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A miniaturized fiber-optic laser Doppler velocimetry sensor has been developed to measure the local blood velocity
in vivo. The laser beam emitted from the sensor tip can be focused at any distance between 0.1 and 0.5 mm from
the tip. Consequently, the sensor has a sufficiently high signal-to-noise ratio to measure the local velocity in almost
any...
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Context 1
... prevent reductions to the fiber diameter and fiber strength during chemical etching when fabricating the convex lens-like fiber tip, the fiber sidewall was coated with a photoresist (Tokyo Ohka Kogyo Co. Ltd., OFPR800). Figure 6 shows examples of the frequency spectrum of the time-averaged Doppler signal, and Figure 7 shows velocity profiles measured in model vessels at a volumetric flow rate of Q = 0.4 L/min. The vertical axis in Figure 6 shows the probability density function (PDF) of the time-averaged ...Context 2
... vertical broken lines in Figure 6 indicate the Doppler frequency corresponding to the axial flow velocity, which is calculated from the relationship between the volumetric flow rate and the parabolic velocity profile of laminar Poiseuille flow. The parabolic curves in Figure 7 show the velocity profiles for Poiseuille flow calculated from the volumetric flow rate. The solid and dashed lines are the theoretical velocity profiles in tubes with diameters of 6.0 and 5.1 mm, respectively, and the double circle points indicate the water flow velocity profiles measured using the dual beam mode (fringe-type) LDV system. ...Context 3
... the injection needle used to insert the fiber optic LDV probe locally disturbed the flow field, the local flow velocity at z = 3 mm (i.e., on the surface of the upper wall) could not be measured accurately. By assuming Poiseuille flow and a tube diameter of 5.1 mm which is suitable for measuring the velocity profile by this sensor, the measured velocity profile agrees well with the theoretical velocity profile, as indicated by the broken line in Figure 7. Because the model vessel was elliptically deformed by its own weight or by the high pressure drop in the tube caused by high viscous blood flow, the distance that the probe was translated was 0.9 mm shorter than the tube inner diameter. ...Citations
... Optical fiber flow rate sensor has developed rapidly due to its unique characteristics such as high sensitivity, compact size, anti-electromagnetic interference and easy integration [13][14][15], which has been used widely in recent years [16][17][18][19]. Most optic fiber flow rate sensors mainly rely on laser Doppler velocimeter (LDV) [20,21], "hot wire" [22,23], and some special structure [15,24,25]. The laser used in LDV is easily absorbed by living cells, tiny particles and suspended particulates, as a result, the intensity of pump laser decreases dramatically, which has great limitations in flow rate measuring. ...
A novel fiber-tip micro flowmeter based on optofluidic microcavity filled with silver nanoparticles solutions (SNS) is proposed. CW fiber laser was used to heat SNS that can emit heat obviously due to the excellent optic-thermo effect. The heat generated by the silver nanoparticles would be taken away as the microfluidic flows over the fiber microcavity until thermal balance is established under different velocity. The effective refractive index (RI) of the SNS changed followed by temperature of the thermal balance. The dips of the Fabry–Perot interference spectrum shift and the flow velocity can be demodulated. Moreover, the sensor can measure the flow rate with a high sensitivity due to the superior thermal conductivity and specific heat capacity of sidewalls. The max flow rate sensitivity can reach 1.5 nm/(μL/s) in the large range of 0–5 μL/s with a detection limitation (DL) of 0.08 μL/s. The Micron scale probe-type flowmeter has strong robustness and can be used to measure flow rate in tiny space. The heating medium also has an excellent biological compatibility and is not contact with the fluidics directly. As such, we believe that the proposed fiber-tip micro flowmeter has great application potentials in haematology, oil prospecting, ocean dynamics and drug research.
... The flow inside a vessel of a living organism is not constant across its transversal section [26]. This fact produces that MBs move with a relative velocity between them within the same vessel [27]. ...
Localization plays a significant role in the production of ultrasound localization microscopy images. For instance, detecting more microbubbles reduces the time of acquisition, while localizing them more accurately improves the resolution of the images. Previous approaches to compare the multiple localization algorithms rely on numerical simulation of a single steady microbubble, with or without modeling its nonlinear response. In real-life situations, vessels have a nonconstant velocity profile, which creates relative movement, producing dynamically overlapped microbubbles even at low concentrations. These complexities deteriorate the behavior of the localization algorithms. To incorporate these effects on the characterization of the localization methods, we designed a virtual medium containing four microtubes of different inner diameters, where single-pixel microbubbles were allowed to flow within each microtube with a parabolic velocity profile. A finite difference method was used to simulate the propagation of ultrasound waves to obtain B-mode images that fed four direct microbubbles localization algorithms (i.e., weighted centroid, 2D-spline interpolation, parabolic fitting, and onset detection). The performance of these methods was quantified using the number of microbubbles detected, the microbubbles distribution, the full width at half maximum, the maximum velocity, and the computational time as metrics. Our simulation results suggest that 2D-spline and paraboloid fitting were the best methods, detecting 100% of the microbubbles with an error in their distribution of 249 and 244 microbubbles, respectively. Both methods with a computational time cost of 18% and 7% lower than weighted centroid, respectively. We also present an experimental comparison of these localization methods, finding results similar to the numerical ones.
... Refinements to this measurement paradigm were undertaken in a wide range of subsequent studies [102][103][104], which included deploying the sensor fibre via needles and micromanipulators [95,[105][106][107]. In 2014, Tajikawa et al. showed that the velocity distribution of human, caprine and bovine blood could be measured very accurately with LDV [108]. Positioning a bare fibre into the blood stream can yield valuable feasibility data. ...
Fibre optic sensors are well suited to measuring fluid flow in many contexts, and recently there has been burgeoning interest in their application to direct, invasive measurement of blood flow within human vasculature. Depending on the sensing method used and assumptions made, these intravascular measurements of blood flow can provide information about local blood velocity, volumetric flow, and flow-derived parameters. Fibre optic sensors can be readily integrated into medical devices, which are positioned into arteries and veins to obtain measurements that are inaccessible or cumbersome using non-invasive imaging modalities. Measurements of flow within coronary arteries is a particularly promising application of fibre optic sensing; recent studies have demonstrated the clinical utility of certain flow-based parameters, such as the coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR). In this review, research and development of fibre optic flow sensors relevant to intravascular flow measurements are reviewed, with a particular focus on biomedical clinical translation.
... En la experimentación, este extremo de la fibra se acerca (a la distancia de 35 cm) al objeto de estudio, que será un objeto en régimen dinámico, ya sea en vibración, circulación, rotación, etc. Cuando el objeto de estudio pasa por el volumen de medida, se produce un efecto de dispersión de los haces incidentes. Desplazando su frecuencia por efecto Doppler (ver Tsutomu Tajikawa et al. 2012). La misma lente recoge por reflexión, la información de la luz dispersada, la dirige ahora a la fibra central, que está conectada al elemento detector, y finalmente se registran las señales en un osciloscopio, tal y como se muestra en la Figura 5.1, y Figura 5.2. ...
Experimental proposal for the development of a Doppler Laser Velocimeter that allows to detect vibrations frecuencies more precisely, with lower noise levels in the signal than those presented in a self manufacturing system based on a prism arrangement and lenses through the implementation of an optical fiber system that will define the focal length to establish the measurement volumen, in wich the frecuency variations caused by induced mechanical vibrations can be detected. Preliminary tests are presented with the adaptation of the optical fiber, from data collection to processing through an FFT program developed in Matlab, where the highest peaks caused by vibrations will be located
... The sensor will be formed as needed to be able to detect pH values. Some of them are high accuracy, not affected by electric and magnetic fields, do not cause sparks, and send information very quickly [2][3][4][5][6]. ...
This research aims to develop fiber optic sensors that can be used to measure acid rain
levels. This fiber optic sensor uses the evanescent wave type method. SFP (Small Form-factor
Pluggable) Transceiver with a wavelength of 1310nm is used as a fiber optic transmitter and
receiver, while the Optical Power Meter (OPM) is used as a validator to test the developed sensor
capability. The measurement results indicate the presence of loses successfully detected by OPM
and SFP Transceiver. It appears that the maximum value of pH level has been successfully
detected with a range of values of 8.72 dBm to 9.75 dBm and 8.7 dBm to 9.74 dBm respectively
using SFP Transceiver and OPM. Good results during the validation process show that the fiber
optic sensor has successfully worked with a strong correlation of 0.78 to monitor acid rain levels.
... Scalise, Steenbergen and Mul [7] reported intra-arterial blood flow velocimetry using self-mixing feedback in a laser diode. The use of a fiber with a convex lens-like tip has been investigated by Tajikawa, Ishihara, Kohri and Ohba [11], but only to measure red cell suspension flow velocity. Influence of the insertion angle was investigated in this work and it was shown that laser Doppler velocimetry was not effective for an angle of 0°corresponding to the fiber pointing in the same direction as the flow. ...
... The flat portion of the spectrum may be attributed to a range of frequency shifts corresponding to the continuous range of velocities exhibited in the parabolic Poiseuille profile. Tajikawa, Ishihara, Kohri and Ohba [11] observed a similar spectrum behavior in a configuration closer to the one we present in this work. We believe that in our configuration, the flat portion of the spectrum corresponds to a range of velocities and movement directions inside the volume probed by the laser light. ...
This work describes the implementation of a compact system allowing measurement of blood flow velocity using laser Doppler velocimetry in situ. The compact setup uses an optical fiber acting as an emitter and receptor of the signal. The signal is then recovered by a photodiode and processed using a spectrum analyzer. The prototype was successfully tested to measure microbead suspension and whole blood flow velocities in a fluidic chip. Fibers with hemispherical lenses with three different radius of curvature were investigated. This simple yet precise setup would enable the insertion of the fiber via a medical catheter to monitor blood flow velocity in non superficial vessels where previous reported techniques cannot be implemented.
... There are a number of techniques to measure blood velocity such as thermal principles, ultrasound and lasers, an example of this is FloWire TM Cardiometrics amongst many [6,[14][15][16]. However, they do have limitations such as being difficult to incorporate into a multi-lumen catheter, not being able to measure within the flow range required for REBOA and requiring large equipment with mains power supply. ...
... However, some serious problems remain because light is easily absorbed in the blood, and multiple scattering events can occur due to the high concentration of erythrocytes in blood (human standard hematocrit H ct = 45% which is the percentage of the total volume of blood occupied by blood cells of mainly erythrocytes, leukocytes and platelets). In order to overcome these shortcomings, we have developed herein, a novel and improved fiberoptic LDV sensor, using which we were able to measure the flow velocity of a highly concentrated suspension such as blood [5,6]. This sensor had a convex lens-like surface on its tip, which allowed the emitted light from the sensor to be focused and to form a very small sampling volume at the point where the intensity of the light was highest. ...
... The composition rate and etching time were HF: NH 4 F: H 2 O= 0.2:1.0:0.5 and t etch = 5 hours, respectively. These values were determined using the methods described in previous studies [6,8]. Fig. 1 (b) shows the microscopic image of a fiber tip used as a sensor, which was fabricated by chemical etching to have convex lens-like surface. ...
... The insertion angle is defined as the angle between the incident laser and flow vectors. From previous studies [6,8], the insertion angle was determined to be θ=60°, for which a Doppler signal with the highest signal to noise ratio was obtained and the error of the insertion angle made a small contribution to the calculation error. ...
A novel, less invasive, miniaturized fiber-optic laser Doppler velocimetry (LDV) sensor, which can be directly inserted into a blood vessel was developed for clinical use in measurements of local blood velocity. A convex lens-like surface was formed by a chemical etching on the fiber’s tip that had a core diameter of 50 μm. A laser beam that was emitted from the fiber’s tip was focused and formed the measuring volume. This fiber sensor was inserted at an insertion angle of 60° through an injection needle, into the flow duct of an acrylic pipe in which highly concentrated fluid, such as whole blood, was flowing in a pulsatile manner. The flow was modeled after human middle cerebral arterial flow. In this study, the local flow velocity and velocity profile across the duct were measured in the pulsatile flow of a dense suspension of a white pigment. The results were compared both with the results obtained using a fringe-mode LDV and with the results that were calculated on the basis of Womersley's oscillatory flow theory. Consequently, it was found that the local velocity and its profile in the pulsatile flow can be successfully measured using the present fiber-optic LDV sensor, which proved the capability of the sensor as a diagnostic device.
Le terme « cancer » désigne un ensemble de maladies dont la caractéristique commune est une prolifération cellulaire anormale en partie liée à l’accumulation de modifications génétiques. Le cancer est un défi majeur de santé publique avec plus de 18 millions de nouveaux cas de cancer et 9 millions de décès recensés en 2018 dans le monde.A ce jour la confirmation de la maladie se fait quasi-systématiquement par l’intermédiaire d’une biopsie solide consistant à extraire un échantillon tissulaire de la tumeur via un acte chirurgical invasif. La recherche se concentre depuis ces dernières décennies sur la mise au point de nouveaux procédés de biopsie liquide. Leur principe repose sur le prélèvement de fluides corporels, notamment le sang, pour la détection de marqueurs tumoraux tels que l’ARN et l’ADN circulants, les vésicules extracellulaires et les Cellules Tumorales Circulantes (CTCs). La biopsie liquide est beaucoup moins invasive, son usage en routine clinique permettrait d’augmenter la fréquence de l’analyse des biomarqueurs et d’améliorer le suivi de la tumeur dans le temps. Ce concept est prometteur dans le cadre d’une personnalisation de la prise en charge des patients, nécessaire face à l’hétérogénéité des pathologies cancéreuses.Parmi les biomarqueurs accessibles via la biopsie liquide, la capture et l’analyse des CTCs présentent un vif intérêt au sein de la communauté scientifique pour les possibilités d’avancées entrouvertes dans le domaine de l’oncologie. La quantité de ces cellules détachées de la tumeur primaire et disséminées dans le sang est notamment liée à l’agressivité du cancer et au potentiel métastatique. Toutefois, l’utilisation des CTCs pour la prise de décision clinique ne fait pas encore consensus, faute d’une technologie fiable et robuste pour la mettre en œuvre. En effet, atteindre une sensibilité suffisante pour la capture sélective de ces cellules rares à partir d’un fluide complexe tel que le sang est un défi technologique (quelques CTCs/ml de sang).Dans la perspective d’apporter une solution technologique fiable, des micro-dispositifs innovants ont été développés pour la capture de CTCs dans le sang. Les dispositifs comportent une membrane filtrante sur laquelle les CTCs sont préférentiellement isolées car elles sont de tailles plus importantes mais aussi plus rigides que les cellules sanguines saines. Cette technologie a fait l’objet d’un transfert industriel à partir duquel est née la start-up SmartCatch en 2016. Le cœur d’activité de l’entreprise est le développement de ces micro-dispositifs de capture, les S-MDCs, afin de les rendre accessibles au sein des unités de recherches et du milieu hospitalier.C’est dans le contexte du développement des S-MDCs que s’inscrivent les travaux de cette thèse CIFRE en collaboration entre SmartCatch et le LAAS-CNRS. Le fil conducteur de cette thèse repose sur une évolution vers des dispositifs capables de fournir des informations sur le processus de capture en temps réel à l’utilisateur. Les informations ciblées sont la détection des évènements de capture cellulaire in situ ainsi qu’un suivi de la vitesse de l’écoulement sanguin au voisinage des S-MDCs. L’accès à ces informations permettrait d’établir une calibration et un protocole d’utilisation précis, nécessaires à l’introduction de ces dispositifs en routine clinique. Dans cette perspective, deux pistes principales ont été explorées au cours de la thèse afin de répondre à ces deux problématiques. La première repose sur l’intégration de microélectrodes pour permettre la détection électrique des cellules capturées. La seconde repose sur un système de vélocimétrie Doppler pour le suivi en temps réel de l’évolution de la vitesse d’écoulement au voisinage du S-MDCs. Le document de thèse détaille les procédés de fabrication de ces micro-dispositifs, des études préliminaires faisant objet de preuve de concept, ainsi que les perspectives de développement pour leur introduction en routine clinique.
