Three-dimensional (3D) printing technique has been improving the industrial process from uniform pipeline production procedure in manufacture into individualized production with distributed network. 3D printing technique also provokes these changes in the field of medicine, especially in orthopedics, stomatology and radiology. The role of 3D printing technique has been increasingly highlighted in tumor radiotherapy. Current studies and application mainly focus on personalized tissue compensato (bolus), brachytherapy (high-dose post-loading and particle implantation therapy), 3D printing personalized phantom and individualized fixtures, etc. In this article, research progresses on the application of 3D printing technique in radiotherapy at home and abroad were reviewed.

Background Dimethyl sulfoxide(DMSO) is a commonly used adjuvant to promote testing drug solubility to prepare multi-levels testing drug concentrations.DMSO is cell type-dependent cytotoxic and its toxicity can interfere the testing drug evaluation.Determining its safe concentration on commonly used cell types is important for ocular drug development.Objective This study was to determine the minimal toxic concentration of DMSO for in vitro ocular cell lines in a simulated drug screening setting.Methods Retinal pigment epithelial (RPE) cells were isolated from one pigmented rabbit and primarily cultured.Human RPE cell strain (ARPE19),scleral fibroblasts line (S75-Fron),human Müller cell line (MIO-M1),human lens epithelial cell line (HLEC),human choroidal melanoma cell line (OCM-1),human umbilical endothelial cell (HUVEC) and human HeLa cell line (HELA) were cultured.Different concentrations of DMSO (1.6％,1.0％,0.8％,0.4％,0.2％ and 0.1％) were prepared with 160 μl DMSO solution and 9.84 ml RPMI1640 (or DMEM/F12 or DMEM) containing 2％ fetal bovine serum.Different concentrations of DMSO were added in medium for 96 hours,and the and viability (absorbance) of the cells was detected using MTS to evaluate the cytotoxicity of DMSO.Results Rabbit primary RPE cells showed the yellow-green fluorescence for cytokeratin(CK) and HMB45 red fluorescence for S100.The viability of the cells was gradually declined as the increase of DMSO dose,showing significant differences in ARPE19,S75-Fron,HLEC,OCM-1,HUVEC and primary RPE cells (all at P＜0.05),and when DMSO concentrations were ≥ 0.8％,the cell viabilities were significantly lower.But no significant difference was found in MIO-M1 cells among different doses of DMSO (F=0.830,P=0.547).The minimal toxic concentration of DMSO for ARPE19,HUVEC,HELA,HLEC,MIO-M1,OCM-1,primary RPE cells and S75-Fron was 0.8％,0.1％,0.8％,＞1.6％,＞1.6％,0.2％,0.2％,0.2％,respectively,and HUVEC was more sensitive to the cytotoxicity of DMSO (P=0.02),and MIO-M1 was the least sensitive to DMSO (P =0.39).The viability of HUVEC and primary RPE cells went down with the increase of DMSO dose,and S75-Fron viability started to decline in 0.1％ DMSO and then stabilize with the higher concentrations until 1.6％ DMSO at which the viability showed further decline.Conclusions The tolerability of ocular cells in vitro to DMSO varies depending on the cell types.The minimal toxic concentration ranged from 0.1％ to 1.6％.The result suggests that a concurrent DMSO control should be set up along with the testing compound.

Objective To apply 3D printing technology to fabricate patient-specific silicone tissue compensators for the chest wall and compare the advantages and clinical characteristics between conventional bolus and 3D-printed PLA materials. Methods The chest wall data of two breast cancer patients undergoing mastectomy were obtained based upon the CT images. A patient-specific 3D printing silicone rubber bolus (3D-SRB) was designed and fabricated. The conformability of 3D-SRB,3D-PLA and conventional bolus to the chest wall were validated. Ecipse8. 6 planning system was adopted to statistically compare the dosimetric parameters of virtual plan with those after using three tissue compensators. Results The 3D-SRB was successfully designed and fabricated with a similar hardness to conventional bolus. During the process of validating conformability and radiotherapy planning,3D-SRB and 3D-PLA were superior to conventional bolus in terms of conformability to chest wall and planning dosimetric distribution.3D-SRB was advantageous in repeatability, conformability and comfortable experience compared with 3D-PLA. Regarding dosimetric parameters,3D-SRB yielded the highest repeatability with the virtual plan, followed by 3D-PLA and conventional bolus. Conclusion It is applicable to utilize 3D-SRB as the patient-specific compensators for the chest wall,which is of significance in clinical practice.