Transducer Tip Research Articles

Applicability of Transnasal Echography for Identification of Internal Carotid Artery.

To study the applicability of transnasal echography for the internal carotid artery (ICA) imaging during endoscopic procedures, primarily nasopharyngectomy. Non-randomized controlled cohort. The tip of a pediatric transducer for transesophageal echography was inserted into each nostril under endoscopic control and placed in the ipsilateral Rosenmuller's fossa. The ICA's internal diameter and distance between the nasopharyngeal wall and the artery's closest point were measured on each side. Two independent examiners measured the same parameters on the axial plane of the skull base computer tomography (CT). Agreement between CT and echography measurements was estimated by the Bland-Altman approach. Twenty-seven ICAs (sides) were available for the echography-CT agreement analysis. Inter method agreement for both parameters was similar to the inter examiner agreement for the CT measurements. Our first study on endoscopic echography demonstrated that this method is applicable, potentially allowing safer transnasal surgery in the ICA vicinity. 3 Laryngoscope, 132:1184-1188, 2022.

Hybrid electromagnetic-ArUco tracking of laparoscopic ultrasound transducer in laparoscopic video.

.Purpose: The purpose of this work was to develop a new method of tracking a laparoscopic ultrasound (LUS) transducer in laparoscopic video by combining the hardware [e.g., electromagnetic (EM)] and the computer vision-based (e.g., ArUco) tracking methods.Approach: We developed a special tracking mount for the imaging tip of the LUS transducer. The mount incorporated an EM sensor and an ArUco pattern registered to it. The hybrid method used ArUco tracking for ArUco-success frames (i.e., frames where ArUco succeeds in detecting the pattern) and used corrected EM tracking for the ArUco-failure frames. The corrected EM tracking result was obtained by applying correction matrices to the original EM tracking result. The correction matrices were calculated in previous ArUco-success frames by comparing the ArUco result and the original EM tracking result.Results: We performed phantom and animal studies to evaluate the performance of our hybrid tracking method. The corrected EM tracking results showed significant improvements over the original EM tracking results. In the animal study, 59.2% frames were ArUco-success frames. For the ArUco-failure frames, mean reprojection errors for the original EM tracking method and for the corrected EM tracking method were 30.8 pixel and 10.3 pixel, respectively.Conclusions: The new hybrid method is more reliable than using ArUco tracking alone and more accurate and practical than using EM tracking alone for tracking the LUS transducer in the laparoscope camera image. The proposed method has the potential to significantly improve tracking performance for LUS-based augmented reality applications.

An alternative explanation for the phasic variations in venous flow

BackgroundPhasic venous flow variation with respiration is surrounded by controversy and not well understood. The current concept assigns a major role to the “abdominal pump.” According to this model, inspiratory increases in abdominal pressure compress the vena cava, increasing its internal venous pressure and propelling blood upstream. Some have assigned a secondary role to the “thoracic pump,” with the negative intrapleural pressure aiding blood flow toward the heart. The aim of the present study was to examine the phasic changes in flow, pressure, and volume in the central veins and named tributaries. MethodsCaliber area changes were measured using intravascular ultrasonography in 37 patients undergoing iliac vein stenting. The pressure was measured in 48 patients using transducer tip catheters with electronic zero calibration. Duplex ultrasound flow in the head and neck and truncal and limb veins during inspiration and expiration was measured in 15 normal volunteers. ResultsThe caliber of the abdominal inferior vena cava had increased by 32% and its lateral pressure had decreased significantly during inspiration. Intravenous pressure in the central veins of the chest and right atrium was positive at 6 to 14 mm Hg. Negative pressures were rarely seen and then only transiently. The internal jugular vein displayed little phasic variation. The upper limb veins displayed weak inspiratory phasicity. Phase polarity was reversed in the lower limbs, with near flow stoppage during inspiration. ConclusionsThese observations conflict with the current notions of venous flow phasicity, which are based on push–pull pressure changes in the abdominal and thoracic veins. The paradoxical inspiratory inferior vena cava caliber increase probably explains the concurrent pressure decrease. Sustained negative pressures in the thoracic central veins and right atrium did not occur. We have proposed an alternate hypothesis for venous flow phasicity based on alternate stretching and relaxation of the mobile section of the great veins with respiratory movement.

A continuum electro-mechanical model of ultrasonic Langevin transducers to study its frequency response

In this paper, a continuum mathematical electro-mechanical model of ultrasonic Langevin transducers has been developed by considering three factors: 3D vibrations, piezoelectric effects, and elements damping. Since the equivalent-circuit methods simulate a continuous system with discrete components, they are valid near one resonance frequency. However, a continuum model is valid in broader frequency ranges. It can also describe the effect of geometries and material properties on the frequency response of transducers. By using the mathematical model, the amplitude of vibrations, mode shape, resonant and anti-resonant frequencies, mechanical quality factor, and frequency response can be achieved for a transducer with a specific geometry and material properties. It would also be reliable to design a transducer and to study its frequency response. A transducer is modeled and then numerically simulated with FEM software of COMSOL, and the results are compared with the model. Then the transducer is fabricated and tested experimentally. The results are compared with the mathematical and numerical models. The analytical resonant frequency obtained with the model is 19,378 Hz, which in comparison with 19,270 Hz of the numerical model and 19,457 Hz of the experimental test, has 0.4% and 0.5% errors, respectively. The vibration amplitude of the transducer's tip at the resonant frequency, obtained by the mathematical model, is 21.2 µm, which is 3.6% lower than the 22 µm obtained using experimental tests. The anti-resonant frequency calculated by the mathematical model is 21,748 Hz, which has a 0.7% variation with the experimental result.

A MEMS-Based Fast-Response Miniature Five-Hole Probe With Optical Pressure Transducers

This paper presents the first realization of a fiber-optic lever-based, miniature five-hole probe (5HP) for aerodynamic flow angle sensing applications. Five MEMS optical transducers are embedded in a hemispheric probe tip to mitigate the pneumatic lag problem of conventional 5HP technology. A silicon die with five optical pressure transducers of $400~\mu \text{m}$ radius is microfabricated from a silicon-on-insulator (SOI) wafer and bonded to a hemispheric tip of 5 mm diameter. The optimal transducer and probe tip designs are determined using lumped element modeling. Laser micromachining is utilized to drill micro holes of about $50~\mu \text{m}$ radius on the hemispheric tip. The optical transduction allows for remotely located electronics. This facilitates probe miniaturization and offers potential for high-temperature capability. The resulting 5HP has a fast response with a modeled settling time of 0.24 ms and a measured high-frequency range of about 3.5 kHz. [2020-0182]

Numerical Optimization of Waveguide Structure in an Ultrasound Brain Stimulation System Using the FDTD Method

Ultrasound stimulation is expected to be capable of transcranial deep and local stimulation to the brain, which is difficult to achieve using conventional electromagnetic stimulation. Once an ultrasound transducer is determined, however, its physical characteristics are hard to change. For obtaining the appropriate irradiation properties, we used a computer simulation of our experimental setup to characterize the optimal shape and size of a waveguide attached to the tip of an ultrasound transducer to target a specific brain region. We obtained an optimal waveguide structure to produce the desired intensity distribution. Our next challenge is to test in our physical setup. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Microglial Involvement in Stress‐induced Prolonged Sympathetic Nervous Excitation in Rats

Hypertension is one of the most important risk factors causing cardiovascular diseases. It has been assumed that hypertension is caused by continuous over‐excitation of the sympathetic nervous system, which is often accompanied by psychological stress. We have previously reported that glial cells, especially astrocytes, are importantly involved in blood pressure elevation during stress and post‐stress recovery period in air jet stress loaded rats. However, it has not been well clarified whether another glial cell, microglia, is also involved in stress‐induced sympathetic nervous excitation. In the present study, we aimed to address this issue using adult rats (n=9, 23–26 weeks age, body weight 300–467g). A blood pressure telemeter was implanted intraperitoneally with a pressure transducer tip in the abdominal aorta under anesthesia. After at least one week recovery period, blood pressure and pulse rate responses to psychological stress were measured in an unanesthetized freely moving condition by blood pressure telemetry system (Kaha Sciences, Auckland, New Zealand). Measurement was first conducted without pretreatment with minocycline, which is an inhibitor of microglial activation. Then, in more than one week after this control measurement, the animal was pretreated with minocycline (25mg/kg/day) for three consecutive days, and blood pressure and pulse rate responses to stress were again measured under the suppression of microglial activation. Air jet stress was loaded to the rat by blowing compressed air to the face of the animal (10L/min, 15min). We recorded blood pressure and pulse rate before, during and after the stress loading, and compared these data between the conditions before and after minocycline pretreatment. Pretreatment with minocycline did not affect either blood pressure or pulse rate in a pre‐stress resting condition. However, after pretreatment with minocycline, stress‐induced augmentation of both blood pressure and pulse rate were attenuated during and after air jet stress loading with statistical significance (paired t‐test). These findings indicate that activated microglia is involved in the augmentation of sympathetic nervous activity during and after stress loading.Support or Funding InformationThis work was supported by JSPS KAKENHI Grant Numbers 17K08559, 17H05540, 18K17783, 19K17386 and 19K17620 and a Grant‐in‐aid of the Cardiovascular Research Fund, Tokyo, Japan.

Role of Microglia in Ventilatory and Blood Pressure Responses to Acute Hypoxia

Microglia induces neuroinflammation in response to intermittent and chronic hypoxia, and enhances ventilatory augmentation and blood pressure elevation during hypoxic exposure. However, the role of microglia in ventilatory and blood pressure responses to acute hypoxia, especially to brief period of hypoxic exposure, has not been well investigated. In the present study we aimed to clarify the role of microglia in ventilatory and blood pressure responses to short duration acute hypoxia. To investigate this issue we conducted experiments using adult rats. A blood pressure telemeter was implanted intraperitoneally with a pressure transducer tip in the abdominal aorta. After at least one week recovery period, ventilatory and blood pressure responses to hypoxia were measured in an unanesthetized freely moving condition by whole body plethysmography and blood pressure telemetry, respectively. Measurement was first conducted without pretreatment with minocycline which is an inhibitor of microglial activation. Then, in more than one week after this control measurement, the animal was pretreated with minocycline for three consecutive days, and ventilatory and blood pressure responses to hypoxia were measured under the suppression of microglial activation. To test hypoxic responses, mild (13% O2, 4 min) and severe (7% O2, 5 min) hypoxia was loaded with a sufficient interval. In results we did not find differences ether in ventilatory or blood pressure response to either level of hypoxia between the conditions before and after pretreatment with minocycline. These results indicate that microglial activation does not affect ventilatory or blood pressure response to short duration acute hypoxia, which is not in agreement with previous reports, and this disagreement may be attributed to the different period of hypoxic loading between the previous reports and our present study, which could you too short to induce neuroinflammatory action by activated microglia.Support or Funding InformationThis work was supported by JSPS KAKENHI Grant Numbers 17K08559, 17H05540, 18K17783, 19K17386 and 19K17620 and a Grant‐in‐aid of the Cardiovascular Research Fund, Tokyo, Japan.

Characterisation of flow behaviour and velocity induced by ultrasound using particle image velocimetry (PIV): Effect of fluid rheology, acoustic intensity and transducer tip size

Acoustic streaming phenomena of ultrasound propagation through liquid media was investigated experimentally employing particle image velocimetry (PIV). Parameters associated with the ultrasonic processor of ultrasonic amplitude (i.e., acoustic power) and transducer tip diameter (i.e., surface area), as well as, fluid rheology (i.e., water, glycerol solution and CMC solution), were studied for their effects on overall flow behaviour and fluid velocity. PIV yielded velocity gradient maps, demonstrating the acoustic streaming phenomena of ultrasound and its associated flow behaviour as a function of ultrasonic amplitude and fluid rheology, whereby increasing amplitude allowed for greater penetration of the acoustic-beam through the bulk of the fluid, and increasing fluid rheology yielded the converse effect. Moreover, upon impingement of the acoustic-beam with the base of vessel, vortex formation occurred, yielding a recirculation pattern. The maximum observed fluid velocities for water, glycerol solution and CMC solution were 0.329 m s−1, 0.423 m s−1, and 0.304 m s−1, respectively (large diameter sonotrode tip for an ultrasonic amplitude of 80%). Furthermore, shear rates were attained (maximum values of 24.25 s−1), and Reynolds numbers were determined in order to assess the degree of turbulence as a function of investigated parameters.

Comparison of HCA and SHO/IMP Control Methodologies for Tip Damping of the Commercial Piezoelectric Transducer

This study investigates and compares Harmonic Control Array (HCA) and Simple Harmonic Oscillator (SHO), or namely Internal Modal Principle (IMP),methodologies for tip damping of the commercial piezoelectric transducer (Mide, Volture PPA-1011) via voltage control under two conditions: (1) Tip displacement at different amplitudes (input) without base vibration input (no disturbance) and (2) by exact opposite of the fist condition; in the presence of base vibration at resonance frequency of the transducer with zero initial condition for tip displacement. Results indicated that HCA is capable to damp both cases and for the first case, with proportional controller alone and for the latter case, via proportional-integral (PI) controller regarding voltage boundary condition at different input and disturbance amplitudes, whereas SHO is unable to control the damping of the transducer tip for the first condition. Alternatively, for the second case, SHO damps remarkably faster than HCA. As an advantage, for both HCA and SHO, optimum gain constants for each case remain unchanged as the amplitude of initial conditions and disturbance vary.

P002 Abnormal surround inhibition of finger tapping task and cerebellar hyper-activation of functional MRI in patients with focal hand dystonia

Introduction Surround inhibition is one physiological mechanism to select neuronal responses and to focus neural activity in the central nervous system. Within the motor system, it is a mechanism by which basal ganglia circuits selectively execute desired motor programs. Clinical features of focal hand dystonia (FHD) are task specific abnormal posturing due to sustained muscle contractions interfering with the performance of the skilled motor tasks. In dystonic patients, abnormal involuntary co-contraction of the hand muscles is associated with a disruption of SI. Objectives The aim of the study is to research the relationship with disrupted SI and function of central nervous system during motor performance using functional MRI. Patients & methods Seven healthy subjects (mean ages 34.7 ± 9.1 years, all men) and seven patients with writer cramp (mean ages 53.7 ± 17 years, 4 men and 2 women) were enrolled. Surrounding inhibition study: the experiment of surround inhibition was done according to Beck and Hallett. The EMG were recorded in both right first dorsal interosseus muscle (FDI) and abductor polices brevis muscle (APB). SI was evaluated as the ratio of MEP size of APB to that of FDI. Their right hand put on a side-table with their index finger on small tip of force transducer. Subjects pushed down on a small force transducer using their index finger as quickly as possible after an acoustic start signal. MEPs were measured by using single TMS which was given before signal and 100 ms, 150 ms and 1200 ms after signal. The time course of SI was constructed. And also cortical silent periods were measured for the evaluation of cortical inhibition during finger movement. Functional magnetic imaging for task and testing procedures: Subject was required to tap the second finger with the thumb at the speed of about 1 Hz for ten seconds of one session. Each subject participated in two sessions during they performed right-hand tapping or left-hand tapping. Functional MRI contrast analysis of activity was collected during tapping versus rest block. Blood oxygen level-dependent (BOLD) images were recorded. All imaging data were analyzed using analysis of SPM2 software in. Activation area was imaged by statistically activation of BOLD. For functional MRI, epoch-related fMRI design to map regional changes in BOLD signal under the condition of grip task and finger tapping task. Results In normal subjects, significant SI (smaller MEP of APB to FDI) was found within 150 ms after finger tapping. However, FHD showed no SI during finger tapping. In FHD, BOLD activity of contralateral SMA and cerebellum and excessive activation in PMA were observed in four of 7 patients. Hyperactive area around SMA in FHD extended broader than normal subjects. And also hyperactive areas were observed in ipsilateral SMA. Finger tapping task than grip task produced stronger activation in cerebellum and SMA in FHD. Discussion: In normal subjects, significant SI was found within 150 ms during pinching task with 10% Fmax. However, FHD showed no SI during pinching task. In FHD, the finding of fMRI showed BOLD hyper-activation of SMA and excessive activation in PMA. And also hyperactivity is observed in both cerebellar hemispheres. Tapping task than grip task produced hyperactivity in SMA and cerebellum. These findings suggest that skilled task must make less surround inhibition in central nervous system network. The finding of hyperactive BOLD signal suggests that dis-inhibition of central nervous system network. There may be any relationship with a disrupted SI and hyper-activation of cerebellum in fMRI during voluntary movement. Conclusion Our findings showed FHD with disrupted SI had cerebellar hyper activation of cerebellum in fMRI during voluntary movement.

Writing Process Modeling and Identification for Heat-Assisted Magnetic Recording

Written-in signal quality for heat-assisted magnetic recording (HAMR) is dominated by the hot spot thermal profile on the media. The thermal profile is determined by the head and media design, the laser power, and the near-field transducer (NFT) tip to media spacing (NMS). NMS keeps changing during the writing process due to protrusions generated by the laser-related heat sources, on top of the usual head-to-media spacing change due to thermal fly-height control and writing current. In this paper, data pattern writing process is modeled as a dynamic system consisting of NFT protrusions of different time constants, energy transfer efficiency versus NMS, media heat transient process, and power-to-signal conversion function. The parameters of this model are identified by minimizing the differences between the model output and the measured read-back signal magnitude of an experimental data pattern written on an HAMR drive. The Gaussian-Newton method is used to find the parameters of the non-linear system. Using the identified parameters, our model is able to predict the written-in signal magnitude, given the writing conditions such as laser power, laser current overshoot, and various thermal actuator operating conditions.

Developing Algorithms to Improve Defect Extraction and Suppressing Undesired Heat Patterns in Sonic IR Images

Sonic IR imaging is an emerging NDE technology. This technology uses short pulses of ultrasonic excitation together with infrared imaging to detect defects in materials and structures. Sonic energy is coupled to the specimen under inspection by means of direct contact between the transducer tip and the specimen at some convenient point. This region which is normally in the field of view of the camera appears as intensity peak in the image which might be misinterpreted as defects or obscure the detection and/or extraction of the defect signals in the proximity of the contact region. Moreover, certain defects may have very small heat signature or being buried in noise. In this paper, we present algorithms to improve defect extraction and suppression of undesired heat patterns in sonic IR images. Two approaches are presented, each fits to a specific category of sonic IR images.

Hyperthermia and malfunction of transesophageal echocardiographic probe.

Sir, Saluja et al. encountered transesophageal echocardiography (TEE) probe malfunction in a patient who developed fever.[1] The TEE probe stopped functioning when the TEE monitor showed a temperature of 42.5°C. TEE transducers have piezoelectric materials in which energy dissipation or energy losses are one of the most critical issues. If a piezoelectric element is heated to its Curie point, the domains become disordered and the element becomes completely depolarized. A piezoelectric element can therefore function for a long period without marked depolarization only at a temperature well below the Curie point.[2,3] A safe operating temperature would normally be halfway between 0°C and the Curie point. That is the reason for which heat sterilization of the probes should never be used because high temperature depolarizes piezoelectric crystals inside the probe and transducer loses its piezoelectric properties forever. Being in a high-volume cardiothoracic unit, we use TEE routinely as a real-time monitoring system in all the patients in operating room as well as in intensive care unit. The TEE transducer system has two levels of upper thermal limit: The first high limit is set at 41.0°C and the second high limit is set at 42.5°C. If the temperature of the transducer tip reaches 41.1°C, the temperature display turns reverse highlight and a warning appears (auto cool eminent) on a frozen images. This warning only appears once per examination. If the temperature reaches 42.5°C, the system freezes unconditionally. The user will not be allowed to scan until the temperature has decreased below 42.0°C. To restart scanning, the user must press the freeze key. The system has a lower thermal limit of 17.5°C. If the temperature of the transducer tip reaches 17.5°C, the temperature display turns reverse highlight and the system freeze unconditionally. The user will not be allowed to scan until the temperature has increased above 18°C. To restart scanning, the user must press the freeze key. The general guidelines for reducing the temperature in two-dimensional (2D) Doppler modes are as follows: Increasing image depth reduces the transducer surface temperature When imaging in color mode, there are no imaging changes that can reduce the transducer surface temperature When imaging in pulsed wave Doppler, decreasing pulse-repetition frequency and/or positioning the Doppler sample gate to a shallower depth generally reduces the surface temperature When imaging in continuous Doppler mode (CWD), increasing the depth of the CWD sample line (2D image depth before turning on Doppler trace mode) generally reduces the transducer surface temperature In any imaging mode, freezing the image will temporarily reduce the transducer surface temperature. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

317 Trial of Ultrasound-Guided Femoral Nerve Block for Isolated Femur Fractures Using Echogenic Needles

317 Trial of Ultrasound-Guided Femoral Nerve Block for Isolated Femur Fractures Using Echogenic Needles

4–5 Tb/in$^{{{2}}}$ Heat-Assisted Magnetic Recording by Short-Pulse Laser Heating

Due to poor thermal performance of media, it is difficult for heat-assisted magnetic recording (HAMR) to achieve densities greater than 3 Tb/in $^{ { {2}}}$ for continuous-wave laser heating. Short-pulse laser heating is an attractive approach to improve the thermal response of media. In this paper, the recording performances of HAMR using short-pulse laser heating are studied by dynamic micromagnetic simulations solving the Landau–Lifshitz–Bloch equation. The results show that the magnetic damping constant of the media, $\alpha $ , and applied magnetic field, $H$ , exhibit significant effects on recording quality at a pulse-width of 100 ps. From analyses of the relationships among readout signal and noise ratio, recorded track width, $\alpha $ , and $H$ , the required parameter setting for various recording densities are obtained. It is indicated that with a transducer tip size of 15 nm and heating laser pulse-width of 100 ps, a recording density greater than 4 Tb/in $^{2}$ is achievable for FePt recording media.

Analysis of Heat-Assisted Magnetic Recording to Density of 4 Tb/in<inline-formula> <tex-math notation="LaTeX">$^{\textbf {2}}$ </tex-math></inline-formula>

Thermal performance of media is a key factor limiting heat-assisted magnetic recording density. In this paper, the effects of near-field optical transducer tip size on the thermal profiles of media are studied, and the results show that even with a tip size of 10 nm, the obtained cross-track thermal spot size and down-track thermal gradient still cannot meet the requirements of 4 Tb/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for continuous-wave laser heating. Pulse laser heating can improve the thermal distribution significantly, and the requirements for 4 Tb/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> can be met at a pulsewidth of 100 ps. Dynamic micromagnetic recording simulation with Landau-Lifshitz-Bloch equation is conducted for pulse laser heating recording. The results indicate that 4 Tb/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> density is realizable for FePt recording media. It is also pointed out that, for short-pulse laser heating recording, media with large magnetic damping constant is important.

Implementation of a rotational ultrasound biomicroscopy system equipped with a high-frequency angled needle transducer--ex vivo ultrasound imaging of porcine ocular posterior tissues.

The mechanical scanning of a single element transducer has been mostly utilized for high-frequency ultrasound imaging. However, it requires space for the mechanical motion of the transducer. In this paper, a rotational scanning ultrasound biomicroscopy (UBM) system equipped with a high-frequency angled needle transducer is designed and implemented in order to minimize the space required. It was applied to ex vivo ultrasound imaging of porcine posterior ocular tissues through a minimal incision hole of 1 mm in diameter. The retina and sclera for the one eye were visualized in the relative rotating angle range of 270° ∼ 330° and at a distance range of 6 ∼ 7 mm, whereas the tissues of the other eye were observed in relative angle range of 160° ∼ 220° and at a distance range of 7.5 ∼ 9 mm. The layer between retina and sclera seemed to be bent because the distance between the transducer tip and the layer was varied while the transducer was rotated. Certin features of the rotation system such as the optimal scanning angle, step angle and data length need to be improved for ensure higher accuracy and precision. Moreover, the focal length should be considered for the image quality. This implementation represents the first report of a rotational scanning UBM system.

Microanatomic Analysis of the Round Window Membrane by White Light Interferometry and Microcomputed Tomography for Mechanical Amplification

The round window membrane (RWM) is increasingly becoming a target for amplification using active middle ear implants. However, the current strategy of using available transducer tips may have negative consequences for the RWM. We investigated the microanatomy of the RWM to establish a basis for the design of the transducer tip for the RWM driver. Using the guinea pig as an animal model, microcomputed tomography (μCT) and white light interferometry were used to study the topography of the RWM and RW niche (RWN). The curvatures of the RWM surface were calculated using the topography data. The 3-dimensional structure of the scala tympani terminal, saddle-shaped surface topography, and surface curvature were determined. The size of the scala terminal was approximated as an ellipse for which the major and minor axes were 1.29 and 0.95 mm. The average minimum and maximum radii of curvature around the center of RWM were -0.44 and +0.70 mm along the minor and major axis. The microanatomies of the RWM and RWN have important implications for the design of the transducer tip to maximize energy transfer while minimizing its distortion and permanent disruption. Our results suggest that the size of the transducer tip should be smaller than the minor axis of the scala terminal to avoid collision with the RWN. The driver should be designed to conform to the topography and radius of curvature of the center portion of the RWM, which for a guinea pig is 0.44 mm.

Oxygen influence on ultrasonic Doppler velocimetry of lead–lithium flow using titanium transducer

Ultrasonic Doppler velocimetry (UDV) with a titanium-tipped transducer has been successfully demonstrated for measuring a velocity profile of molten lead–lithium eutectic alloy (PbLi) with a concentration of oxygen and moisture lower than 1ppm. In contrast, it is found that UDV does not work for PbLi flows in a more oxygen-rich environment. This paper presents UDV measurements of PbLi flows at different levels of ambient oxygen concentration, and then discusses the measurement deterioration, based on a thermodynamic consideration of oxides formation in molten PbLi. In summary, it can be concluded that in an oxygen-rich environment, titanium oxidation occurs and consequently deteriorates the acoustic coupling between the transducer tip and the molten PbLi.