Image-Guided Radiation Therapy (IGRT)
What Is IGRT?
IGRT combines high-resolution imaging technology with radiation therapy to verify the tumor’s exact position before and during each session. Tumors can sometimes move due to breathing, digestion, or changes in weight. IGRT allows us to account for these movements in real time, making treatment safer and more effective.
How IGRT Works
Before each treatment, a quick scan (like a CT or X-ray) is performed.
The scan is compared to the original treatment plan to detect any shifts.
The patient’s position or the radiation beams are adjusted accordingly.
Treatment is then delivered with high precision.
Frequently Asked Questions
Traditional radiation therapy relies on pre-treatment imaging, which may not reflect changes in tumor position during the treatment course. IGRT uses real-time imaging, allowing doctors to adjust the patient’s position or beam direction each day to better target the tumor and protect nearby healthy tissue.
Image-guided radiation therapy (IGRT) uses medical imaging to help provide precise and accurate radiation treatment.
IGRT uses a linear accelerator or cyclotron/synchrotron to produce and deliver radiation therapy. These machines may also have imaging technology to scan the tumor before or during treatment. Your doctor and radiation therapists will compare these scans to the simulation reference images and make adjustments. By adjusting your position and the radiation beams, your doctor and treatment team can more precisely deliver radiation to the tumor while avoiding healthy tissue.
IGRT may use computed tomography (CT), magnetic resonance imaging (MRI), ultrasound (US) or x-ray to scan your tumor. The procedure may place fiducial markers or electromagnetic transponders in or near the tumor. These help the treatment team identify the target area and help position the equipment. See the Fiducial Marker Placement page for more information.
IGRT treats tumors in areas that tend to move, such as the lungs, liver, pancreas, and prostate gland using fiducials, 4D gating or adaptive techniques using high soft tissue resolution imaging. It also treats tumors near critical organs and tissues. Doctors may use IGRT with intensity-modulated radiation therapy (IMRT), proton beam therapy, stereotactic radiosurgery or stereotactic body radiotherapy (SBRT). These advanced forms of high-precision radiotherapy use computers to control x-ray accelerators and deliver precise radiation doses to a tumor or specific areas within it.
Radiation therapy requires a treatment team. The team may include a radiation oncologist, therapeutic medical physicist, dosimetrist and radiation therapists. The radiation oncologist decides which therapies to use, in which area(s), and the optimal therapeutic radiation dose. Radiation therapists obtain images and deliver daily treatments. The radiation oncology nurse provides information about the treatment and possible side effects. The nurse also helps manage any treatment reactions or side effects with supervision and guidance from radiation oncologists.
The radiation oncologist will create and supervise the treatment plan. A radiation therapist will operate the equipment.
What will I feel during and after an IGRT procedure?
Medical imaging prior to or during treatment is painless. During treatment, you may see or hear the equipment moving. Or you may notice an odd smell (the linear accelerator produces ozone). You may even see a colored light during treatment. This is especially true for brain cancer patients. Radiation treatment can cause side effects. These problems may result from the treatment itself or from radiation damage to healthy cells in the treatment area. The number and severity of side effects will depend on the type of radiation, dose, and body part under treatment. Talk to your doctor and/or nurse so they can help you manage them.