Fiber-optic Fabry-Pérot interferometers for force sensing on the tip of a needle

Fiber-optic Fabry-Pérot interferometers for force sensing on the tip of a needle

Lembrechts, T.P.A.

Van den Dobbelsteen, J.J. (mentor)
Van Gerwen, D. (mentor)

Mechanical, Maritime and Materials Engineering

BioMechanical Engineering

BMD

2015-04-30

Physicians use small variations in the needle insertion force to identify tissue properties and detect membrane punctures during needle insertion. Navigation of a needle towards the target tissue, for example to take a biopsy, is often based on detecting these variations in force. Literature shows that presenting physicians force feedback based on forces on the needle tip instead of forces sensed by the physician at the hub of the needle, results in improved detection of membrane puncture events. Measurement of forces on the needle tip is also of interest for other applications like research on needle-tissue interaction forces. The currently studied FBG-based (optical) sensors for the measurement of forces on the needle tip suffer from a cross-sensitivity to temperature, which causes large measurement errors when the needle is inserted into the body of a patient. This thesis investigated several concepts for the design a force sensor based on a fiber-optic Fabry-Pérot interferometer to measure forces on the tip of a core biopsy needle. Special attention was given to concepts for a force sensor with an intrinsic low cross-sensitivity to temperature. Three concepts, using either a quartz glass capillary, an Invar capillary or a thin polyimide film to convert force on the needle tip to a quantity measurable by the Fabry-Pérot interferometer, were investigated in more detail by means of (FE-)modeling and testing of prototypes. Usage of a quartz capillary resulted in a sensor with a very low cross-sensitivity to temperature of 12mN/°C and a good accuracy for the measurement of static forces (maximum observed measurement error of 65mN for a range of 10N). Limited strength of the sensor is however expected to prevent usage of the concept for small diameter needles. Prototypes of concepts using an Invar capillary or polyimide thin film did not perform equally good, although they are better suited for real applications due to better strength, while the latter concept could be suited for the design of a flexible, entirely MRI-compatible polymer needle. Suggestions for methods to improve the measurement accuracy of the latter two prototypes were presented. It was concluded that a triaxial instead of uniaxial force sensor will be required to pursue a very high accuracy by compensating for measurement errors due to transverse forces on the needle tip. Usage of low coherence interferometry was furthermore identified to be better suited than homodyne interferometry to interrogate the FPI-based sensors in most occasions and enable the design of a sensor with an intrinsic low cross-sensitivity to temperature without using highly dimensionally stable but fragile materials like quartz glass.

needle tip
force sensor
fiber-optic
Fabry-Pérot interferometer
cross-sensitivity temperature

http://resolver.tudelft.nl/uuid:47136311-9a81-4960-8c62-a22fa9c1c17d

2018-04-30

Student theses

master thesis

(c) 2015 Lembrechts, T.P.A.