In simple words: During an open abdominal, pelvic, or retroperitoneal surgery, the surgeon places small markers or a device to help guide future radiation therapy. These markers help target the radiation precisely to any remaining diseased tissue.

The provider places one or more fiducial markers to guide radiation therapy or a dosimeter that can measure the radiation being given to the targeted soft tissue. The provider performs this add-on service at the same time that he performs another open abdominal, pelvic, or retroperitoneal procedure, such as tumor removal. The patient is already appropriately prepped and anesthetized, and the provider has already entered the abdomen to perform another primary procedure such as to excise or debulk an intraabdominal, intrapelvic, and/or retroperitoneal tumor. In this add-on procedure, the provider then places small metal markers, or devices known as fiducials, in the target area that help locate the target tissue in the interstitial space of the intraabdominal, intrapelvic, or retroperitoneal region. He places the fiducial markers to eradicate any residual disease. The markers consist of a preloaded delivery system that the provider uses to place one or more of the fiducials around the tumor site using palpation or imaging guidance. The provider then repeats the procedure as necessary until he places an adequate number of fiducials. The provider may also place a dosimeter, which can measure radiation in the target area. When the procedure is complete, and after achieving hemostasis, the provider removes all instruments and closes the wound in layers.

Example 1: A patient undergoing an open colectomy for colon cancer has fiducial markers placed around the tumor bed to guide post-operative radiation therapy., During an open hysterectomy for uterine cancer, the surgeon places a dosimeter in the pelvic cavity to measure the radiation dose delivered during subsequent brachytherapy., A patient with a retroperitoneal sarcoma undergoes an open resection. Fiducial markers are placed to guide stereotactic radiosurgery following the surgery.

Documentation should include the primary procedure performed, the type and number of fiducial markers or dosimeters placed, the location of placement, and the use of image guidance, if performed. The medical record should also justify the medical necessity of the placement of fiducial markers or dosimeter for radiation therapy guidance.