On the search for good aperiodic binary invertible sequences

Ruprecht, J.; Rupf, M.

doi:10.1109/18.532908

Cited by 47 publications

(18 citation statements)

References 14 publications

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“…The transmission frequency on the linear array was 8.9 MHz and the PRF was 3.5 kHz. Four groups of transmission pulses were programmed into the Siemens Antares using special manufacturer software: uncoded broadband imaging pulses (1 cycle), uncoded narrow band Doppler pulses (4 cycles), phase modulated (PM) code pulses (7 and 13-bit Optimal codes) (Ruprecht and Rupf, 1996), and frequency modulated (FM) code pulses (1.17 and 2.10 µs pseudo-chirps) (Liu and Insana, 2005). The transmission amplitude was the same for all pulses.…”

Section: Ultrasonic Shear Rate Measurementsmentioning

confidence: 99%

Role of Ultrasonic Shear Rate Estimation Errors in Assessing Inflammatory Response and Vascular Risk

Tsou

Liu

Barakat

et al. 2008

Ultrasound in Medicine & Biology

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Atherosclerotic lesions preferentially originate in arterial regions that experience low wall shear stress (WSS) and reversing flow patterns. Therefore, routinely monitoring arterial WSS may help to identify the potential sites of early atherosclerosis. A new non-invasive ultrasonic method implemented with coded excitation techniques was utilized to improve WSS estimation accuracy and precision by providing high spatial and temporal resolution. WSS measurement errors were quantified in a model system by scanning a linearly-varying WSS field (0.3-1.9 Pa) within a flow chamber. A 13-bit Optimal code was found to be most effective in reducing bias and standard deviation in WSS estimates down to ~ 10 % and ~ 8 %. The measurement errors slowly increased with input WSS for all imaging pulses. The expression of endothelial cellular adhesion molecules VCAM-1 and E-selectin was investigated over a similar shear range (0-1.6 Pa) in order to study the impact of relating shear-mediated cellular adhesion molecule (CAM) expression to inaccuracies in WSS measurements. We quantified this influence as the prediction error, which accounts for the ultrasonic measurement errors and the sensitivity of CAM expression within certain shear ranges. The highest prediction errors were observed at WSS < 0.8 Pa, where CAM expression is most responsive to WSS. The results emphasize the importance of minimizing estimation errors, especially within low shear regions. Preliminary 2-D in vivo shear imaging is also presented to provide information about the spatial heterogeneity in arterial WSS distribution.

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Section: Ultrasonic Shear Rate Measurementsmentioning

confidence: 99%

Role of Ultrasonic Shear Rate Estimation Errors in Assessing Inflammatory Response and Vascular Risk

Tsou

Liu

Barakat

et al. 2008

Ultrasound in Medicine & Biology

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“…Binary PM sequences-h(nT, x) for a phase-modulated (PM) sequence has three components. First, a code of length K bits is selected for properties related to orthogonality (matched filter decoding) or low noise amplification (inverse filter decoding) [11]. For example, a K = 13-bit Barker code can be written as the hexadecimal number "00CA".…”

Section: Methodsmentioning

confidence: 99%

“…Unfortunately, the maximum Barker sequence is 13 bits. To achieve high eSNR, longer, suboptimal codes suggested by others [11] also were examined. Optimal codes with long sequences approximate the result ϕ cc [n] ≃ Kδ [n], so that (3) reduces to: (4) For Golay codes, K → 2K.…”

Section: Pulse Compressionmentioning

confidence: 99%

Coded pulse excitation for ultrasonic strain imaging

Liu¹,

Insana

2005

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

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Decorrelation strain noise can be significantly reduced in low echo-signal-to-noise (eSNR) conditions using coded excitation. Large time-bandwidth-product (>30) pulses are transmitted into tissue mimicking phantoms with 2.5-mm diameter inclusions that mimic the elastic properties of breast lesions. We observed a 5-10 dB improvement in eSNR that led to a doubling of the depth of focus for strain images with no reduction of spatial resolution. In high eSNR conditions, coded excitation permits the use of higher carrier frequencies and shorter correlation windows to improve the attainable spatial resolution for strain relative to that obtained with conventional short pulses. This paper summarizes comparative studies of strain imaging in noise-limited conditions obtained by short pulses and four common aperiodic codes (chirp, Barker, suboptimal, and Golay) as a function of attenuation, eSNR and applied strain. Imaging performance is quantified using SNR for displacement (SNR d ), local modulation transfer function (LMTF), and contrast-to-noise ratio for strain (CNR ϵ ). We found that chirp and Golay codes are the most robust for imaging soft tissue deformation using matched filter decoding. Their superior performance is obtained by balancing the need for low-range lobes, large eSNR improvement, and short-code duration.

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“…Thus it is often used as a reference to measure the performance of other types of filters. For example, Rupretcht and Rupf (1996) and Damtie et al (2008) have used it as a reference to quantify the performance of different types of radar waveform and filter pairs. A similar approach is used in this work.…”

Section: Snr Performance Comparison Of Adaptive and Mismatched Pulse mentioning

confidence: 99%

“…However, this mismatched filtering and the references within has an associated SNR losses. Binary phase codes that give minimum possible SNR losses when filtered with their aperiodic inverse filters are available in Rupretcht and Rupf (1996).…”

Section: Introductionmentioning

confidence: 99%

Comparison of the performance of different radar pulse compression techniques in an incoherent scatter radar measurement

Damtie

Lehtinen

2009

Ann. Geophys.

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Abstract. Improving an estimate of an incoherent scatter radar signal is vital to provide reliable and unbiased information about the Earth's ionosphere. Thus optimizing the measurement spatial and temporal resolutions has attracted considerable attention. The optimization usually relies on employing different kinds of pulse compression filters in the analysis and a matched filter is perhaps the most widely used one. A mismatched filter has also been used in order to suppress the undesirable sidelobes that appear in the case of matched filtering. Moreover, recently an adaptive pulse compression method, which can be derived based on the minimum mean-square error estimate, has been proposed. In this paper we have investigated the performance of matched, mismatched and adaptive pulse compression methods in terms of the output signal-to-noise ratio (SNR) and the variance and bias of the estimator. This is done by using different types of optimal radar waveforms. It is shown that for the case of low SNR the signal degradation associated to an adaptive filtering is less than that of the mismatched filtering. The SNR loss of both matched and adaptive pulse compression techniques was found to be nearly the same for most of the investigated codes for the case of high SNR. We have shown that the adaptive filtering technique is a compromise between matched and mismatched filtering method when one evaluates its performance in terms of the variance and the bias of the estimator. All the three analysis methods were found to have the same performance when a sidelobe-free matched filter code is employed.

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On the search for good aperiodic binary invertible sequences

Cited by 47 publications

References 14 publications

Role of Ultrasonic Shear Rate Estimation Errors in Assessing Inflammatory Response and Vascular Risk

Role of Ultrasonic Shear Rate Estimation Errors in Assessing Inflammatory Response and Vascular Risk

Coded pulse excitation for ultrasonic strain imaging

Comparison of the performance of different radar pulse compression techniques in an incoherent scatter radar measurement

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