Journal articles: 'Phased-array ultrasound transducer'

1

Turnbull, Daniel H., and F. Stuart Foster. "Simulation of B-Scan Images from Two-Dimensional Transducer Arrays: Part Ii - Comparisons between Linear and Two-Dimensional Phased Arrays." Ultrasonic Imaging 14, no. 4 (1992): 344–53. http://dx.doi.org/10.1177/016173469201400402.

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Two-dimensional (2-D) arrays have been proposed as a solution to the degradation in medical ultrasound image quality occurring as a result of asymmetric focusing properties of linear phased array transducers. The 2-D phased transducer array is also capable of electronically steering the symmetrically focused ultrasound beam throughout a three-dimensional volume. In a companion paper the potential of 2-D transducer arrays for medical imaging has been investigated using simulated B-scan images. In this paper, the advantages of 2-D over linear transducer arrays is demonstrated by simulating images of spherical cysts embedded in a large scattering volume. The large elevation beamwidth in the nearfield of a 5 MHz linear phased transducer array results in a severe reduction in the image contrast measured between a 4 mm diameter cyst and the surrounding scattering media. By employing a 2-D array with symmetric focusing, the contrast between the cyst and surrounding scatterers is significantly improved. The use of additional elements in the elevation direction of a linear array is also investigated. In this case the additional elements are included only to focus, but not to steer the ultrasound beam. Using the contrast characteristics of a 4 mm diameter cyst, it is shown that relatively few elevation elements are required to significantly improve the nearfield imaging capability of the linear array.

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Gentry, Kenneth L., Nasheer Sachedina, and Stephen W. Smith. "Catheter Ultrasound Phased-Array Transducers for Thermal Ablation: A Feasibility Study." Ultrasonic Imaging 27, no. 2 (2005): 89–100. http://dx.doi.org/10.1177/016173460502700203.

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The feasibility of catheter single-element ultrasound transducers for cardiac ablation has been shown previously. We describe the design and testing of catheter-sized linear phased arrays transducers for ultrasound ablation. One array has 86 PZT-4 elements operating at 8 MHz and 5 MHz. The overall array size is 14.9 mm by 3.1 mm (10 Fr). The other array has 50 PZT-5 elements operating at 4 MHz and is 17 mm by 3.1 mm (10 Fr). In order to produce the intensity needed to create lesions in heart tissue, we modified a real-time, 3D scanner to produce 100 Vpp 256-cycle transmit pulses at a pulse repetition frequency of 14.1 kHz. This made it possible for the PZT-4 and PZT-5 transducers to produce ISPTA of 3.26 W/cm2 and 142 W/cm2, respectively. When driving the transducers at high duty factor, the transmit circuitry in the scanner was damaged. A mechanically-focused transducer with the same dimensions as the PZT-4 transducer was built. When transmitting continuously at 9 MHz, it produced an ISPTA of 29.3 W/cm2. This created a lesion 5 mm across and 5 mm deep in beef tissue while raising the focal temperature 23°C. Ablation is within the capabilities of a catheter phased array transducer integrated into a diagnostic ultrasound scanner.

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Wang, Hongliang, Jiao Qu, Xiangjun Wang, Changde He, and Chenyang Xue. "Investigation and Analysis of Ultrasound Imaging Based on Linear CMUT Array." International Journal of Pattern Recognition and Artificial Intelligence 33, no. 08 (2019): 1957004. http://dx.doi.org/10.1142/s0218001419570040.

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In the next generation of ultrasound imaging systems, Capacitive micromachined ultasonic transducer (CMUT) based on microelectromechanical systems (MEMS) is a promising research direction of transducers, which has wide application prospects. In this paper, based on the study of three imaging methods, including classical phased array (CPA) imaging, classical synthetic aperture (CSA) imaging and phased subarray (PSA) imaging, several different imaging schemes are designed for linear CMUT array, after that the performances of these imaging schemes are compared and analyzed. The effects of the three imaging methods are verified and analyzed based on the linear CMUT array. Through analysis, it is found that the image quality of the classical phased array imaging method is the best, the imaging quality of the above three imaging methods can be effectively improved by adopting the amplitude apodization and dynamic focusing method. The research results in this paper will provide theoretical basis and application reference for the design of ultrasonic imaging system based on linear CMUT array in the future.

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Ellingson, William A., J. Scott Steckenrider, and Thomas J. Meitzler. "Defect Detection in Ceramic Armor Using Phased Array Ultrasound." Advances in Science and Technology 65 (October 2010): 143–52. http://dx.doi.org/10.4028/www.scientific.net/ast.65.143.

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Monolithic ceramic tile is used as part of ceramic-composite armor. Rejection of individual tile that contain potential threat-defeat-reducing ―defects‖ must be accomplished in a fast and cost-effective manner. Water-immersion phased-array ultrasound using 10 MHz 128-element transducers sequenced at 32-elements has been demonstrated to quickly scan and detect 25-50 um known inclusion-type defects in individual 25 mm thick SiC tile. Further, use of similar phasedarray transducers and similar transducer-element activation sequences, has shown detection of intentional internal defects in tests of 40 cm square by 50 mm thick, multi-layered composite ceramic-armor specimens. Large changes in acoustic velocities of the various layered materials causes focusing issues of the ultrasonic wave. The use of various digital signal processing methods can be used to overcome some of these issues. The results show that use of phased array ultrasound can reliably be used for defect detection in either monolithic or composite ceramic-armor. The technology and various results are presented.

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Curley, Jonathan, Christian Renwick, and Venkat Mangunta. "Handheld Ultrasound Device Utilization in Extracorporeal Membrane Oxygenation Initiation." Journal of Cardiac Critical Care TSS 8 (October 24, 2024): 246–51. http://dx.doi.org/10.25259/jccc_41_2024.

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Ultrasound imaging is recommended to augment the initiation of extracorporeal membrane oxygenation (ECMO). Handheld ultrasound devices may serve as potential imaging tools, given the increasing image quality and ultrasound functionality in recent models. Specifically, dual transducer ultrasound devices that provide both a phased array and linear transducer on a single device may offer exceptional value to the intensivist or ECMO clinician. A description of the potential utility of incorporating dual transducer ultrasound devices into ECMO initiation and corresponding images depicting image quality and usage. The dual transducer ultrasound device may serve as a valuable clinical tool for the intensivist or ECMO clinician.

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Benkeser, P. J., L. A. Frizzell, K. B. Ocheltree, and C. A. Cain. "A Tapered Phased Array Ultrasound Transducer for Hyperthermia Treatment." IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 34, no. 4 (1987): 446–53. http://dx.doi.org/10.1109/t-uffc.1987.26965.

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Phipps, Marshal A., Thomas J. Manuel, Michelle K. Sigona, et al. "Image guidance and beam localization for transcranial focused ultrasound therapy." Journal of the Acoustical Society of America 152, no. 4 (2022): A154. http://dx.doi.org/10.1121/10.0015867.

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Therapeutic uses of transcranial focused ultrasound (tFUS) in the brain are being widely explored in both clinical and research settings from tissue destruction to blood brain barrier opening (BBBO) to neuromodulation. The appeal of tFUS is the ability to target structures throughout the brain with a millimeter scale focus. In order to understand the outcome of the treatment or experiment it is important to ensure the tFUS beam is targeted to and located at the region of interest. Image guidance allows for targeting of anatomical or functional structures within the brain. Here we present a targeting and localization scheme where optical tracking of the transducer is used to target the tFUS focus to a brain region within a previously acquired image and MR acoustic radiation force imaging is used to localize the beam in the brain to ensure the focus is at the target. By combining this targeting and localization scheme with a phased array transducer we are able to then steer the focus to ensure accurate sonications of specific brain regions using tFUS. This talk will discuss the application of this method to two different phased array transducers used for neuromodulation and BBBO in nonhuman primates.

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YANG, FENG-YI, TZU-JUNG MAO, YUNG-YAW CHEN, HSU CHANG, and WIN-LI LIN. "BEAM STEERING AND FOCUSING ABILITY OF A CONTACT ULTRASOUND TRANSDUCER FOR TRANSSKULL BRAIN DISEASE THERAPY." Biomedical Engineering: Applications, Basis and Communications 18, no. 06 (2006): 328–36. http://dx.doi.org/10.4015/s1016237206000488.

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This paper was to examine the steering and focusing ability of a contact hemispherical ultrasound transducer (80 mm radius of curvature, 160 mm diameter) for transskull brain diseases therapy without skull-specific aberration correction. This work employs a simulation program to investigate the effect of ultrasound transducer parameters on the steering and focusing ability for transskull therapy. The acoustic pressure distribution and the grating lobes in tissue were used to determine the steering and focusing ability of this transducer for a set of given conditions. Simulation results demonstrated that this hemispherical phased array transducer with low frequencies can steer a high-pressure focal zone in a large range within the brain. The peak and size of the high-pressure focal zone mainly depend on ultrasound frequency and the steering distance of the focal zone. By comparing the peak pressures between the focal zone and the grating lobe, 0.1 MHz transducer performed the desired results for large ranges (140 mm x-y direction and 138 mm z direction) of beam steering. The results reveal the feasibility of using a hemispherical phased array transducer with beam steering method at low frequency for brain diseases therapy within almost full range of the brain without performing a craniectomy.

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Liu, Li, and Jian Sun. "A Study of High Intensity Focusing Ultrasonic Transducer." Applied Mechanics and Materials 201-202 (October 2012): 20–23. http://dx.doi.org/10.4028/www.scientific.net/amm.201-202.20.

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High intensity focused ultrasound (HIFU) is the fourth brand-new and efficient means to cure tumour acknowledged by the medical field. Study of ultrasonic transducer is a core part of HIFU technique, In order to ensure reliability and safety of treatment, it is a key for HIFU technique to realize accurate focusing of ultrasonic energy. In the thesis, ultrasonic focusing method, studies of current situations of cell and multiplex array focusing transducers and their existing problems are illustrated based on analyzing challenges faced by HIFU treatment at present. This study suggested that phased array was theoretically easy for realizing accurate control of computer， however, unbeneficial factors and engineering technical problems still exist; How to promote intensity of the focal spot of cell array focusing transducer, enlarge scope of the focal area and improve control way of the focal spot was a bottleneck problem for publicizing and applying cell array focusing transducer and one of urgent research topics for ensuring curative effect of HIFU and avoiding heat damages.

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Hall, Timothy L., Jonathan R. Sukovich, Jon Cannata, J. Brian Fowlkes, and Zhen Xu. "Instrumentation for histotripsy ultrasound therapy: Evolution toward the clinic." Journal of the Acoustical Society of America 153, no. 3_supplement (2023): A138. http://dx.doi.org/10.1121/10.0018425.

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Histotripsy is a method of ultrasound therapy using very intense, focused sound fields to fragment tissue causing controlled and localized necrosis principally through mechanical actions of cavitation. Highly specialized instrumentation (transducers and electrical drivers) is required to produce these extreme sound fields for research into cavitation physics and therapeutic applications of histotripsy. This paper will describe the evolution of histotripsy instrumentation from the first devices up to the latest phased-array systems with hundreds of channels and transmit-receive capability. While early histotripsy systems used tone bursts generators with limited bandwidth (called “class-D” circuits) for transducer excitation, more recent ones are based on a switched inductor principle to produce shorter duration acoustic emissions. This method has been tested for peak excitation voltages up to 5 kV and 40 A in compact modular systems suitable for phased-arrays. Receive of acoustic signals by the therapeutic array for aberration correction and cavitation mapping is achieved by sensing current generated by the transducer greatly simplifying transmit-receive circuitry while maintaining very large dynamic range. A novel distributed architecture was developed for data handling and signal processing using off-the-shelf FPGA evaluation modules interfaced by ethernet. These latest features will be key to successful clinical translation and widespread adoption of histotripsy.

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11

Goldberg, R. "Phased array imaging with a copolymer transducer." Ultrasonic Imaging 13, no. 2 (1991): 202. http://dx.doi.org/10.1016/0161-7346(91)90116-y.

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Smith, S. "Phased array imaging with a copolymer transducer." Ultrasonic Imaging 12, no. 2 (1990): 147–48. http://dx.doi.org/10.1016/0161-7346(90)90202-9.

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Pua, E. C., J. T. Yen, and S. W. Smith. "Real-Time Cylindrical Curvilinear 3-D Ultrasound Imaging." Ultrasonic Imaging 25, no. 3 (2003): 137–50. http://dx.doi.org/10.1177/016173460302500302.

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In patients who are obese or exhibit signs of pulmonary disease, standard transthoracic scanning may yield poor quality cardiac images. For these conditions, two-dimensional transesophageal echocardiography (TEE) is established as an essential diagnostic tool. Current techniques in transesophageal scanning, though, are limited by incomplete visualization of cardiac structures in close proximity to the transducer. Thus, we propose a 2D curvilinear array for 3D transesophageal echocardiography in order to widen the field of view and increase visualization close to the transducer face. In this project, a 440 channel 5 MHz two-dimensional array with a 12.6 mm aperture diameter on a flexible interconnect circuit has been molded to a 4 mm radius of curvature. A 75% element yield was achieved during fabrication and an average −6dB bandwidth of 30% was observed in pulse-echo tests. Using this transducer in conjunction with modifications to the beam former delay software and scan converter display software of the our 3D scanner, we obtained cylindrical real-time curvilinear volumetric scans of tissue phantoms, including a field of view of greater than 120° in the curved, azimuth direction and 65° phased array sector scans in the elevation direction. These images were achieved using a stepped subaperture across the cylindrical curvilinear direction of the transducer face and phased array sector scanning in the noncurved plane. In addition, real-time volume rendered images of a tissue mimicking phantom with holes ranging from 1 cm to less than 4 mm have been obtained. 3D color flow Doppler results have also been acquired. This configuration can theoretically achieve volumes displaying 180° by 120.° The transducer is also capable of obtaining images through a curvilinear stepped subaperture in azimuth in conjunction with a rectilinear stepped subaperture in elevation, further increasing the field of view close to the transducer face. Future work includes development of an array for adapting these modifications to a 6 mm diameter en do scope probe.

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Dean, MD, Anthony J., Bon S. Ku, MD, and Eli M. Zeserson, MD. "The utility of handheld ultrasound in an austere medical setting in Guatemala after a natural disaster." American Journal of Disaster Medicine 2, no. 5 (2007): 249–56. http://dx.doi.org/10.5055/ajdm.2007.0033.

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Objective: To identify equipment needs, utility, clinical applications, and acuity of diagnoses made by hand-carried ultrasound (HCU) after a natural disaster.Methods: An HCU with four probes (curved array, linear array, phased array, and endocavitary) was taken to the site of a natural disaster in Guatemala as part of the relief effort after mudslides killed approximately 1,000 people. Ultrasound (US) scans were classified by transducer type, anatomic region, presenting complaint, and therapeutic urgency of treatment.Results: Ninety-nine patients received 137 US: 58 pelvic, 34 right upper quadrant, 23 renal, six other abdominal, five orthopedic, four cardiac, three pleura and lung, three soft tissue, and one focused assessment by sonography in trauma. Acuity of presenting illness: 23 percent 24 hours, 15 percent 1-14 days, 44 percent 14 days. Eighteen percent were performed in prenatal clinic. Results of US ruled in 12 percent with an emergent problem and excluded disease in 42 percent. In 14 percent, US diagnosed a problem needing f/u in 2 weeks, and 32 percent with a problem needing long-term observation. Transducer utilization was general purpose curved array 88 percent, linear array 10 percent, endocavitary 8 percent, and phased array 4 percent.Conclusions: HCU has a range of applications in an austere medical setting after a natural disaster. Most can be dealt with using a single transducer.

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Ries, Loriann L., and Stephen W. Smith. "Phase Aberration Correction in Two Dimensions Using a Deformable Array Transducer." Ultrasonic Imaging 17, no. 3 (1995): 227–47. http://dx.doi.org/10.1177/016173469501700303.

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Phase aberrations due to tissue inhomogeneities degrade medical ultrasound images by disrupting the ultrasound beam focus. Currently, phase correction algorithms are implemented by adjusting the electronic phase delays used to steer and focus the ultrasound beam. This means that a two-dimensional array is necessary to completely correct two-dimensional aberrations in tissue. However, two-dimensional arrays are a complex option due to their large number of elements and poor sensitivity. Instead of using a full two-dimensional array, a new technique is proposed, similar to one used in adaptive optics, which uses a deformable transducer of significantly fewer channels for two-dimensional phase correction. Phase correction in azimuth is achieved by altering the electronic phase delay of the element. However, phase correction in elevation is achieved by tilting the element in elevation with a piezoelectric actuator. Comparison of simulations of the new phase correction transducer versus the conventional phase correction technique have shown that a deformable 1 × N or 2 × N transducer can approach the image quality of a 4 × N two-dimensional array or greater. A prototype 1 times 32 array with eight low frequency piezoelectric actuators has been constructed such that every four ultrasonic transducer elements in azimuth are mounted on one independently controlled actuator. This prototype transducer was used to test the ability of a deformable array to produce real time phased array scans and to simulate on-line phase correction by tilting the elements in the elevation direction.

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Lourenço de Oliveira, P., F. Rodes, C. Mougenot, and C. Moonen. "Adjustable impedance tuner for ultrasound phased-array transducer at 1.5 MHz." Electronics Letters 45, no. 17 (2009): 913. http://dx.doi.org/10.1049/el.2009.0149.

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Solomon, Rodney J., and Benjamin M. Herrick. "Two-dimensional phased array ultrasound transducer with a convex enviromental barrier." Journal of the Acoustical Society of America 112, no. 4 (2002): 1246. http://dx.doi.org/10.1121/1.1520974.

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Goldberg, Richard L., Stephen W. Smith, and Lewis F. Brown. "In Vivo Imaging Using a Copolymer Phased Array." Ultrasonic Imaging 14, no. 3 (1992): 234–48. http://dx.doi.org/10.1177/016173469201400302.

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Phased-array images have been obtained in vivo with a steered copolymer array operating at 2.5 MHz. The array was fabricated using 28 μm copolymer film, λ/4 resonant at 21 MHz, which was bonded to a glass ceramic backing with a thin film bond. The 32 array elements were created by laser ablation of the continuous gold electrode on one side of the film. The transducer was driven by 200 V shock excitation, and the received signal was processed by 32 custom IC preamplifiers that were mounted to the array connector. The amplifiers had a high input impedance compared to that of the array elements and their output impedance matched that of the coaxial cable that connected to the scanner. Because the copolymer transducer had a broad bandwidth, the spectrum of the pulse echo image was modified by the frequency dependent attenuation of tissue and the bandpass of the ultrasound scanner, resulting in a center frequency of 2.5 MHz. The performance of the copolymer array was compared to that of a 3 MHz, PZT array with similar dimensions. On the Duke phased-array scanner, the copolymer sensitivity was 28 dB less than that of PZT. The copolymer elements had a 6 dB pulse-echo angular response of 30°, and the interelement cross-coupling was −35 dB. Phased-array images were made of the heart of a 25 year-old normal male.

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Nartov, F. A., R. P. Williams, and V. A. Khokhlova. "Electronic Focus Steering Capabilities of a Diagnostic-Type Linear Ultrasound Array Designed for High Power Therapy and Its Visualization." Acoustical Physics 70, no. 1 (2024): 165–74. http://dx.doi.org/10.1134/s1063771023601292.

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Abstract The focus steering capabilities of a 1 MHz linear phased array transducer (64 rectangular elements, 14.8 × 51.2 mm aperture) intended for drug delivery applications in abdominal organs were assessed and compared with its design-stage computer model. Acoustic fields generated by the transducer and predicted by the models of an ideal array with uniformly vibrating elements and either a plane or a cylindrically focused surface were simulated using the Rayleigh integral and angular spectrum methods. The boundary conditions for the transducer were reconstructed from acoustic holography measurements performed for selected focusing configurations of the array and also synthesized from holography data measured for each of its individual elements. It was shown that the transducer field with electronic focus steering can be accurately synthesized based on the holography data of its elements, which significantly simplified acoustic field characterization. Variability of the power and directivity patterns of the array elements were analyzed. A twofold smaller range of electronic steering in the transverse direction for the transducer compared to its computer model is discussed.

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Mi, Bao, and Charles Ume. "Real-Time Weld Penetration Depth Monitoring With Laser Ultrasonic Sensing System." Journal of Manufacturing Science and Engineering 128, no. 1 (2005): 280–86. http://dx.doi.org/10.1115/1.2137747.

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A real-time ultrasound-based system for controlling robotic weld quality by monitoring the weld pool is presented. The weld penetration depth is one of the most important geometric parameters that define weld quality, hence, remains a key control quantity. The sensing system is based on using a laser phased array technique to generate focused and steered ultrasound, and an electromagnetic acoustic transducer (EMAT) as a receiver. When a pulsed laser beam is incident on the surface of a condensed matter, either the thermoelastic expansion or ablation induces mechanical vibrations that propagate as ultrasound within the specimen. Both the ultrasound generation by the laser phased array and the reception by the EMAT are noncontact, which eliminates the need for a couplant medium. They are capable of operating at high temperatures involved in the welding process. The ultrasound generated by the laser phased array propagates through the weld pool and is picked up by the EMAT receiver. A signal-processing algorithm based on a cross-correlation technique has been developed to estimate the time-of-flight (TOF) of the ultrasound. The relationship between the TOF and the penetration depth of the weld has been established experimentally and analytically. The analytical relationship between the TOF and the penetration depth, which is obtained by the ray-tracing algorithm and geometric analysis, agrees well with the experimental measurements.

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Cho, Sungjong, Hyunjo Jeong, and Ik Keun Park. "Optimal Design of Annular Phased Array Transducers for Material Nonlinearity Determination in Pulse–Echo Ultrasonic Testing." Materials 13, no. 23 (2020): 5565. http://dx.doi.org/10.3390/ma13235565.

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Nonlinear ultrasound has been proven to be a useful nondestructive testing tool for micro-damage inspection of materials and structures operating in harsh environment. When measuring the nonlinear second harmonic wave in a solid specimen in the pulse–echo (PE) testing mode, the stress-free boundary characteristics brings the received second harmonic component close to zero. Therefore, the PE method has never been employed to measure the so-called “nonlinear parameter (β)”, which is used to quantify the degree of micro-damage. When there are stress-free boundaries, a focused beam is known to improve the PE reception of the second harmonic wave, so phased-array (PA) transducers can be used to generate the focused beam. For the practical application of PE nonlinear ultrasonic testing, however, it is necessary to develop a new type of PA transducer that is completely different from conventional ones. In this paper, we propose a new annular PA transducer capable of measuring β with improved second harmonic reception in the PE mode. Basically, the annular PA transducer (APAT) consists of four external ring transmitters and an internal disk receiver at the center. The focused beam properties of the transducers are analyzed using a nonlinear sound beam model which incorporates the effects of beam diffraction, material attenuation, and boundary reflection. The optimal design of the APAT is performed in terms of the maximum second harmonic reception and the total correction close to one, and the results are presented in detail.

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Guo, Jian Qiang, Biao Zheng, Lin Chen, et al. "Research on Improving Lateral Resolution of Ultrasound Phased Array Elements by Using Sparse Matrix." Applied Mechanics and Materials 380-384 (August 2013): 3409–12. http://dx.doi.org/10.4028/www.scientific.net/amm.380-384.3409.

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In the phased array imaging system, in order to get better images,the lateral resolution need to be improved and the grating lobes need to be eliminated. Restrainning the width of the main lobe is a way to improve the lateral resolution of the system. This article designed the non-periodic distribution of elements to decrease the width of main lobe of the transducer using sparse matrix methods. In this way, we can improve the lateral resolution, resolve the problem of high-density of elements in phased array element, eliminate the impact of the gate lobe, lowerring the effects of radiation in the neighboring elements, save costs and overcome the difficulty in production of elements.

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Wong, C. M., S. F. Chan, R. Liu, et al. "20-MHz phased array ultrasound transducer for in vivo ultrasound imaging of small animals." Ultrasonics 126 (December 2022): 106821. http://dx.doi.org/10.1016/j.ultras.2022.106821.

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Makūnaitė, Monika, Rytis Jurkonis, Arūnas Lukoševičius, and Mindaugas Baranauskas. "Main Uncertainties in the RF Ultrasound Scanning Simulation of the Standard Ultrasound Phantoms." Sensors 21, no. 13 (2021): 4420. http://dx.doi.org/10.3390/s21134420.

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Ultrasound echoscopy technologies are continuously evolving towards new modalities including quantitative parameter imaging, elastography, 3D scanning, and others. The development and analysis of new methods and algorithms require an adequate digital simulation of radiofrequency (RF) signal transformations. The purpose of this paper is the quantitative evaluation of RF signal simulation uncertainties in resolution and contrast reproduction with the model of a phased array transducer. The method is based on three types of standard physical phantoms. Digital 3D models of those phantoms are composed of point scatterers representing the weak backscattering of the background material and stronger backscattering from inclusions. The simulation results of echoscopy with sector scanning transducer by Field II software are compared with the RF output of the Ultrasonix scanner after scanning standard phantoms with 2.5 MHz phased array. The quantitative comparison of axial, lateral, and elevation resolutions have shown uncertainties from 9 to 22% correspondingly. The echoscopy simulation with two densities of scatterers is compared with contrast phantom imaging on the backscattered RF signals and B-scan reconstructed image, showing that the main sources of uncertainties limiting the echoscopy RF signal simulation adequacy are an insufficient knowledge of the scanner and phantom’s parameters. The attempt made for the quantitative evaluation of simulation uncertainties shows both problems and the potential of echoscopy simulation in imaging technology developments. The analysis presented could be interesting for researchers developing quantitative ultrasound imaging and elastography technologies looking for simulated raw RF signals comparable to those obtained from real ultrasonic scanning.

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Liu, Xu, Ren Ma, Mingpeng Wang, et al. "A phased array ultrasonic transducer linear sinusoidal driving system for ultrasound neuromodulation." Applied Acoustics 222 (June 2024): 109995. http://dx.doi.org/10.1016/j.apacoust.2024.109995.

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Lean, Hui Qi, and Yufeng Zhou. "Acoustic Field of Phased-Array Ultrasound Transducer with the Focus/Foci Shifting." Journal of Medical and Biological Engineering 39, no. 6 (2019): 919–31. http://dx.doi.org/10.1007/s40846-019-00464-z.

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Phipps, M. Anthony, Sumeeth Jonathan, Pai-Feng Yang, Li Min Chen, William Grissom, and Charles F. Caskey. "A reduced aperture allows for transcranial focus localization at lower pressure." JASA Express Letters 2, no. 6 (2022): 062001. http://dx.doi.org/10.1121/10.0011695.

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Localizing the focus during transcranial focused ultrasound procedures is important to ensure accurate targeting of specific brain regions and interpretation of results. Magnetic resonance acoustic radiation force imaging uses the displacement induced by the ultrasound focus in the brain to localize the beam, but the high pressure required to displace brain tissue may cause damage or confounds during subsequent neuromodulatory experiments. Here, reduced apertures were applied to a phased array transducer to generate comparable displacement to the full aperture but with 20% lower free field pressure.

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Hynynen, Kullervo. "Fully electronically steerable high power ultrasound phased arrays for therapy—A review of progress." Journal of the Acoustical Society of America 153, no. 3_supplement (2023): A102. http://dx.doi.org/10.1121/10.0018306.

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When combined with imaging-guidance focused ultrasound (FUS) provides means for localized delivery of mechanical energy deep into tissues. This focal energy deposition can modify tissue function via thermal or mechanical interactions with the tissue. Traditionally, ultrasound has been focused using spherically curved phased arrays that allow limited electronic steering around geometric focus of the array. To have a fully electronically steered arrays requires the transducer element size to be &lt; wavelength/2 of the ultrasound wave. One way to accomplish this is to use sparse arrays with small transducer elements, the other is to have fully populated arrays with thousands of elements and required electronic complexity. However, the electrical impedance of small transducer elements is high and their efficiency is low and it has been difficult to manufacture arrays with adequate acoustic power. In this talk we will describe how these challenges can be solved with novel manufacturing methods and how we developed complete image-guided systems for both animal and clinical testing. We will also describe our experience with these systems for both brain and body treatments.

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Fu, Yang, Kai Ming Lin, Hui Huang, and Wei Feng Zhang. "S-Scan of Ultrasonic Phased Array Testing for Electrofusion Joints of Polyethylene Pipes." Advanced Materials Research 284-286 (July 2011): 1823–26. http://dx.doi.org/10.4028/www.scientific.net/amr.284-286.1823.

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Electrofusion joint is used widely for PE pipes; the quality of the joint influences the safety of gas distribution system. Proven and reliable NDT technology of the joint is immature. The attenuation of ultrasound in PE is higher than for metals. Defects Include voids, cracks, bad fusion interfaces, dislocations of heating wires, could find be ultrasonic phased array testing. Examination time, surface of specimen, transducer, calibration block, resolution, examination range and couplant are recommend.

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Foster, F. Stuart, John Hossack, and S. Lee Adamson. "Micro-ultrasound for preclinical imaging." Interface Focus 1, no. 4 (2011): 576–601. http://dx.doi.org/10.1098/rsfs.2011.0037.

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Over the past decade, non-invasive preclinical imaging has emerged as an important tool to facilitate biomedical discovery. Not only have the markets for these tools accelerated, but the numbers of peer-reviewed papers in which imaging end points and biomarkers have been used have grown dramatically. High frequency ‘micro-ultrasound’ has steadily evolved in the post-genomic era as a rapid, comparatively inexpensive imaging tool for studying normal development and models of human disease in small animals. One of the fundamental barriers to this development was the technological hurdle associated with high-frequency array transducers. Recently, new approaches have enabled the upper limits of linear and phased arrays to be pushed from about 20 to over 50 MHz enabling a broad range of new applications. The innovations leading to the new transducer technology and scanner architecture are reviewed. Applications of preclinical micro-ultrasound are explored for developmental biology, cancer, and cardiovascular disease. With respect to the future, the latest developments in high-frequency ultrasound imaging are described.

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Balakshy, Vladimir, Maxim Kupreychik, Sergey Mantsevich, and Vladimir Molchanov. "Acousto-Optic Cells with Phased-Array Transducers and Their Application in Systems of Optical Information Processing." Materials 14, no. 2 (2021): 451. http://dx.doi.org/10.3390/ma14020451.

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This paper presents the results of theoretical and experimental studies of anisotropic acousto-optic interaction in a spatially periodical acoustic field created by a phased-array transducer with antiphase excitation of adjacent sections. In this case, contrary to the nonsectioned transducer, light diffraction is absent when the optical beam falls on the phased-array cell at the Bragg angle. However, the diffraction takes place at some other angles (called “optimal” here), which are situated on the opposite sides to the Bragg angle. Our calculations show that the diffraction efficiency can reach 100% at these optimal angles in spite of a noticeable acousto-optic phase mismatch. This kind of acousto-optic interaction possesses a number of interesting regularities which can be useful for designing acousto-optic devices of a new type. Our experiments were performed with a paratellurite (TeO2) cell in which a shear acoustic mode was excited at a 9∘ angle to the crystal plane (001). The piezoelectric transducer had to nine antiphase sections. The efficiency of electric to acoustic power conversion was 99% at the maximum frequency response, and the ultrasound excitation band extended from 70 to 160 MHz. The experiments have confirmed basic results of the theoretical analysis.

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Jones, Ryan M., Dallan McMahon, Dallas Leavitt, et al. "Ultrasound-guided microbubble-mediated brain therapy with a modular transmit/receive phased array." Journal of the Acoustical Society of America 152, no. 4 (2022): A153. http://dx.doi.org/10.1121/10.0015863.

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The development of low-cost, ultrasound-guided focused ultrasound (USgFUS) treatment platforms is expected to advance the adoption of microbubble (MB)-mediated brain therapy by improving access to the technology. Our group has designed and fabricated clinical-scale transmit/receive phased array systems for MB-mediated USgFUS brain therapy. Acoustic field simulations were carried out to optimize array element placement, and transducer scaffolds were constructed using 3D printing techniques. These devices have been employed for skull computed tomography-array registration, 3D spatial mapping of MB activity in vivo through ex-vivo human skullcaps via noninvasive aberration correction methods, and we have harnessed this spatiotemporal cavitation information to calibrate exposure levels for safe volumetric blood-brain barrier opening. At higher exposure levels, we have demonstrated the ability of 3D MB imaging data to predict the tissue damage volume distributions induced during nonthermal brain ablation. Ultrafast processing of acoustic emissions data has been shown to uncover MB dynamics hidden by conventional whole-burst temporal averaging, and can inform temporal undersampling strategies when millisecond-long tone bursts are applied. Machine learning approaches can assist with image-based classification of MB activity, which may result in finer control of the induced bioeffects. This talk will focus on our recent results obtained with a novel modular USgFUS phased array system.

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Turnbull, Daniel H., Paul K. Lum, Andrew T. Kerr, and F. Stuart Foster. "Simulation of B-Scan Images from Two-Dimensional Transducer Arrays: Part I - Methods and Quantitative Contrast Measurements." Ultrasonic Imaging 14, no. 4 (1992): 323–43. http://dx.doi.org/10.1177/016173469201400401.

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Recently, theoretical investigations of the beamforming capability of two-dimensional (2-D) transducer arrays have characterized the array parameters required to steer a symmetrically focused ultrasound beam up to 45° off-axis. These investigations have also shown that the number of elements in a steered 2-D array can be dramatically reduced by using a sparse set of elements, randomly distributed throughout the aperture of the transducer. The penalty paid for the use of a sparse array is the development of a “pedestal” sidelobe in the beam profile, the amplitude of which increases as the number of elements in the array decreases. In this paper the potential of 2-D arrays for medical imaging is assessed by simulating B-scan images of spherical lesions, both cystic and scattering, embedded in a large random scattering volume. Similar contrast characteristics over a range of cyst sizes are demonstrated for a dense 2-D array and a sparse array with 1/8th the number of elements, both operating at 5 MHz. A 32nd order sparse array is shown to perform at a reduced level, producing unacceptable artifactual echoes within images of cysts. The 8th order sparse array pattern has been fabricated on a fixed-focus poly(vinylidene difluoride) transducer using photolithographic, techniques. Experimental images from this transducer are used to verify some of the theoretical predictions made in this paper. Comparisons between simulated B-scan images from linear and 2-D phased arrays are presented in a companion paper.

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Zubair, Muhammad, Imad Uddin, Robert Dickinson, and Chris J. Diederich. "Delivering Volumetric Hyperthermia to Head and Neck Cancer Patient-Specific Models Using an Ultrasound Spherical Random Phased Array Transducer." Bioengineering 12, no. 1 (2024): 14. https://doi.org/10.3390/bioengineering12010014.

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In exploring adjuvant therapies for head and neck cancer, hyperthermia (40–45 °C) has shown efficacy in enhancing chemotherapy and radiation, as well as the delivery of liposomal drugs. Current hyperthermia treatments, however, struggle to reach large deep tumors uniformly and non-invasively. This study investigates the feasibility of delivering targeted uniform hyperthermia deep into the tissue using a non-invasive ultrasound spherical random phased array transducer. Simulations in 3D patient-specific models for thyroid and oropharyngeal cancers assessed the transducer’s proficiency. The transducer consisting of 256 elements randomly positioned on a spherical shell, operated at a frequency of 1 MHz with various phasing schemes and power modulations to analyze 40, 41, and 43 °C isothermal volumes and the penetration depth of the heating volume, along with temperature uniformity within the target area using T10, T50, and T90 temperatures, across different tumor models. Intensity distributions and volumetric temperature contours were calculated to define moderate hyperthermia boundaries. The results indicated the array’s ability to produce controlled heating volumes from 1 to 48 cm3 at 40 °C, 0.35 to 27 cm3 at 41 °C, and 0.1 to 8 cm3 at 43 °C. The heating depths ranged from 7 to 39 mm minimum and 52 to 59 mm maximum, measured from the skin’s inner surface. The transducer, with optimal phasing and water-cooled bolus, confined the heating to the targeted regions effectively. Multifocal sonications also improved the heating homogeneity, reducing the length-to-diameter ratio by 38% when using eight foci versus a single one. This approach shows potential for treating a range of tumors, notably deep-seated and challenging oropharyngeal cancers.

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Steinberg, Bernard D. "A Discussion of Two Wavefront Aberration Correction Procedures." Ultrasonic Imaging 14, no. 4 (1992): 387–97. http://dx.doi.org/10.1177/016173469201400405.

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This review paper discusses the basic properties of two adaptive signal processing procedures for dealing with weak scattering in a phased array transducer system. A fundamental improvement in the lateral resolution of ultrasonic echo scanners will result if the weight vector of a large phased array transducer can be modified to account for distortion in the propagation medium. Lateral resolution in most tissue is limited to a few mm by wavefront-distortion-induced sound-speed variations. One important wavefront-distortion source is scattering from local speed variations within large and reasonably homogeneous tissue beds such as the liver. Scattering disperses some energy from the beam and perturbs the wavefront, thereby distorting the image and limiting the resolution to the scale of the distortion. Often, such scattering is weak, meaning that most of the energy in the beam is unscattered. The total field at the receiving transducer is the vector sum of the unscattered and scattered fields. In weak scattering the unscattered field is dominant and the resultant field can be treated as the unscattered field plus a perturbation. The net effect is primarily a distorted phasefront, while the ampitude or modulus of the wavefront remains reasonably intact. Refraction and strong scattering affect the wavefront more severely and are less responsive to these algorithms.

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Juntarapaso, Yada, Chiaki Miyasaka, Richard L. Tutwiler, and Pavlos Anastasiadis. "Contrast Mechanisms for Tumor Cells by High-frequency Ultrasound." Open Neuroimaging Journal 12, no. 1 (2018): 105–19. http://dx.doi.org/10.2174/1874440001812010105.

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Scanning Acoustic Microscopy (SAM) is a powerful technique for both the non-destructive determination of mechanical and elastic properties of biological specimens and for the ultrasonic imaging at a micrometer resolution. The implication of biomechanical properties during the onset and progression of disease has been established rendering a profound understanding of the relationship between mechanoelastic and biochemical signaling at a molecular level crucial. Computer simulation algorithms were developed for the generation of images and the investigation of contrast mechanisms in high-frequency and ultra-high frequency SAM. Furthermore, we determined the mechanical and elastic properties of HeLa and MCF-7 cells. Algorithms for simulatingV(z)responses were developed based on the ray and wave theory (angular spectrum). Theoretical simulations for high-frequency SAM array designs were performed with the Field II software. In these simulations, we applied phased array beam formation and dynamic apodization and focusing. The purpose of our transducer simulations was to explore volumetric imaging capabilities. The novel transducer arrays designed in this research aim at improving the performance of SAM systems by introducing electronic steering and hence, allowing for the 4D imaging of cells and tissues.

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Chen, Gin-Shin, Jonathan Cannata, Ruibin Liu, Hsu Chang, and K. Kirk Shung. "DESIGN AND FABRICATION OF HIGH-INTENSITY FOCUSED ULTRASOUND PHASED ARRAY FOR LIVER TUMOR THERAPY." Biomedical Engineering: Applications, Basis and Communications 21, no. 03 (2009): 187–92. http://dx.doi.org/10.4015/s1016237209001246.

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Noninvasive surgery of the liver tumors has been carried out by using the high-intensity focused ultrasound (HIFU). However, the liver tumor can be moved by the human respirations and heartbeats, which may cause the ablation and damage of normal tissues during the sonications of HIFU. The purpose of this study was to design and fabricate a cylindrical HIFU phased array transducer for treating the moving liver tumor efficiently. The total number of the element was 512 but only 256 channels were required since the elements along the elevation direction were connected in pairs with respect to the central line of the array. Field II software was used to simulate the acoustic field, and a formula for predicting the spatial averaged intensity at focus was developed based on the practical factors. The results of the simulations showed that the cylindrical HIFU phased array in water had a dynamic focusing range from 145 to 175 mm in the depth direction and a steering range from -15 to 15 mm in azimuthal direction with respect to the center of the array. After the dissipation of cables and the attenuation of various media, the designed array could still generate the intensity at focus up to 1095 W/cm2 when the input electrical power was approximately 410 W. The prototype of the array was fabricated and the preliminary test was completed. The testing results showed that each element of the array prototype can work well.

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Kaczkowski, Peter, and Juvenal Ormachea. "The verasonics platform for ultrasound-guided focused ultrasound preclinical studies." Journal of the Acoustical Society of America 153, no. 3_supplement (2023): A101. http://dx.doi.org/10.1121/10.0018303.

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Verasonics, in partnership with Sonic Concepts (Bothell, WA, USA), has developed a turnkey platform for Ultrasound-Guided Focused Ultrasound (USgFUS) therapy with performance over a wide range of acoustic regimes. Built around the Verasonics Vantage HIFU ultrasound research system, it uses a 150 mm diameter, f1 HIFU transducer with 64 (0.5 MHz) or 128 (1.1 and 2 MHz) elements arranged in a spiral pattern that produce a highly focused field with low sidelobes over a 3D steering volume. Guidance and monitoring are provided by a coaxially mounted 128-element broadband phased array imaging transducer that can be rotated about the HIFU axis. Coupling to the subject is achieved by means of a membrane sealed water-filled cone through which degassed and temperature regulated water is circulated. The USgFUS applicator is mounted on an articulated arm that can be mechanically locked with a button actuated servo mechanism. Graphical software enables a conventional therapeutic workflow including imaging with any of several B-Mode and Doppler modalities, positioning of the applicator, focal zone exposure planning, therapy delivery, interleaved ultrasound monitoring using any supplied imaging mode or with Thermal Strain Imaging (TSI), and post-therapy imaging. This talk will describe the platform and provide examples of its capabilities using experiments in scattering phantoms and ex vivo tissues.

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Payne, Allison, Urvi Vyas, Nick Todd, Joshua de Bever, Douglas A. Christensen, and Dennis L. Parker. "The effect of electronically steering a phased array ultrasound transducer on near-field tissue heating." Medical Physics 38, no. 9 (2011): 4971–81. http://dx.doi.org/10.1118/1.3618729.

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Gin-Shin Chen, Che-Yu Lin, Jong Seob Jeong, et al. "Design and characterization of dual-curvature 1.5-dimensional high-intensity focused ultrasound phased-array transducer." IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 59, no. 1 (2012): 150–55. http://dx.doi.org/10.1109/tuffc.2012.2166.

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Wong, Chi-Man, Yan Chen, Haosu Luo, Jiyan Dai, Kwok-Ho Lam, and Helen Lai-wa Chan. "Development of a 20-MHz wide-bandwidth PMN-PT single crystal phased-array ultrasound transducer." Ultrasonics 73 (January 2017): 181–86. http://dx.doi.org/10.1016/j.ultras.2016.09.012.

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Samet, Naïm, Pierre Maréchal, and Hugues Duflo. "Ultrasound monitoring of bubble size and velocity in a fluid model using phased array transducer." NDT & E International 44, no. 7 (2011): 621–27. http://dx.doi.org/10.1016/j.ndteint.2011.06.005.

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Richards, Luke A., Eleanor P. Stride, and Robin O. Cleveland. "Modulating ultrasound field phase and amplitude using foam gratings as an alternative to acoustic lenses." Journal of the Acoustical Society of America 155, no. 3_Supplement (2024): A139. http://dx.doi.org/10.1121/10.0027083.

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There is an increasing number of applications for therapeutic ultrasound, including high intensity focused ultrasound surgery, neuromodulation and drug delivery. For many of these applications, accurate focusing of the ultrasound field at tissue depths of several cm is essential and thus patient-specific acoustic lenses have been widely investigated as an economical alternative to phased array transducers. Lenses can be cast or 3D printed from a range of polymers offering good acoustic impedance matching to human tissue. Disadvantages of polymer lenses, however, include their relatively large size and the difficulties involved in eliminating gas bubbles during production. In this study an alternative approach is investigated using a “grating” comprising a sheet of polymer foam, perforated with a series of pores that act as wave guides. The grating is placed in front of a transducer with the pores arranged to modulate the phase and amplitude of the sound field as required. The gratings can be cheaply and rapidly fabricated, are &lt; 5 mm thick and can achieve phase changes of more than 180° were successfully achieved while maintaining a transmission amplitude of more than 50%.

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Yin, Yuxin, Shouguo Yan, Juan Huang, and Bixing Zhang. "Transcranial Ultrasonic Focusing by a Phased Array Based on Micro-CT Images." Sensors 23, no. 24 (2023): 9702. http://dx.doi.org/10.3390/s23249702.

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In this paper, we utilize micro-computed tomography (micro-CT) to obtain micro-CT images with a resolution of 60 μm and establish a micro-CT model based on the k-wave toolbox, which can visualize the microstructures in trabecular bone, including pores and bone layers. The transcranial ultrasound phased array focusing field characteristics in the micro-CT model are investigated. The ultrasonic waves are multiply scattered in skull and time delays calculations from the transducer to the focusing point are difficult. For this reason, we adopt the pulse compression method and the linear frequency modulation Barker code to compute the time delay and implement phased array focusing in the micro-CT model. It is shown by the simulation results that ultrasonic loss is mainly caused by scattering from the microstructures of the trabecular bone. The ratio of main and side lobes of the cross-correlation calculation is improved by 5.53 dB using the pulse compression method. The focusing quality and the calculation accuracy of time delay are improved. Meanwhile, the beamwidth at the focal point and the sound pressure amplitude decrease with the increase in the signal frequency. Focusing at different depths indicates that the beamwidth broadens with the increase in the focusing depth, and beam deflection focusing maintains good consistency in the focusing effect at a distance of 9 mm from the focal point. This indicates that the phased-array method has good focusing results and focus tunability in deep cranial brain. In addition, the sound pressure at the focal point can be increased by 8.2% through amplitude regulation, thereby enhancing focusing efficiency. The preliminary experiment verification is conducted with an ex vivo skull. It is shown by the experimental results that the phased array focusing method using pulse compression to calculate the time delay can significantly improve the sound field focusing effect and is a very effective transcranial ultrasound focusing method.

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Ellens, Nicholas P. K., Benjamin B. C. Lucht, Samuel T. Gunaseelan, John M. Hudson, and Kullervo H. Hynynen. "A novel, flat, electronically-steered phased array transducer for tissue ablation: preliminary results." Physics in Medicine and Biology 60, no. 6 (2015): 2195–215. http://dx.doi.org/10.1088/0031-9155/60/6/2195.

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Liu, Jingfei, Josquin Foiret, Douglas N. Stephens, Olivier Le Baron, and Katherine W. Ferrara. "Development of a spherically focused phased array transducer for ultrasonic image-guided hyperthermia." Physics in Medicine and Biology 61, no. 14 (2016): 5275–96. http://dx.doi.org/10.1088/0031-9155/61/14/5275.

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Dash, Pradosh Pritam, and Costas Arvanitis. "Heterogenous angular spectrum approach based holograms for trans-skull focused ultrasound therapy." Journal of the Acoustical Society of America 153, no. 3_supplement (2023): A103. http://dx.doi.org/10.1121/10.0018312.

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Focused Ultrasound (FUS) therapy in the brain entails accounting for strong distortions in the transmitted wavefields introduced by the skull. While these aberrations are compensated by MR-guided FUS (MRgFUS) phased array-based systems by adjusting the phase and amplitude of individual transducer elements, their cost and reliance on MRI may limit their widespread adoption. This work presents phase-only acoustic holograms coupled to a single transducer element as a safe, effective, and affordable alternative. We used the Heterogenous Angular Spectrum Approach (HASA) to propagate between the transducer and target plane(s) and applied automated differentiation for gradient computation to iteratively optimize the phase of the holographic lens. To test our design approach, we employed experimentally validated k-wave simulation. Our results show a 9 dB increase in the peak signal-to-noise ratio (PSNR) of the target acoustic field at 1 MHz as compared to the case where aberrations are uncorrected. Furthermore, we addressed the effect of frequency and aperture on the quality of hologram construction. We showed the feasibility of implementing it in a clinical-scale FUS system targeting deep (&gt;6 cm) brain structures. In summary, the combination of HASA with automated differentiation is an efficient and accurate tool for hologram design through heterogeneous media.

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Forsberg, Flemming, William T. Shi, Michael K. Knauer, Anne L. Hall, Chris Vecchio, and Richard Bernardi. "Real-Time Excitation-Enhanced Ultrasound Contrast Imaging." Ultrasonic Imaging 27, no. 2 (2005): 65–74. http://dx.doi.org/10.1177/016173460502700201.

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A new nonlinear contrast specific imaging modality, excitation-enhanced imaging (EEI) has been implemented on commercially-available scanners for real-time imaging. This novel technique employs two acoustic fields: a low-frequency, high-intensity ultrasound field (the excitation field) to actively condition contrast microbubbles, and a second lower-intensity regular imaging field applied shortly afterwards to detect enhanced contrast scattering. A Logiq 9 scanner (GE Healthcare, Milwaukee, WI) with a 3.5C curved linear array and an AN2300 digital ultrasound engine (Analogic Corporation, Peabody, MA) with a P4-2 phased array transducer (Philips Medical Systems, Bothell, WA) were modified to perform EEI on a vector-by-vector basis in fundamental and pulse inversion harmonic grayscale modes. Ultrasound contrast microbubbles within an 8 mm vessel embedded in a tissue-mimicking flow phantom (ATS Laboratories, Bridgeport, CT) were imaged in vitro. While video intensities of scattered signals from the surrounding tissue were unchanged, video intensities of echoes from contrast bubbles within the vessel were markedly enhanced. The maximum enhancement achieved was 10.4 dB in harmonic mode (mean enhancement: 6.3 dB; p=0.0007). In conclusion, EEI may improve the sensitivity of ultrasound contrast imaging, but further work is required to assess the in vivo potential of this new technique.

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Goudarzi, Sobhan, Ryan M. Jones, Yin H. W. Lee, and Kullervo Hynynen. "Transducer module apodization for reducing bone heating during focused ultrasound uterine fibroid ablation." Journal of the Acoustical Society of America 155, no. 3_Supplement (2024): A140. http://dx.doi.org/10.1121/10.0027087.

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During MR-guided focused ultrasound (MRgFUS) for uterine fibroids, thermoablation of tissue near spine/hips is challenging due to bone heating that can cause patient pain and potentially damage nerves. Here we investigate transducer module apodization for maximizing the focal-to-bone heating ratio (ΔT ;ratio) in silico using a 6144-element flat fully populated phased array operating at 0.5 MHz (Arrayus Technologies, Inc.). Acoustic and thermal simulations were performed using anatomies of ten patients who underwent MRgFUS ablation for uterine fibroids with this device as part of a clinical trial (NCT03323905). Transducer modules (64 elements/module) whose beams intersected no-pass regions were identified, their amplitudes were reduced by varying blocking percentage levels, and the resulting temperature field distributions were evaluated across multiple sonications per patient. For all simulated sonications transducer module blocking improved ΔT ;ratio compared to no blocking. In 42% of sonications, full module blocking maximized ΔT ;ratio, with mean improvements of 97% ± 55% and 47% ± 36% in hip and spine compared to no blocking, at the cost of increased focal thermal volumes and acoustic power levels. In the remaining sonications, partial module blocking provided increased ΔT ;ratio values (39% ± 45% in hip, 19% ± 15% in spine targets) relative to full blocking. The optimal blocking percentage varied depending on the specific treatment geometry.

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Kuznetsova, Ekaterina, Michael R. Bailey, Bryan W. Cunitz, et al. "Flexible ultrasound-based system for clinical trial of burst wave lithotripsy and pushing of kidney stones." Journal of the Acoustical Society of America 150, no. 4 (2021): A353. http://dx.doi.org/10.1121/10.0008564.

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Fragmentation of kidney stones by burst-wave lithotripsy (BWL) has shown promising results in preclinical and clinical trials. Based on initial findings, the system was upgraded to enhance imaging, target stones at deeper depths, fragment small stones, and potentially conduct dusting of stones. A 64-element, single-crystal, phased-array imaging probe is coaxially aligned with the therapy probe for image guidance and therapy feedback. Imaging is controlled through a Verasonics Vantage research ultrasound engine capable of harmonic imaging to enhance stone resolution and contrast. These features improve targeting and endpoint detection, particularly for small stones and fragments. New therapy probes were added to effectively target stones with greater skin-to-stone distance, including a higher (800 kHz) frequency transducer to effectively break <4mm stones into sub-millimeter fragments to facilitate passage. The amplifier was upgraded to a custom class D/E design with increased power required by the therapy transducers and is capable of ultrasonic propulsion and real time monitoring of electrical power. This system will provide capabilities to treat a larger patient population as we begin trials breaking and expelling stones in the clinic setting. [Work supported by NIH-P01-DK043881.]

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Journal articles on the topic 'Phased-array ultrasound transducer'

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