Single Optical Fiber Probe Research Articles

Commentary: Use of a Single-Fiber Optical Probe for the Detection of Tumor Fluorescence in High-Grade Glioma.

Commentary: Use of a Single-Fiber Optical Probe for the Detection of Tumor Fluorescence in High-Grade Glioma.

Use of a Single-Fiber Optical Probe for the Detection of Tumor Fluorescence in High-Grade Glioma.

High-grade glioma (HGG) is the most common primary brain tumor in adults. The overall median survival is between 14 and 16 months. Fluorescence-guided surgery by detection of protoporphyrin IX (PpIX) fluorescence has been shown to improve the extent of resection, translating to improved progression-free survival. Microscope-based fluorescence detection techniques are associated with several pain points, some of which may be addressed by using contact-based spectroscopy. We aimed to investigate the accuracy of an optical fiber at detecting PpIX fluorescence by performing real-time spectroscopy in patients with HGG. Adult patients undergoing fluorescence-guided surgery for suspected HGG were recruited prospectively. Intraoperatively, samples from cortex, white matter, and tumor were taken. These samples were interrogated using standard white and blue light microscope techniques and the optical fiber. These specimens were then assessed by neuropathology to determine whether the tumor tissue was present within them. We collected 89 samples from 28 patients. There was an equal ratio of men to women, with a median age of 66.5 years. The accuracy of the probe for detecting PpIX fluorescence was 75.9%, compared with 56.6% for the operating microscope, with a significant improvement in sensitivity (χ2 = 11.84, P < .001). The optical fiber probe was more accurate than the operating microscope for detecting PpIX fluorescence. This technology has potential value in improving the accuracy of fluorescence-guided surgery and has potential practical benefits relating to surgical workflow.

In-situ detection scheme for EGFR gene with temperature and pH compensation using a triple-channel optical fiber biosensor

An advanced multi-parameter optical fiber sensing technology for EGFR gene detection based on DNA hybridization technology is demonstrated in this paper. For traditional DNA hybridization detection methods, temperature and pH compensation can not be realized or need multiple sensor probes. However, the multi-parameter detection technology we proposed can simultaneously detect complementary DNA, temperature and pH based on a single optical fiber probe. In this scheme, three optical signals including dual surface plasmon resonance signal (SPR) and Mach-Zehnder interference signal (MZI) are excited by binding the probe DNA sequence and pH-sensitive material with the optical fiber sensor. The paper proposes the first research to achieve simultaneous excitation of dual SPR signal and Mach-Zehnder interference signal in a single fiber and used for three-parameter detection. Three optical signals have different sensitivities to the three variables. From a mathematical point of view, the unique solutions of exon-20 concentration, temperature and pH can be obtained by analyzing the three optical signals. The experimental results show that the exon-20 sensitivity of the sensor can reach 0.07 nm nM−1, and the limit of detection is 3.27 nM. The designed sensor gives a fast response, high sensitivity, and low detection limit, which is important for the field of DNA hybridization research and for solving the problems of biosensor susceptibility to temperature and pH.

Characteristics of rising temperatures through laser irradiation using a temperature sensor integrated optical fiber probe for soft tissue ablation

A new structure composed of silica optical fibers for soft tissue ablation is proposed and fabricated in this study. Laser irradiation and temperature monitoring are simultaneously performed using a wavelength-division multiplexing technique with a single optical fiber probe. A 1.55-μm wavelength range light is used for temperature measurement. The fabricated Fabry–Perot interference temperature sensor comprising a glass capillary and a graded-index multimode fiber exhibits good temperature sensor characteristics. The probe end is terminated with a glass capillary having a declined glass cap. This portion suppresses the reflected light backward to the incident fibers. Because the reflected light at this portion does not affect the interference of internal reflected light, regardless of the outer medium, stable temperature measurement is confirmed. A 1.48-μm laser irradiation method is investigated as a thermal source for soft tissue ablation. The characteristics of rising temperatures through laser irradiation of chicken-breast meat are investigated and indicate sufficient temperature increases for thermal ablation of soft tissue. A good estimation of the thermal protein denaturation region is achieved through a simple analytical equation using the measured value at the fiber tip temperature sensor.

Measurement of droplet size and velocity based on a single tapered fiber optical reflectometer

A single optical fiber probe (OFP) is used to measure the velocity and size of droplet falling in the air. By analyzing the interference waves formed by two reflected lights from the droplet surface and the fiber core interface, the fiber optical reflectometer (FOR) is mainly studied in this paper. The wave optics simulation was firstly applied to verify the FOR principle of velocity measurement. Then an experiment system which can generate droplets with different velocities and sizes was designed. Through comparing the results of OFP with photography method, the absolute relative error of chord length measured was within 1.3%. During the study, it was observed that the intensity of oscillation waves is closely related to the contact position between probe and droplet, so a method for predicting droplet diameter by OFP is proposed. Compared with photography method, the root mean square error of the predicted diameter is 0.051 mm.

The profiles of the local void fraction close to the heated wall in the subcooled flow boiling

Flow boiling in the subcooled liquid condition is characterized by the complex interplay of phenomena such as bubble detachment from the wall, condensation in the flow, and the interaction between bubbles on which non-drag forces are exerted. However, the fundamental characteristics of the flow boiling in the subcooled liquid condition remain uncharted. In particular, a distribution of the bubbles close to the heated wall is not well understood. Here, we measure the void fraction in the steam-water mixture which is representing the distribution of bubbles by using a single sensor optical fiber probe with fine radial spacing in the close vicinity of the heated wall. We show that the profile of the void fraction along the radial direction of the flow channel is altered by the flow condition. In particular, the peak of the void fraction can be shifted towards the heated wall when there are fast bubbles close to the heated wall.

Noninvasive assessment of oral lesions using elastic light single-scattering spectroscopy: a pilot study.

In the present study, we investigated the potential application of elastic light single-scattering spectroscopy (ELSSS) as a noninvasive, adjunctive tool to differentiate between malignant and benign oral lesions in vivo. ELSSS spectra were acquired from 52 oral lesions of 47 patients prior to surgical biopsy using a single optical fiber probe. The sign of the spectral slope was used as a diagnostic parameter and was compared to the histopathology findings to obtain sensitivity and specificity of the ELSSS system in differentiating between benign and malignant tissues. The sign of the spectral slope was positive for the benign tissues and negative for the malignant tissues. Nine malignant lesions and one high-grade dysplasia were correctly classified as cancerous. Six out of the ten low-grade dysplasia were correctly classified as cancerous, and four of them were misclassified as benign. Thirty benign lesions were correctly classified as benign, and two were misclassified as malignant. Our results indicate that the sign of the spectral slope enables the differentiation between malignant and benign oral lesions with a sensitivity of 80% and specificity of 94%. ELSSS has the potential to be developed as an adjunctive screening tool in the noninvasive evaluation of oral lesions in vivo. This new diagnostic system may reduce the number of unnecessary biopsies.

Double domain wavelength multiplexed Fizeau interferometer with high resolution dynamic sensing and absolute length detection

In this work, we present a simple photonic instrument that has the ability of measuring positions, distances and vibrations with very high resolution by means of two Fizeau interferometers (FI), both using the same optical fiber end as a probe tip itself. On the one hand we have a time domain FI powered with a 1310nm laser and monitored by an InGaAs detector providing displacement information with resolution around a tenth of nm but regardless of the absolute position of object and of the displacement sense. On the other, a spectral domain FI version based on a super luminescent source (SLED) centred at 800nm with bandwidth of nearly 40nm is analysed in real time by means of a digital spectrometer. Each spectrum is acquired in a very small time interval and provides information of both length of the cavity as well as its correct sense of evolution. Resolution of this system is lower than its complementary temporal case, but distance and sense measurements are absolute and can be determined successfully by adequate processing of spectral signal.Both interferometers are optically coupled to a single fiber optic probe and are wavelength modulated.Therefore, combination of both sensors results in a new one which allows the correct knowledge of an object or surfaces under test, i.e. a high resolution of displacement data plus its absolute position and true sense of movement.

Intraoperative assessment of laryngeal malignancy using elastic light single-scattering spectroscopy: A pilot study.

The elastic light single-scattering spectroscopy (ELSSS) system is a new tool for the real-time diagnosis of cancerous lesions. In the current study, we have employed ELSSS to investigate its ability in differentiation between normal and cancerous larynx tissues ex vivo. Basic science study in assessment of laryngeal malignancy using spectroscopy. ELSSS spectra of the larynx tissue were acquired using a single-fiber optical probe. Ex vivo spectroscopic measurements were acquired on 95 laryngeal lesions of 40 patients. Average slopes of the spectra in the wavelength range of 450 to 750 nm were calculated. The signs of the spectral slopes were positive for benign and negative for cancerous larynx tissues. Histopathology results were used as a gold standard to define sensitivity and specificity. The ELSSS system correctly defined 38 out of 41 malignant tissues as cancerous; three of them were misclassified as benign. All benign tissues were correctly classified. Moderate, severely dysplastic, and malignant tissues were correctly classified as cancerous. The system could not classify mild dysplastic tissues either benign or cancerous, whereas nearly half of them were classified as benign and the other half as malignant. The signs of the spectral slopes were used as a discrimination parameter between benign and cancerous (moderate, severely dysplastic, and malignant) lesions with a sensitivity and specificity of 94% and 100%, respectively. The ELSSS system has the potential to be used as an adjunctive tool in the diagnosis of cancerous laryngeal tissues in real time and noninvasively. This new diagnostic technique may reduce the number of negative biopsies. NA Laryngoscope, 127:611-615, 2017.

μOCT imaging using depth of focus extension by self-imaging wavefront division in a common-path fiber optic probe.

Optical coherence tomography (OCT) is an attractive medical modality due to its ability to acquire high-resolution, cross-sectional images inside the body using flexible, small-diameter, scanning fiber optic probes. Conventional, cross-sectional OCT imaging technologies have approximately 10-μm axial resolution and 30-μm lateral resolution, specifications that enable the visualization of microscopic architectural morphology. While this resolution is useful for many clinical applications, it is insufficient for resolving individual cells that characterize many diseases. To address this gap, a supercontinuum-laser-based, μm-resolution OCT (μOCT) system and a 500 μm-diameter, extended depth of focus single fiber optic probe for endoscopic and intravascular imaging were designed and fabricated. At the distal tip of the fiber optic probe, a cylindrical waveguide was used to divide the wavefront to provide multiple circular propagation modes. Once transmitted through a relatively high NA lens (NA >0.1), these modes were projected as multiple coaxial foci (~3 μm full width at half maximum (FWHM)) over a greatly extended focal depth range. The distal tip of the probe also contained a common-path reference reflectance to minimize polarization and dispersion imbalances between sample and reference arm light. Measurements showed that the probe provides a 20-fold depth of focus extension, maintaining a 3-5 µm lateral resolution (FWHM of PSF) and a 2 μm axial resolution over a depth range of approximately 1 mm. These results suggest that this new optical configuration will be useful for achieving high-resolution, cross-sectional OCT imaging in catheter/endoscope-based medical imaging devices.

Differentiating cancerous tissues from noncancerous tissues using single-fiber reflectance spectroscopy with different fiber diameters.

Elastic light-scattering spectra acquired with single-fiber optical probes with diameters of 100, 200, 400, 600, 800, 1000, 1200, and 1500 μm were used to differentiate cancerous from noncancerous prostate tissues. The spectra were acquired ex vivo on 24 excised prostate tissue samples collected from four patients. For each probe, the spectra and histopathology results were compared in order to investigate the correlation between the core diameters of the single-fiber optical probe and successful differentiation between cancerous and noncancerous prostate tissues. The spectra acquired using probes with a fiber core diameter of 400 μm or smaller successfully differentiated cancerous from noncancerous prostate tissues. Next, the spectra were acquired from monosized polystyrene microspheres with a diameter of 5.00±0.01 μm to investigate the correlation between the core diameters of the probes and the Mie oscillations on the spectra. Monte Carlo simulations of the light distribution of the tissue phantoms were run to interrogate whether the light detected by the probes with different fiber core diameters was in the ballistic or diffusive regime. If the single-fiber optical probes detect light in the ballistic regime, the spectra can be used to differentiate between cancerous and noncancerous tissues.

Detecting Positive Surgical Margins Using Single Optical Fiber Probe During Radical Prostatectomy: A Pilot Study

To investigate for the potential of detection of positive surgical margins by the elastic light single-scattering spectroscopy (ELSSS) system with a single optical fiber probe during radical prostatectomy. ELSSS spectra in the 450- to 750-nm wavelength regions were obtained from a total of 31 benign tissue samples and 14 malignant tissue samples from 18 patients. The ELSSS spectral data were assessed by comparing these against the "gold standard" histopathology results. Data were analyzed using principal component analysis , followed by linear discriminant analysis. Receiver operating characteristic curve analysis was used for differentiating performance. Classification based on the discriminant score provided a sensitivity of 86% and a specificity of 97%, in differentiating benign from malignant surgical margins of prostate tissues, with a positive predictive value of 0.92, a negative predictive value of 0.94, and the area under the receiver operating characteristic curve of 0.87. The ELSSS system can accurately distinguish between benign and malignant surgical margins of prostate tissues with a high positive predictive value and negative predictive value. It is a promising technique, and it may be a valuable new tool for determining positive surgical margins during radical prostatectomy.

Autofluorescence of liver tissue and bile: Organ functionality monitoring during ischemia and reoxygenation

Autofluorescence (AF) based optical biopsy of liver tissue is a powerful approach for the real-time diagnosis of its functionality. Since increasing attention is given to the bile production and composition to monitor the liver metabolic engagement in surgery and transplantation, we have investigated the bile AF properties as a potential, additional diagnostic parameter. Spectrofluorometric analysis has been performed in real time on a rat liver model of warm ischemia and reperfusion-60 minutes partial portal vein and hepatic artery clamping and subsequent restoration of blood circulation-in comparison with sham operated rats. The AF spectra have been recorded through a single fiber optic probe (366 nm excitation) from both liver tissue and bile, collected from the cannulated bile duct, and analyzed by means of curve fitting procedures. Bile composition has been also analyzed through biochemical assays of bilirubin, total bile acids (TBA) and proteins. Both liver and bile AF signal amplitude and spectral shape undergo changes during induction of ischemia and subsequent reperfusion. The liver tissue response is mainly ascribable to changes in NAD(P)H and flavins and their redox state, largely dependent on oxygen supply, and to the decrease of both vitamin A and fatty acid AF contributions. During comparable times, sham operated rat livers undergo smaller alterations in AF spectral shape, indicating a continuous, slight increase in the oxidized state. Bile AF emission shows a region in the 510-600 nm range ascribable to bilirubin, and resulting from the contribution of two bands, centered at about 515-523 and 570 nm, consistently with its bichromophore nature. Variations in the balance between these two bands depend on the influence of microenvironment on bilirubin intramolecular interchromophore energy transfer efficiency and are likely indicating alteration in a bile composition. This event is supported also by changes observed in the 400-500 nm emission region, ascribable to other bile components. In parallel with the intratissue AF properties, mainly reflecting redox metabolic activities, the bile AF analysis can provide additional information to assess alterations and recovery in the balance of liver metabolic activities.

Elastic Light Single-Scattering Spectroscopy for the Detection of Cervical Precancerous Ex vivo

Potential application of elastic light single-scattering spectroscopy (ELSSS) for differentiating high-grade squamous intraepithelial lesions (HSIL) from non-HSIL tissues was investigated. An ELSSS system was used to acquire spectra from cervix tissues. A single-fiber optical probe with a diameter of 100μm was used for both delivery and detection of white light to and from the cervix tissue. Spectroscopic measurements were acquired from 95 ex vivo biopsy samples of 60 pap smear positive patients and normal cervix tissue from 10 patients after hysterectomy were used as a negative control group. Spectroscopic results of 95 cervix biopsy were compared to the histopathology of the biopsy samples. Sensitivity and specificity of the ELSSS system in the differentiation of HSIL and non-HSIL tissues are 87.5% and 45.6%, respectively, for the pap smear and colposcopy positive biopsy samples. The ELSSS system has the potential for use in real-time diagnosis of HSIL tissues as an adjunct to Papanicolaou test (pap smear) and colposcopy.

Semi-empirical model of the effect of scattering on single fiber fluorescence intensity measured on a turbid medium

Quantitative determination of fluorophore content from fluorescence measurements in turbid media, such as tissue, is complicated by the influence of scattering properties on the collected signal. This study utilizes a Monte Carlo model to characterize the relationship between the fluorescence intensity collected by a single fiber optic probe (FSF) and the scattering properties. Simulations investigate a wide range of biologically relevant scattering properties specified independently at excitation (λx) and emission (λm) wavelengths, including reduced scattering coefficients in the range μ′s(λx) ∈ [0.1 – 8]mm−1 and μ′s(λm) ∈ [0.25 – 1] × μ′s(λx). Investigated scattering phase functions (P(θ)) include both Henyey-Greenstein and Modified Henyey-Greenstein forms, and a wide range of fiber diameters (df ∈ [0.2 – 1.0] mm) was simulated. A semi-empirical model is developed to estimate the collected FSF as the product of an effective sampling volume, and the effective excitation fluence and the effective escape probability within the effective sampling volume. The model accurately estimates FSF intensities (r=0.999) over the investigated range of μ′s(λx) and μ′s(λm), is insensitive to the form of the P(θ), and provides novel insight into a dimensionless relationship linking FSF measured by different df.

偏光した近接場光を用いたナノスケール温度測定手法の開発(&lt;小特集&gt;第1回マイクロ・ナノ工学シンポジウム)

Measurement of temperature distribution at nanometer scale is important for the thermal design of high integrated devices. However, in conventional optical measurement techniques, the spatial resolution is limited by the diffraction limit of light, which is approximately half of the wavelength of the optical beam. Therefore, we have developed a novel optical temperature measurement method in nanometer scale using near-field microscope technique. We newly employed the polarization of light into the measurement principle, since the near-field polarization has a high sensitivity for the refraction index of the sample, which varies with temperature. In this method, the near-field optical fiber probe which can maintain the polarization state is necessary for increasing the measurement sensitivity. Hence, we have newly fabricated the single mode near-field optical fiber probe. In this paper, we report the verification of the new measurement principle and the comparison of the measurement sensitivity with the results using temperature dependence of reflectance.

Experimental study of the effect of dielectric and physical properties on temperature distribution in fluids during continuous flow microwave heating

Temperature data was collected at multiple locations in tap water, saltwater, and carboxymethylcellulose (CMC) solutions heated in a continuous flow microwave system by use of custom made temperature measurement system employing a single fiber optic probe. Tap water, 3% saltwater and 0.5% CMC solution were pumped through a 915 MHz continuous flow microwave system operating at 4 kW at three flow rates of 1 lit/m, 1.6 lit/m and 2 lit/m. Saltwater absorbed most power (3940 W) out of the 4000 W incident power, followed by CMC solutions (2690 W) and tap water (2626 W). Cross-sectional temperature distribution patterns showed that saltwater had the most uniform temperature distribution followed by tap water; CMC exhibited a non-uniform temperature distribution due to viscosity changes and thermal runaway effects. The study was very useful in enhancing the understanding of continuous flow microwave heating process for a variety of material properties and flow rates.

M3-6 偏光した近接場光を用いたナノスケール温度・熱物性測定手法の開発(M3 熱流体デバイス)

Measurement of temperature distribution at nanoscale is absolutely important for the thermal design of high integrated devices. However, in conventional optical measurement techniques, the spatial resolution is limited by the diffraction limit of light, which is approximately half of the wavelength of the optical beam. Therefore, we have developed a novel optical nanoscale temperature measurement method using near-field microscope technique. We newly employed the polarization of light into the measurement principle, since the near-field polarization has a high sensitivity for the refraction index of the sample, which varies with temperature. In this method, highly polarization maintaining near-field optical fiber probe is necessary for increasing the measurement sensitivity. Hence, we have newly fabricated the single mode near-field optical fiber probe. In this paper, we report the verification of the new measurement principle and the comparison of the measurement sensitivity with the results using temperature dependence of reflectance.

Two-phase flow pattern identification using continuous hidden Markov model

This paper presents a new method for identifying two-phase flow regimes from the instantaneous local fluid phase signals using continuous hidden Markov model (CHMM). CHMM is known to be a very strong pattern identifier. Air–water two-phase flows were realized in a transparent vertical tube. The tube length was 2 m, and its inner diameter was 19 mm. The instantaneous local fluid phase signals were collected using a single step index multimode optical fiber probe located at the center and mid-length of the tube. Signal features required in CHMM implementation were extracted using an innovative method. Various aspects of hidden Markov modeling and their effects on the results were studied. The flow pattern results are in very good agreement with photographs of the flow captured during the experiments. In sum, the results show that hidden Markov model has a good potential in identifying two-phase flow patterns.

Quantitative Time-Resolved Fluorescence Spectrum of the Cortical Sarcoma and the Adjacent Normal Tissue

The difference in time-resolved fluorescence spectrum between the cortical sarcoma and the adjacent normal tissue was studied in both experimental and theoretical ways. The Clinical data were obtained in vivo using a time-resolved fluorescence spectrometer employing a single fiber-optic probe for excitation and detection. Tissue was modeled as s-180 sarcoma tumor surrounded with normal muscle and was mediated by the Palladium-porphyrin photosensitizer (Pd-TCPP). The emitted fluorescence was considered as arising from the tumor tissue or the normal muscle, due to the presence of the photosensitizer. A computational code which could simulating time-resolved fluorescence emission was presented and applied to comparing fluorescence decay of photosensitizer in different stages of tumor growth. In this code the different stages of the tumor was modeled through changing the time tau, the delay of the fluorescence photon emission and z (max), the thickness of the tumor. It was found in the in vivo experiment that the fluorescence from tumor tissue decayed more quickly than from the adjacent normal muscle. For the ten rats in the first experiment day, the mean decay constant of tumor T (s) and normal tissue T (n) were 554 and 526 mus, respectively. And T (s) increased with the tumor growth, from 554 mus in the first day to 634 mus in the eighth day while T (s) kept steady. It was believed that the more adequate oxygen supplied by the normal tissue can more effectively quench the fluorescence and in the normal tissue the photosensitizer lifetime is smaller. As a result the simulated time-resolved fluorescence spectrum of normal tissue showed more quickly decay. And the thickness of the tumor can also delay the fluorescence decay. Both the experimental and simulated results indicated that the germination of the tumor would increase the decay constant of the time-resolved fluorescence spectrum. So decay constant of the tumor tissue spectrum should be larger than that of adjacent normal tissue for the reason of hypoxia and overgrowth. This fact could be of use in the tumor diagnoses.