The OncoReach Stylet for Brachytherapy: Design Evaluation and Pilot Study

2026-01-20

AI Summary

This study addresses the limited accessibility of conventional straight-needle interstitial brachytherapy in cervical cancer, which is constrained by linear trajectories and struggles to reach lateral targets via minimally invasive approaches. To overcome this, the authors propose OncoReach—a handheld, tendon-driven steerable stylet compatible with standard 15G/13G needles. The design incorporates an asymmetric spherical joint and disc structure to enhance bending compliance while preserving axial rigidity, coupled with a dual-tube Cosserat rod model for accurate deflection prediction. Experiments using patient-derived, multi-material uterine-pelvic phantoms demonstrate that the system enables precise targeting of the most lateral lesions through a medial entry point, substantially expanding both the therapeutic reach and the potential for minimally invasive intervention.

Technology Category

• Intelligent Robots: Manipulation
• Machine Learning: Calibration & Uncertainty Quantification
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments
• Responsible Web: Machine-in-the-loop, human agency and autonomy

Abstract

Cervical cancer accounts for a significant portion of the global cancer burden among women. Interstitial brachytherapy (ISBT) is a standard procedure for treating cervical cancer; it involves placing a radioactive source through a straight hollow needle within or in close proximity to the tumor and surrounding tissue. However, the use of straight needles limits surgical planning to a linear needle path. We present the OncoReach stylet, a handheld, tendon-driven steerable stylet designed for compatibility with standard ISBT 15- and 13-gauge needles. Building upon our prior work, we evaluated design parameters like needle gauge, spherical joint count and spherical joint placement, including an asymmetric disk design to identify a configuration that maximizes bending compliance while retaining axial stiffness. Free space experiments quantified tip deflection across configurations, and a two-tube Cosserat rod model accurately predicted the centerline shape of the needle for most trials. The best performing configuration was integrated into a reusable handheld prototype that enables manual actuation. A patient-derived, multi-composite phantom model of the uterus and pelvis was developed to conduct a pilot study of the OncoReach steerable stylet with one expert user. Results showed the ability to steer from less-invasive, medial entry points to reach the lateral-most targets, underscoring the significance of steerable stylets.

Problem

• brachytherapy
• cervical cancer
• steerable needle
• interstitial brachytherapy
• surgical planning

Innovation

• steerable stylet
• interstitial brachytherapy
• tendon-driven mechanism
• Cosserat rod model
• patient-derived phantom