This PDF file contains the front matter associated with SPIE Proceedings Volume 10872 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Epidural anesthesia is the most diffused clinical practice described as a placement of a medical needle into an epidural space, an insertion of a catheter through the needle and an injection of anesthetic in order to numb the nerves. A skilled anesthesiologist penetrates the needle through tissue layers such as subcutaneous fat, interspinous ligament, intraspinous ligament, ligamentum flavum and reaches the target space. Currently, methods of positioning of the needle tip into the epidural space are based on subjective perception, which are not safe and accurate. In order to improve the effectiveness of the epidural space identification, this work proposes a sensorized optical fiber mounted externally on the needle. This medical device provides continuous and real-time measurements with the help of an optical backscattered reflectometry. When the needle is exposed to strain variations during its advancement, the intensity of backscattered light changes. By correlating the spectrum with the reference one, strain patterns can be produced. Obtained data can detect the needle passage from one tissue to the other in a custom made phantom, which mimics a human spinal anatomy. Specifically, needle passage from the stiff ligamentum flavum to the soft epidural space results in a significant strain drop and a consequent increase, which is considered as a crucial indicator of epidural space identification. The proposed device is advantageous over existing optical guidance: it does not obstruct the flow of a liquid in the inner side of the needle; the needle from the tip to the tail performs as a sensor.

We present a multimodal catheter for characterizing airway collapse in obstructive sleep apnea (OSA) during in-vivo sleep studies. Traditionally, diagnosis focusses on identifying the presence of apnea rather than the underlying cause of obstruction, and current methods of detecting airway collapse are not able to identify a specific patient’s contributing factors. It is considered that a simple method to establish the primary site and mechanism for upper airway collapse would improve the ability of clinicians to distinguish which patients would benefit from one of the variety of treatments currently available. By introducing a newly developed manometry catheter into in-vivo studies of known OSA sufferers we can provide the means to determine the location of the site(s) of collapse, the degree of occlusion that occurs, the severity of reduced air flow, the associated anatomical features, and mechanism of collapse. The device consists of 13 discrete pressure and temperature sensing elements and a micro-video camera that collectively enable simultaneous recording of pressure, temperature, and visualization of the point of collapse. The sensors use fiber Bragg gratings (FBGs) spaced on a 10mm pitch which is sufficient to provide an accurate interpolated image of both pressure and temperature along the upper airway (above the epiglottis), whilst the use of paired FBGs effectively removes the temperature artefact. We present results from recent in-vivo studies that demonstrate the viability of the device to identify and characterize occlusive events in the upper airway and the potential to better guide subsequent therapeutic interventions.

The most challenging aspect of deep anterior lamellar keratoplasty (DALK), is what’s known as “Big Bubble” technique which injects air/fluid to fully separate the Descemet’s Membrane and stroma with a hydro-dissection needle. Big bubble technique requires micron accuracy to guide the needle to approximately 90% depth of cornea. Here, we developed and tested common-path swept source optical coherence tomography (CP-SSOCT) distal-sensor integrated hydro-dissection needles, which can accurately detect the needle position relative to corneal tissues with micron accuracy. The OCT distal-sensor was put inside a 30-gauge needle, which was also used for hydro dissection. A high-index elliptical epoxy lens was attached to the end of the single mode fiber to increase the signal to noise ratio inside the cornea. To control the position and insertion angle of the sensor, we customized the eye mount with an angular slide and a precise linear motor with Luer-slip. The needle was fixed outside, 100um from epithelium layer, to obtain the A-scan image to identify both epithelium and endothelium membranes at every 10° from 0° to 70° insertion angles. The needle was then inserted into bovine cornea and recorded A-scan images at each step. Freehand insertion test was performed with and without sensor guided needles. The results showed that the position of the epithelium and endothelium membranes were still identified from A-scan even at 70°. Sensor guided freehand test can reach 95% of cornea thickness on average without any perforation. These results are consistent with our hypothesis that CP-SSOCT fiber sensor can guide a needle insertion inside a cornea for Big Bubble technique.

We demonstrate multimode fiber probe that accomodates dual modality properties for high power ultrashort pulse delivery. A commercially available multimode graded-index (GRIN) fiber is used for two-photon imaging and/or femtosecond laser ablation of Cochlea hair cells. Lensless focusing and digital scanning of ultrashort pulses through the optical fiber is realized using the transmission matrix technique. We investigate the performance and the limitations of the GRIN probe in terms of focusing efficiency and peak power delivery. Selective laser ablation guided by the twophoton image obtained through the GRIN fiber is realized by proximally-only control of the femtosecond laser beam.

Secondary ion mass spectrometry (SIMS) has the unique ability to obtain the spatial and depth distribution of a wide range of atoms and molecules including polymers, pharmaceuticals, lipids, proteins, and semiconductors without the use of labels such as fluorescent tags. In SIMS ion beams are used to desorb molecules from surfaces; the mass of the molecules is then determined using mass spectrometry (MS). In this presentation we illustrate the use of mass spectrometry for the analysis and development of a variety of sensors and devices, including fluorescent electrochemical sensors and pacemakers. While there have been many recent improvements in the performance of SIMS for molecular analysis but their application in imaging MS remains limited by the small number of analyte-specific ions that are obtained per sub-micron pixel and the large amount of data produced. To address these issues, we shall illustrate our current work in both SIMS experimental and data analysis techniques. We shall describe the use of room temperature ionic liquids (ILs) as matrices for the enhancement of SIMS signals. ILs have many uses including in microextraction, and as solvents, lubricants and as matrices in matrix assisted laser desorption/ionization mass spectrometry (MALDI MS). Initial studies focused on the use of two different ionic liquids (ILs), derived from the MALDI matrix α-cyano-4-hydroxycinnamic acid (CHCA). The data clearly show that ILs are extremely effective matrices in SIMS for both biological and polymeric samples. Increases in molecular ion intensities of more than 2 orders of magnitude have been observed, as well as ~3 orders magnitude improvements in detection limits. Second, we shall describe our new method for the analysis of imaging MS data which is based on maximum a posteriori (MAP) reconstruction against physically motivated models. This allows us to quantitatively measure concentrations of species, and extract their mass spectra and sample topography. Further, for the first time this model can be used to investigate matrix effects present.

Jim Harrington was a respected and loved member of our community. He attended all meetings since its inauguration. His passing away this year is a great loss. The conference committee members and friend will each present their personal interactions with jim.

Photonic Crystal Fibers represent a good platform for the development of sensitive and cheap sensors for the detection of protein and DNA sequence. The holes running along the fiber allows the infiltration of biological substances and for biological layers to attach on the air-dielectric interfaces. In addition, the presence of a hollow core can further increase the infiltration feasibility and the sensor sensitivity. Recently, the possibility in using hollow core tube lattice fibers (HC-TLFs) for label-free DNA detection have been numerically investigated. The sensing is based on the waveguiding mechanism, that is inhibited-coupling which makes the HC-TLF transmission properties particularly sensitive to the thickness of the glass struts composing the microstructured cladding of those fibers. The molecular interactions between the surface of the glass and the target to be detected results in a generation of a biological layer which modifies the strut thickness and thus the fiber transmission properties. The aim of the present work is to experimentally demonstrate that HC-TLF can be successfully used as bio sensor for proteins. After a functionalization of the silica surface through a solution of aptes, a layer of biotin was deposited on inner surfaces of the fiber. The fiber was than infiltrated with a solution containing streptavidin and an additional bio-layer is deposited on the surfaces. The experimental results demonstrated a red shift of the entire fiber transmission spectrum of about 7 nm corresponding to an additional bio-layer with thickness of 6.45 nm which is fully compatible with the size of streptavidin molecules of about 6nm.

An ATR measurement system composed of hollow optical fibers, a trapezoid multi-reflection prism, and a couple of fixed-wavelength QCLs emitting different wavelengths is proposed for non-invasive measurement of blood glucose. To choose a wavelength combination that is appropriate for measurement of glucose absorption, firstly absorption spectra of human lip mucosa measured by using an FT-IR-based ATR system are investigated. As a result, two wavelengths, 1152 cm^-1 that coincides with an absorption peak of glucose, and 1186 cm-1 where the glucose absorption becomes minimum are chosen. From numerical simulation using spectral absorptions measured by the FT-IR system, it is found that the differential absorption between the above wavelengths shows a good correlation to blood glucose levels. Finally in-vivo measurement using the ATR system equipped with two single-wavelength QCLs is performed and it is found that the measured optical absorption follows the blood glucose well.

Sterilization of medical equipment using e-beam or gamma radiation produces high sterility assurance but may lead to alterations in materials being treated. Thus, color centers developed in optical fibers result in added attenuation. In this work a series of specialty single-mode (SM) and multimode (MM) optical fibers (13 in total) were exposed to gamma and e-beam sterilization doses of 32 kGy, and the radiation-induced attenuation was investigated. The optical fibers selected for the study had different core chemical compositions, including pure silica and also SiO₂ doped with Ge, F, P and Al. The fibers also differed in the clad diameters (80 and 125 μm), numerical aperture (0.1 – 0.21), coating types (carbon, acrylate, polyimide) and the cutoff wavelength (SM fibers only, 930 – 1470 nm). Effects of all these features on the radiation-induced attenuation were analyzed primarily in the framework of medical applications. The radiation-induced optical losses can be moderated by subsequent thermal treatment of the fibers, and such option was also investigated. Our results showed that while the radiation-induced losses may be high (10² – 10⁴ dB/km), sterilization using e-beam and gamma radiation can be acceptable for many medical applications that deploy 3 m or less fiber lengths. After gamma or e-beam sterilization, 3 meters length of SM fibers with pure SiO₂ and Ge doped core transmit >98% of optical power at 1550 and 1310 nm. In contrast, similar length of SM fibers with P and Al doped cores exhibit very low transmission and cannot be used after ionizing sterilization. Among the MM fiber, F-doped core fibers display much higher transmission than Ge-core fibers, especially at 850 nm. The clad diameter, coating type and bend insensitive features in the refractive index profile did not show much effect on the radiation-induced loss. While gamma and e-beam radiation caused similar changes in the attenuation spectra, gamma radiation caused ~25% higher loss increase than e-beam at the same 32 kGy dose. Since our data showed that postradiation annealing at 100°C for 24 hours results in only ~30% recovery of the radiation induced loss, it may not be practical to implement such annealing scheme for medical applications.

The pneumatic type heart assist pump has a pneumatic chamber and a blood chamber separated by a flaccid membrane. By compressing and sucking the gas into the pneumatic chamber, the membrane shape changes as a result the stroke volume will also change. Our task is to determine the real time stroke volume. The idea presented in the work uses shape reconstruction of the membrane created on the basis of image analysis to calculate the stroke volume. This is made possible by equipping the pump with a wide-angle camera and using the DFD method to visually measure the distance between the camera and the characteristic points selected on the surface of the membrane. A new technique was developed based on this for determining the stroke volume of the pneumatic heart assist pump. The work presents a vision sensor for precise control of the pneumatic heart assist pump, as well as results obtained during experimental research.

In view of the growing importance of nanotechnologies, the detection of nanoparticles type in several contexts has been considered a relevant topic. Several organisms, including the National Institutes of Health, have been highlighting the urge of developing nanoparticles exposure risk assessment assays, since very little is known about their physiological responses. Although the identification/characterization of synthetically produced nanoparticles is considered a priority, there are many examples of “naturally” generated nanostructures that provide useful information about food components or human physiology. In fact, several nanoscale extracellular vesicles are present in physiological fluids with high potential as cancer biomarkers. However, scientists have struggled to find a simple and rapid method to accurately detect/identify nanoparticles, since their majority have diameters between 100-150 nm - far below the diffraction limit. Currently, there is a lack of instruments for nanoparticles detection and the few instrumentation that is commonly used is costly, bulky, complex and time consuming. Thus, considering our recent studies on particles identification through back-scattering, we examined if the time/frequency-domain features of the back-scattered signal provided from a 100 nm polystyrene nanoparticles suspension are able to detect their presence only by dipping a polymeric lensed optical fiber in the solution. This novel technique allowed the detection of synthetic nanoparticles in distilled water versus “blank solutions” (only distilled water) through Multivariate Statistics and Artificial Intelligence (AI)-based techniques. While the state-of-the-art methods do not offer affordable and simple approaches for nanoparticles detection, our technique can contribute for the development of a device with innovative characteristics.

Using infrared spectroscopy for blood analysis has a high potential. In order to bring infrared spectroscopy to clinics, a cost-effective sampling approach, high sample throughput, small sample sizes (< 15μl) and a low detection limit are required. A novel ATR crystal with subwavelength structures on the sampling side was developed and fabricated. The structures and the analyte form an effective medium layer, which supports destructive interference. The absorption signal can be enhanced by at least one order of magnitude. The microstructures also act as a micro sieve that replaces blood centrifugation. The enhancement can be optimized for wavelength regions of interest by changing the dimensions of the microstructures. First steps towards the solution of this high dimensional inverse design problem were made with different neural network architectures.

Nitrate is a frequent water pollutant that results from human activities such as fertilizer over-application and agricultural runoff and improper disposal of human and animals waste. Excess levels of nitrate in watersheds can trigger harmful algal blooms (HABs) and biodiversity loss with consequences that affect the economy and pose a threat to human health. Municipal drinking water and wastewater treatment plants are therefore required to control nitrogen levels to ensure the safety of drinking water and the proper discharge of effluent. Nitrate exhibits distinct absorption bands in the infrared spectral range. While infrared radiation is strongly attenuated in water, implementation of fiber optic evanescent wave spectroscopy (FEWS) enables monitoring of water contaminants in real-time with high sensitivity. This work outlines the development of a non-dispersive infrared (NDIR) detector for the real-time monitoring of nitrate, nitrite and ammonia concentrations targeting implementation at municipal wastewater treatment plants (WWTPs) and onsite wastewater treatment systems (OWTS).

Infrared (IR) optical fibers may be defined as fiber optics transmitting radiation with wavelengths greater than approximately 2 mm. The first IR fibers for Mid IR were fabricated in the mid-1960s from Chalcogenide IR-glasses (CIR-fibers) – such as As-S-glasses with attenuation >10 dB/m.1 During the mid-1970’s, the interest in developing an efficient and reliable IR fiber for short-haul applications increased partly in response to the need for a fiber to link broadband, long wavelength radiation to remote photodetectors in military sensor applications. In addition, there was an ever increasing need for a flexible fiber delivery system for transmitting CO2 laser radiation in surgical applications. SPIE Technical Symposium on Infrared Fibers in 1981 was the 1st one dedicated to this topic - describing all three flexible Mid IR-solutions: glass and crystalline fibers, plus hollow waveguides. Since that time there was good progress reached in each category, and this presentation will review the key milestones - complimented by the latest results achieved in IR-fiber technology and in the promising areas of advanced applications. Prof. James A. Harrington, former SPIE president has passed away in June 2018 after his life devoted to the development of crystalline IR-fibers and hollow waveguides – and we devote this conference and this review talk to his memory. Jim Harrington has died too early because of cancer – while IR-fiber systems can help to fight with this killer disease. Present review will highlight the latest fiber solutions used to detect tumor margins and to enable intraoperative optical control of several therapy methods - realizing the "theranostic" fusion.

Extremely flexible hollow optical fibers with 75-μm-bore size were developed for infrared laser light delivery. The hollow fiber was inner coated with silver and dielectric layers to enhance the reflection rate at an objective wavelength band. The silver layer was inner-coated by using the conventional silver mirror-plating technique. Concerning the fabrication parameters used up to now for 320-μm-bore size fibers, the target flowing rate for plating solutions was 10 ml/min. Parallel arranged bundles of silica capillaries were used to increase the cross-sectional area of the air core. To achieve the flow-rate target, four bundles of 300 pieces of silica capillaries with an inner/outer diameter of 75/150-μm and a length of 20 cm were bundled. To increase the flow rate, four bundles with an inner diameter of 75-μm and a length of 20 cm, together with three silica capillaries with an inner diameter of 530-μm and a length of 50 cm were connected in parallel. The spectrum loss measured by an optical spectrum analyzer for the 75-μm-bore size, 10-cm-length silver hollow optical fiber was around 5 dB at the wavelength of 1-μm. Thin dielectric layer was formed by using liquid-phase coating method for low-loss transmission of Er:YAG laser light.

We demonstrate the fabrication of multi-core (imaging) microstructured optical fiber via soft-glass extrusion through a 3D printed die. The combination of 3D metal printing and extrusion allows for unprecedented control of the optical fiber geometry. We have exploited this to demonstrate a 100 pixel rectangular array imaging microstructured fiber. Due to the high refractive index of the glass used (n = 1.62), such a fiber can theoretically have a pixel pitch of less than 2 μm. This opens opportunities for ultra-small, high-resolution imaging fibers fabricated from diverse glass types.

Stretchable optical and electronic fibers constitute increasingly important building blocks for a myriad of applications, particularly in robotics, soft prosthesis, surgical tools and implants, and smart medical textiles. The integration of multimaterial architectures and complex functionalities within soft fibers has however for a long time remained difficult to achieve, limiting the performance and functionalities of medical fibers and textiles. In this contribution, we will show how the thermal drawing process used to fabricate optical fibers, and traditionally associated with rigid glasses or thermoplastic, can be applied to a certain class of thermoplastic elastomers. We will demonstrate that optical polymers, liquid metals, and conductive polymer composites could be co-drawn with prescribed architectures within a thermoplastic elastomer cladding. This allowed us to successfully fabricate super-elastic fibers with complex optical as well as electronic functionalities relevant for a myriad of applications in health-care. We will show in particular how such fibers can be used as precise and robust pressure, strain or more generally deformation sensors that can be seamlessly integrated within surgical tools, prosthesis, fabrics or robots. We will also discuss their potential as advanced optical probes, regenerative scaffolds or stimulating implants. This work opens novel opportunities for sensing and monitoring, scaffolds and implants, medical robotics and personalized care.

In this study, cylindrical diffusing optical fiber probe (CDOFP) used for tumor treatment using PDT method is developed and analyzed. Diffusing beam profile of 5mm to 40mm tip length probe is produced and analyzed using laser scribing equipment developed in a previous research. Ball tip at the tip of CDOFP was developed for easier infiltration of tissues and the beam profile of such tip is reviewed. Additionally, CDOFP for PDT tumor treatment was used for laser coagulation test on animal tissue. CDOFP with diffusing tip length 5mm and 15mm was infiltrated inside a cow's liver tissue to process laser coagulation test. Coagulation and thermal damage was measured with twice the maximum intensity of laser, where maximum intensity in-vivo test is 1W 200J.

This paper presents an initial investigation into the depth dependence of an inorganic optical fibre sensor (OFS) based on physical measurements and Monte Carlo (MC) simulations, using a 6 MV flattening filter free (FFF) beam. The OFS was fabricated using an inorganic scintillating material (Gd₂O₂S:Tb), which was embedded in a cavity of diameter 700 μm, in a 1mm plastic optical fibre. Percentage depth dose (PDD) profiles were measured in a solid water phantom for three field sizes: 10×10 cm² , 4×4 cm² and 2×2 cm² . The OFS results were then compared to an ion chamber and the W1 plastic scintillator. A MC model of an Elekta Versa HD linear accelerator (linac) was developed using the MC software packages BEAMnrc and DOSXYZnrc and then used to simulate the Gd₂O₂S:Tb and polystyrene scintillators. The OFS measurements over-estimated the dose when compared to the ion chamber and the W1 measurements, across the investigated field sizes, by a maximum of 30%, 20% and 15% for 10×10 cm² , 4×4 cm² and 2×2 cm² , respectively. The MC simulations of the Gd₂O₂S:Tb and polystyrene scintillators were in good agreement with the W1 and ion chamber measurements, however, the OFS measurements were found to differ across all field sizes. Our results therefore indicate the need for further investigation into the overall contribution of the stem effect to the discrepancy between the OFS physical measurements and the ion chamber and the W1 measurements.

Radioluminescent fiber optic dosimeters have drawn great attention due to their unique practical advantageous properties including the ability to perform in vivo, real-time, and intracavity measurements with high spatial resolution due to their small physical size and mechanical flexibility. These features make them ideal candidates for many potential applications in radiation therapy dosimetry, such as in brachytherapy, intensity-modulated radiation therapy, superficial therapy, stereotactic radiosurgery, proton therapy, and small-field dosimetry. However, in therapeutic radiation fields, the total optical signal carried by the fiber has undesirable components in addition to the useful radioluminescent signal. The main problem with fiber optic dosimeters in photon and electron therapies is these undesirable signals that are primarily the Čerenkov radiation generated in the irradiated portion of the guide fiber. Another significant issue related to scintillation fiber optic dosimetry that occurs in proton therapy and other beams with high linear energy transfer (LET) is the non-proportionality between the scintillation signal and the proton dose due to the ionization quenching. In this work, recent progress toward minimizing the impact of Čerenkov radiation and ionization quenching through using spectroscopic methods, specialty fiber optics, and undoped fibers is briefly reviewed.

Stochastic Monte Carlo method (MC) is often used to model light propagation in biological tissues. Since many photon packets need to be process to attain good quality of the simulated data, the experimental geometry in MC simulations is usually substantially simplified to shorten the computation times. However, such simplifications have been shown to introduce large simulation errors when using optical fiber probes. In our previous study, we have shown that the frequently used laterally uniform probe-sample interface simplification can introduce significant errors into the MC simulations of spatially resolved reflectance (SRR) potentially exceeding 200 %. Unfortunately, using full details of the probe tip in the MC simulations breaks down the radial symmetry of the detection scheme. Consequently, the simulation time required to obtain a good quality SRR increases by about two orders of magnitude. In this study, we introduce a framework for efficient and accurate MC simulations of SRR acquired by optical fiber probes that accounts for all the details of the probe tip including reflectance from the stainless steel and the refractive indices of the epoxy fill and optical fibers. For this purpose, we introduce an efficient regression model that maps SRR obtained through fast MC simulations based on simplified geometry to the SRR simulated by full details of the probe-sample interface. We show that a small number of SRR samples is sufficient to determine the parameters of the regression model. Finally, we use the regression model to simulate SRR for a stainless steel optical probe with six linearly placed fibers and build inverse models for estimation of absorption and reduced scattering coefficients and subdiffusive scattering phase function related quantifiers.

Optical Backscatter Reflectometer (OBR), based on Optical Frequency Domain Reflectometry principles can transform a simple and cheap single mode fiber in an efficient spatially distributed (over the fiber length) sensor of temperature and strain variation. Nevertheless, the use of OBR is limited to function with a single sensing fiber. Connecting multiple fibers in parallel can be problematic. The scattering level of each fiber is of the same magnitude so that the backscattering cannot be discriminated. Unfortunately, particular medical applications, such as the guided insertion of needle or medical catheters, can benefit of multiple fiber sensors mounted in parallel. The adopted solution of switching between different sensors in different time frames if feasible, but it significantly reduces the interrogation frequency. In this work a new solution for overcoming this issue, by the use of a high scattering nano-particles doped fiber (NPDF), is proposed. This fiber presents a random distributed pattern of magnesium oxide nanoparticles, whose size varies between 20 to 100 nm, in the core. Its backscattering is 50 dB larger than a standard single mode fiber. The use a NPDF segment spliced to a standard single mode pigtail, with different lengths, such that the NPDF position corresponds to a pigtail on the other fibers, permits to connect them in parallel. Thus, the OBR can spatially resolve the NPDF high backscattering, since the single mode pigtail scattering is irrelevant. Experiments have shown positive results in the terms of temperature and strain discrimination.

Spectroscopic analysis of different body fluids has been realized by using tapered flat silver halide fiber elements as infrared biosensors. Here, a specially functionalized sensor is presented, which had been prepared by an Nhydroxysuccinimide (NHS) ester derivative containing a reactive thiol group. NHS esters are often used as coupling agents to covalently bind amine-containing biomolecules (e.g., enzymes, antibodies or peptides) for the preparation of bioanalytical sensors of high selectivity. Recently, an immuno-infrared-sensor for Alzheimer disease (AD) screening has been presented based on infrared ATR-measurements with antibody-immobilized Ge-element surfaces for the extraction and analysis of Amyloid-beta (Aβ)-monomers, oligomers, and fibrils from blood plasma and cerebrospinal fluid (CSF). Thereby the biomarker amide I maximum frequency was used for AD classification. Here, for functionalizing the silver halide surfaces different procedures have been investigated, which consider the exchange reaction of the halogen atoms by the thiol-group as one option. Other preparation methods use the chemical reduction of silver ions, either from aqueous salt solutions or of the fiber material itself. A further method uses a first printing of silver nanoparticles on top of the flattened fiber sections. The combination of specific protein immobilization via functionalized silver halide fibers with recently introduced quantum cascade laser spectrometers is very promising for device miniaturization suited for implementation into hospital laboratories or general practitioners’ offices.

A localized surface plasmon resonance (LSPR) temperature sensor based on photonic crystal fiber (PCF) filled with liquid and silver nanowires is demonstrated both theoretically and experimentally. Simulation results show that a blueshift is appeared along with temperature increasing. The resonance wavelength and resonance intensity can be tuned effectively by adjusting the volume ratios of the liquid constituents. To investigate the sensor’s performance, a large temperature range from 25°C to 60°C is detected in experiment and the sensitivity of -2.08 nm/°C with figure of merit (FOM) 0.1572 is obtained. The all-fiber device with strong mechanical stability is easy to realize remote sensing by changing the downlead fiber length, also promising for developing a high sensitive, real-time and distribute fiber sensor in temperature sensing applications.

Infrared thermography (IRT) – a non-contact, non-invasive technique – has been used for mass screenings to identify febrile individuals at transportation nodes (e.g., airports) during infectious disease pandemics such as SARS (Severe Acute Respiratory Syndrome), H1N1 virus, and Ebola outbreaks. Despite the potential of IRTs, the field lacks a well-established consensus methodology to ensure temperature measurement accuracy and reliability. This study aims to investigate the use of IRTs in a controlled setting to determine the effectiveness of IRT and the most reliable facial region for estimation of core temperature. We conducted a large clinical study, acquiring facial thermographs of 1,109 febrile and non-febrile subjects using Screening Thermographs (STs). Regression analyses between the reference oral temperature and different areas of the face, specifically the forehead and canthi, were carried out. The coefficients of determination of each regression were compared to determine how well facial and core body temperatures were correlated. Receiver operating characteristic (ROC) curves were constructed to compare the effectiveness of using different facial areas to identify febrile patients. Results show that the maximum temperature of the overall face has the best linear trend, followed by the maximum temperature at the inner canthus region. Both of these values show better correlations than forehead temperatures, which are commonly used as a target by non-contact infrared thermometers. For any chosen facial area, the maximum temperature collected always showed a stronger correlation than a specific point in that area. Results indicate that IRT performance is substantially approved when applying optimal measurement methodology.

Melanoma is responsible for most of the fatalities from skin cancer diseases. Yet, there is no reliable method for a noninvasive early detection of skin cancers. We developed a Fiber-optic Evanescent wave Spectroscopy (FEWS) method based on a Fourier Transform Mid-IR (FTIR) spectrometer and on U shaped silver halide (AgClBr) fibers that are highly transparent in the mid-IR. We measured suspicious lesions on patients, before their excision. The central part of the bent fiber touched the lesion and the mid-IR absorption of this area was measured in situ and in real time. As a background, the same measurement was performed on healthy nearby skin. All discomfort to the patient was avoided. The lesions were then examined by conventional means. Histopathology revealed 5 melanoma tumors out of 90 patients and clear and repeating spectral differences between background and lesion are seen in all patients. We continue to accumulate spectral data of melanoma and of other pathologies, for better statistics and for characterization of other types of skin cancer. It is hoped that this non-invasive method for an early detection and diagnosis of skin cancer will replace biopsy and revolutionize this field.

Optical detection techniques based on surface enhanced Raman spectroscopy (SERS) and capable of providing relevant information on molecular and protein composition of biological samples, are gaining rising attention in clinical research as alternatives to traditional detection assays. Meanwhile, due to the technological advances in compact instrumentation as well as in nanofabrication processes, SERS probes based on portable guided-wave systems, have been implemented thus providing for easier accessibility into complex environments and enabling for real-time in situ detection of low concentrated target analytes. In the present study, low-cost fabrication processes were successfully combined with surface functionalization strategies for the fabrication of disposable SERS-active substrates, engineered to tightly fit the distal end of portable Raman instruments. Being based on a polymer casting fabrication process, the overall design of the substrates can be easily adapted to the varied geometry of the probes to be fit, thus guaranteeing high design versatility. SERS-functionality was achieved by immobilization of gold nanoparticles whose size and shape directly affect the plasmonic properties of the substrates. Moreover, SERS substrates can be further modified by covalently binding molecules acting as baits to selectively fish target biomarkers within heterogeneous samples thereby increasing the specificity of SERS signals. Finally, these sensors represent a powerful tool potentially implementable for the early diagnosis of widespread pathologies by real-time SERS analysis of liquid biopsy.

In-vivo examinations of cervical tissue were performed using Evoked Tissue Fluorescence (ETF) as part of a clinical trial. These examinations were performed in conjunction with conventional colposcopy, along with of biopsies of suspect cancerous or pre-cancerous tissue. The ETF data consisted of 22 images of the cervix taken at combinations of 3 excitation wavelengths and 9 emission wavelengths. The ultimate goal was to use these images to accurately classify tissue between normal states (normal squamous and normal columnar) and pre-cancerous and cancerous states (squamous metaplasia, and high and low Squamous Intraepithelial Lesion, HSIL and LSIL). Several chemometric methods were applied to the data for the purpose of preprocessing (e.g. image alignment), eliminating patient to patient variability (e.g. GLS and specialized centering), classification of tissues (hierarchical PLS-DA) and elucidating the underlying signatures of the tissues and background components (PARAFAC).

Alzheimer’s disease (AD) is an irreversible progressive disease that damages the brain cell and affects the cognitive abilities. Hence an early detection of AD biomarkers is vital for the drug treatment. Considering this, we developed a sensitive and reliable sensing tool based on fiber-enhanced Raman spectroscopic technique for the detection of AD biomarkers. The fiber-enhanced Raman measurements were performed using a hollow core photonic crystal fiber, and a comparison of Raman spectra of samples in a conventional cuvette and with the fiber was carried out. The results showed a high enhancement of Raman signal of samples measured with a fiber compared to the measurements carried out in the cuvette.

We proposed a multimode-interference-based spatio-spectral encoder for scanner-free single-fiber fluorescence imaging. Since the fluorescence spectrum measured via the SSE is modulated by multimode interference, it shows a specific shape corresponding to the position. By encoding the collected light from every imaged pixel, the two-dimensional fluorescence image is reconstructed from a single measured spectrum. SSE is fabricated by splicing a short multimode fiber to the tip of a single mode fiber. Imaging of two-dimensional objects using fabricated SSE is demonstrated.

Optical frequency combs (OFCs) have attracted attention as optical frequency rulers due to their tooth-like discrete spectra together with their inherent mode-locking nature and phase-locking control to a frequency standard. Based on this concept, their applications until now have been demonstrated in the fields of optical frequency metrology. However, if the utility of OFCs can be further expanded beyond their application by exploiting new aspects of OFCs, this will lead to new developments in optical metrology and instrumentation. Previously, we reported a fiber sensing application of OFCs based on a coherent link between the optical and radio frequencies, enabling high-precision refractive index (RI) measurement based on frequency measurement in radio-frequency (RF) region. Our technique encoded an RI change of a liquid sample into a repetition frequency of OFC by a combination of an intracavity multi-mode-interference fiber sensor and wavelength dispersion of a cavity fiber. Then, the change in refractive index was read out with an RI resolution of 4.88 × 10^-6 RIU and an RI accuracy of 5.35 × 10^-5 RIU by measuring the repetition frequency in RF region based on a frequency standard. However, the temperature instability of a sample limits the performance because a refractive index is a function of temperature. In this paper, we demonstrate simultaneous measurement of concentration and temperature in a sample by measuring RI-dependent repetition frequency shift and optical spectrum shift.

Photodynamic therapy is a promising method to selectively treat cancer with light. Therefore, the tumour cells have to be illuminated homogeneously by distributing optical fibers with diffuser tips within the tumour tissue. The challenge is to measure and thereby, tailor the irradiation of the diffusers. In this paper, a novel non-imaging, camera-based method to measure the radiation profile is introduced and compared to an established imaging-based method. The radiation profile of a commercial polymer diffuser with radial homogeneous emittance and the profile of an ultrafast-laser surface structured fiber with radially asymmetric emission was evaluated. For the novel method, the diffuser was positioned in close contact to the image sensor. After coupling a LED to the diffuser, images were recorded for various radial positions. The irradiation profiles of the diffusers were also determined using an imaging camera system. The radiation profiles measured with the novel approach stand in good agreement with the existing imaging method using radial homogeneously emitting diffusers. However, the comparison revealed that the novel approach is advantageous, if the radiation profile is radially asymmetric and if the near-field is of special interest. In this case, several details, such as double peaks, were resolved, which were invisible using other methods. The novel approach is of special interest for the development of simulation models to gain further knowledge about the laser-tissue interaction in the near-field of the fiber. Thereby, irradiation profiles of diffusers could be predicted and tailored towards an application specific irradiation.

Inserting pH probes into precise location of deep tissue yields important possibilities for biomedical science purposes and medical diagnosis. A micro/nanoscale pH sensor can be used as a diagnostic tool, a drug delivery module for pointof-care therapy, an imaging instrument or a combination of these three modalities depending on the sensor’s design and range of sensitivity. We established the fundamental investigations for building up an optical pH sensor using a type of food-grade Lyotropic Liquid Crystal (LLC) nanoparticles. The pH sensor operates based on the liquid crystal reconfiguration upon variation of hydronium concentration in the surrounding solution. The mesophase matrices can be loaded with fluorescent agents as a drug and release it with different rates depending on the pH of the volume. The release rate can be used as a correlation factor in combination with the guest fluorescence optical attributes, such as color, and help us designing an accurate ratiometric pH sensor for monitoring esophageal acid reflux. Here, the release behavior of the mesophase loaded with Rhodamine 6G (a fluorescent model dye) was examined in standard buffers. The rapid response of a few milliseconds and pH sensitivity of the host mesophase between normal to acidic conditions in esophagus offers possibility for real time monitoring of pH values in such biological interface. The effect of pH, temperature, and dye concentration on the release rate were investigated in this research.

Silica fiber and polymer optical fiber (POF) are electromagnetically intensive and can provide a huge wide bandwidth for sensing, monitoring, and endoscopic applications. A great advantage can be obtained due to a small size and array potential to provide discrete imaging speed improvement. While silica is more mature, POF has an important advantage over silica fiber that is silica fiber is a brittle material that would not be recommended to be used with the human body. The superior mechanical properties of POF not only reduce safety concern but also present the potential for greater sensitivity. Polymethylmetacrylate (PMMA), Polycarbonate (PC), Polystyrene (PS), and perfluorinated polymer fiber commonly referred to as Cyclic Transparent Optical Fiber (CYTOP) are leading different types of polymer fibers. In this paper the attenuation and Sellmeier coefficients for the different types of polymer fibers were analyzed and extracted. The extracted values were than utilized to model and simulate the attenuation and dispersion behavior of the polymer fibers. Moreover, OptiFiber simulator was used to simulate index profile of those different POF parameters. These results were then fed to the Optisystem simulation tool to model the application of POF in short distance data transmission system. The application of POF in medical sensing field was demonstrated by proposing a fiber-optic respiration sensor for respiratory monitoring.