Image-guided Radiation Therapy or IGRT is an advanced form of high-precision radiotherapy that uses a computer-controlled X-ray system to deliver precise radiation doses to a malignant tumor. John Buatti, MD, professor and head of the Department of Radiation Oncology at University of Iowa Hospitals and Clinics, talks about IGRT:
How is IGRT treatment different from other radiation treatments?
IGRT has the unique ability to visualize the internal anatomy of the patient as they're being treated. When the patient is put into position for treatment, we obtain a CT scan and match it exactly to the plan that was created for that individual patient. You can then move the patient into better position and have all the structures line up perfectly, or as close to perfect as possible.
Why is pinpointing radiation therapy to just the area affected with cancer important?
It's absolutely critical that you deliver the dose to the tumor, but even more importantly sometimes is avoiding those critical normal structures that might be near where the tumor is located. By pinpointing it and using that CT anatomy, you can actually move the tumor a little bit farther away or a little bit closer to where you exactly want it, each day of the treatment.
Who is qualified to receive IGRT as part of their cancer care?
We're using IGRT for a large number of patients. We're using it for:
- All prostate cancer patients. We can see the prostate and move it away.
- Head and neck cancer patients. We can perfectly model where the spinal chord is in relationship to the high dose and critical structures like the salivary glands.
- Pelvic area for rectal and gynecologic malignancies. Patients can have their lymph nodes much more precisely targeted.
- Pancreas cancers. We think that there are a large number of applications for this technology if you learn to use it properly.
Who makes up the team that plans a patient's IGRT treatment?
A large number of health care professionals are involved. This takes a large group of dedicated physicists--we have nine full time PhD and Master's level physicists that help with quality assurance. We have radiation therapists who deliver the treatment to patients. We have very highly sub-specialized physicians in each of the different areas and different cancers. We have specialized nurses who work with the patients at the time that they're getting therapy. And we have dosimetrists, people who specialize in doing the planning with this. So it's a very large group of health care professionals that contribute to each patient's care.
Is special equipment used to deliver IGRT treatment?
There's special hardware that enables you to get the CT scans in the position and there's special delivery devices for this--a special software that rapidly enables the images to be merged and then repositioned precisely. It's a form of digital radiation therapy, where you link the actual digital image of the patient as they're being treated, to the planned digital image that was obtained previously for the planning.
How is the procedure preformed?
We do what's called a simulation or planning session. During that we get very, very detailed CT scans. We use PET imaging, which is functional imaging. We frequently get MRI imaging as well. We merge all of the images of the patient so that they match, and come up with identification of both where the tumor target is, areas that might be of some risk, and identify the most critical structures. We then put them into a computer planning system and figure out the best ways to spare the normal tissue and get the dose precisely to the tumor. Sometimes that process takes about five days by dosimetrists and physicists working with the physician to identify those targets. After we get the plan, we bring the patient back, verify with CT scans that everything is in the perfect position as planned, and then we deliver the treatment.
Does the patient receiving treatment 'feel' anything?
Usually not. In the vast majority of patients it's like getting any other X-ray. Rarely, a patient may get some nausea but in general, they won't feel anything immediately. Based on the total dose, on the amount in the area, patients will have different side effects, based on where the tumors in the area getting treated are.
In general, how many IGRT treatments does the average cancer patient receive?
I'd say on average it's probably about 15 or 20, but the range is very dramatically different. We have a large number of patients treated with one to three treatments and we have a large number of patients who may receive 30 or 35 treatments.
Are outcomes in patients who receive IGRT better than those who have traditional radiation treatments?
I believe we're finding in the preliminary data--and we're actually publishing studies on the use of this technology--is showing that the accuracy and the amount of sparing is absolutely, clearly better in some circumstances. We're getting better positioning for the patients. We have other data that shows patients with less of the normal tissue treated obviously have fewer side effects. Even though I don't know that there's a great deal of specific information on long-term outcomes, I think that preliminary data and the analysis really leads us to the conclusion that this is going to be better. |
