These two treatment options require taking a series of x-ray images are taken in order to correctly position the patient to within a millimeter of accuracy. This is done by either IGRT or CBCT. IGRT and CBCT technology allows the therapist to ensure that the target is in the same position every treatment session.
IGRT is not another form of treatment; it signifies the ability to visualize the tumor before, during, and in between treatments. Two x-rays are taken 90 degrees apart and then compared to images created from the initial CT scan.
The images can then be aligned using the bony anatomy or surgically implanted fiducial markers. There are several types of fiducial markers that include gold seeds, coils, and radio-frequency identification markers. IGRT can be used in conjunction with IMRT treatments for an accurate treatment.
CBCT is another form of imaging a patient before treatment. In regular IMRT imaging, two 2-D images are taken and reviewed. While doing CBCT, multiple images are taken in an arc rotation around the patient. Those images are reconstructed as a 3-D set of images that resemble a CT image. Those images can be manipulated in a way to look at each angle of the scanned area.