Image-Guided Radiation Therapy (IGRT)

Radiation oncologists at Houston Methodist are experts in image-guided radiation therapy (IGRT), a type of radiation therapy that helps spare healthy tissue while damaging cancer cells.


Houston Methodist is also pioneering a new MRI technology that can be used 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.

Image-Guided Radiation Therapy Makes Treatment More Precise

Image-guided radiation therapy uses a variety of imaging technologies to plan the best radiation protocol treatment, as well as visualize the procedure even as the treatment is underway. Delivery of radiation therapy in this way is more precise, sparing normal healthy cells.


The use of image-guided radiation therapy offers the following advantages:

  • Increases accuracy in locating and measuring tumors
  • Decreases complications during treatment
  • Assesses the impact of unwanted radiation to normal tissues or structures and helps develop a plan to avoid the unwanted exposure
  • Pre-plans, performs and analyzes outcomes before, during and after radiation therapy
  • Precise localization (visualization) of the tumor and any normal tissues that might be affected by the radiation


The powerful and exciting developments in planning and delivering cancer treatments take place in a unique Houston Methodist virtual imaging environment.

How Image-Guided Radiation (IGRT) Therapy Works

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 the tumor in a 3D format.


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

Cancer Treatment Powered By Virtual Imaging Enhancement Environment

Just as impressive as IGRT is the virtual imaging environment it leverages, which was developed at Houston Methodist.


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, including:

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


This information is used to create a colored 3D virtual model of each patient's 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 3D, 4D, 5D and 6D 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 skin, muscle, bones and organs in order to make precise measurements to assess the results of therapy.