A three-dimensional ultrasonic flow image shows two groups of differentiated scatterers that co-exist in sample volumes. The scatterers were differentiated by their moving velocities using a trapezoid filter in the two-dimensional frequency domain. Two sets of differentiated scatterers moving at 12.7 and 26.3 cm/s are displayed by yellow and red, respectively. (Image courtesy of Yi Zheng and Aiping Yao, Digital Signal Processing Laboratory, St. Cloud State University, St. Cloud, MN and James Greenleaf, Ultrasound Research Laboratory, Mayo Clinic, Rochester, MN.)

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The cover depicts the 3-D vibration maps of the first three modes of the micromembranes of a capacitive micromachined ultrasonic transducer (cMUT). The maps are obtained by laser interferometry scanning and computer processing with interpolated shading (Gouraud shading). Fig. 1(a) shows a SEM photograph of a small part of the cMUT under test, consisting of 1512 micromembranes electrostatically excited in parallel; it is possible to see that each membrane (40 μm in diameter) is surrounded by six small sealed etchant holes. Fig. 1(b) and Fig. 1(d) show the fundamental and second harmonic symmetric modes at 5.2 and 17 MHz, respectively. Fig. 1(c) shows an unexpected antisymmetric mode caused by unavoidable axial asymmetries of the micromembranes. More details can be found in “Vibration maps of capacitive micromachined ultrasonic transducers by laser interferometry,” A. Caronti, H. Majjad, S. Ballandras, G. Caliano, R. Carotenuto, A. Iula, V. Foglietti, and M. Pappalardo (submitted to IEEE UFFC, 2001).

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The cover page shows a sequence of microscopic image frames of a freely flowing contrast agent microbubble. The frames were taken during one cycle of ultrasound insonification, with a center frequency of 500 kHz. The peak negative acoustic pressure at the region of interest was 0.85 MPa. Each frame corresponds to a 45 x 27 µm² area. The exposure time of each frame was 10 ns. Interframe times were 330 ns, except for the time between frames e and f, which was 660 ns. The sequence shows a growing gas encapsulated microbubble of 5.3 µm (a) and 17.6 µm (b), and its maximal growth of 22.9 µm (c). After shrinking to 20.2 µm (d), it ruptured (e). The microbubble had been pushed to the lower left side of the frame, apparently by water that was propelled into the microbubble. A subframe shows the negative of the region of interest. Finally, the deformed mcrobubble re-occurred as an assymetric shape (f). Understanding of microbubble-rupturing behavior is neccessary for developments in medical release burst imaging and ultrasound-guided drug delivery. This work has been supported by the Technology Foundation STW (RKG.5104) and the Interuniversity Cardiology Institute of The Netherlands. (Images courtesy of M. Postema, A. Bouakaz, and N. de Jong, Erasmus University Medical Center, Rotterdam, The Netherlands.)

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Limited Diffraction Bessel Beam Measured in Water

A limited diffraction Bessel beam produced with a 10-ring, 50-mm diameter, 2.5-MHz, and 1-3 ceramic/polymer composite annular array transducer, measured in water along the transducer axis with a 0.5-mm diameter needle hydrophone. The beam has about a 2.4-mm -6 dB central beamwidth and a depth of field of 216 mm.

Image courtesy of Jian-yu Lu (Ultrasound Lab, Department of Bioengineering, The University of Toledo, Toledo, OH) and James F. Greenleaf (Ultrasound Research Laboratory, Mayo Clinic, Rochester, MN).

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Acoustic Microscope Image of Surface-Wave Symmetry in Crystalline Quartz

The cover image is a polar-plot depicting the two-fold symmetry of the “slowness” or inverse phase velocity in quartz. A line-focus transducer was used to generate and sense surface waves in a rotational scan. The data have application for the design of surface acoustic wave (SAW) delay lines in microchip circuits. Figure taken from the IEEE Transactions on UFFC, vol. 47, no. 3, pp. 630–634, May, 2000.

Image courtesy of Gerald V. Blessing, Nelson N. Hsu, and John A. Slotwinski, National Institute of Standards and Technology (NIST), Gaithersburg, MD, and Dan Xiang, NASA Goddard Space Flight Center, Greenbelt, MD.

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Surface-related phase noise in SAW resonators

The adsorption and desorption of gas molecules on the surface of a surface acoustic wave resonator will cause frequency fluctuations. It is in essence a stochastic process of mass loading effect. The surface molecular motion noise may exist in other microelectronic devices. Figure taken from the IEEE Transactions on UFFC, vol. 49, no. 5, pp. 649-655, May, 2002.

Image courtesy of Dai Enguang, Department of Electronics, Peking University, Beijing, China.

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Impulse Response of a Fiber-optic Multilayer Hydrophone

Axial particle velocity δu_ax./δt and radial particle velocity δu_rad./δt for an intersection along the axis of a fiber-optic hydrophone and pressure p in the surrounding water after excitation by a short Gaussian pressure pulse. The results of a finite element simulation show the different types of waves that have an impact on the frequency response of the hydrophone.

Image courtesy of Volker Wilkens, Physikalisch-Technische Bundesanstalt, Barunschweig, Germany. See article page 937.

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The Windows’ Shifts in the Extreme Fix Method

The image shows two windows’ shifts performed during the MTIE calculation: the first shift (blue arrow) to the first extreme (max) in the blue window, the second one (green arrow) to the next sample, as for the green window the extreme values does not change.

UFFC article detailing this work: A. Dobrogowski and M. Kasznia “Maximum Time Interval Error Assessment Based on the Sequential Reducing Data Volume,” IEEE Trans. Ultrason., Ferroelect., Freq. Contr., vol. 49, no. 7, pp. 987-994, Jul., 2002.

Image courtesy Andrzej Dobrogowski and Michal Kasznia, Poznan University of Technology, 60-965 Poznan, Poland.

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LGT / SAW Coupling: Euler angles (0°, q, y)

The three-dimensional plot shows the electromechanical coupling coefficient, K2 [%], for the surface acoustic waves (SAW) on a recent piezoelectric material, langatate (LGT, La₃Ga_5.5Ta_0.5O₁₄), Euler angles (f, q, y) = (0°, q, y). The plot displays several high coupling regions; highest K2, up to K2 @ 0.7%, for q around 151° and y 24°.

Image courtesy of Mauricio Pereira da Cunha, Dept. of Electr. and Comp. Eng., University of Maine, Orono, ME, Donald C. Malocha and Kevin Casey, School of Elec. & Comp. Eng., University of Central Florida, Orlando, FL, and Eric L. Adler, Dept. of Electr. and Comp. Eng., McGill University, Montreal, PQ, Canada. See article page 1292.

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B-Scan Image of a Human Tooth

A 10 MHz curtain B-scan image of a human molar shows scattered reflections from a 1 mm side-drilled cavity along the enamel-dentin boundary that mimics an actual delamination. A surface scatterer due to a natural “crease” is also noticeable just above the cavity along with other reflections from other tubular features.

Image courtesy of Dr. Sleiman R. Ghorayeb and Teresa Valle, Biomedical Research Laboratory, Hofstra University, Hempstead, NY, 11549. See article page 1437

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Parametric images for scatterer density (ESNp) at baseline and after reperfusion in the heart

In (a), the gray scale image reperfusion is shown. In (b), the gross pathology specimen with the location of the ultrasound image plane (outlined in blue) is shown. The ischemic viable myocardium is stained with TTC and appears brick red in color, the infarcted non-viable myocardium remains pale and unstained. The pink region within the infarcted pale area represents a combination of congested capillaries and extravascated red blood cells. The normal, non-ischemic region is stained with Evans Blue. Fig. (c) illustrates the parametric image of effective scatterer (ESNp) number at baseline and Fig. (d) illustrates the parametric image of the same region after reperfusion. The arrows point to the fiducial markers and the imaged myocardium is outlined in yellow. From the parametric images, one can see that areas with higher ESNp value increased in infarcted myocardium and these areas match spatially with the infarcted region in gross image.

Image courtesy of James Greenleaf and Xiaohui Hao, Ultrasound Research Laboratory, Mayo Clinic, Rochester, MN 55905. See article page 1530.

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A Dual-mode Ring-Annular Intravascular Ultrasound (IVUS) Array

Traditional side-viewing IVUS systems provide a cross-sectional image of the vessel lumen. Our proposed intravascular ultrasound array has 64 simultaneous side-viewing and forward-viewing elements distributed evenly on an annulus with an inner and outer diameter of 1.1 mm and 1.3 mm respectively. Both side-viewing and forward-viewing images are obtained electronically by synthetic phased array beamformer.

Image courtesy of Yao Wang and Matthew O'Donnell of the Biomedical Ultrasound Lab, University of Michigan, Ann Arbor, MI 48109 and Douglas N. Stephens of Jomed Inc. Rancho Cordova, CA 95670. See article page 1652.

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