The Experts below are selected from a list of 45528 Experts worldwide ranked by ideXlab platform

Chris L De Korte - One of the best experts on this subject based on the ideXlab platform.

  • objective performance testing and quality assurance of Medical Ultrasound equipment
    Ultrasound in Medicine and Biology, 2007
    Co-Authors: J M Thijssen, Gert Weijers, Chris L De Korte
    Abstract:

    There is an urgent need for a measurement protocol and software analysis for objective testing of the imaging performance of Medical Ultrasound equipment from a user's point of view. Methods for testing of imaging performance were developed. Simple test objects were used, which have a long life expectancy. First, the elevational focus (slice thickness) of the transducer was estimated and the in-plane transmit focus was positioned at the same depth. Next, the postprocessing look-up-table (LUT) was measured and linearized. The tests performed were echo level dynamic range (dB), contrast resolution (i.e., gamma of display, number of gray levels/dB) and sensitivity, overall system sensitivity, lateral sensitivity profile, dead zone, spatial resolution and geometric conformity of display. The concept of a computational observer was used to define the lesion signal-to-noise ratio, SNR(L) (or Mahalanobis distance), as a measure for contrast sensitivity. All the measurements were made using digitized images and quantified by objective means, i.e., by image analysis. The whole performance measurement protocol, as well as the quantitative measurements, have been implemented in software. An extensive data-base browser was implemented from which analysis of the images can be started and reports generated. These reports contain all the information about the measurements, such as graphs, images and numbers. The approach of calibrating the gamma by using a linearized LUT was validated by processing simultaneously acquired rf data. The contrast resolution and echo level of the rf data had to be compressed by a factor of two and amplified by a gain factor corresponding to 12 dB. This resulted in contrast curves that were practically identical to those obtained from DICOM image data. The effects of changing the transducer center frequency on the spatial resolution and contrast sensitivity were estimated to illustrate the practical usefulness of the developed approach of quality assurance by measuring objective performance characteristics. The developed methods might be considered as a minimum set of objective quality assurance measures. This set might be used to predict clinical performance of Medical Ultrasound equipment, taking into account the performance at a unique point in space i.e., the coinciding depths of the elevation and in-plane (azimuth) foci. Furthermore, it should be investigated whether the approach might be used to compare objectively various brands of equipment and to evaluate the performance specifications given by the manufacturer. Last but not least, the developed approach can be used to monitor, in a hospital environment, the Medical Ultrasound equipment during its life cycle. The software package may be viewed and downloaded at the website http://www.qa4us.eu.

M.n.s. Swamy - One of the best experts on this subject based on the ideXlab platform.

  • ISCAS - New Spatially Adaptive Wavelet-based Method for the Despeckling of Medical Ultrasound Images
    2007 IEEE International Symposium on Circuits and Systems, 2007
    Co-Authors: Mohammed Imamul Hassan Bhuiyan, M. Omair Ahmad, M.n.s. Swamy
    Abstract:

    Medical Ultrasound images are widely used for diagnostic purposes. A major problem regarding these images is in their inherent corruption by speckle noise in a multiplicative fashion. The presence of speckle noise severely hampers the interpretation and analysis of Medical Ultrasound images. This paper presents a fast and reliable wavelet-based method for reducing the speckle in Medical Ultrasound images. A wavelet-based Bayesian maximum a posteriori denoiser is developed in a homomorphic framework. The wavelet coefficients of the log-transformed signal are modelled by a conditional Gaussian distribution, whereas those of the log-transformed speckle with a Maxwell distribution. The signal variances are obtained by using the local neighbors thus, making the method spatially adaptive. Simulations are performed using synthetically speckled and real Ultrasound images. The results show that the proposed method can perform better than some of the existing methods in terms of the signal-to-noise ratio. Furthermore, the proposed method is fast, and preserves diagnostically important details.

J M Thijssen - One of the best experts on this subject based on the ideXlab platform.

  • objective performance testing and quality assurance of Medical Ultrasound equipment
    Ultrasound in Medicine and Biology, 2007
    Co-Authors: J M Thijssen, Gert Weijers, Chris L De Korte
    Abstract:

    There is an urgent need for a measurement protocol and software analysis for objective testing of the imaging performance of Medical Ultrasound equipment from a user's point of view. Methods for testing of imaging performance were developed. Simple test objects were used, which have a long life expectancy. First, the elevational focus (slice thickness) of the transducer was estimated and the in-plane transmit focus was positioned at the same depth. Next, the postprocessing look-up-table (LUT) was measured and linearized. The tests performed were echo level dynamic range (dB), contrast resolution (i.e., gamma of display, number of gray levels/dB) and sensitivity, overall system sensitivity, lateral sensitivity profile, dead zone, spatial resolution and geometric conformity of display. The concept of a computational observer was used to define the lesion signal-to-noise ratio, SNR(L) (or Mahalanobis distance), as a measure for contrast sensitivity. All the measurements were made using digitized images and quantified by objective means, i.e., by image analysis. The whole performance measurement protocol, as well as the quantitative measurements, have been implemented in software. An extensive data-base browser was implemented from which analysis of the images can be started and reports generated. These reports contain all the information about the measurements, such as graphs, images and numbers. The approach of calibrating the gamma by using a linearized LUT was validated by processing simultaneously acquired rf data. The contrast resolution and echo level of the rf data had to be compressed by a factor of two and amplified by a gain factor corresponding to 12 dB. This resulted in contrast curves that were practically identical to those obtained from DICOM image data. The effects of changing the transducer center frequency on the spatial resolution and contrast sensitivity were estimated to illustrate the practical usefulness of the developed approach of quality assurance by measuring objective performance characteristics. The developed methods might be considered as a minimum set of objective quality assurance measures. This set might be used to predict clinical performance of Medical Ultrasound equipment, taking into account the performance at a unique point in space i.e., the coinciding depths of the elevation and in-plane (azimuth) foci. Furthermore, it should be investigated whether the approach might be used to compare objectively various brands of equipment and to evaluate the performance specifications given by the manufacturer. Last but not least, the developed approach can be used to monitor, in a hospital environment, the Medical Ultrasound equipment during its life cycle. The software package may be viewed and downloaded at the website http://www.qa4us.eu.

Jørgen Arendt Jensen - One of the best experts on this subject based on the ideXlab platform.

  • plane wave imaging challenge in Medical Ultrasound
    Internaltional Ultrasonics Symposium, 2016
    Co-Authors: Herve Liebgott, Jørgen Arendt Jensen, Alfonso Rodriguezmolares, Frederic Cervenansky, Olivier Bernard
    Abstract:

    Plane-Wave imaging enables very high frame rates, up to several thousand frames per second. Unfortunately the lack of transmit focusing leads to reduced image quality, both in terms of resolution and contrast. Recently, numerous beamforming techniques have been proposed to compensate for this effect, but comparing the different methods is difficult due to the lack of appropriate tools. PICMUS, the Plane-Wave Imaging Challenge in Medical Ultrasound aims to provide these tools. This paper describes the PICMUS challenge, its motivation, implementation, and metrics.

  • Medical Ultrasound imaging.
    Progress in biophysics and molecular biology, 2006
    Co-Authors: Jørgen Arendt Jensen
    Abstract:

    The paper gives an introduction to current Medical Ultrasound imaging systems. The basics of anatomic and blood flow imaging are described. The properties of Medical Ultrasound and its focusing are described, and the various methods for two- and three-dimensional imaging of the human anatomy are shown. Systems using both linear and non-linear propagation of Ultrasound are described. The blood velocity can also be non-invasively visualized using Ultrasound and the basic signal processing for doing this is introduced. Examples for spectral velocity estimation, color flow imaging and the new vector velocity images are presented.

  • Potential of coded excitation in Medical Ultrasound imaging.
    Ultrasonics, 2000
    Co-Authors: Thanassis X. Misaridis, Kim Gammelmark, Christian Helms Jørgensen, Niklas Lindberg, Anders H. Thomsen, Morten Høgholm Pedersen, Jørgen Arendt Jensen
    Abstract:

    Improvement in signal-to-noise ratio (SNR) and/or penetration depth can be achieved in Medical Ultrasound by using long coded waveforms, in a similar manner as in radars or sonars. However, the time-bandwidth product (TB) improvement, and thereby SNR improvement is considerably lower in Medical Ultrasound, due to the lower available bandwidth. There is still space for about 20 dB improvement in the SNR, which will yield a penetration depth up to 20 cm at 5 MHz [M. O'Donnell, IEEE Trans. Ultrason. Ferroelectr. Freq. Contr., 39(3) (1992) 341]. The limited TB additionally yields unacceptably high range sidelobes. However, the frequency weighting from the ultrasonic transducer's bandwidth, although suboptimal, can be beneficial in sidelobe reduction. The purpose of this study is an experimental evaluation of the above considerations in a coded excitation Ultrasound system. A coded excitation system based on a modified commercial scanner is presented. A predistorted FM signal is proposed in order to keep the resulting range sidelobes at acceptably low levels. The effect of the transducer is taken into account in the design of the compression filter. Intensity levels have been considered and simulations on the expected improvement in SNR are also presented. Images of a wire phantom and clinical images have been taken with the coded system. The images show a significant improvement in penetration depth and they preserve both axial resolution and contrast.

Manzoor Razaak - One of the best experts on this subject based on the ideXlab platform.

  • Quality evaluation of Medical Ultrasound videos for e-health and telemedicine applications
    2015
    Co-Authors: Manzoor Razaak
    Abstract:

    The advancements in multimedia communication technologies have enabled an increased implementation of telemedicine and e-health application for healthcare services. In parallel, advanced imaging methods have facilitated increasing reliance on Medical images and videos for patient diagnosis. The high data speeds achieved by current communication technologies enables reliable transmission of Medical videos for diagnosis and education purposes in telemedicine applications. The necessary process of video compression, prior to transmission, and communication channel constraints may occasionally impact the quality of the Medical video received after transmission. Thus, to verify the reliability of the received video, quality evaluation is necessary. However, the present approaches used for Medical video quality evaluation have limitations in addressing the contextual requirements of Medical videos. The research work presented in this thesis addresses quality evaluation of Medical Ultrasound videos for telemedicine and e-health applications. The studies presented in the thesis include a subjective quality assessment study of Medical Ultrasound videos compressed via the High Efficiency Video Coding (HEVC) standard and the validation of the performance of state-of-the-art video quality metrics using the subjective cores of Medical experts. Further, the rate-distortion and rate-quality performance of HEVC is analysed for the compression of Medical Ultrasound videos. A video quality metric, Cardiac Ultrasound Quality Index (CUQI), for cardiac Ultrasound videos is proposed that considers the motion and edge features of cardiac videos for quality evaluation. The proposed metric assessment closely agrees with the subjective assessment of Medical experts. Finally, a content-aware packet scheduling approach for transmission of Medical Ultrasound videos over Long Term Evolution (LTE) wireless network is presented. The scheduling approach employs a utility function based on the temporal complexity of the Medical Ultrasound videos and results in improving the received video quality. The research outcomes presented in the thesis indicate that developing quality evaluation approaches according to the contextual requirements of the Medical video modality could enable overcoming the limitations of standard quality evaluation approaches.

  • A Study on Quality Assessment for Medical Ultrasound Video Compressed via HEVC
    IEEE Journal of Biomedical and Health Informatics, 2014
    Co-Authors: Manzoor Razaak, Maria G. Martini, Ketty Savino
    Abstract:

    The quality of experience and quality of service provided in the\nhealthcare sector are critical in evaluating the reliable delivery of\nthe healthcare services provided. Medical images and videos play a major\nrole in modern e-health services and have become an integral part of\nMedical data communication systems. The quality evaluation of Medical\nimages and videos is an essential process, and one of the ways of\naddressing it is via the use of quality metrics. In this paper, we\nevaluate the performance of seven state-of-the-art video quality metrics\nwith respect to compressed Medical Ultrasound video sequences. We study\nthe performance of each video quality metric in representing the\ndiagnostic quality of the video, by evaluating the correlation of each\nmetric with the subjective opinions of Medical experts. The results\nindicate that the visual information fidelity, structural similarity\nindex, and universal quality index metrics show good correlation with\nthe subjective scores provided by Medical experts. The tests also\ninvestigate the performance of the emerging video compression standard,\nhigh-efficiency video coding-HEVC, for Medical Ultrasound video\ncompression. The results show that, using HEVC with the considered\nUltrasound video sequences, a diagnostically reliable compressed\nUltrasound video can be obtained for compression with values of the\nquantization parameter up to 35.