Real-time thickness measurement of biological tissues using a microfabricated magnetically-driven lens actuator
- 215 Downloads
A fiber optic confocal catheter with a micro scanning lens was developed for real-time and non-contact thickness measurement of biological tissue. The catheter has an outer diameter and rigid length of 4.75 mm and 30 mm respectively and is suitable for endoscopic applications. The catheter incorporates a lens actuator that is fabricated using microelectromechanical systems (MEMS) technology. The lens is mounted on a folded flexure made of nickel and is actuated by magnetic field. Thickness measurements are performed by positioning the catheter in front of the tissue and actuating the lens scanner in the out-of-plane direction. A single-mode optical fiber (SMF) is used to deliver a 785 nm laser beam to the tissue and relay back the reflected light from the tissue to a photomultiplier tube (PMT). When the focal point of the scanning lens passes tissue boundaries, intensity peaks are detected in the reflecting signal. Tissue thickness is calculated using its index of refraction and the lens displacement between intensity peaks. The utility of the confocal catheter was demonstrated by measuring the cornea and skin thicknesses of a mouse. Measurement uncertainty of 8.86 µm within 95% confidence interval has been achieved.
KeywordsMicroelectromechanical systems Confocal measurements Magnetic actuation Endoscopy Tissue thickness measurements
The authors wish to thank Jianhua Zhao and Wei Zhang from BC Cancer Agency and Keqin Chen from the Mechanical Engineering Department at the University of British Columbia for their contribution in performing thickness measurement experiments. Mu Chiao is supported by the Canada Research Chairs Program. This project was supported by the Canada Foundation for Innovations (CFI), the Natural Sciences and Engineering Research Council (NSERC) of Canada, and the Canadian Institutes of Health Research (CIHR grant #: MOP – 102672).
- N. Ehlers, T. Bramsen, S. Sperling, Acta ophthalmol 53, 34–43 (1975)Google Scholar
- C.Y. Tan, B. Statham, R. Marks, P.A. Payne, Br J Dermatolo 106, 657–667 (1982)Google Scholar
- H.F. Li, W.M. Petroll, T. Møller-Pedersen, J.K. Maurer, H.D. Cavanagh, J.V. Jester, Oxf. Univ. Press, 1996, pp. 214–221Google Scholar
- S.V. Patel, J.W. McLaren, D.O. Hodge, W.M. Bourne, Investig Ophthalmol Vis Sci 42, 333–339 (2001)Google Scholar
- N.M. Ziebarth, F. Manns, J.M. Parel, J Phys 38, 2708–2715 (2005b)Google Scholar
- S. Kwon, V. Milanovic, L.P. Lee, Proc. Solid-State Sens. and Actuator Workshop, Hilton Head Isl., SC, 2002Google Scholar
- C.P.B.Siu, H. Wang, H. Zeng, M. Chiao, Proc. 21th IEEE Int. Conf. on Micro Electromec. Syst. (2009)Google Scholar
- H. Toshiyoshi, W. Piyawattanametha, C.T. Chan, M.C. Wu, IEEE/ASME J. Micro Electromec Syst 10, 205–214 (2001)Google Scholar
- R. A. Conant, R. S. Muller, Proc. ASME Int. Mech. Eng. Cong. and Expo. (1998)Google Scholar
- G. Rizzoni, in The CRC Handb. of Mech. Eng., ed. By F. Kreith, D.Y. Goswami (CRC Press, 2005) Ch. 5.Google Scholar
- G. Martin, Keck Microscopy Facility. (Univ. of Washington, 2007), http://depts.washington.edu/keck/leica/pinhole.htm , Accessed 20 August 2010
- W.S. Rasband, ImageJ, Natl. Inst. of Health, Bethesda, Maryland, USA, http://rsb.info.nih.gov/ij/, 1997–2010.