title: Fiber-Optic Fabry-Pérot Interferometers for Axial Force Sensing on the Tip of a Needle.
abstract: A range of complex percutaneous procedures, such as biopsy or regional anesthesia, rely heavily on accurate needle insertion. Small variations in the mechanical properties of the pierced tissue can however cause deviations from the projected needle path and can thus result in inaccurate placement of the needle. Navigation of a rigid needle towards the target tissue is traditionally based on the surgeons capacity to interpret small variations in the needle insertion force. A more accurate measurement of these small force variations enables improvement in needle targeting, can potentially aid in enhancing force feedback in robotic needle placement and can provide valuable information on tissue-tool interaction. In this study we investigated several concepts for the design of a force sensor based on a fiber-optic Fabry-Pérot interferometer to measure needle-tissue interaction forces on the tip of a 18 G needle, where special attention was given to concepts for a sensor with (1), an intrinsic low cross-sensitivity to temperature and (2), elementary design and fabrication. Three concepts, using either a quartz capillary, an Invar capillary or a thin polyimide film as the force sensitive element were prototyped and subjected to both static and dynamic testing. The force transducer based on a quartz capillary presented the lowest cross-sensitivity to temperature ( 12 m N / ∘ C) and good accuracy (maximum measurement error of 65 m N /10 N ) in a measurement of static forces. However, limited strength of the sensor is expected to prevent usage of the quartz capillary in small diameter needles. The concepts for a sensor based on an Invar capillary or a thin polyimide film proved a higher cross-sensitivity to temperature ( 50 m N / ∘ C and 220 m N / ∘ C, respectively) and higher maximum measurement error (350 m N /10 N , 800 m N /10 N ), comparable to those of FBG-based sensors reported in literature, but are likely to be more suitable for integration in very small biopsy needles.
authors.affiliation: Department of Physics and Astronomy and LaserLab Amsterdam, Vrije Universiteit Amsterdam, Amsterdam 1081 HV, The Netherlands. s.v.beekmans@vu.nl.
authors.forename: Steven
authors.initials: S
authors.lastname: Beekmans
authors.affiliation: Department of Biomechanical Engineering, Delft University of Technology, Delft 2628 CD, The Netherlands. thomas.lembrechts@gmail.com.
authors.forename: Thomas
authors.initials: T
authors.lastname: Lembrechts
authors.affiliation: Department of Biomechanical Engineering, Delft University of Technology, Delft 2628 CD, The Netherlands. j.j.vandenDobbelsteen@tudelft.nl.
authors.forename: John
authors.initials: J
authors.lastname: van den Dobbelsteen
authors.affiliation: Department of Biomechanical Engineering, Delft University of Technology, Delft 2628 CD, The Netherlands. D.J.vanGerwen@tudelft.nl.
authors.forename: Dennis
authors.initials: D
authors.lastname: van Gerwen
mesh_terms: D004867:Equipment Design; D005336:Fiber Optic Technology / Q000295:instrumentation* / Q000379:methods; D007368:Interferometry / Q000295:instrumentation* / Q000379:methods; D012031:Refractometry / Q000295:instrumentation / Q000379:methods; D013696:Temperature
keywords: Fabry-Pérot interferometer; fiber optic force sensor; low temperature cross-sensitivity; needle-tissue interaction force; tip force sensing