Technical Note: Angiographic Trans-Arterial Guided Gold Fiducial Placement for Tumor Tracking in Cyber Knife-Based Stereotactic Radiotherapy for Lung Lesions.

Internal gold Fiducials are markers necessary for treatment planning and tracking the movements of target lesions during Stereotactic Radiosurgery . Fiducials are typically required for tumors in the chest, abdomen, pelvis, or other soft tissues. Percutaneous image guided fiducial placement is standard technique for Cyber knife tumor tracking in centrally located lung tumors. Occasionally percutaneous placement can be contra indicated and some patients do not accept percutaneous placement for fear of complications In such situations angiographic trans-arterial placement of gold fiducials can be considered. 2 cases of Trans- arterial fiducial placement at our centre. First case was of a 56 year old lady, with adenocarcinoma of middle lobe of right lung, planned for SBRT. Due to the fear of pneumothorax encountered during prior biopsy, the possibility of Trans - arterial fiducial placement was considered. Second case was of a 52 year old lady with carcinoma endometrium, post treatment, on follow up was found to have a confirmed metastatic solitary lung lesion. Hence SBRT was planned. Due to significant chemotherapy induced thrombocytopenia and altered bleeding parameters, the possibility of Trans-arterial fiducial placement was considered. Procedure was done under local anesthesia for both patients through trans- femoral approach. 5F Sheath was placed in the right femoral vein by Seldingers technique. Pulmonary artery was accessed with a 4F head hunter catheter. Angiogram was performed and lobar arteries supplying the lesion were selectively catheterized . The segmental arteries supplying the lesion were selectively catheterised with 2.7F microcatheter. Through the catheter, gold fiducials of size 8 x 0.5 mm were deployed . In first patient, 3 Fiducials were placed exactly around the lesion. In second patient, 2 fiducials were within the vicinity of the lesion and one migrated post-deployment. No minor or major clinical complications seen. Post procedure CT scans confirmed the position of fiducials and patients further underwent SBRT successfully. Intra-arterial Fiducial placement is an effective alternative procedure in patients with contraindications to percutaneous fiducial placement. It is a relatively safe procedure with no risk of pneumothorax/ haemothorax/ hematoma. However, there is a risk of fiducial migration into peripheral arteries during the procedure.