educational and clinical requirements dosimetrists are eligible to sit for certification examination.

Radiation Therapists

Radiation Therapists work with the radiation oncologists to give the daily radiation treatment under the doctor´s prescription and supervision. They maintain daily records and regularly check the treatment machines to make sure they are working properly. Radiation therapists undergo specialized training in radiation physics, and radiation biology, oncology, patient care and patient safety. They must pass a national registry exam to show competency as well as be licensed by the State of Texas.

Radiation Oncology Nurses

Radiation oncology nurses work with every member of the treatment team to care for you and your family before, during and after treatment. They will explain the possible side effects you may experience and will describe how you can manage them. They will assess how you are doing throughout treatment and will help you cope with the changes you are experiencing. If they pass a special exam, they are certified as an Oncology Certified Nurse.

Patient Navigator

Patient navigation is a support service in which a trained staff member guides patients through the cancer care system. Patient Navigators act as the support hub for all aspects of the patient's movement through the health care continuum. The Navigator´s role is to promote smooth and timely continuity of care from diagnosis and through all related activities/services.


Nutritionists, also called dietitians, can help you maintain your weight during treatment. They will help you modify your eating plan if the side effects of treatment are affecting your appetite, will determine what you can eat and provide recipes, menu suggestions and information on ready–to–use nutritional supplements.

Physical Therapists

Physical therapists use exercises to help your body function properly while you are undergoing treatment. These exercises can help manage side effects, alleviate pain and keep you healthy.



If you are considering radiation therapy, you must first meet with a radiation oncologist to see if radiation therapy is right for you. During this first visit, the consultation, your doctor will evaluate your need for radiation therapy and its likely results. This includes reviewing your current medical problems, past medical history, past surgical history, family history, medications, allergies and lifestyle. The doctor will also perform a physical exam to assess the extent of your disease and judge your general physical condition. After review your medical tests, including CT scans, MRI scans and PET scans, and completing a thorough examination, your radiation oncologist will discuss with you the potential benefits and risks of radiation therapy and answer your questions.


To be most effective, radiation therapy must be aimed precisely at the same target(s) each and every time treatment is given. The processes of measuring your body and marking your skin to help your team direct the beams of radiation safely and exactly to their intended locations is called simulation. During simulation, your radiation oncologist and radiation therapist place you in the exact position you will be in during the actual treatment. Your radiation therapist, under your doctor´s supervision, will acquire images using a special treatment planning CT scanner and then they will place marks showing the area to be treated directly on your skin or on immobilization devices. Immobilization devices are molds, casts, headrests or other devices that help you remain in the same position during the entire treatment.

Treatment Planning

The radiation oncologist works with the medical physicist and dosimetrists aided with sophisticated treatment planning computer software to help design the best possible treatment plan for each specific patient. After reviewing all of this information, your doctor will write a prescription that outlines exactly how much radiation you will receive and to what parts of your body.

Patient and physician forms and information

Electronic Medical Record

Utilizing MOSAIQ a dedicated oncology information software system patient data is captured electronically enabling streamlined radiation oncology workflow from the first diagnosis and staging, through planning, treatment, follow-up and long–term survivorship. At the heart of MOSAIQ is the image-enabled electronic medical record (EMR) by which healthcare professionals communicate information about their patients through the entire spectrum of cancer care.

MOSAIQ´s state–of–the–art features include complete, integrated documentation of patient health history (including diagnosis, medications/allergies, and treatment information), as well as the ability to include external documentation.

New Patient Forms

Physician Forms


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