Implanting Two Fiducials into the Liver with Single Needle Insertion Under CT Guidance for CyberKnife® SBRT

Abstract

Purpose We implanted four to six fiducial markers before treating liver tumors with CyberKnife® to allow image-guided positioning before treatment and real-time tracking during treatment. In the conventional implanting technique, a needle insertion is required to place each fiducial, i.e., patients would receive four to six needle punctures. To improve efficiency and reduce the time required for the procedure, not to mention the pain and risks of fiducial implantation, we invented a technique whereby two fiducials are implanted with each needle insertion. Methods and Materials Liver tumors constitute the most common disease treated at our radiotherapy center. From August 2011 to July 2012, 429 patients with liver tumors underwent fiducial implantation with the technique of one-needle insertion placing two fiducials at a time. Ages varied 19–74 years old. In total, 1252 fiducials were implanted with this technique. For the new technique, an initial CT image of the tumor was used to determine the implanting depth and angle of the first fiducial marker. The first fiducial was placed using an 18-gauge needle, and the needle stylet and set remain stationary for 3–5 min, after which it was slowly pulled 3–5 cm out, and then the second fiducial was released. Another image of the fiducials was acquired to assess the distance between the fiducials, their angle with respect to each other, and their compliance with the requirements of fiducial placement before continuing the procedure. Results Among the 1252 fiducials implanted with the technique, 18 (1.44 %) had a distance smaller than 20 mm between each other, 24 (1.92 %) were collinear at 45^° vantage point, 17 (1.04 %) migrated to other organs, and the success rate was 95.28 %. With this technique, 626 punctures were required whereas 1252 punctures would have been needed with the conventional technique. Besides, implanting with a 35^°–5^° angle makes fiducials collinear in the 45^° direction. For some patients, for whom the two-fiducial insertion technique required a puncture deeper than 5 cm, the fiducials were inserted one by one. Conclusion Dual fiducial insertion doubles the implanting efficiency and halves the number of punctures so that the costs and risks are both reduced. The distance between fiducials being smaller than 20 mm and collinear fiducials at the 45^° angle direction are the most common complications affecting success rate.