Fiber-top controlled adaptable stiffness needle
In the Netherlands alone, each year more than 50.000 percutaneous procedures are performed for treatment or removal of tissue from possibly diseased organs. Erroneous needle targeting can have disastrous effects for the patient. Also, in local treatment of cancer by means of radiofrequency ablation, cryoablation, or radioactive seeds, erroneous targeting can result in both reduced effectiveness of the therapy and damage to healthy tissue.
In this project we will develop an instrument that addresses this issue through the first-ever combined use of two mechanical devices: a needle with adaptable stiffness and a probe that can identify tissues via real-time measurements of their stiffness. For instance, malignant cells may be missed due to inaccurate positioning of the biopsy needle.
WP 3.1.1: Design of needles with fiber-top indenter (VU)
We will develop an instrument consisting of a needle tip with an optical fiber interferometric technique to monitor needle advancement through different types of tissue. When the needle encounters the interface between two layers a fiber-top indenter inside the needle is protruded and used to accurately measure the stiffness of the tissue that is about to be perforated. The fiber-top indenter consists of a micromachined cantilever, fabricated on top of an optical fiber. Upon contact with the tissue, the cantilever bends, depending on the stiffness of the tissue. By coupling light from the opposite end of the fiber, the cantilever position is assessed. Measurements of cantilever bending and needle motion will be combined to accurately assess tissue stiffness.
Deliverable: A fiber-top indenter allowing local tissue stiffness measurements at the tip of the needle, allowing analysis of the mechanical properties of the tissue layers in front of the needle.
WP 3.1.2: Design of adaptable stiffness needles (TUD)
To accurately maneuver flexible needles through soft tissue one must account for variations in tissue stiffness, affecting needle-tissue interaction and thus needle deflection. We will design a needle with adaptable stiffness to compensate for such tissue inhomogeneity. The needle will consist of a flexible shaft with a fully actuated tip based on a miniature cable-driven steerable mechanism previously developed at TUD. The stiffness of both the shaft and the needle steerable mechanism can be adapted by adjusting the tensioning of the cables incorporated in the needle. Miniaturized deflection sensors based on Fiber Bragg Grating (FBG) technology will be used for real-time sensing of needle configuration, and dedicated motors and linear stages for inserting the needle into the tissue and controlling its stiffness.
Deliverable: A needle device allowing active manipulation of needle stiffness irrespective of the material properties and diameter, which enables the needles to accurately puncture tissue layers with varying properties. Further, FBG sensors provide real-time information about needle motion, which is essential for obtaining the tissue stiffness measurements.
WP 3.1.3: Fiber-top control of adaptive needle-tissue interaction (VU, VUmc, TUD)
We will develop an instrument based on the combination of cutting edge technologies of WP 3.1.1 and 3.1.2 to adapt, in real time, the instrument mechanical properties to those of the tissue addressed. Indentation data, known to provide accurate information on the Young modulus of the indented sample, will be used to adjust the stiffness of the needle at the level requested for optimal tissue perforation. Furthermore, they will provide clinical information on the tissue itself. As needle-tissue interaction is a function of several system variables such as needle stiffness, insertion speed, and the tissue properties, pre-clinical evaluation experiments will be conducted on human cadavers and soft-tissue simulants to characterize these interactions.
Deliverable: A device enabling providing continuous adaptation of the interaction between the needle and the tissue to improve the accuracy in needle maneuvering. The opportunity to identify the mechanical properties of the tissue will improve the ability to verify appropriate needle placement. The developed technologies can be applied to a class of continuum needles used in the context of percutaneous interventions.