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Proceedings ArticleDOI

Low Complexity 3D Ultrasound Imaging Using Synthetic Aperture Sequential Beamforming

TL;DR: This work extends SASB to 3D imaging and proposes two schemes to reduce its complexity, reducing the number of elements in both transmit and receive and implementing separable beamforming in the second stage.
Abstract: Synthetic aperture sequential beamforming (SASB) is a technique to achieve range-independent resolution in 2D images with lower computational complexity compared to synthetic aperture ultrasound (SAU). It is a two stage process, wherein the first stage performs fixed-focus beamforming followed by dynamic-focus beamforming in the second stage. In this work, we extend SASB to 3D imaging and propose two schemes to reduce its complexity:(1) reducing the number of elements in both transmit and receive and (2) implementing separable beamforming in the second stage. Our Field-II simulations demonstrate that reducing transmit and receive apertures to 32×32 and 16×16 elements, respectively, and using separable beamforming reduces 3D SASB computational complexity by 15× compared to the 64×64 aperture case with almost no loss in image quality. We also describe a hardware architecture for 3D SASB that performs first-stage beamforming in the scan head, reducing the amount of data that must be transferred for offchip processing in the second stage beamformer by up to 256×. We describe an implementation approach for the second stage that performs an optimized in-place update for both steps of separable beamforming and is well suited for GPU.
Citations
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Journal ArticleDOI
TL;DR: The proposed multiple-firing sparse array method increases the volume rate from 11 to 45 volumes per second, without increasing computational complexity at the front-end and with only a small degradation in imaging quality.
Abstract: Three-dimensional (3-D) ultrasound imaging is a promising modality for many medical applications. Unfortunately, it generates voluminous data in the front end, making it unattractive for high-volume-rate portable medical applications. We apply synthetic aperture sequential beamforming (SASB) to greatly compress the front-end receive data. Baseline 3-D SASB has a low volume rate, because subapertures fire one by one. In this paper, we propose to increase the volume rate of 3-D SASB without degrading imaging quality through: 1) transmitting and receiving simultaneously with four subapertures and 2) using linear chirps as the excitation waveform to reduce interference. We design four linear chirps that operate on two overlapped frequency bands with chirp pairs in each band having opposite chirp rates. Direct implementation of this firing scheme results in grating lobes. Therefore, we design a sparse array that mitigates the grating lobe levels through optimizing the locations of transducer elements in the bin-based random array. Compared with the baseline 3-D SASB, the proposed method increases the volume rate from 8.56 to 34.2 volumes/s without increasing the front-end computation requirement. Field-II-based cyst simulations show that the proposed method achieves imaging quality comparable with baseline 3-D SASB in both shallow and deep regions.

7 citations


Cites background or methods from "Low Complexity 3D Ultrasound Imagin..."

  • ...In the STSR1 and STSR2 schemes, each subaperture only receives signals transmitted by itself....

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  • ...The number of computations in the second beamforming stage of MTMR2 and MTMRS is higher compared to STSR2 due to the extra delay paths, as described in Section III....

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  • ...Compared to a contemporary 3D SASB method [4], which achieves a volume rate of 11....

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  • ...Since the number of subapertures to generate one imaging volume is 676 for both cases, the computational complexity of MTMR in the first beamforming stage is the same as that of STSR2....

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  • ...The receive subaperture for each scheme is as follows: • STSR2: uniformly distributed array consisting of 16×16 active receive elements with 2λ spacing....

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Journal ArticleDOI
TL;DR: In this article , a two-point ray tracing method based on Fermat's principle is proposed for fast calculation of the travel times in the presence of a layered aberrator in front of the ultrasound probe.
Abstract: In a recent study, we proposed a technique to correct aberration caused by the skull and reconstruct a transcranial B-mode image with a refraction-corrected synthetic aperture imaging (SAI) scheme. Given a sound speed map, the arrival times were calculated using a fast marching technique (FMT), which solves the Eikonal equation and, therefore, is computationally expensive for real-time imaging. In this article, we introduce a two-point ray tracing method, based on Fermat’s principle, for fast calculation of the travel times in the presence of a layered aberrator in front of the ultrasound probe. The ray tracing method along with the reconstruction technique is implemented on a graphical processing unite (GPU). The point spread function (PSF) in a wire phantom image reconstructed with the FMT and the GPU implementation was studied with numerical synthetic data and experiments with a bone-mimicking plate and a sagittally cut human skull. The numerical analysis showed that the error on travel times is less than 10% of the ultrasound temporal period at 2.5 MHz. As a result, the lateral resolution was not significantly degraded compared with images reconstructed with FMT-calculated travel times. The results using the synthetic, bone-mimicking plate, and skull dataset showed that the GPU implementation causes a lateral/axial localization error of 0.10/0.20, 0.15/0.13, and 0.26/0.32 mm compared with a reference measurement (no aberrator in front of the ultrasound probe), respectively. For an imaging depth of 70 mm, the proposed GPU implementation allows reconstructing 19 frames/s with full synthetic aperture (96 transmission events) and 32 frames/s with multiangle plane wave imaging schemes (with 11 steering angles) for a pixel size of $200~\mu \text{m}$ . Finally, refraction-corrected power Doppler imaging is demonstrated with a string phantom and a bone-mimicking plate placed between the probe and the moving string. The proposed approach achieves a suitable frame rate for clinical scanning while maintaining the image quality.

4 citations

Journal ArticleDOI
TL;DR: In this article , a two-point ray tracing method based on Fermat's principle is proposed for fast calculation of the travel times in the presence of a layered aberrator in front of the ultrasound probe.
Abstract: In a recent study, we proposed a technique to correct aberration caused by the skull and reconstruct a transcranial B-mode image with a refraction-corrected synthetic aperture imaging (SAI) scheme. Given a sound speed map, the arrival times were calculated using a fast marching technique (FMT), which solves the Eikonal equation and, therefore, is computationally expensive for real-time imaging. In this article, we introduce a two-point ray tracing method, based on Fermat’s principle, for fast calculation of the travel times in the presence of a layered aberrator in front of the ultrasound probe. The ray tracing method along with the reconstruction technique is implemented on a graphical processing unite (GPU). The point spread function (PSF) in a wire phantom image reconstructed with the FMT and the GPU implementation was studied with numerical synthetic data and experiments with a bone-mimicking plate and a sagittally cut human skull. The numerical analysis showed that the error on travel times is less than 10% of the ultrasound temporal period at 2.5 MHz. As a result, the lateral resolution was not significantly degraded compared with images reconstructed with FMT-calculated travel times. The results using the synthetic, bone-mimicking plate, and skull dataset showed that the GPU implementation causes a lateral/axial localization error of 0.10/0.20, 0.15/0.13, and 0.26/0.32 mm compared with a reference measurement (no aberrator in front of the ultrasound probe), respectively. For an imaging depth of 70 mm, the proposed GPU implementation allows reconstructing 19 frames/s with full synthetic aperture (96 transmission events) and 32 frames/s with multiangle plane wave imaging schemes (with 11 steering angles) for a pixel size of $200~\mu \text{m}$ . Finally, refraction-corrected power Doppler imaging is demonstrated with a string phantom and a bone-mimicking plate placed between the probe and the moving string. The proposed approach achieves a suitable frame rate for clinical scanning while maintaining the image quality.

4 citations

Proceedings ArticleDOI
31 Oct 2017
TL;DR: The proposed multiple-firing sparse array method increases the volume rate from 11 to 45 volumes per second, without increasing computational complexity at the front-end and with only a small degradation in imaging quality.
Abstract: Synthetic aperture sequential beamforming (SASB) is a two-stage process, with fixed transmit and receive beamforming in the first stage, followed by dynamic receive beamforming in the second stage. Compared to 3D synthetic aperture ultrasound (SAU) imaging, 3D SASB has low computational complexity at the front-end, making it suitable for portable devices. Unfortunately, 3D SASB has low volume rate since typically only one subaperture transmits and receives at a time. To increase the volume rate, we propose to transmit and receive multiple subapertures simultaneously. A straight-forward implementation of such a scheme, for even four simultaneous firings, results in an increase in grating lobe and sidelobe levels. To address these issues, we use bin-based random sparse array to reduce the grating lobes caused by the three other transmits, and then optimize the locations of the active receive elements to minimize the sidelobe. Compared to a contemporary 3D SASB method, the proposed multiple-firing sparse array method increases the volume rate from 11 to 45 volumes per second, without increasing computational complexity at the front-end and with only a small degradation in imaging quality.

3 citations


Cites background or methods from "Low Complexity 3D Ultrasound Imagin..."

  • ...Compared to a contemporary 3D SASB method [4], which achieves a volume rate of 11....

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  • ...To increase the volume rate, we proposed a version of STSR where the subaperture shifts by 2 elements, referred to as STSR2 [4]....

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  • ...01× 10 1 [4]....

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  • ...In our previous work [4], we extended SASB from 2D to 3D...

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  • ...This increase in complexity can be partially mitigated by reducing the number of active receive elements in a subaperture through increasing the spacing between the active receive elements from λ to 2λ [4]....

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References
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Journal ArticleDOI
TL;DR: A method for simulation of pulsed pressure fields from arbitrarily shaped, apodized and excited ultrasound transducers is suggested, which relies on the Tupholme-Stepanishen method for calculating pulsing pressure fields and can also handle the continuous wave and pulse-echo case.
Abstract: A method for simulation of pulsed pressure fields from arbitrarily shaped, apodized and excited ultrasound transducers is suggested. It relies on the Tupholme-Stepanishen method for calculating pulsed pressure fields, and can also handle the continuous wave and pulse-echo case. The field is calculated by dividing the surface into small rectangles and then Summing their response. A fast calculation is obtained by using the far-field approximation. Examples of the accuracy of the approach and actual calculation times are given. >

2,340 citations


"Low Complexity 3D Ultrasound Imagin..." refers methods in this paper

  • ...This “footprint” method is highly memory efficient and is well-suited for GPU implementation....

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Journal ArticleDOI
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

Journal ArticleDOI
TL;DR: The objective is to improve lateral resolution and obtain a more depth independent resolution compared to conventional ultrasound imaging in synthetic aperture sequential beamforming.

110 citations


Additional excerpts

  • ...The process is repeated for each subaperture one by one, covering the entire imaging area of interest [10]....

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Proceedings ArticleDOI
01 Nov 2008
TL;DR: A synthetic aperture focusing (SAF) technique denoted synthetic aperture sequential beamforming (SASB) suitable for 2D and 3D imaging is presented to improve and obtain a more range independent lateral resolution compared to conventional dynamic receive focusing (DRF) without compromising frame rate.
Abstract: A synthetic aperture focusing (SAF) technique denoted synthetic aperture sequential beamforming (SASB) suitable for 2D and 3D imaging is presented The technique differ from prior art of SAF in the sense that SAF is performed on pre-beamformed data contrary to channel data The objective is to improve and obtain a more range independent lateral resolution compared to conventional dynamic receive focusing (DRF) without compromising frame rate SASB is a two-stage procedure using two separate beamformers First a set of B-mode image lines using a single focal point in both transmit and receive is stored The second stage applies the focused image lines from the first stage as input data The SASB method has been investigated using simulations in Field II and by off-line processing of data acquired with a commercial scanner The performance of SASB with a static image object is compared with DRF For the lateral resolution the improvement in FWHM equals a factor of 2 and the improvement at -40 dB equals a factor of 3 With SASB the resolution is almost constant throughout the range The resolution in the near field is slightly better for DRF A decrease in performance at the transducer edges occur for both DRF and SASB, but is more profound for SASB

68 citations


"Low Complexity 3D Ultrasound Imagin..." refers background or methods in this paper

  • ...Along the axial direction, the number of wavefronts contributing to an imaging point increases with depth, which helps maintain good lateral resolution, allowing SASB to achieve range-independent resolution [9]....

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  • ...In SASB, the beamforming process is divided into two stages: a fixed transmit and receive beamforming that results in a single scanline, followed by dynamic receive beamforming [9]....

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Proceedings ArticleDOI
23 Feb 2013
TL;DR: Sonic Millip3De can enable 3D ultrasound with a fully sampled 128×96 transducer array within a 16W full-system power budget and will meet a 5W safe power target by the 11nm node.
Abstract: Three-dimensional (3D) ultrasound is becoming common for non-invasive medical imaging because of its high accuracy, safety, and ease of use. Unlike other modalities, ultrasound transducers require little power, which makes hand-held imaging platforms possible, and several low-resolution 2D devices are commercially available today. However, the extreme computational requirements (and associated power requirements) of 3D ultrasound image formation has, to date, precluded hand-held 3D capable devices. We describe the Sonic Millip3De, a new system architecture and accelerator for 3D ultrasound beamformation-the most computationally intensive aspect of image formation. Our three-layer die-stacked design features a custom beamsum accelerator that employs massive data parallelism and a streaming transform-select-reduce pipeline architecture enabled by our new iterative beamsum delay calculation algorithm. Based on RTL-level design and floorplanning for an industrial 45nm process, we show Sonic Millip3De can enable 3D ultrasound with a fully sampled 128×96 transducer array within a 16W full-system power budget (400× less than a conventional DSP solution) and will meet a 5W safe power target by the 11nm node.

53 citations