**6.7 Temperature monitoring**

Thermal therapy involves destruction of redundant tissue by heating or freezing without surgery. Examples of thermal therapies include treatment of benign prostatic diseases, ablation therapy of cardiac arrhythmia, microwave induced hyperthermia for radio therapy

<sup>5</sup> http://www.endosense.com/home.html

Optical Fiber Gratings in Perspective of Their Applications in Biomedicine 141

textile is useful not only for patient health monitoring but also for soldiers in battlefields, people in sports and even for general safety of public. In a collaborative work 10 expert groups from 5 EU countries have initiated a novel project, i.e. *Optical Fiber Sensors Embedded into Technical Textile for Healthcare* (OFSETH) to create smart wearable textiles with FBG along with other optical devices for measurements of various vital parameters6. Though preliminary experiments with the textile containing FBGs had been undertaken further investigations are needed for practical implementation of smart textile concept in terms of better integration of the fiber with textile, of different patient profiles and overall

A force sensing robot fingers using embedded FBG sensors and shape deposition manufacturing have been demonstrated recently (Park et al 2008). With their very small size and highly precise real-time measurements FBG sensors have the potential to be a part of surgical robot. Shape-sensing systems can be created by using arrays of FBGs distributed along multicore, singlemode fibers that will help determine the precise position and shape

OCT is an upcoming technology for non-invasive cross-sectional imaging in biological systems with a great potential for morphological assessment of various tissues. OCT acquires very high-resolution images through the detection of backscattered near infrared light with the potential to identify a wide range of pathologies in-vivo. Clinical applications of OCT are constrained by its limited penetration depth in tissue and miniaturized fiber-optic probes are used to image deeper within the body. (McLaughlin &

FBGs with precise Bragg wavelength, narrow spectral bandwidth less than 0.1 nm and high reflectivity are being applied in the OCT systems to calibrate and align the custom-made spectrometer for the spectral-domain optical coherence tomography (SD-OCT) system operating in the 1300-nm wavelength range. The calibration and characterization protocol

Fiber grating based sensors and devices are just beginning to tap the vast opportunity for diagnostics to help in therapeutics as indicated by the large number of ongoing research & development activities mentioned in the previous section. They are enabling acquisition of analytical results on the patient's bedside within a few minutes minus the electromagnetic or other interferences. With the development of technology the possibility of cheaper and portable interrogator systems is within reach and the cost of grating fabrication would come down for bulk fabrication. Also, acceptance by the end users will follow only after the researchers are able to prove that this technology is better than the existing ones through

of medical tools and robotic arms used during minimally invasive/robotic surgery.

performance in real environment. (Grillet et al 2008)

**6.11 Optical Coherence Tomography (OCT)** 

was presented and investigated very recently. (Eom et al 2011)

**6.10 Robotic surgery** 

Sampson 2010)

**7. Conclusion** 

6 http://www.ofseth.org

in the cancer treatment, during which temperature of both diseased and normal tissues should ideally be monitored. Most temperature sensors measure temperature at one point only, whereas FBG sensors because of their multiplexing capability provide temperature distribution during thermal treatment using one probe only. Temperature monitoring of a patient during MRI procedure is crucial in general and in particular to ensure that the implantable devices do not heat up under strong fields of MRI. An FBG probe can be placed inside a NMR machine with high magnetic field for remote temperature measurement.

An FBG based temperature profile monitoring system was first proposed by researchers from UK and Australia using four strain-free FBG array that meets the established medical requirements and tested the feasibility of FBG temperature probe inside a NMR machine with high magnetic field and established its working (Rao et al 1997, 1&2). The first *in-vivo*  trials of such temperature probes incorporating five FBGs along a single fiber were undertaken successfully at the Cancer Research Institute in Perth, Australia by the same group (Webb et al 2000) on rabbits undergoing hyperthermia treatment of the kidney and liver via inductive heating of metallic implants. A distributed FBG sensor system was tested effectively in temperature range of -195.80C to100oC for in-vivo use during freezing of porcine liver, for their mechanical stability and MR compatibility (Samset et al 2001).

FBGs are very useful in cryosurgery for localized cancer treatment, where precision of millimeters matters. It is very critical to monitor exact temperature profile throughout surgical procedure to ensure adequate freezing (-40°C) in the cancerous region but preventing low temperatures in the attached nerve fibers, blood vessels or nearby organs for their safety. An FBG based re-usable multi-point temperature monitoring system was developed recently which can record temperatures in a continuum of either four points at 10-mm intervals, or eight points at 5-mm intervals **(**Gowardhan & Greene 2007, Polascik & Mouraviev 2008).

### **6.8 FBG based manometry catheter**

A research group from Australia has demonstrated multi-element catheter using FBG pressure sensor in in-vivo trials in the human oesophagus for diagnosis of gastrointestinal motility disorders (Arkwright et al 2009). The FBG based catheters had an outer diameter of less than 3 mm and were very flexible in comparison to solid state catheters, allowing easy nasal intubation and relative comfort for the patient during subsequent clinical diagnosis. Also, due to multiplexing capability of FBGs a large number of sensors can be accommodated in a single fiber thus making it possible to extend the total span of the sensing region, with no change in the catheter size. For validation, 10 healthy volunteers were intubated via the nose with both catheter assemblies and asked to perform series of controlled water swallows. The results were directly compared with a commercially available solid state catheter and largely equivalent response was obtained.

#### **6.9 Smart clothing**

Smart clothings have the capability to sense stimuli from the environment, to react and adapt to them. Due to their small size and flexibility fiber optic sensors can be woven into the textile and be an integral part of the smart system. This type of wearable and smart textile is useful not only for patient health monitoring but also for soldiers in battlefields, people in sports and even for general safety of public. In a collaborative work 10 expert groups from 5 EU countries have initiated a novel project, i.e. *Optical Fiber Sensors Embedded into Technical Textile for Healthcare* (OFSETH) to create smart wearable textiles with FBG along with other optical devices for measurements of various vital parameters6. Though preliminary experiments with the textile containing FBGs had been undertaken further investigations are needed for practical implementation of smart textile concept in terms of better integration of the fiber with textile, of different patient profiles and overall performance in real environment. (Grillet et al 2008)
