TIMER (gemelli arT Interstitial Multi-imaging pERineal applicator): Dosimetric analysis of homemade device for interventional radiotherapy (brachytherapy)

Purpose: Interventional radiotherapy (IRT, brachytherapy) for perineal malignancies, such as anal canal cancer, is challenged by complex pelvic anatomy and procedural limitations. Therefore, TIMER® applicator was developed to address these issues, offering innovative and adaptable design, compatible with multimodal imaging (MRI, CT, PET/ CT, US). Material and methods: TIMER® applicator features MRI/CT compatibility, dual anchoring options, and optimized needle layout to improve dose distribution and anatomical conformity. A dosimetric comparison with two commercial applicators was conducted, evaluating dose non-homogeneity ratio (DNR) across varying clinical target volumes (CTVs). Results: The TIMER® applicator demonstrated superior dose uniformity, achieving lower DNR values across most configurations and depths. It outperformed both commercially available templates, except for shallow posterior CTVs, where one applicator showed slightly better performance. Conclusions: The TIMER® applicator enhances dose precision and adaptability in IRT for perineal cancers, outperforming commercial devices in most scenarios. Further refinements and clinical validation will establish its role in advancing IRT protocols.