The OncoReach Stylet for Brachytherapy: Design Evaluation and Pilot Study

TL;DR

This study introduces the OncoReach steerable stylet for brachytherapy, demonstrating its design, modeling, and pilot testing to improve tumor targeting in cervical cancer treatment.

Contribution

The paper presents a novel steerable stylet compatible with standard needles, including design evaluation, modeling, and a pilot study showing its clinical potential.

Findings

The steerable stylet can reach lateral targets from medial entry points.

Design parameters like spherical joint placement affect bending compliance.

The prototype enables manual steering in a phantom model.

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.