Mostrando recursos 21 - 39 de 39

  1. Comparative study of different Doppler spectrum estimator implementations

    Madeira, M. M.; Tokhi, M. O.; Ruano, M. Graça
    This paper presents a comparative performance study of some parallel processing architectures aiming at real-time implementation of a blood flow spectral estimator. Three homogeneous and an heterogeneous architecture incorporating transputers, digital signal processors (DSP's) and a vector processor were considered. The performance of these architectures was evaluated and compared in terms of execution times and gradient measurements. Communication times among processing elements were also considered. Analysis of the results revealed that both the DSP's homogeneous architecture and the heterogeneous architecture met real-time requirements; the latter presenting better execution times with less communications time load.

  2. High-performance real-time implementation of a spectral estimator

    Madeira, M. M.; Beltran, L. A. A.; Gonzalez, J. S.; Nocetti, F. G.; Tokhi, M. O.; Ruano, M. Graça
    Doppler blood flow spectral estimation is a common technique of noninvasive cardiovascular disease detection. Blood flow velocity and disturbance may be evaluated by measuring spectral mean frequency and bandwidth respectively. Aiming at minor stenosis diagnosis, parametric spectral estimators may be employed. These models present better spectral resolution than the FFT based ones, at the expense of higher computational burden. Seeking for an efficient real-time implementation of a blood now spectral estimation system, high performance techniques are being investigated. This paper compares the implementation of the Modified Covariance (MC) spectral estimator on two different DSP architectures: the TMS320C40 and the ADSP2016x...

  3. Configurable processing for real-time spectral estimation

    Madeira, M.; Bellis, S.; Ruano, M. Graça; Marnane, W.
    This paper presents a system for real-time implementation of the fourth order Modified Covariance spectral estimator, which, when used in conjunction with pulsed Doppler blood how detectors, has been shown to offer increased sensitivity in atherosclerotic disease detection. The computational burden incurred with the Modified Covariance method is considerably seater than that of the conventional FFT method. This has led to separate studies to evaluate the cost and performance of firstly, transputer/DSP based platforms and secondly application specific custom circuitry, for implementation of the algorithm in real-time. The advantages and disadvantages of each of these different approaches are reviewed in...

  4. High-performance computing for real-time spectral estimation

    Madeira, M. M.; Bellis, S. J.; Beltran, L. A. A.; Gonzalez, J. S.; Nocetti, D. F. G.; Marnane, W. P.; Tokhi, M. O.; Ruano, M. Graça
    This paper presents two separate investigations into the real-time implementation of the modified covariance spectral estimator: one comparing performances on digital signal processors, the TMS320C40, and the recently released ADSP2016x (SHARC); another using application-specific custom circuitry. The advantages and disadvantages of each of these different approaches are reviewed, resulting in the design of a field-programmable gate array/digital signal processor-based high-performance system that combines the hardware and software approaches. In conjunction with pulsed Doppler ultrasound blood-flow detectors, the spectral estimator offers increased sensitivity in the non-invasive detection of arterial disease. (C) 1999 Elsevier Science Ltd. All rights reserved.

  5. High performance parallel-DSP computing in model-based spectral estimation

    Gonzalez, J. S.; Nocetti, D. F. G.; Ruano, M. Graça
    Doppler blood flow spectral estimation is a technique for non-invasive cardiovascular disease detection. Blood flow velocity and disturbance may be determined by measuring the spectral mean frequency and bandwidth, respectively. The work presented here, evaluates a high performance parallel-Doppler Signal Processing architecture (SHARC) for the computation of a parametric model-based spectral estimation method known as the modified covariance algorithm. The model-based method incorporates improvement in frequency resolution when compared with Fast Fourier Transform (FFT)-based methods. However, the computational complexity and the need for real-time response of the algorithm, makes necessary the use of high performance processing in order to fulfil...

  6. Memory management and communication on homogeneous and heterogeneous parallel systems

    Ventura, P.; Ruano, M. Graça; Cunha, J. C. E
    This paper reports a study held on the inter-processor communication performance of homogeneous and heterogeneous parallel systems when different data structure allocation schemes are implemented, regarding internal and/or external processor memory. To evaluate the performance parameters some case-study algorithms were implemented on homogeneous and heterogeneous architectures. Due to algorithm-machine dependency, hardware and software features have to be considered. Where the access to external memory is not efficient, some internal memory buffering methods are analysed. A comparison of the results obtained is presented, enabling establishment of memory management references, regarding the parallel architectures employed. Copyright (C) 2000 IFAC.

  7. Real-time implementation of a Doppler signal spectral estimator using sequential and parallel processing techniques

    Madeira, M. M.; Tokhi, M. O.; Ruano, M. Graça
    Doppler signal spectral estimation has been used to evaluate blood flow parameters in order to diagnose cardiovascular diseases. The modified covariance (MC) method has proved to provide accurate estimation of the two spectral parameters employed in clinical diagnosis, namely mean frequency and bandwidth. The aim of the work reported in this paper is to determine an efficient real-time implementation of the MC spectral estimator by investigating several architectures and implementation methods. A comparative performance analysis of the implementation of the MC algorithm on several homogeneous and heterogeneous architectures incorporating transputers, digital signal processing (DSP) devices and a vector processor is...

  8. Numerical techniques for modeling Doppler ultrasound spectra systems

    Ruano, M. Graça
    Evaluation of blood-flow Doppler ultrasound spectral content is currently performed on clinical diagnosis. Since mean frequency and bandwidth spectral parameters are determinants on the quantification of stenotic degree, more precise estimators than the conventional Fourier transform should be seek. This paper summarizes studies led by the author in this field, as well as the strategies used to implement the methods in real-time. Regarding stationary and nonstationary characteristics of the blood-flow signal, different models were assessed. When autoregressive and autoregressive moving average models were compared with the traditional Fourier based methods in terms of their statistical performance while estimating both spectral...

  9. Time-variable blood flow averaged waveforms

    Leiria, A.; Moura, M. M. M.; Evans, D. H.; Ruano, M. Graça
    The computation of the average of random signals is addressed in this article. These averaging techniques are particularly relevant for Doppler blood flow clinical evaluation and research that usually accesses clinical indicators related to maximum and mean frequency, bandwidth and power variation over time. A novel technique is presented and compared to one previously described in the literature (Kitney and Giddens, "Analysis of blood velocity waveforms by phase shift averaging and autoregressive spectral estimation'', J. Biomech. Eng., 105, 398 - 404, 1983.). While the latter method is an iterative one, which sometimes does not converge, the former is a sequential...

  10. Soft-computing-based car body deformation and EES determination for car crash analysis systems

    Varkonyi-Koczy, A. R.; Rovid, A.; Ruano, M. Graça
    Car body deformation modeling plays a very important role in crash accident analyses, as well as in safe car body design. The determination of the energy absorbed by the deformation and the corresponding energy equivalent speed can be of key importance; however, their precise determination is a very difficult task. Starting from the results of crash tests, intelligent and soft methods offer a way to model the crash process itself, as well as to determine the absorbed energy, the before-crash speed of the car, etc. In this paper, a modeling technique and an intelligent expert system are introduced, which, together,...

  11. A scalable and open source linear positioning system controller

    Medeiros, M. C.; Fernandes, A. J. A.; Teixeira, C. A.; Ruano, M. Graça
    This paper is on the implementation of a dual axis positioning system controller. The system was designed to be used for space-dependent ultrasound signal acquisition problems, such as pressure field mapping. The work developed can be grouped in two main subjects: hardware and software. Each axis includes one stepper motor connected to a driver circuit, which is then connected to a processing unit. The graphical user interface is simple and clear for the user. The system resolution was computed as 127 mu m with an accuracy of 2.44 mu m. Although the target application is ultrasound signal acquisition, the controller...

  12. On the possibility of non-invasive multilayer temperature estimation using soft-computing methods

    Teixeira, C. A.; Pereira, W. C. A.; Ruano, A. E.; Ruano, M. Graça
    Objective and motivation: This work reports original results on the possibility of non-invasive temperature estimation (NITE) in a multilayered phantom by applying soft-computing methods. The existence of reliable non-invasive temperature estimator models would improve the security and efficacy of thermal therapies. These points would lead to a broader acceptance of this kind of therapies. Several approaches based on medical imaging technologies were proposed, magnetic resonance imaging (MRI) being appointed as the only one to achieve the acceptable temperature resolutions for hyperthermia purposes. However, MRI intrinsic characteristics (e. g., high instrumentation cost) lead us to use backscattered ultrasound (BSU). Among the...

  13. On the assessment of time-shift variations from backscattered ultrasound for large temperature changes in biological phantoms

    Teixeira, C. A.; Ruano, M. Graca; Pereira, W. C. A.
    This work reports the assessment of time-shifts (TS) from backscattered ultrasound (BSU) signals when large temperature variations (up to 15 degrees C) were induced in a gel-based phantom. The results showed that during cooling temperature is linear with TS at a rate of approximately 74 ns/degrees C. However during a complete heating/cooling cycle, the relation is highly non-linear. This can be explained by the fact that during cooling the temperature distribution is more uniform. Another problem to report is that TS is very sensitive to external movements.

  14. Influence of temperature variations on the entropy and correlation of the Grey-Level Co-occurrence Matrix from B-Mode images

    Alvarenga, A. V.; Teixeira, C. A.; Ruano, M. Graça; Pereira, W. C. A.
    In this work, the feasibility of texture parameters extracted from B-Mode images were explored in quantifying medium temperature variation. The goal is to understand how parameters obtained from the gray-level content can be used to improve the actual state-of-the-art methods for non-invasive temperature estimation (NITE). B-Mode images were collected from a tissue mimic phantom heated in a water bath. The phantom is a mixture of water, glycerin, agar-agar and graphite powder. This mixture aims to have similar acoustical properties to in vivo muscle. Images from the phantom were collected using an ultrasound system that has a mechanical sector transducer working...

  15. Parallel implementation of a Choi-Williams TFD for Doppler signal analysis

    Cardoso, J. C.; Fish, P. J.; Ruano, M. Graça
    The spectral width and mean frequency of Doppler signals is used to measure and characterise lesion-induced flow disturbance. Conventional methods of spectral estimation based on the Fourier Transform compromise the measurement accuracy since these methods implicitly assume signal stationarity during the signal window under analysis. New methods based on Time-Frequency Distribution (TFD), especially developed for non-stationary signal analysis, are now being introduced which avoid these limitations, at the cost of an increase in the computation burden required. This paper describes the parallel implementation of one TFD method, the Choi-Williams Distribution (CWD), in a transputer platform with 5 processors. The goal...

  16. Adaptive system for blood flow estimation

    Moura, M. M. M.; Leiria, A.; Ruano, M. Graça
    Adaptive estimation of blood flow signals is performed resorting to a framework developed to support research on Doppler blood flow signals' analysis. Real time spectral estimation methods, real time performance evaluation and run-time adjustment of the estimation methods parameters are bound together allowing the system to adapt itself to varying signal characteristic that are caused by physiological reasons.

  17. "Analytic" approximation of Doppler ultrasound blood flow signals

    Moura, Mmm; Leiria, A; Ruano, Mg
    Spectral resolution may be enhanced by complex signal representation ("analytic" signal) of the signals processed. This paper addresses the impact on statistical and computational performance of the autoregressive modified covariance spectral estimator on a clinical scenario, while using, or not, discrete "analytic" signals. The statistical performance results prove that an "analytic" signal representation should be obtained prior to the estimation process. A novel algorithm to compute the complex modified covariance matrix is used to achieve increased computational performance. This approach reduces the estimation error and the execution time by 1% and 30% respectively.

  18. Time, time-frequency and displacement-frequency analysis of embolic signals

    Leiria, A.; Moura, M. M. M.; Ruano, M. Graça; Evans, D. H.
    The characteristics of a new method, the displacement-frequency representation, prompted the study of its use for the analysis of embolic blood flow signals. This paper reports the comparison of displacement-frequency and time-frequency methods with time domain methods, in the characterization of emboli. The study was performed on clinical signals derived from gaseous and particulate embolic events. The results obtained with the different approaches were compared. The conclusions of this study provide encouragement for the use of displacement-frequency domain processing for this kind of analysis.

  19. Adaptive system for blood flow estimation

    Moura, M. M. M.; Leiria, A.; Ruano, M. Graça
    Adaptive estimation of blood flow signals is performed resorting to a framework developed to support research on Doppler blood flow signals' analysis. Real time spectral estimation methods, real time performance evaluation and run-time adjustment of the estimation methods parameters are bound together allowing the system to adapt itself to varying signal characteristics that are caused by physiological reasons.

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