Array Of Transducer Elements Research Articles

Ultrasound drug delivery enhancement and imaging systems and methods

A method and system for both enhancing drug uptake by application of therapeutic transmissions of acoustic energy and imaging a region for applied therapy with a same transducer and ultrasound system. An ultrasonic image of a field of view is generated while localized delivery of a drug is enhanced with ultrasound energy. Using the same transducer and ultrasound system reduces costs and increases system availability for a broader range of medical practitioners. For example, a single linear array of transducer elements is used for application of both imaging and therapeutic ultrasound. As another example, a transmitter is provided that transmits therapeutic transmissions having substantially equal positive and negative peaks at the face of the transducer and also is operable to transmit imaging acoustic energy. As yet another example, therapeutic pulses of acoustic energy are transmitted to have greater power for heating than imaging, but a mechanical index or pressure comparable to imaging transmissions. For example, a mechanical index of about 1.9 or lower is provided, such that cavitation of blood or other non-contrast agent is avoided.

Apparatus and system for real-time synthetic focus ultrasonic imaging

An apparatus for use in an ultrasonic imaging system adapted for generating synthetic focus images in real-time. The apparatus employs an integrated circuit architecture which is scalable and can be employed to construct real-time synthetic focus ultrasonic imaging systems having a large number of transducer array elements. The apparatus utilizes one field programmable gate array per image channel for data storage and sub-image generation. Each field programmable gate array includes on-chip block memories to store digitized ultrasonic signal return echo data and at least one block memory used to store data associated with each ultrasonic transmitter-receiver array pair. Logic inside the field programmable gate array calculates memory addresses during image generation to generate a time-of-flight surface and to form sub-images.

Systems and methods for reducing secondary hot spots in a phased array focused ultrasound system

Systems and methods for performing a therapeutic procedure using focused ultrasound include providing a piezoelectric transducer including a plurality of transducer elements (22), such as a concave concentric ring array or a linear array of transducer elements. Drive circuitry (14) is coupled to the transducer for providing drive signals to the transducer elements at one of a plurality of discrete RF frequencies. A controller (16) is coupled to the drive circuitry for periodically changing a frequency of the drive signals to one of the plurality of discrete frequencies, while controlling a phase component of the drive signals to maintain the focus of the transducer at a primary focal zone during a single sonication.

Ultrasound probe having transducer elements with different frequency centers

Described herein is an ultrasound probe for ultrasound imaging using contrast enhancing agents and including two interleaved arrays of transducer elements. Each array has a longitudinal dimension along which transducer elements are placed. One interleaved array includes transducer elements having a lower center frequency. Another interleaved array includes transducer elements having a higher center frequency. The transducer elements are provided on inter-fitting support members. A length of the transducer elements of one array is larger than a corresponding length of the transducer elements of the other array.

Numerical technique to reduce cross-coupling in acoustical arrays

Applicability of finite element method to optimize the far-field directivity pattern of an individual element in a piezoelectric transducer array is reported. The FEM algorithm calculates the electrical potentials needed to be applied to the two elements which are immediate neighbours to the element being activated in order to minimize acoustic cross-coupling. The feasibility of the algorithm was successfully tested using a simple five elements array made of conventional PZT-5H piezoelectric ceramic material.

Review of Modal Sensing and Actuation Techniques

The linear behavior of continuous structures is characterized by the combined response of infinite individual modal responses. Knowledge of the contribution of each individual mode to the overall dynamic response simplifies many applications, such as vibration control, shape estimation, and structural health monitoring. Unfortunately, most transducers simultaneously measure a combination of modes, and hence extracting the contribution of an individual mode can be difficult. The concept of modal transducers was developed in the late 1970s to overcome this limitation and allow for the simplified design of active control laws. Modal transducers seek to address individual vibration modes on a structure through the intelligent design of transducers, reducing the apparent system complexity. These modal transducers, also known as modal sensors and modal actuators, greatly simplify the problems of vibration control and shape estimation. This paper reviews the literature concerning the design and implementation of spatial modal sensors and actuators. Construction techniques initially focused on large-area sensors physically shaped to provide the desired spatial coupling. Modern techniques use arrays of transducer elements that have their signals weighted to provide the desired filtering. While temporal modal sensors exist, their use in real-time vibration control, shape estimation, and health monitoring is limited due to large time lags resulting from the temporal filtering. This critical review aims to illuminate the main characteristics, advantages, and limitations of the different techniques and provides an extensive list of references on the subject.

Simulation and experimental characterization of a 2-D capacitive micromachined ultrasonic transducer array element

In this letter, a 400-mumx400-mum 2-D capacitive micromachined ultrasonic transducer (cMUT) array element is experimentally characterised, and the results are found to be in good agreement with theoretical predictions. As a receiver, the transducer has a 1.8x10(-7) nm/ radical(Hz) displacement sensitivity, and, as a transmitter, it produces 16.4 kPa/V of output pressure at the transducer surface at 3 MHz. The transducer also has more than 100% fractional bandwidth around 3 MHz, which makes it suitable for ultrasound imaging.

Transducer for sonic logging-while-drilling

An acoustic wave transducer useful in sonic logging while drilling a borehole includes an array of transducer elements mounted circumferentially around a drill collar. The elements are bonded in an elastomer ring that is received in an external groove in the collar and are protected by a shield having windows. The elements are electrically connected in parallel so that when excited by an electrical pulse, the elements generate a monopole acoustic wave that propagates out into the formation. When used as a receiver, the elements detect averaged acoustic waves from the formation around the circumference of the collar and have minimum sensitivity to multipole waves traveling through the drill collar.

Electrical interconnect for multilayer transducer elements of a two-dimensional transducer array

A multilayer two-dimensional array of ultrasonic transducer elements includes four via segments at the four corners of each transducer element. A first pair of diagonally opposed via segments provide signals to signal electrode layers of each transducer element. A second pair of diagonally opposed via segments interconnect ground electrode layers. Thus, a redundant interconnection scheme is achieved. If the transducer elements include piezoelectric layers having a square cross section parallel to a transducer radiating surface, four-fold symmetry is maintained, despite the formation of the four via segments. Also disclosed is a method of forming a two-dimensional array.

A new method for estimation of velocity vectors

The paper describes a new method for determining the velocity vector of a remotely sensed object using either sound or electromagnetic radiation. The movement of the object is determined from a field with spatial oscillations in both the axial direction of the transducer and in one or two directions transverse to the axial direction. By using a number of pulse emissions, the inter-pulse movement can be estimated and the velocity found from the estimated movement and the time between pulses. The method is based on the principle of using transverse spatial modulation for making the received signal influenced by transverse motion. Such a transverse modulation can be generated by using apodization on individual transducer array elements together with a special focusing scheme. A method for making such a field is presented along with a suitable two-dimensional velocity estimator. An implementation usable in medical ultrasound is described, and simulated results are presented. Simulation results for a flow of 1 m/s in a tube rotated in the image plane at specific angles (0, 15, 35, 55, 75, and 90 degrees) are made and characterized by the estimated mean value, estimated angle, and the standard deviation in the lateral and longitudinal direction. The average performance of the estimates for all angles is: mean velocity 0.99 m/s, longitudinal S.D. 0.015 m/s, and lateral S.D. 0.196 m/s. For flow parallel to the transducer the results are: mean velocity 0.95 m/s, angle 0.10, longitudinal S.D. 0.020 m/s, and lateral S.D. 0.172 m/s.

Speckle reduction in ultrasound imaging

A system and a method for generating an ultrasound image of an interrogation region in an object with a transducer with a two-dimensional array of transducer elements, includes the steps of generating an ultrasound beam by activating many transducer elements of the two-dimensional array; electronically controlling the beam to illuminate substantially the same region from at least two orientations; capturing the echoes generated with the beam illuminating the object at different orientations; and analyzing the echoes from all directions to produce an image of the region of the object. The aperture of the transducer generating the beam is at least substantially equal to the aperture generated by a linear array of transducer elements extending across the substantially shortest distance between two opposite edges on the two-dimensional array. The ultrasound power emitted from the transducer elements is not spatially uniform, and the multiple echoes reduce speckle in the image.

Improved signal-to-noise ratio in hybrid 2-D arrays: experimental confirmation.

2-D array transducers have shown significant promise for medical ultrasound over conventional linear arrays, at the cost of increasing the number of channels, difficulty of fabrication and array element impedance. The increase in element impedance reduces the power coupled to a 2-D array element from a conventional 50 omega source in transmit mode. If the array is sparse, which is typical of 2-D arrays, then the net power coupled into the front acoustic load is reduced when compared to a fully sampled aperture. Furthermore, the received signal-to-noise ratio (SNR), when measured through a nonideal amplifier, is degraded because the high impedance 2-D array transducer element cannot efficiently drive the coaxial cable. The reduction in transmit sensitivity and received SNR can be circumvented with the application of multilayer piezoelectric elements. The improvement in transmit occurs because the transducer impedance is better matched to the impedance of the source. In receive, multilayer elements allow more of the open circuit received voltage to fall across the input of the high impedance preamplifier. In this case, the same number of layers are used in transmit and receive. Recently, it has been suggested that separate optimization of the transmit channel and receive channel (a hybrid array) would further improve the pulse-echo SNR. In this paper, we fabricated and tested a hybrid array operating at 1 MHz using a multilayer transmit element and single layer receive element. A 7 omega transmitter and high impedance preamplifier were placed adjacent to the transmit and receive elements within the transducer assembly. The hybrid pulse-echo SNR improved by 26.4 dB over the conventional array. The experimental result showed good agreement with the KLM model. Furthermore, KLM simulations showed that as the operating frequency of the array increases, the overall improvement over the conventional array increases. For example, a 1.5-D array operating at 2 M Hz had an improvement of 30 dB whereas a 7.5 M Hz 1.5-D array showed an increase of approximately 38 dB. The separate optimization of the transmit and receive channel for 2-D arrays showed even greater improvement than for 1.5-D arrays. For example, a 2 MHz 2-D array had an improvement of over 44 dB.

Ultrasound imaging based on multiple beamforming with coded excitation

Phased-array ultrasound imaging employing multiple receive beamforming with coded excitation is investigated. The approach is based on simultaneous excitation of transducer array elements with coded signals, and multiple receive beamforming. It involves only a single transmit-receive step for reconstruction of each image frame. The excitation signals are chosen as decorrelated binary pseudo-noise sequences. Performance of the coded excitation imaging is tested through simulations for code sequences with various lengths and different decoding filters. The simulation results show that the ultrasound scanner with the coded excitation can produce up to —15 dB side lobe level at the transmit beam profile with sufficiently long codes, whereas very short codes result in about —7 dB side lobe level. The coded excitation imaging improves the signal-to-noise ratio and minimizes the signal firings, and hence provides increased penetration depth and frame rates.

Delay generator for phased array ultrasound beamformer

A delay generator for a beamformer in a phased array ultrasound imaging system is provided. The beamformer processes received signals from an array of transducer elements to form a receive beam. The beamformer includes a delay generator corresponding to each transducer element for delaying the received signal. The delay generator includes a delay unit and a delay controller. The delay is variable in response to a change delay signal supplied by the delay controller at discrete times during reception of ultrasound energy. According to one feature of the invention, the delay represents an exact solution, within the quantization error of the delay unit, to the delay equation for the delay at a given steering angle, transducer element and focal depth. According to another feature of the invention, the delay controller generates a change delay signal that steers the receive beam to a dynamically variable steering angle and dynamically focuses the receive beam during reception of ultrasound energy.

Relation between total power output and input phase of underwater transducer array elements made of piezo‐rubber.

The mutual interaction of underwater acoustic transducer array elements is one of the most important factors for its transmission performance. The power output from each array element is characterized by mutual radiation impedance between array elements. Recently numerical simulations are often applied to solve this kind of problem. Generally PZT transducer array is used in experiments but mechanical Q of PZT transducer is high and the range of measuring frequency is limited in narrow band. So many sizes of transducer array models are required to evaluate in different frequencies. Composite material piezo‐rubber has unique properties. Its flexibility and broadband resonance character by low mechanical Q allow experiments in various frequencies utilizing one array apparatus. Consequently a flexible method of model experiment using piezo‐rubber sheet transducer array is introduced. The total power output versus input phase of 3 × 3 piezo‐rubber transducer array provides the effects of interaction between array elements in various frequencies and input amplitudes. Also near field 3‐D mapping of real power and imaginal power shows radiation performance of this transducer array visually. A clear power reduction was observed in the case of a −180‐deg phase shift pattern.

Reviews Of Acoustical Patents

Abstract

2-D array for phase aberration correction

A vibratory energy (ultrasonic) imaging system of the type including a transducer array having a plurality of transducer elements for generating pulses of vibratory energy which are directed towards reflectors and which receive reflections of said vibratory energy and develop echo signals in response thereto. The array comprises a two-dimensional array of transducer elements arranged in a plurality of rows extending in a lateral dimension of the array and a plurality of columns extending in an elevation dimension of the array, at least one of a first type of said columns having elements of a first height in the elevation dimension and at least one of a second type of column having elements of a second height in the elevation dimension which is greater than the first height. In a preferred embodiment of the invention, the first height is an integral fraction of the second height.

Ultrasonic imaging system and method with focusing correction

Ultrasonic imaging apparatus and method are shown which include electronic correction or focus defects produced by acoustic refractive index inhomogeneities within an object (14) being imaged. The region of interest (38) within which focus correction takes place is selected by the operator using control (42 or 84). The imaging system includes adjustable time delays (28-1 through 28-c) through which return signals from transducers (10-1 through 10-n) pass. Outputs from the delays are summed (30) and the resultant signal is envelope detected (32). The envelope detector output is prepared for display at display (36) by scan converter (34). The output from a focus correction delay control circuit (64) is used to control delay times of individual delays (28-1 through 28-c) to provide for a delay profile across operative elements of transducer array (10), which delay profile includes delay profile components that correspond to low order terms of a series expansion, such as a Fourier series (fig. 4). The adjustable signal delays (28-1 through 28-c) are simultaneously adjusted by the focus correction delay control (64) during selection of delay profile component amplitudes which reduce focus defects within the region of interest (38). Either manual (fig. 1) or automatic (fig. 5) focus correction is provided.

Phased array sonic transducers for marine instrument

A low cost phased array sonic transducer is described in which an array of transducer elements separated by spacers are held within a frame which applies a compressive force transverse the length of the elements.

Optoelectronic transmitters for medical ultrasound transducers

Optoelectronics and fiber optics can be used to miniaturize and improve the flexibility of the transducer cable and transducer handle of medical diagnostic ultrasound scanners. The reduction in size has gained importance as 2-D array transducers with up to 1000 independent channels become accepted to improve diagnostic ultrasound images. The authors describe the analysis, design, fabrication and testing of a prototype silicon photoconductive semiconductor switch (PCSS). The monolithic silicon PCSS was used in combination with an infrared semiconductor diode laser with a fiber optic "pigtail" to shock excite and burst excite a 2-D array transducer element resonant at 2.5 MHz. Optically controlled voltage, current, and ultrasound pulses are compared to those from conventional electronic shock excitation and narrow band Doppler pulses. The optically triggered ultrasound pulse for single shock excitation produced 30 V spikes at the 2-D array element with a fall time of 200 nsec and a rise time of 2 /spl mu/sec with a peak current through the transducer element of 34 mA. An optically produced burst of eight pulses at a frequency of 2.5 MHz produced 11 V spikes at the transducer with a fall time under 100 nsec and a rise time of approximately 300 nsec. The peak current per pulse was 25 mA through the transducer element. These results show the feasibility of applying optoelectronic technology to replace conventional electronic transmitter technology.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>