2.3 125I RSI-BT
All patients underwent standard RSI-BT procedure (Fig 1). Pre-operative CT scans (slice thickness 2.5-5 mm with contrast) was carried out and images were transmitted to Brachytherapy Treatment Planning System (BT-TPS) (Beijing Astro Technology, Beijing, China). The needle-puncture pathway was designed on BT-TPS. Radioactivity and number of seeds were calculated according to prescription doses (PD) design. Individualized template was made by three-dimensional-printing techniques (3D-PT). Finally, a digital information of needles channels on BT-TPS for pre-operative plan was transferred into 3D-pinting software and reconstruction.
Patients were usually positioned supine according to the tumor sites. After the induction of local anesthesia, the operator chose the best layer and angle for needle puncture assisted or not by 3D-PT based on the pre-operative plan and followed by needle insertion. CT scans to verify the needles position and direction, the operator optimized the angle and depth of the needle by real-time CT scan to conform the pre-operative plan. Then, seeds were implanted using a Mick® Applicator (Mick Radio Nuclear Instruments, Mount Vernon, NY, USA) according to pre-plan. Finally, CT was undertaken immediately following seeds implantation to check the actual distribution of 125I seeds and, if necessary, more seeds would be implanted for doses distribution in the targets as pre-plan requirements.