FIBER OPTIC SENSORS (FOS) FOR BIOMEDICAL APPLICATIONS

Abstract: Given their EM immunity, intrinsic safety, small size & weight, autoclave compatibility and capability to perform multi-point and multi-parameter sensing remotely, optical fibers and fiber optic-based sensors are seeing increased acceptance and new uses for a variety of bio-medical applications-from laser delivery systems, to disposable body temperature sensors, to intra-aortic catheter probes. This discussion will review the benefits, needs and applications of optical fiber sensors in the bio-medical field.
The intrinsic physical characteristics of optical fibers make them extremely compatible for their use in biomedical sensing applications. Given the small size of un-cabled optical fibers (< 250 microns) enables them to be inserted directly into hypodermic needles and catheters, so that their use can be both minimally invasive and highly localized. Sensors made with them have the capability to perform multi-point and multi-parameter sensing remotely.
Biomedical Fiber Optic Sensor can be categorized into four main types: physical, imaging, chemical and biological. Physical sensor are used to measure a broad variety of different physiological parameters such as body temperature, blood pressure, respiration, heart rate, blood flow, muscle displacement, cerebral activity, etc. Imaging sensors encompass both endoscope devices for internal observation and imaging, as well as more advanced techniques such as Optical Coherence Tomography (OCT), photo acoustic imaging and others, where internal scans and visualization can be made non-intrusively. Chemical sensors rely on fluorescence, spectroscopic and indicator techniques to measure and identify the presence of particular chemical compounds and metabolic variables (pH, blood oxygen, glucose, etc.), detecting specific chemical species for diagnostic purposes, as well as monitoring the body's chemical reactions and activity for diagnostic and therapeutic applications. Biological sensors tend to be more complex and rely on biologic recognition reactions-such as enzyme-substrate, antigen-antibody, or ligand receptor- to identify and quantify specific biochemical molecules of interest.
The biomedical sensing market represents a lucrative and growing opportunity for specialty optical fibers, particularly for large volumes of disposable sensing probes. This is so, due to a combination of factors and trends. On the one hand, there is a demand for more patient monitoring devices due to an increasing older population, living longer life spans and requiring health care. On the other hand, there is a trend towards the practice of minimally invasive surgery (MIS) which in turn calls for a variety of minimally invasive medical devices as well as single-use, disposable sensors of small size that can be incorporated into catheters and endoscopes-an ideal fit for fiber optic sensors. Furthermore, there is also an unquestionable opportunity for FOS as EMI compatible sensors to take vital signs during use of MRI (and related techniques), as well as RF treatments.

Dr. Yousaf Khan ( UET, Kohat Campus )