Acoustic Imaging with Thin Annular Apertures

Vilkomerson, David

doi:10.1007/978-1-4757-0827-1_18

Cited by 23 publications

(2 citation statements)

References 9 publications

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“…It is well known that the thin annulus side lobes show a J 0 ( κ 1 x )/ κ 1 x response [29], which exhibits a very high first lobe height (−8 dB, large gray square, Fig. 3) and a very slow side lobe decay (gray line, Fig.…”

Section: Methodsmentioning

confidence: 99%

Design aspects of focal beams from high-intensity arrays

Stephens¹,

Kruse

Qin

et al. 2011

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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As the applications of ultrasonic thermal therapies expand, the design of the high-intensity array must address both the energy delivery of the main beam and the character and relevance of off-target beam energy. We simulate the acoustic field performance of a selected set of circular arrays organized by array format, including flat versus curved arrays, periodic versus random arrays, and center void diameter variations. Performance metrics are based on the −3-dB focal main lobe (FML) positioning range, axial grating lobe (AGL) temperatures, and side lobe levels. Using finite-element analysis, we evaluate the relative heating of the FML and the AGLs. All arrays have a maximum diameter of 100λ, with element count ranging from 64 to 1024 and continuous wave frequency of 1.5 MHz. First, we show that a 50% spherical annulus produces focus beam side lobes which decay as a function of lateral distance at nearly 87% of the exponential rate of a full aperture. Second, for the arrays studied, the efficiency of power delivery over the −3-dB focus positioning range for spherical arrays is at least 2-fold greater than for flat arrays; the 256-element case shows a 5-fold advantage for the spherical array. Third, AGL heating can be significant as the focal target is moved to its distal half-intensity depth from the natural focus. Increasing the element count of a randomized array to 256 elements decreases the AGL-to-FML heating ratio to 0.12 at the distal half-intensity depth. Further increases in element count yield modest improvements. A 49% improvement in the AGL-to-peak heating ratio is predicted by using the Sumanaweera spiral element pattern with randomization.

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Section: Methodsmentioning

confidence: 99%

Design aspects of focal beams from high-intensity arrays

Stephens¹,

Kruse

Qin

et al. 2011

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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show abstract

“…High sidelobes are not unique with limited diffraction beams. They also occur with methods that increase the depth of field of conventional beams, such as using a ring aperture [43]- [45] or the Axicon [46]- [48]. Efforts have been made to reduce sidelobes.…”

Section: Introductionmentioning

confidence: 99%

Bowtie limited diffraction beams for low-sidelobe and large depth of field imaging

1995

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Limited diffraction beams such as Bessel beams and X waves have a large depth of field and thus could have many applications. However, these beams have higher sidelobes as compared to conventional focused beams in their focal planes. In this paper, a new class of limited diffraction beams is developed. These beams are termed bowtie limited diffraction beams because they have bowtie shapes in a plane perpendicular to the beam axis. To obtain pulse-echo images of low sidelobes and a large depth of field, a bowtie limited diffraction beam is used in transmission and its 90 rotated response (around the beam axis) is used in reception. Unlike the summation-subtraction method developed previously, this method does not reduce image frame rate or dynamic range of signals and is not motion sensitive. The theory of the bowtie limited diffraction beams is developed. Computer simulation of the theoretical beams under practical conditions, such as finite aperture, finite bandwidth, and causal excitation, is performed with the Rayleigh-Sommerfeld diffraction formula. The simulated beams are very close to those predicted analytically over a large depth of field.

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Limited diffraction array beams

Liu

1997

Int. J. Imaging Syst. Technol.

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Limited diffraction beams have a large depth of field infinite aperture. Because of their high side lobes and complex and could have many applications. In this article, new limited diffracbeam patterns near the cone surface, these devices are not curtion beams are developed. They are composed of multiple parallel rently used in clinics. Ring antenna [42] or transducer [43,44] is beams and are thus called array beams. A broadband synthetic array another type of device that increases the depth of field. However, experiment is used to produce these beams of a finite aperture, and the depth of field is increased only in the far field of the rings results are in excellent agreement with theory over a large depth of [45,46] where beams diffract significantly. Near the surfaces of field. In addition, potential applications of the new beams to real-time the rings, beams do not even have a central peak. In addition, volumetric imaging and measurement of transverse velocity of blood ring devices have a low energy efficiency because they must be flow are described.

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Acoustic Imaging with Thin Annular Apertures

Cited by 23 publications

References 9 publications

Design aspects of focal beams from high-intensity arrays

Design aspects of focal beams from high-intensity arrays

Bowtie limited diffraction beams for low-sidelobe and large depth of field imaging

Limited diffraction array beams

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