Flexible Needle Insertion in Soft Tissue

Flexible needle insertion in soft tissue encompasses the design, control and navigation of slender instruments that can bend and steer through deformable biological structures. By exploiting asymmetric tip geometries or external actuation methods, researchers aim to guide needles around critical anatomy, reduce tissue damage and improve targeting accuracy in minimally invasive interventions. Key challenges include modelling needle–tissue interaction forces, predicting needle deflection and ensuring reliable imaging and feedback during real-time insertion. Advances in computational methods, such as finite‐element modelling and machine‐learning-based path planning, alongside innovations in sensor integration and electromagnetic actuation, have expanded the workspace and adaptability of steerable needles. Practical applications range from neurosurgical drug delivery and biopsy to catheter navigation in interventional radiology. The global significance lies in improving procedural outcomes, shortening recovery times and enabling complex trajectories that are not feasible with rigid instruments.

Research from Nature Portfolio

Recent studies have introduced an ultrasound probe combining focused and unfocused elements with an integrated optical hydrophone to achieve three-dimensional needle tip tracking with submillimetre accuracy. In vivo demonstrations in spinal and uterine models highlighted the ability to co-register tracked positions with B-mode images, potentially enhancing procedural safety and workflow compatibility. Another work proposed an electromagnetic actuation system for needle steering in soft phantoms, overcoming limitations of buckling, torsion and restricted curvature by remotely controlling the shaft without manual rotation. This approach yielded improved bending radii and workspace, signalling promise for future clinical translation. Foundational research has also elucidated how bevel-tip geometry and pre-curving influence the ratio of axial to radial forces during tissue penetration, informing new tip designs that achieve predictable curvature and reduced variability in deflection.

Flexible Needle Insertion in Soft Tissue publication trend

The graph below shows the total number of articles in flexible needle insertion in soft tissue across all publications each year (not limited to Nature Index journals).

Technical terms

Steerable needle: A needle designed with an asymmetric tip or external actuation to enable controlled curvature during insertion.

Bevel-tip: An obliquely cut needle tip that generates lateral force causing the shaft to deflect in a predictable direction.

Curvature: The amount by which a needle’s trajectory deviates from a straight line, usually expressed as the reciprocal of the radius of curvature.

Finite-element method: A numerical technique for approximating mechanical behaviour by subdividing a domain into discrete elements.

Force feedback: The provision of tactile or haptic information to an operator or control algorithm based on measured interaction forces.

Phantom: A synthetic material or composite used to mimic the mechanical properties of soft tissue in experiments.

Reinforcement learning: A machine-learning paradigm in which an agent learns optimal actions by trial and error to maximise a reward signal.

References

1. A Heuristically Accelerated Reinforcement Learning-Based Neurosurgical Path Planner. Cyborg and Bionic Systems (2023).
2. Force Modeling, Identification, and Feedback Control of Robot-Assisted Needle Insertion: A Survey of the Literature. Sensors (2018).
3. Looking beyond the imaging plane: 3D needle tracking with a linear array ultrasound probe. Scientific Reports (2017).
4. Magnetic Needle Steering in Soft Phantom Tissue. Scientific Reports (2020).
5. The influence of tip shape on bending force during needle insertion. Scientific Reports (2017).
6. An adaptive finite element model for steerable needles. Biomechanics and Modeling in Mechanobiology (2020).