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Radiation Therapy at San Marcos

The majority of our care is provided in an outpatient setting using customized therapies ranging from chemotherapy and radiation therapy to advanced technologies like immunotherapy, proton therapy, genetic testing, and genomic sequencing. Advanced treatments and best practices that come from a robust program of clinical trials and leading-edge research create the high caliber of care you’ll find at Texas Oncology.

Radiation Modalities

Texas Oncology-San Marcos offers a robust array of radiation modalities:

Imaging Equipment

  • >Computed Tomography (CT)
    Computed tomography (CT) is a quick and painless procedure that combines X-rays with computers to produce highly detailed cross-sectional pictures of your body. The images provide valuable information for staging your cancer or planning your treatments. Learn More.
    • >CT simulation

      After the initial consultation and decision to use radiation treatment, the next session is usually a planning session, which is called a simulation. Simulation is used to determine the radiation treatment fields and most of the treatment planning. Of all the visits to the radiation oncology facility, the simulation session may actually take the most time.

      The CT simulator does not deliver radiation treatment, but instead allows the radiation oncologist and technologists to see the area to be treated. Images are obtained and transferred to the planning system where a virtual 3D image of the patient is created, and the treatment delivery plan is developed.

      For the simulation session, temporary marks are made on your skin with markers to identify the treatment areas. The room is periodically darkened while the treatment fields are being set. Alignment is critical during simulation and is facilitated by lasers mounted on the wall and ceiling. Special individually constructed immobilization devices may be used to help achieve this alignment. While you may see red lines of light, the low energy lasers are for alignment purposes only and you will not feel burning or anything else from the laser light.

      Once the aspects of the treatment fields are set, the technologist will take special simulation X-rays representing the treatment fields. In most centers, the patient is given multiple “tattoos,” which mark the treatment fields and replace the marks previously made with magic markers. These tattoos are not elaborate and consist of no more than pinpricks followed by ink, appearing like a small freckle. Tattoos enable the radiation technologists to set up the treatment fields each day with precision, while allowing you to wash and bathe without worrying about obscuring the marks that indicate where treatment will be delivered.

      Sometimes several simulation sessions are necessary in order to optimize treatment and are often performed prior to planned “boost” or “reduced field” treatments as part of the overall treatment plan. Learn More.
    • >Diagnostic CT imaging
      A CT scan can help doctors diagnose cancer and identify a tumor’s shape, size, and location. Learn More.

CT Simulation Techniques

  • >3D simulations
    Three-dimensional conformal radiation therapy (3D-CRT) is delivered by radiation beams positioned from different directions that are designed to match the shape of the tumor. This helps to reduce radiation damage to normal tissues and better kill the cancer by focusing the radiation dose on the tumor's exact shape and size. Learn More.
  • >4D CT scanning
    Four-dimensional computed tomography is a type of CT scanning which records multiple images over time. Images are mapped to the breathing cycle to give care teams more information about respiration and internal movement for treatment planning. Planning 4D-CT scans can be used to minimize target volumes for lung cancer radiotherapy. Learn More.
  • >Virtual Simulations
    Simulation is the first step in the radiation oncology treatment process and involves consultation with your physician and radiation therapy team to plan for treatment. Planning includes determining the correct body position for treatment, taking imaging scans, making reference marks for the positions on the skin, and virtual simulation. During virtual simulation, the images taken earlier in treatment planning are used to create a 3D model of your anatomy, including the tumor and its location, which augments an oncologist’s ability to plan the optimal course of treatment. Learn More.

External Radiation Therapy

  • >Conventional 2D, 3D, electron treatments
    • Conventional 2D – Conventional (2D) radiation therapy refers to the technique of radiation therapy where treatments are planned by defining a limited number of beams with the boundaries delineated on patient X-rays. Conventional 2D radiation therapy is typically used for palliative treatment.
    • 3D Conformal Radiation – A type of external beam radiation therapy, 3D conformal radiation therapy combines images from CT, MRI, and PET scans to plan the radiation treatment. Software analyzes the images and helps direct radiation beams to conform to the tumor’s shape.
    • Electron Treatments – Electron therapy uses electrons directed to the outer layers of the skin to cover the surface of the body. It does not go into deeper tissues or organs.  
    Learn More.
  • >Intensity Modulated Radiation Therapy (IMRT)
    Intensity modulated radiation therapy (IMRT) is an advanced form of non-invasive radiation treatment enabling radiation oncologists to precisely target tumor cells. It uses computed tomography (CT) to create 3D images and treatment plans to deliver targeted radiation beams of varying intensity to cancerous tumors. By using image-guidance technologies, your radiation oncologist can localize your treatment and minimize damage to surrounding tissue. Learn More.
  • >Stereotactic Body Radiotherapy (SBRT)
    Stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT) are non-surgical procedures that deliver precisely-targeted radiation at very high doses with minimal damage to surrounding healthy tissue. SRS uses a computer-guided therapy system to treat tumors and other abnormalities of the brain. SRS is ideal for otherwise inoperable tumors, such as those that cannot be treated by traditional surgical methods. SBRT is used in areas of the body other than the brain to treat malignant or benign small to medium size tumors. Learn More.
  • >Stereotactic Radiotherapy (SRT)
    Like stereotactic radiosurgery (SRS), stereotactic radiotherapy (SRT) uses a computer-guided therapy system to deliver large doses of radiation. However, instead of a single session, radiation is delivered on multiple days divided into several doses. Learn More.

Image-Guided Radiation Therapy

  • >Onboard Imaging - Conebeam CT, Kilovotage imaging, Fluoroscopy
    Onboard imaging allows care teams to better align treatment to a tumor that may have a complex shape or move, which damage to healthy tissues.
    • Cone Beam Computed Tomography (CBCT) – Physicians use Cone Beam Computed Tomography (CBCT), which utilizes 3D volumetric imaging (vs. 2D X-ray images), to provide improved visualization, better patient positioning, and more precise treatment of cancerous tumors.
    • Kilovoltage Cone Beam Computed Tomography (kV-CBCT) – A type of board imaging, kilovoltage Cone Beam CT allows care teams to make adjustments to the X-rays that impact the intensity and quality of the image.
    • Fluoroscopy – Fluoroscopy is another medical imaging test that can be used in IGRT. An image of the area is created by sending an X-ray beam continuously through the body to create an image. Physicians can view the image on a monitor in real time to see the movement of internal organs.
    Learn More.

Respiratory Gating

  • > Deep Inspiration Breath Hold Technique
    Deep inspiration breath hold (DIBH) is a technique used to minimize radiation doses to the heart over a course of therapy for breast cancer. During both simulation and treatment, the patient takes a deep breath and holds it for a designated amount of time while radiation is given, allowing for a decrease in radiation dose to the heart.

Radiation Information Systems

  • > Elekta MOSAIQ
    Elekta MOSAIQ® Care Management software helps manage all aspects of a radiation oncology program, keeping patient information easily accessible while simplifying complex treatment management, personalizing decision support, and reducing errors and wait times.