[Clinical application of computer-aided design and rapid prototyping technique for radioactive seeds contained maxillary device].

Objective: To test a new method to manufacture a maxillary applicator containing radioactive seeds for brachytherapy of malignant neoplasms based on computer aided design (CAD) and rapid prototyping (RP).

Methods: Six patients with maxillary malignancy which had eroded the inferior wall of orbit and skull base were included in this study. After excision of the tumors, head CT data of these patients were transmitted into the computer. Three-dimensional digital image of the patient's defected region was then obtained with special software processing based on Mimics 8.11 and Geomagic 7.0 and the resin cast of the defected region was manufactured by rapid prototyping. The elastic obturator was then made on this resin cast which can duplicate the undercut tissue of the defected region. After the obturator was completed, the radiotherapy plan was made. (125)I radioactive seeds were implanted into the tissues, and they were also implanted into the target area of the obturator which was used as a maxillary applicator at the same time. The number of radioactive seeds was then counted and the stability of radioactive seeds was determined by CT examination. All these 6 patients were followed-up for 12 months.

Results: All the obturators had good retention and stability and fitted the designed target tissue very well. (125)I radioactive seeds in the form of the obturator applicator were stable. For all patients, the total number of radioactive seeds used was 189. Among them, 105 seeds, 55.6% of the total, were contained in obturator applicators. After the obturator applicators were used, the amount of radioactive seeds irradiating the target regions was significantly increased when compared with that of before. After follow-up of 12 months, there was no recurrence nor severe complications.

Conclusion: (125)I radioactive seeds contained maxillary applicator made by computer aided design and rapid prototyping can effectively improve the brachytherapy of (125)I when it is used for the post-operation radiotherapy of maxillary malignant tumors.