Real-Time 3-D Ultrasound with Multiple Transducer Arrays

The cover is an illustration of the posterior heart showing the left atrium and four pulmonary veins. A side viewing 3-D ultrasound intracardiac catheter transducer is shown resting in the coronary sinus as it scans the left atrium. Simultaneously, a forward viewing 3-D ultrasound intracardiac catheter transducer is inserted into the heart and scans a pair of pulmonary veins for guidance of ablation devices.

Schematic used and modified with permission of Wesley Norman, Ph.D. (http://mywebpages.comcast.net/wnor/heartpostheartchambers.jpg).

Image courtesy Matthew P. Fronheiser, Duke University, Department of Biomedical Engineering, Durham, NC. See article on page 100.

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LLSAW mode: Longitudinal leaky surface acoustic wave on YZ-cut lithium niobate enabling 5-GHz SAW filters

The cover image visualizes the characteristic displacements that are polarized exactly in the sagittal plane for the longitudinal leaky SAW (LLSAW) mode propagating under a periodic system of aluminum electrodes on YZ-cut lithium niobate. The displacements, exaggerated for the sake of clarity, were simulated using FEM/BEM software developed in the Materials Physics Laboratory at the Helsinki University of Technology. The color coding for the substrate indicates the displacement component in the propagation (crystal Z) direction. The shades of gray on the electrodes indicate the magnitude of this displacement component. The high velocity of the LLSAW (about twice that of the Rayleigh mode on the same substrate) enables the fabrication of wide band bandpass SAW filters for the 5-GHz frequency regime using conventional optical lithography.

Image courtesy of Tapani Makkonen and Martti M. Salomaa, Materials Physics Laboratory, Helsinki University of Technology, Espoo, Finland. See article on page 393.

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A 40-MHz PVDF based annular array transducer

A five-ring annular array constructed from a 9-mm PVDF membrane bonded to a copper-clad polyimide (CCP) backing layer. The array pattern is formed on the CCP and the geometric focus is 12 mm. The in vitro bovine eye B-mode images demonstrate the improved depth-of-field and resolution achieved with the array. The upper image is digitized radio-frequency (RF) data from all 25 transmit/receive ring pairs summed, with no time-delay corrections, and the bottom image is the same RF data processed with a synthetic focusing algorithm (41 focal zones).

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Two-Dimensional Ultrasonic Imaging of Myocardial Strain

An echocardiogram (a), a directional cardiac elastogram incorporating both compressive (red) and relaxational (blue) strain (b), and a magnitude cardiac elastogram (c) are shown for standard echocardiographic imaging views. A short-axis view at endsystole of a subject with coronary heart disease (top row) demonstrates compressive strains in the myocardium (arrow). A four-chamber apical view during early systole (lower row) of a second subject shows the presence of strain components in the septal wall (arrow). A GE Vingmed Vivid FiVe ultrasound system (GE-Vingmed, Horten, Norway), using a 2.5-MHz phased array transducer, was used to collect loops of in-phase/ quadrature (IQ) echo data at a frame rate of 50s-1. These incremental cardiac elastograms over 20 ms intervals were generated using a 3-mm window length with 75% overlap between data segments.

Images courtesy of Tomy Varghese, Quan Chen, James A. Zagzebski, Peter Rahko, and Christian S. Breburda. T. Varghese is with the Department of Medical Physics and the Department of Biomedical Engineering at the University of Wisconsin-Madison, Madison, WI. Q. Chen and J. A. Zagzebski are with the Department of Medical Physics at the University of Wisconsin-Madison, Madison, WI. P. Rahko, and C. S. Breburda are with the Section of Cardiovascular Medicine, Department of Medicine at the University of Wisconsin-Madison, Madison, WI.

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Full-Field Imaging of Film Bulk Acoustic Resonator Lateral Modes

The figure shows the presence of lateral modes in a film bulk acoustic resonator driven near its first thickness extensional mode. A new full-field imaging technique, developed at the Idaho National Engineering & Environmental Laboratory, visualizes the acoustic motion of these modes correlated with the electrical impedance as shown. The imaging technique provides quantitative measurement at video frame rates of the in-phase and quadrature out-of-plane displacements that subsequently are used to determine the normal acoustic amplitude and phase at all points on the resonator surface without scanning. In-phase and quadrature images depend on the acoustic starting phase which, for single mode motion, can be cycled to a point where one image shows nearly no displacement, as seen in the images for 877 MHz.

Images courtesy of Ken L. Telschow, Vance A. Deason, Dave Cottle, and John D. Larson. K. L. Telschow, V. A. Deason, and D. Cottle are with Idaho National Laboratory (formerly Idaho National Engineering & Environmental Laboratory), Physics, Idaho Falls, ID. John D. Larson is currently with Avago Technologies Inc., San Jose, CA. This work was done when he was with Agilent Technologies Inc., Palo Alto, CA. See article K. L. Telschow, V. A. Deason, D. L. Cottle, and J. D. Larson, III, "Full-field imaging of gigahertz film bulk acoustic resonator motion," IEEE Trans. Ultrason., Ferroelect., Freq. Contr., vol. 50, no. 10, pp. 1279-1285, 2003.

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Capacitive micromachined ultrasonic transducers with integrated optical diffraction grating.

The picture on the left shows the scanning electron microscope image of part of a cMUT with aluminum membranes fabricated on quartz substrate for integrated optical detection. The membranes are 100 micrometer in diameter and are suspended 2.5 micrometer above the substrate. The picture on the right is taken from the backside, through the transparent quartz wafer and shows the back electrode of one of the cMUT membranes. The aluminum electrode is shaped in the form of a diffraction grating with 4 micrometer period. The reflected diffraction orders enable optical interferometric detection of the membrane displacement.

Images courtesy: F. Levent Degertekin, Neal A. Hall, and Wook Lee. The contributors are with the Georgia Institute of Technology, School of Mechanical Engineering, Atlanta, GA. See article N. A. Hall, W. Lee, and F. L. Degertekin "Capacitive micromachined ultrasonic transducers with diffraction-based integrated optical displacement detection," IEEE Trans. Ultrason., Ferrelect., Freq. Contr., vol. 50, no. 11, pp. 1570-1580, Nov. 2003.

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Echocardiographic Phased Array Harmonic Field Components

This figure illustrates scanned hydrophone measurements of the fundamental (1f = 1.95 MHz), nonlinearly generated second harmonic (2f = 3.90 MHz), and nonlinearly generated third harmonic (3f = 5.85 MHz) ultrasonic field components produced in the azimuthal plane of a echocardiographic phased array in water. A 0.6 mm diameter membrane hydrophone (Sonic Industries, now Sonora Medical Systems, Longmont, CO) was mechanically stepped in a grid, with a uniform 0.5 mm step size, to map the azimuthal plane at axial depths ranging from 2.0 to 162 mm from the face of the transmitter and transverse distances of -20 to +20 mm, symmetric about the axis of propagation. The source plane was mapped in a similar fashion by scanning the hydrophone in a plane parallel to the face of the transmitter with a 2.0 mm axial displacement. For display purposes, the each harmonic (1f, 2f, and 3f) component image has been normalized to its own maximum value. The relative measured maximum intensities of the 1f, 2f, and 3f components are 0 dB, -14 dB, and -26 dB, respectively, for the azimuthal plane data.

Image courtesy of Kirk D. Wallace, Washington University, Department of Physics, Saint Louis, MO. See article on page 1260.

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Comparing nano-indenter-based modulus images with strain elastograms.

These images illustrate the feasibility of imaging the modulus of soft tissues using nano-indentation, as well as comparing modulus images with strain elastograms. In a) the modulus image of a 20mm x 30mm cross-section of a 3mm thick beef slice obtained at 2% strain using a nano-indenter (MTS-Inc, Nashville, TN) with a 2-mm diameter cylindrical punch is shown. In b) the strain elastogram of the slice, embedded in a clear gelatin block, obtained using a HDI-1000 5-MHz, 60% fractional bandwidth transducer at 1% applied strain and a pre-compression of 1% is shown. The bright white regions indicate decorrelation in the elastogram. In c) the optical image of the same slice is shown. The modulus imaging was done in a plane orthogonal to the strain image. The correlation coefficient between the inverted modulus image and the strain image was 0.69.

Images courtesy of Seshadri Srinivasan, Thomas Krouskop, and Jonathan Ophir. S. Srinivasan is currently working at Siemens Medical Solutions, Ultrasound Division, Mountain View, CA; and J. Ophir and T. Krouskop are with the University of Texas-Houston, Department of Radiology, Houston, TX. J. Ophir is also with the University of Houston, Department of Electrical Engineering, Houston, TX.

This work was supported by National Cancer Institute Program Project P01-CA64597-10 awarded to the University of Texas Medical School at Houston.

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Vibrational Mode Figures

This figure shows distributions of out-of-plane displacement amplitude at the top surface of aluminum/polymer/aluminum layered material calculated by the Rayleigh-Ritz method. These images are used for mode identification of free-vibration resonance frequencies measured with the piezoelectric tripod by comparing them with displacement-amplitude distributions measured by laser-Doppler interferometry.

Images courtesy of Masahiko Hirao and Hirotsugu Ogi. The cover contributors are with Osaka University, Graduate School of Engineering Science, Osaka, Japan. See article "Interface delamination of layered media: Acoustic spectroscopy and modal analysis" IEEE Trans. Ultrason., Ferroelect., Freq. Contr., vol. 51, no. 4, pp. 439-443 Apr. 2004.

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Ring Transducer System and Measured Waveforms

The ring transducer is the circular assembly in the foreground connected by cables to electronics in the background. The ring transducer contains 2,048 elements with a 2.5-MHz center frequency, a 67% -6-dB bandwidth, and a 0.23-mm pitch arranged in a 150-mm diameter ring with a 25-mm elevation. The electronics are comprised of 128 independently programmable transmitters with 8-bit resolution, 16 receivers with 12-bit resolution and independently programmable time-variable gain, a 2,048:128 transmit multiplexer, and a 2,048:16 receive multiplexer.

3-D Ultrasound Guidance of Surgical Robotics: A Feasibility Study

Laparoscopic ultrasound has seen increased use as a surgical aide in general, gynecological, and urological procedures. The application of real-time three-dimensional (RT3D) ultrasound to these laparoscopic procedures may increase information available to the surgeon and serve as an additional intraoperative guidance tool. The integration of RT3D with recent advances in robotic surgery can also increase automation and ease of use. In this study, a 1 cm diameter probe for RT3D has been used laparoscopically for in vivo imaging of a canine. The probe, which operates at 5 MHz, was used to image the spleen, liver, and gall bladder as well as to guide surgical instruments. Furthermore, the 3D measurement system of the volumetric scanner used with this probe was tested as a guidance mechanism for a robotic linear motion system in order to simulate the feasibility of RT3D/robotic surgery integration. Using images acquired with the 3D laparoscopic ultrasound device, coordinates were acquired by the scanner and used to direct a robotically controlled needle towards desired in vitro targets as well as targets in a post-mortem canine. The RMS error for these measurements was 1.34 mm using optical alignment and 0.76 mm using ultrasound alignment.

Images courtesy of Eric Christopher Pua, Matthew P. Fronheiser, Joanna R. Noble, Edward D. Light, Patrick D. Wolf, Daniel von Allmen, and Stephen W. Smith. E. C. Pua, M. P. Fronheiser, J. R. Noble, E. D. Light, P. D. Wolf, and S. W. Smith are with Duke University, Department of Biomedical Engineering, Durham, NC. D. von Allmen is with the University of North Carolina at Chapel Hill, Department of Pedatric Surgery, Chapel Hill, NC. See article on page 1999.

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Special Issue on Nanoscale Ferroelectrics

(a) Nanoscale ring structure cut into a thin single crystal BaTiO₃ lamella (about 100 nm thick), using a focused ion beam microscope. It is a first step in the experimental investigation of ferroelectric behavior in nanoring structures, which could be as exciting as that already seen in ferromagnetic nanorings (see paper by M.M. Saad et al. on page 2208 of this issue). (b) In-plane 300 × 300 nm² piezoresponse image of PbTiO₃ nanograins obtained under ultrahigh vacuum demonstrating domain width of 4 nm (see paper by F. Peter, et al. on page 2253 of this issue). (c) Piezoresponse Force Microscopy image of a 28 × 11 domain array used to spell out MaNEP (Materials with Novel Electronic Properties). The domains have radii of about 50 nm, with a spacing of 140 nm between array positions (see paper by M. Dawber, et al. on page 2261 of this issue). (d) Artist's rendition of read-write process in ferroelectric data storage. “1” and “0” correspond to up and down orientations of ferroelectric polarization [image courtesy of S. Jesse and S.V. Kalinin (ORNL)].

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