Image Guided Radiation Therapy (IGRT)
To fight the battle against cancer, you want to have the most advanced technology and technically trained professionals at your disposal. Houston Methodist Hospital’s Department of Radiation Oncology offers one of the most revolutionary technologies available today – image-guided radiation therapy or IGRT.
IGRT machines deliver high doses of radiation in a very precise, accurate manner. These machines target the tumor directly, limiting radiation exposure to healthy, noncancerous tissues. The IGRT machine easily pinpoints the beam from many different angles using an advanced computer mapping system. Mapping ensures the most complete radiation therapy dose with the fewest side effects in a shorter amount of time.
The Treatment Process
The first step is to perform a CT scan that takes detailed cross-sectional images, or slices, of the tumor. The radiation oncologist draws the location of your tumor on each slice. These slices are then stacked atop one another in our computer system, allowing the radiation oncologist to visualize your tumor in a 3-D format.
Next, a 4-D CT scan is performed. Tumors often move when a patient breathes, 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 the patient’s respiratory cycle in addition to its 3-D location.
Once the tumor location has been mapped out, 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 the tumor 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, and special devices are often used. One example is a 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.
IGRT is much more than simply turning on a radiation beam. It is a collection of carefully planned components and stages. Imaging during treatment, immobilization of the tumor and the patient, placement of fiducial markers and high-end computers are all essential for image guided radiation to achieve its extraordinary results.
Houston Methodist Hospital is proud to offer you our expertise – and our compassion – at every step of the treatment process.