S-sequence encoded synthetic aperture B-scan ultrasound imaging

Zemp, Roger J.; Sampaleanu, Alexander; Harrison, Tyler

doi:10.1109/ultsym.2013.0153

Cited by 14 publications

(6 citation statements)

References 4 publications

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“…our previous work includes simulations that proved this concept [12]. In this work, we show the experimental performance of an s-sequence encoded transmission compared with unencoded transmission and an approximation of Hadamard encoding using a wire phantom and in vivo human carotid as targets…”

Section: Introductionmentioning

confidence: 84%

S-sequence spatially-encoded synthetic aperture ultrasound imaging [Correspondence]

Harrison

Sampaleanu

Zemp

2014

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

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Synthetic transmit aperture (STA) ultrasound imaging offers near-ideal reconstruction across an entire field of view. This performance comes at the cost of SNR compared with scanning using only dynamic receive focusing. SNR may be enhanced by using spatial encoding using a Hadamard sequence. An encoding based on a Hadamard sequence has two main drawbacks: the array must be capable of transmitting a pulse and an inverted pulse at the same time, and the inverted transmission must be symmetrical with respect to the non-inverted transmission. These are often not the case in practice, and thus Hadamard encoding may require twice as many transmission events and special consideration of the inverted waveform. As an alternative, we propose the use of S-sequences, which are similar to Hadamard sequences, but use half the elements and do not require an inverted pulse. This encoding is implemented on a commercial ultrasound system and compared with STA imaging using single-element emissions and Hadamard encoding in terms of SNR and resolution using a point target. We find that the two encodings perform very similarly despite the increased transmit power and doubling of transmit events in our implementation of Hadamard imaging. Both encodings give up to 19 dB signal improvement over single-element STA imaging, while maintaining resolution. Finally, we show sample in vivo human carotid images with all three methods which illustrate the suitability of S-sequence-encoded STA imaging for a clinical setting.

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Section: Introductionmentioning

confidence: 84%

S-sequence spatially-encoded synthetic aperture ultrasound imaging [Correspondence]

Harrison

Sampaleanu

Zemp

2014

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

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“…(16) to (17), the computational complexity has been reduced to 3 / 1 after implementing Eq. (12) or (13) compared with the direct inverse equation (Eq.…”

Section: Discussionmentioning

confidence: 99%

“…Various approaches have been proposed to overcome this low SNR limitation in STA imaging involving encoded transmission schemes [12][13][14][15][16][17][18], which can be generally grouped into two categories: temporal encoding and spatial encoding. Temporal encoding has been applied to STA imaging by using linear frequency modulated (FM) pulse (chirp) to increase the transmitted energy, and therefore to increase the SNR while still retaining axial resolution [12,13].…”

Section: Introductionmentioning

confidence: 99%

“…The SNR of the RF signals can be increased by I times ( I is the total number of active transmitters) compared to the traditional STA [14,15]. S-sequence encoding uses [0, 1] codes to avoid the negative/inverted pulses as used in Hadamard encoding [16,17]. Temporal and spatial encoding techniques can also be combined into spatio-temporal encoding such as HadamardGolay encoding to improve SNR further [18].…”

Section: Introductionmentioning

confidence: 99%

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Pseudoinverse Decoding Process in Delay-Encoded Synthetic Transmit Aperture Imaging

Gong

Kolios

2016

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

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Recently, we proposed a new method to improve the signal-to-noise ratio of the prebeamformed radio-frequency data in synthetic transmit aperture (STA) imaging: the delay-encoded STA (DE-STA) imaging. In the decoding process of DE-STA, the equivalent STA data were obtained by directly inverting the coding matrix. This is usually regarded as an ill-posed problem, especially under high noise levels. Pseudoinverse (PI) is usually used instead for seeking a more stable inversion process. In this paper, we apply singular value decomposition to the coding matrix to conduct the PI. Our numerical studies demonstrate that the singular values of the coding matrix have a special distribution, i.e., all the values are the same except for the first and last ones. We compare the PI in two cases: complete PI (CPI), where all the singular values are kept, and truncated PI (TPI), where the last and smallest singular value is ignored. The PI (both CPI and TPI) DE-STA processes are tested against noise with both numerical simulations and experiments. The CPI and TPI can restore the signals stably, and the noise mainly affects the prebeamformed signals corresponding to the first transmit channel. The difference in the overall enveloped beamformed image qualities between the CPI and TPI is negligible. Thus, it demonstrates that DE-STA is a relatively stable encoding and decoding technique. Also, according to the special distribution of the singular values of the coding matrix, we propose a new efficient decoding formula that is based on the conjugate transpose of the coding matrix. We also compare the computational complexity of the direct inverse and the new formula.

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“…to overcome the low SNR in STA [21][22][23][24][25][26][27][28][29][30][31][32][33]. One of them is synthetic aperture imaging using a virtual source element in transmit and dynamic focusing in receive [22,23].…”

Section: Introductionmentioning

confidence: 99%

Novel ultrasound transmission and reconstruction techniques for synthetic transmit aperture imaging

Gong¹

2021

Preprint

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This dissertation describes ultrasound algorithms developed for synthetic transmit aperture (STA) imaging during the transmission and the image reconstruction stages. Images generated using these algorithms demonstrate image quality enhancement both theoretically and experimentally. The advanced algorithms also improve the application of STA imaging. Due to the single element transmission pattern, the low signal-to-noise ratio is a major limitation for STA imaging. A delay-encoded transmission scheme (DE-STA) was designed in this dissertation to encode all the transmissions. The decoded RF signals were equivalent to the standard STA signals, but with a higher SNR. Improved image qualities were observed under DE-STA transmission in terms of lateral resolution (+28%), peak-signal-to-noise ratio (PSNR, +7 dB) and target contrast-to-noise ratio (CNR, +360%) compared to those acquired with the standard STA mode. The stability of DE-STA was analyzed and verified under various noise levels by the special distribution of the singular values of the encoding matrix through singular value decomposition (SVD) (i.e. all the singular values were the same except for the first one and the last one). A more efficient decoding process was also derived based on pseudo-inversion (PI) and the computation complexity was reduced by 2/3. Speckle and undesired sidelobe signals can reduce the lesion CNR and detectability in ultrasound images. Typically, the CNR can be increased by spatial compounding (SC) or frequency compounding (FC) during reconstruction. We proposed methods to implement a 2-dimentional (2-D) aperture domain filter in the SC/FC processes, referred to as filtered spatial compounding (FSC) and filtered frequency compounding (FFC), for synthetic transmit aperture (STA) imaging. Both techniques reduced the sidelobe interference and provided improved lesion CNR. Consequently, the lesion signal-to-noise ratio (lSNR) in FSC and FFC increased (up to +130%), compared to that in the standard delay-and-sum (DAS) method. This dissertation investigates all these proposed advanced ultrasound algorithms, with the end goal of implementing these methods in STA imaging to extend its application in clinic.

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S-sequence encoded synthetic aperture B-scan ultrasound imaging

Cited by 14 publications

References 4 publications

S-sequence spatially-encoded synthetic aperture ultrasound imaging [Correspondence]

S-sequence spatially-encoded synthetic aperture ultrasound imaging [Correspondence]

Pseudoinverse Decoding Process in Delay-Encoded Synthetic Transmit Aperture Imaging

Novel ultrasound transmission and reconstruction techniques for synthetic transmit aperture imaging

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