Distributed fiber optic shape sensing with simultaneous interrogation of multiple fibers based on Rayleigh-signature domain multiplexing.

We propose a method for shape sensing that employs Rayleigh-signature domain multiplexing to simultaneously probe the fibers or cores of a shape sensing setup with a single optical frequency-domain reflectometry scan. The technique enables incrementing the measurement speed by a factor equal to the number of multiplexed fibers at the expense of an increased noise floor in accordance with the Cramér-Rao lower bound. Nonetheless, we verify that the shape reconstruction performance of the proposed method is in very good agreement with that of conventional sequential core interrogation.

Minimally-Invasive Secondary Cytoreduction in Recurrent Ovarian Cancer.

The role of secondary cytoreductive surgery (SCS) in the treatment of recurrent ovarian cancer (ROC) has been widely increased in recent years, especially in trying to improve the quality of life of these patients by utilising a minimally-invasive (MI) approach. However, surgery in previously-treated patients may be challenging, and patient selection and surgical planning are crucial. Unfortunately, at the moment, validated criteria to select patients for MI-SCS are not reported, and no predictors of its feasibility are currently available, probably due to the vast heterogeneity of recurrence patterns. The aim of this narrative review is to describe the role of secondary cytoreductive surgery and, in particular, minimally-invasive procedures, in ROC, analyzing patient selection, outcomes, criticisms, and future perspectives.

Back to the future: The impact of oestrogen receptor profile in the era of molecular endometrial cancer classification.

PURPOSE: The aim of this study is to evaluate the impact of the oestrogen receptor (ER) profile on oncologic outcomes in the new endometrial cancer (EC) risk classification. METHODS: Immunohistochemistry (IHC) analyses were performed in a retrospectively reviewed large series of ECs to assess the presence/absence of oestrogen receptors (ER0\1+ or ER2+\3+) and other molecular factors (i.e. p53 mutation, p53mut; and mismatch repair mutational status, MMRd (mismatch repair deficient) versus MMRp (mismatch repair proficient)), histopathologic and clinical outcomes. ER status was correlated with molecular, histologic, clinical and prognostic data. RESULTS: 891 EC patients were included in the study (211 ER0\1+ and 680 ER2+\3+). The ER0\1+ phenotype was associated with an unfavourable clinicopathological profile (i.e. grading, histotype, lymphovascular space invasion (LVSI), stages, etc.). Simple regression showed that risk class, p53mut, and ER0/1+ impacted on both disease-free survival (DFS) and overall survival (OS) (p < 0.05). In the ER0/1+ population, p53mut no longer influenced DFS and OS (p > 0.05). In multiple regression, age, high and advanced/metastatic risk classes influenced survival outcomes (p < 0.05), but lost significance in the ER0/1+ population (p > 0.05). ER-positivity retained a remarkable prognostic impact even after stratification of the population according to the European Society of Gynaecological Oncology, the European Society for Radiotherapy and Oncology, and the European Society of Pathology (ESGO/ESTRO/ESP) 2021 risk classes and molecular classification. ER0/1+ intermediate, high-intermediate, high and advanced risk versus ER2+/3+ intermediate, high-intermediate, high and advanced risk classes showed statistically different OS and DFS (p< 0.001). ER0/1+ status was associated with a worse prognosis when associated with MMRp, MMRd and p53mut compared to the same molecular classes associated with ER2+/3 (p < 0.001). CONCLUSIONS: We demonstrated that ER status has a significant impact on oncologic outcomes, regardless of risk class and p53/MMR status. Based on our results, we recommend the inclusion of ER assessment in featured EC risk classification system.

Influence of birefringence- and core ellipticity-induced mode coupling on the gain statistics of forward-pumped Raman amplified few-mode fiber links.

The equations describing light propagation in a few-mode fiber for space-division multiplexing are derived under the presence of linear mode coupling and both Kerr- and Raman-induced nonlinearity. By considering physical models of stress birefringence and core ellipticity, the effect of such fiber imperfections on the gain of a forward-pumped Raman-amplified link is assessed through numerical simulations. The average gain and the variation of signal power at the output of the amplified fiber span is numerically evaluated for different levels of coupling strength in fibers supporting 2 and 4 groups of LP modes, identifying three main propagation regimes and assessing the effect of coupling between different groups of degenerate modes.

Rayleigh-Based Distributed Optical Fiber Sensing.

Distributed optical fiber sensing is a unique technology that offers unprecedented advantages and performance, especially in those experimental fields where requirements such as high spatial resolution, the large spatial extension of the monitored area, and the harshness of the environment limit the applicability of standard sensors. In this paper, we focus on one of the scattering mechanisms, which take place in fibers, upon which distributed sensing may rely, i.e., the Rayleigh scattering. One of the main advantages of Rayleigh scattering is its higher efficiency, which leads to higher SNR in the measurement; this enables measurements on long ranges, higher spatial resolution, and, most importantly, relatively high measurement rates. The first part of the paper describes a comprehensive theoretical model of Rayleigh scattering, accounting for both multimode propagation and double scattering. The second part reviews the main application of this class of sensors.

The Characterization of Optical Fibers for Distributed Cryogenic Temperature Monitoring.

Thanks to their characteristics, optical fiber sensors are an ideal solution for sensing applications at cryogenic temperatures, such as the monitoring of superconducting devices. Their applicability at such temperatures, however, is not immediate as optical fibers exhibit a non-linear thermal response which becomes rapidly negligible below 50 K. A thorough analysis of such a response down to cryogenic temperatures then becomes necessary to correctly translate the optical interrogation readings into the actual fiber temperature. Moreover, to increase the fiber sensitivity down to a few kelvin, special coatings can be used. In this manuscript we described the thermal responses experimental characterization of four commercially available optical fiber samples with different polymeric coatings in the temperature range from 5 K to 300 K: two with acrylate coatings of different thickness, one with a polyimide coating and one with a polyether-ether-ketone (PEEK) coating. Multiple thermal cycles were performed consecutively to guarantee the quality of the results and a proper estimate of the sensitivity of the various samples. Finally, we experimentally validated the quality of the measured thermal responses by monitoring the cool down of a dummy superconducting link from room temperature to approximately 50 K using two fibers coated, respectively, in acrylate and PEEK. The temperatures measured with the fibers agreed and matched those obtained by standard electronic sensors, providing, at the same time, further insight in to the cool-down evolution along the cryostat.

Machine Learning Estimation of the Phase at the Fading Points of an OFDR-Based Distributed Sensor.

The paper reports a machine learning approach for estimating the phase in a distributed acoustic sensor implemented using optical frequency domain reflectometry, with enhanced robustness at the fading points. A neural network configuration was trained using a simulated set of optical signals that were modeled after the Rayleigh scattering pattern of a perturbed fiber. Firstly, the performance of the network was verified using another set of numerically generated scattering profiles to compare the achieved accuracy levels with the standard homodyne detection method. Then, the proposed method was tested on real experimental measurements, which indicated a detection improvement of at least 5.1 dB with respect to the standard approach.

Experimental characterization of group and phase delays induced by bending and twisting in multi-core fibers.

The local variations of group and phase propagation delays induced by bending and twisting a coupled core three-core fiber are experimentally characterized, for the first time, to the best of our knowledge, along the fiber length, with millimeter-scale spatial resolution. The measurements are performed by means of spectral correlation analysis on the fiber's Rayleigh backscattered signal, enabling for a distributed measurement of the perturbation effects along the fiber length. A mathematical model validating the experimental results is also reported.

Fast and direct measurement of the linear birefringence profile in standard single-mode optical fibers.

Phase birefringence in optical fibers typically fluctuates over their length due to geometrical imperfections induced from the drawing process or during installation. Currently commercially available fibers exhibit remarkably low birefringence, prompting a high standard for characterization methods. In this work, we detail a method that uses chirped-pulse phase-sensitive optical time-domain reflectometry to directly measure position-resolved linear birefringence of single-mode optical fibers. The technique is suitable for fiber characterization over lengths of tens of kilometers, relying on a fast measurement ($ {\sim} 1\,\, {\rm s} $∼1s) with single-ended access to the fiber. The proposed method is experimentally validated with three different commercial single-mode optical fibers.

High-frequency high-resolution distributed acoustic sensing by optical frequency domain reflectometry.

A data analysis algorithm for OFDR-based distributed acoustic sensing (DAS) is proposed, which achieves high acoustic bandwidths of tens of kilohertz with sharp spatial resolutions in the order of centimeters. The non-idealities of the setup as well as the phase noise affecting the measurement are analyzed and a method to compensate them is experimentally demonstrated. The performance of the sensor is evaluated by extensive experimental tests, showing the viability of the proposed technique to achieve high frequency and high spatial resolution distributed acoustic sensing.

Analysis of modal coupling due to birefringence and ellipticity in strongly guiding ring-core OAM fibers.

After briefly recalling the issue of OAM mode purity in strongly-guiding ring-core fibers, this paper provides a methodology to calculate the coupling strength between OAM mode groups due to fiber perturbations. The cases of stress birefringence and core ellipticity are theoretically and numerically investigated. It is found that both perturbations produce the same coupling pattern among mode groups, although with different intensities. The consequence is that birefringence causes the highest modal crosstalk because it strongly couples groups with a lower propagation-constant mismatch. The power coupling to parasitic TE and TM modes is also quantified for both perturbations and is found to be non-negligible. Approximate modal crosstalk formulas valid for weakly-guiding multi-core fibers, but whose parameters are adapted to the present case of strongly guiding OAM fibers, are found to provide a reasonable fit to numerical results. Finally, the effect that modal coupling has on OAM transmission is assessed in terms of SNR penalty.

Robust Depth Estimation for Light Field Microscopy.

Light field technologies have seen a rise in recent years and microscopy is a field where such technology has had a deep impact. The possibility to provide spatial and angular information at the same time and in a single shot brings several advantages and allows for new applications. A common goal in these applications is the calculation of a depth map to reconstruct the three-dimensional geometry of the scene. Many approaches are applicable, but most of them cannot achieve high accuracy because of the nature of such images: biological samples are usually poor in features and do not exhibit sharp colors like natural scene. Due to such conditions, standard approaches result in noisy depth maps. In this work, a robust approach is proposed where accurate depth maps can be produced exploiting the information recorded in the light field, in particular, images produced with Fourier integral Microscope. The proposed approach can be divided into three main parts. Initially, it creates two cost volumes using different focal cues, namely correspondences and defocus. Secondly, it applies filtering methods that exploit multi-scale and super-pixels cost aggregation to reduce noise and enhance the accuracy. Finally, it merges the two cost volumes and extracts a depth map through multi-label optimization.

Statistical analysis of nonlinear coupling in a WDM system over a two mode fiber.

We study the effect of nonlinear coupling in a WDM configuration over a two-mode fiber. A statistical analysis is presented that takes into account the effect of the random phase-sensitive amplification or depletion. Our results show high nonlinear coupling between the modes. We have quantified the channel power fluctuations, due to the wave phase random variations, at the output of the fiber. We also investigate the effect of random linear mode coupling on the nonlinear mode coupling.

[99mTc]duramycin for cell death imaging: Impact of kit formulation, purification and species difference.

INTRODUCTION: [99mTc]duramycin is a SPECT tracer for cell death imaging. We evaluated the impact of kit formulation, purification and species difference on the pharmacokinetic profile and cell death targeting properties of [99mTc]duramycin in order to define the optimal conditions for (pre-)clinical use. METHODS: Three kits were prepared (A: traditional formulation, B: containing 1/3 of ingredients, C: containing HYNIC-PEG12-duramycin). Following labeling, the kits were used without purification, or with SPE or HPLC purification. The pharmacokinetic profile was evaluated in mice and rats at 24 h post tracer injection (p.i.). Non-specific accumulation of [99mTc]duramcyin was studied by µSPECT imaging in chemotherapy treated COLO205 tumor bearing mice pre-treated with cold duramycin (0.01-50 µg). Cell death targeting ability of the kits displaying the best pharmacokinetic profile was compared in a treatment response study in COLO205 tumor bearing mice treated with conatumumab (anti-DR5 antibody). RESULTS: HPLC purification of kit prepared [99mTc]duramycin and reducing the amount of kit ingredients resulted in the best pharmacokinetic profile with low accumulation in liver, spleen and kidneys. The use of PEGylated [99mTc]duramycin required longer circulation times (> 4 h pi) to obtain good imaging characteristics. Pre-treatment with duramycin significantly decreased tracer uptake in chemotherapy treated tumors in a dose-dependent manner. A blocking dose of 50 µg significantly increased non-specific accumulation in liver and spleen. Non-specific accumulation of [99mTc]duramycin was however demonstrated to be species dependent. HPLC purified kit A (5.21±1.71 %ID/cc) and non-purified kit B (1.68±0.46 %ID/cc) demonstrated a significant increase in tumor uptake compared to baseline following conatumumab treatment. CONCLUSIONS: To obtain [99mTc]duramycin with favorable imaging characteristics for cell death imaging in mice [99mTc]duramycin needs to be prepared with high specific activity by applying HPLC purification. The need for HPLC purification appears to be a species dependent phenomenon and might therefore not be required for clinical translation.

Distributed optical fibre sensing for early detection of shallow landslides triggering.

A distributed optical fibre sensing system is used to measure landslide-induced strains on an optical fibre buried in a large scale physical model of a slope. The fibre sensing cable is deployed at the predefined failure surface and interrogated by means of optical frequency domain reflectometry. The strain evolution is measured with centimetre spatial resolution until the occurrence of the slope failure. Standard legacy sensors measuring soil moisture and pore water pressure are installed at different depths and positions along the slope for comparison and validation. The evolution of the strain field is related to landslide dynamics with unprecedented resolution and insight. In fact, the results of the experiment clearly identify several phases within the evolution of the landslide and show that optical fibres can detect precursory signs of failure well before the collapse, paving the way for the development of more effective early warning systems.

The Label Matters: µPET Imaging of the Biodistribution of Low Molar Mass 89Zr and 18F-Labeled Poly(2-ethyl-2-oxazoline).

Poly(2-alkyl-2-oxazoline)s (PAOx) have received increasing interest for biomedical applications. Therefore, it is of fundamental importance to gain an in-depth understanding of the biodistribution profile of PAOx. We report the biodistribution of poly(2-ethyl-2-oxazoline) (PEtOx) with a molar mass of 5 kDa radiolabeled with PET isotopes 89Zr and 18F. 18F-labeled PEtOx is prepared by the strain-promoted azide-alkyne cycloaddition (SPAAC) of [18F]fluoroethylazide to bicyclo[6.1.0]non-4-yne (BCN)-functionalized PEtOx as many common labeling strategies were found to be unsuccessful for PEtOx. 89Zr-labeled PEtOx is prepared using desferrioxamine end-groups as a chelator. Five kDa PEtOx shows a significantly faster blood clearance compared to PEtOx of higher molar mass while uptake in the liver is lower, indicating a minor contribution of the liver in excretion of the 5 kDa PEtOx. While [18F]-PEtOx displays a rapid and efficient clearance from the kidneys, 5 kDa [89Zr]-Df-PEtOx is not efficiently cleared over the time course of the study, which is most likely caused by trapping of 89Zr-labeled metabolites in the renal tubules and not the polymer itself, demonstrating the importance of selecting the appropriate label for biodistribution studies.

Distributed characterization of localized and stationary dynamic Brillouin gratings in polarization maintaining optical fibers.

We experimentally generate localized and stationary dynamic Brillouin gratings in a 5 m long polarization maintaining fiber by phase-modulation of the pumps with a pseudo-random bit sequence. The dynamic Brillouin gratings are characterized in terms of length, bandwidth, group delay and group delay ripple, optical signal-to-noise ratio and peak to sidelobe ratio by measuring the distribution of the complex reflected signal along the fiber through swept-wavelength interferometry. By numerical processing, the performance of an optimal modulation format enabling null off-peak reflections are estimated and compared to the pseudo-random bit sequence case.

Cryogenic-temperature profiling of high-power superconducting lines using local and distributed optical-fiber sensors.

This contribution presents distributed and multipoint fiber-optic monitoring of cryogenic temperatures along a superconducting power transmission line down to 30 K and over 20 m distance. Multipoint measurements were conducted using fiber Bragg gratings sensors coated with two different functional overlays (epoxy and poly methyl methacrylate (PMMA)) demonstrating cryogenic operation in the range 300-4.2 K. Distributed measurements exploited optical frequency-domain reflectometry to analyze the Rayleigh scattering along two concatenated fibers with different coatings (acrylate and polyimide). The integrated system has been placed along the 20 m long cryostat of a superconducting power transmission line, which is currently being tested at the European Organization for Nuclear Research (CERN). Cool-down events from 300-30 K have been successfully measured in space and time, confirming the viability of these approaches to the monitoring of cryogenic temperatures along a superconducting transmission line.

Distributed measurement of high electric current by means of polarimetric optical fiber sensor.

A novel distributed optical fiber sensor for spatially resolved monitoring of high direct electric current is proposed and analyzed. The sensor exploits Faraday rotation and is based on the polarization analysis of the Rayleigh backscattered light. Preliminary laboratory tests, performed on a section of electric cable for currents up to 2.5 kA, have confirmed the viability of the method.

Widely time-dispersion-tuned fiber optical oscillator and frequency comb based on multiple nonlinear processes.

An all-fiber optical oscillator based on three nonlinear processes, namely stimulated Raman scattering and broad-band and narrow-band optical parametric amplification, is presented and experimentally characterized. The wavelength tuning is achieved by means of the time-dispersion technique and spans over 160 nm. Through the same technique a fast tunable optical frequency comb has been realized exploiting cascaded four-wave mixing.