Image-Guided (IGRT)
Image-guided radiation therapy (IGRT) uses imaging devices contained in the treatment machine to create images that pinpoint the exact size, location and coordinates of the radiation beam before it strikes the target.
In the past, oncologists have had to compensate for patient or tumor movement by making the radiation beam larger, exposing a significant amount of healthy tissue to radiation. With IGRT, two robotically controlled "arms" capture CT, fluoroscopic and X-ray images to pinpoint the position of the internal target prior to treatment. This increased precision may allow for higher doses of radiation to be administered—ultimately leading to higher cure rates.
Fiducial Markers
Used in IGRT, fiducial markers are implantable reference points (small cylinders) used in the registration of space within a patient's body. The marker's position within a patient's body is used as an anchored point-of-reference in calculating position within an otherwise changing field of view. A fiducial marker has a sealed cavity for the introduction of an imaging agent that can be detected by computed tomographic imaging (CT), magnetic resonance imaging (MRI), other imaging modes or a combination of modes. These markers may be permanent or temporary and readily detachable from their anchor site.
On Board Imaging
On board imaging (OBI) is a technology that employs three different methods of imaging. The imaging equipment is attached to the treatment equipment, so that the patient doesn't need to be moved between imaging and treatment. In OBI, imaging is performed immediately before therapy once, ensuring that the patient and the tumor are at the same position as originally planned. One type of imaging is known as Conebeam CT (CBCT), a new form of CT scan. CBCT makes 3D, 360° CT images of the body before or after the delivery of treatment using less radiation than older CT scanners. CBCT is especially useful for imaging cancers of the head, neck, prostate, lungs, pancreas and cervix.