Image Guided Radiation
Therapy (IGRT)

Our doctors and staff at Houston Methodist are constantly striving to improve the quality of care we provide to our patients. We are committed to treating your cancer in a collaborative and compassionate environment and utilizing the most advanced and individualized therapies available.

Image-guided radiation therapy uses a variety of imaging technologies to plan the best radiation protocol treatment and monitors you even as the treatment is underway to visualize the procedure. Delivery of radiation therapy is more precise in killing tumor cells and sparing normal healthy cells when it is planned and delivered using imaging techniques.


Image-Guided Radiation Therapy (IGRT) Process
The first step is to perform a computerized tomography (CT) scan that takes detailed cross-sectional images, or slices, of the tumor allowing the radiation oncologist to see your tumor in a 3-D format.


Next, a 4-D CT scan is performed. Tumors often move when you breathe, making it difficult to steady the beam of radiation. A 4-D CT scan allows the radiation oncologist to understand where the tumor is located in relationship to your respiratory cycle in addition to its 3-D location.

Once the tumor location has been mapped, the images are uploaded to the IGRT machine. The treatment team lines up the tumor properly before turning on the beam and treating the patient.


An important tool that helps the team visualize the tumor and prevent it from moving is the fiducial marker. This metal marker allows for easier visualization and tracking of the tumor. Fiducial markers are often placed into tumors in the prostate, lung, liver and other tumors.


In some cases, the gland or organ containing the tumor needs to be immobilized. For example, when treating prostate cancer, an immobilization balloon is routinely placed into the rectal area to prevent the prostate gland from moving. The purpose of the balloon is not only to immobilize the prostate gland, but also to distend (stretch out) the rectum, which minimizes the amount of rectal tissue that is within the radiation field.


The patient may also require immobilization. One device used for this is a medical vacuum bag, a bean bag-like device that conforms to the shape of the patient’s body. This keeps the patient still during radiation treatment, and is often used for patients with abdominal and pelvic malignancies. For patients with head and/or neck cancer, a mask keeps the head in the correct position during the administration of radiation.


Houston Methodist is also pioneering a new MRI technology that can be utilized while you are undergoing radiation treatment, a novel approach that’s a first of its kind.  This technology can detect if a tumor has moved out of the field of radiation and can pause the radiation delivery until the tumor has moved back into position.  This technique provides significant improvement in better treating the tumor without impacting the surrounding healthy tissue and provides doctors at Houston Methodist better visualization of your tumor the entire time you are undergoing treatment. 


Virtual Imaging Enhancement Environment
As impressive as IGRT is, the virtual environment developed at Houston Methodist is a stunning advancement. Using data from several different types of scans, clinicians and researchers created a computer augmented virtual environment that extracts enormous amounts of data from existing imaging studies:

  • X-rays
  • Ultrasounds
  • CT
  • MRI
  • Positron emission tests (PET)


This information is used to create a colored 3-D virtual model of your specific anatomy. This image can be used to plan surgery or radiation therapy and to educate doctors and patients. The technology is capable of producing 3-D, 4-D, 5-D and 6-D functional images, meaning doctors can see a beating heart in exquisite detail and follow a vein or artery through the body. Physicians can “see” through skins, muscle, bones and organs in order to make precise measurements to assess the results of therapy. It is a very impressive advance and this specific virtual environment is only available at Houston Methodist.


The powerful and exciting developments in planning and delivering cancer treatments take place in a unique Houston Methodist virtual imaging environment. The unique visualization environment within the Houston Methodist Department of Radiation  enables physicians to view multidimensional images of your internal structures on a multi-touch table. Much like graphics on a video game, this technology creates 3-D anatomical features specific to you and your condition.  Using  state-of-the-art interface technologies, such as voice recognition, motion sensors, multi-touch tables, stereoscopic visualization and game controllers, doctors can better view, understand and treat cancer.  The delivery of radiation therapy is more precise when it is planned and delivered using this advanced imaging technique.


Benefits of Image-Guided Radiation Therapy
The use of image guided radiation therapy offers the following advantages:  

  • Improved quality of care
  • Precise localization (visualization) of the tumor and any normal tissues that might be affected by the radiation
  • Volume and shape evaluation
  • Enhanced visualization utilizing existing standard imaging data and techniques
  • Electronic medical records compatibility


Improved Quality of Care
Houston Methodist is establishing this innovative technology as the standard of care in medical imaging. Doctors can use this virtual environment to: 

  • Increase accuracy in locating and measuring tumors
  • Decrease complications during treatment
  • Assess the impact of unwanted radiation to normal tissues or structures and develop a plan to avoid the unwanted exposure
  • Pre-plan, perform and analyze outcomes before, during and after radiation therapy


Capabilites of the Virtual Imaging Environment

The  multidimensional visualization environment created at Houston Methodist offers a more accurate, interactive understanding of tumor location and local involvement. The colored, 3-D volumetric rendering of your anatomy uses a combination of existing imaging data from the following imaging techniques: 

  • X-rays
  • Ultrasounds
  • Computerized tomography (CT)
  • Magnetic resonance imaging (MRI)
  • Positron emission tests (PET)


Volume Evaluation
Doctors can evaluate the volume of the disease process and even  perform simulated radiation treatments. This allows doctors to know exactly where critical structures and pathways are within your body to avoid unnecessary complications during treatment.


Electronic Medical Records Compatibility
This technology is compatible with your electronic medical record (EMR) and provides personal, portable 3-D imaging records that you will have access to after your treatment
This enhanced visualization environment  will help you and your family more fully understand your personal condition and your specific treatment plan. In addition, it will supplement traditional text-based education with a more visual approach for training residents, medical students and physicians.


Multidisciplinary collaboration within the Department of Radiation Oncology and with other institutions results in scientific research that is translated to the outstanding clinical care we provide. In addition, our standard of care is routinely assessed and updated to ensure that we continue to offer the most effective services to our patients.