| Objective Radiation therapy is an important part of comprehensive series of oral cancer treatment. High incidence of radioactive side effects such as mucositis, xerostomia and dysgeusia, seriously affected the quality of life of patients. Dental stent has a protective effect on normal tissues. However, many deficiencies in production materials and production process of dental stent limited its widespread in clinical promotion. For these reasons, the present study attempts to construct individual oral radiotherapy stent by use of new technology of 3D printing, and to prove its feasibility and preliminary clinical evaluation in oral cancer radiotherapy.Methods1. Construction of 3D printed dental stent: we selected suitable metal markers after testing the portal images of metal balls; geometric models were quickly constructed based on application of CT imaging and Mimics software, then entity models were printed out by use of 3D printer. Depending on the anatomical location of the lesion, 3D printed dental stent was designed into two types:one separating the upper and lower,the other separating left and right. Design principles were elaborated, respectively.2. Position verification of 3D printed dental stent: six patients with dental stent were subjected to radiotherapy. Image registration based on bony landmarks and metal tags was separately carried out using Ti GRT IVS system before radiotherapy; once every two weeks, a total of three times. Through comparison and analysis registration errors of portal images and digitally reconstructed radiograph, we can understand the relative position of 3D printed dental stent with the head. So the stability and feasibility of application were proved.3. Clinical evaluation of of 3D printed dental stent: eight tongue cancer patients underwent IMRT were enrolled in this study. The two groups with and without oral stent were statistically compared. Through the analysis of conformal index, homogeneity index,exposure dose of different organs at risk and treatment efficiency, we attempts to make clear its protective effect on adjacent normal tissue.Results1. Portal images of steel balls with different specifications show: metal marker with diameter 3mm was more clear. 3D printed dental stent can be designed with diverse form and function.2. Position verification results show that mean of registration errors on the two methods(based on metal tags and bony landmarks) is less than 1mm. The difference of coordinate values in three directions X, Y, Z axis was not statistically significant(P>0.05).3. Evaluation results show, compared with the trial group, the execution efficiency(numbers of segments and MUs), conformal index and homogeneity index, and dose distribution of organs at risk(spinal cord, throat and bilateral parotids) were no significant difference. Dmax and Dmean of lip, cheek, hard palate and soft palate, V40 of soft palate in the experimental group significantly decreased. There is a statistically significant difference(P <0.01).Conclusions1. 3D printed dental stent has the following characteristics: high modeling efficiency,high model accuracy, individual design, digitally stored easy for repeated printing,placement of markers for image registration. In this study, the use of CT images and Mimics software successfully constructed geometric model, then solid model produced using 3D printing technology, which opens up a new way for the production of dental stent.2. Location validation studies demonstrated the stability of 3D printed dental stent is good, so the application in oral cancer radiotherapy is feasible, which laid a foundation for further study of its clinical value.3. In patients with tongue carcinoma treated postoperatively with intensity-modulated radiotherapy, the application of 3D printed dental stent can significantly reduce radiation dose and volume of organs at risk(upper lip, cheek, hard palate and soft palate), which may alleviate side effects such as oral mucositis, dry mouth. |
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