Patient spesific bolus production using three dimensional printer and dosimetric evalution of the produced material

PURPOSE: In this study, it was researched whether PLA, which is one of the 3D printer raw materials, can be an alternative to SuperFlex bolus materials used in radiotherapy. The advantages and disadvantages of the bolus, which was designed using PLA material, were compared to the superflex bolus. METHODS: On the first phase of the research, the experimental and theorical dose datas that had been obtained from the material were compared to the water phantom datas to make a research on water equivalance of PLA material. The theorical data obtaining was made with Monte Carlo method by the help of GAMOS software and using Acuros XB algorithm on TPS system. For PLA material that had been found to have no water equivalent a HU value was obtained on the treatment planning system with the material's mass density value. On the second phase of the research, three different treatment plans such as treatment with SuperFlex bolus, treatment with PLA bolus and treatment without bolus were created for the target tissue that had been determined on the nose area of the human-like phantom. Treatments were evaluated with D_min,D_max,D_mean values on critical organs, in addition to that on the target tissues V_(98%),V_(95%),V_(2%),CI ve HI parameters were also added to the evaluation. RESULTS: As a result of PDD comparing it was seen that the dose difference between PLA and water surface was 10% depending on the area size. This difference decreased from %1 to the low values as it approached to the maximum dose level. The dose difference increased to the %3 level gradually as getting deeper from the maximum point. The "368 HU" value was obtained for PLA material. In the virtual irradiations on the human-like phantom using SuperFlex, PLA bolus and without bolus D_min%89,6 D_max%105,6 in PTV was evaluated for 0,5 cm PLA bolus. For SuperFlex bolus, D_min%86,5 D_max%105,8 in PTV was evaluated. And for the treatment plan without bolus, the values of D_min%21,9 D_max%119,2 was obtained in PTV. Observing only the target tissues showed that the 0,5 cm PLA bolus had an advantage over SuperFlex bolus with the same thickness. The skin doses were higher on the plan made with PLA bolus than other plans. Evaluations made by using 1 cm thick bolus demonstrated that the dose distributions of target tissue with using of PLA bolus showed similar results as SuperFlex bolus, yet they showed different results in terms of maximum doses. CONCLUSIONS: It was seen that PLA material could be an alternative to SuperFlex bolus. PLA can provide advantages over SuperFlex bolus in terms of dose distribution. If the bolus thickness is not chosen correctly, the maximum dose and dose distributions in PTV may turn into disadvantages. Due to the reason that PLA materials can be varied according to the producing companies, the users should simulate their own PLA material for their clinic. KEY WORDS: Bolus, 3D Printer, Monte Carlo Simulation, Radiation Dose,