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Sample records for phased array ultrasound

  1. Phase estimation for a phased array therapeutic interstitial ultrasound probe.

    PubMed

    Yang, Zhenya; Dillenseger, Jean-Louis

    2012-01-01

    This paper deals about high intensity ultrasound interstitial therapy simulation. The simulated phased array ultrasound probe allows a dynamic electronic focusing of the therapeutic beam. In order to maximize the power deposit at the focal point we propose a method which allows to optimally defining the phase shift of the electrical control signal for each individual element.

  2. Proceedings of the Third EPRI Phased Array Ultrasound Seminar

    SciTech Connect

    2003-12-01

    Phased array technology for ultrasonic examination is providing innovative solutions for nuclear in-service examination applications. EPRI has been a prime mover in the development and deployment of phased array ultrasound applications in the domestic nuclear market over the past decade. As part of this strategic effort, EPRI has hosted a series of seminars on phased array technology and its applications.

  3. Cracks measurement using fiber-phased array laser ultrasound generation

    NASA Astrophysics Data System (ADS)

    Pei, Cuixiang; Demachi, Kazuyuki; Fukuchi, Tetsuo; Koyama, Kazuyoshi; Uesaka, Mitsuru

    2013-04-01

    A phased array laser ultrasound generation system by using fiber optic delivery and a custom-designed focusing objective lens has been developed for crack inspection. The enhancement of crack tip diffraction by using phased array laser ultrasound is simulated with finite element method and validated by experiment. A non-contact and non-destructive measurement of inner-surface cracks by time-of-flight diffraction method using fiber-phased array laser ultrasound generation and electromagnetic acoustic transducer detection has been studied.

  4. A 35 MHz PCMUT phased array for NDE ultrasound

    NASA Astrophysics Data System (ADS)

    Snook, Kevin; Jiang, Xiaoning; Hu, Changhong; Geng, Xuecang; Liu, Ruibin; Welter, John; Shung, Kirk; Hackenberger, Wesley S.

    2009-03-01

    In this paper, the development of a 35 MHz 64-channel Piezoelectric Composite based Micromachined Ultrasound Transducer (PCMUT) phased array for NDE ultrasound application is presented. A 35 MHz PMN-PT single crystal 1-3 composite based PC-MUT phased array was designed with extensive acoustic field and 1D modeling. The initial modeling results demonstrated that the focused detection resolution (10% of -3 dB beam width) could be as small as 30 μm in the azimuth direction. The maximum imaging depth for ceramic samples is around 20 mm. The PC-MUT array being developed will extend the state-of-art NDE phased array technology from approximately 20 MHz to 35 MHz, which will greatly enhance the imaging resolution for a broad range of NDE ultrasound applications.

  5. Design and experiment of 256-element ultrasound phased array for noninvasive focused ultrasound surgery.

    PubMed

    Lu, Mingzhu; Wan, Mingxi; Xu, Feng; Wang, Xiaodong; Chang, Xiaozhen

    2006-12-22

    A 256-element phased array high intensity focused ultrasound system has been designed and constructed in our laboratory. The 256-element spherical-section ultrasound phased array made from piezocomposite material operates at 1.1 MHz with 11-cm radius of curvature, 14-cm outer diameter, and 3.4-cm diameter central hole for mounting diagnostic ultrasound imaging probe. First, the explicit sound field calculation approach for the spherical-section phased array and the genetic optimal algorithm are briefly introduced as the optimal focus pattern control methods. Then, the design guidelines of 256-element spherical-section focused ultrasound phased array and 256-channel driver system are given. The results of single on and off axial focus, multiple on and off axial foci, half sub-array focus pattern provide further evidence for the 3D focus steering and sub-array mode for avoiding obstacles in focused ultrasound surgery. The multi-foci pattern can enlarge the treatment volume to 22 times larger than that of a single focus in one sonication. Finally, in vitro and transparent tissue-mimicking phantom experiment results confirm the ability of 256-element spherical-section phased array system to induce thermal lesions for noninvasive ultrasound surgery.

  6. Phased-array ultrasound technology enhances accuracy of dual frequency ultrasound measurements - towards improved ultrasound bone diagnostics.

    PubMed

    Linder, Hans; Malo, Markus K H; Liukkonen, Jukka; Jurvelin, Jukka S; Töyräs, Juha

    2016-08-01

    Overlying soft tissues attenuate ultrasound backscattered from bone, complicating diagnostics of osteoporosis at the most important fracture sites. Dual-frequency ultrasound technique (DFUS) has been proposed to solve this problem through determination of thickness and composition of overlying soft tissue. This study applies DFUS technique for the first time with a phased-array transducer to investigate if the thickness of two interfering layers (oil and water) can be accurately determined in a variety of configurations. Results indicate that DFUS may be used with phased-array ultrasound systems, making them a suitable combination to consider in future development of clinical in vivo ultrasound methodologies.

  7. Inspecting Composite Ceramic Armor Using Advanced Signal Processing Together with Phased Array Ultrasound

    DTIC Science & Technology

    2010-01-08

    processing techniques have been developed to help improve phased array ultrasonic inspection and analysis of multi-layered ceramic armor panels. The...INSPECTING COMPOSITE CERAMIC ARMOR USING ADVANCED SIGNAL PROCESSING TOGETHER WITH PHASED ARRAY ULTRASOUND J. S. Steckenrider Illinois College...immersion phased array ultrasound system. Some of these specimens had intentional design defects inserted interior to the specimens. Because of the very

  8. Ultrasound cylindrical phased array for transoesophageal thermal therapy: initial studies.

    PubMed

    Melodelima, David; Lafon, Cyril; Prat, Frederic; Birer, Alain; Cathignol, Dominique

    2002-12-07

    This work was undertaken to investigate the feasibility of constructing a cylindrical phased array composed of 64 elements spread around the periphery (OD 10.6 mm) for transoesophageal ultrasound thermotherapy. The underlying operating principle of this applicator is to rotate a plane ultrasound beam electronically. For this purpose, eight adjacent transducers were successively excited with appropriate delay times so as to generate a plane wave. The exposure direction was changed by exciting a different set of eight elements. For these feasibility studies, we used a cylindrical prototype (OD 10.6 mm) composed of 16 elementary transducers distributed over a quarter of the cylinder, all operating at 4.55 MHz. The active part was mechanically reinforced by a rigid damper structure behind the transducers. It was shown that an ultrasound field similar to that emitted by a plane transducer could be generated. Ex vivo experiments on pig's liver demonstrated that the ultrasound beam could be accurately rotated to generate sector-based lesions to a suitable depth (up to 19 mm). Throughout these experiments, exposures lasting 20 s were delivered at an acoustic intensity of 17 W cm(-2). By varying the power from exposure to exposure, the depth of the lesion at different angles could be controlled.

  9. COMPOSITE CERAMIC ARMOR DEFECT ANALYSIS USING PHASED ARRAY ULTRASOUND

    DTIC Science & Technology

    2011-01-30

    background variation. Such an approximation applied to the FFT results of Conclusion Phased - array ultrasonic inspection methods have been...SNR values above 2.55) were statistically defective either. CONCLUSION Phased - array ultrasonic inspection methods have been successfully applied to...4 G.P. Singh and J. W. Davies, “Multiple Transducer Ultrasonic Techniques: Phased Arrays ” In Nondestructive Testing Handbook, 2nd Ed., 7, pp. 284

  10. Cardiac imaging using a phased array ultrasound system. I. System design.

    PubMed

    vonRamm, O T; Thurstone, F L

    1976-02-01

    A new two-dimensional, real-time, high resolution ultrasound imaging system is described. This system uses a linear array of ultrasound transducers to generate tomographic images of the heart in a circular sector format. Phased array techniques allow rapid steering of the ultrasound beam so that images are produced at the rate of 20 per second, or more, while maintaining a resolution of 2-4 mm throughout the field of view.

  11. Modeling and simulation of ultrasound fields generated by 2D phased array transducers for medical applications.

    PubMed

    Matrone, G; Quaglia, F; Magenes, G

    2010-01-01

    Modern ultrasound imaging instrumentation for clinical applications allows real-time volumetric scanning of the patients' body. 4D imaging has been made possible thanks to the development of new echographic probes which consist in 2D phased arrays of piezoelectric transducers. In these new devices it is the system electronics which properly drives the matrix elements and focuses the beam in order to obtain a sequence of volumetric images. This paper introduces an ultrasound field simulator based on the Spatial Impulse Response method which is being properly developed to analyze the characteristics of the ultrasound field generated by a 2D phased array of transducers. Thanks to its high configurability by the user, it will represent a very useful tool for electronics designers in developing 4D ultrasound imaging systems components.

  12. Control of the necrosed tissue volume during noninvasive ultrasound surgery using a 16-element phased array.

    PubMed

    Fan, X; Hynynen, K

    1995-03-01

    Focused high-power ultrasound beams are well suited for noninvasive local destruction of deep target volumes. In order to avoid cavitation and to utilize only thermal tissue damage, high frequencies (1-5 MHz) are used in ultrasonic surgery. However, the focal spots generated by sharply focused transducers become so small that only small tumors can be treated in a reasonable time. Phased array ultrasound transducers can be employed to electronically scan a focal spot or to produce multiple foci in the desired region to increase the treated volume. In this article, theoretical and experimental studies of spherically curved square-element phased arrays for use in ultrasonic surgery were performed. The simulation results were compared with experimental results from a 16-element array. It was shown that the phased array could control the necrosed tissue volume by using closely spaced multiple foci. The phased array can also be used to enlarge a necrosed tissue volume in only one direction at a time, i.e., lateral or longitudinal. The spherically curved 16 square-element phased array can produce useful results by varying the phase and amplitude setting. Four focal points can be easily generated with a distance of two or four wavelengths between the two closest peaks. The maximum necrosed tissue volume generated by the array can be up to sixteen times the volume induced by a similar spherical transducer. Therefore the treatment time could be reduced compared with single transducer treatment.

  13. Dynamic cardiac imaging using a focused, phased-array ultrasound system.

    PubMed

    Kisslo, J A; vonRamm, O T; Thurstone, F L

    1977-07-01

    A two-dimensional ultrasound imaging system capable of producing high resolution, cross-sectional images of the heart in real-time has been developed. This system relies upon phased-array principles to rapidly steer and focus the ultrasound beam through the cardiac structures under investigation. A hand-held, linear array of 24 transducers is manipulated on the anterior chest wall to image various cardiac structures. Images of high line density are presented in selectable sector arcs to a maximum of 90 degrees. This imaging system has proved particularly useful for the detection of a variety of left ventricular and cardiac valvular disease.

  14. Image-guided ultrasound phased arrays are a disruptive technology for non-invasive therapy.

    PubMed

    Hynynen, Kullervo; Jones, Ryan M

    2016-09-07

    Focused ultrasound offers a non-invasive way of depositing acoustic energy deep into the body, which can be harnessed for a broad spectrum of therapeutic purposes, including tissue ablation, the targeting of therapeutic agents, and stem cell delivery. Phased array transducers enable electronic control over the beam geometry and direction, and can be tailored to provide optimal energy deposition patterns for a given therapeutic application. Their use in combination with modern medical imaging for therapy guidance allows precise targeting, online monitoring, and post-treatment evaluation of the ultrasound-mediated bioeffects. In the past there have been some technical obstacles hindering the construction of large aperture, high-power, densely-populated phased arrays and, as a result, they have not been fully exploited for therapy delivery to date. However, recent research has made the construction of such arrays feasible, and it is expected that their continued development will both greatly improve the safety and efficacy of existing ultrasound therapies as well as enable treatments that are not currently possible with existing technology. This review will summarize the basic principles, current statures, and future potential of image-guided ultrasound phased arrays for therapy.

  15. Image-guided ultrasound phased arrays are a disruptive technology for non-invasive therapy

    NASA Astrophysics Data System (ADS)

    Hynynen, Kullervo; Jones, Ryan M.

    2016-09-01

    Focused ultrasound offers a non-invasive way of depositing acoustic energy deep into the body, which can be harnessed for a broad spectrum of therapeutic purposes, including tissue ablation, the targeting of therapeutic agents, and stem cell delivery. Phased array transducers enable electronic control over the beam geometry and direction, and can be tailored to provide optimal energy deposition patterns for a given therapeutic application. Their use in combination with modern medical imaging for therapy guidance allows precise targeting, online monitoring, and post-treatment evaluation of the ultrasound-mediated bioeffects. In the past there have been some technical obstacles hindering the construction of large aperture, high-power, densely-populated phased arrays and, as a result, they have not been fully exploited for therapy delivery to date. However, recent research has made the construction of such arrays feasible, and it is expected that their continued development will both greatly improve the safety and efficacy of existing ultrasound therapies as well as enable treatments that are not currently possible with existing technology. This review will summarize the basic principles, current statures, and future potential of image-guided ultrasound phased arrays for therapy.

  16. Image-guided ultrasound phased arrays are a disruptive technology for non-invasive therapy

    PubMed Central

    Hynynen, Kullervo; Jones, Ryan M.

    2016-01-01

    Focused ultrasound offers a non-invasive way of depositing acoustic energy deep into the body, which can be harnessed for a broad spectrum of therapeutic purposes, including tissue ablation, the targeting of therapeutic agents, and stem cell delivery. Phased array transducers enable electronic control over the beam geometry and direction, and can be tailored to provide optimal energy deposition patterns for a given therapeutic application. Their use in combination with modern medical imaging for therapy guidance allows precise targeting, online monitoring, and post-treatment evaluation of the ultrasound-mediated bioeffects. In the past there have been some technical obstacles hindering the construction of large aperture, high-power, densely-populated phased arrays and, as a result, they have not been fully exploited for therapy delivery to date. However, recent research has made the construction of such arrays feasible, and it is expected that their continued development will both greatly improve the safety and efficacy of existing ultrasound therapies as well as enable treatments that are not currently possible with existing technology. This review will summarize the basic principles, current statures, and future potential of image-guided ultrasound phased arrays for therapy. PMID:27494561

  17. Simulating ultrasound fields for 2D phased-array probes design optimization.

    PubMed

    Matrone, Giulia; Quaglia, Fabio; Magenes, Giovanni

    2011-01-01

    Nowadays, ultrasound diagnostic imaging is one of the non-invasive techniques mostly used in the clinical practice. Recent advances in this field have brought to the development of small and portable systems. New bidimensional probes consisting of 2D phased arrays, allow to obtain real-time 3D representations of moving organs and blood vessels anatomy. Being the complexity of such 4D ultrasound imaging systems significantly increased, new challenges concerning electronics integration arise for designers. In this paper a software simulator is described, which has been developed in order to model ultrasound wave generation, pressure field distribution and echoes reception, with the aim to become a useful tool for optimizing the probe design. The paper mainly focuses on linear ultrasound field modeling; preliminary results on non-linear interactions with contrast agents are also here introduced.

  18. In Vivo Evaluations of a Phased Ultrasound Array for Transesophageal Cardiac Ablation

    NASA Astrophysics Data System (ADS)

    Jaiswal, Devina; Werner, Jacob; Park, Eun-Joo; Francischelli, David; Smith, Nadine Barrie

    2010-03-01

    Atrial fibrillation is one of the most common arrhythmias that affects over 2.2 million Americans each year. Catheter ablation, one of the effective treatments, has shown high rate of success in treating paroxysmal atrial fibrillation. Currently, radiofrequency which is being used for catheter ablation is an invasive procedure. Measurable morbidity and significant costs and time are associated with this modality of treatment of permanent or persistent atrial fibrillation. In order to address these issues, a transesophageal ultrasound applicator for noninvasive cardiac ablation was designed, developed and evaluated. The ultrasound energy delivered by the phased array was used to create a lesion in the myocardial tissue. Various factors, simulation results of transducer arrays, current transesophageal medical devices, and throat anatomy, were considered while designing a phased ultrasound transducer that can be inserted into the esophagus. For this research, a two-dimensional sparse phased array with flat tapered elements was fabricated and evaluated in in vivo experiments. Five pigs were anesthetized; the array was passed transesophagealy and positioned over the heart. An operating frequency of 1.6 MHz and 8˜15 minutes of array operation resulted in both single and multiple lesions on atrial and ventricular myocardium. The average size of lesions was 5.1±2.1 mm in diameter and 7.8±2.5 mm in length. Experimental results indicate that the array delivered sufficient power to produce ablation at the focal point while not grossly damaging the tissue surrounding the area of interest. These results demonstrate a potential application of the ultrasound applicator for noninvasive transesophageal cardiac surgery in atrial fibrillation treatment.

  19. Feasibility of in vivo transesophageal cardiac ablation using a phased ultrasound array.

    PubMed

    Werner, Jacob; Park, Eun-Joo; Lee, Hotaik; Francischelli, David; Smith, Nadine Barrie

    2010-05-01

    Over 2.2 million Americans suffer from atrial fibrillation making it one of the most common arrhythmias. Cardiac ablation has shown a high rate of success in treating paroxysmal atrial fibrillation. Prevailing modalities for this treatment are catheter based radio-frequency ablation or surgery. However, there is measurable morbidity and significant costs and time associated with these invasive procedures. Due to these issues, developing a method that is less invasive to treat atrial fibrillation is needed. In the development of such a device, a transesophageal ultrasound applicator for cardiac ablation was designed, constructed and evaluated. A goal of this research was to create lesions in myocardial tissue using a phased array. Based on multiple factors from array simulations, transesophageal imaging devices and throat anatomy, a phased ultrasound transducer that can be inserted into the esophagus was designed and tested. In this research, a two-dimensional sparse phased array with the aperture size of 20.7 mm x 10.2 mm with flat tapered elements as a transesophageal ultrasound applicator was fabricated and evaluated with in vivo experiments. Five pigs were anesthetized; the array was passed through the esophagus and positioned over the heart. The array was operated for 8-15 min at 1.6 MHz with the acoustic intensity of 150-300 W/cm(2) resulting in both single and multiple lesions on atrial and ventricular myocardium. The average size of lesions was 5.1 +/- 2.1 mm in diameter and 7.8 +/- 2.5 mm in length. Based on the experimental results, the array delivered sufficient power to the focal point to produce ablation while not grossly damaging nearby tissue outside the target area. These results demonstrate a potential application of the ultrasound applicator to transesophageal cardiac surgery in atrial fibrillation treatment.

  20. Principles and applications of a dynamically focused phased array real time ultrasound system.

    PubMed

    Morgan, C L; Trought, W S; Clark, W M; Von Ramm, O T; Thurstone, F L

    1978-12-01

    The physical principles and clinical applications of a high-resolution, dynamically focused phased-array real time ultrasound are described. Advantages of the real time technique include rapid survey capability, efficient selection of an appropriate tomographic plane, identification of pulsating structures, and dynamic studies. The capabilities of a high resolution phased array with extended dynamic focusing to a range of 15-20 cm are demonstrated in vascular, abdominal, and obstetric imaging. Appropriate clinical examples showing normal and pathological anatomy are presented. Comparisons with conventional B scans are illustrated.

  1. Phased Array Ultrasound: Initial Development of PAUT Inspection of Self-Reacting Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Rairigh, Ryan

    2008-01-01

    This slide presentation reviews the development of Phased Array Ultrasound (PAUT) as a non-destructive examination method for Self Reacting Friction Stir Welds (SR-FSW). PAUT is the only NDE method which has been shown to detect detrimental levels of Residual Oxide Defect (ROD), which can result in significant decrease in weld strength. The presentation reviews the PAUT process, and shows the results in comparison with x-ray radiography.

  2. MRI-compatible ultrasound heating system with ring-shaped phased arrays for breast tumor thermal therapy.

    PubMed

    Chen, Hung-Nien; Chen, Guan-Ming; Lin, Bo-Sian; Lien, Pi-Hsien; Chen, Yung-Yaw; Chen, Gin-Shin; Lin, Win-Li

    2013-01-01

    Therapeutic ultrasound transducers can carry out precise and efficient power deposition for tumor thermal therapy under the guidance of magnetic resonance imaging. For a better heating, organ-specific ultrasound transducers with precision location control system should be developed for tumors located at various organs. It is feasible to perform a better heating for breast tumor thermal therapy with a ring-shaped ultrasound phased-array transducer. In this study, we developed ring-shaped phased-array ultrasound transducers with 1.0 and 2.5 MHz and a precision location control system to drive the transducers to the desired location to sonicate the designated region. Both thermo-sensitive hydrogel phantom and ex vivo fresh pork were used to evaluate the heating performance of the transducers. The results showed that the ring-shaped phased array ultrasound transducers were very promising for breast tumor heating with the variation of heating patterns and without overheating the ribs.

  3. Ultrasound array transmitter architecture with high timing resolution using embedded phase-locked loops.

    PubMed

    Smith, Peter R; Cowell, David M J; Raiton, Benjamin; Ky, Chau Vo; Freear, Steven

    2012-01-01

    Coarse time quantization of delay profiles within ultrasound array systems can produce undesirable side lobes in the radiated beam profile. The severity of these side lobes is dependent upon the magnitude of phase quantization error--the deviation from ideal delay profiles to the achievable quantized case. This paper describes a method to improve interchannel delay accuracy without increasing system clock frequency by utilizing embedded phase-locked loop (PLL) components within commercial field-programmable gate arrays (FPGAs). Precise delays are achieved by shifting the relative phases of embedded PLL output clocks in 208-ps steps. The described architecture can achieve the necessary interelement timing resolution required for driving ultrasound arrays up to 50 MHz. The applicability of the proposed method at higher frequencies is demonstrated by extrapolating experimental results obtained using a 5-MHz array transducer. Results indicate an increase in transmit dynamic range (TDR) when using accurate delay profiles generated by the embedded-PLL method described, as opposed to using delay profiles quantized to the system clock.

  4. A 1372-element Large Scale Hemispherical Ultrasound Phased Array Transducer for Noninvasive Transcranial Therapy

    SciTech Connect

    Song, Junho; Hynynen, Kullervo

    2009-04-14

    Noninvasive transcranial therapy using high intensity focused ultrasound transducers has attracted high interest as a promising new modality for the treatments of brain related diseases. We describe the development of a 1372 element large scale hemispherical ultrasound phased array transducer operating at a resonant frequency of 306 kHz. The hemispherical array has a diameter of 31 cm and a 15.5 cm radius of curvature. It is constructed with piezoelectric (PZT-4) tube elements of a 10 mm in diameter, 6 mm in length and 1.4 mm wall thickness. Each element is quasi-air backed by attaching a cork-rubber membrane on the back of the element. The acoustic efficiency of the element is determined to be approximately 50%. The large number of the elements delivers high power ultrasound and offers better beam steering and focusing capability. Comparisons of sound pressure-squared field measurements with theoretical calculations in water show that the array provides good beam steering and tight focusing capability over an efficient volume of approximately 100x100x80 mm{sup 3} with nominal focal spot size of approximately 2.3 mm in diameter at -6 dB. We also present its beam steering and focusing capability through an ex vivo human skull by measuring pressure-squared amplitude after phase corrections. These measurements show the same efficient volume range and focal spot sizes at -6 dB as the ones in water without the skull present. These results indicate that the array is sufficient for use in noninvasive transcranial ultrasound therapy.

  5. A 1372-element Large Scale Hemispherical Ultrasound Phased Array Transducer for Noninvasive Transcranial Therapy

    NASA Astrophysics Data System (ADS)

    Song, Junho; Hynynen, Kullervo

    2009-04-01

    Noninvasive transcranial therapy using high intensity focused ultrasound transducers has attracted high interest as a promising new modality for the treatments of brain related diseases. We describe the development of a 1372 element large scale hemispherical ultrasound phased array transducer operating at a resonant frequency of 306 kHz. The hemispherical array has a diameter of 31 cm and a 15.5 cm radius of curvature. It is constructed with piezoelectric (PZT-4) tube elements of a 10 mm in diameter, 6 mm in length and 1.4 mm wall thickness. Each element is quasi-air backed by attaching a cork-rubber membrane on the back of the element. The acoustic efficiency of the element is determined to be approximately 50%. The large number of the elements delivers high power ultrasound and offers better beam steering and focusing capability. Comparisons of sound pressure-squared field measurements with theoretical calculations in water show that the array provides good beam steering and tight focusing capability over an efficient volume of approximately 100×100×80 mm3 with nominal focal spot size of approximately 2.3 mm in diameter at -6 dB. We also present its beam steering and focusing capability through an ex vivo human skull by measuring pressure-squared amplitude after phase corrections. These measurements show the same efficient volume range and focal spot sizes at -6 dB as the ones in water without the skull present. These results indicate that the array is sufficient for use in noninvasive transcranial ultrasound therapy.

  6. Abdominal and obstetric applications of a dynamically focused phased array real time ultrasound system.

    PubMed

    Morgan, C L; Trought, W S; von Ramm, O T; Thurstone, F L

    1980-05-01

    Abdominal and obstetric applications of a dynamically focused phased array real time ultrasonic system are described. This work was performed utilising both the Thaumascan (two-dimensional, high resolution, actual time, ultrasound, multi-element array scanner) and the first commercial unit based on this system, the Grumman RT-400. Examples of normal and pathological anatomy are presented from over 300 examinations performed to date, including a series of 28 abdominal aortic aneurysms studied with the RT-400. Following electronic alterations in the Thaumascan with resultant improvement in the grey scale, prospective analyses in 86 obstetric and 23 abdominal examinations were undertaken. These studies indicate that fetal, intra-uterine, and abdominal structures can be rapidly and consistently imaged. The value of real time ultrasonic scanning in obstetric and abdominal examinations is illustrated. The principles of dynamically focused phased arrays are described, and the merits and limitations of these systems are discussed.

  7. Fast-pressure field calculations applied to large spherical ultrasound phased arrays designed for thermal therapy

    NASA Astrophysics Data System (ADS)

    Zeng, Xiaozheng; Wu, Liyong; McGough, Robert J.

    2005-04-01

    Large spherical ultrasound phased arrays are ideal for simulation studies of thermal therapy devices designed for noninvasive breast cancer treatments. In a spherical array, circular sources packed in a dense hexagonal arrangement facilitate the most efficient use of the available aperture. Circular sources are also preferred for simulations of large phased arrays because pressure fields are computed more rapidly for circular pistons than for any other transducer geometry. The computation time is further reduced for circular transducers with grid sectoring. With this approach, the grid of computed pressures is divided into several regions, and then grid sectoring applies more abscissas in regions where the pressure integral converges slowly and fewer abscissas where the integral converges rapidly. As a result, the peak value of the numerical error is roughly the same in each sector, so the maximum numerical error in the computed field is maintained while the computation time is significantly reduced. The grid sectoring approach is extended to three dimensions (3D) for pressure field calculations with spherical arrays. In 3D calculations, the sectors are represented by cones, and the intersections between the computational grid and these cones define the boundaries required for grid sectoring. When these cone structures are applied to spherical phased arrays, 3D grid sectoring calculations rapidly compute the pressure fields so that the time required for array design and evaluation is substantially reduced.

  8. Two-dimensional ultrasound phased array design for tissue ablation for treatment of benign prostatic hyperplasia.

    PubMed

    Saleh, K Y; Smith, N B

    2004-02-01

    This paper describes the design, construction and evaluation of a two-dimensional ultrasound phased array to be used in the treatment of benign prostatic hyperplasia. With two-dimensional phased arrays, the focal point position can be controlled by changing the electrical power and phase to the individual elements for focusing and electronically steering in a three-dimensional volume. The array was designed with a steering angle of +/-14 degrees in both transverse and longitudinal directions. A piezoelectric ceramic (PZT-8) was used as the material of the transducer, since it can handle the high power needed for tissue ablation and a matching layer was used for maximum acoustic power transmission to tissue. Analysis of the transducer ceramic and cable impedance has been designed for high power transfer with minimal capacitance and diameter. For this initial prototype, the final construction used magnet compatible housing and cabling for future application in a clinical magnetic resonance imaging system for temperature mapping of the focused ultrasound. To verify the capability of the transducer for focusing and steering, exposimetry was performed and the results correlated well with the calculated field. Ex vivo experiments were performed and indicated the capability of the transducer to ablate tissue using short sonications. For sonications with exposure time of 10, 15 and 20 s, the lesion size was roughly 1.8, 3.0 and 4.3 mm in diameter, respectively, which indicates the feasibility of this device.

  9. The effect of electronically steering a phased array ultrasound transducer on near-field tissue heating

    PubMed Central

    Payne, Allison; Vyas, Urvi; Todd, Nick; Bever, Joshua de; Christensen, Douglas A.; Parker, Dennis L.

    2011-01-01

    Purpose: This study presents the results obtained from both simulation and experimental techniques that show the effect of mechanically or electronically steering a phased array transducer on proximal tissue heating. Methods: The thermal response of a nine-position raster and a 16-mm diameter circle scanning trajectory executed through both electronic and mechanical scanning was evaluated in computer simulations and experimentally in a homogeneous tissue-mimicking phantom. Simulations were performed using power deposition maps obtained from the hybrid angular spectrum (HAS) method and applying a finite-difference approximation of the Pennes’ bioheat transfer equation for the experimentally used transducer and also for a fully sampled transducer to demonstrate the effect of acoustic window, ultrasound beam overlap and grating lobe clutter on near-field heating. Results: Both simulation and experimental results show that electronically steering the ultrasound beam for the two trajectories using the 256-element phased array significantly increases the thermal dose deposited in the near-field tissues when compared with the same treatment executed through mechanical steering only. In addition, the individual contributions of both beam overlap and grating lobe clutter to the near-field thermal effects were determined through comparing the simulated ultrasound beam patterns and resulting temperature fields from mechanically and electronically steered trajectories using the 256-randomized element phased array transducer to an electronically steered trajectory using a fully sampled transducer with 40 401 phase-adjusted sample points. Conclusions: Three distinctly different three distinctly different transducers were simulated to analyze the tradeoffs of selected transducer design parameters on near-field heating. Careful consideration of design tradeoffs and accurate patient treatment planning combined with thorough monitoring of the near-field tissue temperature will

  10. A hybrid computational model for ultrasound phased-array heating in presence of strongly scattering obstacles.

    PubMed

    Botros, Y Y; Volakis, J L; VanBaren, P; Ebbini, E S

    1997-11-01

    A computationally efficient hybrid ray-physical optics (HRPO) model is presented for the analysis and synthesis of multiple-focus ultrasound heating patterns through the human rib cage. In particular, a ray method is used to propagate the ultrasound fields from the source to the frontal plane of the rib cage. The physical-optics integration method is then employed to obtain the intensity pattern inside the rib cage. The solution of the matrix system is carried out by using the pseudo inverse technique to synthesize the desired heating pattern. The proposed technique guides the fields through the intercostal spacings between the solid ribs and, thus, minimal intensity levels are observed over the solid ribs. This simulation model allows for the design and optimization of large-aperture phased-array applicator systems for noninvasive ablative thermal surgery in the heart and liver through the rib cage.

  11. A theoretical assessment of the relative performance of spherical phased arrays for ultrasound surgery.

    PubMed

    Gavrilov, L R; Hand, J W

    2000-01-01

    Computer modeling of spherical-section phased arrays for ultrasound surgery (tissue ablation) is described. The influence on performance of the number of circular elements (68 to 1024), their diameter (2.5 to 10 mm), frequency (1 to 2 MHz), and degree of sparseness in the array is investigated for elements distributed randomly or in square, annular, and hexagonal patterns on a spherical shell (radius of curvature, 120 mm). Criteria for evaluating the quality of the intensity distributions obtained when focusing the arrays both on and away from their center of curvature, and in both single focus and simultaneous multiple foci modes, are proposed. Of the arrays studied, the most favorable performance, for both modes, is predicted for 256 5-mm diameter, randomly distributed elements. For the single focus mode, this performed better than regular arrays of 255 to 1024 elements and, for the case of nine simultaneous foci produced on a coplanar 3x3 grid with 4-mm spacing, better than square, hexagonal, or annular distributed arrays with a comparable number of elements. Randomization improved performance by suppressing grating lobes significantly. For single focus mode, a several-fold decrease in the number of elements could be made without degrading the quality of the intensity distribution.

  12. Detecting failed elements on phased array ultrasound transducers using the Edinburgh Pipe Phantom

    PubMed Central

    Inglis, Scott; Pye, Stephen D

    2016-01-01

    Aims Imaging faults with ultrasound transducers are common. Failed elements on linear and curvilinear array transducers can usually be detected with a simple image uniformity or ‘paperclip’ test. However, this method is less effective for phased array transducers, commonly used in cardiac imaging. The aim of this study was to assess whether the presence of failed elements could be detected through measurement of the resolution integral (R) using the Edinburgh Pipe Phantom. Methods A 128-element paediatric phased array transducer was studied. Failed elements were simulated using layered polyvinyl chloride (PVC) tape as an attenuator and measurements of resolution integral were carried out for several widths of attenuator. Results All widths of attenuator greater than 0.5 mm resulted in a significant reduction in resolution integral and low contrast penetration measurements compared to baseline (p < 0.05). Conclusions Measurements of resolution integral and low contrast penetration both have the potential to be used as straightforward and inexpensive tests to detect failed elements on phased array transducers. Particularly encouraging is the result for low contrast penetration as this is a quick and simple measurement to make and can be performed with many different test objects, thus enabling ‘in-the-field’ checks. PMID:27482276

  13. Detecting failed elements on phased array ultrasound transducers using the Edinburgh Pipe Phantom.

    PubMed

    Welsh, Dan; Inglis, Scott; Pye, Stephen D

    2016-05-01

    Imaging faults with ultrasound transducers are common. Failed elements on linear and curvilinear array transducers can usually be detected with a simple image uniformity or 'paperclip' test. However, this method is less effective for phased array transducers, commonly used in cardiac imaging. The aim of this study was to assess whether the presence of failed elements could be detected through measurement of the resolution integral (R) using the Edinburgh Pipe Phantom. A 128-element paediatric phased array transducer was studied. Failed elements were simulated using layered polyvinyl chloride (PVC) tape as an attenuator and measurements of resolution integral were carried out for several widths of attenuator. All widths of attenuator greater than 0.5 mm resulted in a significant reduction in resolution integral and low contrast penetration measurements compared to baseline (p < 0.05). Measurements of resolution integral and low contrast penetration both have the potential to be used as straightforward and inexpensive tests to detect failed elements on phased array transducers. Particularly encouraging is the result for low contrast penetration as this is a quick and simple measurement to make and can be performed with many different test objects, thus enabling 'in-the-field' checks.

  14. The design and characterization of an ultrasound phased array suitable for deep tissue hyperthermia.

    PubMed

    Aitkenhead, Adam H; Mills, John A; Wilson, Adrian J

    2008-11-01

    In this paper we describe the design and evaluation of a planar phased-array ultrasound transducer suitable for producing localized hyperthermia in solid tumors deep within the body. Simulation using a customized version of Ultrasim has been used to determine the relationship between the size and position of the focus and parameters of the array. These parameters include the overall size of the array and the size, shape and distribution of the individual elements. A 15-element prototype array has been constructed using the results of the simulation. Beam profile measurements on this transducer made in an acoustic tank were compared with the beam profile predicted by simulation. The results showed good agreement in the shape of the focal region, but with the focus closer to the surface of the physical transducer when compared with the simulation and with small high-intensity areas between the surface of the transducer and the focus in the measured profile. A sensitivity analysis using a simulated factorial experiment indicated that the presence of a secondary vibrational mode within the elements of the array was the principal cause for both the shift in the position of the focus and for the unwanted maxima close to the surface of the array. The results also showed that the array was tolerant of a large variation in output intensity of the individual elements in the array in producing a focal region. Extrapolation of the results obtained in this study indicate that an array of 60 elements, based on the design described, driven by 550 V peak-to-peak pulses would be capable of producing a peak focal intensity of 50 Wcm(-2) at a depth of 60 mm in tissue, which would be appropriate for hyperthermia used as an adjunct to radiotherapy or chemotherapy.

  15. A random phased array device for delivery of high intensity focused ultrasound.

    PubMed

    Hand, J W; Shaw, A; Sadhoo, N; Rajagopal, S; Dickinson, R J; Gavrilov, L R

    2009-10-07

    Randomized phased arrays can offer electronic steering of a single focus and simultaneous multiple foci concomitant with low levels of secondary maxima and are potentially useful as sources of high intensity focused ultrasound (HIFU). This work describes laboratory testing of a 1 MHz random phased array consisting of 254 elements on a spherical shell of radius of curvature 130 mm and diameter 170 mm. Acoustic output power and efficiency are measured for a range of input electrical powers, and field distributions for various single- and multiple-focus conditions are evaluated by a novel technique using an infrared camera to provide rapid imaging of temperature changes on the surface of an absorbing target. Experimental results show that the array can steer a single focus laterally to at least +/-15 mm off axis and axially to more than +/-15 mm from the centre of curvature of the array and patterns of four and five simultaneous foci +/-10 mm laterally and axially whilst maintaining low intensity levels in secondary maxima away from the targeted area in good agreement with linear theoretical predictions. Experiments in which pork meat was thermally ablated indicate that contiguous lesions several cm(3) in volume can be produced using the patterns of multiple foci.

  16. Design and characterization of dual-curvature 1.5-dimensional high-intensity focused ultrasound phased-array transducer.

    PubMed

    Chen, Gin-Shin; Lin, Che-Yu; Jeong, Jong Seob; Cannata, Jonathan M; Lin, Win-Li; Chang, Hsu; Shung, K Kirk

    2012-01-01

    A dual-curvature focused ultrasound phased-array transducer with a symmetric control has been developed for noninvasive ablative treatment of tumors. The 1.5-D array was constructed in-house and the electro-acoustic conversion efficiency was measured to be approximately 65%. In vitro experiments demonstrated that the array uses 256 independent elements to achieve 2-D wide-range high-intensity electronic focusing.

  17. [Genetic algorithm application to multi-focus patterns of 256-element phased array for focused ultrasound surgery].

    PubMed

    Xu, Feng; Wan, Mingxi; Lu, Mingzhu

    2008-10-01

    The genetic optimal algorithm and sound field calculation approach for the spherical-section phased array are presented in this paper. The in-house manufactured 256-element phased array focused ultrasound surgery system is briefly described. The on-axis single focus and off-axis single focus are simulated along with the axis-symmetric six-focus patter and the axis-asymmetric four-focus pattern using a 256-element phased array and the genetic optimal algorithm and sound field calculation approach. The experimental results of the described 256-element phased array focused ultrasound surgery system acting on organic glass and phantom are also analyzed. The results of the simulations and experiments confirm the applicability of the genetic algorithm and field calculation approaches in accurately steering three dimensional foci and focus.

  18. Comparison of two methods of treatment for intraluminal thermal ablation using an ultrasound cylindrical phased array.

    PubMed

    Melodelima, David; Prat, Frédéric; Birer, Alain; Theillère, Yves; Cathignol, Dominique

    2004-04-01

    Intraluminal (within the alimentary tract) thermal surgery has been shown to be a useful therapeutic option when extracorporeal focused ultrasound applicators cannot be used since their beam may not reach the target site. If plane transducers are used for the treatment of alimentary tract tumours, the applicator must be rotated in order to generate a cylindrical volume of necrosis. However, rotating these applicators and controlling their shooting direction presents technical difficulties. If tubular transducers are used it is difficult to treat arbitrary angles with a large therapeutic length. To solve these difficulties, the feasibility of an ultrasound phased array applicator has been evaluated using a cylindrical prototype (outer diameter 10.6 mm), which is composed of 16 elementary transducers working at 4.55 MHz and arranged on a quarter of the cylinder. Using this applicator it is possible to generate plane or cylindrical waves. Plane waves were generated by exciting eight successive elements of the array with appropriate delay times. The exposure direction was changed by exciting a different set of eight elements. In this way, the ultrasound beam was electronically rotated through the tissues. Cylindrical waves were generated by exciting several transducers without delay times. Imaging was provided using a miniature echographic probe. Ex vivo experiments were carried out in pig liver to compare two approaches of treatment. The first consisted of generating successive plane waves separated from each other by a 6 degrees angle. The second one consisted of exciting all the 16 elements without delay times. In the two cases, the lesions were well-defined and occupied a quarter of cylinder. In both sets of experiments, the sonication time and the intensity were 20 s and 17 W/cm(2), respectively. In the first case, the depth was up to 17 mm compared to 6 mm in the second case.

  19. Thermal therapy for breast tumors by using a cylindrical ultrasound phased array with multifocus pattern scanning: a preliminary numerical study.

    PubMed

    Ho, Cheng-Shiao; Ju, Kuen-Cheng; Cheng, Tze-Yuan; Chen, Yung-Yaw; Lin, Win-Li

    2007-08-07

    The purpose of this study is to investigate the feasibility of using a 1 MHz cylindrical ultrasound phased array with multifocus pattern scanning to produce uniform heating for breast tumor thermal therapy. The breast was submerged in water and surrounded by the cylindrical ultrasound phased array. A multifocus pattern was generated and electrically scanned by the phased array to enlarge the treatment lesion in single heating. To prevent overheating normal tissues, a large planning target volume (PTV) would be divided into several planes with several subunits on each plane and sequentially treated with a cooling phase between two successive heatings of the subunit. Heating results for different target temperatures (T(tgt)), blood perfusion rates and sizes of the PTV have been studied. Furthermore, a superficial breast tumor with different water temperatures was also studied. Results indicated that a higher target temperature would produce a slightly larger thermal lesion, and a higher blood perfusion rate would not affect the heating lesion size but increase the heating time significantly. The acoustic power deposition and temperature elevations in ribs can be minimized by orienting the acoustic beam from the ultrasound phased array approximately parallel to the ribs. In addition, a large acoustic window on the convex-shaped breast surface for the proposed ultrasound phased array and the cooling effect of water would prevent the skin overheating for the production of a lesion at any desired location. This study demonstrated that the proposed cylindrical ultrasound phased array can provide effective heating for breast tumor thermal therapy without overheating the skin and ribs within a reasonable treatment time.

  20. The feasibility of MRI-guided whole prostate ablation with a linear aperiodic intracavitary ultrasound phased array.

    PubMed

    Sokka, S D; Hynynen, K H

    2000-11-01

    Over the past decade, numerous minimally invasive thermal procedures have been investigated to treat benign prostate hyperplasia and prostate cancer. Of these methods, ultrasound has shown considerable promise due to its ability to produce more precise and deeper thermal foci. In this study, a linear, transrectal ultrasound phased array capable of ablating large tissue volumes was fabricated and evaluated. The device was designed to be compatible for use with MRI guidance and thermometry. The intracavitary applicator increases treatable tissue volume by using an ultrasonic motor to provide a mechanical rotation angle of up to 100 degrees to a 62-element 1D ultrasound array. An aperiodic array geometry was used to reduce grating lobes. In addition, a specially designed Kapton interconnect was used to reduce cable crosstalk and hence also improve the acoustic efficiency of the array. MRI-guided in vivo and ex vivo experiments were performed to verify the array's large-volume ablative capabilities. Ex vivo bovine experiments were performed to assess the focusing range of the applicator. The array generated foci in a 3 cm (2 to 5 cm from the array surface along the axis normal to the array) by 5.5 cm (along the long axis of the array) by 6 cm (along the transverse axis of the array at a depth of 4 cm) volume. In vivo rabbit thigh experiments were performed to evaluate the lesion producing capabilities in perfused tissue. The array generated 3 cm x 2 cm x 2 cm lesions with 8 to 12 half-minute sonications equally spaced in the volume. The results indicate that transrectal ultrasound coagulation of the whole prostate is feasible with the developed device.

  1. The feasibility of MRI-guided whole prostate ablation with a linear aperiodic intracavitary ultrasound phased array

    NASA Astrophysics Data System (ADS)

    Sokka, S. D.; Hynynen, K. H.

    2000-11-01

    Over the past decade, numerous minimally invasive thermal procedures have been investigated to treat benign prostate hyperplasia and prostate cancer. Of these methods, ultrasound has shown considerable promise due to its ability to produce more precise and deeper thermal foci. In this study, a linear, transrectal ultrasound phased array capable of ablating large tissue volumes was fabricated and evaluated. The device was designed to be compatible for use with MRI guidance and thermometry. The intracavitary applicator increases treatable tissue volume by using an ultrasonic motor to provide a mechanical rotation angle of up to 100° to a 62-element 1D ultrasound array. An aperiodic array geometry was used to reduce grating lobes. In addition, a specially designed Kapton interconnect was used to reduce cable crosstalk and hence also improve the acoustic efficiency of the array. MRI-guided in vivo and ex vivo experiments were performed to verify the array's large-volume ablative capabilities. Ex vivo bovine experiments were performed to assess the focusing range of the applicator. The array generated foci in a 3 cm (2 to 5 cm from the array surface along the axis normal to the array) by 5.5 cm (along the long axis of the array) by 6 cm (along the transverse axis of the array at a depth of 4 cm) volume. In vivo rabbit thigh experiments were performed to evaluate the lesion-producing capabilities in perfused tissue. The array generated 3 cm × 2 cm × 2 cm lesions with 8 to 12 half-minute sonications equally spaced in the volume. The results indicate that transrectal ultrasound coagulation of the whole prostate is feasible with the developed device.

  2. Comparison of 3-D synthetic aperture phased-array ultrasound imaging and parallel beamforming.

    PubMed

    Rasmussen, Morten Fischer; Jensen, Jørgen Arendt

    2014-10-01

    This paper demonstrates that synthetic aperture imaging (SAI) can be used to achieve real-time 3-D ultrasound phased-array imaging. It investigates whether SAI increases the image quality compared with the parallel beamforming (PB) technique for real-time 3-D imaging. Data are obtained using both simulations and measurements with an ultrasound research scanner and a commercially available 3.5- MHz 1024-element 2-D transducer array. To limit the probe cable thickness, 256 active elements are used in transmit and receive for both techniques. The two imaging techniques were designed for cardiac imaging, which requires sequences designed for imaging down to 15 cm of depth and a frame rate of at least 20 Hz. The imaging quality of the two techniques is investigated through simulations as a function of depth and angle. SAI improved the full-width at half-maximum (FWHM) at low steering angles by 35%, and the 20-dB cystic resolution by up to 62%. The FWHM of the measured line spread function (LSF) at 80 mm depth showed a difference of 20% in favor of SAI. SAI reduced the cyst radius at 60 mm depth by 39% in measurements. SAI improved the contrast-to-noise ratio measured on anechoic cysts embedded in a tissue-mimicking material by 29% at 70 mm depth. The estimated penetration depth on the same tissue-mimicking phantom shows that SAI increased the penetration by 24% compared with PB. Neither SAI nor PB achieved the design goal of 15 cm penetration depth. This is likely due to the limited transducer surface area and a low SNR of the experimental scanner used.

  3. Realtime Control of Multiple-focus Phased Array Heating Patterns Based on Noninvasive Ultrasound Thermography

    PubMed Central

    Casper, Andrew; Liu, Dalong; Ebbini, Emad S.

    2011-01-01

    A system for the realtime generation and control of multiple-focus ultrasound phased-array heating patterns is presented. The system employs a 1-MHz, 64-element array and driving electronics capable of fine spatial and temporal control of the heating pattern. The driver is integrated with a realtime 2D temperature imaging system implemented on a commercial scanner. The coordinates of the temperature control points are defined on B-mode guidance images from the scanner, together with the temperature set points and controller parameters. The temperature at each point is controlled by an independent proportional, integral, and derivative (PID) controller that determines the focal intensity at that point. Optimal multiple-focus synthesis is applied to generate the desired heating pattern at the control points. The controller dynamically reallocates the power available among the foci from the shared power supply upon reaching the desired temperature at each control point. Furthermore, anti-windup compensation is implemented at each control point to improve the system dynamics. In vitro experiments in tissue-mimicking phantom demonstrate the robustness of the controllers for short (2 – 5 sec) and longer multiple-focus HIFU exposures. Thermocouple measurements in the vicinity of the control points confirm the dynamics of the temperature variations obtained through noninvasive feedback. PMID:21768037

  4. Focusing of high-intensity ultrasound through the rib cage using a therapeutic random phased array.

    PubMed

    Bobkova, Svetlana; Gavrilov, Leonid; Khokhlova, Vera; Shaw, Adam; Hand, Jeffrey

    2010-06-01

    A method for focusing high-intensity ultrasound (HIFU) through a rib cage that aims to minimize heating of the ribs while maintaining high intensities at the focus (or foci) was proposed and tested theoretically and experimentally. Two approaches, one based on geometric acoustics and the other accounting for diffraction effects associated with propagation through the rib cage, were investigated theoretically for idealized source conditions. It is shown that for an idealized radiator, the diffraction approach provides a 23% gain in peak intensity and results in significantly less power losses on the ribs (1% vs. 7.5% of the irradiated power) compared with the geometric one. A 2-D 1-MHz phased array with 254 randomly distributed elements, tissue-mimicking phantoms and samples of porcine rib cages are used in experiments; the geometric approach is used to configure how the array is driven. Intensity distributions are measured in the plane of the ribs and in the focal plane using an infrared camera. Theoretical and experimental results show that it is possible to provide adequate focusing through the ribs without overheating them for a single focus and several foci, including steering at +/- 10-15 mm off and +/- 20 mm along the array axis. Focus splitting caused by the periodic spatial structure of ribs is demonstrated both in simulations and experiments; the parameters of splitting are quantified. The ability to produce thermal lesions with a split focal pattern in ex vivo porcine tissue placed beyond the rib phantom is also demonstrated. The results suggest that the method is potentially useful for clinical applications of HIFU, for which the rib cage lies between the transducer(s) and the targeted tissue.

  5. Focusing of high intensity ultrasound through the rib cage using a therapeutic random phased array

    PubMed Central

    Bobkova, Svetlana; Gavrilov, Leonid; Khokhlova, Vera; Shaw, Adam; Hand, Jeffrey; #, ||

    2010-01-01

    A method for focusing high intensity ultrasound through a rib cage that aims to minimize heating of the ribs whilst maintaining high intensities at the focus (or foci) is proposed and tested theoretically and experimentally. Two approaches, one based on geometric acoustics and the other accounting for diffraction effects associated with propagation through the rib cage, are investigated theoretically for idealized source conditions. It is shown that for an idealized radiator the diffraction approach provides a 23% gain in peak intensity and results in significantly less power losses on the ribs (1% versus 7.5% of the irradiated power) compared with the geometric one. A 2D 1-MHz phased array with 254 randomly distributed elements, tissue mimicking phantoms, and samples of porcine rib cages are used in experiments; the geometric approach is used to configure how the array is driven. Intensity distributions are measured in the plane of the ribs and in the focal plane using an infra-red camera. Theoretical and experimental results show that it is possible to provide adequate focusing through the ribs without overheating them for a single focus and several foci, including steering at ± 10–15 mm off and ± 20 mm along the array axis. Focus splitting due to the periodic spatial structure of ribs is demonstrated both in simulations and experiments; the parameters of splitting are quantified. The ability to produce thermal lesions with a split focal pattern in ex vivo porcine tissue placed beyond the rib phantom is also demonstrated. The results suggest that the method is potentially useful for clinical applications of HIFU for which the rib cage lies between the transducer(s) and the targeted tissue. PMID:20510186

  6. An ultrasound cylindrical phased array for deep heating in the breast: theoretical design using heterogeneous models.

    PubMed

    Bakker, J F; Paulides, M M; Obdeijn, I M; van Rhoon, G C; van Dongen, K W A

    2009-05-21

    The objective of this theoretical study is to design an ultrasound (US) cylindrical phased array that can be used for hyperthermia (40-44 degrees C) treatment of tumours in the intact breast. Simultaneously, we characterize the influence of acoustic and thermal heterogeneities on the specific absorption rate (SAR) and temperature patterns to determine the necessity of using heterogeneous models for a US applicator design and treatment planning. Cylindrical configurations of monopole transducers are studied on their ability to generate interference patterns that can be steered electronically to the location of the target region. Hereto, design parameters such as frequency, number of transducers per ring, ring distance and number of rings are optimized to obtain a small primary focus, while suppressing secondary foci. The models account for local heterogeneities in both acoustic (wave velocity and absorption) and thermal (blood perfusion rate, heat capacity and conductivity) tissue properties. We used breast models with a central tumour (30x20x38 mm3) and an artificial thorax tumour (sphere with a radius of 25 mm) to test the design. Simulations predict that a US cylindrical phased array, consisting of six rings with 32 transducers per ring, a radius of 75 mm and 66 mm distance between the first and sixth transducer ring, operating at a frequency of 100 kHz, can be used to obtain 44 degrees C in the centre of tumours located anywhere in the intact breast. The dimensions of the volumes enclosed by the 41 degrees C iso-temperature are 19x19x21 mm3 and 21x21x32 mm3 for the central and the thorax tumours, respectively. It is demonstrated that acoustic and thermal heterogeneities do not disturb the SAR and temperature patterns.

  7. Development of a 20-MHz wide-bandwidth PMN-PT single crystal phased-array ultrasound transducer.

    PubMed

    Wong, Chi-Man; Chen, Yan; Luo, Haosu; Dai, Jiyan; Lam, Kwok-Ho; Chan, Helen Lai-Wa

    2017-01-01

    In this study, a 20-MHz 64-element phased-array ultrasound transducer with a one-wavelength pitch is developed using a PMN-30%PT single crystal and double-matching layer scheme. High piezoelectric (d33>1000pC/N) and electromechanical coupling (k33>0.8) properties of the single crystal with an optimized fabrication process involving the photolithography technique have been demonstrated to be suitable for wide-bandwidth (⩾70%) and high-sensitivity (insertion loss ⩽30dB) phased-array transducer application. A -6dBbandwidth of 91% and an insertion loss of 29dBfor the 20-MHz 64-element phased-array transducer were achieved. This result shows that the bandwidth is improved comparing with the investigated high-frequency (⩾20MHz) ultrasound transducers using piezoelectric ceramic and single crystal materials. It shows that this phased-array transducer has potential to improve the resolution of biomedical imaging, theoretically. Based on the hypothesis of resolution improvement, this phased-array transducer is capable for small animal (i.e. mouse and zebrafish) studies.

  8. Basic study on ultrasonic monitoring using 1.5-dimensional ultrasound phased array for ultrasound-guided high-intensity focused ultrasound treatment

    NASA Astrophysics Data System (ADS)

    Takagi, Ryo; Iwasaki, Ryosuke; Tomiyasu, Kentaro; Yoshizawa, Shin; Umemura, Shin-ichiro

    2017-07-01

    We have been studying a real-time detection method for tissue changes induced by high-intensity focused ultrasound (HIFU) treatment using ultrasonic RF signals. It has been difficult to track the target region when the tissue to be treated deviates from the imaging plane along the elevation axis of the probe. In this study, a new 1.5-dimensional (1.5D) prototype phased array probe consisting of transducer elements along both the lateral and elevation axes was developed to track tissue motion along the elevation axis of the probe, and the elevational displacement range where the tracking is effective was investigated. The complex cross-correlation coefficient based on a block matching algorithm was applied to 2.5D volumetric RF images acquired by the 1.5D probe and the displacement vector along the elevation axis was calculated. From the results, it was found that the effective tracking range using this prototype probe was up to 3 mm, about 3 times that of a conventional 1D imaging probe. The proposed 1.5D phased array probe has the potential to track target tissue with intrafractional motion.

  9. Feasibility of using lateral mode coupling method for a large scale ultrasound phased array for noninvasive transcranial therapy.

    PubMed

    Song, Junho; Hynynen, Kullervo

    2010-01-01

    A hemispherical-focused, ultrasound phased array was designed and fabricated using 1372 cylindrical piezoelectric transducers that utilize lateral coupling for noninvasive transcranial therapy. The cylindrical transducers allowed the electrical impedance to be reduced by at least an order of magnitude, such that effective operation could be achieved without electronic matching circuits. In addition, the transducer elements generated the maximum acoustic average surface intensity of 27 W/cm(2). The array, driven at the low (306-kHz) or high frequency (840-kHz), achieved excellent focusing through an ex vivo human skull and an adequate beam steering range for clinical brain treatments. It could electronically steer the ultrasound beam over cylindrical volumes of 100-mm in diameter and 60-mm in height at 306 kHz, and 30-mm in diameter and 30-mm in height at 840 kHz. A scanning laser vibrometer was used to investigate the radial and length mode vibrations of the element. The maximum pressure amplitudes through the skull at the geometric focus were predicted to be 5.5 MPa at 306 kHz and 3.7 MPa at 840 kHz for RF power of 1 W on each element. This is the first study demonstrating the feasibility of using cylindrical transducer elements and lateral coupling in construction of ultrasound phased arrays.

  10. Feasibility of Using Lateral Mode Coupling Method for a Large Scale Ultrasound Phased Array for Noninvasive Transcranial Therapy

    PubMed Central

    Song, Junho; Hynynen, Kullervo

    2009-01-01

    A hemispherical-focused, ultrasound phased array was designed and fabricated using 1372 cylindrical piezoelectric transducers that utilize lateral coupling for noninvasive transcranial therapy. The cylindrical transducers allowed the electrical impedance to be reduced by at least an order of magnitude, such that effective operation could be achieved without electronic matching circuits. In addition, the transducer elements generated the maximum acoustic average surface intensity of 27 W/cm2. The array, driven at the low (306 kHz) or high frequency (840 kHz), achieved excellent focusing through an ex vivo human skull and an adequate beam steering range for clinical brain treatments. It could electronically steer the ultrasound beam over cylindrical volumes of 100 mm in diameter and 60 mm in height at 306 kHz, and 30-mm in diameter and 30-mm in height at 840 kHz. A scanning laser vibrometer was used to investigate the radial and length mode vibrations of the element. The maximum pressure amplitudes through the skull at the geometric focus were predicted to be 5.5 MPa at 306 kHz and 3.7 MPa at 840 kHz for RF power of 1 W on each element. This is the first study demonstrating the feasibility of using cylindrical transducer elements and lateral coupling in construction of ultrasound phased arrays. PMID:19695987

  11. A 63 element 1.75 dimensional ultrasound phased array for the treatment of benign prostatic hyperplasia.

    PubMed

    Saleh, Khaldon Y; Smith, Nadine Barrie

    2005-06-17

    Prostate cancer and benign prostatic hyperplasia are very common diseases in older American men, thus having a reliable treatment modality for both diseases is of great importance. The currently used treating options, mainly surgical ones, have numerous complications, which include the many side effects that accompany such procedures, besides the invasive nature of such techniques. Focused ultrasound is a relatively new treating modality that is showing promising results in treating prostate cancer and benign prostatic hyperplasia. Thus this technique is gaining more attention in the past decade as a non-invasive method to treat both diseases. In this paper, the design, construction and evaluation of a 1.75 dimensional ultrasound phased array to be used for treating prostate cancer and benign prostatic hyperplasia is presented. With this array, the position of the focus can be controlled by changing the electrical power and phase to the individual elements for electronically focusing and steering in a three dimensional volume. The array was designed with a maximum steering angle of +/- 13.5 degrees in the transverse direction and a maximum depth of penetration of 11 cm, which allows the treatment of large prostates. The transducer piezoelectric ceramic, matching layers and cable impedance have been designed for maximum power transfer to tissue. To verify the capability of the transducer for focusing and steering, exposimetry was performed and the results correlated well with the calculated field. Ex vivo experiments using bovine tissue were performed with various lesion sizes and indicated the capability of the transducer to ablate tissue using short sonications. A 1.75 dimensional array, that overcame the drawbacks associated with one-dimensional arrays, has been designed, built and successfully tested. Design issues, such as cable and ceramic capacitances, were taken into account when designing this array. The final prototype overcame also the problem of

  12. A 63 element 1.75 dimensional ultrasound phased array for the treatment of benign prostatic hyperplasia

    PubMed Central

    Saleh, Khaldon Y; Smith, Nadine Barrie

    2005-01-01

    Background Prostate cancer and benign prostatic hyperplasia are very common diseases in older American men, thus having a reliable treatment modality for both diseases is of great importance. The currently used treating options, mainly surgical ones, have numerous complications, which include the many side effects that accompany such procedures, besides the invasive nature of such techniques. Focused ultrasound is a relatively new treating modality that is showing promising results in treating prostate cancer and benign prostatic hyperplasia. Thus this technique is gaining more attention in the past decade as a non-invasive method to treat both diseases. Methods In this paper, the design, construction and evaluation of a 1.75 dimensional ultrasound phased array to be used for treating prostate cancer and benign prostatic hyperplasia is presented. With this array, the position of the focus can be controlled by changing the electrical power and phase to the individual elements for electronically focusing and steering in a three dimensional volume. The array was designed with a maximum steering angle of ± 13.5° in the transverse direction and a maximum depth of penetration of 11 cm, which allows the treatment of large prostates. The transducer piezoelectric ceramic, matching layers and cable impedance have been designed for maximum power transfer to tissue. Results To verify the capability of the transducer for focusing and steering, exposimetry was performed and the results correlated well with the calculated field. Ex vivo experiments using bovine tissue were performed with various lesion sizes and indicated the capability of the transducer to ablate tissue using short sonications. Conclusion A 1.75 dimensional array, that overcame the drawbacks associated with one-dimensional arrays, has been designed, built and successfully tested. Design issues, such as cable and ceramic capacitances, were taken into account when designing this array. The final prototype

  13. Investigation of optimal method for inducing harmonic motion in tissue using a linear ultrasound phased array--a simulation study.

    PubMed

    Heikkilä, Janne; Hynynen, Kullervo

    2006-04-01

    Many noninvasive ultrasound techniques have been developed to explore mechanical properties of soft tissues. One of these methods, Localized Harmonic Motion Imaging (LHMI), has been proposed to be used for ultrasound surgery monitoring. In LHMI, dynamic ultrasound radiation-force stimulation induces displacements in a target that can be measured using pulse-echo imaging and used to estimate the elastic properties of the target. In this initial, simulation study, the use of a one-dimensional phased array is explored for the induction of the tissue motion. The study compares three different dual-frequency and amplitude-modulated single-frequency methods for the inducing tissue motion. Simulations were computed in a homogeneous soft-tissue volume. The Rayleigh integral was used in the simulations of the ultrasound fields and the tissue displacements were computed using a finite-element method (FEM). The simulations showed that amplitude-modulated sonication using a single frequency produced the largest vibration amplitude of the target tissue. These simulations demonstrate that the properties of the tissue motion are highly dependent on the sonication method and that it is important to consider the full three-dimensional distribution of the ultrasound field for controlling the induction of tissue motion.

  14. Design and evaluation of a 63 element 1.75-dimensional ultrasound phased array for treating benign prostatic hyperplasia

    NASA Astrophysics Data System (ADS)

    Saleh, Khaldon Y.; Smith, Nadine B.

    2003-10-01

    Focused ultrasound surgery (FUS) is a clinical method for treating benign prostatic hyperplasia (BPH) in which tissue is noninvasively necrosed by elevating the temperature at the focal point above 60°C using short sonications. With 1.75-dimensional (1.75-D) arrays, the power and phase to the individual elements can be controlled electronically for focusing and steering. This research describes the design, construction and evaluation of a 1.75-D ultrasound phased array to be used in the treatment of benign prostatic hyperplasia. The array was designed with a steering angle of +/-13.5 deg in the transverse direction, and can move the focus in three parallel planes in the longitudinal direction with a relatively large focus size. A piezoelectric ceramic (PZT-8) was used as the material of the transducer and two matching layers were built for maximum acoustic power transmission to tissue. To verify the capability of the transducer for focusing and steering, exposimetry was performed and the results correlated well with the calculated fields. In vivo experiments were performed to verify the capability of the transducer to ablate tissue using short sonications. [Work supported by the Whitaker Foundation and the Department of Defense Congressionally Directed Medical Prostate Cancer Research Program.

  15. An 11-channel radio frequency phased array coil for magnetic resonance guided high-intensity focused ultrasound of the breast.

    PubMed

    Minalga, E; Payne, A; Merrill, R; Todd, N; Vijayakumar, S; Kholmovski, E; Parker, D L; Hadley, J R

    2013-01-01

    In this study, a radio frequency phased array coil was built to image the breast in conjunction with a magnetic resonance guided high-intensity focused ultrasound (MRgHIFU) device designed specifically to treat the breast in a treatment cylinder with reduced water volume. The MRgHIFU breast coil was comprised of a 10-channel phased array coil placed around an MRgHIFU treatment cylinder where nearest-neighbor decoupling was achieved with capacitive decoupling in a shared leg. In addition a single loop coil was placed at the chest wall making a total of 11 channels. The radio frequency coil array design presented in this work was chosen based on ease of implementation, increased visualization into the treatment cylinder, image reconstruction speed, temporal resolution, and resulting signal-to-noise ratio profiles. This work presents a dedicated 11-channel coil for imaging of the breast tissue in the MRgHIFU setup without obstruction of the ultrasound beam and, specifically, compares its performance in signal-to-noise, overall imaging time, and temperature measurement accuracy to that of the standard single chest-loop coil typically used in breast MRgHIFU.

  16. Design and experimental evaluations of a low-frequency hemispherical ultrasound phased-array system for transcranial blood-brain barrier disruption.

    PubMed

    Liu, Hao-Li; Chen, Heng-Wen; Kuo, Zhen-Hao; Huang, Wen-Cheng

    2008-10-01

    The purpose of this paper is to demonstrate a prototype design of a low-frequency multiple-channel hemispherical focused-ultrasound phased-array system for transcranial disruption of the blood-brain barrier (BBB). A 32-channel ultrasound driving system tunable in the frequency range from 200 to 400 kHz was designed for producing a suitable ultrasound output for BBB disruption. The driving system includes a microcontroller/field-programmable gate-array-based control kernel with multiple-channel driving circuits implemented by a high-voltage switching/LC-resonance/impedance-matching circuit module. Three hemispherical phased arrays comprising 22, 31, and 80 elements were fabricated and tested. The pressure distributions at the geometric center and at off-center positions were tested experimentally. The focal performance of the different hemispherical arrays was also evaluated theoretically. The results showed that the developed phased-array system can successfully drive the hemispherical array with multiple-channel ultrasound signals with independent phase control at 8-bit resolution. Good focusing abilities were evident both at the geometric center and at specific off-center target positions. Preliminary animal experiments show that the BBB in rat can be locally disrupted successfully. The system will serve as a reference platform for developing a focused-ultrasound system for clinical use in brain drug delivery applications.

  17. Focused beam control for ultrasound surgery with spherical-section phased array: sound field calculation and genetic optimization algorithm.

    PubMed

    Lu, Mingzhu; Wan, Mingxi; Xu, Feng; Wang, Xiaodong; Zhong, Hui

    2005-08-01

    This study aims at a sound field calculation for the spherical-section phased array and an optimization algorithm for the focus patterns of phased array ultrasound surgery. An efficient field calculation formula represented as an explicit expression is derived by the strategies of projection and binomial expansion. An optimization algorithm based on genetic algorithm is constructed by the suitable fitness function and the selection strategies. The simulation results of 256-element spherical-section phased array show the capability of controlling focus accurately and effectively with the combined method made up of the explicit expression method and the genetic optimization algorithm. The simulation results of single focus, multiple foci, on-axial focus, and off-axial focus further convince the feasibility of three-dimensional (3-D) focus steering with excellent acoustic performances. A single focus with the focus dimension of 1.25 mm x 1.25 mm x 7 mm and with the intensity of 6080 W/cm2 is formed. The multiple-focus pattern can enlarge the treatment volume 22 times larger than that of single focus with a sonication. In addition, a comparison between the explicit expression approach and the point source approach testifies to the applicability of the explicit expression approach. The experiment and simulation results of 16-element array actually confirm the feasibility of the combined method.

  18. 64-element intraluminal ultrasound cylindrical phased array for transesophageal thermal ablation under fast MR temperature mapping: an ex vivo study.

    PubMed

    Melodelima, D; Salomir, R; Mougenot, C; Moonen, C; Cathignol, D

    2006-08-01

    This work was undertaken to investigate the feasibility of using a cylindrical phased array for transoesophaeal thermal ablation under magnetic resonance (MR) imaging guidance. Sixty-four transducers (0.45 mm wide by 15 mm tall), operating at 4.6 MHz, were spread around the periphery of a 10.6-mm-diam cylinder. The head of the applicator was covered with a 65-microm thick latex balloon attached using watertight seals. This envelope was inflated with degassed water to provide acoustic coupling between the transducer and the tissues. The underlying operating principle of this applicator is to rotate a plane ultrasound beam electronically. For this purpose, eight adjacent transducers were excited with appropriate delay times so as to generate a plane wave. The exposure direction was changed by exciting a different set of eight elements. Ex vivo experiments conducted on 47 samples of pig liver under MR temperature monitoring demonstrated the ability of this applicator to generate cylindrical or sector-based coagulation necroses at depths up to 19 mm with excellent angular precision by applying 20 W/cm2. MR thermometry was performed in "real-time" with segmented echo-planar imaging gradient echo sequences. The temporal resolution was approximately 3 s/ image. The average value for the temperature baseline in liver tissue close to the applicator was 0.3 degrees C (+/- 0.6 degrees C). The thermal dose delivered in tissues was computed on-line during temperature imaging. Excellent MR compatibility was demonstrated, all MR acquisitions were performed without susceptibility artifacts or radio-frequency interferences with the ultrasound device. Thermal lesions identified on post-treatment follow up showed good correlation with online MR thermometry data. The individual differences between measurements performed visually and using MRI thermal dose maps were about 11% of volume. This study demonstrated the feasibility of thermal ablation using a phased array intraluminal

  19. High-intensity focused ultrasound with large scale spherical phased array for the ablation of deep tumors.

    PubMed

    Ji, Xiang; Bai, Jing-feng; Shen, Guo-feng; Chen, Ya-zhu

    2009-09-01

    Under some circumstances surgical resection is feasible in a low percentage for the treatment of deep tumors. Nevertheless, high-intensity focused ultrasound (HIFU) is beginning to offer a potential noninvasive alternative to conventional therapies for the treatment of deep tumors. In our previous study, a large scale spherical HIFU-phased array was developed to ablate deep tumors. In the current study, taking into account the required focal depth and maximum acoustic power output, 90 identical circular PZT-8 elements (diameter =1.4 cm and frequency=1 MHz) were mounted on a spherical shell with a radius of curvature of 18 cm and a diameter of 21 cm. With the developed array, computer simulations and ex vivo experiments were carried out. The simulation results theoretically demonstrate the ability of the array to focus and steer in the specified volume (a 2 cmx2 cmx3 cm volume) at the focal depth of 15 to 18 cm. Ex vivo experiment results also verify the capability of the developed array to ablate deep target tissue by either moving single focal point or generating multiple foci simultaneously.

  20. A multi-frequency sparse hemispherical ultrasound phased array for microbubble-mediated transcranial therapy and simultaneous cavitation mapping

    NASA Astrophysics Data System (ADS)

    Deng, Lulu; O'Reilly, Meaghan A.; Jones, Ryan M.; An, Ran; Hynynen, Kullervo

    2016-12-01

    Focused ultrasound (FUS) phased arrays show promise for non-invasive brain therapy. However, the majority of them are limited to a single transmit/receive frequency and therefore lack the versatility to expose and monitor the treatment volume. Multi-frequency arrays could offer variable transmit focal sizes under a fixed aperture, and detect different spectral content on receive for imaging purposes. Here, a three-frequency (306, 612, and 1224 kHz) sparse hemispherical ultrasound phased array (31.8 cm aperture; 128 transducer modules) was constructed and evaluated for microbubble-mediated transcranial therapy and simultaneous cavitation mapping. The array is able to perform effective electronic beam steering over a volume spanning (-40, 40) and (-30, 50) mm in the lateral and axial directions, respectively. The focal size at the geometric center is approximately 0.9 (2.1) mm, 1.7 (3.9) mm, and 3.1 (6.5) mm in lateral (axial) pressure full width at half maximum (FWHM) at 1224, 612, and 306 kHz, respectively. The array was also found capable of dual-frequency excitation and simultaneous multi-foci sonication, which enables the future exploration of more complex exposure strategies. Passive acoustic mapping of dilute microbubble clouds demonstrated that the point spread function of the receive array has a lateral (axial) intensity FWHM between 0.8-3.5 mm (1.7-11.7 mm) over a volume spanning (-25, 25) mm in both the lateral and axial directions, depending on the transmit/receive frequency combination and the imaging location. The device enabled both half and second harmonic imaging through the intact skull, which may be useful for improving the contrast-to-tissue ratio or imaging resolution, respectively. Preliminary in vivo experiments demonstrated the system’s ability to induce blood-brain barrier opening and simultaneously spatially map microbubble cavitation activity in a rat model. This work presents a tool to investigate optimal strategies for non

  1. A multi-frequency sparse hemispherical ultrasound phased array for microbubble-mediated transcranial therapy and simultaneous cavitation mapping.

    PubMed

    Deng, Lulu; O'Reilly, Meaghan A; Jones, Ryan M; An, Ran; Hynynen, Kullervo

    2016-12-21

    Focused ultrasound (FUS) phased arrays show promise for non-invasive brain therapy. However, the majority of them are limited to a single transmit/receive frequency and therefore lack the versatility to expose and monitor the treatment volume. Multi-frequency arrays could offer variable transmit focal sizes under a fixed aperture, and detect different spectral content on receive for imaging purposes. Here, a three-frequency (306, 612, and 1224 kHz) sparse hemispherical ultrasound phased array (31.8 cm aperture; 128 transducer modules) was constructed and evaluated for microbubble-mediated transcranial therapy and simultaneous cavitation mapping. The array is able to perform effective electronic beam steering over a volume spanning (-40, 40) and (-30, 50) mm in the lateral and axial directions, respectively. The focal size at the geometric center is approximately 0.9 (2.1) mm, 1.7 (3.9) mm, and 3.1 (6.5) mm in lateral (axial) pressure full width at half maximum (FWHM) at 1224, 612, and 306 kHz, respectively. The array was also found capable of dual-frequency excitation and simultaneous multi-foci sonication, which enables the future exploration of more complex exposure strategies. Passive acoustic mapping of dilute microbubble clouds demonstrated that the point spread function of the receive array has a lateral (axial) intensity FWHM between 0.8-3.5 mm (1.7-11.7 mm) over a volume spanning (-25, 25) mm in both the lateral and axial directions, depending on the transmit/receive frequency combination and the imaging location. The device enabled both half and second harmonic imaging through the intact skull, which may be useful for improving the contrast-to-tissue ratio or imaging resolution, respectively. Preliminary in vivo experiments demonstrated the system's ability to induce blood-brain barrier opening and simultaneously spatially map microbubble cavitation activity in a rat model. This work presents a tool to investigate optimal strategies for non

  2. Targeted hyperthermia in prostate with an MR-guided endorectal ultrasound phased array: patient specific modeling and preliminary experiments

    NASA Astrophysics Data System (ADS)

    Salgaonkar, Vasant A.; Prakash, Punit; Plata, Juan; Holbrook, Andrew; Rieke, Viola; Kurhanewicz, John; Hsu, I.-C.; Diederich, Chris J.

    2013-02-01

    Feasibility of hyperthermia delivery to the prostate with a commercially available MR-guided endorectal ultrasound (ERUS) phased array ablation system (ExAblate 2100, Insightec, LTD) was assessed through computer simulations and ex vivo experiments. The simulations included a 3D FEM-based biothermal model, and acoustic field calculations for the ExAblate phased array (2.3 MHz, 2.3x4.0 cm2) using the rectangular radiator method. Array beamforming strategies were investigated to deliver 30-min hyperthermia (<41 °C) to focal regions of prostate cancer, identified from MR images in representative patient cases. Constraints on power densities, sonication durations and switching speeds imposed by ExAblate hardware and software were incorporated in the models. T<41 °C was calculated in 14-19 cm3 for sonications with planar or diverging beam patterns at 0.9-1.2 W/cm2, and in 3-10 cm3 for curvilinear (cylindrical) or multifocus beam patterns at 1.5-3.3 W/cm2, potentially useful for treating focal disease in a single posterior quadrant. Preliminary experiments included beamformed sonications in tissue mimicking phantom material under MRI-based temperature monitoring at 3T (GRE TE=7.0 ms, TR=15 ms, BW=10.5 kHz, FOV=15 cm, matrix 128x128, FA=40°). MR-temperature rises of 2-6 °C were induced in a phantom with the ExAblate array, consistent with calculated values and lower power settings (~0.86 W/cm2, 3 min.). Conformable hyperthermia may be delivered by tailoring power deposition along the array length and angular expanse. MRgERUS HIFU systems can be controlled for continuous hyperthermia in prostate to augment radiotherapy and drug delivery. [FUS Foundation, NIH R01 122276, 111981].

  3. The role of acoustic nonlinearity in tissue heating behind the rib cage using high intensity focused ultrasound phased array

    PubMed Central

    Yuldashev, Petr V.; Shmeleva, Svetlana M.; Ilyin, Sergey A.; Sapozhnikov, Oleg A.; Gavrilov, Leonid R.; Khokhlova, Vera A.

    2013-01-01

    The goal of this study was to investigate theoretically the effects of nonlinear propagation in a high intensity focused ultrasound (HIFU) field produced by a therapeutic phased array and the resultant heating of tissue behind a rib cage. Three configurations of focusing were simulated: in water, in water with ribs in the beam path, and in water with ribs backed by a layer of soft tissue. The Westervelt equation was used to model the nonlinear HIFU field and a 1 MHz phased array consisting of 254 circular elements was used as a boundary condition to the model. The temperature rise in tissue was modelled using the bioheat equation, and thermally necrosed volumes were calculated using the thermal dose formulation. The shapes of lesions predicted by the modelling were compared with those previously obtained in in vitro experiments at low power sonications. Intensity levels at the face of the array elements that corresponded to formation of high amplitude shock fronts in the focal region were determined as 10 W·cm−2 in the free field in water and 40 W·cm−2 in the presence of ribs. It was shown that exposures with shocks provided a substantial increase in tissue heating, and its better spatial localization in the main focal region only. The relative effects of overheating ribs and splitting of the focus due to the periodic structure of the ribs were therefore reduced. These results suggest that utilizing nonlinear propagation and shock formation effects can be beneficial for inducing confined HIFU lesions when irradiating through obstructions such as ribs. Design of compact therapeutic arrays to provide maximum power outputs with lower intensity levels at the elements is necessary to achieve shock wave regimes for clinically relevant sonication depths in tissue. PMID:23528338

  4. An analysis of the origin of differences between measured and simulated fields produced by a 15-element ultrasound phased array.

    PubMed

    Aitkenhead, Adam H; Mills, John A; Wilson, Adrian J

    2010-03-01

    Modeling provides an attractive approach for the design of phased array ultrasound transducers for hyperthermia. However, measurements on physical transducers reveal differences from the idealized field profiles predicted by simulation. In this paper we report a method of analyzing the origins of these differences. The measured performance of a 15-element sparse phased array is described and compared with simulated fields calculated using the point source method. It highlighted two notable differences: First, that the focal region was located closer to the surface of the physical transducer than in the simulated fields; and second, that numerous intensity maxima were present between the surface of the transducer and the focal zone in the experimental data, but not in the simulated fields. We identified six factors that could potentially affect the field but were not taken into account by the default simulations, and we performed a sensitivity analysis on these: (i) Variation in the amplitude of the output from each element, (ii) the presence of square-wave harmonics in the drive signals, (iii) nonpistonlike vibration of elements, (iv) quantization of the applied phases, (v) errors in the spatial positioning of each element; and (vi) interelement cross-coupling. Both the independent impact of each factor and the interactions between multiple factors were analyzed by using a full-factorial experimental design composed of 64 (2(6)) simulations. The results indicated that nonpistonlike motion of elements is likely to be the primary cause of differences between the measured and modelled fields. Determination of the precise vibrational modes of elements in an array is complex and would require full finite element analysis. However, the simple vibrational mode considered within the present work, corresponding to the addition of a surface Rayleigh wave originating at the element center and propagating radially, produced simulation results that were in good agreement with

  5. A novel strategy to increase heating efficiency in a split-focus ultrasound phased array.

    PubMed

    Liu, Hao-Li; Shih, Tzu-Ching; Chen, Wen-Shiang; Ju, Kuen-Cheng

    2007-07-01

    Focus splitting using sector-based phased arrays increases the necrosed volume in a single sonication and reduces the total treatment time in the treatment of large tumors. However, split-focus sonication results in a lower energy density and worse focal-beam distortion, which limits its usefulness in practical treatments. Here, we propose a new heating strategy involving consecutive strongly focused and split-focus sonications to improve the heating efficiency. Theoretical predictions including linear and thermal-dose-dependent attenuation change were employed to investigate potential factors of this strategy, and ex vivo tissue experiments were conducted to confirm its effectiveness. Results showed that the thermal lesions produced by the proposed strategy could be increased when comparing with the previous reported strategies. The proposed heating strategy also induces a thermal lesion more rapidly, and exhibits higher robustness to various blood perfusion conditions, higher robustness to various power/heating time combinations, and superiority to generate deep-seated lesions through tissues with complex interfaces. Possible mechanisms include the optimization of the thermal conduction created by the strongly focused sonication and the temperature buildup gained from thermally induced tissue attenuation change based on the theoretical analysis. This may represent a useful technique for increasing the applicability of split-focus and multiple-focus sonication techniques, and solve the obstacles encountered when attempting to use these methods to shorten the total clinical treatment time.

  6. MRI-guided Therapeutic Ultrasound : In vitro Validation of a New MR Compatible, Phased Array, Contact Endorectal Ultrasound Transducer with Active Feedback Control of Temperature Evolution

    NASA Astrophysics Data System (ADS)

    Salomir, Rares; Rata, Mihaela; Lafon, Cyril; Melodelima, David; Chapelon, Jean-Yves; Mathias, Adrien; Cotton, François; Bonmartin, Alain; Cathignol, Dominique

    2006-05-01

    Contact application of high intensity ultrasound was demonstrated to be suitable for thermal ablation of sectorial tumours of the digestive duct. Experimental validation of a new MR compatible ultrasonic device is described here, dedicated to the minimal invasive therapy of localized colorectal cancer. This is a cylindrical 1D 64-element phased array transducer of 14 mm diameter and 25 mm height (Imasonic, France) allowing electronic rotation of the acoustic beam. Operating frequency ranges from 3.5 to 4.0 MHz and up to 5 effective electrical watts per element are available. A plane wave is reconstructed by simultaneous excitation of eigth adjacent elements with an appropriate phase law. Driving electronics operates outside the Faraday cage of the scanner and provides fast switching capabilities. Excellent passive and active compatibility with the MRI data acquisition has been demonstrated. In addition, feasibility of active temperature control has been demonstrated based on real-time data export out of the MR scanner and a PID feedback algorithm. Further studies will address the in-vivo validation and the integration of a miniature NMR coil for increased SNR in the near field.

  7. Large improvement of the electrical impedance of imaging and high-intensity focused ultrasound (HIFU) phased arrays using multilayer piezoelectric ceramics coupled in lateral mode.

    PubMed

    Song, Junho; Lucht, Benjamin; Hynynen, Kullervo

    2012-07-01

    With a change in phased-array configuration from one dimension to two, the electrical impedance of the array elements is substantially increased because of their decreased width (w)-to-thickness (t) ratio. The most common way to compensate for this impedance increase is to employ electrical matching circuits at a high cost of fabrication complexity and effort. In this paper, we introduce a multilayer lateral-mode coupling method for phased-array construction. The direct comparison showed that the electrical impedance of a single-layer transducer driven in thickness mode is 1/(n²(1/(w/t))²) times that of an n-layer lateral mode transducer. A large reduction of the electrical impedance showed the impact and benefit of the lateral-mode coupling method. A one-dimensional linear 32-element 770-kHz imaging array and a 42-element 1.45-MHz high-intensity focused ultrasound (HIFU) phased array were fabricated. The averaged electrical impedances of each element were measured to be 58 Ω at the maximum phase angle of -1.2° for the imaging array and 105 Ω at 0° for the HIFU array. The imaging array had a center frequency of 770 kHz with an averaged -6-dB bandwidth of approximately 52%. For the HIFU array, the averaged maximum surface acoustic intensity was measured to be 32.8 W/cm² before failure.

  8. Image-Guided Surgery of Primary Breast Cancer Using Ultrasound Phased Arrays

    DTIC Science & Technology

    2005-07-01

    obvious application of this capability is targeting tumors in results demonstrate what is potentially the most powerful advan- the liver that are...such as the ribs. This may be important if HIFU arrays are to be used for targeting, for example, liver tumors that may be partially obstructed by the...sufficient to justify identifying more complex lower scatter- ing critical structures. Furthermore, we are not suggesting that targets such as tumors

  9. Design and experimental evaluation of a 256-channel dual-frequency ultrasound phased-array system for transcranial blood-brain barrier opening and brain drug delivery.

    PubMed

    Liu, Hao-Li; Jan, Chen-Kai; Chu, Po-Chun; Hong, Jhong-Cing; Lee, Pei-Yun; Hsu, Jyh-Duen; Lin, Chung-Chih; Huang, Chiung-Ying; Chen, Pin-Yuan; Wei, Kuo-Chen

    2014-04-01

    Focused ultrasound (FUS) in the presence of microbubbles can bring about transcranial and local opening of the blood-brain barrier (BBB) for potential noninvasive delivery of drugs to the brain. A phased-array ultrasound system is essential for FUS-BBB opening to enable electronic steering and correction of the focal beam which is distorted by cranial bone. Here, we demonstrate our prototype design of a 256-channel ultrasound phased-array system for large-region transcranial BBB opening in the brains of large animals. One of the unique features of this system is the capability of generating concurrent dual-frequency ultrasound signals from the driving system for potential enhancement of BBB opening. A wide range of signal frequencies can be generated (frequency = 0.2-1.2 MHz) with controllable driving burst patterns. Precise output power can be controlled for individual channels via 8-bit duty-cycle control of transistor-transistor logic signals and the 8-bit microcontroller-controlled buck converter power supply output voltage. The prototype system was found to be in compliance with the electromagnetic compatibility standard. Moreover, large animal experiments confirmed the phase switching effectiveness of this system, and induction of either a precise spot or large region of BBB opening through fast focal-beam switching. We also demonstrated the capability of dual-frequency exposure to potentially enhance the BBB-opening effect. This study contributes to the design of ultrasound phased arrays for future clinical applications, and provides a new direction toward optimizing FUS brain drug delivery.

  10. Phase-rotation based receive-beamformer for miniaturized volumetric ultrasound imaging scanners using 2-D CMUT-on-ASIC arrays

    NASA Astrophysics Data System (ADS)

    Kim, Bae-Hyung; Lee, Seunghun; Song, Jongkeun; Kim, Youngil; Jeon, Taeho; Cho, Kyungil

    2013-03-01

    Up-to-date capacitive micromachined ultrasonic transducer (CMUT) technologies provide us unique opportunities to minimize the size and cost of ultrasound scanners by integrating front-end circuits into CMUT arrays. We describe a design prototype of a portable ultrasound scan-head probe using 2-D phased CMUT-on-ASIC arrays of 3-MHz 250 micrometer-pitch by fabricating and integrating front-end electronics with 2-D CMUT array elements. One of the objectives of our work is to design a receive beamformer architecture for the smart probe with compact size and comparable performance. In this work, a phase-rotation based receive beamformer using the sampling frequency of 4 times the center frequency and a hybrid beamforming to reduce the channel counts of the system-side are introduced. Parallel beamforming is considered for the purpose of saving power consumption of battery (by firing fewer times per image frame). This architecture has the advantage of directly obtaining I and Q components. By using the architecture, the interleaved I/Q data from the storage is acquired and I/Q demodulation for baseband processing is directly achieved without demodulators including sin and cosine lookup tables and mixers. Currently, we are extending the presented architecture to develop a true smart probe by including lower power devices and cooling systems, and bringing wireless data transmission into consideration.

  11. Active control of microbubbles stream in multi-bifurcated flow by using 2D phased array ultrasound transducer.

    PubMed

    Koda, Ren; Koido, Jun; Hosaka, Naoto; Ito, Takumi; Onogi, Shinya; Mochizuki, Takashi; Masuda, Kohji; Ikeda, Seiichi; Arai, Fumihito

    2013-01-01

    We have previously reported our attempt to propel microbbles in flow by a primary Bjerknes force, which is a physical phenomenon where an acoustic wave pushes an obstacle along its direction of propagation. However, when ultrasound was emitted from surface of the body, controlling bubbles in against flow was needed. It is unpractical to use multiple transducers to produce the same number of focal points because single element transducer cannot produce more than two focal points. In this study, we introduced a complex artificial blood vessel according to a capillary model and a 2D array transducer to produce multiple focal points for active control of microbubbles in against flow. Furthermore, we investigated bubble control in viscous fluid. As the results, we confirmed clearly path selection of MBs in viscous fluid as well as in water.

  12. Active aperture phased arrays

    NASA Astrophysics Data System (ADS)

    Shenoy, R. P.

    1989-04-01

    Developments towards the realization of active aperture phased arrays are reviewed. The technology and cost aspects of the power amplifier and phase shifter subsystems are discussed. Consideration is given to research concerning T/R modules, MESFETs, side lobe control, beam steering, optical control techniques, and printed circuit antennas. Methods for configuring the array are examined, focusing on the tile and brick configurations. It is found that there is no technological impediment for introducing active aperture phased arrays.

  13. Handheld ultrasound array imaging device

    NASA Astrophysics Data System (ADS)

    Hwang, Juin-Jet; Quistgaard, Jens

    1999-06-01

    A handheld ultrasound imaging device, one that weighs less than five pounds, has been developed for diagnosing trauma in the combat battlefield as well as a variety of commercial mobile diagnostic applications. This handheld device consists of four component ASICs, each is designed using the state of the art microelectronics technologies. These ASICs are integrated with a convex array transducer to allow high quality imaging of soft tissues and blood flow in real time. The device is designed to be battery driven or ac powered with built-in image storage and cineloop playback capability. Design methodologies of a handheld device are fundamentally different to those of a cart-based system. As system architecture, signal and image processing algorithm as well as image control circuit and software in this device is deigned suitably for large-scale integration, the image performance of this device is designed to be adequate to the intent applications. To elongate the battery life, low power design rules and power management circuits are incorporated in the design of each component ASIC. The performance of the prototype device is currently being evaluated for various applications such as a primary image screening tool, fetal imaging in Obstetrics, foreign object detection and wound assessment for emergency care, etc.

  14. The role of acoustic nonlinearity in tissue heating behind a rib cage using a high-intensity focused ultrasound phased array

    NASA Astrophysics Data System (ADS)

    Yuldashev, Petr V.; Shmeleva, Svetlana M.; Ilyin, Sergey A.; Sapozhnikov, Oleg A.; Gavrilov, Leonid R.; Khokhlova, Vera A.

    2013-04-01

    The goal of this study was to investigate theoretically the effects of nonlinear propagation in a high-intensity focused ultrasound (HIFU) field produced by a therapeutic phased array and the resultant heating of tissue behind a rib cage. Three configurations of focusing were simulated: in water, in water with ribs in the beam path and in water with ribs backed by a layer of soft tissue. The Westervelt equation was used to model the nonlinear HIFU field, and a 1 MHz phased array consisting of 254 circular elements was used as a boundary condition to the model. The temperature rise in tissue was modelled using the bioheat equation, and thermally necrosed volumes were calculated using the thermal dose formulation. The shapes of lesions predicted by the modelling were compared with those previously obtained in in vitro experiments at low-power sonications. Intensity levels at the face of the array elements that corresponded to the formation of high-amplitude shock fronts in the focal region were determined as 10 W cm-2 in the free field in water and 40 W cm-2 in the presence of ribs. It was shown that exposures with shocks provided a substantial increase in tissue heating, and its better spatial localization in the main focal region only. The relative effects of overheating ribs and splitting of the focus due to the periodic structure of the ribs were therefore reduced. These results suggest that utilizing nonlinear propagation and shock formation effects can be beneficial for inducing confined HIFU lesions when irradiating through obstructions such as ribs. Design of compact therapeutic arrays to provide maximum power outputs with lower intensity levels at the elements is necessary to achieve shock wave regimes for clinically relevant sonication depths in tissue.

  15. The role of acoustic nonlinearity in tissue heating behind a rib cage using a high-intensity focused ultrasound phased array.

    PubMed

    Yuldashev, Petr V; Shmeleva, Svetlana M; Ilyin, Sergey A; Sapozhnikov, Oleg A; Gavrilov, Leonid R; Khokhlova, Vera A

    2013-04-21

    The goal of this study was to investigate theoretically the effects of nonlinear propagation in a high-intensity focused ultrasound (HIFU) field produced by a therapeutic phased array and the resultant heating of tissue behind a rib cage. Three configurations of focusing were simulated: in water, in water with ribs in the beam path and in water with ribs backed by a layer of soft tissue. The Westervelt equation was used to model the nonlinear HIFU field, and a 1 MHz phased array consisting of 254 circular elements was used as a boundary condition to the model. The temperature rise in tissue was modelled using the bioheat equation, and thermally necrosed volumes were calculated using the thermal dose formulation. The shapes of lesions predicted by the modelling were compared with those previously obtained in in vitro experiments at low-power sonications. Intensity levels at the face of the array elements that corresponded to the formation of high-amplitude shock fronts in the focal region were determined as 10 W cm(-2) in the free field in water and 40 W cm(-2) in the presence of ribs. It was shown that exposures with shocks provided a substantial increase in tissue heating, and its better spatial localization in the main focal region only. The relative effects of overheating ribs and splitting of the focus due to the periodic structure of the ribs were therefore reduced. These results suggest that utilizing nonlinear propagation and shock formation effects can be beneficial for inducing confined HIFU lesions when irradiating through obstructions such as ribs. Design of compact therapeutic arrays to provide maximum power outputs with lower intensity levels at the elements is necessary to achieve shock wave regimes for clinically relevant sonication depths in tissue.

  16. Multibeam Phased Array Antennas

    NASA Technical Reports Server (NTRS)

    Popovic, Zoya; Romisch, Stefania; Rondineau, Sebastien

    2004-01-01

    In this study, a new architecture for Ka-band multi-beam arrays was developed and demonstrated experimentally. The goal of the investigation was to demonstrate a new architecture that has the potential of reducing the cost as compared to standard expensive phased array technology. The goals of this specific part of the project, as stated in the yearly statement of work in the original proposal are: 1. Investigate bounds on performance of multi-beam lens arrays in terms of beamwidths, volume (size), isolation between beams, number of simultaneous beams, etc. 2. Design a small-scale array to demonstrate the principle. The array will be designed for operation around 3OGHz (Ka-band), with two 10-degree beamwidth beams. 3. Investigate most appropriate way to accomplish fine-tuning of the beam pointing within 5 degrees around the main beam pointing angle.

  17. Addressing the Limit of Detectability of Residual Oxide Discontinuities in Friction Stir Butt Welds of Aluminum using Phased Array Ultrasound

    NASA Technical Reports Server (NTRS)

    Johnston, P. H.

    2008-01-01

    This activity seeks to estimate a theoretical upper bound of detectability for a layer of oxide embedded in a friction stir weld in aluminum. The oxide is theoretically modeled as an ideal planar layer of aluminum oxide, oriented normal to an interrogating ultrasound beam. Experimentally-measured grain scattering level is used to represent the practical noise floor. Echoes from naturally-occurring oxides will necessarily fall below this theoretical limit, and must be above the measurement noise to be potentially detectable.

  18. Addressing the Limit of Detectability of Residual Oxide Discontinuities in Friction Stir Butt Welds of Aluminum Using Phased Array Ultrasound

    NASA Astrophysics Data System (ADS)

    Johnston, P. H.

    2009-03-01

    This activity seeks to estimate a theoretical upper bound of detectability for a layer of oxide embedded in a friction stir weld in aluminum. The oxide is theoretically modeled as an ideal planar layer of aluminum oxide, oriented normal to an interrogating ultrasound beam. Experimentally-measured grain scattering level is used to represent the practical noise floor. Echoes from naturally-occurring oxides will necessarily fall below this theoretical limit, and must be above the measurement noise to be potentially detectable.

  19. Passive cavitation imaging with ultrasound arrays.

    PubMed

    Salgaonkar, Vasant A; Datta, Saurabh; Holland, Christy K; Mast, T Douglas

    2009-12-01

    A method is presented for passive imaging of cavitational acoustic emissions using an ultrasound array, with potential application in real-time monitoring of ultrasound ablation. To create such images, microbubble emissions were passively sensed by an imaging array and dynamically focused at multiple depths. In this paper, an analytic expression for a passive image is obtained by solving the Rayleigh-Sommerfield integral, under the Fresnel approximation, and passive images were simulated. A 192-element array was used to create passive images, in real time, from 520-kHz ultrasound scattered by a 1-mm steel wire. Azimuthal positions of this target were accurately estimated from the passive images. Next, stable and inertial cavitation was passively imaged in saline solution sonicated at 520 kHz. Bubble clusters formed in the saline samples were consistently located on both passive images and B-scans. Passive images were also created using broadband emissions from bovine liver sonicated at 2.2 MHz. Agreement was found between the images and source beam shape, indicating an ability to map therapeutic ultrasound beams in situ. The relation between these broadband emissions, sonication amplitude, and exposure conditions are discussed.

  20. Lateral mode coupling to reduce the electrical impedance of small elements required for high power ultrasound therapy phased arrays

    PubMed Central

    Hynynen, Kullervo; Yin, Jianhua

    2011-01-01

    A method that uses lateral coupling to reduce the electrical impedance of small transducer elements in generating ultrasound waves was tested. Cylindrical, radially-polled transducer elements were driven at their length resonance frequency. Computer simulation and experimental studies showed that the electrical impedance of the transducer element could be controlled by the cylinder wall thickness, while the operation frequency was determined by the cylinder length. Acoustic intensity (averaged over the cylinder diameter) over 10 W/cm2 (a therapeutically relevant intensity) was measured from these elements. PMID:19411214

  1. Design of a phased array for the generation of adaptive radiation force along a path surrounding a breast lesion for dynamic ultrasound elastography imaging.

    PubMed

    Ekeom, Didace; Hadj Henni, Anis; Cloutier, Guy

    2013-03-01

    This work demonstrates, with numerical simulations, the potential of an octagonal probe for the generation of radiation forces in a set of points following a path surrounding a breast lesion in the context of dynamic ultrasound elastography imaging. Because of the in-going wave adaptive focusing strategy, the proposed method is adapted to induce shear wave fronts to interact optimally with complex lesions. Transducer elements were based on 1-3 piezocomposite material. Three-dimensional simulations combining the finite element method and boundary element method with periodic boundary conditions in the elevation direction were used to predict acoustic wave radiation in a targeted region of interest. The coupling factor of the piezocomposite material and the radiated power of the transducer were optimized. The transducer's electrical impedance was targeted to 50 Ω. The probe was simulated by assembling the designed transducer elements to build an octagonal phased-array with 256 elements on each edge (for a total of 2048 elements). The central frequency is 4.54 MHz; simulated transducer elements are able to deliver enough power and can generate the radiation force with a relatively low level of voltage excitation. Using dynamic transmitter beamforming techniques, the radiation force along a path and resulting acoustic pattern in the breast were simulated assuming a linear isotropic medium. Magnitude and orientation of the acoustic intensity (radiation force) at any point of a generation path could be controlled for the case of an example representing a heterogeneous medium with an embedded soft mechanical inclusion.

  2. Phased array ghost elimination

    PubMed Central

    Kellman, Peter; McVeigh, Elliot R.

    2007-01-01

    Parallel imaging may be applied to cancel ghosts caused by a variety of distortion mechanisms, including distortions such as off-resonance or local flow, which are space variant. Phased array combining coefficients may be calculated that null ghost artifacts at known locations based on a constrained optimization, which optimizes SNR subject to the nulling constraint. The resultant phased array ghost elimination (PAGE) technique is similar to the method known as sensitivity encoding (SENSE) used for accelerated imaging; however, in this formulation is applied to full field-of-view (FOV) images. The phased array method for ghost elimination may result in greater flexibility in designing acquisition strategies. For example, in multi-shot EPI applications ghosts are typically mitigated by the use of an interleaved phase encode acquisition order. An alternative strategy is to use a sequential, non-interleaved phase encode order and cancel the resultant ghosts using PAGE parallel imaging. Cancellation of ghosts by means of phased array processing makes sequential, non-interleaved phase encode acquisition order practical, and permits a reduction in repetition time, TR, by eliminating the need for echo-shifting. Sequential, non-interleaved phase encode order has benefits of reduced distortion due to off-resonance, in-plane flow and EPI delay misalignment. Furthermore, the use of EPI with PAGE has inherent fat-water separation and has been used to provide off-resonance correction using a technique referred to as lipid elimination with an echo-shifting N/2-ghost acquisition (LEENA), and may further generalized using the multi-point Dixon method. Other applications of PAGE include cancelling ghosts which arise due to amplitude or phase variation during the approach to steady state. Parallel imaging requires estimates of the complex coil sensitivities. In vivo estimates may be derived by temporally varying the phase encode ordering to obtain a full k-space dataset in a scheme

  3. Optically interconnected phased arrays

    NASA Technical Reports Server (NTRS)

    Bhasin, Kul B.; Kunath, Richard R.

    1988-01-01

    Phased-array antennas are required for many future NASA missions. They will provide agile electronic beam forming for communications and tracking in the range of 1 to 100 GHz. Such phased arrays are expected to use several hundred GaAs monolithic integrated circuits (MMICs) as transmitting and receiving elements. However, the interconnections of these elements by conventional coaxial cables and waveguides add weight, reduce flexibility, and increase electrical interference. Alternative interconnections based on optical fibers, optical processing, and holography are under evaluation as possible solutions. In this paper, the current status of these techniques is described. Since high-frequency optical components such as photodetectors, lasers, and modulators are key elements in these interconnections, their performance and limitations are discussed.

  4. Optimized Hyperthermia Treatment of Prostate Cancer Using a Novel Intracavitary Ultrasound Array

    DTIC Science & Technology

    2005-01-01

    1.75 dimensional tapered ultrasound phased array for the treatment of prostate disease, Materials Research Innovation , 8, (2) 2004, pp 121-124...ultrasound phased array for the treatment of prostate disease, Materials Research Innovation , 8, (2) 2004, pp 121-124. anuscripts submitted Saleh, K...the treatment of prostate disease," Materials Research Innovation , vol. 8, no. 2, pp. 121-124, 2004a. [19] K. Saleh and N. B. Smith. "Two Dimensional

  5. All fiber sensor array for ultrasound sensing

    NASA Astrophysics Data System (ADS)

    Gabai, Haniel; Steinberg, Idan; Eyal, Avishay

    2016-03-01

    The field of Optical Fiber Sensors (OFS) is gaining tremendous popularity in recent years. OFS natural immunity to electromagnetic disturbances, inherent biocompatibility and compactness making them highly attractive for ultrasound sensing. Moreover, their compatibility with photoacoustics can make them useful in situations where traditional piezoelectric probes are inadequate. However, the issue of multiplexing individual OFS into an array remains a challenging and costly task. In this work, we demonstrate a straightforward approach for multiplexing multiple broadband OFS for ultrasound sensing by exploiting most of the photoreceiver's bandwidth. The design is based on a recently developed system in which all sensing elements are connected to a single interrogator and to a single digitizing circuit. To mitigate aliasing, the system employs I/Q coherent detection. Synchronization of the sensor interrogation with the excitation enables very high repetition rates (kHz) making it ideal for applications where imaging of dynamic processes is desired.

  6. Breast ultrasound tomography with two parallel transducer arrays

    NASA Astrophysics Data System (ADS)

    Huang, Lianjie; Shin, Junseob; Chen, Ting; Lin, Youzuo; Gao, Kai; Intrator, Miranda; Hanson, Kenneth

    2016-03-01

    Breast ultrasound tomography is an emerging imaging modality to reconstruct the sound speed, density, and ultrasound attenuation of the breast in addition to ultrasound reflection/beamforming images for breast cancer detection and characterization. We recently designed and manufactured a new synthetic-aperture breast ultrasound tomography prototype with two parallel transducer arrays consisting of a total of 768 transducer elements. The transducer arrays are translated vertically to scan the breast in a warm water tank from the chest wall/axillary region to the nipple region to acquire ultrasound transmission and reflection data for whole-breast ultrasound tomography imaging. The distance of these two ultrasound transducer arrays is adjustable for scanning breasts with different sizes. We use our breast ultrasound tomography prototype to acquire phantom and in vivo patient ultrasound data to study its feasibility for breast imaging. We apply our recently developed ultrasound imaging and tomography algorithms to ultrasound data acquired using our breast ultrasound tomography system. Our in vivo patient imaging results demonstrate that our breast ultrasound tomography can detect breast lesions shown on clinical ultrasound and mammographic images.

  7. Nonlinear phased array imaging

    NASA Astrophysics Data System (ADS)

    Croxford, Anthony J.; Cheng, Jingwei; Potter, Jack N.

    2016-04-01

    A technique is presented for imaging acoustic nonlinearity within a specimen using ultrasonic phased arrays. Acoustic nonlinearity is measured by evaluating the difference in energy of the transmission bandwidth within the diffuse field produced through different focusing modes. The two different modes being classical beam forming, where delays are applied to different element of a phased array to physically focus the energy at a single location (parallel firing) and focusing in post processing, whereby one element at a time is fired and a focused image produced in post processing (sequential firing). Although these two approaches are linearly equivalent the difference in physical displacement within the specimen leads to differences in nonlinear effects. These differences are localized to the areas where the amplitude is different, essentially confining the differences to the focal point. Direct measurement at the focal point are however difficult to make. In order to measure this the diffuse field is used. It is a statistical property of the diffuse field that it represents the total energy in the system. If the energy in the diffuse field for both the sequential and parallel firing case is measured then the difference between these, within the input signal bandwidth, is largely due to differences at the focal spot. This difference therefore gives a localized measurement of where energy is moving out of the transmission bandwidth due to nonlinear effects. This technique is used to image fatigue cracks and other damage types undetectable with conventional linear ultrasonic measurements.

  8. UAVSAR Phased Array Aperture

    NASA Technical Reports Server (NTRS)

    Chamberlain, Neil; Zawadzki, Mark; Sadowy, Greg; Oakes, Eric; Brown, Kyle; Hodges, Richard

    2009-01-01

    This paper describes the development of a patch antenna array for an L-band repeat-pass interferometric synthetic aperture radar (InSAR) instrument that is to be flown on an unmanned aerial vehicle (UAV). The antenna operates at a center frequency of 1.2575 GHz and with a bandwidth of 80 MHz, consistent with a number of radar instruments that JPL has previously flown. The antenna is designed to radiate orthogonal linear polarizations in order to facilitate fully-polarimetric measurements. Beam-pointing requirements for repeat-pass SAR interferometry necessitate electronic scanning in azimuth over a range of -20degrees in order to compensate for aircraft yaw. Beam-steering is accomplished by transmit/receive (T/R) modules and a beamforming network implemented in a stripline circuit board. This paper, while providing an overview of phased array architecture, focuses on the electromagnetic design of the antenna tiles and associated interconnects. An important aspect of the design of this antenna is that it has an amplitude taper of 10dB in the elevation direction. This is to reduce multipath reflections from the wing that would otherwise be detrimental to interferometric radar measurements. This taper is provided by coupling networks in the interconnect circuits as opposed to attenuating the output of the T/R modules. Details are given of material choices and fabrication techniques that meet the demanding environmental conditions that the antenna must operate in. Predicted array performance is reported in terms of co-polarized and crosspolarized far-field antenna patterns, and also in terms of active reflection coefficient.

  9. Phase array calibration orthogonal phase sequence

    NASA Technical Reports Server (NTRS)

    Sorace, Ronald E. (Inventor); Reinhardt, Victor S. (Inventor); Chan, Clinton (Inventor)

    1999-01-01

    Methods and systems for calibrating an array antenna are described. The array antenna has a plurality of antenna elements each having a signal with a phase and an amplitude forming an array antenna signal. For calibration, the phase of each element signal is sequentially switched one at a time through four orthogonal phase states. At each orthogonal phase state, the power of the array antenna signal is measured. A phase and an amplitude error for each of the element signals is determined based on the power of the array antenna signal at each of the four orthogonal phase states. The phase and amplitude of each of the element signals is then adjusted by the corresponding phase and amplitude errors.

  10. Investigation of standing-wave formation in a human skull for a clinical prototype of a large-aperture, transcranial MR-guided focused ultrasound (MRgFUS) phased array: an experimental and simulation study.

    PubMed

    Song, Junho; Pulkkinen, Aki; Huang, Yuexi; Hynynen, Kullervo

    2012-02-01

    Standing-wave formation in an ex vivo human skull was investigated using a clinical prototype of a 30-cm diameter with 15-cm radius of curvature, low-frequency (230 kHz), hemispherical transcranial magnetic resonance-guided focused ultrasound phased array. Experimental and simulation studies were conducted with changing aperture size and f -number configurations of the phased array and qualitatively and quantitatively examined the acoustic pressure variation at the focus due to standing waves. The results demonstrated that the nodes and antinodes of standing wave produced by the small-aperture array were clearly seen at approximately every 3 mm. The effect of the standing wave became more pronounced as the focus was moved closer to skull base. However, a sharp focus was seen for the full array, and there was no such standing-wave pattern in the acoustic plane or near the skull base. This study showed that the fluctuation pressure amplitude would be greatly reduced by using a large-scale, hemispherical phased array with a low f-number. © 2011 IEEE

  11. Investigation of standing wave formation in a human skull for a clinical prototype of a large-aperture, transcranial MR-guided Focused Ultrasound (MRgFUS) phased array: An experimental and simulation study

    PubMed Central

    Song, Junho; Pulkkinen, Aki; Huang, Yuexi; Hynynen, Kullervo

    2014-01-01

    Standing wave formation in an ex vivo human skull was investigated using a clinical prototype of a 30 cm diameter with 15 cm radius of curvature, low frequency (230 kHz), hemispherical transcranial Magnetic Resonance guided Focused Ultrasound (MRgFUS) phased-array. Experimental and simulation studies were conducted with changing aperture size and f-number configurations of the phased array, and qualitatively and quantitatively examined the acoustic pressure variation at the focus due to standing waves. The results demonstrated that the nodes and anti-nodes of standing wave produced by the small aperture array were clearly seen at approximately every 3 mm. The effect of the standing wave became more pronounced as the focus was moved closer to skull base. However, a sharp focus was seen for the full array, and there was no such standing wave pattern in the acoustic plane or near the skull base. This study showed that the fluctuation pressure amplitude would be greatly reduced by using a large-scale, hemispherical phased array with a low f-number. PMID:22049360

  12. Micromachined capacitive transducer arrays for intravascular ultrasound

    NASA Astrophysics Data System (ADS)

    Degertekin, F. Levent; Guldiken, R. Oytun; Karaman, Mustafa

    2005-01-01

    Intravascular ultrasound (IVUS) imaging has become an essential imaging modality for the effective diagnosis and treatment of cardiovascular diseases during the past decade enabled by innovative applications of piezoelectric transducer technology. The limitations in the manufacture and performance of the same piezoelectric transducers have also impeded the improvement of IVUS for emerging clinically important applications such as forward viewing arrays for guiding interventions and high resolution imaging of arterial structure such as vulnerable plaque and fibrous cap, and also implementation of techniques such as harmonic imaging of the tissue and of the contrast agents. Capacitive micromachined ultrasonic transducer (CMUT) technology shows great potential for transforming IVUS not only to satisfy these clinical needs but also to open up possibilities for low-cost imaging devices integrated to therapeutic tools. We have developed manufacturing processes with a maximum process temperature of 250°C to build CMUTs on the same silicon chip with integrated electronics. Using these processes we fabricated CMUT arrays suitable for forward viewing IVUS in the 10-20MHz range. We characterized these array elements in terms of pulse-echo response, radiation pattern measurements and demonstrated its volumetric imaging capabilities on various imaging targets.

  13. Error analysis of subaperture processing in 1-D ultrasound arrays.

    PubMed

    Zhao, Kang-Qiao; Bjåstad, Tore Gruner; Kristoffersen, Kjell

    2015-04-01

    To simplify the medical ultrasound system and reduce the cost, several techniques have been proposed to reduce the interconnections between the ultrasound probe and the back-end console. Among them, subaperture processing (SAP) is the most straightforward approach and is widely used in commercial products. This paper reviews the most important error sources of SAP, such as static focusing, delay quantization, linear delay profile, and coarse apodization, and the impacts introduced by these errors are shown. We propose to use main lobe coherence loss as a simple classification of the quality of the beam profile for a given design. This figure-ofmerit (FoM) is evaluated by simulations with a 1-D ultrasound subaperture array setup. The analytical expressions and the coherence loss can work as a quick guideline in subaperture design by equalizing the merit degradations from different error sources, as well as minimizing the average or maximum loss over ranges. For the evaluated 1-D array example, a good balance between errors and cost was achieved using a subaperture size of 5 elements, focus at 40 mm range, and a delay quantization step corresponding to a phase of π/4.

  14. Characterization of nonlinear ultrasound fields of 2D therapeutic arrays

    PubMed Central

    Yuldashev, Petr V.; Kreider, Wayne; Sapozhnikov, Oleg A.; Farr, Navid; Partanen, Ari; Bailey, Michael R.; Khokhlova, Vera

    2015-01-01

    A current trend in high intensity focused ultrasound (HIFU) technologies is to use 2D focused phased arrays that enable electronic steering of the focus, beamforming to avoid overheating of obstacles (such as ribs), and better focusing through inhomogeneities of soft tissue using time reversal methods. In many HIFU applications, the acoustic intensity in situ can reach thousands of W/cm2 leading to nonlinear propagation effects. At high power outputs, shock fronts develop in the focal region and significantly alter the bioeffects induced. Clinical applications of HIFU are relatively new and challenges remain for ensuring their safety and efficacy. A key component of these challenges is the lack of standard procedures for characterizing nonlinear HIFU fields under operating conditions. Methods that combine low-amplitude pressure measurements and nonlinear modeling of the pressure field have been proposed for axially symmetric single element transducers but have not yet been validated for the much more complex 3D fields generated by therapeutic arrays. Here, the method was tested for a clinical HIFU source comprising a 256-element transducer array. A numerical algorithm based on the Westervelt equation was used to enable 3D full-diffraction nonlinear modeling. With the acoustic holography method, the magnitude and phase of the acoustic field were measured at a low power output and used to determine the pattern of vibrations at the surface of the array. This pattern was then scaled to simulate a range of intensity levels near the elements up to 10 W/cm2. The accuracy of modeling was validated by comparison with direct measurements of the focal waveforms using a fiber-optic hydrophone. Simulation results and measurements show that shock fronts with amplitudes up to 100 MPa were present in focal waveforms at clinically relevant outputs, indicating the importance of strong nonlinear effects in ultrasound fields generated by HIFU arrays. PMID:26203345

  15. Characterization of nonlinear ultrasound fields of 2D therapeutic arrays.

    PubMed

    Yuldashev, Petr V; Kreider, Wayne; Sapozhnikov, Oleg A; Farr, Navid; Partanen, Ari; Bailey, Michael R; Khokhlova, Vera

    2012-10-07

    A current trend in high intensity focused ultrasound (HIFU) technologies is to use 2D focused phased arrays that enable electronic steering of the focus, beamforming to avoid overheating of obstacles (such as ribs), and better focusing through inhomogeneities of soft tissue using time reversal methods. In many HIFU applications, the acoustic intensity in situ can reach thousands of W/cm(2) leading to nonlinear propagation effects. At high power outputs, shock fronts develop in the focal region and significantly alter the bioeffects induced. Clinical applications of HIFU are relatively new and challenges remain for ensuring their safety and efficacy. A key component of these challenges is the lack of standard procedures for characterizing nonlinear HIFU fields under operating conditions. Methods that combine low-amplitude pressure measurements and nonlinear modeling of the pressure field have been proposed for axially symmetric single element transducers but have not yet been validated for the much more complex 3D fields generated by therapeutic arrays. Here, the method was tested for a clinical HIFU source comprising a 256-element transducer array. A numerical algorithm based on the Westervelt equation was used to enable 3D full-diffraction nonlinear modeling. With the acoustic holography method, the magnitude and phase of the acoustic field were measured at a low power output and used to determine the pattern of vibrations at the surface of the array. This pattern was then scaled to simulate a range of intensity levels near the elements up to 10 W/cm(2). The accuracy of modeling was validated by comparison with direct measurements of the focal waveforms using a fiber-optic hydrophone. Simulation results and measurements show that shock fronts with amplitudes up to 100 MPa were present in focal waveforms at clinically relevant outputs, indicating the importance of strong nonlinear effects in ultrasound fields generated by HIFU arrays.

  16. Active membrane phased array radar

    NASA Technical Reports Server (NTRS)

    Moussessian, Alina; Del Castillo, Linda; Huang, John; Sadowy, Greg; Hoffman, James; Smith, Phil; Hatake, Toshiro; Derksen, Chuck; Lopez, Bernardo; Caro, Ed

    2005-01-01

    We have developed the first membrane-based active phased array in L-band (1.26GHz). The array uses membrane compatible Transmit/Receive (T/R) modules (membrane T/R) for each antenna element. We use phase shifters within each T/R module for electronic beam steering. We will discuss the T/R module design and integration with the membrane, We will also present transmit and receive beam-steering results for the array.

  17. Active membrane phased array radar

    NASA Technical Reports Server (NTRS)

    Moussessian, Alina; Del Castillo, Linda; Huang, John; Sadowy, Greg; Hoffman, James; Smith, Phil; Hatake, Toshiro; Derksen, Chuck; Lopez, Bernardo; Caro, Ed

    2005-01-01

    We have developed the first membrane-based active phased array in L-band (1.26GHz). The array uses membrane compatible Transmit/Receive (T/R) modules (membrane T/R) for each antenna element. We use phase shifters within each T/R module for electronic beam steering. We will discuss the T/R module design and integration with the membrane, We will also present transmit and receive beam-steering results for the array.

  18. [Modeling and simulation of responses from ultrasonic linear phased array].

    PubMed

    He, Wenjing; Zhu, Yuanzhong; Wang, Yufeng; He, Lingli; Lai, Siyu

    2012-10-01

    Phased array transducers are very attractive because the beam generated by the arrays can be electronically focused and steered. The present work characterizes far-field 2D properties of phased array system by functions that are deduced from rectangle source, rectangle line array and phased array based on point source. Results are presented for the distribution of ultrasound intensity on plane xoz and on x-axis by simulation using numerical calculation. It is shown that the shape of response of rectangle line array is modulated by the single array element. It is also demonstrated that the delay time of phased array is the key to steer the beam, sacrificing the value of main lobe and increasing the number of side lobes.

  19. Multilayer Array Transducer for Nonlinear Ultrasound Imaging

    NASA Astrophysics Data System (ADS)

    Owen, Neil R.; Kaczkowski, Peter J.; Li, Tong; Gross, Dan; Postlewait, Steven M.; Curra, Francesco P.

    2011-09-01

    The properties of nonlinear acoustic wave propagation are known to be able to improve the resolution of ultrasound imaging, and could be used to dynamically estimate the physical properties of tissue. However, transducers capable of launching a wave that becomes nonlinear through propagation do not typically have the necessary bandwidth to detect the higher harmonics. Here we present the design and characterization of a novel multilayer transducer for high intensity transmit and broadband receive. The transmit layer was made from a narrow-band, high-power piezoceramic (PZT), with nominal frequency of 2.0 MHz, that was diced into an array of 32 elements. Each element was 0.300 mm wide and 6.3 mm in elevation, and with a pitch of 0.400 mm the overall aperture width was 12.7 mm. A quarter-wave matching layer was attached to the PZT substrate to improve transmit efficiency and bandwidth. The overlaid receive layer was made from polyvinylidene fluoride (PVDF) that had gold metalization on one side. A custom two-sided flex circuit routed electrical connections to the PZT elements and patterned the PVDF elements; the PZT and PVDF elements had identical apertures. A low viscosity and electrically nonconductive epoxy was used for all adhesion layers. Characterization of electrical parameters and acoustic output were performed per standard methods, where transmit and receive events were driven by a software-controlled ultrasound engine. Echo data, collected from ex vivo tissue and digitized at 45 MS/s, exhibited frequency content up to the 4th harmonic of the 2 MHz transmit frequency.

  20. Development of a Fibre-Phased Array Laser-EMAT Ultrasonic System for Defect Inspection

    NASA Astrophysics Data System (ADS)

    Pei, C.; Demachi, K.; Fukuchi, T.; Koyama, K.; Uesaka, M.; Chen, Z.

    2014-06-01

    In this work, a phased array laser ultrasound system with using fibre optic delivery and a custom-designed focusing objective lens has been developed for enhancing the ultrasound generation. The fibre-phased array method is applied to improve the sensitivity and detecting ability of the laser-EMAT system for defect inspection.

  1. Phase multiplying electronic scanning array

    NASA Technical Reports Server (NTRS)

    Seaton, A. F.

    1969-01-01

    Scanning array was designed with properties of low RF loss and phase control. The array consists of a series of special waveguides, hybrids made up of two variable reactance branch arms for input signals, an edge slot for the difference port, and a sum arm for the unradiated signal.

  2. Phased array observations with infield phasing

    NASA Astrophysics Data System (ADS)

    Kudale, Sanjay; Chengalur, Jayaram N.

    2017-07-01

    We present results from pulsar observations using the Giant Metrewave Radio Telescope (GMRT) as a phased array with infield phasing. The antennas were kept in phase throughout the observation by applying antenna based phase corrections derived from visibilities that were obtained in parallel with the phased array beam data, and which were flagged and calibrated in real time using a model for the continuum emission in the target field. We find that, as expected, the signal to noise ratio (SNR) does not degrade with time. In contrast observations in which the phasing is done only at the start of the observation show a clear degradation of the SNR with time. We find that this degradation is well fit by a function of the form SNR (τ ) = α + β e^{-(τ /τ 0)^{5/3}}, which corresponds to the case where the phase drifts are caused by Kolmogorov type turbulence in the ionosphere. We also present general formulae (i.e. including the effects of correlated sky noise, imperfect phasing and self noise) for the SNR and synthesized beam size for phased arrays (as well as corresponding formulae for incoherent arrays). These would be useful in planning observations with large array telescopes.

  3. Phased array observations with infield phasing

    NASA Astrophysics Data System (ADS)

    Kudale, Sanjay; Chengalur, Jayaram N.

    2017-10-01

    We present results from pulsar observations using the Giant Metrewave Radio Telescope (GMRT) as a phased array with infield phasing. The antennas were kept in phase throughout the observation by applying antenna based phase corrections derived from visibilities that were obtained in parallel with the phased array beam data, and which were flagged and calibrated in real time using a model for the continuum emission in the target field. We find that, as expected, the signal to noise ratio (SNR) does not degrade with time. In contrast observations in which the phasing is done only at the start of the observation show a clear degradation of the SNR with time. We find that this degradation is well fit by a function of the form SNR(τ ) = α + β e^{-(τ /τ 0)^{5/3}}, which corresponds to the case where the phase drifts are caused by Kolmogorov type turbulence in the ionosphere. We also present general formulae (i.e. including the effects of correlated sky noise, imperfect phasing and self noise) for the SNR and synthesized beam size for phased arrays (as well as corresponding formulae for incoherent arrays). These would be useful in planning observations with large array telescopes.

  4. Distributed phased array architecture study

    NASA Technical Reports Server (NTRS)

    Bourgeois, Brian

    1987-01-01

    Variations in amplifiers and phase shifters can cause degraded antenna performance, depending also on the environmental conditions and antenna array architecture. The implementation of distributed phased array hardware was studied with the aid of the DISTAR computer program as a simulation tool. This simulation provides guidance in hardware simulation. Both hard and soft failures of the amplifiers in the T/R modules are modeled. Hard failures are catastrophic: no power is transmitted to the antenna elements. Noncatastrophic or soft failures are modeled as a modified Gaussian distribution. The resulting amplitude characteristics then determine the array excitation coefficients. The phase characteristics take on a uniform distribution. Pattern characteristics such as antenna gain, half power beamwidth, mainbeam phase errors, sidelobe levels, and beam pointing errors were studied as functions of amplifier and phase shifter variations. General specifications for amplifier and phase shifter tolerances in various architecture configurations for C band and S band were determined.

  5. Simulation study of the effects of near- and far-field heating during focused ultrasound uterine fibroid ablation using an electronically focused phased array: A theoretical analysis of patient safety

    SciTech Connect

    Ellens, Nicholas Hynynen, Kullervo

    2014-07-15

    Purpose: Assess the feasibility of using large-aperture, flat ultrasonic transducer arrays with 6500 small elements operating at 500 kHz without the use of any mechanical components for the thermal coagulation of uterine fibroids. This study examines the benefits and detriments of using a frequency that is significantly lower than that used in clinical systems (1–1.5 MHz). Methods: Ultrasound simulations were performed using the anatomies of five fibroid patients derived from 3D MRI. Using electronic steering solely, the ultrasound focus from a flat, 6500-element phased array was translated around the volume of the fibroids in various patterns to assess the feasibility of completing full treatments from fixed physical locations. Successive temperature maps were generated by numerically solving the bioheat equation. Using a thermal dose model, the bioeffects of these simulations were quantified and analyzed. Results: The simulations indicate that such an array could be used to perform fibroid treatments to 18 EM{sub 43} at an average rate of 90 ± 20 cm{sup 3}/h without physically moving the transducer array. On average, the maximum near-field thermal dose for each patient was below 4 EM{sub 43}. Fibroid tissue could be treated as close as 40 mm to the spine without reaching temperatures expected to cause pain or damage. Conclusions: Fibroids were successfully targeted and treated from a single transducer position to acceptable extents and without causing damage in the near- or far-field. Compared to clinical systems, treatment rates were good. The proposed treatment paradigm is a promising alternative to existing systems and warrants further investigation.

  6. Phase-locked laser array

    NASA Technical Reports Server (NTRS)

    Botez, Dan (Inventor)

    1987-01-01

    A phase-locked laser array comprises a body of semiconductor material having means for defining a plurality of substantially parallel lasing zones which are spaced an effective distance apart so that the modes of the adjacent lasing zones are phase-locked to one another. One of the array electrodes comprises a plurality of electrical contacts to the body between the lasing zones. These contacts provide an enhanced current density profile and thus an increase in the gain in the regions between the lasing zones so that zero degree phase-shift operation between adjacent lasing zones is achievable.

  7. A New Design Approach for Dual-Mode Ultrasound Arrays

    NASA Astrophysics Data System (ADS)

    Wan, Yayun; Ebbini, Emad

    2009-04-01

    Advances in piezocomposite transducer technology have made it possible to design and fabricate therapeutic phased arrays with sufficiently high bandwidth and low element cross coupling to produce high-quality HIFU beams. These improvements have also allowed for the use of such arrays in dual-mode operation as imaging and therapy arrays. We have reported on a 1-MHz, 64-element concave dual-mode ultrasound array (DMUA) prototype with 100-mm radius of curvature. However, the imaging capabilities of this prototype remain limited by the coarse sampling of the large, concave aperture, i.e. the therapeutic performance of the DMUA was maintained at the expense of degradation in the imaging performance. We have conducted a simulation study of a new design approach for DMUAs that significantly improves their imaging performance without compromising their therapeutic capabilities. The approach is based on the use a finely sampled aperture in imaging mode (to optimize the spatial and contrast resolutions) and a coarsely sampled aperture in therapeutic mode (to optimize the therapeutic gain and driver efficiency). We will describe a 128×8 DMUA structure that can be configured as a 64×1 array in therapeutic mode and 128×1 in imaging mode. Pulse-mode simulations of wire targets and cyst phantoms using the Field II program show that the new DMUA design offers significant improvement in both spatial and contrast resolutions compared to the existing prototype design. These results provide initial validation of our approach toward the design and fabrication of piezocomposite DMUAs which are simultaneously optimized for therapeutic and imaging operations.

  8. Modeling of phased array transducers.

    PubMed

    Ahmad, Rais; Kundu, Tribikram; Placko, Dominique

    2005-04-01

    Phased array transducers are multi-element transducers, where different elements are activated with different time delays. The advantage of these transducers is that no mechanical movement of the transducer is needed to scan an object. Focusing and beam steering is obtained simply by adjusting the time delay. In this paper the DPSM (distributed point source method) is used to model the ultrasonic field generated by a phased array transducer and to study the interaction effect when two phased array transducers are placed in a homogeneous fluid. Earlier investigations modeled the acoustic field for conventional transducers where all transducer points are excited simultaneously. In this research, combining the concepts of delayed firing and the DPSM, the phased array transducers are modeled semi-analytically. In addition to the single transducer modeling the ultrasonic fields from two phased array transducers placed face to face in a fluid medium is also modeled to study the interaction effect. The importance of considering the interaction effect in multiple transducer modeling is discussed, pointing out that neighboring transducers not only act as ultrasonic wave generators but also as scatterers.

  9. A conformal ultrasound transducer array featuring microfabricated polyimide joints

    NASA Astrophysics Data System (ADS)

    Bennett, David B.; Culjat, Martin O.; Cox, Brian P.; Dann, Aaron E.; Williams, Kimani; Lee, Hua; Brown, Elliott R.; Grundfest, Warren S.; Singh, Rahul S.

    2009-03-01

    Due to their increased angular coverage around body surfaces, conformal ultrasound transducers may potentially provide increased signal acquisition relative to rigid medical ultrasound probes and eliminate the need for mechanical scanning. This paper describes a novel, high efficiency, and robust conformal ultrasound transducer array based on a flexible substrate of silicon islands joined together using polyimide joints. The array incorporated diced bulk lead zirconate titanate (PZT) mounted atop the silicon islands as its piezoelectric material for its desirable electromechanical coupling factor and high piezoelectric coefficients. Parylene thin films deposited over the array reinforced the bendable joints, encapsulated the metal film interconnects, and formed, in conjunction with the silicon, an acoustical match between the PZT and soft tissue. Eight element linear arrays were fabricated with a pitch of 3.5 mm, operating at a center frequency of 12 MHz with a 6dB bandwidth of 27%. The robustness of the transducer was demonstrated by iterative bending around a 1 cm diameter cylinder, and the durability of the electrical traces and the frequency performance was measured using a vector network analyzer. This paper presents a robust, durable conformal ultrasound array with the versatility to scale to enable new applications in diagnostic ultrasound imaging.

  10. Development of high frequency annular array ultrasound transducers

    NASA Astrophysics Data System (ADS)

    Gottlieb, Emanuel John

    The advantage of ultrasonic annular arrays over conventional single element transducers has been in the ability to transmit focus at multiple points throughout the depth of field, as well as receive dynamic focus. Today, annular, linear and multidimensional array imaging systems are not commercially available at frequencies greater than 20 MHz. The fabrication technology used to develop a high frequency (>50 MHz) annular array transducer is presented. A 9 mum P(VDF-TrFE) film was bonded to gold annuli electrodes on the top layer of a two sided polyimide flexible circuit. Each annulus was separated by a 30 mum kerf and had several electroplated micro vias that connected to electrode traces on the bottom side of the polyimide flexible circuit. The array's performance was evaluated by measuring the electrical impedance, pulse echo response and crosstalk measurement for each element in the array. In order to improve device sensitivity each element was electrically matched to an impedance magnitude of 50 O and 0° phase at resonance. The average round trip insertion loss measured for the array and compensated for diffraction effects was -33.5 dB. The measured average center frequency and bandwidth of an element was 55 MHz and 47 respectively. The measured crosstalk between adjacent elements remained below -29 dB at the center frequency in water. A vertical wire phantom was imaged using a single focus transmit beamformer and dynamic focusing receive beamformer. This image showed a significant improvement in lateral resolution over a range of 9 mm after the dynamic focusing receive algorithm was applied. These results correlated well with predictions from a Field II simulation. After beamforming the minimum lateral resolution (-6 dB) was 108 mum at the focus. Preliminary ultrasound B-mode images of the rabbit eye using this transducer were shown in conjunction with a multi-channel digital beamformer. A feasibility study of designing and fabricating tunable copolymer

  11. EHF multifunction phased array antenna

    NASA Astrophysics Data System (ADS)

    Solbach, Klaus

    1986-07-01

    The design of a low cost demonstration EHF multifunction-phased array antenna is described. Both, the radiating elements and the phase-shifter circuits are realized on microstrip substrate material in order to allow photolithographic batch fabrication. Self-encapsulated beam-lead PIN-diodes are employed as the electronic switch elements to avoid expensive hermetic encapsulation of the semiconductors or complete circuits. A space-feed using a horn-radiator to illuminate the array from the front-side is found to be the simplest and most inexpensive feed. The phased array antenna thus operates as a reflect-array, the antenna elements employed in a dual role for the collection of energy from the feed-horn and for the re-radiation of the phase-shifted waves (in transmit-mode). The antenna is divided into modules containing the radiator/phase-shifter plate plus drive- and BITE-circuitry at the back. Both drive- and BITE-components use gate-array integrated circuits especially designed for the purpose. Several bus-systems are used to supply bias and logical data flows to the modules. The beam-steering unit utilizes several signal processors and high-speed discrete adder circuits to combine the pointing, frequency and beam-shape information from the radar system computer with the stored phase-shift codes for the array elements. Since space, weight and power consumption are prime considerations only the most advanced technology is used in the design of both the microwave and the digital/drive circuitry.

  12. Phased Array Feeds

    NASA Astrophysics Data System (ADS)

    Fisher, J. Richard; Bradley, Richard F.; Brisken, Walter F.; Cotton, William D.; Emerson, Darrel T.; Kerr, Anthony R.; Lacasse, Richard J.; Morgan, Matthew A.; Napier, Peter J.; Norrod, Roger D.; Payne, John M.; Pospieszalski, Marian W.; Symmes, Arthur; Thompson, A. Richard; Webber, John C.

    2009-03-01

    This white paper offers cautionary observations about the planning and development of new, large radio astronomy instruments. Complexity is a strong cost driver so every effort should be made to assign differing science requirements to different instruments and probably different sites. The appeal of shared resources is generally not realized in practice and can often be counterproductive. Instrument optimization is much more difficult with longer lists of requirements, and the development process is longer and less efficient. More complex instruments are necessarily further behind the technology state of the art because of longer development times. Including technology R&D in the construction phase of projects is a growing trend that leads to higher risks, cost overruns, schedule delays, and project de-scoping. There are no technology breakthroughs just over the horizon that will suddenly bring down the cost of collecting area. Advances come largely through careful attention to detail in the adoption of new technology provided by industry and the commercial market. Radio astronomy instrumentation has a very bright future, but a vigorous long-term R&D program not tied directly to specific projects needs to be restored, fostered, and preserved.

  13. High Frequency Ultrasound Array Designed for Ultrasound Guided Breast Biopsy

    PubMed Central

    Cummins, Thomas; Eliahoo, Payam; Shung, K. Kirk

    2016-01-01

    This paper describes the development of a miniaturized high frequency linear array that can be integrated within a core biopsy needle to improve tissue sampling accuracy during breast cancer biopsy procedures. The 64 element linear array has an element width of 14 μm, kerf width of 6 μm, element length of 1 mm and element thickness of 24 μm. The 2–2 array composite was fabricated using deep reactive ion etching of PMN-PT single crystal material. The array composite fabrication process as well as a novel high density electrical interconnect solution are presented and discussed. Array performance measurements show that the array had a center frequency and fractional bandwidth (−6 dB) of 59.1 MHz and 29.4%, respectively. Insertion loss and adjacent element cross talk at the center frequency were −41.0 dB and −23.7 dB, respectively. A B-mode image of a tungsten wire target phantom was captured using a synthetic aperture imaging system and the imaging test results demonstrate axial and lateral resolutions of 33.2 μm and 115.6 um, respectively. PMID:27046895

  14. Robotic inspection of fiber reinforced composites using phased array UT

    NASA Astrophysics Data System (ADS)

    Stetson, Jeffrey T.; De Odorico, Walter

    2014-02-01

    Ultrasound is the current NDE method of choice to inspect large fiber reinforced airframe structures. Over the last 15 years Cartesian based scanning machines using conventional ultrasound techniques have been employed by all airframe OEMs and their top tier suppliers to perform these inspections. Technical advances in both computing power and commercially available, multi-axis robots now facilitate a new generation of scanning machines. These machines use multiple end effector tools taking full advantage of phased array ultrasound technologies yielding substantial improvements in inspection quality and productivity. This paper outlines the general architecture for these new robotic scanning systems as well as details the variety of ultrasonic techniques available for use with them including advances such as wide area phased array scanning and sound field adaptation for non-flat, non-parallel surfaces.

  15. Automated Array Assembly, Phase 2

    NASA Technical Reports Server (NTRS)

    Carbajal, B. G.

    1979-01-01

    The Automated Array Assembly Task, Phase 2 of the Low Cost Silicon Solar Array Project is a process development task. The contract provides for the fabrication of modules from large area tandem junction cells (TJC). During this quarter, effort was focused on the design of a large area, approximately 36 sq cm, TJC and process verification runs. The large area TJC design was optimized for minimum I squared R power losses. In the TJM activity, the cell-module interfaces were defined, module substrates were formed and heat treated and clad metal interconnect strips were fabricated.

  16. Airborne electronically steerable phased array

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The results are presented of the second stage of a program for the design and development of a phased array capable of simultaneous and separate transmission and reception of radio frequency signals at S-band frequencies. The design goals of this stage were the development of three major areas of interest required for the final prototype model. These areas are the construction and testing of the low-weight, full-scale 128-element array of antenna elements, the development of the RF manifold feed system, and the construction and testing of a working module containing diplexer and transmit and receive circuits.

  17. Optical phased-array ladar.

    PubMed

    Montoya, Juan; Sanchez-Rubio, Antonio; Hatch, Robert; Payson, Harold

    2014-11-01

    We demonstrate a ladar with 0.5 m class range resolution obtained by integrating a continuous-wave optical phased-array transmitter with a Geiger-mode avalanche photodiode receiver array. In contrast with conventional ladar systems, an array of continuous-wave sources is used to effectively pulse illuminate a target by electro-optically steering far-field fringes. From the reference frame of a point in the far field, a steered fringe appears as a pulse. Range information is thus obtained by measuring the arrival time of a pulse return from a target to a receiver pixel. This ladar system offers a number of benefits, including broad spectral coverage, high efficiency, small size, power scalability, and versatility.

  18. Laser array generated ultrasound for weld quality control

    SciTech Connect

    Graham, G.M.; Ume, C.I.

    1996-12-31

    Currently, no on-line techniques exist for direct penetration measurement in automated welding processes. The development of a penetration control system will significantly reduce the costs associated with repairing or scrapping defective work. Laser array generated ultrasound is one noncontact, nondestructive method of measuring weld penetration depth. This paper will discuss the development of a laser fiber bundle array and EMAT (electromagnetic acoustic transducer) system for the generation and reception of ultrasound for on-line weld penetration measurement. Experimental results will be shown for penetration measurement in simulated solidified and liquid welds at room and elevated temperatures. Results will be compared with an analytical model for ultrasound time-of-flight in simulated solidified welds at room temperature.

  19. Cabling design for phased arrays

    NASA Technical Reports Server (NTRS)

    Kruger, I. D.; Turkiewicz, L.

    1972-01-01

    The ribbon-cabling system used for the AEGIS phased array which provides minimum cable bulk, complete EMI shielding, rugged mechanical design, repeatable electrical characteristics, and ease of assembly and maintenance is described. The ribbon cables are 0.040-inch thick, and in widths up to 2 1/2 inches. Their terminations are molded connectors that can be grouped in a three-tier arrangement, with cable branching accomplished by a matrix-welding technique.

  20. Cabling design for phased arrays

    NASA Technical Reports Server (NTRS)

    Kruger, I. D.; Turkiewicz, L.

    1972-01-01

    The ribbon-cabling system used for the AEGIS phased array which provides minimum cable bulk, complete EMI shielding, rugged mechanical design, repeatable electrical characteristics, and ease of assembly and maintenance is described. The ribbon cables are 0.040-inch thick, and in widths up to 2 1/2 inches. Their terminations are molded connectors that can be grouped in a three-tier arrangement, with cable branching accomplished by a matrix-welding technique.

  1. C-scan transmission ultrasound based on a hybrid microelectronic sensor array and its physical performance

    NASA Astrophysics Data System (ADS)

    Lo, Shih-Chung B.; Rich, David; Lasser, Marvin E.; Kula, John; Zhao, Hui; Lasser, Bob; Freedman, Matthew T.

    2001-05-01

    A C-scan through-transmission ultrasound system has been constructed based on a patented hybrid microelectronic array that is capable of generating ultrasound images with fluoroscopic presentation. To generate real-time images, ultrasound is introduced into the object under study with a large unfocused plane wave source. The resultant pressure wave strikes the object and is attenuated and scattered. The device detects scattered as well as attenuated ultrasound energy which allows the use of an acoustic lens to focus on detected energy from an object plane. The acoustic lens collects the transmitted energy and focuses it onto the ultrasound sensitive array. The array is made up to two components, a silicon detector/readout array and a piezoelectric material that is deposited onto the array through semiconductor processing. The array is 1 cm on a side consisting of 128x128 pixel elements with 85micrometers pixel spacing. The energy that strikes the piezoelectric material is converted to an analog voltage that is digitized and processed by low cost commercial video electronics. The images generated by the device appear with no speckle artifact with fluoroscopy-like presentation. The images show no obvious geometrical distortion. The experimental results indicated that the system has a spatial resolution of 0.32 mm. It can resolve 3mm objects with low differential contrast and an attenuation coefficient difference less than 0.07 dB/cm/MHz. Phase contrast of the objects are also clearly measurable. A presentation of a C- scan image guided breast biopsy was demonstrated. In addition, punctured needle tracks in a tumor was clearly observed. This implies the potential of observing the spiculation of masses in vivo.

  2. Adaptive ground implemented phase array

    NASA Technical Reports Server (NTRS)

    Spearing, R. E.

    1973-01-01

    The simulation of an adaptive ground implemented phased array of five antenna elements is reported for a very high frequency system design that is tolerant to the radio frequency interference environment encountered by a tracking data relay satellite. Signals originating from satellites are received by the VHF ring array and both horizontal and vertical polarizations from each of the five elements are multiplexed and transmitted down to ground station. A panel on the transmitting end of the simulation chamber contains up to 10 S-band RFI sources along with the desired signal to simulate the dynamic relationship between user and TDRS. The 10 input channels are summed, and desired and interference signals are separated and corrected until the resultant sum signal-to-interference ratio is maximized. Testing performed with this simulation equipment demonstrates good correlation between predicted and actual results.

  3. Imaging phased telescope array study

    NASA Technical Reports Server (NTRS)

    Harvey, James E.

    1989-01-01

    The problems encountered in obtaining a wide field-of-view with large, space-based direct imaging phased telescope arrays were considered. After defining some of the critical systems issues, previous relevant work in the literature was reviewed and summarized. An extensive list was made of potential error sources and the error sources were categorized in the form of an error budget tree including optical design errors, optical fabrication errors, assembly and alignment errors, and environmental errors. After choosing a top level image quality requirment as a goal, a preliminary tops-down error budget allocation was performed; then, based upon engineering experience, detailed analysis, or data from the literature, a bottoms-up error budget reallocation was performed in an attempt to achieve an equitable distribution of difficulty in satisfying the various allocations. This exercise provided a realistic allocation for residual off-axis optical design errors in the presence of state-of-the-art optical fabrication and alignment errors. Three different computational techniques were developed for computing the image degradation of phased telescope arrays due to aberrations of the individual telescopes. Parametric studies and sensitivity analyses were then performed for a variety of subaperture configurations and telescope design parameters in an attempt to determine how the off-axis performance of a phased telescope array varies as the telescopes are scaled up in size. The Air Force Weapons Laboratory (AFWL) multipurpose telescope testbed (MMTT) configuration was analyzed in detail with regard to image degradation due to field curvature and distortion of the individual telescopes as they are scaled up in size.

  4. Proceedings: EPRI Second Phased Array Inspection Seminar

    SciTech Connect

    2001-11-01

    The Second EPRI Phased Array Inspection Seminar focused on industrial applications of phased array technology that have been achieved to date or are planned for the near future. Presentations were made by developers of inspection techniques, inspection services vendors, and utility personnel who have performed inspections using arrays.

  5. The application of sparse arrays in high frequency transcranial focused ultrasound therapy: A simulation study

    PubMed Central

    Pajek, Daniel; Hynynen, Kullervo

    2013-01-01

    Purpose: Transcranial focused ultrasound is an emerging therapeutic modality that can be used to perform noninvasive neurosurgical procedures. The current clinical transcranial phased array operates at 650 kHz, however the development of a higher frequency array would enable more precision, while reducing the risk of standing waves. However, the smaller wavelength and the skull's increased distortion at this frequency are problematic. It would require an order of magnitude more elements to create such an array. Random sparse arrays enable steering of a therapeutic array with fewer elements. However, the tradeoffs inherent in the use of sparsity in a transcranial phased array have not been systematically investigated and so the objective of this simulation study is to investigate the effect of sparsity on transcranial arrays at a frequency of 1.5 MHz that provides small focal spots for precise exposure control. Methods: Transcranial sonication simulations were conducted using a multilayer Rayleigh-Sommerfeld propagation model. Element size and element population were varied and the phased array's ability to steer was assessed. Results: The focal pressures decreased proportionally as elements were removed. However, off-focus hotspots were generated if a high degree of steering was attempted with very sparse arrays. A phased array consisting of 1588 elements 3 mm in size, a 10% population, was appropriate for steering up to 4 cm in all directions. However, a higher element population would be required if near-skull sonication is desired. Conclusions: This study demonstrated that the development of a sparse, hemispherical array at 1.5 MHz could enable more precision in therapies that utilize lower intensity sonications. PMID:24320540

  6. The application of sparse arrays in high frequency transcranial focused ultrasound therapy: A simulation study

    SciTech Connect

    Pajek, Daniel Hynynen, Kullervo

    2013-12-15

    Purpose: Transcranial focused ultrasound is an emerging therapeutic modality that can be used to perform noninvasive neurosurgical procedures. The current clinical transcranial phased array operates at 650 kHz, however the development of a higher frequency array would enable more precision, while reducing the risk of standing waves. However, the smaller wavelength and the skull's increased distortion at this frequency are problematic. It would require an order of magnitude more elements to create such an array. Random sparse arrays enable steering of a therapeutic array with fewer elements. However, the tradeoffs inherent in the use of sparsity in a transcranial phased array have not been systematically investigated and so the objective of this simulation study is to investigate the effect of sparsity on transcranial arrays at a frequency of 1.5 MHz that provides small focal spots for precise exposure control. Methods: Transcranial sonication simulations were conducted using a multilayer Rayleigh-Sommerfeld propagation model. Element size and element population were varied and the phased array's ability to steer was assessed. Results: The focal pressures decreased proportionally as elements were removed. However, off-focus hotspots were generated if a high degree of steering was attempted with very sparse arrays. A phased array consisting of 1588 elements 3 mm in size, a 10% population, was appropriate for steering up to 4 cm in all directions. However, a higher element population would be required if near-skull sonication is desired. Conclusions: This study demonstrated that the development of a sparse, hemispherical array at 1.5 MHz could enable more precision in therapies that utilize lower intensity sonications.

  7. Analysis of phased-array diode lasers

    SciTech Connect

    Hardy, A.; Streifer, W.

    1985-07-01

    An improved, more accurate analysis of phased-array diode lasers is presented, which yields results that differ both qualitatively and quantitatively from those previously employed. A numerical example indicating decreased splitting in array mode gains is included.

  8. Density-tapered spiral arrays for ultrasound 3-D imaging.

    PubMed

    Ramalli, Alessandro; Boni, Enrico; Savoia, Alessandro Stuart; Tortoli, Piero

    2015-08-01

    The current high interest in 3-D ultrasound imaging is pushing the development of 2-D probes with a challenging number of active elements. The most popular approach to limit this number is the sparse array technique, which designs the array layout by means of complex optimization algorithms. These algorithms are typically constrained by a few steering conditions, and, as such, cannot guarantee uniform side-lobe performance at all angles. The performance may be improved by the ungridded extensions of the sparse array technique, but this result is achieved at the expense of a further complication of the optimization process. In this paper, a method to design the layout of large circular arrays with a limited number of elements according to Fermat's spiral seeds and spatial density modulation is proposed and shown to be suitable for application to 3-D ultrasound imaging. This deterministic, aperiodic, and balanced positioning procedure attempts to guarantee uniform performance over a wide range of steering angles. The capabilities of the method are demonstrated by simulating and comparing the performance of spiral and dense arrays. A good trade-off for small vessel imaging is found, e.g., in the 60λ spiral array with 1.0λ elements and Blackman density tapering window. Here, the grating lobe level is -16 dB, the lateral resolution is lower than 6λ the depth of field is 120λ and, the average contrast is 10.3 dB, while the sensitivity remains in a 5 dB range for a wide selection of steering angles. The simulation results may represent a reference guide to the design of spiral sparse array probes for different application fields.

  9. Delamination Detection Using Guided Wave Phased Arrays

    NASA Technical Reports Server (NTRS)

    Tian, Zhenhua; Yu, Lingyu; Leckey, Cara

    2016-01-01

    This paper presents a method for detecting multiple delaminations in composite laminates using non-contact phased arrays. The phased arrays are implemented with a non-contact scanning laser Doppler vibrometer (SLDV). The array imaging algorithm is performed in the frequency domain where both the guided wave dispersion effect and direction dependent wave properties are considered. By using the non-contact SLDV array with a frequency domain imaging algorithm, an intensity image of the composite plate can be generated for delamination detection. For the proof of concept, a laboratory test is performed using a non-contact phased array to detect two delaminations (created through quasi-static impact test) at different locations in a composite plate. Using the non-contact phased array and frequency domain imaging, the two impact-induced delaminations are successfully detected. This study shows that the non-contact phased array method is a potentially effective method for rapid delamination inspection in large composite structures.

  10. Cumulative phase delay imaging - A new contrast enhanced ultrasound modality

    SciTech Connect

    Demi, Libertario Sloun, Ruud J. G. van; Mischi, Massimo; Wijkstra, Hessel

    2015-10-28

    Recently, a new acoustic marker for ultrasound contrast agents (UCAs) has been introduced. A cumulative phase delay (CPD) between the second harmonic and fundamental pressure wave field components is in fact observable for ultrasound propagating through UCAs. This phenomenon is absent in the case of tissue nonlinearity and is dependent on insonating pressure and frequency, UCA concentration, and propagation path length through UCAs. In this paper, ultrasound images based on this marker are presented. The ULA-OP research platform, in combination with a LA332 linear array probe (Esaote, Firenze Italy), were used to image a gelatin phantom containing a PVC plate (used as a reflector) and a cylindrical cavity measuring 7 mm in diameter (placed in between the observation point and the PVC plate). The cavity contained a 240 µL/L SonoVueO{sup ®} UCA concentration. Two insonating frequencies (3 MHz and 2.5 MHz) were used to scan the gelatine phantom. A mechanical index MI = 0.07, measured in water at the cavity location with a HGL-0400 hydrophone (Onda, Sunnyvale, CA), was utilized. Processing the ultrasound signals backscattered from the plate, ultrasound images were generated in a tomographic fashion using the filtered back-projection method. As already observed in previous studies, significantly higher CPD values are measured when imaging at a frequency of 2.5 MHz, as compared to imaging at 3 MHz. In conclusion, these results confirm the applicability of the discussed CPD as a marker for contrast imaging. Comparison with standard contrast-enhanced ultrasound imaging modalities will be the focus of future work.

  11. Cumulative phase delay imaging - A new contrast enhanced ultrasound modality

    NASA Astrophysics Data System (ADS)

    Demi, Libertario; van Sloun, Ruud J. G.; Wijkstra, Hessel; Mischi, Massimo

    2015-10-01

    Recently, a new acoustic marker for ultrasound contrast agents (UCAs) has been introduced. A cumulative phase delay (CPD) between the second harmonic and fundamental pressure wave field components is in fact observable for ultrasound propagating through UCAs. This phenomenon is absent in the case of tissue nonlinearity and is dependent on insonating pressure and frequency, UCA concentration, and propagation path length through UCAs. In this paper, ultrasound images based on this marker are presented. The ULA-OP research platform, in combination with a LA332 linear array probe (Esaote, Firenze Italy), were used to image a gelatin phantom containing a PVC plate (used as a reflector) and a cylindrical cavity measuring 7 mm in diameter (placed in between the observation point and the PVC plate). The cavity contained a 240 µL/L SonoVueO® UCA concentration. Two insonating frequencies (3 MHz and 2.5 MHz) were used to scan the gelatine phantom. A mechanical index MI = 0.07, measured in water at the cavity location with a HGL-0400 hydrophone (Onda, Sunnyvale, CA), was utilized. Processing the ultrasound signals backscattered from the plate, ultrasound images were generated in a tomographic fashion using the filtered back-projection method. As already observed in previous studies, significantly higher CPD values are measured when imaging at a frequency of 2.5 MHz, as compared to imaging at 3 MHz. In conclusion, these results confirm the applicability of the discussed CPD as a marker for contrast imaging. Comparison with standard contrast-enhanced ultrasound imaging modalities will be the focus of future work.

  12. High Power Low Impedance Therapeutic Intracavitary Phased Array

    NASA Astrophysics Data System (ADS)

    Kukic, Aleksandra; Hynynen, Kullervo

    2010-03-01

    Ultrasound phased arrays can be used for noninvasive surgical applications, and are ideal for intracavitary applications, where their properties of dynamic focusing and beam steering compensate for the spatial constraints. Phase shifting without grating lobes requires small elements, which results in low width-thickness ratios and thus high electrical impedance. This study demonstrates, for the first time, a method of lateral coupling for the purposes of reduction of electrical impedance of linear phased arrays. Fabrication procedure for a lateral coupled array for therapeutic purposes is demonstrated. Impedance analysis of a thickness mode driven phased array is compared to a lateral coupling mode array. For a 1.5 MHz resonant frequency, impedance drop of 33 times is seen at antiresonance, and 6 times at resonance. Thickness mode phase peak is never higher than -41.3°, whereas it reaches to 42.3° in the lateral coupling mode. This allows for a phase crossing of 0° for lateral mode transducer, where the impedance is 111Ω, eliminating the need for matching circuits. Scanning laser vibrometer measurements of surface displacements show that a lateral mode element can achieve intensity levels greater than 20 W/cm2, when an unmatched element is tested.

  13. Design, development, and evaluation of focused ultrasound arrays for transesophageal cardiac ablations

    NASA Astrophysics Data System (ADS)

    Lee, Hotaik

    two-dimensional sparse phased array with flat tapered elements was found to be adequate as a transesophageal ultrasound applicator. The spatially sparse array uses 64 active elements operating at a frequency of 1.6 MHz sampled from 195 (15 by 13) rectangular elements. With this applicator, the size and position of the ablation targets can be controlled by changing the electrical power and phase to the individual elements for ultrasound beam focusing and steering. The magnetic resonance-compatible probe head housing is 19 mm in diameter and incorporates an acoustic window. For the verification of the suggested design, a prototype array with an acoustic impedance matching layer was constructed, and tested using exposimetry andex vivo experiments. Experimental results indicated that the array could focus and steer the beam with an angle within +/-10° inside the tissue. Also, the array can deliver sufficient power to the focal point to produce ablation while not damaging nearby tissue outside the target area. The results demonstrated a potential application of the ultrasound applicator to transesophageal cardiac surgery in atrial fibrillation treatment.

  14. Breast ultrasound tomography with two parallel transducer arrays: preliminary clinical results

    NASA Astrophysics Data System (ADS)

    Huang, Lianjie; Shin, Junseob; Chen, Ting; Lin, Youzuo; Intrator, Miranda; Hanson, Kenneth; Epstein, Katherine; Sandoval, Daniel; Williamson, Michael

    2015-03-01

    Ultrasound tomography has great potential to provide quantitative estimations of physical properties of breast tumors for accurate characterization of breast cancer. We design and manufacture a new synthetic-aperture breast ultrasound tomography system with two parallel transducer arrays. The distance of these two transducer arrays is adjustable for scanning breasts with different sizes. The ultrasound transducer arrays are translated vertically to scan the entire breast slice by slice and acquires ultrasound transmission and reflection data for whole-breast ultrasound imaging and tomographic reconstructions. We use the system to acquire patient data at the University of New Mexico Hospital for clinical studies. We present some preliminary imaging results of in vivo patient ultrasound data. Our preliminary clinical imaging results show promising of our breast ultrasound tomography system with two parallel transducer arrays for breast cancer imaging and characterization.

  15. A sidelobe suppressing near-field beamforming approach for ultrasound array imaging.

    PubMed

    He, Zhengyao; Zheng, Fan; Ma, Yuanliang; Kim, Hyung Ham; Zhou, Qifa; Shung, K Kirk

    2015-05-01

    A method is proposed to suppress sidelobe level for near-field beamforming in ultrasound array imaging. An optimization problem is established, and the second-order cone algorithm is used to solve the problem to obtain the weight vector based on the near-field response vector of a transducer array. The weight vector calculation results show that the proposed method can be used to suppress the sidelobe level of the near-field beam pattern of a transducer array. Ultrasound images following the application of weight vector to the array of a wire phantom are obtained by simulation with the Field II program, and the images of a wire phantom and anechoic sphere phantom are obtained experimentally with a 64-element 26 MHz linear phased array. The experimental and simulation results agree well and show that the proposed method can achieve a much lower sidelobe level than the conventional delay and sum beamforming method. The wire phantom image is demonstrated to focus much better and the contrast of the anechoic sphere phantom image improved by applying the proposed beamforming method.

  16. Multilevel phase gratings for array illuminators.

    PubMed

    Arrizón, V; Ojeda-Castañeda, J

    1994-09-01

    We describe a variety of multilevel phase structures that can be used to generate Lohmann's array illuminators. We report several experimental verifications of the synthesis of such multilevel phase structures by using simple binary curves in a conventional optical processor.

  17. Ultrasound phase rotation beamforming on multi-core DSP.

    PubMed

    Ma, Jieming; Karadayi, Kerem; Ali, Murtaza; Kim, Yongmin

    2014-01-01

    Phase rotation beamforming (PRBF) is a commonly-used digital receive beamforming technique. However, due to its high computational requirement, it has traditionally been supported by hardwired architectures, e.g., application-specific integrated circuits (ASICs) or more recently field-programmable gate arrays (FPGAs). In this study, we investigated the feasibility of supporting software-based PRBF on a multi-core DSP. To alleviate the high computing requirement, the analog front-end (AFE) chips integrating quadrature demodulation in addition to analog-to-digital conversion were defined and used. With these new AFE chips, only delay alignment and phase rotation need to be performed by DSP, substantially reducing the computational load. We implemented the delay alignment and phase rotation modules on a Texas Instruments C6678 DSP with 8 cores. We found it takes 200 μs to beamform 2048 samples from 64 channels using 2 cores. With 4 cores, 20 million samples can be beamformed in one second. Therefore, ADC frequencies up to 40 MHz with 2:1 decimation in AFE chips or up to 20 MHz with no decimation can be supported as long as the ADC-to-DSP I/O requirement can be met. The remaining 4 cores can work on back-end processing tasks and applications, e.g., color Doppler or ultrasound elastography. One DSP being able to handle both beamforming and back-end processing could lead to low-power and low-cost ultrasound machines, benefiting ultrasound imaging in general, particularly portable ultrasound machines. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Registration of human skull computed tomography data to an ultrasound treatment space using a sparse high frequency ultrasound hemispherical array.

    PubMed

    O'Reilly, Meaghan A; Jones, Ryan M; Birman, Gabriel; Hynynen, Kullervo

    2016-09-01

    Transcranial focused ultrasound (FUS) shows great promise for a range of therapeutic applications in the brain. Current clinical investigations rely on the use of magnetic resonance imaging (MRI) to monitor treatments and for the registration of preoperative computed tomography (CT)-data to the MR images at the time of treatment to correct the sound aberrations caused by the skull. For some applications, MRI is not an appropriate choice for therapy monitoring and its cost may limit the accessibility of these treatments. An alternative approach, using high frequency ultrasound measurements to localize the skull surface and register CT data to the ultrasound treatment space, for the purposes of skull-related phase aberration correction and treatment targeting, has been developed. A prototype high frequency, hemispherical sparse array was fabricated. Pulse-echo measurements of the surface of five ex vivo human skulls were made, and the CT datasets of each skull were obtained. The acoustic data were used to rigidly register the CT-derived skull surface to the treatment space. The ultrasound-based registrations of the CT datasets were compared to the gold-standard landmark-based registrations. The results show on an average sub-millimeter (0.9 ± 0.2 mm) displacement and subdegree (0.8° ± 0.4°) rotation registration errors. Numerical simulations predict that registration errors on this scale will result in a mean targeting error of 1.0 ± 0.2 mm and reduction in focal pressure of 1.0% ± 0.6% when targeting a midbrain structure (e.g., hippocampus) using a commercially available low-frequency brain prototype device (InSightec, 230 kHz brain system). If combined with ultrasound-based treatment monitoring techniques, this registration method could allow for the development of a low-cost transcranial FUS treatment platform to make this technology more widely available.

  19. An experimental X band phased array

    NASA Astrophysics Data System (ADS)

    Rao, N. P. R.; Limaye, K. U.; Ramalingam, R. P.; Gangadharan, T. S.; Bhandopadhyay, G.; Deshpande, P. A.

    1983-10-01

    The details of an X band experimental 11 x 11 element Phased Array Antenna of phased lens configuration with a monopulse space feed developed at LRDE are presented. The studies carried and the results obtained on collimation, beam steering, pattern variation with scan, array operation in two-dimensional search, dedicated track and track while scan (TWS) are also given.

  20. Quantitative ultrasonic phased array imaging

    NASA Astrophysics Data System (ADS)

    Engle, Brady J.; Schmerr, Lester W., Jr.; Sedov, Alexander

    2014-02-01

    When imaging with ultrasonic phased arrays, what do we actually image? What quantitative information is contained in the image? Ad-hoc delay-and-sum methods such as the synthetic aperture focusing technique (SAFT) and the total focusing method (TFM) fail to answer these questions. We have shown that a new quantitative approach allows the formation of flaw images by explicitly inverting the Thompson-Gray measurement model. To examine the above questions, we have set up a software simulation test bed that considers a 2-D scalar scattering problem of a cylindrical inclusion with the method of separation of variables. It is shown that in SAFT types of imaging the only part of the flaw properly imaged is the front surface specular response of the flaw. Other responses (back surface reflections, creeping waves, etc.) are improperly imaged and form artifacts in the image. In the case of TFM-like imaging the quantity being properly imaged is an angular integration of the front surface reflectivity. The other, improperly imaged responses are also averaged, leading to a reduction in some of the artifacts present. Our results have strong implications for flaw sizing and flaw characterization with delay-and-sum images.

  1. Large phased-array radars

    SciTech Connect

    Brookner, D.E.

    1988-12-15

    Large phased-array radars can play a very important part in arms control. They can be used to determine the number of RVs being deployed, the type of targeting of the RVs (the same or different targets), the shape of the deployed objects, and possibly the weight and yields of the deployed RVs. They can provide this information at night as well as during the day and during rain and cloud covered conditions. The radar can be on the ground, on a ship, in an airplane, or space-borne. Airborne and space-borne radars can provide high resolution map images of the ground for reconnaissance, of anti-ballistic missile (ABM) ground radar installations, missile launch sites, and tactical targets such as trucks and tanks. The large ground based radars can have microwave carrier frequencies or be at HF (high frequency). For a ground-based HF radar the signal is reflected off the ionosphere so as to provide over-the-horizon (OTH) viewing of targets. OTH radars can potentially be used to monitor stealth targets and missile traffic.

  2. Large phased-array radars

    NASA Astrophysics Data System (ADS)

    Brookner, Eli, Dr.

    1988-12-01

    Large phased-array radars can play a very important part in arms control. They can be used to determine the number of RVs being deployed, the type of targeting of the RVs (the same or different targets), the shape of the deployed objects, and possibly the weight and yields of the deployed RVs. They can provide this information at night as well as during the day and during rain and cloud covered conditions. The radar can be on the ground, on a ship, in an airplane, or space-borne. Airborne and space-borne radars can provide high resolution map images of the ground for reconnaissance, of anti-ballistic missile (ABM) ground radar installations, missile launch sites, and tactical targets such as trucks and tanks. The large ground based radars can have microwave carrier frequencies or be at HF (high frequency). For a ground-based HF radar the signal is reflected off the ionosphere so as to provide over-the-horizon (OTH) viewing of targets. OTH radars can potentially be used to monitor stealth targets and missile traffic.

  3. Two-dimensional ultrasound receive array using an angle-tuned Fabry-Perot polymer film sensor for transducer field characterization and transmission ultrasound imaging.

    PubMed

    Beard, Paul Christopher

    2005-06-01

    A 2-D optical ultrasound receive array has been investigated. The transduction mechanism is based upon the detection of acoustically induced changes in the optical thickness of a thin polymer film acting as a Fabry-Perot sensing interferometer (FPI). By illuminating the sensor with a large-area laser beam and mechanically scanning a photodiode across the reflected output beam, while using a novel angle-tuned phase bias control system to optimally set the FPI working point, a notional 2-D ultrasound array was synthesized. To demonstrate the concept, 1-D and 2-D ultrasound field distributions produced by planar 3.5-MHz and focused 5-MHz PZT ultrasound transducers were mapped. The system was also evaluated by performing transmission ultrasound imaging of a spatially calibrated target. The "array" aperture, defined by the dimensions of the incident optical field, was elliptical, of dimensions 16 x 12 mm and spatially sampled in steps of 0.1 mm or 0.2 mm. Element sizes, defined by the photodiode aperture, of 0.8, 0.4, and 0.2 mm were variously used for these experiments. Two types of sensor were evaluated. One was a discrete 75-microm-thick polyethylene terephthalate FPI bonded to a polymer backing stub which had a wideband peak noise-equivalent pressure of 6.5 kPa and an acoustic bandwidth 12 MHz. The other was a 40-microm Parylene film FPI which was directly vacuum-deposited onto a glass backing stub and had an NEP of 8 kPa and an acoustic bandwidth of 17.5 MHz. It is considered that this approach offers an alternative to piezoelectric ultrasound arrays for transducer field characterization, transmission medical and industrial ultrasound imaging, biomedical photoacoustic imaging, and ultrasonic nondestructive testing.

  4. Phased Array Inspection of Irregular Surfaces

    NASA Astrophysics Data System (ADS)

    Long, R.; Cawley, P.

    2007-03-01

    The purpose of this project is to research and develop new conformable phased arrays that allow reliable ultrasonic inspection of components with an irregular surface. Two alternative approaches have been considered: flexible contact arrays in which the array itself conforms to the surface and a membrane device in which a standard array is coupled to the surface via a fluid-filled membrane. A linear flexible contact phased array was purchased from CEA France and a conformable membrane device was designed and manufactured at Imperial College. Initial investigations were conducted to evaluate both approaches when coupling to test pieces with machined surfaces representative of typical welded pipes without removal of the weld caps. The research incorporated beam modelling using the CEA CIVA software and comparisons with experimental measurements. It is shown that the conformable membrane approach using a standard array transducer is competitive with the bespoke flexible array.

  5. Airborne Electronically Steerable Phased Array (AESPA) program

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The basic concept and design of a flatplate-fed transmission array are described and system performance requirements are summarized. Particular emphasis is given to the design of the aperture, the radiating element, the phase shifter, the flatplate feed, and the mechanical support structure. Fabrication and testing techniques are considered. Of the three major parameters of interest in demonstrating the performance capabilities of the transmissive array, beamwidth was shown to be the least sensitive to system amplitude and phase errors. Beam pointing angle was also shown to be relatively insensitive to errors. Close agreement between measured and calculated values was found for array gain. The greatest difference was found for array sidelone level.

  6. Phased-Antenna-Array Conical Scanning

    NASA Technical Reports Server (NTRS)

    Lesh, J. R.

    1984-01-01

    Antenna pointing faster than mechanical scanning. Three antenna phased array connected to receiving signal-processing system through two phase-shifting networks. Two networks simultaneously steer phased array in two slightly-different beam directions; one for scanning, one for tracking. Technique has many uses in military and civilian radar, principally in tracking aircraft, balloonborne weather instruments, and other moving signal sources or reflectors.

  7. Photoacoustic-guided ultrasound therapy with a dual-mode ultrasound array.

    PubMed

    Prost, Amaury; Funke, Arik; Tanter, Mickaël; Aubry, Jean-François; Bossy, Emmanuel

    2012-06-01

    Photoacoustics has recently been proposed as a potential method to guide and/or monitor therapy based on high-intensity focused ultrasound (HIFU). We experimentally demonstrate the creation of a HIFU lesion at the location of an optical absorber, by use of photoacoustic signals emitted by the absorber detected on a dual mode transducer array. To do so, a dedicated ultrasound array intended to both detect photoacoustic waves and emit HIFU with the same elements was used. Such a dual-mode array provides automatically coregistered reference frames for photoacoustic detection and HIFU emission, a highly desired feature for methods involving guidance or monitoring of HIFU by use of photoacoustics. The prototype is first characterized in terms of both photoacoustic and HIFU performances. The probe is then used to perform an idealized scenario of photoacoustic-guided therapy, where photoacoustic signals generated by an absorbing thread embedded in a piece of chicken breast are used to automatically refocus a HIFU beam with a time-reversal mirror and necrose the tissue at the location of the absorber.

  8. Photoacoustic-guided ultrasound therapy with a dual-mode ultrasound array

    NASA Astrophysics Data System (ADS)

    Prost, Amaury; Funke, Arik; Tanter, Mickaël; Aubry, Jean-François; Bossy, Emmanuel

    2012-06-01

    Photoacoustics has recently been proposed as a potential method to guide and/or monitor therapy based on high-intensity focused ultrasound (HIFU). We experimentally demonstrate the creation of a HIFU lesion at the location of an optical absorber, by use of photoacoustic signals emitted by the absorber detected on a dual mode transducer array. To do so, a dedicated ultrasound array intended to both detect photoacoustic waves and emit HIFU with the same elements was used. Such a dual-mode array provides automatically coregistered reference frames for photoacoustic detection and HIFU emission, a highly desired feature for methods involving guidance or monitoring of HIFU by use of photoacoustics. The prototype is first characterized in terms of both photoacoustic and HIFU performances. The probe is then used to perform an idealized scenario of photoacoustic-guided therapy, where photoacoustic signals generated by an absorbing thread embedded in a piece of chicken breast are used to automatically refocus a HIFU beam with a time-reversal mirror and necrose the tissue at the location of the absorber.

  9. Large-scale nanophotonic phased array.

    PubMed

    Sun, Jie; Timurdogan, Erman; Yaacobi, Ami; Hosseini, Ehsan Shah; Watts, Michael R

    2013-01-10

    Electromagnetic phased arrays at radio frequencies are well known and have enabled applications ranging from communications to radar, broadcasting and astronomy. The ability to generate arbitrary radiation patterns with large-scale phased arrays has long been pursued. Although it is extremely expensive and cumbersome to deploy large-scale radiofrequency phased arrays, optical phased arrays have a unique advantage in that the much shorter optical wavelength holds promise for large-scale integration. However, the short optical wavelength also imposes stringent requirements on fabrication. As a consequence, although optical phased arrays have been studied with various platforms and recently with chip-scale nanophotonics, all of the demonstrations so far are restricted to one-dimensional or small-scale two-dimensional arrays. Here we report the demonstration of a large-scale two-dimensional nanophotonic phased array (NPA), in which 64 × 64 (4,096) optical nanoantennas are densely integrated on a silicon chip within a footprint of 576 μm × 576 μm with all of the nanoantennas precisely balanced in power and aligned in phase to generate a designed, sophisticated radiation pattern in the far field. We also show that active phase tunability can be realized in the proposed NPA by demonstrating dynamic beam steering and shaping with an 8 × 8 array. This work demonstrates that a robust design, together with state-of-the-art complementary metal-oxide-semiconductor technology, allows large-scale NPAs to be implemented on compact and inexpensive nanophotonic chips. In turn, this enables arbitrary radiation pattern generation using NPAs and therefore extends the functionalities of phased arrays beyond conventional beam focusing and steering, opening up possibilities for large-scale deployment in applications such as communication, laser detection and ranging, three-dimensional holography and biomedical sciences, to name just a few.

  10. MR thermometry characterization of a hyperthermia ultrasound array designed using the k-space computational method

    PubMed Central

    Al-Bataineh, Osama M; Collins, Christopher M; Park, Eun-Joo; Lee, Hotaik; Smith, Nadine Barrie

    2006-01-01

    Background Ultrasound induced hyperthermia is a useful adjuvant to radiation therapy in the treatment of prostate cancer. A uniform thermal dose (43°C for 30 minutes) is required within the targeted cancerous volume for effective therapy. This requires specific ultrasound phased array design and appropriate thermometry method. Inhomogeneous, acoustical, three-dimensional (3D) prostate models and economical computational methods provide necessary tools to predict the appropriate shape of hyperthermia phased arrays for better focusing. This research utilizes the k-space computational method and a 3D human prostate model to design an intracavitary ultrasound probe for hyperthermia treatment of prostate cancer. Evaluation of the probe includes ex vivo and in vivo controlled hyperthermia experiments using the noninvasive magnetic resonance imaging (MRI) thermometry. Methods A 3D acoustical prostate model was created using photographic data from the Visible Human Project®. The k-space computational method was used on this coarse grid and inhomogeneous tissue model to simulate the steady state pressure wavefield of the designed phased array using the linear acoustic wave equation. To ensure the uniformity and spread of the pressure in the length of the array, and the focusing capability in the width of the array, the equally-sized elements of the 4 × 20 elements phased array were 1 × 14 mm. A probe was constructed according to the design in simulation using lead zerconate titanate (PZT-8) ceramic and a Delrin® plastic housing. Noninvasive MRI thermometry and a switching feedback controller were used to accomplish ex vivo and in vivo hyperthermia evaluations of the probe. Results Both exposimetry and k-space simulation results demonstrated acceptable agreement within 9%. With a desired temperature plateau of 43.0°C, ex vivo and in vivo controlled hyperthermia experiments showed that the MRI temperature at the steady state was 42.9 ± 0.38°C and 43.1 ± 0.80

  11. Phased Array Ultrasonic Inspection of Titanium Forgings

    SciTech Connect

    Howard, P.; Klaassen, R.; Kurkcu, N.; Barshinger, J.; Chalek, C.; Nieters, E.; Sun, Zongqi; Fromont, F. de

    2007-03-21

    Aerospace forging inspections typically use multiple, subsurface-focused sound beams in combination with digital C-scan image acquisition and display. Traditionally, forging inspections have been implemented using multiple single element, fixed focused transducers. Recent advances in phased array technology have made it possible to perform an equivalent inspection using a single phased array transducer. General Electric has developed a system to perform titanium forging inspection based on medical phased array technology and advanced image processing techniques. The components of that system and system performance for titanium inspection will be discussed.

  12. A Nonlinear Lumped Model for Ultrasound Systems Using CMUT Arrays

    PubMed Central

    Satir, Sarp; Degertekin, F. Levent

    2015-01-01

    We present a nonlinear lumped model that predicts the electrical input-output behavior of an ultrasonic system using CMUTs with arbitrary array/membrane/electrode geometry in different transmit-receive configurations and drive signals. The receive-only operation, where the electrical output signal of the CMUT array in response to incident pressure field is calculated, is included by modifying the boundary element based vibroacoustic formulation for a CMUT array in rigid baffle. Along with the accurate large signal transmit model, this formulation covers pitch-catch and pulse-echo operation when transmit and receive signals can be separated in time. In cases when this separation is not valid, such as CMUTs used in continuous wave transmit-receive mode, pulse-echo mode with a nearby hard or soft wall or in a bounded space such as in a microfluidic channel, an efficient formulation based on the method of images is used. Some of these particular applications and the overall modeling approach have been validated through comparison with finite element analysis on specific examples including CMUTs with multiple electrodes. To further demonstrate the capability of the model for imaging applications, the two-way response of a partial dual-ring intravascular ultrasound array is simulated using a parallel computing cluster, where the output currents of individual array elements are calculated for given input pulse and compared with experimental results. With its versatility, the presented model can be a useful tool for rapid iterative CMUT-based system design and simulation for a broad range of ultrasonic applications. PMID:26470049

  13. A nonlinear lumped model for ultrasound systems using CMUT arrays.

    PubMed

    Satir, Sarp; Degertekin, F Levent

    2015-10-01

    We present a nonlinear lumped model that predicts the electrical input-output behavior of an ultrasonic system using CMUTs with arbitrary array/membrane/electrode geometry in different transmit-receive configurations and drive signals. The receive-only operation, where the electrical output signal of the CMUT array in response to incident pressure field is calculated, is included by modifying the boundary elementbased vibroacoustic formulation for a CMUT array in rigid baffle. Along with the accurate large signal transmit model, this formulation covers pitch-catch and pulse-echo operation when transmit and receive signals can be separated in time. In cases when this separation is not valid, such as CMUTs used in continuous wave transmit-receive mode, pulse-echo mode with a nearby hard or soft wall or in a bounded space such as in a microfluidic channel, an efficient formulation based on the method of images is used. Some of these particular applications and the overall modeling approach have been validated through comparison with finite element analysis on specific examples including CMUTs with multiple electrodes. To further demonstrate the capability of the model for imaging applications, the two-way response of a partial dual-ring intravascular ultrasound array is simulated using a parallel computing cluster, where the output currents of individual array elements are calculated for given input pulse and compared with experimental results. With its versatility, the presented model can be a useful tool for rapid iterative CMUT-based system design and simulation for a broad range of ultrasonic applications.

  14. Phased-array radar for airborne systems

    NASA Astrophysics Data System (ADS)

    Tahim, Raghbir S.; Foshee, James J.; Chang, Kai

    2003-09-01

    Phased array antenna systems, which support high pulse rates and high transmit power, are well suited for radar and large-scale surveillance. Sensors and communication systems can function as the eyes and ears for ballistic missile defense applications, providing early warning of attack, target detection and identification, target tracking, and countermeasure decision. In such applications, active array radar systems that contain solid-state transmitter sources and low-noise preamplifiers for transmission and reception are preferred over the conventional radar antennas, because the phased array radar offers the advantages of power management and efficiency, reliability, signal reception, beam steering target detection. The current phased array radar designs are very large, complex and expensive and less efficient because of high RF losses in the phase control circuits used for beam scan. Several thousands of phase shifters and drivers may be required for a single system thus making the system very complex and expensive. This paper describes the phased array radar system based on high power T/R modules, wide-band radiating planar antenna elements and very low loss wide-band phase control circuits (requiring reduced power levels) for beam scan. The phase shifter design is based on micro-strip feed lines perturbed by the proximity of voltage controlled piezoelectric transducer (PET). Measured results have shown an added insertion loss of less than 1 dB for a phase shift of 450 degrees from 2 to 20 GHz. The new wideband phased array radar design provides significant reduction in size cost and weight. Compared to the conventional phased array systems, the cost saving is more than 15 to 1.

  15. Coplanar waveguide fed phased array antenna

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Ponchak, George E.; Lee, R. Q.; Fernandez, N. S.

    1990-01-01

    A K-band four element linear phased array was designed and tested. Coplanar waveguide (CPW) is used for the microwave distribution system. A CPW to twin strip transition is used to interface with the printed dipole antennas. MMIC phased shifters are used for phase control.

  16. Theory and operation of 2-D array piezoelectric micromachined ultrasound transducers.

    PubMed

    Dausch, David E; Castellucci, John B; Chou, Derrick R; von Ramm, Olaf T

    2008-11-01

    Piezoelectric micromachined ultrasound transducers (pMUTs) are a new approach for the construction of 2-D arrays for forward-looking 3-D intravascular (IVUS) and intracardiac (ICE) imaging. Two-dimensional pMUT test arrays containing 25 elements (5 x 5 arrays) were bulk micromachined in silicon substrates. The devices consisted of lead zirconate titanate (PZT) thin film membranes formed by deep reactive ion etching of the silicon substrate. Element widths ranged from 50 to 200 microm with pitch from 100 to 300 mum. Acoustic transmit properties were measured in de-ionized water with a calibrated hydrophone placed at a range of 20 mm. Measured transmit frequencies for the pMUT elements ranged from 4 to 13 MHz, and mode of vibration differed for the various element sizes. Element capacitance varied from 30 to over 400 pF depending on element size and PZT thickness. Smaller element sizes generally produced higher acoustic transmit output as well as higher frequency than larger elements. Thicker PZT layers also produced higher transmit output per unit electric field applied. Due to flexure mode operation above the PZT coercive voltage, transmit output increased nonlinearly with increased drive voltage. The pMUT arrays were attached directly to the Duke University T5 Phased Array Scanner to produce real-time pulse-echo B-mode images with the 2-D pMUT arrays.

  17. Optimization of acoustic emitted field of transducer array for ultrasound imaging.

    PubMed

    He, Zhengyao

    2014-01-01

    A method is proposed to calculate the weight vector of a transducer array for ultrasound imaging to obtain a low-sidelobe transmitting beam pattern based on the near-field response vector. An optimization problem is established, and the second-order cone (SOC) algorithm is used to solve the problem to obtain the weight vector. The optimized acoustic emitted field of the transducer array is then calculated using the Field II program by applying the obtained weight vector to the array. The simulation results with a 64-element 26 MHz linear phased array show that the proposed method can be used to control the sidelobe of the near-field transmitting beam pattern of the transducer array and achieve a low-sidelobe level. The near-field sound pressure distribution of the transducer array using the proposed method focuses much better than that using the standard delay and sum (DAS) beamforming method. The sound energy is more concentrated using the proposed method.

  18. A phased array tracking antenna for vehicles

    NASA Technical Reports Server (NTRS)

    Ohmori, Shingo; Mano, Kazukiko; Tanaka, Kenji; Matsunaga, Makoto; Tsuchiya, Makio

    1990-01-01

    An antenna system including antenna elements and a satellite tracking method is considered a key technology in implementing land mobile satellite communications. In the early stage of land mobile satellite communications, a mechanical tracking antenna system is considered the best candidate for vehicles, however, a phased array antenna will replace it in the near future, because it has many attractive advantages such as a low and compact profile, high speed tracking, and potential low cost. Communications Research Laboratory is now developing a new phased array antenna system for land vehicles based on research experiences of the airborne phased array antenna, which was developed and evaluated in satellite communication experiments using the ETS-V satellite. The basic characteristics of the phased array antenna for land vehicles are described.

  19. Segmented-mirror phased-array lasers

    SciTech Connect

    De Silvestri, S.; Laporta, P.; Magni, V.; Svelto, O.

    1987-11-30

    A scheme for phase-locked laser arrays in both one- and two-dimensional configurations is discussed. The scheme can be applied to any laser and its validity has been proved for the case of a pulsed neodimium laser.

  20. Thin catheter bending in the direction perpendicular to ultrasound propagation using two-dimensional array transducer

    NASA Astrophysics Data System (ADS)

    Suzuki, Toshiya; Mochizuki, Takashi; Ushimizu, Hidetaka; Miyazawa, Shinya; Tsurui, Nobuhiro; Masuda, Kohji

    2017-07-01

    Although we have already experimented on the bending of a thin catheter with acoustic radiation force using a single transducer, it is necessary to develop a method of bending a catheter in an arbitrary direction because the installation position of ultrasound transducers on a body surface is limited for application to various shapes of in vivo blood vessels. Therefore, we examined the bending of a thin catheter in the direction perpendicular to ultrasound propagation using a two-dimensional array transducer (1 MHz), which realizes not only the temporospatial design but also the dynamic variation of acoustic fields. Forming two focal points with opposite phases, where the amplitudes of the two points instantaneously have the positive and negative relationship, we confirmed the bending of a thin catheter in the direction perpendicular to ultrasound propagation. We used a thin catheter (diameter, 200 µm length, 50 mm) to obtain the maximum displacement of 220 µm, where the displacement was proportional to the square of the maximum sound pressure and the duty ratio. From these results, the acoustic energy densities observed in front of and behind the catheter are dominant for the bending of the thin catheter independent of ultrasound propagation. We also found that the distance between two focal points may improve the bending performance without requiring a precise position setting.

  1. Fundamental Limitations of Phased Array Antenna Elements

    DTIC Science & Technology

    2015-12-15

    Radiation Q of InfinitePlanar Dipole Phased Arrays, IEEE Transactions on Antennas and Propagation, (01 2014): 153. doi: Yong Heui Cho, Do-Hoon Kwon...element bandwidth bounds were found in terms of the strengths of the induced electric and magnetic dipole moments, taking into account of the coupling...Distribution Unlimited UU UU UU UU 15-12-2015 1-Oct-2012 30-Sep-2015 Final Report: Fundamental Limitations of Phased Array Antenna Elements The views

  2. Phase interpolation circuits using frequency multiplication for phased arrays

    NASA Technical Reports Server (NTRS)

    Caron, P. R.; Mailloux, R. J.

    1970-01-01

    Antenna phasing circuit is described with the following advantages - 1/ increased number of phased elements, 2/ current repetition for each array element, 3/ circuit simplicity, and 4/ accurate phase interpolation. This circuit functions with Huggins Scan or with nearly any other phasing system.

  3. Nonlinear ultrasonic phased array imaging.

    PubMed

    Potter, J N; Croxford, A J; Wilcox, P D

    2014-10-03

    This Letter reports a technique for the imaging of acoustic nonlinearity. By contrasting the energy of the diffuse field produced through the focusing of an ultrasonic array by delayed parallel element transmission with that produced by postprocessing of sequential transmission data, acoustic nonlinearity local to the focal point is measured. Spatially isolated wave distortion is inferred without requiring interrogation of the wave at the inspection point, thereby allowing nonlinear imaging through depth.

  4. Nonlinear Ultrasonic Phased Array Imaging

    NASA Astrophysics Data System (ADS)

    Potter, J. N.; Croxford, A. J.; Wilcox, P. D.

    2014-10-01

    This Letter reports a technique for the imaging of acoustic nonlinearity. By contrasting the energy of the diffuse field produced through the focusing of an ultrasonic array by delayed parallel element transmission with that produced by postprocessing of sequential transmission data, acoustic nonlinearity local to the focal point is measured. Spatially isolated wave distortion is inferred without requiring interrogation of the wave at the inspection point, thereby allowing nonlinear imaging through depth.

  5. Monitoring techniques for phased-array antennas

    NASA Astrophysics Data System (ADS)

    Ronen, J.; Clarke, R. H.

    1985-12-01

    The problem of monitoring phased-array antennas in general and microwave landing system (MLS) in particular is considered. Various methods of monitoring phased-array antennas are suggested. One is based on changes in the far field radiation pattern arising from defects in the array. Another method uses the near-field to far-field transformation, based on the concept of the plane-wave spectrum, for the detection of defects in the antenna. A third method is based on near-field measurements and uses the properties of the Fresnel integral. The methods were simulated on the computer and, where possible, were tested by experiment. A comparative assessment of the methods is given, and an operational monitoring system is suggested for the MLS phased array.

  6. Pulse-Echo Phased Array Ultrasonic Inspection of Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS)

    NASA Technical Reports Server (NTRS)

    Johnston, Pat H.

    2010-01-01

    A PRSEUS test article was subjected to controlled impact on the skin face followed by static and cyclic axial compressions. Phased array ultrasonic inspection was conducted before impact, and after each of the test conditions. A linear phased array probe with a manual X-Y scanner was used for interrogation. Ultrasound showed a delamination between the skin and stringer flange adjacent to the impact. As designed, the stitching in the flange arrested the lateral flaw formation. Subsequent ultrasonic data showed no delamination growth due to continued loading. Keywords: Phased Array, Ultrasonics, Composites, Out-of-Autoclave

  7. Phased Array Inspection of Titanium Disk Forgings Targeting no. 1/2 FBH Sensitivity

    SciTech Connect

    Roberts, R.A.; Friedl, J.

    2005-04-09

    The phased array implementation of a focused zoned ultrasonic inspection to achieve a >3dB signal-to-noise for no. 1/2 flat bottom holes (FBH) in titanium is reported. Previous work established the ultrasound focusing required to achieve the targeted sensitivity. This work reports on the design of a phased array transducer capable of maintaining the needed focus to the depths required in the forging inspection. The performance of the phased array inspection is verified by examining signal-to-noise of no. 1/2 FBHs contained in coupons cut from actual forgings.

  8. Automated Array Assembly, Phase 2

    NASA Technical Reports Server (NTRS)

    Daiello, R. V.

    1978-01-01

    The purpose of the overall program is to establish technological readiness and provide verification for the elements of a manufacturing sequence which would ultimately be suitable for the large-scale production of silicon solar-array modules at a selling price of less than $500/kW. A program and process plan for accomplishing this objective was developed and put into operation. Three junction-formation processes are shown; since cost analysis shows that they do not differ greatly in cost, each should be considered for technical merits and possible future cost reduction. The progress made in the various process steps of the plan is described, and conclusions are presented.

  9. The Norwegian Seismic Array (NORSAR). Phase 3

    DTIC Science & Technology

    1983-06-01

    NORSAR Phase 3 N-2007 Kieller- Norway ii CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE AFTAC/HQ/TGX h1no 1ORA Patrick AFB 13. NUMBER OF PAGES FL...Project Manager Frode Ringdal (02) 71 69 15 Title of Work The Norwegian Seismic Array (NORSAR) Phase 3 Amount of Contract $4.762.383 Contract Period Covered...one in the center. This gives an array of aperture about 4.45 km. For high-frequency phases ( 3 Hz and above) the outer ring does not contribute to

  10. Norwegian Seismic Array (NORSAR) Phase 3

    DTIC Science & Technology

    1976-07-23

    PAGE 1 REPORT NUMBER F08606-76-C-0001 2. GOVT ACCESSION NO 4. TITLE (end Subtitle) rsir Report" Norwegian Seismic Array (N<$SSAR) Phase 3 # 7...34 CONTRACT OR GRANT NUMBERf») Ftf86^6-76-C-##l, 10. PROGRAM ELEMENT, PROJECT, TASK AREA • JORK UNIT NUMBERS NORSAR Phase 3 23 Ju IS...0001 Nils Mar&s (02) 71 69 15 Norwegian Seismic Array (NORSAR) Phase 3 $800 000 1 January 1976 - 30 June 1976 The views and conclusions

  11. RADIATION CHARACTERISTICS OF A GENERALIZED PHASED ARRAY

    NASA Technical Reports Server (NTRS)

    Acosta, R. J.

    1994-01-01

    The phased array has become a key component in the design of advanced antenna systems. This computer program was developed to examine the radiation characteristics of a generalized phased array antenna. Using a very efficient numerical technique, this program calculates the array's radiated power and its directivity. The results can be used to determine the radiation pattern of a generalized phased array at near- or far-field observation points. This program is a key research tool at the NASA Lewis Research Center for analyzing advanced space communication antenna systems. Results from this program compare favorably with experimental Lewis results for arrays of 2x2 and 3x3 elements. Given the array geometry and element characteristics, generalized phased array attributes can be broken into two areas: 1) the power radiated and its directivity at any given point, and 2) the co- and cross-polarization field components. This program allows arbitrarily located source elements with an analytically described cosine pattern. The formulation is based on a Romberg integration scheme and takes into account arbitrary element polarization, E and H plane element patterns, and mutual coupling. The input consists of the array geometry; phase, amplitude, linear and circular polarization of each source element; and the cosine functions of the element pattern. The output is a series of observation angles with their associated field magnitude and polarizations. Total radiated power and peak directivity are also calculated. This program is written in FORTRAN IV for batch execution and has been implemented on an IBM 370 computer operating under TSS with a central memory requirement of approximately 22K of 8 bit bytes. The IBM Scientific Subroutine Package (SSP) is required to run the program. This program was developed in 1986.

  12. Optical signal processing of phased array radar

    NASA Astrophysics Data System (ADS)

    Weverka, Robert T.

    This thesis develops optical processors that scale to very high processing speed. Optical signal processing is often promoted on the basis of smaller size, lower weight and lower power consumption as well as higher signal processing speed. While each of these requirements has applications, it is the ones that require processing speed beyond that available in electronics that are most compelling. Thirty years ago, optical processing was the only method fast enough to process Synthetic Aperture Radar (SAR), one of the more demanding signal processing tasks at this time. Since that time electronic processing speed has improved sufficiently to tackle that problem. We have sought out the problems that require significantly higher processing speed and developed optical processors that tackle these more difficult problems. The components that contribute to high signal processing speed are high input signal bandwidth, a large number of parallel input channels each with this high bandwidth, and a large number of parallel operations required on each input channel. Adaptive signal processing for phased array radar has all of these factors. The processors developed for this task scale well in three dimensions, which allows them to maximize parallelism for high speed. This thesis explores an example of a negative feedback adaptive phased array processor and an example of a positive feedback phased array processor. The negative feedback processor uses and array of inputs in up to two dimensions together with the time history of the signal in the third dimension to adapt the array pattern to null out incoming jammer signals. The positive feedback processor uses the incoming signals and assumptions about the radar scene to correct for position errors in a phased array. Discovery and analysis of these new processors are facilitated by an original volume holographic analysis technique developed in the thesis. The thesis includes a new acoustooptic Bragg cell geometry developed with

  13. Transmission and reflective ultrasound images using PE-CMOS sensor array

    NASA Astrophysics Data System (ADS)

    Lo, Shih-Chung B.; Liu, Chu Chuan; Freedman, Matthew T.; Kula, John; Lasser, Bob; Lasser, Marvin E.; Wang, Yue

    2005-04-01

    The purpose of this study is to investigate the imaging capability of a CMOS (PE-CMOS) ultrasound sensing array coated with piezoelectric material. There are three main components in the laboratory setup: (1) a transducer operated at 3.5MHz-7MHz frequency generating unfocused ultrasound plane waves, (2) an acoustic compound lens that collects the energy and focuses ultrasound signals onto the detector array, and (3) a PE-CMOS ultrasound sensing array (Model I400, Imperium Inc. Silver Spring, MD) that receives the ultrasound and converts the energy to analog voltage followed by a digital conversion. The PE-CMOS array consists of 128×128 pixel elements with 85μm per pixel. The major improvement of the new ultrasound sensor array has been in its dynamic range. We found that the current PE-CMOS ultrasound sensor (Model I400) possesses a dynamic range up to 70dB. The system can generate ultrasound attenuation images of soft tissues which are similar to digital images obtained from an x-ray projection system. In the paper, we also show that the prototype system can image bone fractures using reflective geometry.

  14. Array Phase Shifters: Theory and Technology

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R.

    2007-01-01

    While there are a myriad of applications for microwave phase shifters in instrumentation and metrology, power combining, amplifier linearization, and so on, the most prevalent use is in scanning phased-array antennas. And while this market continues to be dominated by military radar and tracking platforms, many commercial applications have emerged in the past decade or so. These new and potential applications span low-Earth-orbit (LEO) communications satellite constellations and collision warning radar, an aspect of the Intelligent Vehicle Highway System or Automated Highway System. In any case, the phase shifters represent a considerable portion of the overall antenna cost, with some estimates approaching 40 percent for receive arrays. Ferrite phase shifters continue to be the workhorse in military-phased arrays, and while there have been advances in thin film ferrite devices, the review of this device technology in the previous edition of this book is still highly relevant. This chapter will focus on three types of phase shifters that have matured in the past decade: GaAs MESFET monolithic microwave integrated circuit (MMIC), micro-electromechanical systems (MEMS), and thin film ferroelectric-based devices. A brief review of some novel devices including thin film ferrite phase shifters and superconducting switches for phase shifter applications will be provided. Finally, the effects of modulo 2 phase shift limitations, phase errors, and transient response on bit error rate degradation will be considered.

  15. Quantum Phase Transition in Josephson Junction Arrays

    NASA Astrophysics Data System (ADS)

    Moon, K.; Girvin, S. M.

    1997-03-01

    One-dimensional Josephson junction arrays of SQUIDS exhibit a novel superconductor-insulator phase transition. The critical regime can be accessed by tuning the effective Josephson coupling energy using a weak magnetic field applied to the SQUIDS. The role of instantons induced by quantum fluctuations will be discussed. One novel feature of these systems which can be explained in terms of quantum phase slips is that in some regimes, the array resistance decreases with increasing length of the array. We calculate the finite temperature crossover function for the array resistance and compare our theoretical results with the recent experiments by D. Haviland and P. Delsing at Chalmers. This work is supported by DOE grant #DE-FG02-90ER45427 and by NSF DMR-9502555.

  16. The Norwegian Seismic Array (NORSAR). Phase 3

    DTIC Science & Technology

    1978-10-31

    Seismic Array (NOFSAR). Phase 3 . •■I11 111 s . ,„-,, , ■ , s m^ib^^ ^Ciiv .TlW VJ 7 APPROVED FOR PUBLIC RELEASE. DISTRIBUTION UNUMfflEO...N-2007 Kjeller, Norway 10. PROGRAM ELEMENT, PROJECT. TASK AREA & WORK UNIT NUMBERS Norsar Phase 3 11. CONTROLLING OFFICE NAME AND ADDRESS 12...NORSAR) Phase 3 $520,000 ^: The views and conclusions contained in this document are those of the authors and should not be interpreted as

  17. Phase Noise in Photonic Phased-Array Antenna Systems

    NASA Technical Reports Server (NTRS)

    Logan, Ronald T., Jr.; Maleki, Lute

    1998-01-01

    The total noise of a phased-array antenna system employing a photonic feed network is analyzed using a model for the individual component noise including both additive and multiplicative equivalent noise generators.

  18. Adaptive lesion formation using dual mode ultrasound array system

    NASA Astrophysics Data System (ADS)

    Liu, Dalong; Casper, Andrew; Haritonova, Alyona; Ebbini, Emad S.

    2017-03-01

    We present the results from an ultrasound-guided focused ultrasound platform designed to perform real-time monitoring and control of lesion formation. Real-time signal processing of echogenicity changes during lesion formation allows for identification of signature events indicative of tissue damage. The detection of these events triggers the cessation or the reduction of the exposure (intensity and/or time) to prevent overexposure. A dual mode ultrasound array (DMUA) is used for forming single- and multiple-focus patterns in a variety of tissues. The DMUA approach allows for inherent registration between the therapeutic and imaging coordinate systems providing instantaneous, spatially-accurate feedback on lesion formation dynamics. The beamformed RF data has been shown to have high sensitivity and specificity to tissue changes during lesion formation, including in vivo. In particular, the beamformed echo data from the DMUA is very sensitive to cavitation activity in response to HIFU in a variety of modes, e.g. boiling cavitation. This form of feedback is characterized by sudden increase in echogenicity that could occur within milliseconds of the application of HIFU (see http://youtu.be/No2wh-ceTLs for an example). The real-time beamforming and signal processing allowing the adaptive control of lesion formation is enabled by a high performance GPU platform (response time within 10 msec). We present results from a series of experiments in bovine cardiac tissue demonstrating the robustness and increased speed of volumetric lesion formation for a range of clinically-relevant exposures. Gross histology demonstrate clearly that adaptive lesion formation results in tissue damage consistent with the size of the focal spot and the raster scan in 3 dimensions. In contrast, uncontrolled volumetric lesions exhibit significant pre-focal buildup due to excessive exposure from multiple full-exposure HIFU shots. Stopping or reducing the HIFU exposure upon the detection of such an

  19. Transvaginal 3D Image-Guided High Intensity Focused Ultrasound Array

    NASA Astrophysics Data System (ADS)

    Held, Robert; Nguyen, Thuc Nghi; Vaezy, Shahram

    2005-03-01

    The goal of this project is to develop a transvaginal image-guided High Intensity Focused Ultrasound (HIFU) device using piezocomposite HIFU array technology, and commercially-available ultrasound imaging. Potential applications include treatment of uterine fibroids and abnormal uterine bleeding. The HIFU transducer was an annular phased array, with a focal length range of 30-60 mm, an elliptically-shaped aperture of 35×60 mm, and an operating frequency of 3 MHz. A pillow-shaped bag with water circulation will be used for coupling the HIFU energy into the tissue. An intra-cavity imaging probe (C9-5, Philips) was integrated with the HIFU array such that the focal axis of the HIFU transducer was within the image plane. The entire device will be covered by a gel-filled condom when inserted in the vaginal cavity. To control it, software packages were developed in the LabView programming environment. An imaging algorithm processed the ultrasound image to remove noise patterns due to the HIFU signal. The device will be equipped with a three-dimensional tracking system, using a six-degrees-of-freedom articulating arm. Necrotic lesions were produced in a tissue-mimicking phantom and a turkey breast sample for all focal lengths. Various HIFU doses allow various necrotic lesion shapes, including thin ellipsoidal, spherical, wide cylindrical, and teardrop-shaped. Software control of the device allows multiple foci to be activated sequentially for desired lesion patterns. Ultrasound imaging synchronization can be achieved using hardware signals obtained from the imaging system, or software signals determined empirically for various imaging probes. The image-guided HIFU device will provide a valuable tool in visualization of uterine fibroid tumors for the purposes of planning and subsequent HIFU treatment of the tumor, all in a 3D environment. The control system allows for various lesions of different shapes to be optimally positioned in the tumor to cover the entire tumor

  20. MMIC Phased Array Demonstrations with ACTS

    NASA Technical Reports Server (NTRS)

    Raquet, Charles A. (Compiler); Martzaklis, Konstantinos (Compiler); Zakrajsek, Robert J. (Compiler); Andro, Monty (Compiler); Turtle, John P.

    1996-01-01

    Over a one year period from May 1994 to May 1995, a number of demonstrations were conducted by the NASA Lewis Research Center (LeRC) in which voice, data, and/or video links were established via NASA's advanced communications technology satellite (ACTS) between the ACTS link evaluation terminal (LET) in Cleveland, OH, and aeronautical and mobile or fixed Earth terminals having monolithic microwave integrated circuit (MMIC) phased array antenna systems. This paper describes four of these. In one, a duplex voice link between an aeronautical terminal on the LeRC Learjet and the ACTS was achieved. Two others demonstrated duplex voice (and in one case video as well) links between the ACTS and an Army vehicle. The fourth demonstrated a high data rate downlink from ACTS to a fixed terminal. Array antenna systems used in these demonstrations were developed by LeRC and featured LeRC and Air Force experimental arrays using gallium arsenide MMIC devices at each radiating element for electronic beam steering and distributed power amplification. The single 30 GHz transmit array was developed by NASA/LeRC and Texas Instruments. The three 20 GHz receive arrays were developed in a cooperative effort with the Air Force Rome Laboratory, taking advantage of existing Air Force array development contracts with Boeing and Lockheed Martin. The paper describes the four proof-of-concept arrays and the array control system. The system configured for each of the demonstrations is described, and results are discussed.

  1. Cardiac phase detection in intravascular ultrasound images

    NASA Astrophysics Data System (ADS)

    Matsumoto, Monica M. S.; Lemos, Pedro Alves; Yoneyama, Takashi; Furuie, Sergio Shiguemi

    2008-03-01

    Image gating is related to image modalities that involve quasi-periodic moving organs. Therefore, during intravascular ultrasound (IVUS) examination, there is cardiac movement interference. In this paper, we aim to obtain IVUS gated images based on the images themselves. This would allow the reconstruction of 3D coronaries with temporal accuracy for any cardiac phase, which is an advantage over the ECG-gated acquisition that shows a single one. It is also important for retrospective studies, as in existing IVUS databases there are no additional reference signals (ECG). From the images, we calculated signals based on average intensity (AI), and, from consecutive frames, average intensity difference (AID), cross-correlation coefficient (CC) and mutual information (MI). The process includes a wavelet-based filter step and ascendant zero-cross detection in order to obtain the phase information. Firstly, we tested 90 simulated sequences with 1025 frames each. Our method was able to achieve more than 95.0% of true positives and less than 2.3% of false positives ratio, for all signals. Afterwards, we tested in a real examination, with 897 frames and ECG as gold-standard. We achieved 97.4% of true positives (CC and MI), and 2.5% of false positives. For future works, methodology should be tested in wider range of IVUS examinations.

  2. Automated Array Assembly, Phase 2

    NASA Technical Reports Server (NTRS)

    Carbajal, B. G.

    1979-01-01

    The solar cell module process development activities in the areas of surface preparation are presented. The process step development was carried out on texture etching including the evolution of a conceptual process model for the texturing process; plasma etching; and diffusion studies that focused on doped polymer diffusion sources. Cell processing was carried out to test process steps and a simplified diode solar cell process was developed. Cell processing was also run to fabricate square cells to populate sample minimodules. Module fabrication featured the demonstration of a porcelainized steel glass structure that should exceed the 20 year life goal of the low cost silicon array program. High efficiency cell development was carried out in the development of the tandem junction cell and a modification of the TJC called the front surface field cell. Cell efficiencies in excess of 16 percent at AM1 have been attained with only modest fill factors. The transistor-like model was proposed that fits the cell performance and provides a guideline for future improvements in cell performance.

  3. Seismic vertical array analysis for phase decomposition

    NASA Astrophysics Data System (ADS)

    Yoshida, Kunikazu; Sasatani, Tsutomu

    2008-08-01

    We propose a vertical array analysis method that decomposes complex seismograms into body and surface wave time histories by using a velocity structure at the vertical array site. We assume that the vertical array records are the sum of vertically incident plane P and S waves, and laterally incident Love and Rayleigh waves. Each phase at the surface is related to that at a certain depth by the transfer function in the frequency domain; the transfer function is obtained by Haskell's matrix method, assuming a 1-D velocity structure. Decomposed P, S and surface waves at the surface are estimated from the vertical array records and the transfer functions by using a least-squares method in the frequency domain; their time histories are obtained by the inverse Fourier transform. We carried out numerical tests of this method based on synthetic vertical array records consisting of vertically incident plane P and S waves and laterally incident plane Love and Rayleigh waves. Perfect results of the decomposed P, S, Love and Rayleigh waves were obtained for synthetic records without noise. A test of the synthetic records in which a small amount of white noise was added yielded a reasonable result for the decomposed P, S and surface waves. We applied this method to real vertical array records from the Ashigara valley, a moderate-sized sedimentary valley. The array records from two earthquakes occurring at depths of 123 and 148 km near the array (epicentral distance of about 31 km) exhibited long-duration later phases. The analysis showed that duration of the decomposed S waves was a few seconds and that the decomposed surface waves appeared a few seconds after the direct S-wave arrival and had very long duration. This result indicated that the long-duration later phases were generated not by multireflected S waves, but by basin-induced surface waves.

  4. Real-time B-scan ultrasonic imaging using a digital phased array system for NDE

    NASA Astrophysics Data System (ADS)

    Dunki-Jacobs, Robert; Thomas, Lewis

    A demonstration is presented of the ability to produce real-time images of metals on the basis of a phased-array ultrasound system. Attention is given to the critical role played by a beam-former. It is established that the present imaging system's resolution approaches the theoretical capabilities of the given aperture size and wavelength.

  5. In Vivo application and localization of transcranial focused ultrasound using dual-mode ultrasound arrays.

    PubMed

    Haritonova, Alyona; Liu, Dalong; Ebbini, Emad S

    2015-12-01

    Focused ultrasound (FUS) has been proposed for a variety of transcranial applications, including neuromodulation, tumor ablation, and blood-brain barrier opening. A flurry of activity in recent years has generated encouraging results demonstrating its feasibility in these and other applications. To date, monitoring of FUS beams has been primarily accomplished using MR guidance, where both MR thermography and elastography have been used. The recent introduction of real-time dual-mode ultrasound array (DMUA) systems offers a new paradigm in transcranial focusing. In this paper, we present first experimental results of ultrasound-guided transcranial FUS (tFUS) application in a rodent brain, both ex vivo and in vivo. DMUA imaging is used for visualization of the treatment region for placement of the focal spot within the brain. This includes the detection and localization of pulsating blood vessels at or near the target point(s). In addition, DMUA imaging is used to monitor and localize the FUS-tissue interactions in real time. In particular, a concave (40 mm radius of curvature), 32-element, 3.5-MHz DMUA prototype was used for imaging and tFUS application in ex vivo and in vivo rat models. The ex vivo experiments were used to evaluate the point spread function of the transcranial DMUA imaging at various points within the brain. In addition, DMUA-based transcranial ultrasound thermography measurements were compared with thermocouple measurements of subtherapeutic tFUS heating in rat brain ex vivo. The ex vivo setting was also used to demonstrate the capability of DMUA to produce localized thermal lesions. The in vivo experiments were designed to demonstrate the ability of the DMUA to apply, monitor, and localize subtherapeutic tFUS patterns that could be beneficial in transient blood-brain barrier opening. The results show that although the DMUA focus is degraded due to the propagation through the skull, it still produces localized heating effects within a sub

  6. In Vivo Application and Localization of Transcranial Focused Ultrasound Using Dual-Mode Ultrasound Arrays

    PubMed Central

    Haritonova, Alyona; Liu, Dalong; Ebbini, Emad S.

    2015-01-01

    Focused ultrasound (FUS) has been proposed for a variety of transcranial applications, including neuromodulation, tumor ablation, and blood brain barrier opening. A flurry of activity in recent years has generated encouraging results demonstrating its feasibility in these and other applications. To date, monitoring of FUS beams have been primarily accomplished using MR guidance, where both MR thermography and elastography have been used. The recent introduction of real-time dual-mode ultrasound array (DMUA) systems offers a new paradigm in transcranial focusing. In this paper, we present first experimental results of ultrasound-guided transcranial FUS (tFUS) application in a rodent brain, both ex vivo and in vivo. DMUA imaging is used for visualization of the treatment region for placement of the focal spot within the brain. This includes the detection and localization of pulsating blood vessels at or near the target point(s). In addition, DMUA imaging is used to monitor and localize the FUS-tissue interactions in real-time. In particular, a concave (40-mm radius of curvature), 32-element, 3.5 MHz DMUA prototype was used for imaging and tFUS application in ex vivo and in vivo rat model. The ex vivo experiments were used to evaluate the point spread function (psf) of the transcranial DMUA imaging at various points within the brain. In addition, DMUA-based transcranial ultrasound thermography measurements were compared with thermocouple measurements of subtherapeutic tFUS heating in rat brain ex vivo. The ex vivo setting was also used to demonstrate the DMUA capability to produce localized thermal lesions. The in vivo experiments were designed to demonstrate the ability of the DMUA to apply, monitor, and localize subtherapeutic tFUS patterns that could be beneficial in transient blood brain barrier opening. The results show that, while the DMUA focus is degraded due to the propagation through the skull, it still produces localized heating effects within sub

  7. The design of a focused ultrasound transducer array for the treatment of stroke: a simulation study

    PubMed Central

    Pajek, Daniel; Hynynen, Kullervo

    2014-01-01

    High intensity focused ultrasound (HIFU) is capable of mechanically disintegrating blood clots at high pressures. Safe thrombolysis may require frequencies higher than those currently utilized by transcranial HIFU. Since the attenuation and focal distortion of ultrasound in bone increases at higher frequencies, resulting focal pressures are diminished. This study investigated the feasibility of using transcranial HIFU for the non-invasive treatment of ischemic stroke. The use of large aperture, 1.1–1.5 MHz phased arrays in targeting four clinically relevant vessel locations was simulated. Resulting focal sizes decreased with frequency, producing a maximum −3 dB depth of field and lateral width of 2.0 and 1.2 mm, respectively. Mean focal gains above an order of magnitude were observed in three of four targets and transducer intensities required to achieve thrombolysis were determined. Required transducer element counts are about an order of magnitude higher than what currently exists and so, although technically feasible, new arrays would need to be developed to realize this as a treatment modality for stroke. PMID:22800986

  8. Experimental characterization of ultrasonic phased arrays for the nondestructive evaluation of concrete structures

    SciTech Connect

    Azar, L.; Wooh, S.C.

    1999-02-01

    Novel ultrasonic phased arrays were developed and their feasibility was tested for assessing the condition of concrete structures. These sensors are based on low frequency ultrasound technology, which, to date, has been the preferred method for concrete testing. By combining multiple transducer elements in a linear configuration, dynamic phase focusing and steering of the ultrasound beam is possible. An automated testing assembly was used to assess the steering and focusing performance of the array in a cementitious medium. Experimental results demonstrate excellent steerability and accuracy when compared to the numerical simulation presented. The effective steering and focusing behavior in concrete signifies that phased arrays can be used as the primary imaging and scanning device for large scale concrete structures.

  9. Ka-Band Phased Array System Characterization

    NASA Technical Reports Server (NTRS)

    Acosta, R.; Johnson, S.; Sands, O.; Lambert, K.

    2001-01-01

    Phased Array Antennas (PAAs) using patch-radiating elements are projected to transmit data at rates several orders of magnitude higher than currently offered with reflector-based systems. However, there are a number of potential sources of degradation in the Bit Error Rate (BER) performance of the communications link that are unique to PAA-based links. Short spacing of radiating elements can induce mutual coupling between radiating elements, long spacing can induce grating lobes, modulo 2 pi phase errors can add to Inter Symbol Interference (ISI), phase shifters and power divider network introduce losses into the system. This paper describes efforts underway to test and evaluate the effects of the performance degrading features of phased-array antennas when used in a high data rate modulation link. The tests and evaluations described here uncover the interaction between the electrical characteristics of a PAA and the BER performance of a communication link.

  10. Proposed Functional Description for Phased Arrays

    NASA Technical Reports Server (NTRS)

    Jackson, Deborah

    1996-01-01

    Generally speaking, many photonic engineers, while working in a systems development mode, still focus on presenting the unique physical details of the optical elements, instead of using functional representation to describe the system. The purpose of this presentation is to introduce symbols that can be used to represent the functional intent of most of the phased array architecture.

  11. The phase-scanned commutated array network

    NASA Astrophysics Data System (ADS)

    Young, R.

    An array feed network has been developed to demonstrate the P-Scan principle incorporating separate elevation and azimuth antennas. The microwave lens, switches, phase shifters, and amplitude control are discussed, and beam formation is described. The increased scan of the system is addressed, and the results of tests on the system are discussed.

  12. Ultrasonic fingerprinting by phased array transducer

    NASA Astrophysics Data System (ADS)

    Sednev, D.; Kataeva, O.; Abramets, V.; Pushenko, P.; Tverdokhlebova, T.

    2016-06-01

    Increasing quantity of spent nuclear fuel that must be under national and international control requires a novel approach to safeguard techniques and equipment. One of the proposed approaches is utilize intrinsic features of casks with spent fuel. In this article an application of a phased array ultrasonic method is considered. This study describes an experimental results on ultrasonic fingerprinting of austenitic steel seam weld.

  13. Phase calibration scheme for a ``T'' array

    NASA Astrophysics Data System (ADS)

    Ramesh, R.; Subramanian, K. R.; Sastry, Ch. V.

    1999-10-01

    A calibration scheme based on closure and redundancy techniques is described for correcting the phase errors in the complex visibilities observed with a T-shaped radio interferometer array. Practical details of the scheme are illustrated with reference to the Gauribidanur radioheliograph (GRH).

  14. Microelectromechanical Switches for Phased Array Antennas

    NASA Technical Reports Server (NTRS)

    Ponchak, George E.; Simons, Rainee N.; Scardelletti, Maximillian; Varaljay, Nicholas C.

    2000-01-01

    Preliminary results are presented on the fabrication and testing of a MicroElectro-Mechanical (MEM) microstrip series switch. This switch is being developed for use in a K-band phased array antenna that NASA will use for communication links in its Earth orbiting satellites. Preliminary insertion loss and isolation measurements are presented.

  15. Phased array antenna matching: Simulation and optimization of a planar phased array of circular waveguide elements

    NASA Technical Reports Server (NTRS)

    Dudgeon, J. E.

    1972-01-01

    A computerized simulation of a planar phased array of circular waveguide elements is reported using mutual coupling and wide angle impedance matching in phased arrays. Special emphasis is given to circular polarization. The aforementioned computer program has as variable inputs: frequency, polarization, grid geometry, element size, dielectric waveguide fill, dielectric plugs in the waveguide for impedance matching, and dielectric sheets covering the array surface for the purpose of wide angle impedance matching. Parameter combinations are found which produce reflection peaks interior to grating lobes, while dielectric cover sheets are successfully employed to extend the usable scan range of a phased array. The most exciting results came from the application of computer aided optimization techniques to the design of this type of array.

  16. A MRI rotary phased array head coil.

    PubMed

    Li, Bing Keong; Weber, Ewald; Crozier, Stuart

    2013-08-01

    A new rotary phased array (RPA) head coil that can provide homogenous brain images comparable to volumetric radiofrequency coils is proposed for magnetic resonance brain imaging applications. The design of the RPA head coil is a departure from conventional circumferential array design method, as coil elements of the RPA head coil have a "paddle-like" structure consisting of a pair of main conductors located on opposite sides, inserted equi-angularly around and over the head. A prototype 2T receive-only 4-element RPA head coil was constructed and experimentally tested against a conventional receive-only 4-element phased array head coil and a commercial receive-only quadrature birdcage head coil. Homogenous phantom images acquired by the RPA head coil show that signal intensity deep at the center of the phantom was improved as compared to the conventional phased array head coil and this improvement allow the RPA head coil to acquire homogenous brain images similar to brain images acquired with the birdcage head coil. In addition, partial parallel imaging was used in conjunction with the RPA head coil to enable rapid imaging.

  17. Phased array performance evaluation with photoelastic visualization

    SciTech Connect

    Ginzel, Robert; Dao, Gavin

    2014-02-18

    New instrumentation and a widening range of phased array transducer options are affording the industry a greater potential. Visualization of the complex wave components using the photoelastic system can greatly enhance understanding of the generated signals. Diffraction, mode conversion and wave front interaction, together with beam forming for linear, sectorial and matrix arrays, will be viewed using the photoelastic system. Beam focus and steering performance will be shown with a range of embedded and surface targets within glass samples. This paper will present principles and sound field images using this visualization system.

  18. Wide Angle Liquid Crystal Optical Phased Array

    NASA Technical Reports Server (NTRS)

    Wang, Xing-Hua; Wang, Bin; Bos, Philip J.; Anderson, James E.; Pouch, John J.; Miranda, Felix A.; McManamon, Paul F.

    2004-01-01

    Accurate modeling of a high resolution, liquid crystal (LC) based, optical phased array (OPA) is shown. The simulation shows excellent agreement with a test 2-D LC OPA. The modeling method is extendable to cases where the array element size is close to the wavelength of light. The fringing fields of such a device are first studied, and subsequently reduced. This results in a device that demonstrates plus or minus 7.4 degrees of continuous beam steering at a wavelength of 1550 nm, and a diffraction efficiency (DE) higher than 72%.

  19. Transcranial ultrasound imaging with speed of sound-based phase correction: a numerical study.

    PubMed

    Wang, Tianren; Jing, Yun

    2013-10-07

    This paper presents a numerical study for ultrasound transcranial imaging. To correct for the phase aberration from the skull, two critical steps are needed prior to brain imaging. In the first step, the skull shape and speed of sound are acquired by either CT scans or ultrasound scans. In the ultrasound scan approach, phased array and double focusing technique are utilized, which are able to estimate the thickness of the skull with a maximum error of around 10% and the average speed of sound in the skull is underestimated by less than 2%. In the second step, the fast marching method is used to compute the phase delay based on the known skull shape and sound speed from the first step, and the computation can be completed in seconds for 2D problems. The computed phase delays are then used in combination with the conventional delay-and-sum algorithm for generating B-mode images. Images of wire phantoms with CT or ultrasound scan-based phase correction are shown to have much less artifact than the ones without correction. Errors of deducing speed of sound from CT scans are also discussed regarding its effect on the transcranial ultrasound images. Assuming the speed of sound grows linearly with the density, this study shows that, the CT-based phase correction approach can provide clear images of wire phantoms even if the speed of sound is overestimated by 400 m s(-1), or the linear coefficient is overestimated by 40%. While in this study, ultrasound scan-based phase correction performs almost equally well with the CT-based approach, potential problems are identified and discussed.

  20. Photorefractive processing for large adaptive phased arrays

    NASA Astrophysics Data System (ADS)

    Weverka, Robert T.; Wagner, Kelvin; Sarto, Anthony

    1996-03-01

    An adaptive null-steering phased-array optical processor that utilizes a photorefractive crystal to time integrate the adaptive weights and null out correlated jammers is described. This is a beam-steering processor in which the temporal waveform of the desired signal is known but the look direction is not. The processor computes the angle(s) of arrival of the desired signal and steers the array to look in that direction while rotating the nulls of the antenna pattern toward any narrow-band jammers that may be present. We have experimentally demonstrated a simplified version of this adaptive phased-array-radar processor that nulls out the narrow-band jammers by using feedback-correlation detection. In this processor it is assumed that we know a priori only that the signal is broadband and the jammers are narrow band. These are examples of a class of optical processors that use the angular selectivity of volume holograms to form the nulls and look directions in an adaptive phased-array-radar pattern and thereby to harness the computational abilities of three-dimensional parallelism in the volume of photorefractive crystals. The development of this processing in volume holographic system has led to a new algorithm for phased-array-radar processing that uses fewer tapped-delay lines than does the classic time-domain beam former. The optical implementation of the new algorithm has the further advantage of utilization of a single photorefractive crystal to implement as many as a million adaptive weights, allowing the radar system to scale to large size with no increase in processing hardware.

  1. Excitation of ultrasonic Lamb waves using a phased array system with two array probes: phantom and in vitro bone studies.

    PubMed

    Nguyen, Kim-Cuong T; Le, Lawrence H; Tran, Tho N H T; Sacchi, Mauricio D; Lou, Edmond H M

    2014-07-01

    Long bones are good waveguides to support the propagation of ultrasonic guided waves. The low-order guided waves have been consistently observed in quantitative ultrasound bone studies. Selective excitation of these low-order guided modes requires oblique incidence of the ultrasound beam using a transducer-wedge system. It is generally assumed that an angle of incidence, θi, generates a specific phase velocity of interest, co, via Snell's law, θi=sin(-1)(vw/co) where vw is the velocity of the coupling medium. In this study, we investigated the excitation of guided waves within a 6.3-mm thick brass plate and a 6.5-mm thick bovine bone plate using an ultrasound phased array system with two 0.75-mm-pitch array probes. Arranging five elements as a group, the first group of a 16-element probe was used as a transmitter and a 64-element probe was a receiver array. The beam was steered for six angles (0°, 20°, 30°, 40°, 50°, and 60°) with a 1.6-MHz source signal. An adjoint Radon transform algorithm mapped the time-offset matrix into the frequency-phase velocity dispersion panels. The imaged Lamb plate modes were identified by the theoretical dispersion curves. The results show that the 0° excitation generated many modes with no modal discrimination and the oblique beam excited a spectrum of phase velocities spread asymmetrically about co. The width of the excitation region decreased as the steering angle increased, rendering modal selectivity at large angles. The phenomena were well predicted by the excitation function of the source influence theory. The low-order modes were better imaged at steering angle ⩾30° for both plates. The study has also demonstrated the feasibility of using the two-probe phased array system for future in vivo study.

  2. Brazilian Decimetric Array (Phase-I)

    NASA Astrophysics Data System (ADS)

    Sawant, H. S.; Ramesh, R.; Cecatto, J. R.; Faria, C.; Fernandes, F. C. R.; Rosa, R. R.; Andrade, M. C.; Stephany, S.; Cividanes, L. B. T.; Miranda, C. A. I.; Botti, L. C. L.; Boas, J. W. S. V.; Saito, J. H.; Moron, C. E.; Mascarenhas, N. D.; Subramanian, K. R.; Sundararajan, M. S.; Ebenezer, E.; Sankararaman, M. R.

    2007-05-01

    An East West, one-dimensional radio interferometer array consisting of five parabolic dish antennas has been set up at Cachoeira Paulista (longitude 45°0‧20″ W, latitude 22°41‧19″ S) for observations of the Sun and some of the strong sidereal sources by the Instituto Nacional de Pesquisas Espaciais (INPE), Brazil. This is Phase-I of the proposed Brazilian Decimetric Array and can be operated at any frequency in the range 1.2 1.7 GHz. The instrument has been in operation since November 2004 onwards at 1.6 GHz. The angular and temporal resolutions at this frequency are ˜3‧ and 100 ms, respectively. Details of the array, analog/digital receiver system, and a preliminary East West one-dimensional solar image at the 1.6 GHz are presented in this paper.

  3. Phased array-fed antenna configuration study

    NASA Technical Reports Server (NTRS)

    Crosswell, W. F.; Ball, D. E.; Taylor, R. C.

    1983-01-01

    The scope of this contract entails a configuration study for a phased array fed transmit antenna operating in the frequency band of 17.7 to 20.2 GHz. This initial contract provides a basis for understanding the design limitations and advantages of advanced phased array and cluster feeds (both utilizing intergral MMIC modules) illuminating folded reflector optics (both near field and focused types). Design parametric analyses are performed utilizing as constraints the objective secondary performance requirements of the Advanced Communications Technology Satellite (Table 1.0). The output of the study provides design information which serves as a data base for future active phased array fed antenna studies such as detailed designs required to support the development of a ground tested breadboard. In general, this study is significant because it provides the antenna community with an understanding of the basic principles which govern near field phased scanned feed effects on secondary reflector system performance. Although several articles have been written on analysis procedures and results for these systems, the authors of this report have observed phenomenon of near field antenna systems not previously documented. Because the physical justification for the exhibited performance is provided herein, the findings of this study add a new dimension to the available knowledge of the subject matter.

  4. Therapy/imaging array-based system and technology for intense ultrasound surgery

    NASA Astrophysics Data System (ADS)

    Barthe, Peter G.; Slayton, Michael H.; Jaeger, Paul M.; Makin, Inder R. S.; Gallagher, Laura A.; Mast, T. Douglas; Runk, Megan M.; Faidi, Waseem

    2004-05-01

    Minimally invasive, miniature (2.2- × 50-mm aperture, 3.3-mm diameter) dual-mode linear arrays have been developed into low-cost disposable probes with high acoustic power output (120 W/cm2 at the source), high transmit efficiency (>65% typical), and good imaging performance (50% fractional bandwidth, >100-mm-deep field of view). These therapy/imaging probes have been integrated into a flexible intense ultrasound surgery platform which also includes conventional diagnostic imaging probes. A system architecture has been developed which includes a 64-channel therapy driver with software selection of array aperture and phasing (λ/16), frequency (0.5-8 MHz), drive amplitude (5 W/channel, nominal), rotational steering (+/-180 deg), and temporal sequencing/switching of imaging/therapy/monitoring modes. System software includes graphical and text-based script mode control of therapeutic treatment. Real-time monitoring of electric power per channel, temperature sensors, and thermal effects provide a range of feedback and safety. Numerous system and probe technological issues such as electrical interconnect and matching, acoustic coupling, thermal control, and maintaining probe efficiency have been addressed. The array-based imaging/therapy system has produced encouraging results in preclinical studies of bulk tissue ablation and imaging.

  5. 1D multi-element CMUT arrays for ultrasound thermal therapy

    NASA Astrophysics Data System (ADS)

    N'Djin, William Apoutou; Canney, Michael; Meynier, Cyril; Chavrier, Françoise; Lafon, Cyril; Nguyen-Dinh, An; Chapelon, Jean-Yves; Carpentier, Alexandre

    2017-03-01

    Interstitial therapeutic ultrasound devices are a promising technology for performing thermal ablation in a wide variety of organs. In this study, the use of Capacitive Micromachined Ultrasound Transducers (CMUTs) for interstitial heating applications was investigated. CMUTs exhibit potential advantages for use in therapeutic ultrasound applications in comparison to standard piezo ultrasound transducer technologies as they have good characteristics in terms of miniaturization (cell size: few dozens of microns), bandwidth (several MHz) and high electro-acoustic efficiency. Two designs of CMUT arrays were studied: (1) a 1D 128-element planar-CMUT array originally dedicated to abdominal ultrasound imaging purposes (5 MHz, element size: 0.3 × 8.0 mm2); (2) a 12-element linear-array, 32.4-mm long and 0.8-mm wide, developed specifically for minimally-invasive interstitial therapeutic applications (6 MHz, element size: 2.7 × 0.8 mm2). Simulations were performed to evaluate the ability to generate thermal lesions in soft tissues with: (1) 1 single linear array, (2) a combination of multiple linear arrays positioned on a cylindrical catheter. Experimental investigations performed with the CMUT imaging array showed the ability to generate surface acoustic intensities (Iac) up to 20 W.cm-2 and to generate intense centimetric thermal lesions in in-vitro turkey breast tissues. At 6 MHz, a single element was able to generate in water a maximum peak pressure of >0.5 MPa. In simulations, the ability to use various power levels and frequencies on independent elements, as well as combinations of multiple linear-arrays offered sufficient flexibility to achieve a wide variety of thermal ablation patterns in 3D. Simulated ablation volumes could be controlled to cover accurately non-symmetrical volumes of brain metastases. In conclusion, CMUT arrays show interesting characteristics, which may open new perspectives of spatial control for conformal interstitial thermal therapy with

  6. A Phased Array Magnetometer for Sensing IED

    DTIC Science & Technology

    2008-02-04

    of information is estimated to average 1 tiour per response, including the time for reviewing instructions, searching existing data sources, gathering...Device Organization (JIEDDO) (Contract No: FA9550-07- 1 -0107) Program Dr. Byung-Lip "Les" Lee Manager Project Title A Phased Array...Los Angeles, CA 90095-1597 Voice: 310-825-6030 Fax:310-206-2302 1 . OVERALL OBJECTIVE The objective of this project was to develop the fundamental

  7. Optical Matrix Inverter for Phased Array Radar

    DTIC Science & Technology

    1990-04-01

    cancelling was presented. -, 14 SUBJECTTERMS 15 NUMBER OF PAGES Phased Arrays, Optical Algebraic Processors, Optical Matrix 64 Inverter, Optical...optical algebraic processors to such problems. The advantages gained by using optical systems over their electronic counterparts are investigated...are both time consuming algebra problems. B. No a priori Information is Known This is the most general case where we assume no information about jammers

  8. Technology Development for Millimeter Wave Phased Arrays.

    DTIC Science & Technology

    1987-05-01

    design would use the technology of integration-the same technology that has brought us computing power at such a low cost. The integrated phased array ...circuitry and/or the feed network, which can degrade sidelobe levels or polarization. A Two Layer Substrate Figure 2.8 shows a possible two-layer design ...feed substrates. Coupling is again through aper- tures in the ground plane of the antenna substrate. This design also allows the use of a low dielectric

  9. Phased array antenna for space shuttle orbiter

    NASA Technical Reports Server (NTRS)

    Davidson, Shayla E.

    1987-01-01

    The National Aeronautics and Space Administration is developing a distributed phased array antenna at the Lyndon B. Johnson Space Center as a possible upgrade for the Space Shuttle Orbiter S-band phase modulation communications system. The antenna consists of an eight-element transmit section, eight-element receive section, and a single L-band receive element. The antenna design is constrained by the existing Orbiter system and space environment. The solution to the interface design problems led to an antenna system which provides improved link margins and yet supports previous operational configurations. This paper describes the system development, antenna hardware, and the interface consideration which led to the final design.

  10. Digital Phased Array Ultrasonic Inspection system with dynamic focusing

    NASA Astrophysics Data System (ADS)

    Hwang, J. S.; Shin, H. J.; Song, S. J.; Song, T. K.

    2000-05-01

    Enhancement of the ultrasonic flaw detection and characterization is expected through the development of a high performance PAULI (Phased Array Ultrasonic Inspection) system which can provide high resolution two-dimensional (sector scan: S-scan) images. The high-resolution S-scan image renders inspection results more readable compared to the conventional A-scan and B-scan results. Therefore, it can improve inspection efficiency and reliability. In this study, the ultrasonic imaging technologies developed in medical applications were adapted to develop a digital PAULI system for nondestructive testing. To provide real-time S-scan images, the PAULI system uses 64 independent transceiver channels controlled by proper delay laws for steering and focusing the ultrasound beams along each scan lines. The PAULI system employs a novel dynamic receive focusing technique in order to optimize the lateral resolution by focusing the ultrasound wave at all imaging points. The dynamic receive focusing is achieved in real-time by digital signal processing methods. The feasibility of PAULI system is demonstrated for the NDE of steel structures.

  11. An Optical Phased Array for LIDAR

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Wu, M. C.

    2016-11-01

    We have previously demonstrated the development of an Optical Phased Array (OPA) micromechanical system (MEMS) used for beam steering, which shows great advantages over previous mechanisms such as opto-mechanical, acousto-optical (AO) or electro-optical (EO). We aim to integrate the OPA MEMS system into the application of automobile navigation, which is currently primarily dominated by opto-mechanical scanning based systems. Opto-mechanical scanning devices are usually bulky and relatively slow, while competing technologies (AO, EO) utilize devices that while small in size, cannot provide the steering speeds and versatility necessary for many applications. In drawing from phased array concepts that revolutionized RADAR technology by providing a compact, agile alternative to mechanically steered technology, the OPA based LIDAR program seeks to integrate thousands of closely packed optical emitting facets, precise relative electronic phase control of these facets, and all within a very small form factor. Comparing with other competing LIDAR system, the OPA based LIDAR system will have multiple degrees of freedom for phase control which enables not only agile beam steering but also beam forming and multiple beam generation, greatly expanding the diversity of applications.

  12. Pulse-echo phased array ultrasonic inspection of pultruded rod stitched efficient unitized structure (PRSEUS)

    SciTech Connect

    Johnston, P. H.

    2011-06-23

    A PRSEUS test article was subjected to controlled impact on the skin face followed by static and cyclic axial compressions. Phased array ultrasonic inspection was conducted before impact, and after each of the test conditions. A linear phased array probe with a manual X-Y scanner was used for interrogation. Ultrasound showed a delamination between the skin and stringer flange adjacent to the impact. As designed, the stitching in the flange arrested the lateral flaw formation. Subsequent ultrasonic data showed no delamination growth due to continued loading.

  13. Liquid sodium testing of in-house phased array EMAT transducer for L-wave applications

    SciTech Connect

    Le Bourdais, F.; Le Polles, T.; Baque, F.

    2015-07-01

    This paper describes the development of an in-house phased array EMAT transducer for longitudinal wave inspection in liquid sodium. The work presented herein is part of an undergoing project aimed at improving in-service inspection techniques for the ASTRID reactor project. The design process of the phased array EMAT probe is briefly explained and followed by a review of experimental test results. We first present test results obtained in the laboratory while the last part of the paper describes the liquid sodium testing and the produced ultrasound images. (authors)

  14. Simulation of Transrib HIFU Propagation and the Strategy of Phased-array Activation

    NASA Astrophysics Data System (ADS)

    Zhou, Yufeng; Wang, Mingjun

    Liver ablation is challenging in high-intensity focused ultrasound (HIFU) because of the presence of ribs and great inhomogeneity in multi-layer tissue. In this study, angular spectrum approach (ASA) has been used in the wave propagation from phased-array HIFU transducer, and diffraction, attenuation and the nonlinearity are accounted for by means of second order operator splitting method. Bioheat equation is used to simulate the subsequent temperature elevation and lesion formation with the formation of shifted focus and multiple foci. In summary, our approach could simulate the performance of phased-array HIFU in the clinics and then develop an appropriate treatment plan.

  15. Pulse-Echo Phased Array Ultrasonic Inspection of Pultruded Rod Stitched Efficient Unitized Structure (prseus)

    NASA Astrophysics Data System (ADS)

    Johnston, P. H.

    2011-06-01

    A PRSEUS test article was subjected to controlled impact on the skin face followed by static and cyclic axial compressions. Phased array ultrasonic inspection was conducted before impact, and after each of the test conditions. A linear phased array probe with a manual X-Y scanner was used for interrogation. Ultrasound showed a delamination between the skin and stringer flange adjacent to the impact. As designed, the stitching in the flange arrested the lateral flaw formation. Subsequent ultrasonic data showed no delamination growth due to continued loading.

  16. Visualization of phased-array sound fields and flaw interaction using the photoelastic effect

    NASA Astrophysics Data System (ADS)

    Schmitte, T.; Orth, T.; Kersting, T.

    2012-05-01

    In order to visualize ultrasound in steel the photoelastic imager is a complementary technique to simulations, with the advantage that real transducers are used. In this contribution we show the linear behavior of the derived photoelastic signal and compare the results to FEM calculations. We use the result for quantitative analysis of sound-fields of immersion and phased array transducers. Interesting results are derived by analysis of the influence of missing elements on the shape and intensity of phased array (PA) ultrasonic pulses. Furthermore the formation of grating lobes from PA excitation is demonstrated and the plurality of waves generated from a small notch is displayed exemplarily.

  17. Diffraction and coherence in breast ultrasound tomography: a study with a toroidal array

    SciTech Connect

    Huang, Lianjie; Simonetti, Francesco; Duric, Neb; Littrup, Peter

    2008-01-01

    Ultrasound is commonly used as an adjunct to mammography for diagnostic evaluation of suspicions arising from breast cancer screening. As an alternative to conventional sonography that uses hand-held transducers, toroidal array probes that encircle the breast immersed in a water bath have been investigated for ultrasound tomography. In this paper, two sets of experiments performed with a prototype ultrasound scanner on a phantom and a human breast in vivo are used to investigate the effects of diffraction and coherence in ultrasound tomography. Reconstructions obtained with transmission diffraction tomography (TDT) are compared with conventional reflection imaging and computerized ultrasound tomography showing a substantial improvement. The in vivo tests demonstrate that TDT can image the complex boundary of a cancer mass and suggest that it can reveal the anatomy of milk ducts and Cooper's ligaments.

  18. Integrated circuits for volumetric ultrasound imaging with 2-D CMUT arrays.

    PubMed

    Bhuyan, Anshuman; Choe, Jung Woo; Lee, Byung Chul; Wygant, Ira O; Nikoozadeh, Amin; Oralkan, Ömer; Khuri-Yakub, Butrus T

    2013-12-01

    Real-time volumetric ultrasound imaging systems require transmit and receive circuitry to generate ultrasound beams and process received echo signals. The complexity of building such a system is high due to requirement of the front-end electronics needing to be very close to the transducer. A large number of elements also need to be interfaced to the back-end system and image processing of a large dataset could affect the imaging volume rate. In this work, we present a 3-D imaging system using capacitive micromachined ultrasonic transducer (CMUT) technology that addresses many of the challenges in building such a system. We demonstrate two approaches in integrating the transducer and the front-end electronics. The transducer is a 5-MHz CMUT array with an 8 mm × 8 mm aperture size. The aperture consists of 1024 elements (32 × 32) with an element pitch of 250 μm. An integrated circuit (IC) consists of a transmit beamformer and receive circuitry to improve the noise performance of the overall system. The assembly was interfaced with an FPGA and a back-end system (comprising of a data acquisition system and PC). The FPGA provided the digital I/O signals for the IC and the back-end system was used to process the received RF echo data (from the IC) and reconstruct the volume image using a phased array imaging approach. Imaging experiments were performed using wire and spring targets, a ventricle model and a human prostrate. Real-time volumetric images were captured at 5 volumes per second and are presented in this paper.

  19. Measured aperture-array noise temperature of the Mark II phased array feed for ASKAP

    NASA Astrophysics Data System (ADS)

    Chippendale, A. P.; Brown, A. J.; Beresford, R. J.; Hampson, G. A.; Shaw, R. D.; Hayman, D. B.; Macleod, A.; Forsyth, A. R.; Hay, S. G.; Leach, M.; Cantrall, C.; Brothers, M. L.; Hotan, A. W.

    2015-11-01

    We have measured the aperture-array noise temperature of the first Mk. II phased array feed that CSIRO has built for the Australian Square Kilometre Array Pathfinder telescope. As an aperture array, the Mk. II phased array feed achieves a beam equivalent noise temperature less than 40 K from 0.78 GHz to 1.7 GHz and less than 50 K from 0.7 GHz to 1.8 GHz for a boresight beam directed at the zenith. We believe these are the lowest reported noise temperatures over these frequency ranges for ambient-temperature phased arrays. The measured noise temperature includes receiver electronics noise, ohmic losses in the array, and stray radiation from sidelobes illuminating the sky and ground away from the desired field of view. This phased array feed was designed for the Australian Square Kilometre Array Pathfinder to demonstrate fast astronomical surveys with a wide field of view for the Square Kilometre Array.

  20. Design of patient-specific focused ultrasound arrays for non-invasive brain therapy with increased trans-skull transmission and steering range

    NASA Astrophysics Data System (ADS)

    Hughes, Alec; Hynynen, Kullervo

    2017-09-01

    The use of a phased array of ultrasound transducer elements to sonicate through the skull has opened the way for new treatments and the delivery of therapeutics beyond the blood-brain barrier. The limited steering range of current clinical devices, particularly at higher frequencies, limits the regions of the brain that are considered treatable by ultrasound. A new array design is introduced that allows for high levels of beam steering and increased transmission throughout the brain. These improvements are achieved using concave transducers normal to the outer-skull surface in a patient-specific configuration to target within the skull, so that the far-field of each beam is within the brain. It is shown that by using pulsed ultrasound waves timed to arrive in-phase at the desired target, sufficient levels of acoustic energy are delivered for blood-brain barrier opening throughout the brain.

  1. A phased antenna array for surface plasmons

    PubMed Central

    Dikken, Dirk Jan W.; Korterik, Jeroen P.; Segerink, Frans B.; Herek, Jennifer L.; Prangsma, Jord C.

    2016-01-01

    Surface plasmon polaritons are electromagnetic waves that propagate tightly bound to metal surfaces. The concentration of the electromagnetic field at the surface as well as the short wavelength of surface plasmons enable sensitive detection methods and miniaturization of optics. We present an optical frequency plasmonic analog to the phased antenna array as it is well known in radar technology and radio astronomy. Individual holes in a thick gold film act as dipolar emitters of surface plasmon polaritons whose phase is controlled individually using a digital spatial light modulator. We show experimentally, using a phase sensitive near-field microscope, that this optical system allows accurate directional emission of surface waves. This compact and flexible method allows for dynamically shaping the propagation of plasmons and holds promise for nanophotonic applications employing propagating surface plasmons. PMID:27121099

  2. A phased antenna array for surface plasmons.

    PubMed

    Dikken, Dirk Jan W; Korterik, Jeroen P; Segerink, Frans B; Herek, Jennifer L; Prangsma, Jord C

    2016-04-28

    Surface plasmon polaritons are electromagnetic waves that propagate tightly bound to metal surfaces. The concentration of the electromagnetic field at the surface as well as the short wavelength of surface plasmons enable sensitive detection methods and miniaturization of optics. We present an optical frequency plasmonic analog to the phased antenna array as it is well known in radar technology and radio astronomy. Individual holes in a thick gold film act as dipolar emitters of surface plasmon polaritons whose phase is controlled individually using a digital spatial light modulator. We show experimentally, using a phase sensitive near-field microscope, that this optical system allows accurate directional emission of surface waves. This compact and flexible method allows for dynamically shaping the propagation of plasmons and holds promise for nanophotonic applications employing propagating surface plasmons.

  3. Photonic Multitasking Interleaved Si Nanoantenna Phased Array.

    PubMed

    Lin, Dianmin; Holsteen, Aaron L; Maguid, Elhanan; Wetzstein, Gordon; Kik, Pieter G; Hasman, Erez; Brongersma, Mark L

    2016-12-14

    Metasurfaces provide unprecedented control over light propagation by imparting local, space-variant phase changes on an incident electromagnetic wave. They can improve the performance of conventional optical elements and facilitate the creation of optical components with new functionalities and form factors. Here, we build on knowledge from shared aperture phased array antennas and Si-based gradient metasurfaces to realize various multifunctional metasurfaces capable of achieving multiple distinct functions within a single surface region. As a key point, we demonstrate that interleaving multiple optical elements can be accomplished without reducing the aperture of each subelement. Multifunctional optical elements constructed from Si-based gradient metasurface are realized, including axial and lateral multifocus geometric phase metasurface lenses. We further demonstrate multiwavelength color imaging with a high spatial resolution. Finally, optical imaging functionality with simultaneous color separation has been obtained by using multifunctional metasurfaces, which opens up new opportunities for the field of advanced imaging and display.

  4. Phase discriminating capacitive array sensor system

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor); Rahim, Wadi (Inventor)

    1993-01-01

    A phase discriminating capacitive sensor array system which provides multiple sensor elements which are maintained at a phase and amplitude based on a frequency reference provided by a single frequency stabilized oscillator. Sensor signals provided by the multiple sensor elements are controlled by multiple phase control units, which correspond to the multiple sensor elements, to adjust the sensor signals from the multiple sensor elements based on the frequency reference. The adjustment made to the sensor signals is indicated by output signals which indicate the proximity of the object. The output signals may also indicate the closing speed of the object based on the rate of change of the adjustment made, and the edges of the object based on a sudden decrease in the adjustment made.

  5. Fabrication and Performance of a Miniaturized and Integrated Endoscope Ultrasound Convex Array for Digestive Tract Imaging.

    PubMed

    Peng, Jue; Peng, Xiaojian; Tang, Hu; Li, Xiaozhen; Chen, Ruimin; Li, Yang; Wang, Tianfu; Chen, Siping; Shung, Koping; Zhou, Qifa

    2017-04-24

    This work presents the design, fabrication and testing of a miniaturized and integrated ultrasound endoscope for use as an in situ digestive diagnostic device to facilitate real-time ultrasound guidance of intervention treatments. We designed an optimal structure to integrate an auto-focus 5-megapixel camera module with an 8-MHz, 64-element curvilinear ultrasonic array in one miniaturized package. A novel three-axis auto-focusing voice coil motor (VCM) was designed and manufactured for the camera module to move the lens position for auto-focusing and to adjust the lens tilt. The results showed that the array had a center frequency of 8.09 MHz and a -6-dB fractional bandwidth of 83%. At the center frequency, the two-way insertion loss was 40.6 dB. Endoscopic ultrasound imaging demonstrated satisfactory performance for imaging an anthropomorphic phantom of the esophagus. By slightly adjusting the tilt angle of the optical axis of the lens, the optical image captured by the auto-focusing lens obtained improved definition regardless of changes in the view angle of the camera with respect to the objects being captured. The integrated convex ultrasound endoscope, possessing minimal size, improved optical imaging definition, and good ultrasound imaging performance, can become a useful tool in digestive tract imaging. The miniaturized and integrated convex ultrasound endoscope can facilitate real-time ultrasound intervention guidance, reducing risks associated with the operation.

  6. Phased Antenna Array for Global Navigation Satellite System Signals

    NASA Technical Reports Server (NTRS)

    Turbiner, Dmitry (Inventor)

    2015-01-01

    Systems and methods for phased array antennas are described. Supports for phased array antennas can be constructed by 3D printing. The array elements and combiner network can be constructed by conducting wire. Different parameters of the antenna, like the gain and directivity, can be controlled by selection of the appropriate design, and by electrical steering. Phased array antennas may be used for radio occultation measurements.

  7. Scattering of ultrasound by minority phases in polycrystalline metals

    NASA Astrophysics Data System (ADS)

    Sayers, C. M.

    1984-01-01

    The scattering of ultrasound by minority phases in polycrystalline metals is discussed. For discrete inclusions, the scattering theory of Ying and Truell describes the attenuation of longitudinal waves. This is demonstrated by comparison with experiments of Papadakis for graphite particles in modular cast iron. To treat the scattering by a second phase formed by segregation at a grain boundary, the scattering by a spherical shell with density and elastic constants different from those of the surrounding medium is developed. Reflection of ultrasound at this boundary is found to enhance the attenuation at low frequencies. Application is made to the scattering by manganese sulphide in free machining steel.

  8. Strategies for Ultrasound Imaging Using Two-Dimensional Arrays

    NASA Astrophysics Data System (ADS)

    Velichko, A.; Wilcox, P. D.

    2010-02-01

    2D arrays are able to `view' a given defect from a range of angles leading to the possibility of obtaining richer characterization detail than possible with 1D arrays. This has clear benefits as real defects and engineering structures are three-dimensional. This paper describes different approaches to optimize 2D array design. Results are shown that illustrate the application of the proposed techniques to modeling and experimental data.

  9. Ultrasonic phased array transducers for nondestructive evaluation of steel structures

    NASA Astrophysics Data System (ADS)

    Song, Sung-Jin; Shin, Hyeon Jae; Jang, You Hyun

    2000-05-01

    An ultrasonic phased array transducer has been developed and demonstrated for the nondestructive evaluation of steel structures. The number of array elements is 64 and the center frequency is about 5 MHz. This phased array transducer is designed to use with the phased array system that does steering, transmission focusing and dynamic receive focusing. Each of the array elements is individually excited according to the focal laws and steering angles. Measurements of ultrasonic beam profiles for the array transducer in a reference steel block are presented and compared with theoretical predictions. Some of the phased array transducer design concepts for the application in steel structures are discussed. The two-dimensional ultrasonic images of the sample steel block including flat bottom holes and side drilled holes are presented. Experimental and theoretical results demonstrate excellent feasibility of the utility of the phased array transducer in imaging and detection of defects in steel structures.

  10. Consistency check of diagnostic ultrasound transducer arrays using tissue-equivalent phantoms

    NASA Astrophysics Data System (ADS)

    Wolter, Steffen; Kopp, Andreas; Liebscher, Eckhard; Rosenfeld, Eike

    2012-05-01

    Measurements at two different types of Phantoms - a classic thread phantom and a 3D cyst phantom - were carried out to assess the technical quality of ultrasound B-scan systems. Using statistical methods we examined whether the phantoms are suitable for a consistency test of the transducer arrays. Based on simulated transducer failures it was found that in particular the detection of local of element failures in arrays turned out to be problematic.

  11. Optimized Hyperthermia Treatment of Prostate Cancer Using a Novel Intracavitary Ultrasound Array

    DTIC Science & Technology

    2006-01-01

    channel . The ultra- sound array and animal (or phantom) were placed inside a birdcage coil to receive/transmit the radio frequency (RF) signal for MRI ... 3T Magnet Receiving RF coil Intracavitary Array Animal / phantom Luxtron® Thermal map calculation Closed-loop controller Ultrasound...birdcage coil to receive/transmit the radio frequency (RF) signal for MRI measurement. Temperature maps constructed from MRI data using proton resonance

  12. A digital sidelobe canceller for a linear phased-array

    NASA Astrophysics Data System (ADS)

    Wardrop, B.; Gould, D. M.

    The design and performance of a three auxiliary sidelobe canceller for use with a 25 element S-band phased-array is described. The phased-array incorporates a resistive-matrix multiple-beam former, and so the auxiliaries can be either elements of the array, or other beams. Experimental results showing its performance against multiple noise jammers are presented.

  13. Acoustic trapping with a high frequency linear phased array.

    PubMed

    Zheng, Fan; Li, Ying; Hsu, Hsiu-Sheng; Liu, Changgeng; Tat Chiu, Chi; Lee, Changyang; Ham Kim, Hyung; Shung, K Kirk

    2012-11-19

    A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array.

  14. Acoustic trapping with a high frequency linear phased array

    PubMed Central

    Zheng, Fan; Li, Ying; Hsu, Hsiu-Sheng; Liu, Changgeng; Tat Chiu, Chi; Lee, Changyang; Ham Kim, Hyung; Shung, K. Kirk

    2012-01-01

    A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array. PMID:23258939

  15. Reconfigurable 2D cMUT-ASIC arrays for 3D ultrasound image

    NASA Astrophysics Data System (ADS)

    Song, Jongkeun; Jung, Sungjin; Kim, Youngil; Cho, Kyungil; Kim, Baehyung; Lee, Seunghun; Na, Junseok; Yang, Ikseok; Kwon, Oh-kyong; Kim, Dongwook

    2012-03-01

    This paper describes the design and implementations of the complete 2D capacitive micromachined ultrasound transducer electronics and its analog front-end module for transmitting high voltage ultrasound pulses and receiving its echo signals to realize 3D ultrasound image. In order to minimize parasitic capacitances and ultimately improve signal-to- noise ratio (SNR), cMUT has to be integrate with Tx/Rx electronics. Additionally, in order to integrate 2D cMUT array module, significant optimized high voltage pulser circuitry, low voltage analog/digital circuit design and packaging challenges are required due to high density of elements and small pitch of each element. We designed 256(16x16)- element cMUT and reconfigurable driving ASIC composed of 120V high voltage pulser, T/R switch, low noise preamplifier and digital control block to set Tx frequency of ultrasound and pulse train in each element. Designed high voltage analog ASIC was successfully bonded with 2D cMUT array by flip-chip bonding process and it connected with analog front-end board to transmit pulse-echo signals. This implementation of reconfigurable cMUT-ASIC-AFE board enables us to produce large aperture 2D transducer array and acquire high quality of 3D ultrasound image.

  16. Mechanism modeling for phase fraction measurement with ultrasound attenuation in oil–water two-phase flow

    NASA Astrophysics Data System (ADS)

    Su, Qian; Tan, Chao; Dong, Feng

    2017-03-01

    When measuring the phase fraction of oil–water two-phase flow with the ultrasound attenuation, the phase distribution and fraction have direct influence on the attenuation coefficient. Therefore, the ultrasound propagation at various phase fractions and distributions were investigated. Mechanism models describing phase fraction with the ultrasound attenuation coefficient were established by analyzing the interaction between ultrasound and two-phase flow by considering the scattering, absorption and diffusion effect. Experiments were performed to verify the theoretical analysis, and the test results gave good agreement with the theoretical analysis. When the dispersed phase fraction is low, the relationship between ultrasound attenuation coefficient and phase fraction is of monotonic linearity; at higher dispersed phase fraction, ultrasound attenuation coefficient presents an irregular response to the dispersed phase fraction. The presented mechanism models give reasonable explanations about the trend of ultrasound attenuation.

  17. Visualization of phase conjugate ultrasound waves passed through inhomogeneous layer.

    PubMed

    Yamamoto, K; Pernod, P; Preobrazhensky, V

    2004-04-01

    Compensation of phase distortions of ultrasound beams by means of parametric phase conjugation is visualized. Quasi-plane and focused primary beams were distorted by a polymer aberration layer introduced between the primary wave source and the wave phase conjugator. It is demonstrated acousto-optically that, while the acoustic field is strongly irregular in the area between aberration layer and conjugator, the phase conjugate wave visibly reproduces the primary beams in the area between the layer and the primary wave source. The phenomenon is observed in supercritical mode of parametric amplification when intensity of phase conjugate wave is high enough for manifestations of acoustic nonlinearities in water.

  18. Short ultrasound exposure times for noninvasive insulin delivery in rats using the lightweight cymbal array.

    PubMed

    Lee, Seungjun; Newnham, Robert E; Smith, Nadine Barrie

    2004-02-01

    The purpose of this study is to demonstrate the feasibility of using short ultrasound exposure times to noninvasively deliver insulin with a lightweight (<22 g), low-profile (37 x 37 x 7 mm3) cymbal array (f = 20 kHz). Using hyperglycemic rats, previous experiments using the array demonstrated that blood glucose would decrease approximately 250 mg/dl from 60 and 20 minutes of pulsed ultrasound exposure for transdermal insulin delivery. Using a similar intensity (Isptp = 100 mW/cm2, 20% duty cycle), the goal was to determine if the same effect can be achieved with only 5 minutes of ultrasound exposure. For these experiments, 20 Sprague Dawley rats were anesthetized and shaved, and a 1-mm watertight standoff reservoir that held the insulin or saline was placed between the rat's abdomen and the ultrasound array. At the beginning of the experiment and every 30 minutes, 0.3 ml of blood was collected from the jugular vein to determine the blood glucose level (milligrams per deciliter) for a total of 90 minutes. For comparison purposes between the rats, the change in the glucose level for each rat was normalized to a baseline (i.e., 0 mg/dl). The first control group used insulin in the reservoir without any ultrasound. The second control group had saline in the reservoir with ultrasound operating at Isptp = 100 mW/cm2 for 60 minutes. For the noncontrol experiments, the third group used insulin with ultrasound exposure for 10 minutes. The last group used insulin with ultrasound operating with a 5-minute exposure to examine the effects of using short ultrasound exposure times on delivery. For the 10- and 5-minute ultrasound exposure groups, the glucose level was found to decrease from the baseline to -174.6 +/- 67.2 and -200.4 +/- 43.4 mg/dl measured after 1 hour, respectively. These results indicated that ultrasound exposure times do not need to be long to deliver a clinically significant insulin dose to reduce a high blood glucose level.

  19. Hybrid-array-based optoacoustic and ultrasound (OPUS) imaging of biological tissues

    NASA Astrophysics Data System (ADS)

    Deán-Ben, X. L.; Merčep, E.; Razansky, D.

    2017-05-01

    Hybrid optoacoustic and pulse-echo ultrasound imaging is an attractive multi-modal combination owing to the highly complementary contrast of the two techniques. Efficient hybridization is often hampered by significant dissimilarities between their optimal data acquisition and image formation strategies. Herein, we introduce an approach for combined optoacoustic and ultrasound imaging based on a plano-concave detector array design with a non-uniform pitch distribution. The hybrid design optimized for both modalities allows for maintaining an extended field of view for efficient ultrasound navigation while simultaneously providing broad tomographic coverage for optimal optoacoustic imaging performance. Imaging sessions performed in tissue-mimicking phantoms and healthy volunteers demonstrate that the suggested approach renders an enhanced imaging performance as compared with the previously reported hybrid optoacoustic and ultrasound imaging approaches. Thus, it can greatly facilitate clinical translation of the optoacoustic imaging technology by means of its efficient combination with ultrasonography, a well-established clinical imaging modality.

  20. Electret Acoustic Transducer Array For Computerized Ultrasound Risk Evaluation System

    DOEpatents

    Moore, Thomas L.; Fisher, Karl A.

    2005-08-09

    An electret-based acoustic transducer array is provided and may be used in a system for examining tissue. The acoustic transducer array is formed with a substrate that has a multiple distinct cells formed therein. Within each of the distinct cells is positioned an acoustic transducing element formed of an electret material. A conductive membrane is formed over the distinct cells and may be flexible.

  1. Phased-array design for MST and ST radars

    NASA Technical Reports Server (NTRS)

    Ecklund, W. L.

    1986-01-01

    All of the existing radar systems fully dedicated to clear-air radar studies use some type of phased-array antennas. The effects of beam-steering techniques including feed networks and phase shifters; sidelobe control; ground-clutter suppression; low altitude coverage; arrays with integrated radiating elements and feed networks; analysis of coaxial-collinear antennas; use of arrays with multiple beams; and array testing and measure on structural design of the antenna are discussed.

  2. Laser induced ultrasonic phased array using full matrix capture data acquisition and total focusing method.

    PubMed

    Stratoudaki, Theodosia; Clark, Matt; Wilcox, Paul D

    2016-09-19

    Laser ultrasonics is a technique where lasers are employed to generate and detect ultrasound. A data collection method (full matrix capture) and a post processing imaging algorithm, the total focusing method, both developed for ultrasonic arrays, are modified and used in order to enhance the capabilities of laser ultrasonics for nondestructive testing by improving defect detectability and increasing spatial resolution. In this way, a laser induced ultrasonic phased array is synthesized. A model is developed and compared with experimental results from aluminum samples with side drilled holes and slots at depths of 5 - 20 mm from the surface.

  3. Top-orthogonal-to-bottom-electrode (TOBE) CMUT arrays for 3-D ultrasound imaging.

    PubMed

    Sampaleanu, Alex; Zhang, Peiyu; Kshirsagar, Abhijeet; Moussa, Walied; Zemp, Roger J

    2014-02-01

    Two-dimensional ultrasound arrays hold great promise for 3-D imaging; however, wiring of each channel becomes impractical for large arrays or for small-footprint catheter probes for which the number of wires must be limited. Capacitive micromachined ultrasound transducers offer a promising solution for such 2-D array applications, but channel routing is still non-trivial. A top-orthogonal-to-bottom-electrode (TOBE) 2-D CMUT array architecture is presented along with row-column addressing schemes for low-channel-count 3-D ultrasound imaging. An N × N TOBE array is capable of obtaining 3-D images using only 2N channels. An interfacing scheme is presented in which transmit-receive signals are routed along rows while bias voltages are applied along columns, effectively allowing for single-element transmit/receive control. Simulations demonstrated potentially finer resolution and improved side lobe suppression over a previously published row-column-based imaging method. Laser vibrometer testing was done to measure membrane displacement in air and confirmed that single-element air-coupled actuation in transmit mode could be achieved using our proposed interfacing scheme. Acoustic testing was also performed in both transmit and receive modes to characterize the ability of the proposed interfacing scheme to achieve dominant-element transmission and reception in immersion operation. It was seen that membrane displacement in both modes was indeed largely confined to the active area.

  4. S-band antenna phased array communications system

    NASA Technical Reports Server (NTRS)

    Delzer, D. R.; Chapman, J. E.; Griffin, R. A.

    1975-01-01

    The development of an S-band antenna phased array for spacecraft to spacecraft communication is discussed. The system requirements, antenna array subsystem design, and hardware implementation are examined. It is stated that the phased array approach offers the greatest simplicity and lowest cost. The objectives of the development contract are defined as: (1) design of a medium gain active phased array S-band communications antenna, (2) development and test of a model of a seven element planar array of radiating elements mounted in the appropriate cavity matrix, and (3) development and test of a breadboard transmit/receive microelectronics module.

  5. Preliminary work of real-time ultrasound imaging system for 2-D array transducer.

    PubMed

    Li, Xu; Yang, Jiali; Ding, Mingyue; Yuchi, Ming

    2015-01-01

    Ultrasound (US) has emerged as a non-invasive imaging modality that can provide anatomical structure information in real time. To enable the experimental analysis of new 2-D array ultrasound beamforming methods, a pre-beamformed parallel raw data acquisition system was developed for 3-D data capture of 2D array transducer. The transducer interconnection adopted the row-column addressing (RCA) scheme, where the columns and rows were active in sequential for transmit and receive events, respectively. The DAQ system captured the raw data in parallel and the digitized data were fed through the field programmable gate array (FPGA) to implement the pre-beamforming. Finally, 3-D images were reconstructed through the devised platform in real-time.

  6. Multiband Photonic Phased-Array Antenna

    NASA Technical Reports Server (NTRS)

    Tang, Suning

    2015-01-01

    A multiband phased-array antenna (PAA) can reduce the number of antennas on shipboard platforms while offering significantly improved performance. Crystal Research, Inc., has developed a multiband photonic antenna that is based on a high-speed, optical, true-time-delay beamformer. It is capable of simultaneously steering multiple independent radio frequency (RF) beams in less than 1,000 nanoseconds. This high steering speed is 3 orders of magnitude faster than any existing optical beamformer. Unlike other approaches, this technology uses a single controlling device per operation band, eliminating the need for massive optical switches, laser diodes, and fiber Bragg gratings. More importantly, only one beamformer is needed for all antenna elements.

  7. Wavelet Analysis for Acoustic Phased Array

    NASA Astrophysics Data System (ADS)

    Kozlov, Inna; Zlotnick, Zvi

    2003-03-01

    Wavelet spectrum analysis is known to be one of the most powerful tools for exploring quasistationary signals. In this paper we use wavelet technique to develop a new Direction Finding (DF) Algorithm for the Acoustic Phased Array (APA) systems. Utilising multi-scale analysis of libraries of wavelets allows us to work with frequency bands instead of individual frequency of an acoustic source. These frequency bands could be regarded as features extracted from quasistationary signals emitted by a noisy object. For detection, tracing and identification of a sound source in a noisy environment we develop smart algorithm. The essential part of this algorithm is a special interacting procedure of the above-mentioned DF-algorithm and the wavelet-based Identification (ID) algorithm developed in [4]. Significant improvement of the basic properties of a receiving APA pattern is achieved.

  8. PHASED ARRAY FEED CALIBRATION, BEAMFORMING, AND IMAGING

    SciTech Connect

    Landon, Jonathan; Elmer, Michael; Waldron, Jacob; Jones, David; Stemmons, Alan; Jeffs, Brian D.; Warnick, Karl F.; Richard Fisher, J.; Norrod, Roger D.

    2010-03-15

    Phased array feeds (PAFs) for reflector antennas offer the potential for increased reflector field of view and faster survey speeds. To address some of the development challenges that remain for scientifically useful PAFs, including calibration and beamforming algorithms, sensitivity optimization, and demonstration of wide field of view imaging, we report experimental results from a 19 element room temperature L-band PAF mounted on the Green Bank 20 Meter Telescope. Formed beams achieved an aperture efficiency of 69% and a system noise temperature of 66 K. Radio camera images of several sky regions are presented. We investigate the noise performance and sensitivity of the system as a function of elevation angle with statistically optimal beamforming and demonstrate cancelation of radio frequency interference sources with adaptive spatial filtering.

  9. Quantitative flaw characterization with ultrasonic phased arrays

    NASA Astrophysics Data System (ADS)

    Engle, Brady John

    Ultrasonic nondestructive evaluation (NDE) is a critical diagnostic tool in many industries. It is used to characterize potentially dangerous flaws in critical components for aerospace, automotive, and energy applications. The use of phased array transducers allows for the extension of traditional techniques and the introduction of new methods for quantitative flaw characterization. An equivalent flaw sizing technique for use in time-of-flight diffraction setups is presented that provides an estimate of the size and orientation of isolated cracks, surface-breaking cracks, and volumetric flaws such as voids and inclusions. Experimental validation is provided for the isolated crack case. A quantitative imaging algorithm is developed that corrects for system effects and wave propagation, making the images formed directly related to the properties of the scatterer present. Simulated data is used to form images of cylindrical and spherical inclusions. The contributions of different signals to the image formation process are discussed and examples of the quantitative nature of the images are shown.

  10. A Phased Array Approach to Rock Blasting

    SciTech Connect

    Leslie Gertsch; Jason Baird

    2006-07-01

    A series of laboratory-scale simultaneous two-hole shots was performed in a rock simulant (mortar) to record the shock wave interference patterns produced in the material. The purpose of the project as a whole was to evaluate the usefulness of phased array techniques of blast design, using new high-precision delay technology. Despite high-speed photography, however, we were unable to detect the passage of the shock waves through the samples to determine how well they matched the expected interaction geometry. The follow-up mine-scale tests were therefore not conducted. Nevertheless, pattern analysis of the vectors that would be formed by positive interference of the shockwaves from multiple charges in an ideal continuous, homogeneous, isotropic medium indicate the potential for powerful control of blast design, given precise characterization of the target rock mass.

  11. Joint stars phased array radar antenna

    NASA Astrophysics Data System (ADS)

    Shnitkin, Harold

    1994-10-01

    The Joint STARS phased array radar system is capable of performing long range airborne surveillance and was used during the Persian Gulf war on two E8-A aircraft to fly many around-the-clock missions to monitor the Kuwait and Iraq battlefield from a safe distance behind the front lines. This paper is a follow-on to previous publications on the subject of the Joint STARS antenna and deals mainly with mission performance and technical aspects not previously covered. Radar data of troop movements and armament installations will be presented, a brief review of the antenna design is given, followed by technical discussions concerning the three-port interferometry, gain and sidelobe design approach, cost control, range test implementation and future improvements.

  12. Composite ultrasound transducer arrays for operation above 20 MHz

    NASA Astrophysics Data System (ADS)

    Ritter, Timothy A.; Shung, K. Kirk; Geng, Xuecang; Lopath, Patrick D.; Tutwiler, Richard L.; Shrout, Thomas R.

    1999-06-01

    Methods for fabricating and modeling high frequency 2-2 composites and arrays are presented. The composites are suitable for arrays and small aperture single element devices operating above 20 MHz. Coupling coefficients above 0.65 and lateral mode frequencies near 60 MHz were achieved with this composite. Backing and matching materials were prepared to provide up to 70% bandwidth and coaxial cable was used to impedance match the elements to a 50 ohm source. A TPX lens was fabricated and bonded to the face to provide focusing in the elevation direction. Three prototype 4 element 30 MHz linear arrays were designed and built. The designs were analyzed in a time domain finite element analysis program and excellent agreement between theory and experiment was achieved.

  13. Receiver Would Control Phasing of a Phased-Array Antenna

    NASA Technical Reports Server (NTRS)

    Dunn, Charles E.; Young, Lawrence E.

    2006-01-01

    In a proposed digital signal-processing technique, a radio receiver would control the phasing of a phased-array antenna to aim the peaks of the antenna radiation pattern toward desired signal sources while aiming the nulls of the pattern toward interfering signal sources. The technique was conceived for use in a Global Positioning System (GPS) receiver, for which the desired signal sources would be GPS satellites and typical interference sources would be terrestrial objects that cause multipath propagation. The technique could also be used to optimize reception in spread-spectrum cellular-telephone and military communication systems. During reception of radio signals in a conventional phased-array antenna system, received signals at their original carrier frequencies are phase-shifted, then combined by analog circuitry. The combination signal is then subjected to down-conversion and demodulation. In a system according to the proposed technique (see figure), the signal received by each antenna would be subjected to down-conversion, spread-spectrum demodulation, and correlation; this processing would be performed separately from, and simultaneously with, similar processing of signals received by the other antenna elements. Following analog down-conversion to baseband, the signals would be digitized, and all subsequent processing would be digital. In the digital process, residual carriers would be removed and each signal would be correlated with a locally generated model pseudorandum-noise code, all following normal GPS procedure. As part of this procedure, accumulated values would be added in software and the resulting signals would be phase-shifted in software by the amounts necessary to synthesize the desired antenna directional gain pattern of peaks and nulls. The principal advantage of this technique over the conventional radio-frequency-combining technique is that the parallel digital baseband processing of the signals from the various antenna elements would be

  14. Flow integration transform: detecting shapes in matrix-array 3D ultrasound data

    NASA Astrophysics Data System (ADS)

    Stetten, George D.; Caines, Michael; von Ramm, Olaf T.

    1995-03-01

    Matrix-array ultrasound produces real-time 3D images of the heart, by employing a square array of transducers to steer the ultrasound beam in three dimensions electronically with no moving parts. Other 3D modalities such as MR, MUGA, and CT require the use of gated studies, which combine many cardiac cycles to produce a single average cycle. Three- dimensional ultrasound eliminates this restriction, in theory permitting the continuous measurement of cardiac ventricular volume, which we call the volumetricardiogram. Towards implementing the volumetricardiogram, we have developed the flow integration transform (FIT), which operates on a 2D slice within the volumetric ultrasound data. The 3D ultrasound machine's scan converter produces a set of such slices in real time, at any desired location and orientation, to which the FIT may then be applied. Although lacking rotational or scale invariance, the FIT is designed to operate in dedicated hardware where an entire transform could be completed within a few microseconds with present integrated circuit technology. This speed would permit the application of a large battery of test shapes, or the evolution of the test shape to converge on that of the actual target.

  15. SOUND-SPEED TOMOGRAPHY USING FIRST-ARRIVAL TRANSMISSION ULTRASOUND FOR A RING ARRAY

    SciTech Connect

    HUANG, LIANJIE; QUAN, YOULI

    2007-01-31

    Sound-speed tomography images can be used for cancer detection and diagnosis. Tumors have generally higher sound speeds than the surrounding tissue. Quality and resolution of tomography images are primarily determined by the insonification/illumination aperture of ultrasound and the capability of the tomography method for accurately handling heterogeneous nature of the breast. We investigate the capability of an efficient time-of-flight tomography method using transmission ultrasound from a ring array for reconstructing sound-speed images of the breast. The method uses first arrival times of transmitted ultrasonic signals emerging from non-beamforming ultrasound transducers located around a ring. It properly accounts for ray bending within the breast by solving the eikonal equation using a finite-difference scheme. We test and validate the time-of-flight transmission tomography method using synthetic data for numerical breast phantoms containing various objects. In our simulation, the objects are immersed in water within a ring array. Two-dimensional synthetic data are generated using a finite-difference scheme to solve acoustic-wave equation in heterogeneous media. We study the reconstruction accuracy of the tomography method for objects with different sizes and shapes as well as different perturbations from the surrounding medium. In addition, we also address some specific data processing issues related to the tomography. Our tomography results demonstrate that the first-arrival transmission tomography method can accurately reconstruct objects larger than approximately five wavelengths of the incident ultrasound using a ring array.

  16. Sound-speed tomography using first-arrival transmission ultrasound for a ring array

    NASA Astrophysics Data System (ADS)

    Quan, Youli; Huang, Lianjie

    2007-03-01

    Sound-speed tomography images can be used for cancer detection and diagnosis. Tumors have generally higher sound speeds than the surrounding tissue. Quality and resolution of tomography images are primarily determined by the insonification/illumination aperture of ultrasound and the capability of the tomography method for accurately handling heterogeneous nature of the breast. We investigate the capability of an efficient time-of-flight tomography method using transmission ultrasound from a ring array for reconstructing sound-speed images of the breast. The method uses first-arrival times of transmitted ultrasonic signals emerging from non-beamforming ultrasound transducers located around a ring. It properly accounts for ray bending within the breast by solving the eikonal equation using a finite-difference scheme. We test and validate the time-of-flight transmission tomography method using synthetic data for numerical breast phantoms containing various objects. In our simulation, the objects are immersed in water within a ring array. Two-dimensional synthetic data are generated using a finite-difference scheme to solve acoustic-wave equation in heterogeneous media. We study the reconstruction accuracy of the tomography method for objects with different sizes and shapes as well as different perturbations from the surrounding medium. In addition, we also address some specific data processing issues related to the tomography. Our tomography results demonstrate that the first-arrival transmission tomography method can accurately reconstruct objects larger than approximately five wavelengths of the incident ultrasound using a ring array.

  17. Simulation of three-dimensional nonlinear fields of ultrasound therapeutic arrays

    NASA Astrophysics Data System (ADS)

    Yuldashev, P. V.; Khokhlova, V. A.

    2011-05-01

    A novel numerical model was developed to simulate three-dimensional nonlinear fields generated by high intensity focused ultrasound (HIFU) arrays. The model is based on the solution to the Westervelt equation; the developed algorithm makes it possible to model nonlinear pressure fields of periodic waves in the presence of shock fronts localized near the focus. The role of nonlinear effects in a focused beam of a two-dimensional array was investigated in a numerical experiment in water. The array consisting of 256 elements and intensity range on the array elements of up to 10 W/cm2 was considered. The results of simulations have shown that for characteristic intensity outputs of modern HIFU arrays, nonlinear effects play an important role and shock fronts develop in the pressure waveforms at the focus.

  18. Fast Ultrasound Beam Prediction for Linear and Regular Two-dimensional Arrays

    PubMed Central

    Hlawitschka, Mario; McGough, Robert J.; Ferrara, Katherine W.; Kruse, Dustin E.

    2012-01-01

    Real-time beam predictions are highly desirable for the patient-specific computations required in ultrasound therapy guidance and treatment planning. To address the long-standing issue of the computational burden associated with calculating the acoustic field in large volumes, we use graphics processing unit (GPU) computing to accelerate the computation of monochromatic pressure fields for therapeutic ultrasound arrays. In our strategy, we start with acceleration of field computations for single rectangular pistons, and then we explore fast calculations for arrays of rectangular pistons. For single-piston calculations, we employ the fast near-field method (FNM) to accurately and efficiently estimate the complex near-field wave patterns for rectangular pistons in homogeneous media. The FNM is compared with the Rayleigh-Sommerfeld method (RSM) for the number of abscissas required in the respective numerical integrations to achieve 1%, 0.1%, and 0.01% accuracy in the field calculations. Next, algorithms are described for accelerated computation of beam patterns for two different ultrasound transducer arrays: regular 1-D linear arrays and regular 2-D linear arrays. For the array types considered, the algorithm is split into two parts: 1) the computation of the field from one piston, and 2) the computation of a piston-array beam pattern based on a pre-computed field from one piston. It is shown that the process of calculating an array beam pattern is equivalent to the convolution of the single-piston field with the complex weights associated with an array of pistons. Our results show that the algorithms for computing monochromatic fields from linear and regularly spaced arrays can benefit greatly from GPU computing hardware, exceeding the performance of an expensive CPU by more than 100 times using an inexpensive GPU board. For a single rectangular piston, the FNM method facilitates volumetric computations with 0.01% accuracy at rates better than 30 ns per field point

  19. Fast ultrasound beam prediction for linear and regular two-dimensional arrays.

    PubMed

    Hlawitschka, Mario; McGough, Robert J; Ferrara, Katherine W; Kruse, Dustin E

    2011-09-01

    Real-time beam predictions are highly desirable for the patient-specific computations required in ultrasound therapy guidance and treatment planning. To address the longstanding issue of the computational burden associated with calculating the acoustic field in large volumes, we use graphics processing unit (GPU) computing to accelerate the computation of monochromatic pressure fields for therapeutic ultrasound arrays. In our strategy, we start with acceleration of field computations for single rectangular pistons, and then we explore fast calculations for arrays of rectangular pistons. For single-piston calculations, we employ the fast near-field method (FNM) to accurately and efficiently estimate the complex near-field wave patterns for rectangular pistons in homogeneous media. The FNM is compared with the Rayleigh-Sommerfeld method (RSM) for the number of abscissas required in the respective numerical integrations to achieve 1%, 0.1%, and 0.01% accuracy in the field calculations. Next, algorithms are described for accelerated computation of beam patterns for two different ultrasound transducer arrays: regular 1-D linear arrays and regular 2-D linear arrays. For the array types considered, the algorithm is split into two parts: 1) the computation of the field from one piston, and 2) the computation of a piston-array beam pattern based on a pre-computed field from one piston. It is shown that the process of calculating an array beam pattern is equivalent to the convolution of the single-piston field with the complex weights associated with an array of pistons. Our results show that the algorithms for computing monochromatic fields from linear and regularly spaced arrays can benefit greatly from GPU computing hardware, exceeding the performance of an expensive CPU by more than 100 times using an inexpensive GPU board. For a single rectangular piston, the FNM method facilitates volumetric computations with 0.01% accuracy at rates better than 30 ns per field point

  20. A novel method to design sparse linear arrays for ultrasonic phased array.

    PubMed

    Yang, Ping; Chen, Bin; Shi, Ke-Ren

    2006-12-22

    In ultrasonic phased array testing, a sparse array can increase the resolution by enlarging the aperture without adding system complexity. Designing a sparse array involves choosing the best or a better configuration from a large number of candidate arrays. We firstly designed sparse arrays by using a genetic algorithm, but found that the arrays have poor performance and poor consistency. So, a method based on the Minimum Redundancy Linear Array was then adopted. Some elements are determined by the minimum-redundancy array firstly in order to ensure spatial resolution and then a genetic algorithm is used to optimize the remaining elements. Sparse arrays designed by this method have much better performance and consistency compared to the arrays designed only by a genetic algorithm. Both simulation and experiment confirm the effectiveness.

  1. Quantitative ultrasound images generated by a PE-CMOS sensor array: scatter modeling and image restoration

    NASA Astrophysics Data System (ADS)

    Liu, Chu-Chuan; Lo, Shih-Chung Ben; Freedman, Matthew T.; Lasser, Marvin E.; Lasser, Bob; Kula, John; Wang, Yue Joseph

    2007-03-01

    In the projection geometry, the detected ultrasound energy through a soft-tissue is mainly attributed to the attenuated primary intensity and the scatter intensity. In order to extract ultrasound image of attenuated primary beam out of the detected raw data, the scatter component must be carefully quantified for restoring the original image. In this study, we have designed a set of apparatus to modeling the ultrasound scattering in soft-tissue. The employed ultrasound imaging device was a C-Scan (projection) prototype using a 4th generation PE-CMOS sensor array (model I400, by Imperium Inc., Silver Spring, MD) as the detector. Right after the plane wave ultrasound transmitting through a soft-tissue mimicking material (Zerdine, by CIRS Inc., Norfolk, VA), a ring aperture is used to collimate the signal before reaching the acoustic lens and the PE-CMOS sensor. Three sets of collimated ring images were acquired and analyzed to obtain the scattering components as a function of the off-center distance. Several pathological specimens and breast phantoms consisting of simulated breast tissue with masses, cysts and microcalcifications were imaged by the same C-Scan imaging prototype. The restoration of these ultrasound images were performed by using a standard deconvolution computation. Our study indicated that the resultant images show shaper edges and detailed features as compared to their unprocessed counterparts.

  2. Microfabrication of electrode patterns for high-frequency ultrasound transducer arrays.

    PubMed

    Bernassau, Anne L; García-Gancedo, Luis; Hutson, David; Démoré, Christine E M; McAneny, Jim J; Button, Tim W; Cochran, Sandy

    2012-08-01

    High-frequency ultrasound is needed for medical imaging with high spatial resolution. A key issue in the development of ultrasound imaging arrays to operate at high frequencies (≥30 MHz) is the need for photolithographic patterning of array electrodes. To achieve this directly on 1-3 piezocomposite, the material requires not only planar, parallel, and smooth surfaces, but also an epoxy composite filler that is resistant to chemicals, heat, and vacuum. This paper reports, first, on the surface finishing of 1-3 piezocomposite materials by lapping and polishing. Excellent surface flatness has been obtained, with an average surface roughness of materials as low as 3 nm and step heights between ceramic/polymer of ∼80 nm. Subsequently, high-frequency array elements were patterned directly on top of these surfaces using a photolithography process. A 30-MHz linear array electrode pattern with 50-μm element pitch has been patterned on the lapped and polished surface of a high-frequency 1-3 piezocomposite. Excellent electrode edge definition and electrical contact to the composite were obtained. The composite has been lapped to a final thickness of ∼55 μm. Good adhesion of electrodes on the piezocomposite has been achieved and electrical impedance measurements have demonstrated their basic functionality. The array was then packaged, and acoustic pulse-echo measurements were performed. These results demonstrate that direct patterning of electrodes by photolithography on 1-3 piezocomposite is feasible for fabrication of high-frequency ultrasound arrays. Furthermore, this method is more conducive to mass production than other reported array fabrication techniques.

  3. Feasibility of ultrasound phase contrast for heating localization.

    PubMed

    Farny, Caleb H; Clement, Greg T

    2008-03-01

    Ultrasound-based methods for temperature monitoring could greatly assist focused ultrasound visualization and treatment planning based on sound speed-induced change in phase as a function of temperature. A method is presented that uses reflex transmission integration, planar projection, and tomographic reconstruction techniques to visualize phase contrast by measuring the sound field before and after heat deposition. Results from experiments and numerical simulations employing a through-transmission setup are presented to demonstrate feasibility of using phase contrast methods for identifying temperature change. A 1.088-MHz focused transducer was used to interrogate a medium with a phase contrast feature, following measurement of the baseline reference field with a hydrophone. A thermal plume in water and a tissue phantom with multiple water columns was used in separate experiments to produce a phase contrast. The reference and phase contrast field scans were numerically backprojected and the phase difference correctly identified the position and orientation of the features. The peak temperature reconstructed from the phase shift was within 0.2 degrees C of the measured temperature in the plume. Simulated results were in good agreement with experimental results. Finally, employment of reflex transmission imaging techniques for adopting a pulse-echo arrangement was simulated, and its future experimental application is discussed.

  4. Reconfigurable Wave Velocity Transmission Lines for Phased Arrays

    NASA Technical Reports Server (NTRS)

    Host, Nicholas Keith; Chen, Chi-Chih; Volakis, John L.

    2012-01-01

    This presentation discussed a novel phased array with an emphasis to simplify the array feed. Specifically, we will demonstrate a simple, low cost feeding approach by mechanically controlling the substrate thickness. The array feed lines are constructed from parallel plate transmission lines whose thickness are adjusted to control their effective dielectric constant (Epsilon_eff). As a result the phase delay/excitation at each array element will be adjusted per desired beam direction. The proposed antenna elements will be overlapping dipoles operating over a 2:1 bandwidth in the Ku-Band spectrum. Preliminary simulation and experimental demonstration of such an array will be presented.

  5. Microstrip technology and its application to phased array compensation

    NASA Technical Reports Server (NTRS)

    Dudgeon, J. E.; Daniels, W. D.

    1972-01-01

    A systematic analysis of mutual coupling compensation using microstrip techniques is presented. A method for behind-the-array coupling of a phased antenna array is investigated as to its feasibility. The matching scheme is tried on a rectangular array of one half lambda 2 dipoles, but it is not limited to this array element or geometry. In the example cited the values of discrete components necessary were so small an L-C network is needed for realization. Such L-C tanks might limit an otherwise broadband array match, however, this is not significant for this dipole array. Other areas investigated were balun feeding and power limits of spiral antenna elements.

  6. Real-time photoacoustic and ultrasound imaging: a simple solution for clinical ultrasound systems with linear arrays.

    PubMed

    Montilla, Leonardo G; Olafsson, Ragnar; Bauer, Daniel R; Witte, Russell S

    2013-01-07

    Recent clinical studies have demonstrated that photoacoustic imaging (PAI) provides important diagnostic information during a routine breast exam for cancer. PAI enhances contrast between blood vessels and background tissue, which can help characterize suspicious lesions. However, most PAI systems are either not compatible with commercial ultrasound systems or inefficiently deliver light to the region of interest, effectively reducing the sensitivity of the technique. To address and potentially overcome these limitations, we developed an accessory for a standard linear ultrasound array that optimizes light delivery for PAI. The photoacoustic enabling device (PED) exploits an optically transparent acoustic reflector to help direct laser illumination to the region of interest. This study compares the PED with standard fiber bundle illumination in scattering and non-scattering media. In scattering media with the same incident fluence, the PED enhanced the photoacoustic signal by 18 dB at a depth of 5 mm and 6 dB at a depth of 20 mm. To demonstrate in vivo feasibility, we also used the device to image a mouse with a pancreatic tumor. The PED identified blood vessels at the periphery of the tumor, suggesting that PAI provides complementary contrast to standard pulse echo ultrasound. The PED is a simple and inexpensive solution that facilitates the translation of PAI technology to the clinic for routine screening of breast cancer.

  7. Echo decorrelation imaging of ex vivo HIFU and bulk ultrasound ablation using image-treat arrays

    NASA Astrophysics Data System (ADS)

    Fosnight, Tyler R.; Hooi, Fong Ming; Colbert, Sadie B.; Keil, Ryan D.; Barthe, Peter G.; Mast, T. Douglas

    2017-03-01

    In this study, the ability of ultrasound echo decorrelation imaging to map and predict heat-induced cell death was tested using bulk ultrasound thermal ablation, high intensity focused ultrasound (HIFU) thermal ablation, and pulse-echo imaging of ex vivo liver tissue by a custom image-treat array. Tissue was sonicated at 5.0 MHz using either pulses of unfocused ultrasound (N=12) (7.5 s, 50.9-101.8 W/cm2 in situ spatial-peak, temporal-peak intensity) for bulk ablation or focused ultrasound (N=21) (1 s, 284-769 W/cm2 in situ spatial-peak, temporal-peak intensity and focus depth of 10 mm) for HIFU ablation. Echo decorrelation and integrated backscatter (IBS) maps were formed from radiofrequency pulse-echo images captured at 118 frames per second during 5.0 s rest periods, beginning 1.1 s after each sonication pulse. Tissue samples were frozen at -80˚C, sectioned, vitally stained, imaged, and semi-automatically segmented for receiver operating characteristic (ROC) analysis. ROC curves were constructed to assess prediction performance for echo decorrelation and IBS. Logarithmically scaled mean echo decorrelation in non-ablated and ablated tissue regions before and after electronic noise and motion correction were compared. Ablation prediction by echo decorrelation and IBS was significant for both focused and bulk ultrasound ablation. The log10-scaled mean echo decorrelation was significantly greater in regions of ablation for both HIFU and bulk ultrasound ablation. Echo decorrelation due to electronic noise and motion was significantly reduced by correction. These results suggest that ultrasound echo decorrelation imaging is a promising approach for real-time prediction of heat-induced cell death for guidance and monitoring of clinical thermal ablation, including radiofrequency ablation and HIFU.

  8. Ultrasound therapy transducers with space-filling non-periodic arrays.

    PubMed

    Raju, Balasundar I; Hall, Christopher S; Seip, Ralf

    2011-05-01

    Ultrasound transducers designed for therapeutic purposes such as tissue ablation, histotripsy, or drug delivery require large apertures for adequate spatial localization while providing sufficient power and steerability without the presence of secondary grating lobes. In addition, it is highly preferred to minimize the total number of channels and to maintain simplicity in electrical matching network design. To this end, we propose array designs that are both space-filling and non-periodic in the placement of the elements. Such array designs can be generated using the mathematical concept of non-periodic or aperiodic tiling (tessellation) and can lead to reduced grating lobes while maintaining full surface area coverage to deliver maximum power. For illustration, we designed two 2-D space-filling therapeutic arrays with 128 elements arranged on a spherical shell. One was based on the two-shape Penrose rhombus tiling, and the other was based on a single rectangular shape arranged non-periodically. The steerability performance of these arrays was studied using acoustic field simulations. For comparison, we also studied two other arrays, one with circular elements distributed randomly, and the other a periodic array with square elements. Results showed that the two space-filling non-periodic arrays were able to steer to treat a volume of 16 x 16 x 20 mm while ensuring that the grating lobes were under -10 dB compared with the main lobe. The rectangular non-periodic array was able to generate two and half times higher power than the random circles array. The rectangular array was then fabricated by patterning the array using laser scribing methods and its steerability performance was validated using hydrophone measurements. This work demonstrates that the concept of space-filling aperiodic/non-periodic tiling can be used to generate therapy arrays that are able to provide higher power for the same total transducer area compared with random arrays while maintaining

  9. Thermal dispersion method for an ultrasonic phased-array transducer

    NASA Astrophysics Data System (ADS)

    Choi, Euna; Lee, Wonseok; Roh, Yongrae

    2016-07-01

    When the driving voltage of an ultrasonic transducer is increased to improve the quality of ultrasound images, heat is generated inside the transducer, which can burn the patient’s skin and degrade transducer performance. In this study, the method to disperse the heat inside an ultrasonic phased-array transducer has been examined. The mechanism of temperature rise due to heat generation inside the transducer was investigated by numerical analysis and the effects of the thermal properties of the components of the transducer such as specific heat and thermal conductivity on the temperature rise were analyzed. On the basis of the results, a heat-dispersive structure was devised to reduce the temperature at the surface of the acoustic lens of the transducer. Prototype transducers were fabricated to check the efficacy of the heat-dispersive structure. By experiments, we have confirmed that the new heat-dispersive structure can reduce the internal temperature by as much as 50% in comparison with the conventional structure, which confirms the validity of the thermal dispersion mechanism developed in this work.

  10. Optimizing Satellite Communications With Adaptive and Phased Array Antennas

    NASA Technical Reports Server (NTRS)

    Ingram, Mary Ann; Romanofsky, Robert; Lee, Richard Q.; Miranda, Felix; Popovic, Zoya; Langley, John; Barott, William C.; Ahmed, M. Usman; Mandl, Dan

    2004-01-01

    A new adaptive antenna array architecture for low-earth-orbiting satellite ground stations is being investigated. These ground stations are intended to have no moving parts and could potentially be operated in populated areas, where terrestrial interference is likely. The architecture includes multiple, moderately directive phased arrays. The phased arrays, each steered in the approximate direction of the satellite, are adaptively combined to enhance the Signal-to-Noise and Interference-Ratio (SNIR) of the desired satellite. The size of each phased array is to be traded-off with the number of phased arrays, to optimize cost, while meeting a bit-error-rate threshold. Also, two phased array architectures are being prototyped: a spacefed lens array and a reflect-array. If two co-channel satellites are in the field of view of the phased arrays, then multi-user detection techniques may enable simultaneous demodulation of the satellite signals, also known as Space Division Multiple Access (SDMA). We report on Phase I of the project, in which fixed directional elements are adaptively combined in a prototype to demodulate the S-band downlink of the EO-1 satellite, which is part of the New Millennium Program at NASA.

  11. Coherent scattering of phase conjugate ultrasound waves in bubbly media.

    PubMed

    Shirkovskiy, Pavel; Preobrazhensky, Vladimir L; Pernod, Philippe

    2015-04-01

    Wave phase conjugation of ultrasound scattered by clouds of micro-bubbles in water has been studied experimentally and expounded theoretically. The clouds of microbubbles with variable concentration and sizes have been generated here using electrolytic method. The wave front of the ultrasound beam of frequency 10 MHz was reversed by a parametric phase conjugator. The signal of phase conjugate wave (PCW) detected by an acoustic transceiver was compared with the signal of the wave scattered toward the phase conjugator. The scattered wave (SW) signal was detected by the transducer substituting the phase conjugator. It is shown that, in contrast with stochastic SW signal, wave phase conjugation forms regular PCW signal on the transceiver in spite of random distribution of the scatterers. The PCW signal is found to be much more sensitive to variations of bubbles concentration comparing with the mean value of the SW amplitude. Moreover, the relative error of measurements of PCW signals is much smaller than that of the SW signal. The revealed properties of phase conjugate waves are applicable for testing of concentration of scatterers in dispersive systems.

  12. Three-dimensional mid-air acoustic manipulation by ultrasonic phased arrays.

    PubMed

    Ochiai, Yoichi; Hoshi, Takayuki; Rekimoto, Jun

    2014-01-01

    The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes. The acoustic axis of the ultrasound beam in conventional studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers. In the present study, we considered extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. Our manipulation system has two original features. One is the direction of the ultrasound beam, which is arbitrary because the force acting toward its centre is also utilised. The other is the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed and ultrasonic phased arrays. We experimentally confirmed that expanded-polystyrene particles of 0.6 mm, 1 mm, and 2 mm in diameter could be manipulated by our proposed method.

  13. Three-Dimensional Mid-Air Acoustic Manipulation by Ultrasonic Phased Arrays

    PubMed Central

    Ochiai, Yoichi; Hoshi, Takayuki; Rekimoto, Jun

    2014-01-01

    The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes. The acoustic axis of the ultrasound beam in conventional studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers. In the present study, we considered extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. Our manipulation system has two original features. One is the direction of the ultrasound beam, which is arbitrary because the force acting toward its centre is also utilised. The other is the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed and ultrasonic phased arrays. We experimentally confirmed that expanded-polystyrene particles of 0.6 mm, 1 mm, and 2 mm in diameter could be manipulated by our proposed method. PMID:24849371

  14. Phased Array Transmit Antenna for a Satellite

    NASA Technical Reports Server (NTRS)

    Huggins, R. W.; Heisen, P. T.; Miller, G. E.; McMeen, D. J.; Perko, K. L.

    1999-01-01

    Active phased array antennas with electronically scanned beams offer advantages over high gain parabolic dish antennas currently used on spacecraft. Benefits include the elimination of deployable structures, no moving parts, and no torque disturbances that moving antennas impart to the spacecraft. The latter results in the conservation of spacecraft power, and the ability to take precision optical data while transmitting data. Such an antenna has been built under a contract from NASA Goddard Space Flight Center for the New Millennium Program EO- 1 satellite where it will act as the primary highspeed scientific data communication link. The antenna operates at X-band, has an integral controller and power conditioner, communicates with the spacecraft over a 1773 optical data bus, and is space qualified for low earth orbit (705 Km altitude). The nominal mission length is one year, and the operational requirement is for one 10 minute transmission a day over Spitsbergen, Norway. Details of the antenna and its performance will be described in the following paper.

  15. Phased Array Transmit Antenna for a Satellite

    NASA Technical Reports Server (NTRS)

    Huggins, R. W.; Heisen, P. T.; Miller, G. E.; McMeen, D. J.; Perko, K. L.

    1999-01-01

    Active phased array antennas with electronically scanned beams offer advantages over high gain parabolic dish antennas currently used on spacecraft. Benefits include the elimination of deployable structures, no moving parts, and no torque disturbances that moving antennas impart to the spacecraft. The latter results in the conservation of spacecraft power, and the ability to take precision optical data while transmitting data. Such an antenna has been built under a contract from NASA Goddard Space Flight Center for the New Millennium Program EO- 1 satellite where it will act as the primary highspeed scientific data communication link. The antenna operates at X-band, has an integral controller and power conditioner, communicates with the spacecraft over a 1773 optical data bus, and is space qualified for low earth orbit (705 Km altitude). The nominal mission length is one year, and the operational requirement is for one 10 minute transmission a day over Spitsbergen, Norway. Details of the antenna and its performance will be described in the following paper.

  16. In vivo visualization of robotically implemented synthetic tracked aperture ultrasound (STRATUS) imaging system using curvilinear array

    NASA Astrophysics Data System (ADS)

    Zhang, Haichong K.; Aalamifar, Fereshteh; Boctor, Emad M.

    2016-04-01

    Synthetic aperture for ultrasound is a technique utilizing a wide aperture in both transmit and receive to enhance the ultrasound image quality. The limitation of synthetic aperture is the maximum available aperture size limit determined by the physical size of ultrasound probe. We propose Synthetic-Tracked Aperture Ultrasound (STRATUS) imaging system to overcome the limitation by extending the beamforming aperture size through ultrasound probe tracking. With a setup involving a robotic arm, the ultrasound probe is moved using the robotic arm, while the positions on a scanning trajectory are tracked in real-time. Data from each pose are synthesized to construct a high resolution image. In previous studies, we have demonstrated the feasibility through phantom experiments. However, various additional factors such as real-time data collection or motion artifacts should be taken into account when the in vivo target becomes the subject. In this work, we build a robot-based STRATUS imaging system with continuous data collection capability considering the practical implementation. A curvilinear array is used instead of a linear array to benefit from its wider capture angle. We scanned human forearms under two scenarios: one submerged the arm in the water tank under 10 cm depth, and the other directly scanned the arm from the surface. The image contrast improved 5.51 dB, and 9.96 dB for the underwater scan and the direct scan, respectively. The result indicates the practical feasibility of STRATUS imaging system, and the technique can be potentially applied to the wide range of human body.

  17. Forward-Looking Intracardiac Ultrasound Imaging Using a 1-D CMUT Array Integrated With Custom Front-End Electronics

    PubMed Central

    Nikoozadeh, Amin; Wygant, Ira O.; Lin, Der-Song; Oralkan, Ömer; Ergun, A. Sanlı; Stephens, Douglas N.; Thomenius, Kai E.; Dentinger, Aaron M.; Wildes, Douglas; Akopyan, Gina; Shivkumar, Kalyanam; Mahajan, Aman; Sahn, David J.; Khuri-Yakub, Butrus T.

    2009-01-01

    Minimally invasive catheter-based electrophysiological (EP) interventions are becoming a standard procedure in diagnosis and treatment of cardiac arrhythmias. As a result of technological advances that enable small feature sizes and a high level of integration, nonfluoroscopic intracardiac echocardiography (ICE) imaging catheters are attracting increasing attention. ICE catheters improve EP procedural guidance while reducing the undesirable use of fluoroscopy, which is currently the common catheter guidance method. Phased-array ICE catheters have been in use for several years now, although only for side-looking imaging. We are developing a forward-looking ICE catheter for improved visualization. In this effort, we fabricate a 24-element, fine-pitch 1-D array of capacitive micromachined ultrasonic transducers (CMUT), with a total footprint of 1.73 mm × 1.27 mm. We also design a custom integrated circuit (IC) composed of 24 identical blocks of transmit/receive circuitry, measuring 2.1 mm × 2.1 mm. The transmit circuitry is capable of delivering 25-V unipolar pulses, and the receive circuitry includes a transimpedance preamplifier followed by an output buffer. The CMUT array and the custom IC are designed to be mounted at the tip of a 10-Fr catheter for high-frame-rate forward-looking intracardiac imaging. Through-wafer vias incorporated in the CMUT array provide access to individual array elements from the back side of the array. We successfully flip-chip bond a CMUT array to the custom IC with 100% yield. We coat the device with a layer of polydimethylsiloxane (PDMS) to electrically isolate the device for imaging in water and tissue. The pulse-echo in water from a total plane reflector has a center frequency of 9.2 MHz with a 96% fractional bandwidth. Finally, we demonstrate the imaging capability of the integrated device on commercial phantoms and on a beating ex vivo rabbit heart (Langendorff model) using a commercial ultrasound imaging system. PMID:19126489

  18. Guided wave phased array beamforming and imaging in composite plates.

    PubMed

    Yu, Lingyu; Tian, Zhenhua

    2016-05-01

    This paper describes phased array beamforming using guided waves in anisotropic composite plates. A generic phased array algorithm is presented, in which direction dependent guided wave parameters and the energy skew effect are considered. This beamforming at an angular direction is achieved based on the classic delay-and-sum principle by applying phase delays to signals received at array elements and adding up the delayed signals. The phase delays are determined with the goal to maximize the array output at the desired direction and minimize it otherwise. For array characterization, the beam pattern of rectangular grid arrays in composite plates is derived. In addition to the beam pattern, the beamforming factor in terms of wavenumber distribution is defined to provide intrinsic explanations for phased array beamforming. The beamforming and damage detection in a composite plate are demonstrated using rectangular grid arrays made by a non-contact scanning laser Doppler vibrometer. Detection images of the composite plate with multiple surface defects at various directions are obtained. The results show that the guided wave phased array method is a potential effective method for rapid inspection of large composite structures.

  19. In vivo three-dimensional photoacoustic imaging based on a clinical matrix array ultrasound probe

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Erpelding, Todd N.; Jankovic, Ladislav; Guo, Zijian; Robert, Jean-Luc; David, Guillaume; Wang, Lihong V.

    2012-06-01

    We present an integrated photoacoustic and ultrasonic three-dimensional (3-D) volumetric imaging system based on a two-dimensional (2-D) matrix array ultrasound probe. A wavelength-tunable dye laser pumped by a Q-switched Nd:YAG laser serves as the light source and a modified commercial ultrasound imaging system (iU22, Philips Healthcare) with a 2-D array transducer (X7-2, Philips Healthcare) detects both the pulse-echo ultrasound and photoacoustic signals. A multichannel data acquisition system acquires the RF channel data. The imaging system enables rendering of co-registered 3-D ultrasound and photoacoustic images without mechanical scanning. The resolution along the azimuth, elevation, and axial direction are measured to be 0.69, 0.90 and 0.84 mm for photoacoustic imaging. In vivo 3-D photoacoustic mapping of the sentinel lymph node was demonstrated in a rat model using methylene blue dye. These results highlight the clinical potential of 3-D PA imaging for identification of sentinel lymph nodes for cancer staging in humans.

  20. Beamforming of Ultrasound Signals from 1-D and 2-D Arrays under Challenging Imaging Conditions

    NASA Astrophysics Data System (ADS)

    Jakovljevic, Marko

    Beamforming of ultrasound signals in the presence of clutter, or partial aperture blockage by an acoustic obstacle can lead to reduced visibility of the structures of interest and diminished diagnostic value of the resulting image. We propose new beamforming methods to recover the quality of ultrasound images under such challenging conditions. Of special interest are the signals from large apertures, which are more susceptible to partial blockage, and from commercial matrix arrays that suffer from low sensitivity due to inherent design/hardware limitations. A coherence-based beamforming method designed for suppressing the in vivo clutter, namely Short-lag Spatial Coherence (SLSC) Imaging, is first implemented on a 1-D array to enhance visualization of liver vasculature in 17 human subjects. The SLSC images show statistically significant improvements in vessel contrast and contrast-to-noise ratio over the matched B-mode images. The concept of SLSC imaging is then extended to matrix arrays, and the first in vivo demonstration of volumetric SLSC imaging on a clinical ultrasound system is presented. The effective suppression of clutter via volumetric SLSC imaging indicates it could potentially compensate for the low sensitivity associated with most commercial matrix arrays. The rest of the dissertation assesses image degradation due to elements blocked by ribs in a transthoracic scan. A method to detect the blocked elements is demonstrated using simulated, ex vivo, and in vivo data from the fully-sampled 2-D apertures. The results show that turning off the blocked elements both reduces the near-field clutter and improves visibility of anechoic/hypoechoic targets. Most importantly, the ex vivo data from large synthetic apertures indicates that the adaptive weighing of the non-blocked elements can recover the loss of focus quality due to periodic rib structure, allowing large apertures to realize their full resolution potential in transthoracic ultrasound.

  1. An Automated Dosing Method for a HIFU Device Containing Multiple Phased Arrays

    NASA Astrophysics Data System (ADS)

    Zeng, Xiaozheng Jenny; Barnes, Steve; Sekins, K. Michael

    2010-03-01

    A device containing multiple 2D therapeutic and imaging ultrasound phased arrays is proposed for acoustic hemostasis applications. An automated dosing algorithm selects the optimal combination of therapeutic phased arrays and calculates the acoustic power required of each array. Simulations demonstrate that therapeutic temperatures (70° Carrays mounted in panels that embody a cuff, patch or blanket type device. Using array and tissue target positions, an algorithm automatically estimates the available power at the target using depth, beam steering angles, directivity and the tissue properties. The individual array powers are then assigned using a power balance (equalization) algorithm that adjusts the size and shape of the heated target region. The treatment volume is adjusted by dynamically scanning the individual foci through patterns in the target zone. The temperature elevation was simulated using 3D finite element models. Numerical simulations were performed on the therapeutic performance of the device. The surface acoustic intensity of the arrays was maintained below a threshold associated with avoidance of skin burning. The total absorbed power in the target volume (8 mm diameter spherical target) producing therapeutic temperatures was 4 to 5 W for 30 second continuous dosing times. The spatial-peak-time-averaged intensity in the target focal zone was ≈600 W/cm2, below the inertial cavitation threshold for these conditions. Simulations showed that the proposed ultrasound device yielded a relatively uniform temperature distribution in the target volume.

  2. A Phased Array Coil for Human Cardiac Imaging

    PubMed Central

    Constantinides, Chris D.; Westgate, Charles R.; O'Dell, Walter G.; Zerhouni, Elias A.; McVeigh, Elliot R.

    2007-01-01

    A prototype cardiac phased array receiver coil was constructed that comprised a cylindrical array and a separate planar array. Both arrays had two coil loops with the same coil dimensions. Data acquisition with the cylindrical array placed on the human chest, and the planar array placed under the back, yielded an overall enhancement of the signal-to-noise ratio (SNR) over the entire heart by a factor of 1.1–2.85 over a commercially available flexible coil and a commercially available four-loop planar phased array coil. This improvement in SNR can be exploited in cardiac imaging to increase the spatial resolution and reduce the image acquisition time. PMID:7674903

  3. 3-D ultrasound imaging using a forward-looking CMUT ring array for intravascular/intracardiac applications.

    PubMed

    Yeh, David T; Oralkan, Omer; Wygant, Ira O; O'Donnell, Matthew; Khuri-Yakub, Butrus T

    2006-06-01

    Forward-viewing ring arrays can enable new applications in intravascular and intracardiac ultrasound. This work presents compelling, full-synthetic, phased-array volumetric images from a forward-viewing capacitive micromachined ultrasonic transducer (CMUT) ring array wire bonded to a custom integrated circuit front end. The CMUT ring array has a diameter of 2 mm and 64 elements each 100 microm x 100 microm in size. In conventional mode, echo signals received from a plane reflector at 5 mm had 70% fractional bandwidth around a center frequency of 8.3 MHz. In collapse mode, 69% fractional bandwidth is measured around 19 MHz. Measured signal-to-noise ratio (SNR) of the echo averaged 16 times was 29 dB for conventional operation and 35 dB for collapse mode. B-scans were generated of a target consisting of steel wires 0.3 mm in diameter to determine resolution performance. The 6 dB axial and lateral resolutions for the B-scan of the wire target are 189 microm and 0.112 radians for 8 MHz, and 78 microm and 0.051 radians for 19 MHz. A reduced firing set suitable for real-time, intravascular applications was generated and shown to produce acceptable images. Rendered three-dimensional (3-D) images of a Palmaz-Schatz stent also are shown, demonstrating that the imaging quality is sufficient for practical applications.

  4. Effects of Non-Elevation-Focalized Linear Array Transducer on Ultrasound Plane-Wave Imaging

    PubMed Central

    Wang, Congzhi; Xiao, Yang; Xia, Jingjing; Qiu, Weibao; Zheng, Hairong

    2016-01-01

    Plane-wave ultrasound imaging (PWUS) has become an important method of ultrasound imaging in recent years as its frame rate has exceeded 10,000 frames per second, allowing ultrasound to be used for two-dimensional shear wave detection and functional brain imaging. However, compared to the traditional focusing and scanning method, PWUS images always suffer from a degradation of lateral resolution and contrast. To improve the image quality of PWUS, many different beamforming algorithms have been proposed and verified. Yet the influence of transducer structure is rarely studied. For this paper, the influence of using an acoustic lens for PWUS was evaluated. Two linear array transducers were fabricated. One was not self-focalized in the elevation direction (non-elevation-focalized transducer, NEFT); the other one was a traditional elevation-focalized transducer (EFT). An initial simulation was conducted to show the influence of elevation focusing. Then the images obtained with NEFT on a standard ultrasound imaging phantom were compared with those obtained with EFT. It was demonstrated that, in a relatively deep region, the contrast of an NEFT image is better than that of an EFT image. These results indicate that a more sophisticated design of ultrasound transducer would further improve the image quality of PWUS. PMID:27845751

  5. Reconfigurable Wave Velocity Transmission Lines for Phased Arrays

    NASA Technical Reports Server (NTRS)

    Host, Nick; Chen, Chi-Chih; Volakis, John L.; Miranda, Felix

    2013-01-01

    Phased array antennas showcase many advantages over mechanically steered systems. However, they are also more complex, heavy and most importantly costly. This presentation paper presents a concept which overcomes these detrimental attributes by eliminating all of the phase array backend (including phase shifters). Instead, a wave velocity reconfigurable transmission line is used in a series fed array arrangement to allow phase shifting with one small (100mil) mechanical motion. Different configurations of the reconfigurable wave velocity transmission line are discussed and simulated and experimental results are presented.

  6. Phased array feed testing for astronomy with ASKAP

    NASA Astrophysics Data System (ADS)

    Chippendale, Aaron P.; O'Sullivan, John; Reynolds, John; Gough, Russell; Hayman, Douglas; Hay, Stuart

    2010-10-01

    Phased array feeds enable radio telescopes to make faster surveys with fewer antennas. This paper presents testing of a phased array feed prototype to verify design methods for array feeds of the Australian Square Kilometre Array Pathfinder (ASKAP). We have tested a 5 × 4 port × 2 polarisation connected-chequerboard array at the prime focus of a 12 m diameter parabolic reflector. This prototype system currently achieves a system-temperature-on-efficiency ratio Tsys/η of 134 K at 1260 MHz and operates from 700 MHz to 1,800 MHz. The larger 94 port × 2 polarisation phased array feed being developed for ASKAP has a target Tsys/η of 50 K. The time taken by a radio telescope to survey a fixed area of sky to a fixed sensitivity is proportional to (Tsys/η)2.

  7. Cumulative phase delay imaging for contrast-enhanced ultrasound tomography

    NASA Astrophysics Data System (ADS)

    Demi, Libertario; van Sloun, Ruud J. G.; Wijkstra, Hessel; Mischi, Massimo

    2015-11-01

    Standard dynamic-contrast enhanced ultrasound (DCE-US) imaging detects and estimates ultrasound-contrast-agent (UCA) concentration based on the amplitude of the nonlinear (harmonic) components generated during ultrasound (US) propagation through UCAs. However, harmonic components generation is not specific to UCAs, as it also occurs for US propagating through tissue. Moreover, nonlinear artifacts affect standard DCE-US imaging, causing contrast to tissue ratio reduction, and resulting in possible misclassification of tissue and misinterpretation of UCA concentration. Furthermore, no contrast-specific modality exists for DCE-US tomography; in particular speed-of-sound changes due to UCAs are well within those caused by different tissue types. Recently, a new marker for UCAs has been introduced. A cumulative phase delay (CPD) between the second harmonic and fundamental component is in fact observable for US propagating through UCAs, and is absent in tissue. In this paper, tomographic US images based on CPD are for the first time presented and compared to speed-of-sound US tomography. Results show the applicability of this marker for contrast specific US imaging, with cumulative phase delay imaging (CPDI) showing superior capabilities in detecting and localizing UCA, as compared to speed-of-sound US tomography. Cavities (filled with UCA) which were down to 1 mm in diameter were clearly detectable. Moreover, CPDI is free of the above mentioned nonlinear artifacts. These results open important possibilities to DCE-US tomography, with potential applications to breast imaging for cancer localization.

  8. A Flexible Annular-Array Imaging Platform for Micro-Ultrasound

    PubMed Central

    Qiu, Weibao; Yu, Yanyan; Chabok, Hamid Reza; Liu, Cheng; Tsang, Fu Keung; Zhou, Qifa; Shung, K. Kirk; Zheng, Hairong; Sun, Lei

    2013-01-01

    Micro-ultrasound is an invaluable imaging tool for many clinical and preclinical applications requiring high resolution (approximately several tens of micrometers). Imaging systems for micro-ultrasound, including single-element imaging systems and linear-array imaging systems, have been developed extensively in recent years. Single-element systems are cheaper, but linear-array systems give much better image quality at a higher expense. Annular-array-based systems provide a third alternative, striking a balance between image quality and expense. This paper presents the development of a novel programmable and real-time annular-array imaging platform for micro-ultrasound. It supports multi-channel dynamic beamforming techniques for large-depth-of-field imaging. The major image processing algorithms were achieved by a novel field-programmable gate array technology for high speed and flexibility. Real-time imaging was achieved by fast processing algorithms and high-speed data transfer interface. The platform utilizes a printed circuit board scheme incorporating state-of-the-art electronics for compactness and cost effectiveness. Extensive tests including hardware, algorithms, wire phantom, and tissue mimicking phantom measurements were conducted to demonstrate good performance of the platform. The calculated contrast-to-noise ratio (CNR) of the tissue phantom measurements were higher than 1.2 in the range of 3.8 to 8.7 mm imaging depth. The platform supported more than 25 images per second for real-time image acquisition. The depth-of-field had about 2.5-fold improvement compared to single-element transducer imaging. PMID:23287923

  9. A flexible annular-array imaging platform for micro-ultrasound.

    PubMed

    Qiu, Weibao; Yu, Yanyan; Chabok, Hamid Reza; Liu, Cheng; Tsang, Fu Keung; Zhou, Qifa; Shung, K Kirk; Zheng, Hairong; Sun, Lei

    2013-01-01

    Micro-ultrasound is an invaluable imaging tool for many clinical and preclinical applications requiring high resolution (approximately several tens of micrometers). Imaging systems for micro-ultrasound, including single-element imaging systems and linear-array imaging systems, have been developed extensively in recent years. Single-element systems are cheaper, but linear-array systems give much better image quality at a higher expense. Annular-array-based systems provide a third alternative, striking a balance between image quality and expense. This paper presents the development of a novel programmable and real-time annular-array imaging platform for micro-ultrasound. It supports multi-channel dynamic beamforming techniques for large-depth-of-field imaging. The major image processing algorithms were achieved by a novel field-programmable gate array technology for high speed and flexibility. Real-time imaging was achieved by fast processing algorithms and high-speed data transfer interface. The platform utilizes a printed circuit board scheme incorporating state-of-the-art electronics for compactness and cost effectiveness. Extensive tests including hardware, algorithms, wire phantom, and tissue mimicking phantom measurements were conducted to demonstrate good performance of the platform. The calculated contrast-to-noise ratio (CNR) of the tissue phantom measurements were higher than 1.2 in the range of 3.8 to 8.7 mm imaging depth. The platform supported more than 25 images per second for real-time image acquisition. The depth-of-field had about 2.5-fold improvement compared to single-element transducer imaging.

  10. Rigorous investigation of the array-tilt aberration for hexagonal, optical phased arrays.

    PubMed

    Hyde, Milo W; Wyman, Jason E; Tyler, Glenn A

    2014-04-10

    An investigation of the array-tilt aberration for hexagonal, optical phased arrays is presented. The investigation begins with theoretical derivations of the far-zone radiated field, the array factor, and the far-field radiated power for the seven-element hexagonal array with array tilt present. Physical insights gained from this analysis are discussed. An analytical treatment of correlation-based array-tilt estimators is also undertaken. Two novel array-tilt estimation techniques are developed from the analysis. The new techniques are shown to be significantly more efficient computationally than the traditional estimation approach. Simulation and experimental results are presented to validate the new array-tilt estimation methods.

  11. Glasses for 3D ultrasound computer tomography: phase compensation

    NASA Astrophysics Data System (ADS)

    Zapf, M.; Hopp, T.; Ruiter, N. V.

    2016-03-01

    Ultrasound Computer Tomography (USCT), developed at KIT, is a promising new imaging system for breast cancer diagnosis, and was successfully tested in a pilot study. The 3D USCT II prototype consists of several hundreds of ultrasound (US) transducers on a semi-ellipsoidal aperture. Spherical waves are sequentially emitted by individual transducers and received in parallel by many transducers. Reflectivity volumes are reconstructed by synthetic aperture focusing (SAFT). However, straight forward SAFT imaging leads to blurred images due to system imperfections. We present an extension of a previously proposed approach to enhance the images. This approach includes additional a priori information and system characteristics. Now spatial phase compensation was included. The approach was evaluated with a simulation and clinical data sets. An increase in the image quality was observed and quantitatively measured by SNR and other metrics.

  12. Microwave power transmitting phased array antenna research project

    NASA Technical Reports Server (NTRS)

    Dickinson, R. M.

    1978-01-01

    An initial design study and the development results of an S band RF power transmitting phased array antenna experiment system are presented. The array was to be designed, constructed and instrumented to permit wireless power transmission technology evaluation measurements. The planned measurements were to provide data relative to the achievable performance in the state of the art of flexible surface, retrodirective arrays, as a step in technically evaluating the satellite power system concept for importing to earth, via microwave beams, the nearly continuous solar power available in geosynchronous orbit. Details of the microwave power transmitting phased array design, instrumentation approaches, system block diagrams, and measured component and breadboard characteristics achieved are presented.

  13. 2D Ultrasound Sparse Arrays Multi-Depth Radiation Optimization Using Simulated Annealing and Spiral-Array Inspired Energy Functions.

    PubMed

    Roux, Emmanuel; Ramalli, Alessandro; Tortoli, Piero; Cachard, Christian; Robini, Marc; Liebgott, Herve

    2016-08-24

    Full matrix arrays are excellent tools for 3D ultrasound imaging, but the required number of active elements is too high to be individually controlled by an equal number of scanner channels. The number of active elements is significantly reduced by the sparse array techniques, but the position of the remaining elements must be carefully optimized. This issue is here faced by introducing novel energy functions in the simulated annealing algorithm. At each iteration step of the optimization process, one element is freely translated and the associated radiated pattern is simulated. To control the pressure field behavior at multiple depths, three energy functions inspired by the pressure field radiated by a Blackman-tapered spiral array are introduced. Such energy functions aim at limiting the main lobe width while lowering the side lobe and grating lobe levels at multiple depths. Numerical optimization results illustrate the influence of the number of iterations, pressure measurement points and depths as well as the influence of the energy function definition on the optimized layout. It is also shown that performance close to- or even better than the one provided by a spiral array, here assumed as reference, may be obtained. The finite-time convergence properties of simulated annealing allow the duration of the optimization process to be set in advance.

  14. 2-D Ultrasound Sparse Arrays Multidepth Radiation Optimization Using Simulated Annealing and Spiral-Array Inspired Energy Functions.

    PubMed

    Roux, Emmanuel; Ramalli, Alessandro; Tortoli, Piero; Cachard, Christian; Robini, Marc C; Liebgott, Herve

    2016-12-01

    Full matrix arrays are excellent tools for 3-D ultrasound imaging, but the required number of active elements is too high to be individually controlled by an equal number of scanner channels. The number of active elements is significantly reduced by the sparse array techniques, but the position of the remaining elements must be carefully optimized. This issue is faced here by introducing novel energy functions in the simulated annealing (SA) algorithm. At each iteration step of the optimization process, one element is freely translated and the associated radiated pattern is simulated. To control the pressure field behavior at multiple depths, three energy functions inspired by the pressure field radiated by a Blackman-tapered spiral array are introduced. Such energy functions aim at limiting the main lobe width while lowering the side lobe and grating lobe levels at multiple depths. Numerical optimization results illustrate the influence of the number of iterations, pressure measurement points, and depths, as well as the influence of the energy function definition on the optimized layout. It is also shown that performance close to or even better than the one provided by a spiral array, here assumed as reference, may be obtained. The finite-time convergence properties of SA allow the duration of the optimization process to be set in advance.

  15. Coherent optical monolithic phased-array antenna steering system

    DOEpatents

    Hietala, Vincent M.; Kravitz, Stanley H.; Vawter, Gregory A.

    1994-01-01

    An optical-based RF beam steering system for phased-array antennas comprising a photonic integrated circuit (PIC). The system is based on optical heterodyning employed to produce microwave phase shifting by a monolithic PIC constructed entirely of passive components. Microwave power and control signal distribution to the antenna is accomplished by optical fiber, permitting physical separation of the PIC and its control functions from the antenna. The system reduces size, weight, complexity, and cost of phased-array antenna systems.

  16. Signal detectability in diffusive media using phased arrays in conjunction with detector arrays.

    PubMed

    Kang, Dongyel; Kupinski, Matthew A

    2011-06-20

    We investigate Hotelling observer performance (i.e., signal detectability) of a phased array system for tasks of detecting small inhomogeneities and distinguishing adjacent abnormalities in uniform diffusive media. Unlike conventional phased array systems where a single detector is located on the interface between two sources, we consider a detector array, such as a CCD, on a phantom exit surface for calculating the Hotelling observer detectability. The signal detectability for adjacent small abnormalities (2 mm displacement) for the CCD-based phased array is related to the resolution of reconstructed images. Simulations show that acquiring high-dimensional data from a detector array in a phased array system dramatically improves the detectability for both tasks when compared to conventional single detector measurements, especially at low modulation frequencies. It is also observed in all studied cases that there exists the modulation frequency optimizing CCD-based phased array systems, where detectability for both tasks is consistently high. These results imply that the CCD-based phased array has the potential to achieve high resolution and signal detectability in tomographic diffusive imaging while operating at a very low modulation frequency. The effect of other configuration parameters, such as a detector pixel size, on the observer performance is also discussed.

  17. Real-time Implementation of a Dual-Mode Ultrasound Array System: In Vivo Results

    PubMed Central

    Casper, Andrew J.; Liu, Dalong; Ballard, John R.; Ebbini, Emad S.

    2013-01-01

    A real-time dual-mode ultrasound array (DMUA) system for imaging and therapy is described. The system utilizes a concave (40-mm radius of curvature) 3.5 MHz, 32 element array and modular multi-channel transmitter/receiver. It is capable of operating in a variety of imaging and therapy modes (on transmit) and continuous receive on all array elements even during high-power operation. A signal chain consisting of field-programmable gate arrays (FPGA) and graphical processing units (GPU) is used to enable real-time, software-defined beamforming and image formation. Imaging data, from quality assurance phantoms as well as in vivo small and large animal models, are presented and discussed. Corresponding images obtained using a temporally-synchronized and spatially-aligned diagnostic probe confirm the DMUA’s ability to form anatomically-correct images with sufficient contrast in an extended field of view (FOV) around its geometric center. In addition, high frame rate DMUA data also demonstrate the feasibility of detection and localization of echo changes indicative of cavitation and/or tissue boiling during HIFU exposures with 45 – 50 dB dynamic range. The results also show that the axial and lateral resolution of the DMUA are consistent with its fnumber and bandwidth with well behaved speckle cell characteristics. These results point the way to a theranostic DMUA system capable of quantitative imaging of tissue property changes with high specificity to lesion formation using focused ultrasound. PMID:23708766

  18. Phased-array sources based on nonlinear metamaterial nanocavities

    SciTech Connect

    Wolf, Omri; Campione, Salvatore; Benz, Alexander; Ravikumar, Arvind P.; Liu, Sheng; Luk, Ting S.; Kadlec, Emil Andrew; Shaner, Eric A.; Klem, John Frederick; Sinclair, Michael B.; Brener, Igal

    2015-07-01

    Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization. As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (~5 μm): a beam splitter and a polarizing beam splitter. As a result, proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum.

  19. Phased-array sources based on nonlinear metamaterial nanocavities.

    PubMed

    Wolf, Omri; Campione, Salvatore; Benz, Alexander; Ravikumar, Arvind P; Liu, Sheng; Luk, Ting S; Kadlec, Emil A; Shaner, Eric A; Klem, John F; Sinclair, Michael B; Brener, Igal

    2015-07-01

    Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization. As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (∼5 μm): a beam splitter and a polarizing beam splitter. Proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum.

  20. Phased array ultrasonic inspection of Friction Stir Weldments

    NASA Astrophysics Data System (ADS)

    Lamarre, André; Moles, Michael; Lupien, Vincent

    2000-05-01

    Phased array ultrasonic inspection methods have been developed for the rapid inspection of Friction Stir Weldments (FSW) on Delta rocket cryogenic tanks. A comprehensive review was performed to identify NDE methods that are suitable for the detection of defects in this new welding process. The search included a review of traditional and advanced NDE methods that were capable of demonstrating both the sensitivity and inspection rates required for this examination. This paper will discuss the theory behind phased array techniques, fundamentals of several probe designs for FSW configurations, and the advantages of using phased arrays over conventional NDE methods for this applications.

  1. Diffraction-Coupled, Phase-Locked Semiconductor Laser Array

    NASA Technical Reports Server (NTRS)

    Katz, Joseph; Yariv, Amnon; Margalit, Shlomo

    1988-01-01

    Stable, narrow far field produced. Array of lasers fabricated on single chip. Individual laser waveguides isolated from each other except in end portions, where diffraction coupling takes place. Radiation pattern far from laser array has single, sharp central lobe when all lasers operate in phase with each other. Shape of lobe does not vary appreciably with array current. Applications include recording, printing, and range finding.

  2. Nonlinear ultrasonic phased array imaging of closed cracks using global preheating and local cooling

    NASA Astrophysics Data System (ADS)

    Ohara, Yoshikazu; Takahashi, Koji; Ino, Yoshihiro; Yamanaka, Kazushi

    2015-10-01

    Closed cracks are the main cause of underestimation in ultrasonic inspection, because the ultrasound transmits through the crack. Specifically, the measurement of closed-crack depth in coarse-grained materials, which are highly attenuative due to linear scatterings at the grains, is the most difficult issue. To solve this problem, we have developed a temporary crack opening method, global preheating and local cooling (GPLC), using tensile thermal stress, and a high-selectivity imaging method, load difference phased array (LDPA), based on the subtraction of phased array images between different stresses. To demonstrate our developed method, we formed a closed fatigue crack in coarse-grained stainless steel (SUS316L) specimen. As a result of applying it to the specimen, the high-selectivity imaging performance was successfully demonstrated. This will be useful in improving the measurement accuracy of closed-crack depths in coarse-grained material.

  3. Frequency translating phase conjugation circuit for active retrodirective antenna array

    NASA Astrophysics Data System (ADS)

    Chernoff, R.

    1980-11-01

    An active retrodirective antenna array which has central phasing from a reference antenna element through a "tree" structured network of transmission lines utilizes a number of phase conjugate circuits (PCCs) at each node and a phase reference regeneration circuit (PRR) at each node except the initial node. Each node virtually coincides with an element of the array. A PCC generates the exact conjugate phase of an incident signal using a phase locked loop which combines the phases in an up converter, divides the sum by 2 and mixes the result with the phase in a down converter for phase detection. The PRR extracts the phase from the conjugate phase. Both the PCC and the PRR are not only exact but also free from mixer degeneracy.

  4. Ultrasound

    MedlinePlus

    Ultrasound is a type of imaging. It uses high-frequency sound waves to look at organs and ... liver, and other organs. During pregnancy, doctors use ultrasound to view the fetus. Unlike x-rays, ultrasound ...

  5. Ultrasound assisted three phase partitioning of a fibrinolytic enzyme.

    PubMed

    Avhad, Devchand N; Niphadkar, Sonali S; Rathod, Virendra K

    2014-03-01

    The present investigation is aimed at ultrasound assisted three phase partitioning (UATPP) of a fibrinolytic enzyme from Bacillus sphaericus MTCC 3672. Three phase partitioning integrates the concentration and partial purification step of downstream processing of a biomolecule. Three phase system is formed with simultaneous addition of ammonium sulfate to crude broth and followed by t-butanol. UATPP of a fibrinolytic enzyme was studied by varying different process parameters such as ammonium sulfate saturation concentration, pH, broth to t-butanol ratio, temperature, ultrasound frequency, ultrasonication power, and duty cycle. The optimized parameters yielding maximum purity of 16.15-fold of fibrinolytic enzyme with 65% recovery comprised of 80% ammonium sulfate saturation, pH 9, temperature 30 °C, broth to t-butanol ratio 0.5 (v/v), at 25 kHz frequency and 150 W ultrasonication power with 40% duty cycle for 5 min irradiation time. SDS PAGE analysis of partitioned enzyme shows partial purification with a molecular weight in the range of 55-70 kDa. Enhanced mass transfer of UATPP resulted in higher fold purity of fibrinolytic enzyme with reduced time of operation from 1 h to 5 min as compared to conventional TPP. Outcome of our findings highlighted the use of UATPP as an efficient biosepartion technique. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Towards the volumetricardiogram: volume determination of cardiac chambers using 3D matrix-array ultrasound

    NASA Astrophysics Data System (ADS)

    Stetten, George D.; Caines, Michael; Ohazama, Chikai J.; von Ramm, Olaf T.

    1995-05-01

    Matrix-array ultrasound is a new medical imaging modality that steers an ultrasound beam electronically in three dimensions. It is the first imaging modality that can view the heart in 3D in real time, making possible the `volumetricardiogram,' i.e., continuous beat to beat measurement of cardiac chamber volume. To create a fully automatic real-time volumetricardiogram, we have developed the flow integration transform (FIT), which operates on 2D images produced by slicing through the 3D ultrasound data. Although lacking rotational or scale invariance, the FIT is designed to operate eventually in dedicated hardware at very high speed, permitting the application of a large battery of test shapes within the period of a single ultrasound frame (approximately 45 milliseconds). To test the FIT, we have volumetrically scanned a series of 21 fluid-filled balloons. We used the FIT to detect circular cross-sections of the balloons by applying a battery of circles over a range of radii. The detected circles were used to compute volumes, which were then compared to volumes determined independently by weight. Our results are encouraging towards further development of this completely automated method of volume determination.

  7. Phased array-fed antenna configuration study: Technology assessment

    NASA Technical Reports Server (NTRS)

    Croswell, W. F.; Ball, D. E.; Taylor, R. C.

    1983-01-01

    Spacecraft array fed reflector antenna systems were assessed for particular application to a multiple fixed spot beam/multiple scanning spot beam system. Reflector optics systems are reviewed in addition to an investigation of the feasibility of the use of monolithic microwave integrated circuit power amplifiers and phase shifters in each element of the array feed.

  8. Testing the Atacama Compact Array Phase-Correction Scheme Using the Submillimeter Array

    NASA Astrophysics Data System (ADS)

    Matsushita, Satoki; Chen, Yu-Lin

    2010-08-01

    We conducted observational tests of a phase-correction scheme for the Atacama Compact Array (ACA) of the Atacama Large Millimeter and submillimeter Array (ALMA) using the Submillimeter Array (SMA) on Mauna Kea in Hawaii. Interferometers at millimeter and submillimeter waves are highly affected by refraction induced by water vapor in the troposphere, which results in phase fluctuations. The ACA is planning to compensate for the atmospheric phase fluctuation using phase information of the outermost antennas with interpolating into the inner antennas by creating a phase screen. The interpolation and extrapolation phase-correction schemes using phase screens have been tested by the SMA to study how effective they are. We produce a plane of wavefront (phase screen) from the phase information of three antennas for each integration, and this phase screen is used for interpolating the phase of the inner antenna and extrapolating that of the outer one. The interpolation scheme apparently obtains improved results, suggesting that the ACA phase-correction scheme works well. On the other hand, the extrapolation one often does not improve the results. After extrapolation, unexpectedly large phase fluctuations occur in the phases of the antennas at a distance of ˜140 m away from the center of the three reference antennas. The directions of these antennas are almost perpendicular to that of the wind, suggesting that the phase fluctuations can be well explained by the frozen phase screen in the atmosphere.

  9. Laser-scanning photoacoustic microscopy with ultrasonic phased array transducer.

    PubMed

    Zheng, Fan; Zhang, Xiangyang; Chiu, Chi Tat; Zhou, Bill L; Shung, K Kirk; Zhang, Hao F; Jiao, Shuliang

    2012-11-01

    In this paper, we report our latest progress on proving the concept that ultrasonic phased array can improve the detection sensitivity and field of view (FOV) in laser-scanning photoacoustic microscopy (LS-PAM). A LS-PAM system with a one-dimensional (1D) ultrasonic phased array was built for the experiments. The 1D phased array transducer consists of 64 active elements with an overall active dimension of 3.2 mm × 2 mm. The system was tested on imaging phantom and mouse ear in vivo. Experiments showed a 15 dB increase of the signal-to-noise ratio (SNR) when beamforming was employed compared to the images acquired with each single element. The experimental results demonstrated that ultrasonic phased array can be a better candidate for LS-PAM in high sensitivity applications like ophthalmic imaging.

  10. Laser-scanning photoacoustic microscopy with ultrasonic phased array transducer

    PubMed Central

    Zheng, Fan; Zhang, Xiangyang; Chiu, Chi Tat; Zhou, Bill L.; Shung, K. Kirk; Zhang, Hao F.; Jiao, Shuliang

    2012-01-01

    In this paper, we report our latest progress on proving the concept that ultrasonic phased array can improve the detection sensitivity and field of view (FOV) in laser-scanning photoacoustic microscopy (LS-PAM). A LS-PAM system with a one-dimensional (1D) ultrasonic phased array was built for the experiments. The 1D phased array transducer consists of 64 active elements with an overall active dimension of 3.2 mm × 2 mm. The system was tested on imaging phantom and mouse ear in vivo. Experiments showed a 15 dB increase of the signal-to-noise ratio (SNR) when beamforming was employed compared to the images acquired with each single element. The experimental results demonstrated that ultrasonic phased array can be a better candidate for LS-PAM in high sensitivity applications like ophthalmic imaging. PMID:23162708

  11. Fabrication and performance of a miniaturized 64-element high-frequency endoscopic phased array.

    PubMed

    Bezanson, Andre; Adamson, Rob; Brown, Jeremy

    2014-01-01

    We have developed a 40-MHz, 64-element phased-array transducer packaged in a 2.5 x 3.1 mm endoscopic form factor. The array is a forward-looking semi-kerfed design based on a 0.68Pb(Mg(1/3)Nb(2/3))O(3) - 0.32PbTiO3 (PMN-32%PT) single-crystal wafer with an element-to-element pitch of 38 µm. To achieve a miniaturized form factor, a novel technique of wire bonding the array elements to a polyimide flexible circuit board oriented parallel to the forward looking ultrasound beam and perpendicular to the array was developed. A technique of partially dicing into the back of the array was also implemented to improve the directivity of the array elements. The array was fabricated with a single-layer P(VDF-TrFE)-copolymer matching layer and a polymethylpentene (TPX) lens for passive elevation focusing to a depth of 7 mm. The two-way -6-dB pulse bandwidth was measured to be 55% and the average electromechanical coupling (k(eff)) for the individual elements was measured to be 0.62. The one-way -6-dB directivities from several array elements were measured to be ±20°, which was shown to be an improvement over an identical kerfless array. The -3-dB elevation focus resulting from the TPX lens was measured to be 152 µm at the focal depth, and the focused lateral resolution was measured to be 80 µm at a steering angle of 0°. To generate beam profiles and images, the probe was connected to a commercial ultrasound imaging platform which was reprogrammed to allow for phased array transmit beamforming and receive data collection. The collected RF data were then processed offline using a numerical computing script to generate sector images. The radiation pattern for the beamformed transmit pulse was collected along with images of wire phantoms in water and tissue-equivalent medium with a dynamic range of 60 dB. Finally, ex vivo tissue images were generated of porcine brain tissue.

  12. An Evaluation of Signal Processing Tools for Improving Phased Array Ultrasonic Weld Inspection

    SciTech Connect

    Ramuhalli, Pradeep; Cinson, Anthony D.; Crawford, Susan L.; Harris, Robert V.; Diaz, Aaron A.; Anderson, Michael T.

    2011-03-24

    Cast austenitic stainless steel (CASS) commonly used in U.S. nuclear power plants is a coarse-grained, elastically anisotropic material. The coarse-grained nature of CASS makes ultrasonic inspection of in-service components difficult. Recently, low-frequency phased array ultrasound has emerged as a candidate for the CASS piping weld inspection. However, issues such as low signal-to-noise ratio and difficulty in discriminating between flaw and non-flaw signals remain. This paper discusses the evaluation of a number of signal processing algorithms for improving flaw detection in CASS materials. The full paper provides details of the algorithms being evaluated, along with preliminary results.

  13. High-throughput fiber-array transvaginal ultrasound/photoacoustic probe for ovarian cancer imaging

    NASA Astrophysics Data System (ADS)

    Salehi, Hassan S.; Kumavor, Patrick D.; Alqasemi, Umar; Li, Hai; Wang, Tianheng; Zhu, Quing

    2014-03-01

    A high-throughput ultrasound/photoacoustic probe for delivering high contrast and signal-to-noise ratio images was designed, constructed, and tested. The probe consists of a transvaginal ultrasound array integrated with four 1mm-core optical fibers and a sheath. The sheath encases transducer and is lined with highly reflecting aluminum for high intensity light output and uniformity while at the same time remaining below the maximum permissible exposure (MPE) recommended by the American National Standards Institute (ANSI). The probe design was optimized by simulating the light fluence distribution in Zemax. The performance of the probe was evaluated by experimental measurements of the fluence and real-time imaging of polyethylene-tubing filled with blood. These results suggest that our probe has great potential for in vivo imaging and characterization of ovarian cancer.

  14. 2D array transducers for real-time 3D ultrasound guidance of interventional devices

    NASA Astrophysics Data System (ADS)

    Light, Edward D.; Smith, Stephen W.

    2009-02-01

    We describe catheter ring arrays for real-time 3D ultrasound guidance of devices such as vascular grafts, heart valves and vena cava filters. We have constructed several prototypes operating at 5 MHz and consisting of 54 elements using the W.L. Gore & Associates, Inc. micro-miniature ribbon cables. We have recently constructed a new transducer using a braided wiring technology from Precision Interconnect. This transducer consists of 54 elements at 4.8 MHz with pitch of 0.20 mm and typical -6 dB bandwidth of 22%. In all cases, the transducer and wiring assembly were integrated with an 11 French catheter of a Cook Medical deployment device for vena cava filters. Preliminary in vivo and in vitro testing is ongoing including simultaneous 3D ultrasound and x-ray fluoroscopy.

  15. Non-invasive tissue parameter estimation with dual-mode ultrasound arrays

    NASA Astrophysics Data System (ADS)

    Haritonova, Alyona; Wilken-Resman, Elias; Liu, Dalong; Ebbini, Emad

    2017-03-01

    Objective of this study was to noninvasively extract quantitative estimates of heart tissue absorption before and after lesion formation. To extract tissue absorption, ultrasound temperature maps were reconstructed from single transmit focus (STF) images acquired with a 3.5MHz Dual-Mode Ultrasound Array (DMUA). Initial heating rate is estimated before and after therapeutic lesion formation through a delivery of a subtherapeutic intensity shot in ex vivo bovine heart tissue. Changes in heating rate are documented for a subset of five subtherapeutic shot intensities. Additionally, repeatability is demonstrated for before and after measurement of the initial heating rate. Careful gross examination of tissue was performed for every location where an absorption measurement was made.

  16. MSAT mobile electronically steered phased array antenna development

    NASA Technical Reports Server (NTRS)

    Schmidt, Fred

    1988-01-01

    The Mobile Satellite Experiment (MSAT-X) breadboard antenna design demonstrates the feasibility of using a phased array in a mobile satellite application. An electronically steerable phased array capable of tracking geosynchronous satellites from anywhere in the Continental United States has been developed. The design is reviewed along with the test data. Cost analysis are presented which indicate that this design can be produced at a cost of $1620 per antenna.

  17. Designing of Phased Array Transducers for Industrial Applications

    NASA Astrophysics Data System (ADS)

    Dumas, Ph.; Poguet, J.; Fleury, G.

    2004-02-01

    By increasing inspection speed, and deflection capabilities of the transducers, Phased-array technology has proved its interest to face new ∂ NDT challenges, and is becoming more and more popular in the main industrial fields of activities. This paper describes the main effects of specifications on transducer performances, and explains how to defined them. The second part speaks about the manufacturing step, showing the influence of component choice on performances. Several Phased-array applications examples illustrating these considerations will be presented.

  18. Genetic Algorithms as a Tool for Phased Array Radar Design

    DTIC Science & Technology

    2002-06-01

    NAVAL POSTGRADUATE SCHOOL Monterey, California THESIS Approved for public release; distribution is unlimited. GENETIC ALGORITHMS AS A...REPORT DATE June 2002 3. REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE: Genetic Algorithms as a Tool for Phased Array Radar...creative ways to design multi-function phased array radars. This thesis proposes that Genetic Algorithms, computer programs that mimic natural selection

  19. A 32-GHz phased array transmit feed for spacecraft telecommunications

    NASA Technical Reports Server (NTRS)

    Lee, K. A.; Rascoe, D. L.; Crist, R. A.; Huang, J.; Wamhof, P. D.; Lansing, F. S.

    1992-01-01

    A 21-element phased array transmit feed was demonstrated as part of an effort to develop and evaluate state-of-the-art transmitter and receiver components at 32 and 34 GHz for future deep-space missions. Antenna pattern measurements demonstrating electronic beam steering of the two-dimensional array are reported and compared with predictions based on measured performance of MMIC-based phase shifter and amplifier modules and Vivaldi slotline radiating elements.

  20. Piezoelectric Micromachined Ultrasound Transducer (PMUT) Arrays for Integrated Sensing, Actuation and Imaging

    PubMed Central

    Qiu, Yongqiang; Gigliotti, James V.; Wallace, Margeaux; Griggio, Flavio; Demore, Christine E. M.; Cochran, Sandy; Trolier-McKinstry, Susan

    2015-01-01

    Many applications of ultrasound for sensing, actuation and imaging require miniaturized and low power transducers and transducer arrays integrated with electronic systems. Piezoelectric micromachined ultrasound transducers (PMUTs), diaphragm-like thin film flexural transducers typically formed on silicon substrates, are a potential solution for integrated transducer arrays. This paper presents an overview of the current development status of PMUTs and a discussion of their suitability for miniaturized and integrated devices. The thin film piezoelectric materials required to functionalize these devices are discussed, followed by the microfabrication techniques used to create PMUT elements and the constraints the fabrication imposes on device design. Approaches for electrical interconnection and integration with on-chip electronics are discussed. Electrical and acoustic measurements from fabricated PMUT arrays with up to 320 diaphragm elements are presented. The PMUTs are shown to be broadband devices with an operating frequency which is tunable by tailoring the lateral dimensions of the flexural membrane or the thicknesses of the constituent layers. Finally, the outlook for future development of PMUT technology and the potential applications made feasible by integrated PMUT devices are discussed. PMID:25855038

  1. Coherent Optical Processing of Phased Array Radar Data

    NASA Technical Reports Server (NTRS)

    Rogers, J. W.

    1972-01-01

    Interfacing a coherent optical processor, which utilizes an electron-beam addressed, potassium dideuterium phosphate (KDP) crystal modulator, with a linear phased array is studied. An abbreviated development of typical radar signals from a linear array is included. A plan for formating the spatial modulator with linear array signals is presented. The theoretical expectations which include target angle and Doppler are derived. A simulated set of M signals which are typical of a linear array of M elements was devised. This set of signals was used to modulate the wave front of collimated laser light via the KDP crystal according to the format presented.

  2. Jet Noise Source Localization Using Linear Phased Array

    NASA Technical Reports Server (NTRS)

    Agboola, Ferni A.; Bridges, James

    2004-01-01

    A study was conducted to further clarify the interpretation and application of linear phased array microphone results, for localizing aeroacoustics sources in aircraft exhaust jet. Two model engine nozzles were tested at varying power cycles with the array setup parallel to the jet axis. The array position was varied as well to determine best location for the array. The results showed that it is possible to resolve jet noise sources with bypass and other components separation. The results also showed that a focused near field image provides more realistic noise source localization at low to mid frequencies.

  3. Ultrasound of the coracoclavicular ligaments in the acute phase of an acromioclavicular disjonction: Comparison of radiographic, ultrasound and MRI findings.

    PubMed

    Faruch Bilfeld, Marie; Lapègue, Franck; Chiavassa Gandois, Hélène; Bayol, Marie Aurélie; Bonnevialle, Nicolas; Sans, Nicolas

    2017-02-01

    Acromioclavicular joint injuries are typically diagnosed by clinical and radiographic assessment with the Rockwood classification, which is crucial for treatment planning. The purpose of this study was to describe how the ultrasound findings of acromioclavicular joint injury compare with radiography and MRI findings. Forty-seven patients with suspected unilateral acromioclavicular joint injury after acute trauma were enrolled in this prospective study. All patients underwent digital radiography, ultrasound and 3T MRI. A modified Rockwood classification was used to evaluate the coracoclavicular ligaments. The classifications of acromioclavicular joint injuries diagnosed with radiography, ultrasound and MRI were compared. MRI was used as the gold standard. The agreement between the ultrasound and MRI findings was very good, with a correlation coefficient of 0.83 (95 % CI: 0.72-0.90; p < 0.0001). Ultrasound detected coracoclavicular ligament injuries with a sensitivity of 88.9 %, specificity of 90.0 %, positive predictive value of 92.3 % and negative predictive value of 85.7 %. The agreement between the ultrasound and radiography findings was poor, with a correlation coefficient of 0.69 (95 % CI: 0.51-0.82; p < 0.0001). Ultrasound is an effective examination for the diagnostic work-up of lesions of the coracoclavicular ligaments in the acute phase of an acromioclavicular injury. • Ultrasound is appropriate for acute acromioclavicular trauma due to its accessibility. • Ultrasound contributes to the diagnostic work-up of acute lesions of the coracoclavicular ligaments. • Ultrasound is appropriate in patients likely to benefit from surgical treatment. • Ultrasound could be a supplement to standard radiography in acute acromioclavicular trauma.

  4. Large Phased Array Radar Using Networked Small Parabolic Reflectors

    NASA Technical Reports Server (NTRS)

    Amoozegar, Farid

    2006-01-01

    Multifunction phased array systems with radar, telecom, and imaging applications have already been established for flat plate phased arrays of dipoles, or waveguides. In this paper the design trades and candidate options for combining the radar and telecom functions of the Deep Space Network (DSN) into a single large transmit array of small parabolic reflectors will be discussed. In particular the effect of combing the radar and telecom functions on the sizes of individual antenna apertures and the corresponding spacing between the antenna elements of the array will be analyzed. A heterogeneous architecture for the DSN large transmit array is proposed to meet the radar and telecom requirements while considering the budget, scheduling, and strategic planning constrains.

  5. Large Phased Array Radar Using Networked Small Parabolic Reflectors

    NASA Technical Reports Server (NTRS)

    Amoozegar, Farid

    2006-01-01

    Multifunction phased array systems with radar, telecom, and imaging applications have already been established for flat plate phased arrays of dipoles, or waveguides. In this paper the design trades and candidate options for combining the radar and telecom functions of the Deep Space Network (DSN) into a single large transmit array of small parabolic reflectors will be discussed. In particular the effect of combing the radar and telecom functions on the sizes of individual antenna apertures and the corresponding spacing between the antenna elements of the array will be analyzed. A heterogeneous architecture for the DSN large transmit array is proposed to meet the radar and telecom requirements while considering the budget, scheduling, and strategic planning constrains.

  6. An optically controlled Ka-band phased array antenna

    NASA Astrophysics Data System (ADS)

    Kunath, R. R.; Lee, Richard Q.; Martzaklis, K. S.; Shalkhauser, K. A.; Downey, Alan N.; Simons, Rainee N.

    1992-08-01

    The design and development of a small, optically controlled phased array antenna suitable for communication satellite applications are discussed. A vertical integration architecture is used which minimizes the size of the array with its associated beamforming network (BFN). The antenna features a four-element linear microstrip array that uses aperture coupling of the antenna elements to the BFN; a modified Wilkinson power divider BFN; and 32 GHz, four-bit monolithic microwave integrated circuit (MMIC) phase shifters in customized quartz packages with corresponding optoelectronic interface circuits (OEIC's) for control signal reception.

  7. An optically controlled Ka-band phased array antenna

    NASA Technical Reports Server (NTRS)

    Kunath, R. R.; Lee, Richard Q.; Martzaklis, K. S.; Shalkhauser, K. A.; Downey, Alan N.; Simons, Rainee N.

    1992-01-01

    The design and development of a small, optically controlled phased array antenna suitable for communication satellite applications are discussed. A vertical integration architecture is used which minimizes the size of the array with its associated beamforming network (BFN). The antenna features a four-element linear microstrip array that uses aperture coupling of the antenna elements to the BFN; a modified Wilkinson power divider BFN; and 32 GHz, four-bit monolithic microwave integrated circuit (MMIC) phase shifters in customized quartz packages with corresponding optoelectronic interface circuits (OEIC's) for control signal reception.

  8. A vertically integrated Ka-band phased array antenna

    NASA Technical Reports Server (NTRS)

    Kunath, R. R.; Lee, R. Q.; Martzaklis, K. S.; Shalkhauser, K. A.; Downey, A. N.; Simons, R.

    1992-01-01

    The design, development, and experimental demonstration of a small phased array antenna suitable for applications on communications satellites are discussed. Each of the vertical layers was optimized for performance, and MMICs on custom carriers were characterized prior to insertion. A vertical integration architecture is used which minimizes the size of the array with its associated beamforming network (BFN). The antenna features a four-element linear microstrip array that uses aperture coupling of the antenna elements to the BFN; a modified Wilkinson power divider BFN; and 32 Ghz, 4-bit MMIC phase shifters on customized alumina carriers. Performance data are presented for all components, and far-field antenna radiation patterns are given.

  9. Optical beam forming techniques for phased array antennas

    NASA Technical Reports Server (NTRS)

    Wu, Te-Kao; Chandler, Charles W.

    1993-01-01

    Three optical beam forming techniques are identified as applicable to large spaceborne phased array antennas. They are 1) the fiber replacement of conventional RF phased array distribution and control components, 2) spatial beam forming, and 3) optical beam splitting techniques. Two novel optical beam forming approaches, i.e., the spatial beam forming with a 'smart pixel' spatial light modulator (SLM) and the optical beam splitting approaches are conceived with integrated quasi-optical components. Also presented are the transmit and receive array architectures with the new SLM.

  10. PMN-PT single crystal for endoscopic ultrasound 2D array application

    NASA Astrophysics Data System (ADS)

    Zhu, Yuhang; Liang, Huageng; Zhu, Benpeng; Zhou, Dan; Yang, Xiaofei

    2017-03-01

    Based on lead magnesium niobate-lead titanate single crystal, a 24 × 24 row-column addressing endoscopic two-dimensional array has been successfully fabricated using novel flanged electrodes and "semi-kerf" technologies. Each row/column array element was measured to have an electromechanical coupling coefficient of 0.81, a center frequency of 5MHz, and a fractional bandwidth of approximately 88% at -6 dB. Of particular significance was that the lead magnesium niobate-lead titanate element exhibits much higher sensitivity compared with lead zirconate titanate-based 2D arrays with similar operational frequency and element area. According to the Field II simulated results, although the obtained beamwidth at -6 dB was a little inferior to that of the fully sampled 24 × 24 two-dimensional array, it is believed that the beamwidth can be improved by appropriately increasing the element number. These results demonstrated that the lead magnesium niobate-lead titanate single-crystal 2D array is a promising candidate for real-time three-dimensional endoscopic ultrasound imaging.

  11. Ka-Band Multibeam Aperture Phased Array Being Developed

    NASA Technical Reports Server (NTRS)

    Reinhart, Richard C.; Kacpura, Thomas J.

    2004-01-01

    Phased-array antenna systems offer many advantages to low-Earth-orbiting satellite systems. Their large scan angles and multibeam capabilities allow for vibration-free, rapid beam scanning and graceful degradation operation for high rate downlink of data to users on the ground. Technology advancements continue to reduce the power, weight, and cost of these systems to make phased arrays a competitive alternative in comparison to the gimbled reflector system commonly used in science missions. One effort to reduce the cost of phased arrays is the development of a Ka-band multibeam aperture (MBA) phased array by Boeing Corporation under a contract jointly by the NASA Glenn Research Center and the Office of Naval Research. The objective is to develop and demonstrate a space-qualifiable dual-beam Ka-band (26.5-GHz) phased-array antenna. The goals are to advance the state of the art in Ka-band active phased-array antennas and to develop and demonstrate multibeam transmission technology compatible with spacecraft in low Earth orbit to reduce the cost of future missions by retiring certain development risks. The frequency chosen is suitable for space-to-space and space-to-ground communication links. The phased-array antenna has a radiation pattern designed by combining a set of individual radiating elements, optimized with the type of radiating elements used, their positions in space, and the amplitude and phase of the currents feeding the elements. This arrangement produces a directional radiation pattern that is proportional to the number of individual radiating elements. The arrays of interest here can scan the main beam electronically with a computerized algorithm. The antenna is constructed using electronic components with no mechanical parts, and the steering is performed electronically, without any resulting vibration. The speed of the scanning is limited primarily by the control electronics. The radiation performance degrades gracefully if a portion of the elements

  12. Optical phased arrays with evanescently-coupled antennas

    DOEpatents

    Sun, Jie; Watts, Michael R; Yaacobi, Ami; Timurdogan, Erman

    2015-03-24

    An optical phased array formed of a large number of nanophotonic antenna elements can be used to project complex images into the far field. These nanophotonic phased arrays, including the nanophotonic antenna elements and waveguides, can be formed on a single chip of silicon using complementary metal-oxide-semiconductor (CMOS) processes. Directional couplers evanescently couple light from the waveguides to the nanophotonic antenna elements, which emit the light as beams with phases and amplitudes selected so that the emitted beams interfere in the far field to produce the desired pattern. In some cases, each antenna in the phased array may be optically coupled to a corresponding variable delay line, such as a thermo-optically tuned waveguide or a liquid-filled cell, which can be used to vary the phase of the antenna's output (and the resulting far-field interference pattern).

  13. Fiber optic signal distribution for phased array antennas

    NASA Astrophysics Data System (ADS)

    Mecherle, G. S.

    1992-03-01

    The use of a 32-GHz phased-array transmitting antenna with fiberoptic signal distribution is considered in the context of a Mars relay satellite for NASA's Space Exploration Initiative. The specifications of the proposed application are assessed with specific attention given to the EIRP requirement of 86 dBW and its ramifications on the phased array, antenna, and photonic architecture. A photonic performance analysis is conducted to study phase-noise and SNR degradations to determine whether phase-locked loop (PLL) complexity is required. SNR and phase noise are examined as a function of the number of optical splits, and the number is shown to be limited to 350. Use of the PLL allows one laser to support 650 elements - as opposed to 250 - showing that only a single laser diode is needed to support the array for the Mars transmitter.

  14. A novel, flat, electronically-steered phased array transducer for tissue ablation: preliminary results

    NASA Astrophysics Data System (ADS)

    Ellens, Nicholas P. K.; Lucht, Benjamin B. C.; Gunaseelan, Samuel T.; Hudson, John M.; Hynynen, Kullervo H.

    2015-03-01

    Flat, λ/2-spaced phased arrays for therapeutic ultrasound were examined in silico and in vitro. All arrays were made by combining modules made of 64 square elements with 1.5 mm inter-element spacing along both major axes. The arrays were designed to accommodate integrated, co-aligned diagnostic transducers for targeting and monitoring. Six arrays of 1024 elements (16 modules) and four arrays of 6144 elements (96 modules) were modelled and compared according to metrics such as peak pressure amplitude, focal size, ability to be electronically-steered far off-axis and grating lobe amplitude. Two 1024 element prototypes were built and measured in vitro, producing over 100 W of acoustic power. In both cases, the simulation model of the pressure amplitude field was in good agreement with values measured by hydrophone. Using one of the arrays, it was shown that the peak pressure amplitude dropped by only 24% and 25% of the on-axis peak pressure amplitude when steered to the edge of the array (40 mm) at depths of 30 mm and 50 mm. For the 6144 element arrays studied in in silico only, similarly high steerability was found: even when steered 100 mm off-axis, the pressure amplitude decrease at the focus was less than 20%, while the maximum pressure grating lobe was only 20%. Thermal simulations indicate that the modules produce more than enough acoustic power to perform rapid ablations at physiologically relevant depths and steering angles. Arrays such as proposed and tested in this study have enormous potential: their high electronic steerability suggests that they will be able to perform ablations of large volumes without the need for any mechanical translation.

  15. Coplanar waveguide feeds for phased array antennas

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Lee, Richard Q.

    1992-01-01

    The design and performance of the following coplanar waveguide (CPW) microwave distribution networks for linear as well as circularly polarized microstrip patches and printed dipole arrays is presented: (1) CPW/microstrip line feed; (2) CPW/balanced stripline feed; (3) CPW/slotline feed; (4) grounded CPW (GCPW)/balanced coplanar stripline feed; and (5) CPW/slot coupled feed. Typical measured radiation patterns are presented, and their relative advantages and disadvantages are compared.

  16. Coplanar waveguide feeds for phased array antennas

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Lee, Richard Q.

    1991-01-01

    The design and performance is presented of the following Coplanar Waveguides (CPW) microwave distribution networks for linear as well as circularly polarized microstrip patches and dipole arrays: (1) CPW/Microstrip Line feed; (2) CPW/Balanced Stripline feed; (3) CPW/Slotline feed; (4) Grounded CPW/Balanced coplanar stripline feed; and (5) CPW/Slot coupled feed. Typical measured radiation patterns are presented, and their relative advantages and disadvantages are compared.

  17. Coplanar waveguide feeds for phased array antennas

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Lee, Richard Q.

    1991-01-01

    The design and performance is presented of the following coplanar waveguides (CPW) microwave distribution networks for linear as well as circularly polarized microstrip patches and dipole arrays: (1) CPW/microstrip line feed; (2) CPW/balanced stripline feed; (3) CPW/slotline feed; (4) grounded CPW/balanced coplanar stripline feed; and (5) CPW/slot coupled feed. Typical measured radiation patterns are presented, and their relative advantages and disadvantages are compared.

  18. Optical Phase Lock Loop Based Phased Array Transmitter for Optical Commmunications

    NASA Astrophysics Data System (ADS)

    Vilenchik, Y.; Erkmen, B. I.; Satyan, N.; Yariv, A.; Farr, W. H.; Choi, J. M.

    2011-02-01

    We propose a novel deep space optical communication scheme, in which an integrated optical phased array (OPA) is used for both phase modulation and fine beam steering. In particular, an optical phase-locked loop (OPLL) based phased array with full electronic control over the phase is introduced and analyzed. The performance of such an array as a beam steering mechanism is evaluated and compared to realistic steering requirements for deep space applications. It is shown that an array with a high fill factor (>0.7) with about 300 elements per dimension is needed to meet these requirements. The effect of residual phase noise due to limited loop bandwidth is analyzed. Finally, the theory is validated by experimental results demonstrating successful beam steering using a two-element phased array.

  19. Interferometric study on Gouy phase anomaly of microlens array

    NASA Astrophysics Data System (ADS)

    Kim, Myun-Sik; Scharf, Toralf; Noell, Wilfried; Herzig, Hans Peter; Voelkel, Reinhard

    2015-03-01

    We investigate the Gouy phase anomaly of light in the focus of refractive plano-convex microlens arrays by using longitudinal-differential (LD) interferometry and a finite-difference time-domain (FDTD) simulation. We put emphasis on determining the amount of the Gouy phase shift for the line focus of the cylindrical lens and the point focus of the spherical lens. We discuss additional phase structures caused by diffraction, which lead to the discrepancy from the conventional Gouy phase shift.

  20. Design and control of phased ICRF antenna arrays

    SciTech Connect

    Goulding, R.H.; Baity, F.W.; Hoffman, D.J.

    1993-11-01

    Phased antenna arrays operating in the ion cyclotron range of frequencies (ICRF) are used to produce highly directional wave spectra, primarily for use in current drive experiments. RF current drive using phased antennas has been demonstrated in both the JET and DIII-D tokamaks, and both devices are planning to operate new four-element arrays beginning early next year. Features of antenna design that are relevant to phased operation and production of directional spectra are reviewed. Recent advances in the design of the feed circuits and the related control systems for these arrays should substantially improve their performance, by reducing the coupling seen by the matching networks and rf power supplies caused by the mutual impedance of the array elements. The feed circuit designs for the DIII-D and JET phased antenna arrays are compared. The two configurations differ significantly due to the fact that one power amplifier is used for the entire array in the former case, and one per element in the latter. The JET system uses automatic feedback control of matching, phase and amplitude of antenna currents, and the transmitter power balance. The design of this system is discussed, and a time dependent model used to predict its behavior is described.

  1. Three-dimensional ultrasound molecular imaging of angiogenesis in colon cancer using a clinical matrix array ultrasound transducer.

    PubMed

    Wang, Huaijun; Kaneko, Osamu F; Tian, Lu; Hristov, Dimitre; Willmann, Jürgen K

    2015-05-01

    We sought to assess the feasibility and reproducibility of 3-dimensional ultrasound molecular imaging (USMI) of vascular endothelial growth factor receptor 2 (VEGFR2) expression in tumor angiogenesis using a clinical matrix array transducer and a clinical grade VEGFR2-targeted contrast agent in a murine model of human colon cancer. Animal studies were approved by the Institutional Administrative Panel on Laboratory Animal Care. Mice with human colon cancer xenografts (n = 33) were imaged with a clinical ultrasound system and transducer (Philips iU22; X6-1) after intravenous injection of either clinical grade VEGFR2-targeted microbubbles or nontargeted control microbubbles. Nineteen mice were scanned twice to assess imaging reproducibility. Fourteen mice were scanned both before and 24 hours after treatment with either bevacizumab (n = 7) or saline only (n = 7). Three-dimensional USMI data sets were retrospectively reconstructed into multiple consecutive 1-mm-thick USMI data sets to simulate 2-dimensional imaging. Vascular VEGFR2 expression was assessed ex vivo using immunofluorescence. Three-dimensional USMI was highly reproducible using both VEGFR2-targeted microbubbles and nontargeted control microbubbles (intraclass correlation coefficient, 0.83). The VEGFR2-targeted USMI signal significantly (P = 0.02) decreased by 57% after antiangiogenic treatment compared with the control group, which correlated well with ex vivo VEGFR2 expression on immunofluorescence (ρ = 0.93, P = 0.003). If only central 1-mm tumor planes were analyzed to assess antiangiogenic treatment response, the USMI signal change was significantly (P = 0.006) overestimated by an average of 27% (range, 2%-73%) compared with 3-dimensional USMI. Three-dimensional USMI is feasible and highly reproducible and allows accurate assessment and monitoring of VEGFR2 expression in tumor angiogenesis in a murine model of human colon cancer.

  2. Three-dimensional Ultrasound Molecular Imaging of Angiogenesis in Colon Cancer using a Clinical Matrix Array Ultrasound Transducer

    PubMed Central

    Wang, Huaijun; Kaneko, Osamu F.; Tian, Lu; Hristov, Dimitre; Willmann, Jürgen K.

    2015-01-01

    Objectives We sought to assess the feasibility and reproducibility of three-dimensional (3D) ultrasound molecular imaging (USMI) of vascular endothelial growth factor receptor 2 (VEGFR2) expression in tumor angiogenesis using a clinical matrix array transducer and a clinical grade VEGFR2-targeted contrast agent in a murine model of human colon cancer. Materials and Methods Animal studies were approved by the Institutional Administrative Panel on Laboratory Animal Care. Mice with human colon cancer xenografts (n=33) were imaged with a clinical ultrasound system and transducer (Philips iU22; X6-1) following intravenous injection of either clinical grade VEGFR2-targeted microbubbles (MBVEGFR2) or non-targeted control microbubbles (MBControl). Nineteen mice were scanned twice to assess imaging reproducibility. Fourteen mice were scanned both before and 24h after treatment with either bevacizumab (n=7) or saline only (n=7). 3D USMI datasets were retrospectively reconstructed into multiple consecutive 1-mm thick USMI data sets to simulate 2D imaging. Vascular VEGFR2 expression was assessed ex vivo using immunofluorescence. Results 3D USMI was highly reproducible using both MBVEGFR2 and MBControl (ICC=0.83). VEGFR2-targeted USMI signal significantly (P=0.02) decreased by 57% following anti-angiogenic treatment compared to the control group, which correlated well with ex vivo VEGFR2 expression on immunofluorescence (rho=0.93, P=0.003). If only central 1-mm tumor planes were analyzed to assess anti-angiogenic treatment response, the USMI signal change was significantly (P=0.006) overestimated by an average of 27% (range, 2–73%) compared to 3D USMI. Conclusions 3D USMI is feasible and highly reproducible and allows accurate assessment and monitoring of VEGFR2 expression in tumor angiogenesis in a murine model of human colon cancer. PMID:25575176

  3. High-frequency (>50 MHz) medical ultrasound linear arrays fabricated from micromachined bulk PZT materials.

    PubMed

    Liu, Changgeng; Zhou, Qifa; Djuth, Frank T; Shung, K Kirk

    2012-02-01

    This paper describes the development and characterization of a high-frequency (65-MHz) ultrasound transducer linear array. The array was built from bulk PZT which was etched using an optimized chlorine-based plasma dry-etching process. The median etch rate of 8 µ m/h yielded a good profile (wall) angle (>83°) and a reasonable processing time for etch depths up to 40 μm (which corresponds to a 50-MHz transducer). A backing layer with an acoustic impedance of 6 MRayl and a front-end polymer matching layer yielded a transducer bandwidth of 40%. The major parameters of the transducer have been characterized. The two-way insertion loss and crosstalk between adjacent channels at the center frequency are 26.5 and -25 dB, respectively.

  4. High-Frequency (>50 MHz) Medical Ultrasound Linear Arrays Fabricated From Micromachined Bulk PZT Materials

    PubMed Central

    Liu, Changgeng; Zhou, Qifa; Djuth, Frank T.; Shung, K. Kirk

    2012-01-01

    This paper describes the development and characterization of a high-frequency (65-MHz) ultrasound transducer linear array. The array was built from bulk PZT which was etched using an optimized chlorine-based plasma dry-etching process. The median etch rate of 8 μm/h yielded a good profile (wall) angle (>83°) and a reasonable processing time for etch depths up to 40 μm (which corresponds to a 50-MHz transducer). A backing layer with an acoustic impedance of 6 MRayl and a front-end polymer matching layer yielded a transducer bandwidth of 40%. The major parameters of the transducer have been characterized. The two-way insertion loss and crosstalk between adjacent channels at the center frequency are 26.5 and −25 dB, respectively. PMID:24626041

  5. Full matrix capture and the total focusing imaging algorithm using laser induced ultrasonic phased arrays

    NASA Astrophysics Data System (ADS)

    Stratoudaki, Theodosia; Clark, Matt; Wilcox, Paul D.

    2017-02-01

    Laser ultrasonics is a technique where lasers are used for the generation and detection of ultrasound instead of conventional piezoelectric transducers. The technique is broadband, non-contact, and couplant free, suitable for large stand-off distances, inspection of components of complex geometries and hazardous environments. In this paper, array imaging is presented by obtaining the full matrix of all possible laser generation, laser detection combinations in the array (Full Matrix Capture), at the nondestructive, thermoelastic regime. An advanced imaging technique developed for conventional ultrasonic transducers, the Total Focusing Method (TFM), is adapted for laser ultrasonics and then applied to the captured data, focusing at each point of the reconstruction area. In this way, the beamforming and steering of the ultrasound is done during the post processing. A 1-D laser induced ultrasonic phased array is synthesized with significantly improved spatial resolution and defect detectability. In this study, shear waves are used for the imaging, since they are more efficiently produced than longitudinal waves in the nondestructive, thermoelastic regime. Experimental results are presented from nondestructive, laser ultrasonic inspection of aluminum samples with side drilled holes and slots at depths varying between 5 and 20mm from the surface.

  6. Adaptive optimization of ultrasound beamforming sound velocity using sub-aperture differential phase gradient.

    PubMed

    Shen, Che-Chou; Yang, Hsiao-Chi

    2017-08-01

    Ultrasound array imaging systems rely on a presumed beamforming sound velocity to calculate the time compensation of each element for receive focusing. The mismatch between the tissue sound velocity and the beamforming sound velocity can degrade the focusing quality due to loss of phase coherence. Since the tissue sound velocity cannot be known in prior, an adaptive optimization of beamforming sound velocity is required to improve the image quality. Differential phase gradient of channel data is proposed to estimate the optimal sound velocity for beamforming. The sound velocity optimization is achieved when the differential phase gradient between the left and the right sub-apertures approaches zero. Channel-domain autocorrelation is utilized for the estimation of phase gradient due to its high rejection to noise interference and low computational complexity. Results indicate that, compared to the conventional phase variance method, the proposed differential phase gradient reduces the standard deviation of sound velocity estimation from 0.5% to 0.2% while the accuracy remains comparable. The contrast ratio of the cyst region achieves the peak when the optimized sound velocity is utilized for beamforming. The lateral resolution of point target also improves by 14.3% after sound velocity optimization. The proposed method increases the robustness of sound velocity optimization. It is suggested to be implemented at transmit focal depth and without beam steering for better performance. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. An Agile Beam Transmit Array Using Coupled Oscillator Phase Control

    NASA Technical Reports Server (NTRS)

    Pogorzelski, Ronald S.; Scaramastra, Rocco P.; Huang, John; Beckon, Robert J.; Petree, Steve M.; Chavez, Cosme

    1993-01-01

    A few years ago York and colleagues suggested that injection locking of voltage controlled oscillators could be used to implement beam steering in a phased array [I]. The scheme makes use of the fact that when an oscillator is injection locked to an external signal, the phase difference between the output of the oscillator and the injection signal is governed by the difference between the injection frequency and the free running frequency of the oscillator (the frequency to which the oscillator is tuned). Thus, if voltage controlled oscillators (VCOs) are used, this phase difference is controlled by an applied voltage. Now, if a set of such oscillators are coupled to nearest neighbors, they can be made to mutually injection lock and oscillate as an ensemble. If they are all tuned to the same frequency, they will all oscillate in phase. Thus, if the outputs are connected to radiating elements forming a linear array, the antenna will radiate normal to the line of elements. Scanning is accomplished by antisymmetrically detuning the end oscillators in the array by application of a pair of appropriate voltages to their tuning ports. This results in a linear phase progression across the array which is just the phasing required to scan the beam. The scan angle is determined by the degree of detuning. We have constructed a seven element one dimensional agile beam array at S-band based on the above principle. Although, a few such arrays have been built in the past, this array possesses two unique features. First, the VCO MMICs have buffer amplifiers which isolate the output from the tuning circuit, and second, the oscillators are weakly coupled to each other at their resonant circuits rather than their outputs. This results in a convenient isolation between the oscillator array design and the radiating aperture design. An important parameter in the design is the so called coupling phase which determines the phase shift of the signals passing from one oscillator to its

  8. Phased array antenna beamforming using optical processor

    NASA Technical Reports Server (NTRS)

    Anderson, L. P.; Boldissar, F.; Chang, D. C. D.

    1991-01-01

    The feasibility of optical processor based beamforming for microwave array antennas is investigated. The primary focus is on systems utilizing the 20/30 GHz communications band and a transmit configuration exclusively to serve this band. A mathematical model is developed for computation of candidate design configurations. The model is capable of determination of the necessary design parameters required for spatial aspects of the microwave 'footprint' (beam) formation. Computed example beams transmitted from geosynchronous orbit are presented to demonstrate network capabilities. The effect of the processor on the output microwave signal to noise quality at the antenna interface is also considered.

  9. Reflector-based phase calibration of ultrasound transducers.

    PubMed

    van Neer, Paul L M J; Vos, Hendrik J; de Jong, Nico

    2011-01-01

    Recently, the measurement of phase transfer functions (PTFs) of piezoelectric transducers has received more attention. These PTFs are useful for e.g. coding and interference based imaging methods, and ultrasound contrast microbubble research. Several optical and acoustic methods to measure a transducer's PTF have been reported in literature. The optical methods require a setup to which not all ultrasound laboratories have access to. The acoustic methods require accurate distance and acoustic wave speed measurements. A small error in these leads to a large error in phase, e.g. an accuracy of 0.1% on an axial distance of 10cm leads to an uncertainty in the PTF measurement of ±97° at 4MHz. In this paper we present an acoustic pulse-echo method to measure the PTF of a transducer, which is based on linear wave propagation and only requires an estimate of the wave travel distance and the acoustic wave speed. In our method the transducer is excited by a monofrequency sine burst with a rectangular envelope. The transducer initially vibrates at resonance (transient regime) prior to the forcing frequency response (steady state regime). The PTF value of the system is the difference between the phases deduced from the transient and the steady state regimes. Good agreement, to within 7°, was obtained between KLM simulations and measurements on two transducers in a 1-8MHz frequency range. The reproducibility of the method was ±10°, with a systematic error of 2° at 1MHz increasing to 16° at 8MHz. This work demonstrates that the PTF of a transducer can be measured in a simple laboratory setting.

  10. Simple Array Beam-Shaping Using Phase-Only Adjustments.

    SciTech Connect

    Doerry, Armin W.

    2015-07-01

    Conventional beam-shaping for array antennas is accomplished via an amplitude-taper on the elemental radiators. It is well known that proper manipulation of the elemental phases can also shape the antenna far-field pattern. A fairly simple transformation from a desired amplitude-taper to a phase-taper can yield nearly equivalent results.

  11. Ultrasonic Phased-Array Characterization for NDE Applications

    NASA Technical Reports Server (NTRS)

    Hanley, John J.; Tennis, Richard F.; Pickens, Keith S.

    1995-01-01

    Southwest Research Institute (SwRI) recently fabricated and delivered the 100-channel Ultrasonic Phased-Array Testbed System (UPATS) for NASA's Langley Research Center. NASA prepared the specifications and provided the funding to develop UPATS in order to provide a tool for the improvement of ultrasonic nondestructive evaluation (NDE) and characterization of materials. UPATS incorporates state-of-the-art phased-array concepts such as beam steering, focusing, apodization, and phase-sensitive detection which make it possible to develop more sophisticated testing methodologies. It also can be used to investigate fundamental ultrasonic propagation and detection phenomena such as refraction, diffraction, scattering, and beam broadening.

  12. Diffraction-limited circular single spot from phased array lasers

    SciTech Connect

    Tatsuno, K.; Drenten, R.; Poel, C.v.d.; Opschoor, J.; Acket, G. )

    1989-11-01

    Anamorphic prism optics makes it possible to obtain a diffraction-limited ({Sigma}/8) circular single spot from index guided phased array lasers. It served not only for beam shaping but also for astigmatism correction and spatial filtering. The optical path analysis based on the interferometric fringe scanning phase measurements both in the near and far fields indicates that the phased array lasers can be applied to such diffraction-limited precise optical systems as optical disk recording, laser beam printing, or second harmonics generation.

  13. Optical phased array radiating optical vortex with manipulated topological charges.

    PubMed

    Ma, Xiaoliang; Pu, Mingbo; Li, Xiong; Huang, Cheng; Pan, Wenbo; Zhao, Bo; Cui, Jianhua; Luo, Xiangang

    2015-02-23

    Optical antennas are key elements in quantum optics emitting and sensing, and behave wide range applications in optical domain. However, integration of optical antenna radiating orbital angular momentum is still a challenge in nano-scale. We theoretically demonstrate a sub-wavelength phased optical antenna array, which manipulates the distribution of the orbital angular momentum in the near field. Orbital angular momentum with topological charge of 4 can be obtained by controlling the phase distribution of the fundamental mode orbital angular momentum in each antenna element. Our results indicate this phased array may be utilized in high integrated optical communication systems.

  14. Non-invasive transcranial surgery with dual-mode ultrasound arrays

    NASA Astrophysics Data System (ADS)

    Haritonova, Alyona; Liu, Dalong; Wilken-Resman, Elias; Bayat, Mahdi; Wang, Xiao; Chen, Wei; Divani, Afshin; Ebbini, Emad

    2017-03-01

    We present the first transcranial mapping of temperature with Dual-Mode Ultrasound Arrays (DMUAs), with subsequent validation of transskull ultrasound therapy guidance and monitoring in a small rodent model. Experiments were conducted in sacrificed rats, utilizing the custom designed DMUA platform manufactured in our laboratory. First, careful examination of DMUA imaging through the skull was conducted, where a fine 50μm wire was embedded within the brain tissue. Second, anatomical landmarks were visualized by co-registering two volumes, volume of synthetic aperture (SA) images acquired with DMUA and a 9.4T MRI volume acquired in live rats prior to the sacrifice. Third, subtherapeutic shot delivery through the skull was tested, where a set of five varying intensity shots were deposited below the skull surface. Shot delivery and temperature monitoring were performed with DMUA, and compared with the thermocouple data acquired close to the therapeutic focus. This study was an exploratory effort to validate ultrasound therapy delivery and monitoring in transcranial applications with DMUAs. In conclusion, DMUAs offer a unique advantage by providing real-time feedback by means of temperature monitoring with a high degree of spatial localization.

  15. A Method for Accurate in silico modeling of Ultrasound Transducer Arrays

    PubMed Central

    Guenther, Drake A.; Walker, William F.

    2009-01-01

    This paper presents a new approach to improve the in silico modeling of ultrasound transducer arrays. While current simulation tools accurately predict the theoretical element spatio-temporal pressure response, transducers do not always behave as theorized. In practice, using the probe's physical dimensions and published specifications in silico, often results in unsatisfactory agreement between simulation and experiment. We describe a general optimization procedure used to maximize the correlation between the observed and simulated spatio-temporal response of a pulsed single element in a commercial ultrasound probe. A linear systems approach is employed to model element angular sensitivity, lens effects, and diffraction phenomena. A numerical deconvolution method is described to characterize the intrinsic electro-mechanical impulse response of the element. Once the response of the element and optimal element characteristics are known, prediction of the pressure response for arbitrary apertures and excitation signals is performed through direct convolution using available tools. We achieve a correlation of 0.846 between the experimental emitted waveform and simulated waveform when using the probe's physical specifications in silico. A far superior correlation of 0.988 is achieved when using the optimized in silico model. Electronic noise appears to be the main effect preventing the realization of higher correlation coefficients. More accurate in silico modeling will improve the evaluation and design of ultrasound transducers as well as aid in the development of sophisticated beamforming strategies. PMID:19041997

  16. EMAT phased array: A feasibility study of surface crack detection.

    PubMed

    Isla, J; Cegla, F

    2017-02-14

    Electromagnetic-acoustic transducers (EMATs) consist of a magnet and a coil. They are advantageous in some non-destructive evaluation (NDE) applications because no direct contact with the specimen is needed to send and receive ultrasonic waves. However, EMATs commonly require excitation peak powers greater than 1kW and therefore the driving electronics and the EMAT coils have to be bulky. This has hindered the development of EMAT phased arrays with characteristics similar to those of conventional piezoelectric phased arrays. Phased arrays are widely used in NDE because they offer superior defect characterization in comparison to single-element transducers. In this paper, we report a series of novel techniques and design elements that make it possible to construct an EMAT phased array that performs similarly to conventional piezoelectric arrays used in NDE. One of the key enabling features is the use of coded excitation to reduce the excitation peak power to less than 4.8W (24 Vpp and 200mA) so that racetrack coils with dimensions 3.2×18mm(2) can be employed. Moreover, these racetrack coils are laid out along their shortest dimension so that 1/3 of their area is overlapped. This helps to reduce the crosstalk between the coils, i.e., the array elements, to less than -15dB. We show that an 8-element EMAT phased array operating at a central frequency of 1MHz can be used to detect defects which have a width and a depth of 0.2 and 0.8mm respectively and are located on the surface opposite to the array.

  17. A conformal SHF phased array for aircraft satellite communication

    NASA Astrophysics Data System (ADS)

    Cummings, R.; Kudrna, K.

    1984-03-01

    A receive-only 7.5 GHz microstrip phased array has been developed by Ball Aerospace Systems Division (BASD). This 256 radiating element array provides a gain of 20 dBic over a conical scan region of 120 deg. Two arrays with one on either side of an aircraft would provide near hemispherical coverage. The array consists of four subarrays and can be expanded to achieve higher gain when required. The array is left-hand circularly polarized and has three-bit digital PIN diode phase shifters for steering the beam. A microprocessor-based beam steering controller is used for calculating the phase shifter settings for each beam position. Each subarray includes radiating elements, quadrature hybrids, phase shifters, corporate feed, R.F. chokes in microstrip medium and hybrid PIN diode drivers. The array is approximately 1.5 inches thick and is conformal to the aircraft skin. It is a bolt on assembly only requiring aircraft skin entries for the R.F. output and for control lines. Transmit capability can be provided by merely changing the artwork to go to 8.5 GHz.

  18. A design concept for an MMIC microstrip phased array

    NASA Technical Reports Server (NTRS)

    Lee, R. Q.; Smetana, J.; Acosta, R.

    1986-01-01

    A conceptual design for a microstrip phased array with monolithic microwave integrated circuit (MMIC) amplitude and phase controls is described. The MMIC devices used are 20 GHz variable power amplifiers and variable phase shifters recently developed by NASA contractors for applications in future Ka band advanced satellite communication antenna systems. The proposed design concept is for a general NxN element array of rectangular lattice geometry. Subarray excitation is incorporated in the MMIC phased array design to reduce the complexity of the beam forming network and the number of MMIC components required. The proposed design concept takes into consideration the RF characteristics and actual phyical dimensions of the MMIC devices. Also, solutions to spatial constraints and interconnections associated with currently available packaging designs are discussed. Finally, the design of the microstrip radiating elements and their radiation characteristics are examined.

  19. Phased Array Radiometer Calibration Using a Radiated Noise Source

    NASA Technical Reports Server (NTRS)

    Srinivasan, Karthik; Limaye, Ashutoch S.; Laymon, Charles A.; Meyer, Paul J.

    2010-01-01

    Electronic beam steering capability of phased array antenna systems offer significant advantages when used in real aperture imaging radiometers. The sensitivity of such systems is limited by the ability to accurately calibrate variations in the antenna circuit characteristics. Passive antenna systems, which require mechanical rotation to scan the beam, have stable characteristics and the noise figure of the antenna can be characterized with knowledge of its physical temperature [1],[2]. Phased array antenna systems provide the ability to electronically steer the beam in any desired direction. Such antennas make use of active components (amplifiers, phase shifters) to provide electronic scanning capability while maintaining a low antenna noise figure. The gain fluctuations in the active components can be significant, resulting in substantial calibration difficulties [3]. In this paper, we introduce two novel calibration techniques that provide an end-to-end calibration of a real-aperture, phased array radiometer system. Empirical data will be shown to illustrate the performance of both methods.

  20. A design concept for an MMIC microstrip phased array

    NASA Astrophysics Data System (ADS)

    Lee, R. Q.; Smetana, J.; Acosta, R.

    A conceptual design for a microstrip phased array with monolithic microwave integrated circuit (MMIC) amplitude and phase controls is described. The MMIC devices used are 20 GHz variable power amplifiers and variable phase shifters recently developed by NASA contractors for applications in future Ka band advanced satellite communication antenna systems. The proposed design concept is for a general NxN element array of rectangular lattice geometry. Subarray excitation is incorporated in the MMIC phased array design to reduce the complexity of the beam forming network and the number of MMIC components required. The proposed design concept takes into consideration the RF characteristics and actual phyical dimensions of the MMIC devices. Also, solutions to spatial constraints and interconnections associated with currently available packaging designs are discussed. Finally, the design of the microstrip radiating elements and their radiation characteristics are examined.

  1. Clinical results of real-time ultrasonic scanning of the heart using a phased array system.

    PubMed

    Kisslo, J A; vonRamm, O T; Thurstone, F L

    1977-01-01

    This report describes the operating characteristics and initial clinical results of a new echocardiographic system that produces real-time, high resolution, cross-sectional images of the heart. This system relies upon phased-array principles to rapidly steer and focus the ultrasound beam through the cardiac structures under investigation. A hand-held, linear array of 24 transducers is manipulated on the patient's chest to direct the interrogating plane at various cardiac structures. Images of high line density are presented in selectable sector arcs to a maximum of 90 degrees. This imaging system has been used clinically in over 2,000 patients in the past two and one-half years. Its use in the detection of altered states of ventricular and valvular pathology has been described.

  2. A 5-MHz cylindrical dual-layer transducer array for 3-D transrectal ultrasound imaging.

    PubMed

    Chen, Yuling; Nguyen, Man; Yen, Jesse T

    2012-07-01

    Two-dimensional transrectal ultrasound (TRUS) is being used in guiding prostate biopsies and treatments. In many cases, the TRUS probes are moved manually or mechanically to acquire volumetric information, making the imaging slow, user dependent, and unreliable. A real-time three-dimensional (3-D) TRUS system could improve reliability and volume rates of imaging during these procedures. In this article, the authors present a 5-MHz cylindrical dual-layer transducer array capable of real-time 3-D transrectal ultrasound without any mechanically moving parts. Compared with fully sampled 2-D arrays, this design substantially reduces the channel count and fabrication complexity. This dual-layer transducer uses PZT elements for transmit and P[VDF-TrFE] copolymer elements for receive, respectively. The mechanical flexibility of both diced PZT and copolymer makes it practical for transrectal applications. Full synthetic aperture 3-D data sets were acquired by interfacing the transducer with a Verasonics Data Acquisition System. Offline 3-D beamforming was then performed to obtain volumes of two wire phantoms and a cyst phantom. Generalized coherence factor was applied to improve the contrast of images. The measured -6-dB fractional bandwidth of the transducer was 62% with a center frequency of 5.66 MHz. The measured lateral beamwidths were 1.28 mm and 0.91 mm in transverse and longitudinal directions, respectively, compared with a simulated beamwidth of 0.92 mm and 0.74 mm.

  3. Conformal Bulk Ablation And Therapy Monitoring Using Intracorporeal Image-Treat Ultrasound Arrays

    NASA Astrophysics Data System (ADS)

    Makin, I. R.; Faidi, W.; Mast, T. D.; Runk, M.; Slayton, M.; Barthe, P.

    2005-03-01

    For thermal treatment of soft tissue, an alternative to HIFU is bulk ablation using unfocused or weakly focused intense ultrasound fields. This approach offers faster ablation of large tissue volumes and can be performed in minimally invasive (e.g., laparoscopic or percutaneous) procedures. Here, methods for image-guided ablation of large tissue volumes using compact dual-modality (image and treat) ultrasound arrays are reported including tissue modification caused by the thermal therapy. The dual-modality arrays developed have 16-64 elements spanning apertures of 2-8 mm in elevation and 24-48 mm in azimuth. These devices can provide both therapeutically significant power (e.g. source intensity > 80 W/cm2 at 3.1 MHz) and broad bandwidth (e.g. 50% with a center frequency of 3.5 MHz) for imaging. Imaging challenges associated with limited probe dimensions and channel count are met using signal processing techniques that improve definition and contrast, allowing high-quality B-scan images and useful monitoring information to be obtained during therapy planning and treatment. Using linear and rotational scanning methods, large tissue volumes (20-60 cc) can be treated. The approach can be applied for ablation of other soft tissue pathologies, e.g., kidney, heart, uterus, brain, GI tract, etc.

  4. Transmit beamforming techniques for suppressing grating lobes in large pitch ultrasonic phased arrays

    NASA Astrophysics Data System (ADS)

    Torbatian, Zahra; Adamson, Rob; Bance, Manohar; Brown, Jeremy A.

    2011-03-01

    To date, clinical implementation of high-frequency ultrasound has been limited due to the difficulties in fabricating sufficiently small micro-array transducers. Specifically, if an array is desired with the ability to beam-steer to large angles, an inter-element pitch of approximately .5λ is required to avoid grating lobe artifacts. At high-frequencies (30-70MHz), this introduces major fabrication challenges since the required element pitch is between 10 and 25 microns. A new technique called Phase Coherence Imaging has been introduced in the literature for suppressing grating lobes in large-pitch arrays by calculating a weighting factor proportional to the instantaneous phase coherence of the received element echoes. If the reflected echoes in the grating lobe region are relatively broadband, only some of the echoes will overlap and the resulting weighting factor will be less. Unfortunately, most beamforming techniques result in relatively narrowband echoes in the grating lobe region, making this technique less effective. We have developed a technique that splits the N-element transmit aperture into N/K transmit elements and N receive elements in order to better suppress grating lobes by increasing the bandwidth of the grating lobe echoes. We have also developed a technique that uses a probing pulse from a virtual point source behind the array in order to pre-calculate weighting factors from broadband echoes before conventional transmit beamforming is used. Radiation patterns have been simulated and the amount of grating lobe suppression has been quantified using the proposed techniques. It has been shown that these techniques are very effective in suppressing grating lobes in large-pitch phased-arrays, potentially simplifying high-frequency array fabrication.

  5. New piezocrystal material in the development of a 96-element array transducer for MR-guided focused ultrasound surgery

    NASA Astrophysics Data System (ADS)

    Qiu, Zhen; Habeshaw, Roderick; Fortine, Julien; Huang, Zhihong; Démoré, Christine; Cochran, Sandy

    2012-11-01

    Piezocrystal materials have been recognized as having better performance than piezoelectric ceramics, and have thus been widely adopted in ultrasound imaging arrays. Although their behaviour is susceptible to temperature and pressure, their large electromechanical coupling coefficients and other excellent piezoelectric properties also offer the potential for further improvements in the efficiency of therapeutic ultrasound transducers. Furthermore, new piezocrystals with modified compositions have been developed recently to increase their tolerance to temperature and pressure. In this work, a prototype of faceted bowl transducer was designed and manufactured as a proof of concept to explore practical issues associated with adoption of piezocrystals for magnetic resonance imaging guided focused ultrasound surgery.

  6. Code-modulated interferometric imaging system using phased arrays

    NASA Astrophysics Data System (ADS)

    Chauhan, Vikas; Greene, Kevin; Floyd, Brian

    2016-05-01

    Millimeter-wave (mm-wave) imaging provides compelling capabilities for security screening, navigation, and bio- medical applications. Traditional scanned or focal-plane mm-wave imagers are bulky and costly. In contrast, phased-array hardware developed for mass-market wireless communications and automotive radar promise to be extremely low cost. In this work, we present techniques which can allow low-cost phased-array receivers to be reconfigured or re-purposed as interferometric imagers, removing the need for custom hardware and thereby reducing cost. Since traditional phased arrays power combine incoming signals prior to digitization, orthogonal code-modulation is applied to each incoming signal using phase shifters within each front-end and two-bit codes. These code-modulated signals can then be combined and processed coherently through a shared hardware path. Once digitized, visibility functions can be recovered through squaring and code-demultiplexing operations. Pro- vided that codes are selected such that the product of two orthogonal codes is a third unique and orthogonal code, it is possible to demultiplex complex visibility functions directly. As such, the proposed system modulates incoming signals but demodulates desired correlations. In this work, we present the operation of the system, a validation of its operation using behavioral models of a traditional phased array, and a benchmarking of the code-modulated interferometer against traditional interferometer and focal-plane arrays.

  7. Interventional multispectral photoacoustic imaging with a clinical linear array ultrasound probe for guiding nerve blocks

    NASA Astrophysics Data System (ADS)

    Xia, Wenfeng; West, Simeon J.; Nikitichev, Daniil I.; Ourselin, Sebastien; Beard, Paul C.; Desjardins, Adrien E.

    2016-03-01

    Accurate identification of tissue structures such as nerves and blood vessels is critically important for interventional procedures such as nerve blocks. Ultrasound imaging is widely used as a guidance modality to visualize anatomical structures in real-time. However, identification of nerves and small blood vessels can be very challenging, and accidental intra-neural or intra-vascular injections can result in significant complications. Multi-spectral photoacoustic imaging can provide high sensitivity and specificity for discriminating hemoglobin- and lipid-rich tissues. However, conventional surface-illumination-based photoacoustic systems suffer from limited sensitivity at large depths. In this study, for the first time, an interventional multispectral photoacoustic imaging (IMPA) system was used to image nerves in a swine model in vivo. Pulsed excitation light with wavelengths in the ranges of 750 - 900 nm and 1150 - 1300 nm was delivered inside the body through an optical fiber positioned within the cannula of an injection needle. Ultrasound waves were received at the tissue surface using a clinical linear array imaging probe. Co-registered B-mode ultrasound images were acquired using the same imaging probe. Nerve identification was performed using a combination of B-mode ultrasound imaging and electrical stimulation. Using a linear model, spectral-unmixing of the photoacoustic data was performed to provide image contrast for oxygenated and de-oxygenated hemoglobin, water and lipids. Good correspondence between a known nerve location and a lipid-rich region in the photoacoustic images was observed. The results indicate that IMPA is a promising modality for guiding nerve blocks and other interventional procedures. Challenges involved with clinical translation are discussed.

  8. Highly precise acoustic calibration method of ring-shaped ultrasound transducer array for plane-wave-based ultrasound tomography

    NASA Astrophysics Data System (ADS)

    Terada, Takahide; Yamanaka, Kazuhiro; Suzuki, Atsuro; Tsubota, Yushi; Wu, Wenjing; Kawabata, Ken-ichi

    2017-07-01

    Ultrasound computed tomography (USCT) is promising for a non-invasive, painless, operator-independent and quantitative system for breast-cancer screening. Assembly error, production tolerance, and aging-degradation variations of the hardwire components, particularly of plane-wave-based USCT systems, may hamper cost effectiveness, precise imaging, and robust operation. The plane wave is transmitted from a ring-shaped transducer array for receiving the signal at a high signal-to-noise-ratio and fast aperture synthesis. There are four signal-delay components: response delays in the transmitters and receivers and propagation delays depending on the positions of the transducer elements and their directivity. We developed a highly precise calibration method for calibrating these delay components and evaluated it with our prototype plane-wave-based USCT system. Our calibration method was found to be effective in reducing delay errors. Gaps and curves were eliminated from the plane wave, and echo images of wires were sharpened in the entire imaging area.

  9. Optical RF distribution links for MMIC phased array antennas

    NASA Technical Reports Server (NTRS)

    Kunath, Richard R.; Bhasin, Kul B.; Raquet, Charles A.

    1987-01-01

    Conventional methods to distribute RF signals to GaAs Monolithic Microwave Integrated Circuits Phased Array Antennas are inadequate for arrays having large numbers of elements. Optical RF distribution links have been proposed as a lightweight, mechanically flexible, and low volume solution. Three candidate techniques for providing optical RF distribution are discussed along with the electro-optic devices required to configure them. A discussion of the present status of applicable electro-optics devices is also included.

  10. Phased-Array Antenna With Optoelectronic Control Circuits

    NASA Technical Reports Server (NTRS)

    Kunath, Richard R.; Shalkhauser, Kurt A.; Martzaklis, Konstantinos; Lee, Richard Q.; Downey, Alan N.; Simons, Rainee N.

    1995-01-01

    Prototype phased-array antenna features control of amplitude and phase at each radiating element. Amplitude- and phase-control signals transmitted on optical fiber to optoelectronic interface circuit (OEIC), then to monolithic microwave integrated circuit (MMIC) at each element. Offers advantages of flexible, rapid electronic steering and shaping of beams. Furthermore, greater number of elements, less overall performance of antenna degraded by malfunction in single element.

  11. Reconfigurable Infrared Phased-Array Semiconductor Metasurfaces

    NASA Astrophysics Data System (ADS)

    Schuller, Jon

    The ability to engineer the scattering phase of metamaterial constituents offers tremendous potential for constructing new classes of beam steering, shaping, and focusing technologies. Current methods for engineering phase rely on static geometry-based effects. In this talk we describe methods to dynamically tune the scattering phase of infrared semiconductor nanoantennas. We fabricate spherical silicon and germanium nanoparticles via femtosecond laser ablation and demonstrate size-dependent multipolar resonances throughout the infrared frequency range. We experimentally demonstrate that the resonance frequencies shift with doping, according to simple Drude models of free-carrier refraction. Using a combination of theoretical and analytical calculations we show that dynamically tuning free-carrier concentration can enable reconfigurable optical antennas and metasurfaces. Such dynamic tuning will enable reconfigurable photonic devices based on optical antenna and metamaterial concepts.

  12. Optoelectronic Infrastructure for Radio Frequency and Optical Phased Arrays

    NASA Technical Reports Server (NTRS)

    Cai, Jianhong

    2015-01-01

    Optoelectronic integrated circuits offer radiation-hardened solutions for satellite systems in addition to improved size, weight, power, and bandwidth characteristics. ODIS, Inc., has developed optoelectronic integrated circuit technology for sensing and data transfer in phased arrays. The technology applies integrated components (lasers, amplifiers, modulators, detectors, and optical waveguide switches) to a radio frequency (RF) array with true time delay for beamsteering. Optical beamsteering is achieved by controlling the current in a two-dimensional (2D) array. In this project, ODIS integrated key components to produce common RF-optical aperture operation.

  13. Optical beam forming techniques for phased array antennas

    NASA Technical Reports Server (NTRS)

    Wu, Te-Kao; Chandler, C.

    1993-01-01

    Conventional phased array antennas using waveguide or coax for signal distribution are impractical for large scale implementation on satellites or spacecraft because they exhibit prohibitively large system size, heavy weight, high attenuation loss, limited bandwidth, sensitivity to electromagnetic interference (EMI) temperature drifts and phase instability. However, optical beam forming systems are smaller, lighter, and more flexible. Three optical beam forming techniques are identified as applicable to large spaceborne phased array antennas. They are (1) the optical fiber replacement of conventional RF phased array distribution and control components, (2) spatial beam forming, and (3) optical beam splitting with integrated quasi-optical components. The optical fiber replacement and the spatial beam forming approaches were pursued by many organizations. Two new optical beam forming architectures are presented. Both architectures involve monolithic integration of the antenna radiating elements with quasi-optical grid detector arrays. The advantages of the grid detector array in the optical process are the higher power handling capability and the dynamic range. One architecture involves a modified version of the original spatial beam forming approach. The basic difference is the spatial light modulator (SLM) device for controlling the aperture field distribution. The original liquid crystal light valve SLM is replaced by an optical shuffling SLM, which was demonstrated for the 'smart pixel' technology. The advantages are the capability of generating the agile beams of a phased array antenna and to provide simultaneous transmit and receive functions. The second architecture considered is the optical beam splitting approach. This architecture involves an alternative amplitude control for each antenna element with an optical beam power divider comprised of mirrors and beam splitters. It also implements the quasi-optical grid phase shifter for phase control and grid

  14. Optical beam forming techniques for phased array antennas

    NASA Astrophysics Data System (ADS)

    Wu, Te-Kao; Chandler, C.

    Conventional phased array antennas using waveguide or coax for signal distribution are impractical for large scale implementation on satellites or spacecraft because they exhibit prohibitively large system size, heavy weight, high attenuation loss, limited bandwidth, sensitivity to electromagnetic interference (EMI) temperature drifts and phase instability. However, optical beam forming systems are smaller, lighter, and more flexible. Three optical beam forming techniques are identified as applicable to large spaceborne phased array antennas. They are (1) the optical fiber replacement of conventional RF phased array distribution and control components, (2) spatial beam forming, and (3) optical beam splitting with integrated quasi-optical components. The optical fiber replacement and the spatial beam forming approaches were pursued by many organizations. Two new optical beam forming architectures are presented. Both architectures involve monolithic integration of the antenna radiating elements with quasi-optical grid detector arrays. The advantages of the grid detector array in the optical process are the higher power handling capability and the dynamic range. One architecture involves a modified version of the original spatial beam forming approach. The basic difference is the spatial light modulator (SLM) device for controlling the aperture field distribution. The original liquid crystal light valve SLM is replaced by an optical shuffling SLM, which was demonstrated for the 'smart pixel' technology. The advantages are the capability of generating the agile beams of a phased array antenna and to provide simultaneous transmit and receive functions. The second architecture considered is the optical beam splitting approach. This architecture involves an alternative amplitude control for each antenna element with an optical beam power divider comprised of mirrors and beam splitters. It also implements the quasi-optical grid phase shifter for phase control and grid

  15. Optical beam forming techniques for phased array antennas

    NASA Technical Reports Server (NTRS)

    Wu, Te-Kao; Chandler, C.

    1993-01-01

    Conventional phased array antennas using waveguide or coax for signal distribution are impractical for large scale implementation on satellites or spacecraft because they exhibit prohibitively large system size, heavy weight, high attenuation loss, limited bandwidth, sensitivity to electromagnetic interference (EMI) temperature drifts and phase instability. However, optical beam forming systems are smaller, lighter, and more flexible. Three optical beam forming techniques are identified as applicable to large spaceborne phased array antennas. They are (1) the optical fiber replacement of conventional RF phased array distribution and control components, (2) spatial beam forming, and (3) optical beam splitting with integrated quasi-optical components. The optical fiber replacement and the spatial beam forming approaches were pursued by many organizations. Two new optical beam forming architectures are presented. Both architectures involve monolithic integration of the antenna radiating elements with quasi-optical grid detector arrays. The advantages of the grid detector array in the optical process are the higher power handling capability and the dynamic range. One architecture involves a modified version of the original spatial beam forming approach. The basic difference is the spatial light modulator (SLM) device for controlling the aperture field distribution. The original liquid crystal light valve SLM is replaced by an optical shuffling SLM, which was demonstrated for the 'smart pixel' technology. The advantages are the capability of generating the agile beams of a phased array antenna and to provide simultaneous transmit and receive functions. The second architecture considered is the optical beam splitting approach. This architecture involves an alternative amplitude control for each antenna element with an optical beam power divider comprised of mirrors and beam splitters. It also implements the quasi-optical grid phase shifter for phase control and grid

  16. The Potential of Phased Arrays for Planetary Exploration

    NASA Technical Reports Server (NTRS)

    Pogorzelski, Ronald J.

    2000-01-01

    Phased array antennas provide a set of operational capabilities which are very attractive for certain mission applications and not very attractive for others. Such antennas are by no means a panacea for telecommunications. In this paper the features of phased arrays are reviewed and their implications for space missions are considered in terms of benefits and costs. The primary capability provided by a phased array is electronic beam agility. The beam direction may be controlled at electronic speeds (vs. mechanical actuation) permitting time division multiplexing of multiple "users." Moreover, the beam direction can be varied over a full hemisphere (for a planar array). On the other hand, such antennas are typically much more complicated than the more commonly used reflectors and horns and this implies higher cost. In some applications, this increased cost must be accepted if the mission is to be carried out at all. The SIR-C radar is an example of such a case albeit not for deep space. Assuming for the sake of argument that the complexity and cost of a phased array can be significantly reduced, where can such antennas be of value in the future of planetary exploration? Potential applications to be discussed are planetary rovers, landers, and orbiters including both the areosynchronous and low orbit varieties. In addition, consideration is given to links from deep space to earth. As may be fairly obvious, the deep space link to earth would not benefit from the wide angle steering capability provided by a phase array whereas a rover could gain advantage from the capability to steer a beam anywhere in the sky. In the rover case, however, physical size of the aperture becomes a significant factor which, of course, has implications regarding the choice of frequency band. Recent research work concerning phased arrays has suggested that future phased arrays might be made less complex and, therefore, less costly. Successful realization of such phased arrays would enable

  17. Ultrasound aided photochemical synthesis of Ag loaded TiO2 nanotube arrays to enhance photocatalytic activity.

    PubMed

    Sun, Lan; Li, Jing; Wang, Chenglin; Li, Sifang; Lai, Yuekun; Chen, Hongbo; Lin, Changjian

    2009-11-15

    This work presents a novel approach for preparing TiO(2) nanotube array photocatalyst loaded with highly dispersed Ag nanoparticles through an ultrasound aided photochemical route. The Ag content loaded on the array was controlled by changing the concentration of AgNO(3) solution. The Ag-TiO(2) nanotube arrays were characterized by SEM, XRD, XPS and UV-vis absorption. The effects of Ag content on the photoelectrochemical (PEC) property and photocatalytic activity of TiO(2) nanotube array electrode were studied. The results showed that Ag loading significantly enhanced the photocurrent and photocatalytic degradation rate of TiO(2) nanotube array under UV-light irradiation. The photocurrent and photocatalytic degradation rate of Ag-TiO(2) nanotube array prepared in 0.006 M AgNO(3) solution were about 1.2 and 3.7 times as that of pure TiO(2) nanotube array, respectively.

  18. A Parameterized Pattern-Error Objective for Large-Scale Phase-Only Array Pattern Design

    DTIC Science & Technology

    2016-03-21

    array pattern Array synthesis Transmit array pattern Array pattern optimization Phase-only optimization Modern phased-array radar systems increasingly...the most trivial phase-only optimizations are nonconvex and thus may have large numbers of local optima. In most fielded radar systems only the...existing approaches to phase-only array design can be roughly divided into heuristic, nonlocal optimization , and local optimization methods. The first two

  19. Full-matrix capture with a customizable phased array instrument

    NASA Astrophysics Data System (ADS)

    Dao, Gavin; Braconnier, Dominique; Gruber, Matt

    2015-03-01

    In recent years, a technique known as Full-Matrix Capture (FMC) has gained some headway in the NDE community for phased array applications. It's important to understand that FMC is the method that the instrumentation acquires the ultrasonic signals, but further post-processing is required in software to create a meaningful image for a particular application. Having a flexible software interface, small form factor, excellent signal-to-noise ratio per acquisition channel on a 64/64 or 128/128 phased array module with FMC capability proves beneficial in both industrial implementation and in further investigation of post-processing techniques. This paper will provide an example of imaging with a 5MHz linear phased array transducer with 128 elements using FMC and a popular post-processing algorithm known as Total-Focus Method (TFM).

  20. Phased arrays for satellites and the TDRSS antennas

    NASA Astrophysics Data System (ADS)

    Imbriale, W. A.

    The design and performance of satellite phased-array systems are examined by considering several specific antennas built for spacecraft use. Particular consideration is given to: (1) the JARED (Jammer Reduction Antenna System) antenna, and adaptive phased array which can be used to null jammer signals while providing coverage to specific user areas; (2) the algorithm used in the JARED antenna; and (3) a technique that can be used to detect and locate jammers. The antennas used by the Tracking and Data Relay Satellite System (TDRSS) are then described. A significant aspect of the TDRSS is the multiple access antenna which is a 30-element phased array, providing a single steered beam on transmit and the ability to receive data from 20 simultaneous users. Also included on the TDRSS is a mesh deployable reflector and a C-band and K-band communications system.

  1. Phased arrays for satellites and the TDRSS antennas

    NASA Technical Reports Server (NTRS)

    Imbriale, W. A.

    1983-01-01

    The design and performance of satellite phased-array systems are examined by considering several specific antennas built for spacecraft use. Particular consideration is given to: (1) the JARED (Jammer Reduction Antenna System) antenna, and adaptive phased array which can be used to null jammer signals while providing coverage to specific user areas; (2) the algorithm used in the JARED antenna; and (3) a technique that can be used to detect and locate jammers. The antennas used by the Tracking and Data Relay Satellite System (TDRSS) are then described. A significant aspect of the TDRSS is the multiple access antenna which is a 30-element phased array, providing a single steered beam on transmit and the ability to receive data from 20 simultaneous users. Also included on the TDRSS is a mesh deployable reflector and a C-band and K-band communications system.

  2. System response in passively phased fiber amplifier arrays

    NASA Astrophysics Data System (ADS)

    Shakir, Sami A.; Culver, Bill; Nelson, Burke; Starcher, Yuji; Bates, George M.; Hedrick, Jerry W., Jr.

    2008-08-01

    System temporal response in passively phased fiber amplifier arrays dictates how fast a passively phased system can correct for phase fluctuations due to thermal and mechanical effects. The system response time was measured by employing a variable-speed mechanical chopper in the feedback loop of a passively phased system then measuring the on-axis output intensity of the system as a function of time. Observed relaxation oscillations are compared to theory. The system response time was measured to be about 20 μsec. We also find that passive phasing improved the system's beam stability and extraction efficiency.

  3. Research on calibration error of carrier phase against antenna arraying

    NASA Astrophysics Data System (ADS)

    Sun, Ke; Hou, Xiaomin

    2016-11-01

    It is the technical difficulty of uplink antenna arraying that signals from various quarters can not be automatically aligned at the target in deep space. The size of the far-field power combining gain is directly determined by the accuracy of carrier phase calibration. It is necessary to analyze the entire arraying system in order to improve the accuracy of the phase calibration. This paper analyzes the factors affecting the calibration error of carrier phase of uplink antenna arraying system including the error of phase measurement and equipment, the error of the uplink channel phase shift, the position error of ground antenna, calibration receiver and target spacecraft, the error of the atmospheric turbulence disturbance. Discuss the spatial and temporal autocorrelation model of atmospheric disturbances. Each antenna of the uplink antenna arraying is no common reference signal for continuous calibration. So it must be a system of the periodic calibration. Calibration is refered to communication of one or more spacecrafts in a certain period. Because the deep space targets are not automatically aligned to multiplexing received signal. Therefore the aligned signal should be done in advance on the ground. Data is shown that the error can be controlled within the range of demand by the use of existing technology to meet the accuracy of carrier phase calibration. The total error can be controlled within a reasonable range.

  4. Adaptive array technique for differential-phase reflectometry in QUEST

    SciTech Connect

    Idei, H. Hanada, K.; Zushi, H.; Nagata, K.; Mishra, K.; Itado, T.; Akimoto, R.; Yamamoto, M. K.

    2014-11-15

    A Phased Array Antenna (PAA) was considered as launching and receiving antennae in reflectometry to attain good directivity in its applied microwave range. A well-focused beam was obtained in a launching antenna application, and differential-phase evolution was properly measured by using a metal reflector plate in the proof-of-principle experiment at low power test facilities. Differential-phase evolution was also evaluated by using the PAA in the Q-shu University Experiment with Steady State Spherical Tokamak (QUEST). A beam-forming technique was applied in receiving phased-array antenna measurements. In the QUEST device that should be considered as a large oversized cavity, standing wave effect was significantly observed with perturbed phase evolution. A new approach using derivative of measured field on propagating wavenumber was proposed to eliminate the standing wave effect.

  5. Optically controlled phased-array technology for space communication systems

    NASA Technical Reports Server (NTRS)

    Kunath, Richard R.; Bhasin, Kul B.

    1988-01-01

    Using MMICs in phased-array applications above 20 GHz requires complex RF and control signal distribution systems. Conventional waveguide, coaxial cable, and microstrip methods are undesirable due to their high weight, high loss, limited mechanical flexibility and large volume. An attractive alternative to these transmission media, for RF and control signal distribution in MMIC phased-array antennas, is optical fiber. Presented are potential system architectures and their associated characteristics. The status of high frequency opto-electronic components needed to realize the potential system architectures is also discussed. It is concluded that an optical fiber network will reduce weight and complexity, and increase reliability and performance, but may require higher power.

  6. High-frequency ultrasound annular array imaging. Part II: digital beamformer design and imaging.

    PubMed

    Hu, Chang-Hong; Snook, Kevin A; Cao, Pei-Jie; Shung, K Kirk

    2006-02-01

    This is the second part of a two-paper series reporting a recent effort in the development of a high-frequency annular array ultrasound imaging system. In this paper an imaging system composed of a six-element, 43 MHz annular array transducer, a six-channel analog front-end, a field programmable gate array (FPGA)-based beamformer, and a digital signal processor (DSP) microprocessor-based scan converter will be described. A computer is used as the interface for image display. The beamformer that applies delays to the echoes for each channel is implemented with the strategy of combining the coarse and fine delays. The coarse delays that are integer multiples of the clock periods are achieved by using a first-in-first-out (FIFO) structure, and the fine delays are obtained with a fractional delay (FD) filter. Using this principle, dynamic receiving focusing is achieved. The image from a wire phantom obtained with the imaging system was compared to that from a prototype ultrasonic backscatter microscope with a 45 MHz single-element transducer. The improved lateral resolution and depth of field from the wire phantom image were observed. Images from an excised rabbit eye sample also were obtained, and fine anatomical structures were discerned.

  7. Three-Dimensional Transcranial Ultrasound Imaging of Microbubble Clouds Using a Sparse Hemispherical Array

    PubMed Central

    O'Reilly, Meaghan A.; Jones, Ryan M.; Hynynen, Kullervo

    2014-01-01

    There is an increasing interest in bubble-mediated focused ultrasound (FUS) interventions in the brain. However, current technology lacks the ability to spatially monitor the interaction of the microbubbles with the applied acoustic field, something which is critical for safe clinical translation of these treatments. Passive acoustic mapping could offer a means for spatially monitoring microbubble emissions that relate to bubble activity and associated bioeffects. In this study a hemispherical receiver array was integrated within an existing transcranial therapy array to create a device capable of both delivering therapy and monitoring the process via passive imaging of bubble clouds. A 128-element receiver array was constructed and characterized for varying bubble concentrations and source spacings. Initial in vivo feasibility testing was performed. The system was found to be capable of monitoring bubble emissions down to single bubble events through an ex vivo human skull. The lateral resolution of the system was found to be between 1.25-2 mm and the axial resolution between 2-3.5 mm, comparable to the resolution of MRI-based temperature monitoring during thermal FUS treatments in the brain. The results of initial in vivo experiments show that bubble activity can be mapped starting at pressure levels below the threshold for Blood-Brain barrier disruption. This study presents a feasible solution for imaging bubble activity during cavitation-mediated FUS treatments in the brain. PMID:24658252

  8. Phase-locked laser array through global antenna mutual coupling

    SciTech Connect

    Kao, Tsung -Yu; Reno, John L.; Hu, Qing

    2016-01-01

    Here, phase locking of an array of lasers is a highly effective way in beam shaping, to increase the output power, and to reduce lasing threshold. In this work, we present a novel phase-locking mechanism based on "antenna mutual coupling" wherein laser elements interact through far-field radiations with definite phase relations. This allows long-range global coupling among array elements to achieve robust 2-dimensional phase-locked laser array. The new scheme is ideal for lasers with deep sub-wavelength confined cavity such as nanolasers, where the divergent beam pattern could be used to form strong coupling among elements in the array. We experimentally demonstrated such a scheme using sub-wavelength short-cavity surface-emitting lasers at terahertz frequency. More than 37 laser elements are phase-locked to each other, delivering up to 6.5 mW single-mode radiations at ~3 terahertz, with maximum 450-mW/A slope efficiency and near diffraction limit beam divergence.

  9. Phase-locked laser array through global antenna mutual coupling

    DOE PAGES

    Kao, Tsung -Yu; Reno, John L.; Hu, Qing

    2016-01-01

    Here, phase locking of an array of lasers is a highly effective way in beam shaping, to increase the output power, and to reduce lasing threshold. In this work, we present a novel phase-locking mechanism based on "antenna mutual coupling" wherein laser elements interact through far-field radiations with definite phase relations. This allows long-range global coupling among array elements to achieve robust 2-dimensional phase-locked laser array. The new scheme is ideal for lasers with deep sub-wavelength confined cavity such as nanolasers, where the divergent beam pattern could be used to form strong coupling among elements in the array. We experimentallymore » demonstrated such a scheme using sub-wavelength short-cavity surface-emitting lasers at terahertz frequency. More than 37 laser elements are phase-locked to each other, delivering up to 6.5 mW single-mode radiations at ~3 terahertz, with maximum 450-mW/A slope efficiency and near diffraction limit beam divergence.« less

  10. Phased-array sources based on nonlinear metamaterial nanocavities

    DOE PAGES

    Wolf, Omri; Campione, Salvatore; Benz, Alexander; ...

    2015-07-01

    Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization.more » As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (~5 μm): a beam splitter and a polarizing beam splitter. As a result, proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum.« less

  11. Phased-array sources based on nonlinear metamaterial nanocavities

    PubMed Central

    Wolf, Omri; Campione, Salvatore; Benz, Alexander; Ravikumar, Arvind P.; Liu, Sheng; Luk, Ting S.; Kadlec, Emil A.; Shaner, Eric A.; Klem, John F.; Sinclair, Michael B.; Brener, Igal

    2015-01-01

    Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization. As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (∼5 μm): a beam splitter and a polarizing beam splitter. Proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum. PMID:26126879

  12. Quantitative measurement of ultrasound pressure field by optical phase contrast method and acoustic holography

    NASA Astrophysics Data System (ADS)

    Oyama, Seiji; Yasuda, Jun; Hanayama, Hiroki; Yoshizawa, Shin; Umemura, Shin-ichiro

    2016-07-01

    A fast and accurate measurement of an ultrasound field with various exposure sequences is necessary to ensure the efficacy and safety of various ultrasound applications in medicine. The most common method used to measure an ultrasound pressure field, that is, hydrophone scanning, requires a long scanning time and potentially disturbs the field. This may limit the efficiency of developing applications of ultrasound. In this study, an optical phase contrast method enabling fast and noninterfering measurements is proposed. In this method, the modulated phase of light caused by the focused ultrasound pressure field is measured. Then, a computed tomography (CT) algorithm used to quantitatively reconstruct a three-dimensional (3D) pressure field is applied. For a high-intensity focused ultrasound field, a new approach that combines the optical phase contrast method and acoustic holography was attempted. First, the optical measurement of focused ultrasound was rapidly performed over the field near a transducer. Second, the nonlinear propagation of the measured ultrasound was simulated. The result of the new approach agreed well with that of the measurement using a hydrophone and was improved from that of the phase contrast method alone with phase unwrapping.

  13. Phased array receiver development using high performance HEMT MMICs

    NASA Astrophysics Data System (ADS)

    Liu, L.; Jones, W.; Carandang, R.; Lam, W.; Yonaki, J.; Streit, D.; Kasody, R.

    1991-07-01

    A set of HEMT MMICs including LNAs and phase shifters has been developed for an all-HEMT 20 GHz phased array receiver applications. These MMICs use state-of-the-art HEMT devices for low noise figure, innovative design techniques for compactness, and proven wafer processing for high yield. The LNA achieved a noise figure of 2.5 dB with an associated gain of 22 dB. The 3-bit phase shifter achieved 6 to 7.8 dB insertion loss for all states. With their performance and high process yield, these MMIC chips can be inserted into a system to demonstrate the next generation phased array performance.

  14. Detection Performance of a Diffusive Wave Phased Array

    NASA Astrophysics Data System (ADS)

    Morgan, Stephen P.

    2004-04-01

    Diffusive wave phased arrays have been demonstrated to be a sensitive method of detecting inhomogeneities embedded in heavily scattering media. However, the increase in sensitivity is coupled with an increase in noise, so that the optimum performance may not be obtained when the sources are modulated in antiphase. The performance of a range of configurations in the presence of Gaussian noise is investigated by using probabilistic detection theory. A model of diffusive wave propagation through scattering media is used to demonstrate that the phase performance can be improved by controlling the relative phase difference between the two sources. However, the best performance is obtained by using the amplitude response of a single source system. The major benefit of a phased array system is therefore the rejection of common systematic noise.

  15. A novel serrated columnar phased array ultrasonic transducer

    NASA Astrophysics Data System (ADS)

    Zou, Cheng; Sun, Zhenguo; Cai, Dong; Song, Hongwei; Chen, Qiang

    2016-02-01

    Traditionally, wedges are required to generate transverse waves in a solid specimen and mechanical rotation device is needed for interrogation of a specimen with a hollow bore, such as high speed railway locomotive axles, turbine rotors, etc. In order to eliminate the mechanical rotation process, a novel array pattern of phased array ultrasonic transducers named as serrated columnar phased array ultrasonic transducer (SCPAUT) is designed. The elementary transducers are planar rectangular, located on the outside surface of a cylinder. This layout is aimed to generate electrically rotating transverse waveforms so as to inspect the longitudinal cracks on the outside surface of a specimen which has a hollow bore at the center, such as the high speed railway locomotive axles. The general geometry of the SCPAUT and the inspection system are illustrated. A FEM model and mockup experiment has been carried out. The experiment results are in good agreement with the FEM simulation results.

  16. Removing Background Noise with Phased Array Signal Processing

    NASA Technical Reports Server (NTRS)

    Podboy, Gary; Stephens, David

    2015-01-01

    Preliminary results are presented from a test conducted to determine how well microphone phased array processing software could pull an acoustic signal out of background noise. The array consisted of 24 microphones in an aerodynamic fairing designed to be mounted in-flow. The processing was conducted using Functional Beam forming software developed by Optinav combined with cross spectral matrix subtraction. The test was conducted in the free-jet of the Nozzle Acoustic Test Rig at NASA GRC. The background noise was produced by the interaction of the free-jet flow with the solid surfaces in the flow. The acoustic signals were produced by acoustic drivers. The results show that the phased array processing was able to pull the acoustic signal out of the background noise provided the signal was no more than 20 dB below the background noise level measured using a conventional single microphone equipped with an aerodynamic forebody.

  17. Phased Array Probe Optimization for the Inspection of Titanium Billets

    NASA Astrophysics Data System (ADS)

    Rasselkorde, E.; Cooper, I.; Wallace, P.; Lupien, V.

    2010-02-01

    The manufacturing process of titanium billets can produce multiple sub-surface defects that are particularly difficult to detect during the early stages of production. Failure to detect these defects can lead to subsequent in-service failure. A new and novel automated quality control system is being developed for the inspection of titanium billets destined for use in aerospace applications. The sensors will be deployed by an automated system to minimise the use of manual inspections, which should improve the quality and reliability of these critical inspections early on in the manufacturing process. This paper presents the first part of the work, which is the design and the simulation of the phased array ultrasonic inspection of the billets. A series of phased array transducers were designed to optimise the ultrasonic inspection of a ten inch diameter billet made from Titanium 6Al-4V. A comparison was performed between different probes including a 2D annular sectorial array.

  18. Computation of the radiation characteristics of a generalized phased array

    NASA Technical Reports Server (NTRS)

    Acosta, R. J.

    1986-01-01

    With the advent of monolithic microwave integrated circuit (MMIC) technology, the phased array has become a key component in the design of advanced antenna systems. Array-fed antennas are used extensively in today's multiple beam satellite antennas. A computer program based on a very efficient numerical technique for calculating the radiated power (Romberg integration), directivity, and radiation pattern of a phased array is described. The formulation developed is very general, and takes into account arbitrary element polarization, E- and H-plane element pattern, element location, and complex element excitation. For comparison purposes sample cases have been presented. Excellent agreement has been obtained for all cases. Also included are a user guide and a copy of the computer program.

  19. Ku band phased array in a large angular sector

    NASA Astrophysics Data System (ADS)

    Dubost, G.; Gueho, S.; Beguin, D.

    The feasibility of a microstrip, flat, phased, square array performing at high frequency and exhibiting proper technological behavior is demonstrated. A total of 64 three-bit digital PIN diode phase shifters are used to steer the beam. Sum and difference patterns can be formed for every deflected directivity. Data are presented on the efficiency evaluation for different deflection angles, the highest sidelobe levels, the maximum directivity, and the measured average efficiency.

  20. Inflatable TORUS Solar Array Technology Program. Phase 2.

    DTIC Science & Technology

    1994-01-01

    Phase II Accomplishments ............................ 199, 5.5.2 Lessons Learned from the ITSAT Program ................ 192 5.5.3 Phase III Program...flexible solar array blanket consists of thin crystalline silicon solar cells, a foldable Kapton® substrate, associated wiring and assembly fittings. This...film is used to hold the pressure when inflating by increasing the tear resistance; otherwise the soft foldable aluminum would tear very easily

  1. Infinite Phased Array of Microstrip Dipoles in Two Layers

    DTIC Science & Technology

    1989-01-01

    Green’s function appropriate to the two-layer substrate- superstrate structure was used in the formulation of the method of moMents - (continued on back) 20...analysis is presented for an infinite phased array of microstrip dipoles embedded within a two layer substrate structure (sub- strate- superstrate ...characterization of input impedance as a function of phase scan angle. Results for several sub- strate- superstrate structures illustrate the utility of the single

  2. Realtime photoacoustic microscopy in vivo with a 30-MHz ultrasound array transducer.

    PubMed

    Zemp, Roger J; Song, Liang; Bitton, Rachel; Shung, K Kirk; Wang, Lihong V

    2008-05-26

    We present a novel high-frequency photoacoustic microscopy system capable of imaging the microvasculature of living subjects in realtime to depths of a few mm. The system consists of a high-repetition-rate Q-switched pump laser, a tunable dye laser, a 30-MHz linear ultrasound array transducer, a multichannel high-frequency data acquisition system, and a shared-RAM multi-core-processor computer. Data acquisition, beamforming, scan conversion, and display are implemented in realtime at 50 frames per second. Clearly resolvable images of 6-microm-diameter carbon fibers are experimentally demonstrated at 80 microm separation distances. Realtime imaging performance is demonstrated on phantoms and in vivo with absorbing structures identified to depths of 2.5-3 mm. This work represents the first high-frequency realtime photoacoustic imaging system to our knowledge.

  3. Ultrasound-array-based real-time photoacoustic microscopy of human pulsatile dynamics in vivo

    NASA Astrophysics Data System (ADS)

    Song, Liang; Maslov, Konstantin; Shung, K. Kirk; Wang, Lihong V.

    2010-03-01

    With a refined ultrasound-array-based real-time photoacoustic microscopy (UA-PAM) system, we demonstrate the feasibility of noninvasive in vivo imaging of human pulsatile dynamics. The system, capable of real-time B-scan imaging at 50 Hz and high-speed 3-D imaging, is validated by imaging the subcutaneous microvasculature in rats and humans. After the validation, a human artery around the palm-wrist area is imaged, and its pulsatile dynamics, including the arterial pulsatile motion and changes in hemoglobin concentration, is monitored with 20-ms B-scan imaging temporal resolution. To our knowledge, this is the first demonstration of real-time photoacoustic imaging of human physiological dynamics. Our results show that UA-PAM can potentially enable many new possibilities for studying functional and physiological dynamics in both preclinical and clinical imaging settings.

  4. Phased arrays. Citations from the NTIS data base

    NASA Astrophysics Data System (ADS)

    Reed, W. E.

    1980-04-01

    The design, performance, radiation patterns, and applications of phased arrays are presented in these Federally-sponsored research reports. Applications include communications, radar, optical, spacecraft, and navigational aids. This updated bibliography contains 244 abstracts, 44 of which are new entries to the previous edition.

  5. Electro-optical processing of phased-array antenna data

    NASA Technical Reports Server (NTRS)

    Casasent, D.; Casasayas, F.

    1975-01-01

    An on-line two-dimensional optical processor has been used to process simulated linear and planar phased-array radar data off-line but at real-time data rates. The input transducer is an electron-beam-addressed KD2PO4 light valve.

  6. Coordinated Radar Resource Management for Networked Phased Array Radars

    DTIC Science & Technology

    2014-12-01

    Research and Development Canada Ottawa, Canada K1A 0Z4 Email: Peter.Moo@drdc-rddc.gc.ca Abstract A phased array radar has the ability to rapidly and...search and Development Canada (DRDC) Ottawa to analyse the performance of radar resource management techniques for naval radars operating in a littoral

  7. From Vision to Reality: 50 Years of Phased Array Development

    DTIC Science & Technology

    2016-09-30

    an exciting year on 4 October when the engineers and scientists of the Soviet Union launched the first artificial earth satellite. The “Space Age...reliably and in complete amplitude and phase coherence an “impossible dream .” The cost, complexity, and reliability of such arrays were substantial

  8. Weak-signal Phase Calibration Strategies for Large DSN Arrays

    NASA Technical Reports Server (NTRS)

    Jones, Dayton L.

    2005-01-01

    The NASA Deep Space Network (DSN) is studying arrays of large numbers of small, mass-produced radio antennas as a cost-effective way to increase downlink sensitivity and data rates for future missions. An important issue for the operation of large arrays is the accuracy with which signals from hundreds of small antennas can be combined. This is particularly true at Ka band (32 GHz) where atmospheric phase variations can be large and rapidly changing. A number of algorithms exist to correct the phases of signals from individual antennas in the case where a spacecraft signal provides a useful signal-to-noise ratio (SNR) on time scales shorter than the atmospheric coherence time. However, for very weak spacecraft signals it will be necessary to rely on background natural radio sources to maintain array phasing. Very weak signals could result from a spacecraft emergency or by design, such as direct-to-Earth data transmissions from distant planetary atmospheric or surface probes using only low gain antennas. This paper considers the parameter space where external real-time phase calibration will be necessary, and what this requires in terms of array configuration and signal processing. The inherent limitations of this technique are also discussed.

  9. Noise correlations and SNR in phased-array MRS.

    PubMed

    Martini, N; Santarelli, M F; Giovannetti, G; Milanesi, M; De Marchi, D; Positano, V; Landini, L

    2010-01-01

    The acquisition of magnetic resonance spectroscopy (MRS) signals by multiple receiver coils can improve the signal-to-noise ratio (SNR) or alternatively can reduce the scan time maintaining a reliable SNR. However, using phased array coils in MRS studies requires efficient data processing and data combination techniques in order to exploit the sensitivity improvement of the phased array coil acquisition method. This paper describes a novel method for the combination of MRS signals acquired by phased array coils, even in presence of correlated noise between the acquisition channels. In fact, although it has been shown that electric and magnetic coupling mechanisms produce correlated noise in the coils, previous algorithms developed for MRS data combination have ignored this effect. The proposed approach takes advantage of a noise decorrelation stage to maximize the SNR of the combined spectra. In particular Principal Component Analysis (PCA) was exploited to project the acquired spectra in a subspace where the noise vectors are orthogonal. In this subspace the SNR weighting method will provide the optimal overall SNR. Performance evaluation of the proposed method is carried out on simulated (1)H-MRS signals and experimental results are obtained on phantom (1)H-MR spectra using a commercially available 8-element phased array coil. Noise correlations between elements were generally low due to the optimal coil design, leading to a fair SNR gain (about 0.5%) in the center of the field of view (FOV). A greater SNR improvement was found in the peripheral FOV regions.

  10. NASA Adaptive Multibeam Phased Array (AMPA): An application study

    NASA Technical Reports Server (NTRS)

    Mittra, R.; Lee, S. W.; Gee, W.

    1982-01-01

    The proposed orbital geometry for the adaptive multibeam phased array (AMPA) communication system is reviewed and some of the system's capabilities and preliminary specifications are highlighted. Typical AMPA user link models and calculations are presented, the principal AMPA features are described, and the implementation of the system is demonstrated. System tradeoffs and requirements are discussed. Recommendations are included.

  11. Looking Below the Surface with Ultrasonic Phased Array

    SciTech Connect

    Cinson, Anthony D.; Crawford, Susan L.

    2010-10-01

    This article is a brief tutorial on the benefits of volumetric ultrasonic phased array line scanning. The article describes the need, the approach, and the methods/practices used to analyze the data for flaw detection and characterization in the nuclear power plant component arena.

  12. MMIC devices for active phased array antennas

    NASA Technical Reports Server (NTRS)

    Mittra, R.

    1984-01-01

    The study of printed circuit discontinuities is necessary in order to design, for example, transitions between rectangular waveguides and printed circuits. New developments with respect to the analytical approaches to this problem are discussed. A summary of the progress in the experimental approach is presented. The accurate solution for the modes in various millimeter-wave waveguides is essential in the analysis of many integrated circuit components, such as filters and impedance transformers. Problems associated with the numerical computation of these modes in two frequently used waveguide forms, namely, the finline and microstrip, are presented. The spectral domain method of formulation, with a moment method solution, is considered. This approach can be readily extended to analyze an arbitrary configuration of dielectric and metallized regions in a shielded enclosure. Galerkin's method is used, where the testing and basic functions are the same. It is shown that the mode functions, or eigenfunctions, are more sensitive to errors than the phase constants, or eigenvalues. The approximate mode functions do not satisfy the orthogonality relationship well, resulting in difficulties when these modal solutions are used to form an approximate Green's function or are used in a mode matching analysis.

  13. SUPER-RESOLUTION ULTRASOUND TOMOGRAPHY: A PRELIMINARY STUDY WITH A RING ARRAY

    SciTech Connect

    HUANG, LIANJIE; SIMONETTI, FRANCESCO; DURIC, NEBOJSA; RAMA, OLSI

    2007-01-18

    Ultrasound tomography attempts to retrieve the structure of an objective by exploiting the interaction of acoustic waves with the object. A fundamental limit of ultrasound tomography is that features cannot be resolved if they are spaced less than {lambda}/2 apart, where {lambda} is wavelength of the probing wave, regardless of the degree of accuracy of the measurements. Therefore, since the attenuation of the probing wave with propagation distance increases as {lambda} decreases, resolution has to be traded against imaging depth. Recently, it has been shown that the {lambda}/2 limit is a consequence of the Born approximation (implicit in the imaging algorithms currently employed) which neglects the distortion of the probing wavefield as it travels through the medium to be imaged. On the other hand, such a distortion, which is due to the multiple scattering phenomenon, can encode unlimited resolution in the radiating component of the scattered field. Previously, a resolution better than {lambda}/3 has been reported in these proceedings [F. Simonetti, pp. 126 (2006)] in the case of elastic wave probing. In this paper, they demonstrate experimentally a resolution better than {lambda}/4 for objects immersed in a water bth probed by means of a ring array which excites and detects pressure waves in a full view configuration.

  14. Nonlinear contrast imaging with an array-based micro-ultrasound system.

    PubMed

    Needles, A; Arditi, M; Rognin, N G; Mehi, J; Coulthard, T; Bilan-Tracey, C; Gaud, E; Frinking, P; Hirson, D; Foster, F S

    2010-12-01

    The main goal of this study was to determine the optimal strategy for a real-time nonlinear contrast mode for small-animal imaging at high frequencies, on a new array-based micro-ultrasound system. Previously reported contrast imaging at frequencies above 15 MHz has primarily relied on subtraction schemes involving B-mode image data. These approaches provide insufficient contrast to tissue ratios under many imaging conditions. In this work, pulse inversion, amplitude modulation and combinations of these were systematically investigated for the detection of nonlinear fundamental and subharmonic signal components to maximize contrast-to-tissue ratio (CTR) in the 18-24 MHz range. From in vitro and in vivo measurements, nonlinear fundamental detection with amplitude modulation provided optimal results, allowing an improvement in CTR of 13 dB compared with fundamental imaging. Based on this detection scheme, in vivo parametric images of murine kidneys were generated using sequences of nonlinear contrast images after intravenous bolus injections of microbubble suspensions. Initial parametric images of peak enhancement (PE), wash-in rate (WiR) and rise time (RT) are presented. The parametric images are indicative of blood perfusion kinetics, which, in the context of preclinical imaging with small animals, are anticipated to provide valuable insights into the progression of human disease models, where blood perfusion plays a critical role in either the diagnosis or treatment of the disease. Copyright © 2010 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  15. In vivo imaging of inducible tyrosinase gene expression with an ultrasound array-based photoacoustic system

    NASA Astrophysics Data System (ADS)

    Harrison, Tyler; Paproski, Robert J.; Zemp, Roger J.

    2012-02-01

    Tyrosinase, a key enzyme in the production of melanin, has shown promise as a reporter of genetic activity. While green fluorescent protein has been used extensively in this capacity, it is limited in its ability to provide information deep in tissue at a reasonable resolution. As melanin is a strong absorber of light, it is possible to image gene expression using tyrosinase with photoacoustic imaging technologies, resulting in excellent resolutions at multiple-centimeter depths. While our previous work has focused on creating and imaging MCF-7 cells with doxycycline-controlled tyrosinase expression, we have now established the viability of these cells in a murine model. Using an array-based photoacoustic imaging system with 5 MHz center frequency, we capture interleaved ultrasound and photoacoustic images of tyrosinase-expressing MCF-7 tumors both in a tissue mimicking phantom, and in vivo. Images of both the tyrosinase-expressing tumor and a control tumor are presented as both coregistered ultrasound-photoacoustic B-scan images and 3-dimensional photoacoustic volumes created by mechanically scanning the transducer. We find that the tyrosinase-expressing tumor is visible with a signal level 12dB greater than that of the control tumor in vivo. Phantom studies with excised tumors show that the tyrosinase-expressing tumor is visible at depths in excess of 2cm, and have suggested that our imaging system is sensitive to a transfection rate of less than 1%.

  16. VHF-induced thermoacoustic imaging of fresh human prostates using a clinical ultrasound transducer array

    NASA Astrophysics Data System (ADS)

    Patch, S. K.; See, W. A.

    2016-03-01

    The purpose of this work was to demonstrate that a clinical ultrasound transducer array can practically detect thermoacoustic pulses induced by irradiation by very high frequency (VHF) electromagnetic energy. This is an important step because thermoacoustic signal strength is directly proportional to the specific absorption rate (SAR), which is lower in the VHF regime than in microwave or optical regimes. A 96-channel transducer array (P4-1) providing 3 cm coverage was incorporated into a benchtop thermoacoustic imaging system for imaging fresh surgical specimens. Thermoacoustic signal was generated by 700 ns irradiation pulses with 11 kV/m electric field strength and 108 MHz carrier frequency. To improve SNR 1024 pulses were averaged at a 250 Hz repetition rate. Two sets of sinograms were acquired, separated by a 2 cm translation along the tomographic axis and reconstructed over a 6 x 6 x 5 cm3 volume. Contrast and in-plane resolution were measured by imaging a homogeneous cylindrical phantom and an 80- micron wire designed to highlight E-field polarization effects. FWHM of the in-plane point spread function varied from 250 microns to 1.1 mm, depending upon transducer used and phantom orientation relative to the electric field. Several fresh human prostates were imaged immediately after surgery. Rudimentary comparison to histology was performed and volumetric reconstruction of the multi-channel P4-1 data visualizes anatomic features that are rarely seen in ultrasound, CT, or MRI. The single element transducer provided superior image contrast, but with inferior resolution.

  17. Real-time 3-d intracranial ultrasound with an endoscopic matrix array transducer.

    PubMed

    Light, Edward D; Mukundan, Srinivasan; Wolf, Patrick D; Smith, Stephen W

    2007-08-01

    A transducer originally designed for transesophageal echocardiography (TEE) was adapted for real-time volumetric endoscopic imaging of the brain. The transducer consists of a 36 x 36 array with an interelement spacing of 0.18 mm. There are 504 transmitting and 252 receive channels placed in a regular pattern in the array. The operating frequency is 4.5 MHz with a -6 dB bandwidth of 30%. The transducer is fabricated on a 10-layer flexible circuit from Microconnex (Snoqualmie, WA, USA). The purpose of this study is to evaluate the clinical feasibility of real-time 3-D intracranial ultrasound with this device. The Volumetrics Medical Imaging (Durham, NC, USA) 3-D scanner was used to obtain images in a canine model. A transcalvarial acoustic window was created under general anesthesia in the animal laboratory by placing a 10-mm burr hole in the high parietal calvarium of a 50-kg canine subject. The burr-hole was placed in a left parasagittal location to avoid the sagittal sinus, and the transducer was placed against the intact dura mater for ultrasound imaging. Images of the lateral ventricles were produced, including real-time 3-D guidance of a needle puncture of one ventricle. In a second canine subject, contrast-enhanced 3-D Doppler color flow images were made of the cerebral vessels including the complete Circle of Willis. Clinical applications may include real-time 3-D guidance of cerebrospinal fluid extraction from the lateral ventricles and bedside evaluation of critically ill patients where computed tomography and magnetic resonance imaging techniques are unavailable.

  18. Quantitative shear wave optical coherence elastography (SW-OCE) with acoustic radiation force impulses (ARFI) induced by phase array transducer

    NASA Astrophysics Data System (ADS)

    Song, Shaozhen; Le, Nhan Minh; Wang, Ruikang K.; Huang, Zhihong

    2015-03-01

    Shear Wave Optical Coherence Elastography (SW-OCE) uses the speed of propagating shear waves to provide a quantitative measurement of localized shear modulus, making it a valuable technique for the elasticity characterization of tissues such as skin and ocular tissue. One of the main challenges in shear wave elastography is to induce a reliable source of shear wave; most of nowadays techniques use external vibrators which have several drawbacks such as limited wave propagation range and/or difficulties in non-invasive scans requiring precisions, accuracy. Thus, we propose linear phase array ultrasound transducer as a remote wave source, combined with the high-speed, 47,000-frame-per-second Shear-wave visualization provided by phase-sensitive OCT. In this study, we observed for the first time shear waves induced by a 128 element linear array ultrasound imaging transducer, while the ultrasound and OCT images (within the OCE detection range) were triggered simultaneously. Acoustic radiation force impulses are induced by emitting 10 MHz tone-bursts of sub-millisecond durations (between 50 μm - 100 μm). Ultrasound beam steering is achieved by programming appropriate phase delay, covering a lateral range of 10 mm and full OCT axial (depth) range in the imaging sample. Tissue-mimicking phantoms with agarose concentration of 0.5% and 1% was used in the SW-OCE measurements as the only imaging samples. The results show extensive improvements over the range of SW-OCE elasticity map; such improvements can also be seen over shear wave velocities in softer and stiffer phantoms, as well as determining the boundary of multiple inclusions with different stiffness. This approach opens up the feasibility to combine medical ultrasound imaging and SW-OCE for high-resolution localized quantitative measurement of tissue biomechanical property.

  19. Linear array transducer for high-power airborne ultrasound using flextensional structure

    NASA Astrophysics Data System (ADS)

    Yamamoto, Jun; Mizuno, Yosuke; Tabaru, Marie; Nakamura, Kentaro

    2015-07-01

    To change the direction of ultrasonic irradiation without moving a transducer, a high-power airborne ultrasonic transducer for a one-dimensional phased array system was designed and tested. A flextensional element transducer with higher-mode bending vibration was fabricated to obtain a high vibration amplitude over a wide aperture, where a phase-compensating stepped structure was employed. The width of the main lobe at half maximum and the sidelobe level were measured to be 14.3 deg and 0.78, respectively. The maximal sound pressure of 132 dB (0 dB re. 0.02 mPa) was obtained under the applied voltage of 4.0 V. The beam steering characteristics of a phased array using eight elements were compared with the simple theory.

  20. Simultaneous Transmit and Receive Performance of an 8-Channel Digital Phased Array

    DTIC Science & Technology

    2017-01-16

    Simultaneous transmit and receive with digital phased arrays,” in IEEE International Symposium on Phased Array Systems and Technology , Oct. 2016, pp. 1–6. ...Simultaneous Transmit and Receive Performance of an 8-channel Digital Phased Array Jonathan P. Doane, Kenneth E. Kolodziej, Bradley T. Perry MIT...high isolation between adjacent transmitting and receiving sub-arrays in a digital phased array without analog cancellers or other complex front-end

  1. Adaptive phase calibration of a microphone array for acoustic holography.

    PubMed

    Teal, Paul D; Poletti, Mark A

    2010-04-01

    Previous work has indicated that a limitation on the performance of a circular microphone array for holographic sound field recording at low frequencies is phase mismatch between the microphones in the array. At low frequencies these variations become more significant than at mid-range and high frequencies because the high order phase mode responses at low frequencies are lower in amplitude. This paper demonstrates the feasibility of a "self-calibration" method. The basis of the calibration is to estimate the location of one or more wide-band sources using mid-range frequencies and to use this source location information to perform correction to the array at low frequencies. In its simplest form the calibration must be performed in an anechoic environment, since multipath effects at widely differing frequencies are uncorrelated. The approach is first demonstrated in such an environment using recordings from an array of high quality microphones. The technique is then extended to an adaptive calibration that can be used in an environment that is somewhat reverberant. The validity of the adaptive approach is demonstrated using recordings from an array of inexpensive microphones.

  2. High-power phase-locked arrays of antiguides

    NASA Astrophysics Data System (ADS)

    Botez, D.

    1991-12-01

    Phase-locked arrays of antiguides are a unique class of (monolithic) coherent diode lasers in that they provide both strong overall interelement coupling as well as strong optical-mode confinement. The leaky-wave characteristics of antiguides allow for a resonant condition; that is, when the interelement regions are odd integer numbers of the leaky-wave (lateral) half wavelength all elements equally couple to each other creating so called parallel coupling. By contrast, for the vast majority of coherent arrays published to date interelement coupling is of the nearest-neighbor type, so called series coupling, which gives weak coherence and poor intermodal discrimination. Parallel-coupled arrays of antiguides are called resonant-optical-waveguide (ROW) arrays. ROW devices posses such desirable properties as: full coherence, uniform intensity profile, and large intermodal discrimination. Thus, high coherent powers can be achieved without active phase control. The theory of operation for ROW arrays will be outlined. Experimental results include diffraction-limited-operation from both 20- and 40-element devices to high drive levels (10×threshold) and powers (0.5-1.5 W). CW diffraction-limited operation has been achieved to 0.5 W, while in pulsed operation up to 2 W is obtained in a nearly diffraction-limited beam. Devices can be driven to 5 W with beamwidths 3×diffraction limit.

  3. A 220 GHz reflection-type phased array concept study

    NASA Astrophysics Data System (ADS)

    Hedden, Abigail S.; Dietlein, Charles R.; Wikner, David A.

    2011-05-01

    The goal of this project is to enable light-weight, durable, and portable systems capable of performing standoff detection of person-borne improvised explosive devices (PB-IEDs) through the development of millimeter-wave reflection-type phased arrays. Electronic beam steering eliminates the need for complex mechanical scanners that are commonly implemented with millimeter-wave imaging systems and would reduce overall system size and weight. We present a concept study of a 220 GHz reflection-type phased array for the purpose of performing beam scanning of a confocal reflector system. Requirements for effective imaging of the desired target region are established, including spatial resolution, total scan angle, and number of image pixels achievable. We examine the effects of array architecture on beam characteristics as it is scanned off broadside, including Gaussicity and encircled energy. Benchmark requirements are determined and compared with the capabilities of several potential phase shifter technologies, including MEMS-based variable capacitor phase shifters, switches, and varactor diode-based phase shifters.

  4. Ultrasonic Phased Array Inspection of Seeded Titanium Billet

    NASA Astrophysics Data System (ADS)

    Friedl, J. H.; Gray, T. A.; Khandelwal, P.; Dunhill, T.

    2004-02-01

    As part of efforts by Rolls-Royce to evaluate the use of ultrasonic phased arrays for inspection of titanium billets, a series of ultrasonic phased array inspections were performed at the Center for Nondestructive Evaluation (CNDE). The inspections were performed using a sectorial-annular array designed especially for titanium billets by R/D Tech and supplied to Rolls-Royce. The billet test piece is seeded with thirteen yttria disks, each located at successive depths below the outer diameter surface to just past the billet centerline. The phased array inspections employed both fixed-focus and dynamic-depth-focus (DDF) focal laws in conjunction with several depth gating schemes. Aperture and focal parameters were changed as a function of depth when using fixed-focus focal laws. Results include characterization of transducer performance and delay-time correction of imperfections, signal-to-noise measurements for the yttria disks in the billet test piece, and effects of probe misalignment on flaw sensitivity.

  5. Binary-Phase Fourier Gratings for Nonuniform Array Generation

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Crow, Robert W.; Ashley, Paul R.

    2003-01-01

    We describe a design method for a binary-phase Fourier grating that generates an array of spots with nonuniform, user-defined intensities symmetric about the zeroth order. Like the Dammann fanout grating approach, the binary-phase Fourier grating uses only two phase levels in its grating surface profile to generate the final spot array. Unlike the Dammann fanout grating approach, this method allows for the generation of nonuniform, user-defined intensities within the final fanout pattern. Restrictions governing the specification and realization of the array's individual spot intensities are discussed. Design methods used to realize the grating employ both simulated annealing and nonlinear optimization approaches to locate optimal solutions to the grating design problem. The end-use application driving this development operates in the near- to mid-infrared spectrum - allowing for higher resolution in grating specification and fabrication with respect to wavelength than may be available in visible spectrum applications. Fabrication of a grating generating a user-defined nine spot pattern is accomplished in GaAs for the near-infrared. Characterization of the grating is provided through the measurement of individual spot intensities, array uniformity, and overall efficiency. Final measurements are compared to calculated values with a discussion of the results.

  6. Airborne ultrasonic phased arrays using ferroelectrets: a new fabrication approach.

    PubMed

    Ealo, Joao L; Camacho, Jorge J; Fritsch, Carlos

    2009-04-01

    In this work, a novel procedure that considerably simplifies the fabrication process of ferroelectret-based multielement array transducers is proposed and evaluated. Also, the potential of ferroelectrets being used as active material for air-coupled ultrasonic transducer design is demonstrated. The new construction method of multi-element transducers introduces 2 distinctive improvements. First, active ferroelectret material is not discretized into elements, and second, the need of structuring upper and/or lower electrodes in advance of the permanent polarization of the film is removed. The aperture discretization and the mechanical connection are achieved in one step using a through-thickness conductive tape. To validate the procedure, 2 linear array prototypes of 32 elements, with a pitch of 3.43 mm and a wide usable frequency range from 30 to 300 kHz, were built and evaluated using a commercial phased-array system. A low crosstalk among elements, below -30 dB, was measured by interferometry. Likewise, a homogeneous response of the array elements, with a maximum deviation of +/-1.8 dB, was obtained. Acoustic beam steering measurements were accomplished at different deflection angles using a calibrated microphone. The ultrasonic beam parameters, namely, lateral resolution, side lobe level, grating lobes, and focus depth, were congruent with theory. Acoustic images of a single reflector were obtained using one of the array elements as the receiver. Resulting images are also in accordance with numerical simulation, demonstrating the feasibility of using these arrays in pulse-echo mode. The proposed procedure simplifies the manufacturing of multidimensional arrays with arbitrary shape elements and not uniformly distributed. Furthermore, this concept can be extended to nonflat arrays as long as the transducer substrate conforms to a developable surface.

  7. Scan blindness in infinite phased arrays of printed dipoles

    NASA Technical Reports Server (NTRS)

    Pozar, D. M.; Schaubert, D. H.

    1984-01-01

    A comprehensive study of infinite phased arrays of printed dipole antennas is presented, with emphasis on the scan blindness phenomenon. A rigorous and efficient moment method procedure is used to calculate the array impedance versus scan angle. Data are presented for the input reflection coefficient for various element spacings and substrate parameters. A simple theory, based on coupling from Floquet modes to surface wave modes on the substrate, is shown to predict the occurrence of scan blindness. Measurements from a waveguide simulator of a blindness condition confirm the theory.

  8. Parametric wave phase conjugation of nonlinear ultrasound waves

    NASA Astrophysics Data System (ADS)

    Brysev, Andrew; Mikhalevich, Vladislav; Streltsov, Vladimir

    2003-10-01

    Real time acoustic wave phase conjugation (WPC), based on parametric self-consistent physical mechanisms, was realized up to the present time only for the monochromatic waves [A. P. Brysev et al., Phys.-Usp. 41, 793 (1998)]. Here the possibility of WPC of nonmonochromatic ultrasound waves is considered. For simultaneous WPC of the entire series of spectral components generated by nonlinear propagation of the incident wave we propose the use of phonon-plasmon interaction in piezosemiconductors. WPC of nonlinear acoustic waves can be accomplished by modulation of the electron density provided by a sequence of short laser pulses pumping the sample. If the periodicity of the optical pulses is half the period of the fundamental component of the acoustic wave, such wide-band, excitation leads to self-synchronized parametric conjugation of each spectral component in the incident wave. The conjugation efficiency depends sharply on relations between acoustical frequency content, laser pulse duration, and interband relaxation time. It is shown that under certain conditions the time profile of the conjugate wave may be efficiently controlled by varying the duration of the laser pulses. The time profile of the conjugate wave is investigated for some physical conditions of practical interest.

  9. SAR processing with stepped chirps and phased array antennas.

    SciTech Connect

    Doerry, Armin Walter

    2006-09-01

    Wideband radar signals are problematic for phased array antennas. Wideband radar signals can be generated from series or groups of narrow-band signals centered at different frequencies. An equivalent wideband LFM chirp can be assembled from lesser-bandwidth chirp segments in the data processing. The chirp segments can be transmitted as separate narrow-band pulses, each with their own steering phase operation. This overcomes the problematic dilemma of steering wideband chirps with phase shifters alone, that is, without true time-delay elements.

  10. Ultrasound nondestructive evaluation (NDE) imaging with transducer arrays and adaptive processing.

    PubMed

    Li, Minghui; Hayward, Gordon

    2012-01-01

    This paper addresses the challenging problem of ultrasonic non-destructive evaluation (NDE) imaging with adaptive transducer arrays. In NDE applications, most materials like concrete, stainless steel and carbon-reinforced composites used extensively in industries and civil engineering exhibit heterogeneous internal structure. When inspected using ultrasound, the signals from defects are significantly corrupted by the echoes form randomly distributed scatterers, even defects that are much larger than these random reflectors are difficult to detect with the conventional delay-and-sum operation. We propose to apply adaptive beamforming to the received data samples to reduce the interference and clutter noise. Beamforming is to manipulate the array beam pattern by appropriately weighting the per-element delayed data samples prior to summing them. The adaptive weights are computed from the statistical analysis of the data samples. This delay-weight-and-sum process can be explained as applying a lateral spatial filter to the signals across the probe aperture. Simulations show that the clutter noise is reduced by more than 30 dB and the lateral resolution is enhanced simultaneously when adaptive beamforming is applied. In experiments inspecting a steel block with side-drilled holes, good quantitative agreement with simulation results is demonstrated.

  11. Ultrasound Nondestructive Evaluation (NDE) Imaging with Transducer Arrays and Adaptive Processing

    PubMed Central

    Li, Minghui; Hayward, Gordon

    2012-01-01

    This paper addresses the challenging problem of ultrasonic non-destructive evaluation (NDE) imaging with adaptive transducer arrays. In NDE applications, most materials like concrete, stainless steel and carbon-reinforced composites used extensively in industries and civil engineering exhibit heterogeneous internal structure. When inspected using ultrasound, the signals from defects are significantly corrupted by the echoes form randomly distributed scatterers, even defects that are much larger than these random reflectors are difficult to detect with the conventional delay-and-sum operation. We propose to apply adaptive beamforming to the received data samples to reduce the interference and clutter noise. Beamforming is to manipulate the array beam pattern by appropriately weighting the per-element delayed data samples prior to summing them. The adaptive weights are computed from the statistical analysis of the data samples. This delay-weight-and-sum process can be explained as applying a lateral spatial filter to the signals across the probe aperture. Simulations show that the clutter noise is reduced by more than 30 dB and the lateral resolution is enhanced simultaneously when adaptive beamforming is applied. In experiments inspecting a steel block with side-drilled holes, good quantitative agreement with simulation results is demonstrated. PMID:22368457

  12. Imaging with Concave Large-Aperture Therapeutic Ultrasound Arrays Using Conventional Synthetic-Aperture Beamforming

    PubMed Central

    Wan, Yayun; Ebbini, Emad S.

    2009-01-01

    Several dual-mode ultrasound array (DMUA) systems are being investigated for potential use in image-guided surgery. In therapeutic mode, DMUAs generate pulsed or continuous-wave (CW) high-intensity focused ultrasound (HIFU) beams capable of generating localized therapeutic effects within the focal volume. In imaging mode, pulse-echo data can be collected from the DMUA elements to obtain B-mode images or other forms of feedback on the state of the target tissue before, during, and after the application of the therapeutic HIFU beam. Therapeutic and technological constraints give rise to special characteristics of therapeutic arrays. Specifically, DMUAs have concave apertures with low f-number values and are typically coarsely sampled using directive elements. These characteristics necessitate pre- and post-beamforming signal processing of echo data to improve the spatial and contrast resolution and maximize the image uniformity within the imaging field of view (IxFOV). We have recently developed and experimentally validated beamforming algorithms for concave large-aperture DMUAs with directive elements. Experimental validation was performed using a 1 MHz, 64-element, concave spherical aperture with 100 mm radius of curvature. The aperture was sampled in the lateral direction using elongated elements 1−λ×33.3‒ with 1.333‒−λ center-to-center spacing (λ is the wavelength). This resulted in f-number values of 0.8 and 2 in the azimuth and elevation directions, respectively. In this paper, we present a new DMUA design approach based on different sampling of the shared concave aperture to improve image quality while maintaining therapeutic performance. A pulse-wave (PW) simulation model using a modified version of the Field II program is used in this study. The model is used in generating pulse-echo data for synthetic-aperture (SA) beamforming for forming images of a variety of targets, e.g., wire arrays and speckle-generating cyst phantoms. To provide

  13. Imaging with concave large-aperture therapeutic ultrasound arrays using conventional synthetic-aperture beamforming.

    PubMed

    Wan, Yayun; Ebbini, Emad S

    2008-08-01

    Several dual-mode ultrasound array (DMUA) systems are being investigated for potential use in image- guided surgery. In therapeutic mode, DMUAs generate pulsed or continuous-wave (CW) high-intensity focused ultrasound (HIFU) beams capable of generating localized therapeutic effects within the focal volume. In imaging mode, pulse-echo data can be collected from the DMUA elements to obtain B-mode images or other forms of feedback on the state of the target tissue before, during, and after the application of the therapeutic HIFU beam. Therapeutic and technological constraints give rise to special characteristics of therapeutic arrays. Specifically, DMUAs have concave apertures with low f-number values and are typically coarsely sampled using directive elements. These characteristics necessitate pre- and post-beamforming signal processing of echo data to improve the spatial and contrast resolution and maximize the image uniformity within the imaging field of view (IxFOV). We have recently developed and experimentally validated beamforming algorithms for concave large-aperture DMUAs with directive elements. Experimental validation was performed using a 1 MHz, 64-element, concave spherical aperture with 100 mm radius of curvature. The aperture was sampled in the lateral direction using elongated elements 1-lambda x 33.3-lambda with 1.333-lambda center-to-center spacing (lambda is the wavelength). This resulted in f-number values of 0.8 and 2 in the azimuth and elevation directions, respectively. In this paper, we present a new DMUA design approach based on different sampling of the shared concave aperture to improve image quality while maintaining therapeutic performance. A pulse-wave (PW) simulation model using a modified version of the Field II program is used in this study. The model is used in generating pulse-echo data for synthetic-aperture (SA) beamforming for forming images of a variety of targets, e.g., wire arrays and speckle-generating cyst phantoms. To

  14. High-Resolution Ultrasonic Imaging of Dento-Periodontal Tissues Using a Multi-Element Phased Array System.

    PubMed

    Nguyen, Kim-Cuong T; Le, Lawrence H; Kaipatur, Neelambar R; Zheng, Rui; Lou, Edmond H; Major, Paul W

    2016-10-01

    Intraoral ultrasonography uses high-frequency mechanical waves to study dento-periodontium. Besides the advantages of portability and cost-effectiveness, ultrasound technique has no ionizing radiation. Previous studies employed a single transducer or an array of transducer elements, and focused on enamel thickness and distance measurement. This study used a phased array system with a 128-element array transducer to image dento-periodontal tissues. We studied two porcine lower incisors from a 6-month-old piglet using 20-MHz ultrasound. The high-resolution ultrasonographs clearly showed the cross-sectional morphological images of the hard and soft tissues. The investigation used an integration of waveform analysis, travel-time calculation, and wavefield simulation to reveal the nature of the ultrasound data, which makes the study novel. With the assistance of time-distance radio-frequency records, we robustly justified the enamel-dentin interface, dentin-pulp interface, and the cemento-enamel junction. The alveolar crest level, the location of cemento-enamel junction, and the thickness of alveolar crest were measured from the images and compared favorably with those from the cone beam computed tomography with less than 10% difference. This preliminary and fundamental study has reinforced the conclusions from previous studies, that ultrasonography has great potential to become a non-invasive diagnostic imaging tool for quantitative assessment of periodontal structures and better delivery of oral care.

  15. Efficient array beam forming by spatial filtering for ultrasound B-mode imaging

    PubMed Central

    Kim, Kang-Sik; Liu, Jie; Insana, Michael F.

    2009-01-01

    This paper proposes an efficient array beam-forming method using spatial matched filtering (SMF) for ultrasonic imaging. In the proposed method, ultrasonic waves are transmitted from an array subaperture with fixed transmit focus as in conventional array imaging. At receive, radio frequency echo signals from each receive channel are passed through a spatial matched filter that is constructed based on the system transmit-receive spatial impulse response. The filtered echo signals are then summed without time delays. The filter concentrates and spatially registers the echo energy from each element so that the pulse-echo impulse response of the summed output is focused with acceptably low side lobes. Analytical beam pattern analysis and simulation results using a linear array show that this spatial filtering method can improve lateral resolution and contrast-to-noise ratio as compared with conventional dynamic receive focusing (DRF) methods. Experimental results with a linear array are consistent but point out the need to address additional practical issues. Spatial filtering is equivalent to synthetic aperture methods that dynamically focus on both transmit and receive throughout the field of view. In one common example of phase aberrations, the SMF method was degraded to a degree comparable to conventional DRF methods. PMID:16938973

  16. Subharmonic phased array for crack evaluation using surface acoustic wave

    NASA Astrophysics Data System (ADS)

    Ouchi, Akihiro; Sugawara, Azusa; Ohara, Yoshikazu; Yamanaka, Kazushi

    2015-07-01

    To accurately measure closed crack length, we proposed an imaging method using a subharmonic phased array for crack evaluation using surface acoustic waves (SAW SPACE) with water immersion. We applied SAW SPACE to the hole specimen in a fundamental array (FA) image. The hole was imaged with high resolution. Subsequently, SAW SPACE was applied to fatigue crack and stress corrosion crack (SCC) specimens. A fatigue crack was imaged in FA and subharmonic array (SA) images, and the length of this particular fatigue crack measured in the images was almost the same as that measured by optical observation. The SCC was imaged and its length was accurately measured in the SA image, whereas it was underestimated in the FA image and by optical observation. Thus, we demonstrated that SAW SPACE with water immersion is useful for the accurate measurement of closed crack length and for imaging the distribution of open and closed parts of cracks with high resolution.

  17. Photorefractive phased array antenna beam-forming processor

    NASA Astrophysics Data System (ADS)

    Sarto, Anthony W.; Wagner, Kelvin H.; Weverka, Robert T.; Blair, Steven M.; Weaver, Samuel P.

    1996-11-01

    A high bandwidth, large degree-of-freedom photorefractive phased-array antenna beam-forming processor which uses 3D dynamic volume holograms in photorefractive crystals to time integrate the adaptive weights to perform beam steering and jammer-cancellation signal-processing tasks is described. The processor calculates the angle-of-arrival of a desired signal of interest and steers the antenna pattern in the direction of this desired signal by forming a dynamic holographic grating proportional to the correlation between the incoming signal of interest from the antenna array and the temporal waveform of the desired signal. Experimental results of main-beam formation and measured array-functions are presented in holographic index grating and the resulting processor output.

  18. Collective Quantum Phase-Slip Dynamics in Superconducting Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Skacel, Sebastian T.; Voss, Jan N.; Bier, Tobias; Radke, Lucas; Weides, Martin; Rotzinger, Hannes; Mooij, Hans E.; Ustinov, Alexey V.

    2014-03-01

    Superconducting nanowire arrays exhibit quantum phase-slip (QPS) phenomenon if the superconductor has a very high normal-state sheet resistance. We experimentally study QPS effects in arrays of nanowires embedded in a resonant circuit at GHz frequencies. We probe this circuit at ultra-low microwave power, applied flux and mK temperatures. The nanowires are fabricated utilizing aluminium grown in a precisely-controlled oxygen atmosphere. In this way, we aim to control the QPS rate for a given wire width. The wires are defined with conventional electron beam lithography down to a width of 20 nm. We will present the fabrication of the nanowire arrays and first microwave measurements at mK temperatures. Center for Functional Nanostructures, Karlsruhe Institute of Technology, D-76128 Karlsruhe, Germany.

  19. Brazilian Decimetre Array (Phase-1): Initial solar observations

    NASA Astrophysics Data System (ADS)

    Ramesh, R.; Sawant, H. S.; Cecatto, J. R.; Faria, C.; Fernandes, F. C. R.; Kathiravan, C.; Suryanarayana, G. S.

    An East-West one-dimensional radio interferometer array consisting of 5 parabolic dish antennas has been set-up at Cachoeira Paulista, Brazil (Longitude: 45°0'20″W, Latitude: 22°41'19″S) for observations of Sun and some of the strong sidereal sources by the Instituto Nacional de Pesquisas Espaciais (INPE), Brazil. This is Phase-1 of the proposed Brazilian Decimetre Array (BDA) and can be operated at any frequency in the range 1.2-1.7 GHz. The instrument is functional since November 2004 onwards at 1.6 GHz. The angular and temporal resolution at the above frequency range are ˜3' and 100 ms, respectively. We present here the initial solar observations carried out with this array.

  20. Optically addressed ultra-wideband phased antenna array

    NASA Astrophysics Data System (ADS)

    Bai, Jian

    Demands for high data rate and multifunctional apertures from both civilian and military users have motivated development of ultra-wideband (UWB) electrically steered phased arrays. Meanwhile, the need for large contiguous frequency is pushing operation of radio systems into the millimeter-wave (mm-wave) range. Therefore, modern radio systems require UWB performance from VHF to mm-wave. However, traditional electronic systems suffer many challenges that make achieving these requirements difficult. Several examples includes: voltage controlled oscillators (VCO) cannot provide a tunable range of several octaves, distribution of wideband local oscillator signals undergo high loss and dispersion through RF transmission lines, and antennas have very limited bandwidth or bulky sizes. Recently, RF photonics technology has drawn considerable attention because of its advantages over traditional systems, with the capability of offering extreme power efficiency, information capacity, frequency agility, and spatial beam diversity. A hybrid RF photonic communication system utilizing optical links and an RF transducer at the antenna potentially provides ultra-wideband data transmission, i.e., over 100 GHz. A successful implementation of such an optically addressed phased array requires addressing several key challenges. Photonic generation of an RF source with over a seven-octave bandwidth has been demonstrated in the last few years. However, one challenge which still remains is how to convey phased optical signals to downconversion modules and antennas. Therefore, a feed network with phase sweeping capability and low excessive phase noise needs to be developed. Another key challenge is to develop an ultra-wideband array antenna. Modern frontends require antennas to be compact, planar, and low-profile in addition to possessing broad bandwidth, conforming to stringent space, weight, cost, and power constraints. To address these issues, I will study broadband and miniaturization

  1. Phased Arrays of Ground and Airborne Mobile Terminals for Satellite Communications

    NASA Technical Reports Server (NTRS)

    Huang, John

    1996-01-01

    Phased array antenna is beginning to play an important in the arena of mobile/satellite communications. Two examples of mobile terminal phased arrays will be shown. Their technical background, challenges, and cost drivers will be discussed. A possible solution to combat some of the deficiencies of the conventional phased array by exploiting the phased reflectarray technology will be briefly presented.

  2. Chirp-coded excitation imaging with a high-frequency ultrasound annular array.

    PubMed

    Mamou, Jonathan; Ketterling, Jeffrey A; Silverman, Ronald H

    2008-02-01

    High-frequency ultrasound (HFU, > 15 MHz) is an effective means of obtaining fine-resolution images of biological tissues for applications such as opthalmologic, dermatologic, and small animal imaging. HFU has two inherent drawbacks. First, HFU images have a limited depth of field (DOF) because of the short wavelength and the low fixed F-number of conventional HFU transducers. Second, HFU can be used to image only a few millimeters deep into a tissue because attenuation increases with frequency. In this study, a five-element annular array was used in conjunction with a synthetic-focusing algorithm to extend the DOF. The annular array had an aperture of 10 mm, a focal length of 31 mm, and a center frequency of 17 MHz. To increase penetration depth, 8-micros, chirp-coded signals were designed, input into an arbitrary waveform generator, and used to excite each array element. After data acquisition, the received signals were linearly filtered to restore axial resolution and increase the SNR. To compare the chirpcoded imaging method with conventional impulse imaging in terms of resolution, a 25-microm diameter wire was scanned and the -6-dB axial and lateral resolutions were computed at depths ranging from 20.5 to 40.5 mm. The results demonstrated that chirp-coded excitation did not degrade axial or lateral resolution. A tissue-mimicking phantom containing 10-microm glass beads was scanned, and backscattered signals were analyzed to evaluate SNR and penetration depth. Finally, ex vivo ophthalmic images were formed and chirpcoded images showed features that were not visible in conventional impulse images.

  3. Quantum phases in circuit QED with a superconducting qubit array

    PubMed Central

    Zhang, Yuanwei; Yu, Lixian; Liang, J. -Q; Chen, Gang; Jia, Suotang; Nori, Franco

    2014-01-01

    Circuit QED on a chip has become a powerful platform for simulating complex many-body physics. In this report, we realize a Dicke-Ising model with an antiferromagnetic nearest-neighbor spin-spin interaction in circuit QED with a superconducting qubit array. We show that this system exhibits a competition between the collective spin-photon interaction and the antiferromagnetic nearest-neighbor spin-spin interaction, and then predict four quantum phases, including: a paramagnetic normal phase, an antiferromagnetic normal phase, a paramagnetic superradiant phase, and an antiferromagnetic superradiant phase. The antiferromagnetic normal phase and the antiferromagnetic superradiant phase are new phases in many-body quantum optics. In the antiferromagnetic superradiant phase, both the antiferromagnetic and superradiant orders can coexist, and thus the system possesses symmetry. Moreover, we find an unconventional photon signature in this phase. In future experiments, these predicted quantum phases could be distinguished by detecting both the mean-photon number and the magnetization. PMID:24522250

  4. Quantum phases in circuit QED with a superconducting qubit array.

    PubMed

    Zhang, Yuanwei; Yu, Lixian; Liang, J-Q; Chen, Gang; Jia, Suotang; Nori, Franco

    2014-02-13

    Circuit QED on a chip has become a powerful platform for simulating complex many-body physics. In this report, we realize a Dicke-Ising model with an antiferromagnetic nearest-neighbor spin-spin interaction in circuit QED with a superconducting qubit array. We show that this system exhibits a competition between the collective spin-photon interaction and the antiferromagnetic nearest-neighbor spin-spin interaction, and then predict four quantum phases, including: a paramagnetic normal phase, an antiferromagnetic normal phase, a paramagnetic superradiant phase, and an antiferromagnetic superradiant phase. The antiferromagnetic normal phase and the antiferromagnetic superradiant phase are new phases in many-body quantum optics. In the antiferromagnetic superradiant phase, both the antiferromagnetic and superradiant orders can coexist, and thus the system possesses Z(z)₂ ⊗ Z₂ symmetry. Moreover, we find an unconventional photon signature in this phase. In future experiments, these predicted quantum phases could be distinguished by detecting both the mean-photon number and the magnetization.

  5. Variable phase sine wave generator for active phased arrays

    NASA Astrophysics Data System (ADS)

    Waters, W. M.

    1992-09-01

    A waveform generator is provided for generating a high frequency waveform. A pulse generator provides a pulse train at a low frequency. A pulse converter converts the pulse train into an alternatingly positive and negative groups of pulses. A bandpass filter passes the alternatingly positive and negative groups of pulses in a frequency band centered at the high frequency to output the generated waveform at the high frequency. When the groups of pulses are a pair of pulses, a sine wave is output from the bandpass filter. A pulse delay circuit can be used to variably delay the pulse train and thereby cause a phase change in the generated waveform.

  6. AlGaAs phased array laser for optical communications

    NASA Technical Reports Server (NTRS)

    Carlson, N. W.

    1989-01-01

    Phased locked arrays of multiple AlGaAs diode laser emitters were investigated both in edge emitting and surface emitting configurations. CSP edge emitter structures, coupled by either evanescent waves or Y-guides, could not achieve the required powers (greater than or similar to 500 mW) while maintaining a diffraction limited, single lobed output beam. Indeed, although the diffraction limit was achieved in this type of device, it was at low powers and in the double lobed radiation pattern characteristic of out-of-phase coupling. Grating surface emitting (GSE) arrays were, therefore, investigated with more promising results. The incorporation of second order gratings in distribute Bragg reflector (DBR) structures allows surface emission, and can be configured to allow injection locking and lateral coupling to populate 2-D arrays that should be able to reach power levels commensurate with the needs of high performance, free space optical communications levels. Also, a new amplitude modulation scheme was developed for GSE array operation.

  7. Active retrodirective arrays for SPS beam pointing. [phase conjugation

    NASA Technical Reports Server (NTRS)

    Chernoff, R.

    1980-01-01

    The basic requirement of the SPS beam pointing system is that it deliver a certain amount of S-band (lambda = 12.5 cm) power to a 9.6 km diameter receiving rectenna on the ground. The power is transmitted from a 1.0 km diameter antenna array on the SPS, which is, for a rectenna at about plus or minus 40 deg. latitude, some 37.5x10 to the 6th power km distant. At the present time ARA's appear to be the best bet to realize this very stringent beam pointing requirement. An active retrodirective array (ARA) transmits a beam towards the apparent source of an illuminating signal called the pilot. The array produces, not merely reflects, RF power. Retrodirectivity is achieved by retransmitting from each element of the array a signal whose phase is the "conjugate" of that received by the element. Phase conjugate circuits and pointing errors in ARA's are described. Results obtained using a 2-element X-band ARA and an 8-element S-band ARA are included.

  8. The application of taylor weighting, digital phase shifters, and digital attenuators to phased-array antennas.

    SciTech Connect

    Brock, Billy C.

    2008-03-01

    Application of Taylor weighting (taper) to an antenna aperture can achieve low peak sidelobes, but combining the Taylor weighting with quantized attenuators and phase shifters at each radiating element will impact the performance of a phased-array antenna. An examination of array performance is undertaken from the simple point of view of the characteristics of the array factor. Design rules and guidelines for determining the Taylor-weighting parameters, the number of bits required for the digital phase shifter, and the dynamic range and number of bits required for the digital attenuator are developed. For a radar application, when each element is fed directly from a transmit/receive module, the total power radiated by the array will be reduced as a result of the taper. Consequently, the issue of whether to apply the taper on both transmit and receive configurations, or only on the receive configuration is examined with respect to two-way sidelobe performance.

  9. Wake Vortex Detection: Phased Microphone vs. Linear Infrasonic Array

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A.; Zuckerwar, Allan J.; Sullivan, Nicholas T.; Knight, Howard K.

    2014-01-01

    Sensor technologies can make a significant impact on the detection of aircraft-generated vortices in an air space of interest, typically in the approach or departure corridor. Current state-of-the art sensor technologies do not provide three-dimensional measurements needed for an operational system or even for wake vortex modeling to advance the understanding of vortex behavior. Most wake vortex sensor systems used today have been developed only for research applications and lack the reliability needed for continuous operation. The main challenges for the development of an operational sensor system are reliability, all-weather operation, and spatial coverage. Such a sensor has been sought for a period of last forty years. Acoustic sensors were first proposed and tested by National Oceanic and Atmospheric Administration (NOAA) early in 1970s for tracking wake vortices but these acoustic sensors suffered from high levels of ambient noise. Over a period of the last fifteen years, there has been renewed interest in studying noise generated by aircraft wake vortices, both numerically and experimentally. The German Aerospace Center (DLR) was the first to propose the application of a phased microphone array for the investigation of the noise sources of wake vortices. The concept was first demonstrated at Berlins Airport Schoenefeld in 2000. A second test was conducted in Tarbes, France, in 2002, where phased microphone arrays were applied to study the wake vortex noise of an Airbus 340. Similarly, microphone phased arrays and other opto-acoustic microphones were evaluated in a field test at the Denver International Airport in 2003. For the Tarbes and Denver tests, the wake trajectories of phased microphone arrays and lidar were compared as these were installed side by side. Due to a built-in pressure equalization vent these microphones were not suitable for capturing acoustic noise below 20 Hz. Our group at NASA Langley Research Center developed and installed an

  10. In vivo liver tracking with a high volume rate 4D ultrasound scanner and a 2D matrix array probe

    NASA Astrophysics Data System (ADS)

    Lediju Bell, Muyinatu A.; Byram, Brett C.; Harris, Emma J.; Evans, Philip M.; Bamber, Jeffrey C.

    2012-03-01

    The effectiveness of intensity-modulated radiation therapy (IMRT) is compromised by involuntary motion (e.g. respiration, cardiac activity). The feasibility of processing ultrasound echo data to automatically estimate 3D liver motion for real-time IMRT guidance was previously demonstrated, but performance was limited by an acquisition speed of 2 volumes per second due to hardware restrictions of a mechanical linear array probe. Utilizing a 2D matrix array probe with parallel receive beamforming offered increased acquisition speeds and an opportunity to investigate the benefits of higher volume rates. In vivo livers of three volunteers were scanned with and without respiratory motion at volume rates of 24 and 48 Hz, respectively. Respiration was suspended via voluntary breath hold. Correlation-based, phase-sensitive 3D speckle tracking was applied to consecutively acquired volumes of echo data. Volumes were omitted at fixed intervals and 3D speckle tracking was re-applied to study the effect of lower scan rates. Results revealed periodic motion that corresponded with the heart rate or breathing cycle in the absence or presence of respiration, respectively. For cardiac-induced motion, volume rates for adequate tracking ranged from 8 to 12 Hz and was limited by frequency discrepancies between tracking estimates from higher and lower frequency scan rates. Thus, the scan rate of volume data acquired without respiration was limited by the need to sample the frequency induced by the beating heart. In respiratory-dominated motion, volume rate limits ranged from 4 to 12 Hz, interpretable from the root-mean-squared deviation (RMSD) from tracking estimates at 24 Hz. While higher volume rates yielded RMSD values less than 1 mm in most cases, lower volume rates yielded RMSD values of 2-6 mm.

  11. In vivo liver tracking with a high volume rate 4D ultrasound scanner and a 2D matrix array probe.

    PubMed

    Bell, Muyinatu A Lediju; Byram, Brett C; Harris, Emma J; Evans, Philip M; Bamber, Jeffrey C

    2012-03-07

    The effectiveness of intensity-modulated radiation therapy (IMRT) is compromised by involuntary motion (e.g. respiration, cardiac activity). The feasibility of processing ultrasound echo data to automatically estimate 3D liver motion for real-time IMRT guidance was previously demonstrated, but performance was limited by an acquisition speed of 2 volumes per second due to hardware restrictions of a mechanical linear array probe. Utilizing a 2D matrix array probe with parallel receive beamforming offered increased acquisition speeds and an opportunity to investigate the benefits of higher volume rates. In vivo livers of three volunteers were scanned with and without respiratory motion at volume rates of 24 and 48 Hz, respectively. Respiration was suspended via voluntary breath hold. Correlation-based, phase-sensitive 3D speckle tracking was applied to consecutively acquired volumes of echo data. Volumes were omitted at fixed intervals and 3D speckle tracking was re-applied to study the effect of lower scan rates. Results revealed periodic motion that corresponded with the heart rate or breathing cycle in the absence or presence of respiration, respectively. For cardiac-induced motion, volume rates for adequate tracking ranged from 8 to 12 Hz and was limited by frequency discrepancies between tracking estimates from higher and lower frequency scan rates. Thus, the scan rate of volume data acquired without respiration was limited by the need to sample the frequency induced by the beating heart. In respiratory-dominated motion, volume rate limits ranged from 4 to 12 Hz, interpretable from the root-mean-squared deviation (RMSD) from tracking estimates at 24 Hz. While higher volume rates yielded RMSD values less than 1 mm in most cases, lower volume rates yielded RMSD values of 2-6 mm.

  12. Phased array ultrasonic testing of dissimilar metal welds using geometric based referencing delay law technique

    NASA Astrophysics Data System (ADS)

    Han, Taeyoung; Schubert, Frank; Hillmann, Susanne; Meyendorf, Norbert

    2015-03-01

    Phased array ultrasonic testing (PAUT) techniques are widely used for the non-destructive testing (NDT) of austenitic welds to find defects like cracks. However, the propagation of ultrasound waves through the austenitic material is intricate due to its inhomogeneous and anisotropic nature. Such a characteristic leads beam path distorted which causes the signal to be misinterpreted. By employing a reference block which is cutout from the mockup of which the structure is a dissimilar metal weld (DMW), a new method of PAUT named as Referencing Delay Law Technique (RDLT) is introduced. With the RDLT, full matrix capture (FMC) was used for data acquisition. To reconstruct the images, total focusing method (TFM) was used. After the focal laws were calculated, PAUT was then performed. As a result, the flaws are more precisely positioned with significantly increased signal-to-noise ratio (SNR).

  13. Experimental validation of an 8 element EMAT phased array probe for longitudinal wave generation

    NASA Astrophysics Data System (ADS)

    Le Bourdais, Florian; Marchand, Benoit

    2015-03-01

    Sodium cooled Fast Reactors (SFR) use liquid sodium as a coolant. Liquid sodium being opaque, optical techniques cannot be applied to reactor vessel inspection. This makes it necessary to develop alternative ways of assessing the state of the structures immersed in the medium. Ultrasonic pressure waves are well suited for inspection tasks in this environment, especially using pulsed electromagnetic acoustic transducers (EMAT) that generate the ultrasound directly in the liquid sodium. The work carried out at CEA LIST is aimed at developing phased array EMAT probes conditioned for reactor use. The present work focuses on the experimental validation of a newly manufactured 8 element probe which was designed for beam forming imaging in a liquid sodium environment. A parametric study is carried out to determine the optimal setup of the magnetic assembly used in this probe. First laboratory tests on an aluminium block show that the probe has the required beam steering capabilities.

  14. Experimental validation of an 8 element EMAT phased array probe for longitudinal wave generation

    SciTech Connect

    Le Bourdais, Florian Marchand, Benoit

    2015-03-31

    Sodium cooled Fast Reactors (SFR) use liquid sodium as a coolant. Liquid sodium being opaque, optical techniques cannot be applied to reactor vessel inspection. This makes it necessary to develop alternative ways of assessing the state of the structures immersed in the medium. Ultrasonic pressure waves are well suited for inspection tasks in this environment, especially using pulsed electromagnetic acoustic transducers (EMAT) that generate the ultrasound directly in the liquid sodium. The work carried out at CEA LIST is aimed at developing phased array EMAT probes conditioned for reactor use. The present work focuses on the experimental validation of a newly manufactured 8 element probe which was designed for beam forming imaging in a liquid sodium environment. A parametric study is carried out to determine the optimal setup of the magnetic assembly used in this probe. First laboratory tests on an aluminium block show that the probe has the required beam steering capabilities.

  15. Simulation of Temperature Field Induced by 8-Element Phased Array HIFU Transducer with Concave Spherical Surface

    NASA Astrophysics Data System (ADS)

    Sun, Wujun; Zhang, Ping; Zhang, Xiaojing; Jian, Xiqi; Li, Zhihua

    2011-09-01

    Multi-element High Intensity Focused Ultrasound (HIFU) transducers can change their focal lengths and form multi-foci. In this paper the Westervelt formula and Pennes bio-heat transfer equation have been used along, with the Finite Difference Time Domain (FDTD) method, to study the temperature distribution induced by an 8-element phased array HIFU transducer inside the human body. We evaluated the effects of the gap in the arc between two rings, the frequency of excitation function and pre-focal length on the temperature field. For HIFU therapy, skin burns were caused by high frequency, small pre-focal length, or a big gap between two rings. The focal region may be no longer an ellipsoid due to high frequency. In addition, the actual focal length is slightly different from the pre-focal length.

  16. A conceptual design for a microwave active phased array SAR

    NASA Technical Reports Server (NTRS)

    Gilchrist, Brian E.; Stacy, Nicholas J.; Daida, Jason; Vesecky, John F.

    1986-01-01

    The active phased array radar is well known for its assets of rapid electronic beam steering and adaptability to limited degrading influences. In a spaceborne synthetic aperture radar (SAR) application, therefore, it should be possible to provide for rapid beam control in the cross-track (variable incidence angle) and along-track (spot-light mode) directions, as well as allowing for possible relaxation of antenna structural requirements. A design study has been conducted at Stanford University for a conceptual spaceborne C-band SAR application operating in the early to mid-1990's time frame. This study was intended to identify principal design issues, as well as unique features associated with an active phased array antenna SAR. A hypothetical design is used to illustrate these issues. Some of this work should have generic application to space-based communications activities.

  17. Energy efficient two-phase cooling for concentrated photovoltaic arrays

    NASA Astrophysics Data System (ADS)

    Reeser, Alexander Douglas

    Concentrated sunlight focused on the aperture of a photovoltaic solar cell, coupled with high efficiency, triple junction cells can produce much greater power densities than traditional 1 sun photovoltaic cells. However, the large concentration ratios will lead to very high cell temperatures if not efficiently cooled by a thermal management system. Two phase, flow boiling is an attractive cooling option for such CPV arrays. In this work, two phase flow boiling in mini/microchannels and micro pin fin arrays will be explored as a possible CPV cooling technique. The most energy efficient microchannel design is chosen based on a least-material, least-energy analysis. Heat transfer and pressure drop obtained in micro pin fins will be compared to data in the recent literature and new correlations for heat transfer coefficient and pressure drop will be presented. The work concludes with an energy efficiency comparison of micro pin fins with geometrically similar microchannel geometry.

  18. Ultrasonic Phased Array Simulations of Welded Components at NASA

    NASA Technical Reports Server (NTRS)

    Roth, D. J.; Tokars, R. P.; Martin, R. E.; Rauser, R. W.; Aldrin, J. C.

    2009-01-01

    Comprehensive and accurate inspections of welded components have become of increasing importance as NASA develops new hardware such as Ares rocket segments for future exploration missions. Simulation and modeling will play an increasing role in the future for nondestructive evaluation in order to better understand the physics of the inspection process, to prove or disprove the feasibility for an inspection method or inspection scenario, for inspection optimization, for better understanding of experimental results, and for assessment of probability of detection. This study presents simulation and experimental results for an ultrasonic phased array inspection of a critical welded structure important for NASA future exploration vehicles. Keywords: nondestructive evaluation, computational simulation, ultrasonics, weld, modeling, phased array

  19. Monolithic Microwave Integrated Circuit (MMIC) Phased Array Demonstrated With ACTS

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Monolithic Microwave Integrated Circuit (MMIC) arrays developed by the NASA Lewis Research Center and the Air Force Rome Laboratory were demonstrated in aeronautical terminals and in mobile or fixed Earth terminals linked with NASA's Advanced Communications Technology Satellite (ACTS). Four K/Ka-band experimental arrays were demonstrated between May 1994 and May 1995. Each array had GaAs MMIC devices at each radiating element for electronic beam steering and distributed power amplification. The 30-GHz transmit array used in uplinks to ACTS was developed by Lewis and Texas Instruments. The three 20-GHz receive arrays used in downlinks from ACTS were developed in cooperation with the Air Force Rome Laboratory, taking advantage of existing Air Force integrated-circuit, active-phased-array development contracts with the Boeing Company and Lockheed Martin Corporation. Four demonstrations, each related to an application of high interest to both commercial and Department of Defense organizations, were conducted. The location, type of link, and the data rate achieved for each of the applications is shown. In one demonstration-- an aeronautical terminal experiment called AERO-X--a duplex voice link between an aeronautical terminal on the Lewis Learjet and ACTS was achieved. Two others demonstrated duplex voice links (and in one case, interactive video links as well) between ACTS and an Army high-mobility, multipurpose wheeled vehicle (HMMWV, or "humvee"). In the fourth demonstration, the array was on a fixed mount and was electronically steered toward ACTS. Lewis served as project manager for all demonstrations and as overall system integrator. Lewis engineers developed the array system including a controller for open-loop tracking of ACTS during flight and HMMWV motion, as well as a laptop data display and recording system used in all demonstrations. The Jet Propulsion Laboratory supported the AERO-X program, providing elements of the ACTS Mobile Terminal. The successful

  20. Estimating Transmitted-Signal Phase Variations for Uplink Array Antennas

    NASA Technical Reports Server (NTRS)

    Paal, Leslie; Mukai, Ryan; Vilntrotter, Victor; Cornish, Timothy; Lee, Dennis

    2009-01-01

    A method of estimating phase drifts of microwave signals distributed to, and transmitted by, antennas in an array involves the use of the signals themselves as phase references. The method was conceived as part of the solution of the problem of maintaining precise phase calibration required for proper operation of an array of Deep Space Network (DSN) antennas on Earth used for communicating with distant spacecraft at frequencies between 7 and 8 GHz. The method could also be applied to purely terrestrial phased-array radar and other radio antenna array systems. In the DSN application, the electrical lengths (effective signal-propagation path lengths) of the various branches of the system for distributing the transmitted signals to the antennas are not precisely known, and they vary with time. The variations are attributable mostly to thermal expansion and contraction of fiber-optic and electrical signal cables and to a variety of causes associated with aging of signal-handling components. The variations are large enough to introduce large phase drifts at the signal frequency. It is necessary to measure and correct for these phase drifts in order to maintain phase calibration of the antennas. A prior method of measuring phase drifts involves the use of reference-frequency signals separate from the transmitted signals. A major impediment to accurate measurement of phase drifts over time by the prior method is the fact that although DSN reference-frequency sources separate from the transmitting signal sources are stable and accurate enough for most DSN purposes, they are not stable enough for use in maintaining phase calibrations, as required, to within a few degrees over times as long as days or possibly even weeks. By eliminating reliance on the reference-frequency subsystem, the present method overcomes this impediment. In a DSN array to which the present method applies (see figure), the microwave signals to be transmitted are generated by exciters in a signal

  1. Simulations of lesion detection using a combined phased array LHMI-technique.

    PubMed

    Heikkilä, Janne; Hynynen, Kullervo

    2008-11-01

    Ultrasound based elasticity imaging techniques have been developed during the past decades. Some of these techniques are based on an internal radiation force stimulation in which a transient or dynamic radiation force is produced by using a single or dual-frequency sonication. In addition, sonication and data acquisition can be implemented using combined or separate transducers. In this simulation study of lesion detection using localized harmonic motion imaging (LHMI), we used a combined phased array designed for simultaneous thermal ablation and lesion detection. In the sonication mode, a focused single-frequency amplitude-modulated sonication is used to induce harmonic motion and in the tracking mode, some of the array elements are used for pulse-echo tracking of the induced displacements. The results showed that the size of the lesion affected the induced displacement around the sonication point. The displacement tracking simulations demonstrated that these changes in the displacement distributions can be detected using only a few of the array elements in the tracking mode but the exact size of the lesion can not be detected accurately. The simulations also showed that two lesions having the radius of 2.5mm can be distinguished if distance between these lesions is at least 2.5mm.

  2. Scattering of the field of a multi-element phased array by human ribs

    NASA Astrophysics Data System (ADS)

    Gélat, P.; ter Haar, G.; Saffari, N.

    2012-03-01

    The efficacy of high intensity focused ultrasound (HIFU) for the non-invasive treatment of cancer has been demonstrated for a range of different cancers including those of the liver, kidney, prostate and breast. As a non-invasive focused therapy, HIFU offers considerable advantages over other techniques such as chemotherapy and surgical resection, in terms of invasiveness and risk of harmful side effects. Despite its advantages, however, there are a number of significant challenges currently hindering its widespread clinical application. One of these challenges is the need to transmit sufficient energy through the ribcage to induce tissue necrosis at the required foci whilst minimising the formation of side lobes. Multielement random arrays are currently showing great promise in overcoming the limitations of single-element transducers. Nevertheless, successfully treating a patient for liver tumours requires a thorough understanding of the way in which the ultrasonic pressure field from a HIFU array is scattered by the ribcage. A mesh of quadratic pressure patches was generated using CT scan data for ribs nine to twelve on the right side. A boundary element approach based on a Generalised Minimal Residual (GMRES) implementation of the Burton-Miller formulation was used, in conjunction with phase conjugation techniques to focus the field of a 256-element random HIFU array past the ribs at both intercostal and transcostal treatment locations. This method has the advantage of accounting for full effects of scattering and diffraction in three dimensions under continuous wave excitation.

  3. Transparent Fabry-Perot polymer film ultrasound array for backward-mode photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Beard, Paul C.; Zhang, Edward Z. Y.; Cox, Benjamin T.

    2004-07-01

    A novel optical ultrasound sensor has been developed for backward-mode photoacoustic imaging. The sensor is based on a Fabry Perot polymer film interferometer, the mirrors of which are transparent to 1064nm, but highly reflective at 850nm. When illuminated by a CW interrogating laser source at the latter wavelength, the system acts as a resonant Fabry Perot (FP) sensing cavity, the reflected intensity output of which is dependent upon acoustically-induced changes in the optical thickness of the polymer film. By optically addressing different regions of the sensor, a notional ultrasound array of arbitrary aperture and dimensionality can be synthesised. The system was demonstrated in backward mode by transmitting 1064nm excitation laser pulses through the sensor into an Intralipid scattering solution (μa=0.03mm-1, μs'=1mm-1) containing various absorbing structures and detecting the resulting photoacoustic signals over a line. A 1D depth profile of a 1.3mm thick absorbing polymer sheet (´a=0.8mm-1) immersed to a depth of 12mm in the Intralipid solution was obtained by performing an 11mm linescan. In another experiment, a 3-layer structure consisting of 0.076mm thick line absorbers was immersed in Intralipid and a 2D image reconstructed from the detected photoacoustic signals using an inverse k-space reconstruction algorithm. Lateral resolution was 0.4mm and the vertical resolution 0.1mm. The ability of this system to map wideband photoacoustic signals with high sensitivity in backward mode may provide a useful tool for high resolution imaging of superficial tissue structures such as the skin microvasculature.

  4. Adaptive multibeam phased array design for a Spacelab experiment

    NASA Technical Reports Server (NTRS)

    Noji, T. T.; Fass, S.; Fuoco, A. M.; Wang, C. D.

    1977-01-01

    The parametric tradeoff analyses and design for an Adaptive Multibeam Phased Array (AMPA) for a Spacelab experiment are described. This AMPA Experiment System was designed with particular emphasis to maximize channel capacity and minimize implementation and cost impacts for future austere maritime and aeronautical users, operating with a low gain hemispherical coverage antenna element, low effective radiated power, and low antenna gain-to-system noise temperature ratio.

  5. Comparison of Two Detection Combination Algorithms for Phased Array Radars

    DTIC Science & Technology

    2015-07-01

    data were generated by a simulator of multi-function radar ( MFR ) and the combination algorithms are evaluated with the recorded simulation data. With...electronically scanned phased array Multi-Function Radar ( MFR ), is a type of radar whose transmitter and receiver functions are composed of numerous...small transmit/receive modules. An MFR can perform many functions previously performed by individual, dedicated radars for search, tracking and

  6. Wireless Networks for Beamforming in Distributed Phased Array Radar

    DTIC Science & Technology

    2007-09-01

    Radar (VSR) working on L- band is integrated with the AN/SPY-3 Multi Function Radar (MFR), which is an X- band active phased array radar designed to...following standards: Wi-Fi (IEEE 802.11), Bluetooth, Ultra-Wide Band ( UWB ), and Wimax. In recent years, Wi-Fi has become increasingly popular by enabling...30 Figure 14. Maximum capacity for UWB and 802.11n (After [22]). .................................31 Figure 15. Two

  7. Progress of Multifunction Phased Array Radar (MPAR) Program

    DTIC Science & Technology

    2009-01-15

    radars (ARSRs), and Terminal Doppler Weather Radars (TDWRs), as well as the NWS/DOD/FAA Weather Surveillance Radar Model 88 Doppler (WSR-88D), 1...the exploration of simultaneous dual polarization for phased array radars . The ability of an MPAR system to simultaneously support both weather and...from the National Oceanic and Atmospheric Administration’s (NOAA) National Severe Storm Laboratory’s (NSSL) National Weather Radar Testbed (NWRT) in

  8. Range sidelobe suppression in wideband phased array radars

    NASA Astrophysics Data System (ADS)

    Belcher, Melvin L., Jr.; Moss, Karen M.

    The authors delineate some considerations in achieving RSL (range sidelobe) suppression in wideband phased arrays. Attention is given to wideband radar characteristics suppression of spurious signals, and sources of wideband RSLs. It is suggested that the parallelism associated with the transmitter and antenna paths should mitigate associated uncorrelated time-varying error modulation. The exciter can be a major RSL contributor unless spurious signal suppression with the SSBM (single sideband modulator) is emphasized in design and calibration procedures.

  9. Thermoacoustic range verification using a clinical ultrasound array provides perfectly co-registered overlay of the Bragg peak onto an ultrasound image.

    PubMed

    Patch, S K; Kireeff Covo, M; Jackson, A; Qadadha, Y M; Campbell, K S; Albright, R A; Bloemhard, P; Donoghue, A P; Siero, C R; Gimpel, T L; Small, S M; Ninemire, B F; Johnson, M B; Phair, L

    2016-08-07

    The potential of particle therapy due to focused dose deposition in the Bragg peak has not yet been fully realized due to inaccuracies in range verification. The purpose of this work was to correlate the Bragg peak location with target structure, by overlaying the location of the Bragg peak onto a standard ultrasound image. Pulsed delivery of 50 MeV protons was accomplished by a fast chopper installed between the ion source and the cyclotron inflector. The chopper limited the train of bunches so that 2 Gy were delivered in [Formula: see text]. The ion pulse generated thermoacoustic pulses that were detected by a cardiac ultrasound array, which also produced a grayscale ultrasound image. A filtered backprojection algorithm focused the received signal to the Bragg peak location with perfect co-registration to the ultrasound images. Data was collected in a room temperature water bath and gelatin phantom with a cavity designed to mimic the intestine, in which gas pockets can displace the Bragg peak. Phantom experiments performed with the cavity both empty and filled with olive oil confirmed that displacement of the Bragg peak due to anatomical change could be detected. Thermoacoustic range measurements in the waterbath agreed with Monte Carlo simulation within 1.2 mm. In the phantom, thermoacoustic range estimates and first-order range estimates from CT images agreed to within 1.5 mm.

  10. Thermoacoustic range verification using a clinical ultrasound array provides perfectly co-registered overlay of the Bragg peak onto an ultrasound image

    NASA Astrophysics Data System (ADS)

    Patch, S. K.; Kireeff Covo, M.; Jackson, A.; Qadadha, Y. M.; Campbell, K. S.; Albright, R. A.; Bloemhard, P.; Donoghue, A. P.; Siero, C. R.; Gimpel, T. L.; Small, S. M.; Ninemire, B. F.; Johnson, M. B.; Phair, L.

    2016-08-01

    The potential of particle therapy due to focused dose deposition in the Bragg peak has not yet been fully realized due to inaccuracies in range verification. The purpose of this work was to correlate the Bragg peak location with target structure, by overlaying the location of the Bragg peak onto a standard ultrasound image. Pulsed delivery of 50 MeV protons was accomplished by a fast chopper installed between the ion source and the cyclotron inflector. The chopper limited the train of bunches so that 2 Gy were delivered in 2 μ \\text{s} . The ion pulse generated thermoacoustic pulses that were detected by a cardiac ultrasound array, which also produced a grayscale ultrasound image. A filtered backprojection algorithm focused the received signal to the Bragg peak location with perfect co-registration to the ultrasound images. Data was collected in a room temperature water bath and gelatin phantom with a cavity designed to mimic the intestine, in which gas pockets can displace the Bragg peak. Phantom experiments performed with the cavity both empty and filled with olive oil confirmed that displacement of the Bragg peak due to anatomical change could be detected. Thermoacoustic range measurements in the waterbath agreed with Monte Carlo simulation within 1.2 mm. In the phantom, thermoacoustic range estimates and first-order range estimates from CT images agreed to within 1.5 mm.

  11. Large-Aperture Membrane Active Phased-Array Antennas

    NASA Technical Reports Server (NTRS)

    Karasik, Boris; McGrath, William; Leduc, Henry

    2009-01-01

    Large-aperture phased-array microwave antennas supported by membranes are being developed for use in spaceborne interferometric synthetic aperture radar systems. There may also be terrestrial uses for such antennas supported on stationary membranes, large balloons, and blimps. These antennas are expected to have areal mass densities of about 2 kg/sq m, satisfying a need for lightweight alternatives to conventional rigid phased-array antennas, which have typical areal mass densities between 8 and 15 kg/sq m. The differences in areal mass densities translate to substantial differences in total mass in contemplated applications involving aperture areas as large as 400 sq m. A membrane phased-array antenna includes patch antenna elements in a repeating pattern. All previously reported membrane antennas were passive antennas; this is the first active membrane antenna that includes transmitting/receiving (T/R) electronic circuits as integral parts. Other integral parts of the antenna include a network of radio-frequency (RF) feed lines (more specifically, a corporate feed network) and of bias and control lines, all in the form of flexible copper strip conductors on flexible polymeric membranes. Each unit cell of a prototype antenna (see Figure 1) contains a patch antenna element and a compact T/R module that is compatible with flexible membrane circuitry. There are two membrane layers separated by a 12.7-mm air gap. Each membrane layer is made from a commercially available flexible circuit material that, as supplied, comprises a 127-micron-thick polyimide dielectric layer clad on both sides with 17.5-micron-thick copper layers. The copper layers are patterned into RF, bias, and control conductors. The T/R module is located on the back side of the ground plane and is RF-coupled to the patch element via a slot. The T/R module is a hybrid multilayer module assembled and packaged independently and attached to the membrane array. At the time of reporting the information for

  12. PATL: A RFID Tag Localization based on Phased Array Antenna

    PubMed Central

    Qiu, Lanxin; Liang, Xiaoxuan; Huang, Zhangqin

    2017-01-01

    In RFID systems, how to detect the position precisely is an important and challenging research topic. In this paper, we propose a range-free 2D tag localization method based on phased array antenna, called PATL. This method takes advantage of the adjustable radiation angle of the phased array antenna to scan the surveillance region in turns. By using the statistics of the tags’ number in different antenna beam directions, a weighting algorithm is used to calculate the position of the tag. This method can be applied to real-time location of multiple targets without usage of any reference tags or additional readers. Additionally, we present an optimized weighting method based on RSSI to increase the locating accuracy. We use a Commercial Off-the-Shelf (COTS) UHF RFID reader which is integrated with a phased array antenna to evaluate our method. The experiment results from an indoor office environment demonstrate the average distance error of PATL is about 21 cm and the optimized approach achieves an accuracy of 13 cm. This novel 2D localization scheme is a simple, yet promising, solution that is especially applicable to the smart shelf visualized management in storage or retail area. PMID:28295014

  13. Control of complex components with Smart Flexible Phased Arrays.

    PubMed

    Casula, O; Poidevin, C; Cattiaux, G; Dumas, Ph

    2006-12-22

    The inspection is mainly performed in contact with ultrasonic wedge transducers; However, the shape cannot fit the changing geometries of components (butt weld, nozzle, elbow). The variable thickness of the coupling layer, between the wedge and the local surface, leads to beam distortions and losses of sensitivity. Previous studies have shown that these two phenomena contribute to reduce the inspection performances leading to shadow area, split beam.... Flexible phased arrays have been developed to fit the complex profile and improve such controls. The radiating surface is composed with independent piezoelectric elements mechanically assembled and a profilometer, embedded in the transducer, measures the local distortion. The computed shape is used by an algorithm to compute in real-time the adapted delay laws compensating the distortions of 2D or 3D profiles. Those delay laws are transferred to the real-time UT acquisition system, which applies them to the piezoelectric elements. This self-adaptive process preserves, during the scanning, the features of the focused beam (orientation and focal depth) in the specimen. To validate the concept of the Smart Flexible Phased Array Transducer, prototypes have been integrated to detect flaws machined in mock-ups with realistic irregular 2D and 3D shapes. Inspections have been carried out on samples showing the enhancement performances of the "Smart Flexible Phased Array" and validating the mechanical and acoustical behaviors of these probes.

  14. Phased-Array Satcom Antennas Developed for Aeronautical Applications

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.

    2001-01-01

    The Advanced Communications (AC) for Aeronautics research at the NASA Glenn Research Center integrates both aeronautics and space communications technologies to achieve the national objective of upgrading the present National Airspace System infrastructure by responding to the agency's aviation capacity and safety goals. One concept for future air traffic management, free flight, presents a significantly increased demand for communications systems capacity and performance in comparison to current air traffic management practices. Current aeronautical communications systems are incapable of supporting the anticipated demands, and the new digital data communications links that are being developed, or are in the early stages of implementation, are not primarily designed to carry the data-intensive free flight air traffic management (ATM) communications loads. Emerging satellite communications technologies are the best potential long-term solution to provide the capacity and performance necessary to enable a mature free flight concept to be deployed. NASA AC/ATM funded the development of a Boeing-designed Ku-band transmit phased-array antenna, a combined in-house and contract effort. Glenn designed and integrated an Aeronautical Mobile Satellite Communications terminal based on the transmit phased-array antenna and a companion receive phased-array antenna previously developed by Boeing.

  15. PATL: A RFID Tag Localization based on Phased Array Antenna.

    PubMed

    Qiu, Lanxin; Liang, Xiaoxuan; Huang, Zhangqin

    2017-03-15

    In RFID systems, how to detect the position precisely is an important and challenging research topic. In this paper, we propose a range-free 2D tag localization method based on phased array antenna, called PATL. This method takes advantage of the adjustable radiation angle of the phased array antenna to scan the surveillance region in turns. By using the statistics of the tags' number in different antenna beam directions, a weighting algorithm is used to calculate the position of the tag. This method can be applied to real-time location of multiple targets without usage of any reference tags or additional readers. Additionally, we present an optimized weighting method based on RSSI to increase the locating accuracy. We use a Commercial Off-the-Shelf (COTS) UHF RFID reader which is integrated with a phased array antenna to evaluate our method. The experiment results from an indoor office environment demonstrate the average distance error of PATL is about 21 cm and the optimized approach achieves an accuracy of 13 cm. This novel 2D localization scheme is a simple, yet promising, solution that is especially applicable to the smart shelf visualized management in storage or retail area.

  16. Simulation and data reconstruction for NDT phased array techniques.

    PubMed

    Chatillon, S; de Roumilly, L; Porre, J; Poidevin, C; Calmon, P

    2006-12-22

    Phased array techniques are now widely employed for industrial NDT applications in various contexts. Indeed, phased array present a great adaptability to the inspection configuration and the application of suitable delay laws allows to optimize the detection and characterization performances by taking into account the component geometry, the material characteristics, and the aim of the inspection. In addition, the amount of potential information issued from the inspection is in general greatly enhanced. It is the case when the employed method involve sequences of shots (sectorial scanning, multiple depth focusing etc) or when signals received on the different channels are stored. At last, application of electronic commutation make possible higher acquisition rates. Accompanying these advantages, it is clear that an optimal use of such techniques require the application of simulation-based algorithms at the different stages of the inspection process: When designing the probe by optimizing number and characteristics of element; When conceiving the inspection method by selecting suitable sequences of shots, computing optimized delay laws and evaluating the performances of the control in terms of zone coverage or flaw detection capabilities; When analysing the results by applying simulation-helped visualization and data reconstruction algorithms. For many years the CEA (French Atomic Energy Commission) has been being greatly involved in the development of such phased arrays simulation-based tools. In this paper, we will present recent advances of this activity and show different examples of application carried out on complex situations.

  17. Photonic implementation of phased array antennas (rf scanning)

    NASA Astrophysics Data System (ADS)

    Nichter, James E.

    1999-07-01

    Phase Array Antennas provided angular scanning (beam steering) from fixed antenna structures. Photonics can accomplish the beam steering with improvements in size and weight along with the remoting benefits utilizing fiber optics. Photonic advantages include True Time Delay beam steering eliminating the beam squint imposed by phase shifted signals produced in an electronic implementation. Another benefit of beam steering is the ability to position nulls in the spacial pattern to reduce the interference signals. Hybrid circuits utilizing both photonic and electronic components take advantages of the best aspects of each technology. Various types of photonic implementations are included.

  18. Phase-type quantum-dot-array diffraction grating

    SciTech Connect

    Wang Chuanke; Kuang Longyu; Wang Zhebin; Cao Leifeng; Liu Shenye; Ding Yongkun; Wang Deqiang; Xie Changqing; Ye Tianchun; Hu Guangyue

    2008-12-15

    A novel phase-type quantum-dot-array diffraction grating (QDADG) is reported. In contrast to an earlier amplitude-type QDADG [C. Wang et al., Rev. Sci. Instrum. 78, 053503 (2007)], the new phase-type QDADG would remove the zeroth order diffraction at some certain wavelength, as well as suppressing the higher-order diffractions. In this paper, the basic concept, the fabrication, the calibration techniques, and the calibration results are presented. Such a grating can be applied in the research fields of beam splitting, laser probe diagnostics, and so on.

  19. Interplay between vortex matter phases and arrays of pinning centers in low temperature superconductors

    NASA Astrophysics Data System (ADS)

    Vicent, Jose L.; Del Valle, Javier; Gomez, Alicia; Rodriguez, Manuel; Granados, Daniel; Galvez, Fernando; Gonzalez, Elvira M.

    2015-03-01

    We have studied vortex matter phases in Nb films grown on Si substrates with arrays of Cu nanodots. The symmetry of the pinning arrays rules the presence of vortex matter phases. Four-fold symmetry arrays enhance the vortex glass transition temperature, at matching fields, in comparison with plain Nb films. This is a similar effect that obtained using arrays of magnetic pinning centers (Villegas et al. PRB72, 174512). Breaking the symmetry of the pinning array, such that the array mimic a smectic crystal, leads to a new phase, in a very narrow temperature window between the liquid and glassy phases, which can be identified with a vortex smectic phase. Remarkably, the smectic vortex phase is enhanced increasing the array symmetry. Increasing the number of vortices vanishes this smectic phase. (H,T) phase diagrams will be presented for different types of arrays. We thank Spanish MINECO and CM.

  20. Ultrasound

    MedlinePlus Videos and Cool Tools

    ... baby's development in the uterus. Ultrasound uses inaudible sound waves to produce a two-dimensional image of the baby while inside the mother's uterus. The sound waves bounce off solid structures in the body ...

  1. Ultrasound

    MedlinePlus

    ... called multiples) To screen for birth defects, like spina bifida or heart defects . Screening means seeing if your ... example, if the ultrasound shows your baby has spina bifida, she may be treated in the womb before ...

  2. Ultrasound

    MedlinePlus

    ... a pregnant woman and assess her fetus Diagnose gallbladder disease Evaluate flow in blood vessels Guide a ... For some ultrasound exams, such as of the gallbladder, your doctor may ask that you not eat ...

  3. The concentric-ring array for ultrasound hyperthermia: combined mechanical and electrical scanning.

    PubMed

    Ibbini, M S; Cain, C A

    1990-01-01

    While two-dimensional phased arrays can be electronically focused and steered in three dimensions without physically moving the applicator, they generally require a relatively large number of small transducer elements and, consequently, complex drive electronics. A configuration that does not require a large number of elements is that of a concentric-ring array. The field conjugation method can be used to produce a focal spot (or multiple spots) along the array axis. The resulting focal regions are very small and need to be steered transversely to heat tumours of typical size. However, steering the focused beam away from the array axis results in annular heating patterns which are often associated with undesired secondary foci (hot spots). In this paper, a method based on combining electrical and mechanical scanning using a concentric-ring applicator is presented. Advantages of the new method over the mechanically scanned fixed-focus transducers, currently in use, are pointed out. Computer simulations are conducted to investigate the possibility of heating different size tumours by appropriately combining the two scanning techniques. The bioheat transfer equation is solved numerically and temperature distributions associated with relevant heating patterns are presented and discussed. The simulations demonstrate the possibility of the combined technique to produce useful heating patterns which cannot be produced by either technique separately.

  4. Quantitative measurement of high intensity focused ultrasound pressure field by optical phase contrast method applying non-continuous phase unwrapping algorithm

    NASA Astrophysics Data System (ADS)

    Syahid, Mohd; Oyama, Seiji; Yasuda, Jun; Yoshizawa, Shin; Umemura, Shin-ichiro

    2015-07-01

    A fast and accurate ultrasound pressure field measurement is necessary for the progress of ultrasound application in medicine. In general, a hydrophone is used to measure the ultrasound field, which takes a long measurement time and might disturb the ultrasound field. Hence, we proposed a new method categorized in an optical method called Phase Contrast method to overcome the drawback in the hydrophone method. The proposed method makes use of the spatial DC spectrum formed in the focal plane to measure the modulated optical phase induced by ultrasound propagation in water. In this study, we take into account the decreased intensity of the DC spectrum at high ultrasound intensity to increase the measurement accuracy of the modulated optical phase. Then, we apply a non-continuous phase unwrapping algorithm to unwrap the modulated optical phase at high ultrasound intensity. From, the unwrapped result, we evaluate the quantitativeness of the proposed method.

  5. Simulation Study of an Ultrasound Retinal Prosthesis With a Novel Contact-Lens Array for Noninvasive Retinal Stimulation.

    PubMed

    Gao, Mengdi; Yu, Yanyan; Zhao, Huixia; Li, Guofeng; Jiang, Hongyang; Wang, Congzhi; Cai, Feiyan; Chan, Leanne Lai-Hang; Chiu, Bernard; Qian, Wei; Qiu, Weibao; Zheng, Hairong

    2017-09-01

    Millions of people around the world suffer from varying degrees of vision loss (including complete blindness) because of retinal degenerative diseases. Artificial retinal prosthesis, which is usually based on electrical neurostimulation, is the most advanced technology for different types of retinal degeneration. However, this technology involves placing a device into the eyeball, and such a highly invasive procedure is inevitably highly risk and expensive. Ultrasound has been demonstrated to be a promising technology for noninvasive neurostimulation, making it possible to stimulate the retina and induce action potentials similar to those elicited by light stimulation. However, the technology of ultrasound retinal stimulation still requires considerable developments before it could be applied clinically. This paper proposes a novel contact-lens array transducer for use in an ultrasound retinal prosthesis (USRP). The transducer was designed in the shape of a contact lens so as to facilitate acoustic coupling with the eye liquid. The key parameters of the ultrasound transducer were simulated, and results are presented that indicate the achievement of 2-D pattern generation and that the proposed contact-lens array is suitable for multiple-focus neurostimulation, and can be used in a USRP.

  6. Phased-array-fed antenna configuration study. Volume 1: Technology assessment

    NASA Technical Reports Server (NTRS)

    Sorbello, R. M.; Zaghloul, A. I.; Lee, B. S.; Siddiqi, S.; Geller, B. D.; Gerson, H. I.; Srinivas, D. N.

    1983-01-01

    The status of the technologies for phased-array-fed dual reflector systems is reviewed. The different aspects of these technologies, including optical performances, phased array systems, problems encountered in phased array design, beamforming networks, MMIC design and its incorporation into waveguide systems, reflector antenna structures, and reflector deployment mechanisms are addressed.

  7. Ultrasonic Phased Arrays for the Inspection of Thick-Section Welds

    DTIC Science & Technology

    2009-09-01

    phased - array ultrasonics in NDE , with specific reference to the inspection of thick- section welds. The...likely that ultrasonic phased arrays will eventually replace conventional ultrasonic methods in many non-destructive evaluation ( NDE ) applications...embraced by the NDE community. The purpose of this report is to present a summary of the advantages and limitations of phased - array ultrasonics

  8. Light focusing and two-dimensional imaging through scattering media using the photoacoustic transmission matrix with an ultrasound array.

    PubMed

    Chaigne, Thomas; Gateau, Jérôme; Katz, Ori; Bossy, Emmanuel; Gigan, Sylvain

    2014-05-01

    We implement the photoacoustic transmission matrix approach on a two-dimensional photoacoustic imaging system, using a 15 MHz linear ultrasound array. Using a black leaf skeleton as a complex absorbing structure, we demonstrate that the photoacoustic transmission matrix approach allows to reveal structural features that are invisible in conventional photoacoustic images, as well as to selectively control light focusing on absorbing targets, leading to a local enhancement of the photoacoustic signal.

  9. Estimation of scatterer size and acoustic concentration in sound field produced by linear phased array transducer

    NASA Astrophysics Data System (ADS)

    Oguri, Takuma; Tamura, Kazuki; Yoshida, Kenji; Mamou, Jonathan; Hasegawa, Hideyuki; Maruyama, Hitoshi; Hachiya, Hiroyuki; Yamaguchi, Tadashi

    2015-07-01

    Although there have been several quantitative ultrasound studies on the methods of estimation of scatterer size and acoustic concentration based on the analysis of RF signals for tissue characterization, some problems, e.g., narrow frequency bandwidths and complex sound fields, have limited the clinical applications of such methods. In this report, two types of ultrasound transducer are investigated for the estimation of the scatterer size and acoustic concentration in two glass bead phantoms of different weight concentrations of 0.25 and 2.50% and those in an excised pig liver. The diameters of the glass beads ranged from 5 to 63 µm with an average of 50 µm. The first transducer is a single element and the other is a linear phased array. A comparison of the estimations obtained using both transducers gives an insight into how these methods could be applied clinically. Results obtained using the two transducers were significantly different. One of the possible explanations is that beamforming could significantly affect the backscatter coefficient estimation, which was not taken into account.

  10. Phased array antenna with couplers in spatial filter arrangement

    NASA Astrophysics Data System (ADS)

    Lopez, Alfred R.

    1992-02-01

    A lossless spatial filter is provided between the antenna input ports and the elements of an array antenna so that the effective element pattern associated with each input port is primarily within a selected angular region of space. The antenna elements are arranged along a predetermined path and each element is connected to only one output port of the spatial filter. A beam steering unit controls the direction of radiation and includes N phase shifters and means for controlling the phase shifters. Each phase shifter has an input port and an output port which is connected to only one input port of the spatial filter. The antenna also includes a supply means for supplying wave energy signals. The supply means includes a signal generator supplying a power divider having N output signal ports, each output port connected to only one phase shifter input port. In microwave landing systems, this invention provides a non-thinned or fully filled array which may be used to achieve linearity and minimize the field monitor distance for the glide path antenna. A synthesis procedure for a five level non-thinned spatial filter is included.

  11. Ultrasound array photoacoustic microscopy for dynamic in vivo 3D imaging

    NASA Astrophysics Data System (ADS)

    Song, Liang; Maslov, Konstantin; Shung, K. Kirk; Wang, Lihong V.

    2010-02-01

    Using realtime ultrasound array photoacoustic microscopy (UA-PAM), we demonstrated the feasibility of noninvasive in vivo imaging of human pulsatile dynamics, as well as 3-D dynamic imaging of sentinel lymph nodes (SLNs) in a murine model. The system, capable of realtime B-scan imaging at 50 Hz and high-speed 3-D imaging, was validated by imaging the subcutaneous microvasculature in rats and humans. After the validation, a human superficial palmar was imaged, and its pulsatile dynamics monitored, with 20-ms B-scan imaging temporal resolution. In addition, noninvasive photoacoustic sentinel lymph node (SLN) mapping with high spatial resolution has the potential to reduce the false negative rate and eliminate the use of radioactive tracers. Upon intra-dermal injection of Evans blue, the system maps SLNs accurately in mice and rats. Furthermore, the ~6 s 3-D imaging temporal resolution offers the capability to quantitatively and noninvasively monitor the dye dynamics in SLNs in vivo through sequential 3-D imaging. The demonstrated capability suggests that high-speed 3-D photoacoustic imaging should facilitate the understanding of the dynamics of various dyes in SLNs, and potentially help identify SLNs with high accuracy. With the results shown in this study, we believe that UA-PAM can potentially enable many new possibilities for studying functional and physiological dynamics in both preclinical and clinical imaging settings.

  12. A preliminary evaluation work on a 3D ultrasound imaging system for 2D array transducer

    NASA Astrophysics Data System (ADS)

    Zhong, Xiaoli; Li, Xu; Yang, Jiali; Li, Chunyu; Song, Junjie; Ding, Mingyue; Yuchi, Ming

    2016-04-01

    This paper presents a preliminary evaluation work on a pre-designed 3-D ultrasound imaging system. The system mainly consists of four parts, a 7.5MHz, 24×24 2-D array transducer, the transmit/receive circuit, power supply, data acquisition and real-time imaging module. The row-column addressing scheme is adopted for the transducer fabrication, which greatly reduces the number of active channels . The element area of the transducer is 4.6mm by 4.6mm. Four kinds of tests were carried out to evaluate the imaging performance, including the penetration depth range, axial and lateral resolution, positioning accuracy and 3-D imaging frame rate. Several strong reflection metal objects , fixed in a water tank, were selected for the purpose of imaging due to a low signal-to-noise ratio of the transducer. The distance between the transducer and the tested objects , the thickness of aluminum, and the seam width of the aluminum sheet were measured by a calibrated micrometer to evaluate the penetration depth, the axial and lateral resolution, respectively. The experiment al results showed that the imaging penetration depth range was from 1.0cm to 6.2cm, the axial and lateral resolution were 0.32mm and 1.37mm respectively, the imaging speed was up to 27 frames per second and the positioning accuracy was 9.2%.

  13. Deeply penetrating in vivo photoacoustic imaging using a clinical ultrasound array system.

    PubMed

    Kim, Chulhong; Erpelding, Todd N; Jankovic, Ladislav; Pashley, Michael D; Wang, Lihong V

    2010-07-26

    Using a hand-held photoacoustic probe integrated with a clinical ultrasound array system, we successfully imaged objects deeply positioned in biological tissues. The optical contrasts were enhanced by methylene blue with a concentration of ~30 mM. The penetration depth reached ~5.2 cm in chicken breast tissue by using 650-nm wavelength, which is ~4.7 times the 1/e optical penetration depth. This imaging depth was achieved using a laser fluence on the tissue surface of only 3 mJ/cm(2), which is 1/7 of the American National Standards Institute (ANSI) safety limit (20 mJ/cm(2)). The noise equivalent sensitivity at this depth was ~11 mM. Further, after intradermal injection of methylene blue in a rat, a sentinel lymph node was easily detected in vivo, beneath a 2-cm thick layer of chicken breast. Also, blood located 3.5 cm deep in the rat was clearly imaged with intrinsic contrast. We have photoacoustically guided insertion of a needle into a rat sentinel lymph node with accumulated methylene blue. These results highlight the clinical potential of photoacoustic image-guided identification and needle biopsy of sentinel lymph nodes for axillary staging in breast cancer patients.

  14. Phased-array vector velocity estimation using transverse oscillations.

    PubMed

    Pihl, Michael J; Marcher, Jonne; Jensen, Jorgen A

    2012-12-01

    A method for estimating the 2-D vector velocity of blood using a phased-array transducer is presented. The approach is based on the transverse oscillation (TO) method. The purposes of this work are to expand the TO method to a phased-array geometry and to broaden the potential clinical applicability of the method. A phased-array transducer has a smaller footprint and a larger field of view than a linear array, and is therefore more suited for, e.g., cardiac imaging. The method relies on suitable TO fields, and a beamforming strategy employing diverging TO beams is proposed. The implementation of the TO method using a phased-array transducer for vector velocity estimation is evaluated through simulation and flow-rig measurements are acquired using an experimental scanner. The vast number of calculations needed to perform flow simulations makes the optimization of the TO fields a cumbersome process. Therefore, three performance metrics are proposed. They are calculated based on the complex TO spectrum of the combined TO fields. It is hypothesized that the performance metrics are related to the performance of the velocity estimates. The simulations show that the squared correlation values range from 0.79 to 0.92, indicating a correlation between the performance metrics of the TO spectrum and the velocity estimates. Because these performance metrics are much more readily computed, the TO fields can be optimized faster for improved velocity estimation of both simulations and measurements. For simulations of a parabolic flow at a depth of 10 cm, a relative (to the peak velocity) bias and standard deviation of 4% and 8%, respectively, are obtained. Overall, the simulations show that the TO method implemented on a phased-array transducer is robust with relative standard deviations around 10% in most cases. The flow-rig measurements show similar results. At a depth of 9.5 cm using 32 emissions per estimate, the relative standard deviation is 9% and the relative bias is -9

  15. Application of ultrasound in textile wet processing, Phase 1

    SciTech Connect

    Smith, C.B. . Coll. of Textiles)

    1992-11-01

    The US textile industry urgently needs new technologies to keep the industry competitive. This study was designed to develop a pilot plant-scale ultrasonic continuous yarn-dyeing system and to establish a foundation for continuing research in the use of ultrasonic energy in textile processes. On the basis of their findings in the literature on ultrasound-enhanced textile wet processing, researchers designed laboratory- and pilot-scale equipment and conducted studies using various dye and fiber combinations. In laboratory studies they used small vessels of approximately 1-liter capacity and ultrasound probes of 400--1200 W output. Pilot studies were conducted in a 40-gallon dye tank using ultrasound power of approximately 5 kW. Investigations on dye diffusion showed that ultrasound increased diffusion coefficients by typically 30% and permeability coefficients by more than 300%, thereby enhancing dye penetration. The apparent activation energy of diffusion was decreased by approximately 24%. The decrease in activation energy shows a potential for reducing dyeing temperatures. Ultrasound also increased the reactivity of fiber-reactive dyes. Researchers obtained the most promising pilot plant results in the dyeing of nylon with acid dyes. Ultrasonic techniques may also benefit polyester dyed with disperse dyes. One hundred percent polyester dyed in the laboratory had approximately 150 percent increased depth. This knowledge of ultrasonic effects on fundamental processes leads to a better design for the dyeing process in pilot plant and commercial scale-up applications. The study shows that the use of ultrasound for dyeing will replace expensive thermal energy and chemicals, which have to be treated in waste water, with electricity. It also improves the quality of dyed fiber, thereby potentially enhancing the competitiveness of the US textile industry.

  16. Determining temperature distribution in tissue in the focal plane of the high (>100 W/cm(2)) intensity focused ultrasound beam using phase shift of ultrasound echoes.

    PubMed

    Karwat, Piotr; Kujawska, Tamara; Lewin, Peter A; Secomski, Wojciech; Gambin, Barbara; Litniewski, Jerzy

    2016-02-01

    In therapeutic applications of High Intensity Focused Ultrasound (HIFU) the guidance of the HIFU beam and especially its focal plane is of crucial importance. This guidance is needed to appropriately target the focal plane and hence the whole focal volume inside the tumor tissue prior to thermo-ablative treatment and beginning of tissue necrosis. This is currently done using Magnetic Resonance Imaging that is relatively expensive. In this study an ultrasound method, which calculates the variations of speed of sound in the locally heated tissue volume by analyzing the phase shifts of echo-signals received by an ultrasound scanner from this very volume is presented. To improve spatial resolution of B-mode imaging and minimize the uncertainty of temperature estimation the acoustic signals were transmitted and received by 8 MHz linear phased array employing Synthetic Transmit Aperture (STA) technique. Initially, the validity of the algorithm developed was verified experimentally in a tissue-mimicking phantom heated from 20.6 to 48.6 °C. Subsequently, the method was tested using a pork loin sample heated locally by a 2 MHz pulsed HIFU beam with focal intensity ISATA of 129 W/cm(2). The temperature calibration of 2D maps of changes in the sound velocity induced by heating was performed by comparison of the algorithm-determined changes in the sound velocity with the temperatures measured by thermocouples located in the heated tissue volume. The method developed enabled ultrasound temperature imaging of the heated tissue volume from the very inception of heating with the contrast-to-noise ratio of 3.5-12 dB in the temperature range 21-56 °C. Concurrently performed, conventional B-mode imaging revealed CNR close to zero dB until the temperature reached 50 °C causing necrosis. The data presented suggest that the proposed method could offer an alternative to MRI-guided temperature imaging for prediction of the location and extent of the thermal lesion prior to applying the

  17. Improved Phased Array Imaging of a Model Jet

    NASA Technical Reports Server (NTRS)

    Dougherty, Robert P.; Podboy, Gary G.

    2010-01-01

    An advanced phased array system, OptiNav Array 48, and a new deconvolution algorithm, TIDY, have been used to make octave band images of supersonic and subsonic jet noise produced by the NASA Glenn Small Hot Jet Acoustic Rig (SHJAR). The results are much more detailed than previous jet noise images. Shock cell structures and the production of screech in an underexpanded supersonic jet are observed directly. Some trends are similar to observations using spherical and elliptic mirrors that partially informed the two-source model of jet noise, but the radial distribution of high frequency noise near the nozzle appears to differ from expectations of this model. The beamforming approach has been validated by agreement between the integrated image results and the conventional microphone data.

  18. Low Noise Performance Perspectives Of Wideband Aperture Phased Arrays

    NASA Astrophysics Data System (ADS)

    Woestenburg, E. E. M.; Kuenen, J. C.

    2004-06-01

    A general analysis of phased array noise properties and measurements, applied to one square meter tiles of the Thousand Element Array (THEA), has resulted in a procedure to define the noise budget for a THEA-tile (Woestenburg and Dijkstra, 2003). The THEA system temperature includes LNA and receiver noise, antenna connecting loss, noise coupling between antenna elements and other possible contributions. This paper discusses the various noise contributions to the THEA system temperature and identifies the areas where improvement can be realized. We will present better understanding of the individual noise contributions using measurements and analysis of single antenna/receiver elements. An improved design for a 1-m2 Low Noise Tile (LNT) will be discussed and optimized low noise performance for the LNT is presented. We will also give future perspectives of the noise performance for such tiles, in relation to the requirements for SKA in the 1 GHz frequency range.

  19. Improved arrayed-waveguide-grating layout avoiding systematic phase errors.

    PubMed

    Ismail, Nur; Sun, Fei; Sengo, Gabriel; Wörhoff, Kerstin; Driessen, Alfred; de Ridder, René M; Pollnau, Markus

    2011-04-25

    We present a detailed description of an improved arrayed-waveguide-grating (AWG) layout for both, low and high diffraction orders. The novel layout presents identical bends across the entire array; in this way systematic phase errors arising from different bends that are inherent to conventional AWG designs are completely eliminated. In addition, for high-order AWGs our design results in more than 50% reduction of the occupied area on the wafer. We present an experimental characterization of a low-order device fabricated according to this geometry. The device has a resolution of 5.5 nm, low intrinsic losses (< 2 dB) in the wavelength region of interest for the application, and is polarization insensitive over a wide spectral range of 215 nm.

  20. Multiple beam phased array for Space Station Control Zone Communications

    NASA Astrophysics Data System (ADS)

    Halsema, P. B.

    The Space Station Communications Control Zone is a disk shaped region 40 nautical miles in diameter and 10 nautical miles thick centered about the Space Station. It is estimated that 6 simultaneous Multiple Access (MA) channels will be required to satisfy the projected communications needs within this zone. These channels will be used to communicate with MA users located anywhere within the Control Zone. This paper details the tradeoffs and design implementation of a multiple beam integrated phased array to provide antenna coverage of the Control Zone. The array is a compact, modular assembly using Gallium Arsenide circuits, microstrip elements, and advanced packaging techniques. This results in a small, reliable antenna system capable of meeting the projected Space Station requirements and flexible enough to grow and evolve as the Space Station communications needs develop.