Development and Validation of the Augsburg Nasopharyngeal Applicator: Enhancing Efficacy in Nasal Route Brachytherapy.

Purpose: This study evaluates the Augsburg Nasopharyngeal Applicator (ANA), a novel nasal brachytherapy device designed for early-stage nasopharyngeal carcinoma (T1-T2 stages). ANA leverages nasal anatomy to overcome limitations of oral applicators, optimizing tumor targeting while sparing adjacent tissues, such as the soft palate and oral mucosa. Methods and Materials: ANA was developed using sagittal computed tomography-based anatomic measurements and computer-aided design modeling. Structural integrity was validated through nonlinear finite-element analysis, mechanical stress testing (including Euler buckling tests), and displacement testing (30 min vibration at 5 Hz with 2 cm amplitude). Dosimetry was verified using radiochromic film with 3%/3 mm gamma analysis criteria, following the TG-43 formalism for dose calculation. Insertion feasibility was assessed in a postmortem model under institutional autopsy protocols. Results: ANA (with nylon 6/6 catheter) withstood displacements up to 30 mm without failure. Simulated motion tests demonstrated positional stability (<1 mm displacement). Dosimetry achieved a 97.5% gamma pass rate (clinical acceptability threshold: 95%), with the 20 mm curvature configuration reducing soft palate doses by >50% compared to standard oral applicators (eg, Rotterdam design). Postmortem insertion was completed in 10 min, with endoscopic confirmation of positioning accuracy within 1 mm. Conclusions: ANA demonstrates precise positioning, mechanical stability under simulated physiologic motion (<1 mm displacement), and clinically significant dose sparing (>50% reduction to the soft palate with the 20 mm curvature configuration). Its nasal approach and anatomic adaptability position it as a promising alternative to oral applicators. These proof-of-concept findings support the need for phase 1/2 clinical trials to evaluate safety and efficacy in patients.