Transducer Housing Research Articles

Miniaturized preamplifier integration in ultrasound transducer design for enhanced photoacoustic imaging.

Photoacoustic imaging (PAI) utilizes the photoacoustic effect to record both vascular and functional characteristics of a biological tissue. Photoacoustic signals have typically low amplitude that cannot be read efficiently by data acquisition systems. This necessitates the use of one or more amplifiers. These amplifiers are somewhat bulky (e.g., the ZFL-500LN+, Mini-Circuits, USA, or 351A-3-50-NI, Analog Modules Inc., USA). Here, we describe the fabrication and development process of a transducer with a built-in low-noise preamplifier that is encased within the transducer housing. This new, to the best of our knowledge, design could be advantageous for applications where a compact transducer + preamplifier is required. We demonstrate the performance of this compact detection unit in a laser scanning photoacoustic microscopy system by imaging a rat ear ex vivo and a rat brain vasculature in vivo.

Towards a locally constructed multi-element ultrasound imaging transducer for resource poor environments

This paper investigates techniques and materials for making a multi-element ultrasound imaging transducer with craft-based techniques available in resource poor environments. The transducer housing can be conveniently divided into three parts: the body supporting the piezoelectric (PZT) elements and other components; the matching layer between the PZT elements and the human body; and the backing layer behind the PZT elements. Low-cost 3D printing systems based on photopolymers were found to be suitable for manufacturing the body. Finite Element Modelling (FEM) showed that the material characteristics of the backing layer and the thickness of the matching layer were much less critical than predicted by ultrasound plane wave theory and transmission line theory, respectively. The backing and matching layers are normally made from epoxy-tungsten composites that are pourable in the uncured state. However, the composite required for the backing layer was putty-like when uncured. When the tungsten was allowed to settle under gravity during curing, a 20 % by volume uncured tungsten-epoxy composite gave a 30 % by volume concentration of tungsten at the bottom when cured at 20–30 °C. These findings, when coupled with the findings from the FEM modelling, suggests that constructing a multi-element ultrasound imaging transducer using craft-based techniques is feasible.

#3379 DESIGN OF A NEW DIAPHRAGM PRESSURE TRANSDUCER FOR DIALYSIS MACHINE

Abstract Background and Aims Diaphragm pressure transducers can cause the dialysis process to be performed at higher quality. Pressure transduction is committed to concave, disc-shaped, impervious membranes that divide the respective chambers into two hermetically separate compartments: one contains liquid (blood/dialysate) while in the other there is trapped air. One of the sensitive parts in the design of a dialysis machine is diaphragm transducer which is used as a pressure gauge. One side of the diaphragm is pressurized, elastically deforming the diaphragm into a slightly curved shape and piezoelectric electrodes built a weak electrical signal that is used for measuring the pressure. The proper design of the diaphragm makes it sensitive to pressure changes and as a result, the pressure can be measured with high accuracy. Simulation of the flow inside the transducer can be used as a tool for designing the diaphragm and its housing. Method The behavior of whole blood is non-Newtonian. Under high shear forces, viscosity approaches an asymptotic value that corresponds to blood viscosity when considered as a Newtonian fluid. The Carreau-Yasuda model is used to express the relationship between shear stress and shear strain. Three modified and three novel geometries are suggested for pressure transducers. Each geometry is discretized with meshing software. Pyramidal cells are used to mesh the computing domain. Ansys Fluent software is an analyzer program that is used to simulate the field of fluid flow, heat transfer, etc. The solution is selected based on pressure. Due to the complexity of the geometry and convergence of the problem, only implicit formulation has been used for the model. The flow is assumed to be steady. The governing equation in this problem is continuity and momentum conservation and the k-ε model has been selected as for turbulent flow. Simple algorithm is considered for solving. Results The main output data is pressure distribution. Pressure and velocity distribution are related to each other. Figure 1 shows the velocity vector distribution in three modified schemes. The flow does not affect the pressure distribution inside the transducer housing for the straight port and is partially impressed in the shows-center port. The results of Figure 1 show that port location modification cannot affect the flow inside of the housing in such a way as to increase the sensitivity of the diaphragm. So, it was decided to redesign the geometry of the transducer's housing so can to apply the pressure variation on the diaphragm more sensibly. A curved part is added to the lower face of the transducer to guide the flow toward the diaphragm and distributed on the entire surface of the diaphragm to reach a uniform pressure. To find the best port location three configuration is used; i.e. straight, 90-degree, and 120-degree. Figure 2 is the velocity vector distribution for the other three novel geometries. In these schemes, flow circulates in the housing and has an effect directly on the diaphragm. The 90-degree port of the newly designed transducer has not had proper performance and pressure is concentrated on one side of the diaphragm which is between the ports. The uniformity of pressure becomes higher in the 120-degree. But in the straight scheme, the concentration is located exactly in the middle of the diaphragm and it is a desirable and optimal condition that the designer is seeking. Conclusion A series of simulations are carried out in the Ansys Fluent software to investigate a diaphragm pressure transducer flow after port locations and housing geometry modifications. The results show that if the fluid is directed to the diaphragm tangentially, the concentration of pressure is located on the diaphragm while the uniformity is reserved. The results show that this consideration leads to an optimal design using a new housing geometry with a curved shape wall to deflect the flow and distributed the pressure uniformly.

Treatment Depth Effects of Combined Magnetic Field Technology using a Commercial Bone Growth Stimulator

Lumbar spinal fusion is one of the more common spinal surgeries, and its use is on the rise. If the bone fails to fuse properly, then a pseudarthrosis or “false joint” develops and results in pain, instability, and disability. Since1974, three types of electrical stimulation technologies have been approved for clinical use to enhance spinal fusions. One such technology is inductive coupling, which includes combined magnetic fields (CMFs). The purpose of this study was to evaluate the effects of a CMF device known as the Donjoy (SpinaLogic®) on MG-63 (ATCC® CRL1427TM) human osteosarcoma cells at treatment depths ranging from 0.5” to 6.0”. The cells were grown to confluence on 4-well chamber slides that were kept in a nickel-alloy chamber within an incubator to shield the cells from unwanted environmental electromagnetic fields. During treatment, a specially designed apparatus held both the treatment device and the chamber slide. Briefly, the chamber slide was placed inside an acrylic tube at a specific distance from the transducer housing, and the device was turned on for 30 minutes. The chamber slides were then returned to the incubator to be evaluated at 7, 14, and 21 days post treatment for cell viability and bone nodule formation. Our results showed that compared to control cells, the cells located at 3” from the source had the greatest increase in bone nodule formation 7 days post treatment which is the depth at this consistent with manufacturer recommendations.

Low intensity pulsed ultrasound (LIPUS) for the treatment of intervertebral disc degeneration.

Discogenic back pain presents a major public health issue, with current therapeutic interventions limited to short-term symptom relief without providing regenerative remedies for diseased intervertebral discs (IVD). Many of these interventions are invasive and can diminish the biomechanical integrity of the IVDs. Low intensity pulsed ultrasound (LIPUS) is a potential treatment option that is both non-invasive and regenerative. LIPUS has been shown to be a clinically effective method for the enhancement of wound and fracture healing. Recent in vitro studies have shown that LIPUS stimulation induces an upregulation functional matrix proteins and downregulation of inflammatory factors in cultured IVD cells. However, we do not know the effects of LIPUS on an in vivo model for intervertebral disc degeneration. The objective of this study was to show technical feasibility of building a LIPUS system that can target the rat tail IVD and apply this setup to a model for acute IVD degeneration. A LIPUS exposimetry system was built using a 1.0 MHz planar transducer and custom housing. Ex vivo intensity measurements demonstrated LIPUS delivery to the center of the rat tail IVD. Using an established stab-incision model for disc degeneration, LIPUS was applied for 20 minutes daily for five days. For rats that displayed a significant injury response, LIPUS treatment caused significant upregulation of Collagen II and downregulation of Tumor Necrosis Factor - α gene expression. Our preliminary studies indicate technical feasibility of targeted delivery of ultrasound to a rat tail IVD for studies of LIPUS biological effects.

Focal point determination in magnetic resonance-guided focused ultrasound using tracking coils

To develop a method for rapid prediction of the geometric focus location in MR coordinates of a focused ultrasound (US) transducer with arbitrary position and orientation without sonicating. Three small tracker coil circuits were designed, constructed, attached to the transducer housing of a breast-specific MR-guided focused US (MRgFUS) system with 5 degrees of freedom, and connected to receiver channel inputs of an MRI scanner. A one-dimensional sequence applied in three orthogonal directions determined the position of each tracker, which was then corrected for gradient nonlinearity. In a calibration step, low-level heating located the US focus in one transducer position orientation where the tracker positions were also known. Subsequent US focus locations were determined from the isometric transformation of the trackers. The accuracy of this method was verified by comparing the tracking coil predictions to thermal center of mass calculated using MR thermometry data acquired at 16 different transducer positions for MRgFUS sonications in a homogeneous gelatin phantom. The tracker coil predicted focus was an average distance of 2.1 ± 1.1 mm from the thermal center of mass. The one-dimensional locator sequence and prediction calculations took less than 1 s to perform. This technique accurately predicts the geometric focus for a transducer with arbitrary position and orientation without sonicating. Magn Reson Med 77:2424-2430, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Development of a spherically focused phased array transducer for ultrasonic image-guided hyperthermia

A 1.5 MHz prolate spheroidal therapeutic array with 128 circular elements was designed to accommodate standard imaging arrays for ultrasonic image-guided hyperthermia. The implementation of this dual-array system integrates real-time therapeutic and imaging functions with a single ultrasound system (Vantage 256, Verasonics). To facilitate applications involving small animal imaging and therapy the array was designed to have a beam depth of field smaller than 3.5 mm and to electronically steer over distances greater than 1 cm in both the axial and lateral directions. In order to achieve the required f number of 0.69, 1-3 piezocomposite modules were mated within the transducer housing. The performance of the prototype array was experimentally evaluated with excellent agreement with numerical simulation. A focal volume (2.70 mm (axial) × 0.65 mm (transverse) × 0.35 mm (transverse)) defined by the −6 dB focal intensity was obtained to address the dimensions needed for small animal therapy. An electronic beam steering range defined by the −3 dB focal peak intensity (17 mm (axial) × 14 mm (transverse) × 12 mm (transverse)) and −8 dB lateral grating lobes (24 mm (axial) × 18 mm (transverse) × 16 mm (transverse)) was achieved. The combined testing of imaging and therapeutic functions confirmed well-controlled local heating generation and imaging in a tissue mimicking phantom. This dual-array implementation offers a practical means to achieve hyperthermia and ablation in small animal models and can be incorporated within protocols for ultrasound-mediated drug delivery.

Vibro-acoustic model of a piezoelectric-based stethoscope for chest sound measurements

This article focuses on the influence of noise and vibration on chest sound measurements with a piezoelectric stethoscope. Two types of vibrations, namely inputs through the patient chest and disturbances from the physician, influence the acoustic measurement. The goal of this work is to develop a model to understand the propagation of these vibrational noises through the stethoscope and to the piezoelectric sensing element. Using the model, methods to reduce the influence of disturbances acting on the stethoscope from the physician handling the device are explored.A multi-DOF rigid body vibration model consisting of discrete connected components is developed for the piezoelectric stethoscope. Using a two-port lumped parameter model, the mechanical vibrations are related to the resulting electrical signal. The parameterized state space model is experimentally validated and its parameters are identified by using a thorax simulator and vibration shaker. Based on predictions from the model, the introduction of vibration isolation to reduce the influence of physician noise on the transducer is then pursued. It is shown that direct vibration isolation between the transducer and the rest of the stethoscope structure leads to a reduction in coupling with the patient’s chest. However, if isolation is instead introduced between the transducer housing and the rest of the stethoscope, then vibration isolation from the physician is achieved with far less reduction in patient coupling. Experimental results are presented to study the influence of the proposed design changes and confirm the predicted model behavior.

3D ultrasound system to investigate intraventricular hemorrhage in preterm neonates

Intraventricular hemorrhage (IVH) is a common disorder among preterm neonates that is routinely diagnosed and monitored by 2D cranial ultrasound (US). The cerebral ventricles of patients with IVH often have a period of ventricular dilation (ventriculomegaly). This initial increase in ventricle size can either spontaneously resolve, which often shows clinically as a period of stabilization in ventricle size and eventual decline back towards a more normal size, or progressive ventricular dilation that does not stabilize and which may require interventional therapy to reduce symptoms relating to increased intracranial pressure. To improve the characterization of ventricle dilation, we developed a 3D US imaging system that can be used with a conventional clinical US scanner to image the ventricular system of preterm neonates at risk of ventriculomegaly. A motorized transducer housing was designed specifically for hand-held use inside an incubator using a transducer commonly used for cranial 2D US scans. This system was validated using geometric phantoms, US/MRI compatible ventricle volume phantoms, and patient images to determine 3D reconstruction accuracy and inter- and intra-observer volume estimation variability. 3D US geometric reconstruction was found to be accurate with an error of <0.2%. Measured volumes of a US/MRI compatible ventricle-like phantom were within 5% of gold standard water displacement measurements. Intra-class correlation for the three observers was 0.97, showing very high agreement between observers. The coefficient of variation was between 1.8–6.3% for repeated segmentations of the same patient. The minimum detectable difference was calculated to be 0.63 cm3 for a single observer. Results from ANOVA for three observers segmenting three patients of IVH grade II did not show any significant differences (p > 0.05) for the measured ventricle volumes between observers. This 3D US system can reliably produce 3D US images of the neonatal ventricular system. There is the potential to use this system to monitor the progression of ventriculomegaly over time in patients with IVH.

Proposal of Curvature Control Method for High Intensity Focused Ultrasound Transducer

A method of controlling the focal length of concave ultrasonic transducers using a flexible surface with arrayed piezoelectric elements is proposed. The surface made of a silicon rubber has a different curvature depending on the air pressure of the inner space of the transducer housing. The acoustic fields of the transducer were measured and compared with the simulated ones. The ultrasonic field from the transducer converged with a different shape with the deflection of the surface. We confirmed the possibility that the focal point of the transducer could be easily controlled by the method.

I08 System for measuring tongue force variability immune to head movements artifacts

System originally developed for Track-HD project (R Reilmann) due to externally opened force measuring chain, can be vulnerable to upper body and head movements, which may interfere with measured tongue force. The sensor housing is attached to the external frame against which subject suppose to rest during the measurement. The tongue pushing muscles (four extrinsic glossus muscles) are anchored in the bottom part of oral cavity. The housing of the force transducer should be attached to the same biomechanical structure which serves muscles anchoring. The most steady fixation surface provides the bite that allow comfortable holding of transducer between the teeth. Transducer housing has cylindrical form of 13 mm diameter with the butterfly plate at its top, preventing its slippage out of the mouth (a modified syringe). The opposite slotted tip of the syringe, serves as the bayonet connection, allowing to attach the force sensor in precisely centered position. Pushing force of the tongue, which always stays inside the mouth, is transmitted to the force sensor by the syringe plunger with removed sealed tip. To prevent the damage of the force sensor by applying the force above 45N, there is a short spring giving the transducer additional elasticity which passes to the excessive force to the sensor enclosure. Authors explored the possibility of characterising the tongue force instability with the single number parameter like the surface under the rectified AC force signal, as well as the number of crossings the line of required force level. Force transducer may be connected to the universal data acquisition system originally developed for measuring saccadic eye movements.

Flexible Ultrasound Transducer Array

A transducer array includes two or more sub-arrays that move relative to each other. Position sensors on each of the sub-arrays provide spatial coordination for beamforming and/or image forming to yield extended field of view and high image resolution. The adaptable transducer array, such as mounted on a flexible transducer housing, allows the array to better conform to the patient during internal or external use.

‘Ceci n’est pas une échographie': a plea for quality assessment in prenatal ultrasound

‘Ceci n’est pas une échographie': a plea for quality assessment in prenatal ultrasound

Transducer to actuator interface

An implantable hearing aid transducer including a transducer housing, a driver, and an actuator movably connected to the transducer housing. The transducer driver includes at least one coil and one magnet. In one aspect of the present transducer, a seal is provided to seal transducer components that are located at a location other than at the movable connection between the actuator and the transducer housing. According to this aspect, the seal may be disposed around one of a magnet and a coil that is connectable to the actuator, to protect the same from body fluids. The other one of the magnet and the coil may include its own seal within the transducer housing.

Connector for securing ultrasound catheter to transducer

An ultrasound system has an ultrasound transducer having a transducer housing and a horn provided at the distal end of the transducer housing, an ultrasound transmission member, a sonic connector that is connected to the horn and the proximal end of the ultrasound transmission member, and a catheter knob having a proximal end that is coupled to the distal end of the transducer housing. The catheter knob has a proximal bore that houses the sonic connector. The system also includes a nesting piece that is retained inside the proximal bore of the catheter knob. The nesting piece can be moved from a first position where the sonic connector is received inside the nesting piece to a second position where the sonic connector is separated from the nesting piece when ultrasound energy is being propagated through the ultrasound transmission member.

Implantable transducer for hearing aids and process for tuning the frequency response of one such transducer

An implantable electromagnetic transducer for hearing aids and process for tuning its frequency response are disclosed. The transducer is provided with a static transducer part which includes a hermetically sealed transducer housing and a ring coil arrangement which is mounted inside, and with a dynamic part which is mechanically connected to the static transducer part via at least one connecting element which is coupled in the implanted state to part of the body of the implant wearer via at least one connecting element. The implantable transducer has a permanent magnet arrangement, which interacts with the ring coil arrangement and which is supported to be able to vibrate by means of a support in the direction of the axis of the ring coil arrangement, with at least one connecting element being made as a multifunction element which is part of the support and/or part of the hermetically tight transducer housing. The mechanical properties of the multifunction element are selected for achieving a set frequency response of the transducer.

Electric/acoustic transducer module, in-ear hearing aid and method for manufacturing an in-ear hearing aid

A transducer module for integration into a hearing aid device. The transducer module has an encapsulation with an opening and a transducer housing resiliently mounted in the encapsulation. The transducer module also has a first membrane and a second membrane. The first membrane forms a first space adjacent to a first side of the membrane which communicates with the opening. The first membrane also forms a second space adjacent to a second side of the first membrane which communicates with an intermediate space between the transducer housing and the encapsulation. The second membrane is for closing the opening of the encapsulation. Further, the transducer forms a self-contained module with the encapsulation as a housing of the module, with the module being adapted for insertion into the hearing device.

Application of computational fluid dynamics and laser Doppler velocimetry to liquid ultrasonic flow meter design

Axisymmetric computational fluid dynamic (CFD) studies have been undertaken for the case of a coaxial, ultrasonic transducer housing in a cylindrical cross-section metering duct and compared to experimental results taken by laser Doppler velocimetry. Results are presented for a meter geometry having a single strut attachment of the transducer housing to the duct wall at Reynolds numbers (based on mean velocity and meter duct diameter) of 750, 3000 and 8000. Good matches between experiment and CFD modelling have been obtained near the duct walls, with some significant departures near the duct centreline, attributed to the limitations of modelling a 3D flow using an axisymmetric model. This CFD modelling is being used to improve the design of similar flow meters.

Remotely controlled beeper and method

A collar-mounted animal training device includes a piezoelectric transducer device ( 6 ) attached to a mylar cone acoustic element mounted in a transducer housing ( 5 ) configured as a resonant sound port. The piezoelectric transducer is driven by circuitry including a microcontroller ( 31 ), a voltage booster circuit ( 34 ), and driver circuitry coupled to the booster circuit and producing a boosted drive signal to the piezoelectric device ( 6 ). The microcontroller stores data representing a plurality of sequential segments each having a start and stop time and a start and stop frequency. The microcontroller sequentially produces a plurality of output signals having a start and stop times and frequencies.

Miniature high frequency focused ultrasonic transducers for minimally invasive imaging procedures

Abstract Spherically focused, high frequency (30–50 MHz) ultrasonic imaging transducers are fabricated using poly(vinylidene) difluoride (PVDF) film and a membrane deflection technique that is compatible with CMOS microelectronics fabrication. Micromachined ultrasonic transducers with 0.75–2.00 mm-diameter apertures and f-numbers of 1.30–2.45 are fabricated and characterized. The transducers exhibit focused radiation patterns with 50 μm axial resolution and 51–92 μm lateral resolution and bandwidths of 80–110% around center frequency values. A miniature preamplifier hybrid circuit, which is designed to be mounted within the transducer housing, is fabricated and characterized to reveal a low noise level of 5.3 nV / H z . Tissue imaging capabilities of the micromachined ultrasonic transducers are demonstrated through successful imaging of human cadaveric aorta.