A digital model individual template and CT-guided 125I seed implants for malignant tumors of the head and neck

摘要

Before implantation, patients underwent CT scanning based on a thickness of 0.75?mm. Data was saved in DICOM format. Patient posture during CT examination was the same as the predicted posture during implantation. The brachytherapy treatment planning system (BTPS, Beijing Atom and High Technique Industries Inc., Beijing, China) software for Windows XP was used to read information from CT images and to construct the implantation plan (Fig.?1A). In the plan, needles were implanted from different directions to avoid bone, major blood vessels and important organs (Fig.?1B). The CT images, including planned information on number, position, and direction of the implant needles, were then exported and saved in DICOM format. The Mimics 10.01 for windows (Materialise, Belgium) was used initially to read CT and needle information, and then used to reconstruct the three-dimensional (3-D) appearance of the head and neck region and implantation needles in the correct positions (Fig.?1C). The 3-D data was then exported to software Geomagic 8.0 (Geomagic Company, USA) in an STL format. The individual template was designed according to the 3-D appearance of the skin using Geomagic software, and ideally covering a marking point, such as the nose, the lower border of mandible, the zygoma or the ear, which could facilitate placement of the template in the correct position (Fig.?1C). The thickness of the template (6?mm in our study) and the diameter of the implantation needles (18G interstitial needles in our treatment) were then determined, and the Boolean minus operation was applied to obtain an image of the individual template that contained the needle information. According to the digital model, the individual template was constructed from the medial light-cured resin using the rapid forming machine Eden250 (Objet Company, Israel). An individual template of the parotid, infratemporal fossa and mandibular ramus regions can be seen in Fig.?1D. Under general anesthesia, the needles were implanted using the individual template and CT guidance, to ensure that all needles were in the expected position and depth, which was calculated in BTPS (Fig.?1E, 1F). Following this, 125I seeds were implanted in the tissues via the needles, in accordance with the implantation plan. Finally, a further CT examination was performed to verify and guarantee that the seeds were distributed in the correct position. CT images of the seeds were used to calculate the D₉₀, V₁₀₀, V₁₅₀ and dosages at organs at risk after treatment by BTPS.