Lesion Localization Before SBRT (Fiducial Placement)

Background and indications

Fiducial marker placement is an image-guided percutaneous procedure to mark a tumor for subsequent stereotactic body radiation therapy (SBRT), cyberknife, or proton therapy. Fiducials serve as landmarks for the robotic treatment guidance system, enabling real-time tumor tracking and precise irradiation despite respiratory motion.

Most common locations are lung, liver, pancreas, prostate, lymph nodes, and bone.

Pre-procedure assessment

Assessment includes recent CT of the treatment area, coagulation panel, and coordination with the radiation therapist (optimal number and positioning of fiducials, minimum distance constraints between markers). Typically, 2-4 fiducials are placed around or within the tumor.

Procedure

Under local anesthesia (± sedation), a fine needle (18-19G) is inserted under CT guidance to the target site. A fiducial (small 3-6 mm gold or platinum cylinder) is deposited through the needle. The operation is repeated for each fiducial. A control CT verifies correct positioning. The procedure takes 20-40 minutes.

Results and scientific evidence

Technical success rate is 95-99%. Fiducial migration rate is 5-10%, generally without clinical consequence (remaining fiducials suffice for guidance). Fiducial-guided stereotactic radiotherapy achieves 1-2 mm targeting precision.

Risks and complications

Pneumothorax (10-20% for lung locations, 3-5% requiring drainage), minor local hemorrhage (5-10%), fiducial migration (5-10%). Major complications are rare (< 2%).

Recovery

Same-day discharge in most cases (except pneumothorax). Radiotherapy is planned 7-14 days after placement to allow fiducial stabilization.

Practical information

The procedure is performed as an outpatient or short inpatient stay depending on the case. It is performed by an interventional radiologist, in coordination with the radiation therapist.