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. © 2017 IEEE.

Arun K. Thittai

Department of Applied Mechanics

Beamforming

COHERENT LIGHT

Image quality

Medical imaging

Synthetic apertures

Ultrasonics

Active elements

DIVERGING BEAMS

FOCAL POINTS

LATERAL RESOLUTION

Linear arrays

LOW-COST ULTRASOUND

SIGN COHERENCE FACTORS

ULTRASOUND SCANNERS

Ultrasonic applications

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Design of a low cost ultrasound system using diverging beams and synthetic aperture approach: Preliminary study

Proceedings - International Symposium on Biomedical Imaging

In this paper, a technique combining Diverging Beam with Synthetic Aperture Technique (DB-SAT) is demonstrated that utilizes only limited number of active elements yet provides better quality images at higher frame rates than possible with Conventional Focused Beamforming (CFB). The DB-SAT has been investigated in simulations and experiments on wire and tissue-mimicking phantoms, and the results are compared with routinely used CFB with Linear Array (CFB-LA). The estimated lateral resolution at the focal point was 0.41 mm and 0.34 mm for CFB-LA and DB-SAT, respectively, in simulations. These were estimated to be 0.78 mm and 0.71 mm, respectively, in experiments. Experimentally computed contrast resolution (contrast-to-noise ratio) for the cyst located at 60 mm depth were 0.50 (1.31 dB) and 0.58 (2.33 dB) for CFB-LA and DB-SAT, respectively. The frame-rate achieved by DB-SAT was 8 times and 2 times higher than that achieved by CFB-LA when transmit sub-apertures had an overlap 0% and 75%, respectively. Therefore, 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. Since there is a reduction in the number of active transmit elements in the case of DB-SAT, it leads to a reduction in the overall system complexity. © 2018 Elsevier B.V.

Diverging beam transmit through limited aperture: A method to reduce ultrasound system complexity and yet obtain better image quality at higher frame rates

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 2.69 ± 0.81, 1.35 ± 0.22, and 14.71 ± 9.83, 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. © 2018 Institute of Physics and Engineering in Medicine.

Physics in Medicine and Biology

Diverging beam with synthetic aperture technique for rotation elastography: Preliminary experimental results

In this work, an adaptive weighting function based on the phase dispersion, namely, Sign Coherence Factor (SCF) is adapted to plane wave ultrasound imaging. SCF weighting is tested on both simulation and experimental data provided by the Plane Wave Imaging Challenge in Medical Ultrasound (PICMUS) organizers. The results demonstrate that the spatial resolution in plane wave imaging can be improved using SCF weighting without compromising the other image quality metrics. Furthermore, the results are compared with conventional delay and sum beamforming algorithm. © 2016 IEEE.

IEEE International Ultrasonics Symposium, IUS

Spatial resolution improvement in Plane Wave Imaging using adaptive Sign Coherence Factor weighting

Journal	Data powered by TypesetProceedings - International Symposium on Biomedical Imaging
Publisher	Data powered by TypesetIEEE Computer Society
ISSN	19457928
Open Access	No