Towards clinical computed ultrasound tomography in echo-mode: Dynamic range artefact reduction

Jaeger, Michael; Frenz, Martin

doi:10.1016/j.ultras.2015.06.003

Cited by 32 publications

(27 citation statements)

References 21 publications

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“…However, the object to be imaged should be placed close to the lens for the coupling of the near-field evanescent wave to the lens. In other words, it is difficult to apply these AMM-based lenses to conventional far-field imaging methods based on a pulse-echo scheme in which the object would be placed far away from the lens 9 – 11 . Moreover, although the principle of the AMM-based lenses has been experimentally proven 6 – 8 , 12 , manufacturing a microstructure of such a lens in the megasonic range (>1 MHz) involves significant challenges related to fabrication quality and the control of energy losses.…”

Section: Introductionmentioning

confidence: 99%

Realization of an ultrathin acoustic lens for subwavelength focusing in the megasonic range

Hyun

Kim

Doh

et al. 2018

Sci Rep

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In this study, we report the first experimental realization of an ultrathin (0.14λ, λ = 1.482 mm means wavelength at 1 MHz in the water medium) subwavelength focusing acoustic lens that can surpass the Rayleigh diffraction limit (0.61λ/NA, NA means numerical aperture). It is termed a Super-Oscillatory Acoustic Lens (SOAL), and it operates in the megasonic range. The SOAL represents an interesting feature allowing the achievement of subwavelength focusing without the need to operate in close proximity to the object to be imaged. The optimal layout of the SOAL is obtained by utilizing a systematic design approach, referred to here as topology optimization. To this end, the optimization formulation is newly defined. The optimized SOAL is fabricated using a photo-etching process and its subwavelength focusing performance is verified experimentally via an acoustic intensity measurement system. From these measurements, we found that the proposed optimized SOAL can achieve superior focusing features with a Full Width at Half Maximum (FWHM) of ~0.40λ/NA ≃ 0.84 mm (for our SOAL, NA = 0.707) with the transmission efficiency of 26.5%.

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Section: Introductionmentioning

confidence: 99%

Realization of an ultrathin acoustic lens for subwavelength focusing in the megasonic range

Hyun

Kim

Doh

et al. 2018

Sci Rep

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“…Although ultrasonic computed tomography (USCT) was developed for estimation of the spatial distribution of sound speeds [57][58][59][60][61][62], it is not suitable for ultrasonography based on the pulse-echo method because USCT basically requires measurement of an ultrasonic wave transmitted through a medium. Recently, USCT in the pulseecho mode [63][64][65][66] is being studied intensively.…”

Section: Estimation Of Speed Of Soundmentioning

confidence: 99%

Advances in ultrasonography: image formation and quality assessment

Hasegawa

2021

J Med Ultrasonics

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Delay-and-sum (DAS) beamforming is widely used for generation of B-mode images from echo signals obtained with an array probe composed of transducer elements. However, the resolution and contrast achieved with DAS beamforming are determined by the physical specifications of the array, e.g., size and pitch of elements. To overcome this limitation, adaptive imaging methods have recently been explored extensively thanks to the dissemination of digital and programmable ultrasound systems. On the other hand, it is also important to evaluate the performance of such adaptive imaging methods quantitatively to validate whether the modification of the image characteristics resulting from the developed method is appropriate. Since many adaptive imaging methods have been developed and they often alter image characteristics, attempts have also been made to update the methods for quantitative assessment of image quality. This article provides a review of recent developments in adaptive imaging and image quality assessment.

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“…Each projection is acquired by transmitting multiple plane waves (−20°to 20°in steps of 0.5°) and then coherently adding the reconstructed images. The US images are reconstructed a using Fourier transform-based reconstruction algorithm [42], where the curved array is approximated to be linear, under the assumption that the ratio of the phased array aperture to the radius of curvature is small. Multiple projections are then combined to form an image of the object cross section.…”

Section: Us Imagingmentioning

confidence: 99%

Photoacoustic and acousto-optic tomography for quantitative and functional imaging

Hussain¹,

Hondebrink²,

Staley³

et al. 2018

Optica

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Optical absorption contrast, large imaging depth at ultrasonic resolution, and the potential of functional/quantitative imaging are the features driving the rapid development of photoacoustic (PA) imaging. For quantitative and functional PA imaging, the fluence distribution is required to transform a PA image to a map of absorption coefficients. A suitable method to estimate the fluence for in vivo applications must not require a priori knowledge of the medium optical properties, should work for various illumination conditions, and must be applicable to different PA imaging geometries. Existing methods of estimating fluence in tissue do not meet these requirements simultaneously. Here we present a method to measure the fluence distribution in tissue using acousto-optics (AO) that meets all the above requirements. We developed a PA and AO tomography system for small-animal imaging to investigate the potential and the feasibility of fluence-corrected PA imaging using our method in a single instrument. We performed experiments on phantoms, an ex vivo tissue sample, and freshly sacrificed mice. We demonstrate that the correction for spatial and spectral fluence variations in PA images establishes the direct relation between image value and optical absorption, which in turns improves the quantitative estimation of blood oxygen saturation.

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Towards clinical computed ultrasound tomography in echo-mode: Dynamic range artefact reduction

Cited by 32 publications

References 21 publications

Realization of an ultrathin acoustic lens for subwavelength focusing in the megasonic range

Realization of an ultrathin acoustic lens for subwavelength focusing in the megasonic range

Advances in ultrasonography: image formation and quality assessment

Photoacoustic and acousto-optic tomography for quantitative and functional imaging

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