Robinwood Medical Center
11110 Medical Campus Rd.
The John R. Marsh Cancer Center now offers image-guided radiation therapy (IGRT) using fiducial markers for prostate cancer treatment.
IGRT works in conjunction with intensity modulated radiation therapy (IMRT) to increase the precision of radiation treatment. In IMRT, computer-controlled linear accelerators deliver specific amounts of radiation to a tumor without affecting the surrounding tissues. While the patient lies on a table, a linear accelerator machine sends radiation into the tumor. The dosage can vary by shape, depth, and intensity. The John R. Marsh Cancer Center uses the Varian 2100 EX linear accelerator, which targets radiation very precisely, delivering treatment in the exact shape of the tumor.
IGRT enables the linear accelerator to compensate for the patient’s movements during treatment. Something as simple as gas or a full bladder can move the position of the prostate by half an inch—a substantial distance when it comes to radiation therapy. So to treat prostate cancer, three tiny gold markers (about one-tenth of one inch long) are inserted into the prostate. These fiducial markers serve as a fixed standard of reference showing the exact location of the prostate within the patient’s body. The linear accelerator detects the fiducial markers and adjusts the targeting of the radiation beams appropriately, so that the bladder and rectum are not damaged.
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Fiducial Marker Placement
The procedure for placing the fiducial markers is similar to that used for the prostate biopsy, although the marker placement procedure is more comfortable for the patient and has fewer side effects.
The urologist uses a rectal sonogram probe to view the prostate. The probe has a hole in the center, through which the urologist guides several needles, each of which places one marker. The procedure takes just ten minutes.