Design of a low cost ultrasound system using diverging beams and synthetic aperture approach: Preliminary study
18 Apr 2017-pp 1108-1111
TL;DR: Results show that the proposed method provides better Lateral Resolution (LR) to that obtained when conventional focused linear array technique is used and is shown to improve further when sign coherence factor weighting is incorporated during beamforming.
Abstract: In this paper, a new method inspired by the synthetic aperture approach is proposed that aims at reducing the system's complexity (only 8 or 16 active elements) without compromising the image quality, and at frame rates comparable to or higher than conventional focused linear array technique. The novel method has been investigated in simulations using Field II software and experiments performed on a wire phantom using an ultrasound scanner. Results show that the proposed method provides better Lateral Resolution (LR) to that obtained when conventional focused linear array technique is used. The estimated LR at the focal point was 1.09 mm and 0.29 mm for conventional and the proposed method, respectively, in simulations. These were estimated to be 1.03 mm and 0.38 mm, respectively, in experiments. The image quality is shown to improve further when sign coherence factor weighting is incorporated during beamforming.
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TL;DR: It can be concluded from the results that DB‐SAT using 8 active transmit elements and 64 active receive elements yields better quality images at higher frame‐rates than those obtained using CFB‐LA with 64 active elements in transmit and receive.
17 citations
Cites methods or result from "Design of a low cost ultrasound sys..."
..., particularly more than 16 elements) leads to a degradation in the image quality due to axial lobes, which was previously reported by many authors [13,26,17]....
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...Specifically, we had investigated and reported on further improvement in lateral resolution by incorporating a simple Sign Coherence Factor (SCF) weighting during beamforming [17]....
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01 Apr 2020
TL;DR: The image quality improved by F-DwMAS compared to DAS and F-DMAS, a minimum-redundancy synthetic aperture technique for achieving high-quality imaging in low complex ultrasound systems.
Abstract: In this paper, the development of a modified beamforming method, named as, Filtered Delay Weight Multiply and Sum (F-DwMAS) beamforming is reported. The developed F-DwMAS method was investigated on a minimum-redundancy synthetic aperture technique, called as 2 Receive Synthetic Aperture Focussing Technique (2R-SAFT), which uses one element in the transmit and two consecutive elements in the receive, for achieving high-quality imaging in low complex ultrasound systems. Notably, in F-DwMAS, an additional aperture window function is designed and incorporated to the recently introduced F-DMAS method. The different methods of F-DwMAS, F-DMAS and Delay and Sum (DAS) were compared in terms of Lateral Resolution (LR), Axial Resolution (AR), Contrast Ratio (CR) and contrast-to-noise ratio (CNR) in a simulation study. Results show that the proposed F-DwMAS resulted in improvements of LR by 22.86 % and 25.19 %, AR by 5.18 % and 11.06 % and CR by 152 % and 112.8 % compared to those obtained using F-DMAS and DAS, respectively. However, CNR of F-DwMAS was 12.3 % less compared to DAS, but 103.09 % more than F-DMAS. Hence, it can be concluded that the image quality improved by F-DwMAS compared to DAS and F-DMAS.
10 citations
Cites background from "Design of a low cost ultrasound sys..."
...Several efforts have been made to reduce the cost and complexity of the US system to make it suitable for point of care application in rural and resource-poor settings [1-5]....
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TL;DR: A synthetic aperture-based method, diverging beam with synthetic aperture technique (DB-SAT) that was aimed to not only reduce the ultrasound system complexity, but also provide improved lateral resolution throughout the depth of imaging and at higher frame-rate than that is possible in CFB-LA is developed.
Abstract: Rotation Elastogram (RE) is a 2D spatial distribution map of the estimated local rigid-body rotation undergone by a target when subjected to an external compression, which is one of the recent variants in elastographic imaging A recent study has shown that inclusion-contrast in RE is independent of inclusion-background modulus contrast and thus may be helpful in distinguishing between barely-stiff benign and malignant lesions However, estimation of quality RE requires not only precise axial displacement estimates but also lateral displacement estimates The widely used conventional focused beamforming technique using linear array (CFB-LA) provides better lateral resolution only over the depth of focus, which still results in poorer quality lateral displacement estimates compared to the axial displacement estimates As an alternative to overcome this depth-dependent lateral resolution and obtain an improved lateral resolution, synthetic aperture-based approaches have been proposed in literature Recently, we developed a synthetic aperture-based method, diverging beam with synthetic aperture technique (DB-SAT) that was aimed to not only reduce the ultrasound system complexity, but also provide improved lateral resolution throughout the depth of imaging and at higher frame-rate than that is possible in CFB-LA In this paper, we report the preliminary experimental findings on the use of DB-SAT on RE and compare the resultant image quality against that obtained using often-employed CFB-LA and the synthetic transmit aperture (STA) technique The investigation was done on tissue-mimicking phantoms and using contrast-to-noise ratio (CNR) as the metric for performance evaluation The estimated CNR values from the REs obtained using CFB-LA, STA, and DB-SAT were 269 ± 081, 135 ± 022, and 1471 ± 983, respectively, for inclusion present at 55 mm depth The obtained results clearly demonstrated that the quality of RE can be improved significantly, especially at larger depth, using DB-SAT compared to that obtained using CFB-LA and STA technique
4 citations
01 Jul 2019
TL;DR: The results suggest that using this approach of reference layer of known stiffness yields Young’s modulus values within 10% error compared to the ground truth.
Abstract: It is well-documented in the literature that changes in tissue elasticity are generally correlated with disease condition. In the case of diffuse liver disease, the elasticity of the liver reduces progressively. However, this change does not clearly manifest in conventional ultrasound examinations. Although quasi-static elastography is popular in clinical applications where qualitative assessment of relative tissue stiffness is enough, its potential is relatively underutilized in liver imaging due to the need for quantitative stiffness value. Recently, it was demonstrated that using a reference layer of known stiffness, one could produce quantitative modulus elastograms of the target tissue using quasi-static elastography using simulations and phantom experiments. Here, we examined the performance of this approach on ex-vivo goat liver samples and compare the estimated modulus values to that obtained from indentation measurements. The results suggest that using this approach of reference layer yields Young’s modulus values within 10% error compared to the ground truth.
Cites background from "Design of a low cost ultrasound sys..."
...On the other hand, feasibility to realize quasi-static elastography in low–cost systems is being shown [4, 5]....
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06 Feb 2021
TL;DR: The separated waveforms are sent by two elements together, instead of a single element, and the combination of the methods of independent component analysis and adaptive filtering both are used to extract different components in the received echoes to improve the computational complexity.
Abstract: Purpose: The artificial aperture imaging method owns a good contrast in the data recording and imaging process. However, this method is very time consuming that prevents its practical implementation. Materials and Methods: In this paper, the separated waveforms are sent by two elements together, instead of a single element, and the combination of the methods of independent component analysis and adaptive filtering both are used to extract different components in the received echoes. The obtained result illustrates that the imaging is performed in less time, and the computational complexity of this method is declined. Results: The proposed algorithm has been evaluated on two sets of simulated data and experimental data. The results indicate that the proposed method in the point phantom mode is only 1.5% worse in the resolution than the conventional artificial aperture method. Also, from the contrasting viewpoint, the proposed method has made the CR parameter worse by about 1.34dB than the conventional artificial aperture method. These adverse points of resolution and contrast in the proposed method are neglected than the conventional artificial aperture method because of a slight decrease in image quality than the artificial aperture method. Conclusion: However, the proposed method improves the computational complexity by 45% than the conventional artificial aperture method. As a result, it has brought the researchers closer to the practical implementation of artificial aperture imaging.
References
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TL;DR: It is concluded that the patient's skin should be abraded to reduce impedance, and measurements should be avoided in the first 10 min after electrode placement, to allow satisfactory images.
Abstract: A computer simulation is used to investigate the relationship between skin impedance and image artefacts in electrical impedance tomography. Sets of electrode impedance are generated with a pseudo-random distribution and used to introduce errors in boundary voltage measurements. To simplify the analysis, the non-idealities in the current injection circuit are replaced by a fixed common-mode error term. The boundary voltages are reconstructed into images and inspected. Where the simulated skin impedance remains constant between measurements, large impedances (> 2k omega) do not cause significant degradation of the image. Where the skin impedances 'drift' between measurements, a drift of 5% from a starting impedance of 100 omega is sufficient to cause significant image distortion. If the skin impedances vary randomly between measurements, they have to be less than 10 omega to allow satisfactory images. Skin impedances are typically 100-200 omega at 50 kHz on unprepared skin. These values are sufficient to cause image distortion if they drift over time. It is concluded that the patient's skin should be abraded to reduce impedance, and measurements should be avoided in the first 10 min after electrode placement.
1,976 citations
Book•
05 Dec 2013
TL;DR: Diagnostic Ultrasound Imaging provides a unified description of the physical principles of ultrasound imaging, signal processing, systems and measurements that enable practicing engineers, students and clinical professionals to understand the essential physics and signal processing techniques behind modern imaging systems.
Abstract: Diagnostic Ultrasound Imaging provides a unified description of the physical principles of ultrasound imaging, signal processing, systems and measurements. This comprehensive reference is a core resource for both graduate students and engineers in medical ultrasound research and design. With continuing rapid technological development of ultrasound in medical diagnosis, it is a critical subject for biomedical engineers, clinical and healthcare engineers and practitioners, medical physicists, and related professionals in the fields of signal and image processing. The book contains 17 new and updated chapters covering the fundamentals and latest advances in the area, and includes four appendices, 450 figures (60 available in color on the companion website), and almost 1,500 references. In addition to the continual influx of readers entering the field of ultrasound worldwide who need the broad grounding in the core technologies of ultrasound, this book provides those already working in these areas with clear and comprehensive expositions of these key new topics as well as introductions to state-of-the-art innovations in this field. * Enables practicing engineers, students and clinical professionals to understand the essential physics and signal processing techniques behind modern imaging systems as well as introducing the latest developments that will shape medical ultrasound in the future* Suitable for both newcomers and experienced readers, the practical, progressively organized applied approach is supported by hands-on MATLAB code and worked examples that enable readers to understand the principles underlying diagnostic and therapeutic ultrasound* Covers the new important developments in the use of medical ultrasound: elastography and high-intensity therapeutic ultrasound. Many new developments are comprehensively reviewed and explained, including aberration correction, acoustic measurements, acoustic radiation force imaging, alternate imaging architectures, bioeffects: diagnostic to therapeutic, Fourier transform imaging, multimode imaging, plane wave compounding, research platforms, synthetic aperture, vector Doppler, transient shear wave elastography, ultrafast imaging and Doppler, functional ultrasound and viscoelastic models
1,170 citations
"Design of a low cost ultrasound sys..." refers background in this paper
...Ultrasound (US) is the second most widely used imaging modality in medical diagnostic applications due to its noninvasive, non-ionizing, and real-time imaging capabilities [1]....
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TL;DR: Multi-element synthetic aperture imaging methods suitable for applications with severe cost and size limitations are explored in this article, where each method uses different spatial frequencies and acquisition strategies for imaging, and therefore different sets of active transmit/receive element combinations.
Abstract: Multi-element synthetic aperture imaging methods suitable for applications with severe cost and size limitations are explored. Array apertures are synthesized using an active multi-element receive subaperture and a multi-element transmit subaperture defocused to emulate a single-element spatial response with high acoustic power. Echo signals are recorded independently by individual elements of the receive subaperture. Each method uses different spatial frequencies and acquisition strategies for imaging, and therefore different sets of active transmit/receive element combinations. Following acquisition, image points are reconstructed using the complete data set with full dynamic focus on both transmit and receive. Various factors affecting image quality have been evaluated and compared to conventional imagers through measurements with a 3.5 MHz, 128-element transducer array on different gel phantoms. Multielement synthetic aperture methods achieve higher electronic signal to noise ratio and better contrast resolution than conventional synthetic aperture techniques, approaching conventional phased array performance. >
595 citations
"Design of a low cost ultrasound sys..." refers background or methods in this paper
...to miniaturize US scanner and make it a low-cost device has been an area of active research over the years [3, 4, 5]....
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...Initial efforts were made towards utilizing the concept of SA to reduce the complexity of the PA system [3, 4]....
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TL;DR: A new method for grating and side lobes suppression in ultrasound images is presented, based on an analysis of the phase diversity at the aperture data, which uses phase rather than amplitude information to perform the correction action.
Abstract: A new method for grating and side lobes suppression in ultrasound images is presented. It is based on an analysis of the phase diversity at the aperture data. Two coherence factors, namely the phase coherence factor (PCF) and the sign coherence factor (SCF), are proposed to weight the coherent sum output. Different from other approaches, phase rather than amplitude information is used to perform the correction action.
368 citations
"Design of a low cost ultrasound sys..." refers background or methods in this paper
...Incorporating coherence factor correction has been shown to reduce side lobes and grating lobes, thus resulting in better image quality [14, 16]....
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...Further improvements in image quality is shown by incorporating the Sign Coherence Factor (SCF) weighting in beamforming process [14]....
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...SCF is a type of phase coherence factor calculated by quantifying phases of the aperture data by a single bit [14]....
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TL;DR: By mechanically rocking the array, in a way similar to what is done with an annular array, a 3-D set of images can be collected in the time normally required for a single image.
Abstract: A method for real-time three-dimensional (3-D) ultrasound imaging using a mechanically scanned linear phased array is proposed. The high frame rate necessary for real-time volumetric imaging is achieved using a sparse synthetic aperture beamforming technique utilizing only a few transmit pulses for each image. Grating lobes in the two-way radiation pattern are avoided by adjusting the transmit element spacing and the receive aperture functions to account for the missing transmit elements. The signal loss associated with fewer transmit pulses is minimized by increasing the power delivered to each transmit element and by using multiple transmit elements for each transmit pulse. By mechanically rocking the array, in a way similar to what is done with an annular array, a 3-D set of images can be collected in the time normally required for a single image.
358 citations
"Design of a low cost ultrasound sys..." refers background in this paper
...Several methods have been reported that exploit SA approach on LA technique to gain significant improvement in the frame-rate [9, 10, 11]....
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