Fiducial markers

Fiducial markers are bits of metal the size of a grain of rice that are often placed around a gastrointestinal tumor before radiation therapy. The fiducial markers show up on images (such as X-rays) to better pinpoint a tumor. Because organs in the body shift around when we move, fiducial markers permanently mark the tumor and help make sure radiation is aimed precisely. That way, radiation can be as exact as possible, affecting just the cancerous cells and minimizing harm to healthy tissue. Using imaging to help guide radiation is called image-guided radiation therapy (IGRT).

What to expect from fiducial markers

Typically, three to six fiducial markers are placed around a tumor during an outpatient procedure called endoscopic ultrasound (EUS). A thin, flexible tube (endoscope) is inserted through the mouth, down the esophagus, past the stomach and into the area of the tumor. A thin needle is inserted through the tube into the tumor to place the fiducial markers. The endoscope contains a tiny camera, which transmits pictures to a monitor so a doctor can see inside as the fiducial markers are placed.

You must wait a week or so after having fiducial markers placed before beginning radiation therapy.