Purpose: To design a novel high-dose-rate intracavitary applicator which may lead to enhanced dose modulation in the brachytherapy of gynecological cancers. Material and methods: A novel brachytherapy applicator, auxiliary equipment and quality control phantom were modeled in SketchUp Pro 2017 modeling software and printed out from a MakerBot Replicator Z18 three-dimensional printer. As a printing material polylactic acid (PLA) filament was used and compensator materials including aluminum, stainless-steel and Cerrobend alloy were selected according to their radiation attenuation properties. To evaluate the feasibility of the novel applicator, two sets of measurements were performed in a Varian GammaMed iX Plus highdose rate iridium-192 (192 Ir) brachytherapy unit and all of the treatment plans were calculated in Varian BrachyVision treatment planning system v.8.9 with TG43-based formalism. In the first step, catheter and source-dwell positioning accuracy, reproducibility of catheter and source positions, linearity of relative dose with changing dwell times and compensator materials were tested to evaluate the mechanical stability of the designed applicator. In the second step, to validate the dosimetric accuracy of the novel applicator measured point dose and two-dimensional dose distributions in homogeneous medium were compared with calculated data in the treatment planning system using PTW VeriSoft v.5.1 software. Results: In mechanical quality control tests source-dwell positioning accuracy and linearity of the designed applicator were measured as ≤ 0.5 mm and ≤ 1.5%, respectively. Reproducibility of the treatment planning was ≥ 97.7% for gamma evaluation criteria of 1 mm distance to agreement and 1% dose difference of local dose. In dosimetric quality control tests, maximum difference between measured and calculated point dose was found as 3.8% in homogeneous medium. In two-dimensional analysis, the number of passing points was greater than 90% for all measurements using gamma evaluation criteria of 3 mm distance to agreement and 3% dose difference of local dose. Conclusions: The novel brachytherapy applicator met the necessary requirements in quality control tests.

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Purpose: To evaluate dosimetric differences between point-based 2-dimensional (2D) vaginal brachytherapy (VBT) treatment planning technique and volume-based 3-dimensional (3D) VBT method for endometrial cancer (EC).Material and methods: Ten patients with uterine-confined EC treated with VBT were included in this study. All patients received 27.5 Gy in 5 fractions. Three different treatment plans were performed for each patient: plan A for dose prescribed to the entire vaginal wall thickness delineated via computed tomography guidance, plan B for dose prescribed to the vaginal mucosa/cylinder surface, and plan C for dose prescribed to 5 mm beyond the vaginal mucosa/cylinder surface. Dose-volume histograms (DVH) of treatment volumes and organs at risk (OARs) were evaluated and compared.Results: DVH analysis of target volume doses (D 100 , D 95 , and D 90 ) showed a significant difference between plan A and plan B (p = 0.005), and plan B was found lower. D 100 for plan C was significantly higher than plan A (p = 0.009), but for D 95 and D 90 , no statistically significant difference was found (p = 0.028 and p = 0.028, respectively). In terms of OARs doses, including vagina, rectum, bladder, and sigmoid, D 2cm 3 doses were significantly higher in plan A than plan B (p = 0.009, p = 0.009, p = 0.005, and p = 0.005, respectively). All these doses were also significantly lower than in plan C (p = 0.005, p = 0.012, and p = 0.013, respectively), except for sigmoid (p = 0.155).Conclusions: In this dosimetric analysis, we have shown that the volume-based 3D VBT technique provides the ability to balance the target dose against the sparing of OARs. Therefore, in the new modern 3D treatment era, instead of normalization of the dose to standard reference points, customized 3D volume-based VBT planning should be recommended.