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.