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  • 1.
    Brandberg, Joakim
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Janerot Sjöberg, Birgitta
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Ask, Per
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Increased accuracy of echocardiographic measurement of flow using automated spherical integration of multiple plane velocity vectors1999In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 25, no 2, p. 249-257Article in journal (Refereed)
    Abstract [en]

    The calculation of blood flow in the heart by surface integration of velocity vectors (SIVV) using Doppler ultrasound is independent of the angle. Flow is normally calculated from velocity in a spherical thick shell with its center located at the ultrasound transducer. In a numerical simulation, we have shown that the ratio between minor and major axes of an elliptic flow area substantially influences the accuracy of the estimation of flow in a single scan plane. The accuracy of flow measurements by SIVV can be improved by calculating the mean of the values from more than one scan plane. We have produced an automated computer program that includes an antialiasing procedure. We confirmed an improvement of flow measurements in a pulsatile hydraulic flow model, the 95% confidence interval for single estimations being reduced from 20% to 10% (p < 0.05) using the newly developed software. We think that the SIVV method has important implications for clinical transthoracic echocardiography.

  • 2.
    Chew, Michelle
    et al.
    Departments of Anaesthesia and Intensive Care, Aarhus, Denmark.
    Brandberg, Joakim
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Canard, Peter
    Institute of Experimental Clinical Research, Skejby Sygehus, Aarhus University Hospital, Aarhus, Denmark.
    Sloth, Erik
    Departments of Anaesthesia and Intensive Care, Aarhus, Denmark.
    Ask, Per
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Hasenkam, Michael
    Department of Cardiothoracic and Vascular Surgery, Aarhus, Denmark.
    Doppler flow measurement using surface integration of velocity vectors (Sivv): in vitro validation2000In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 26, no 2, p. 255-262Article in journal (Refereed)
    Abstract [en]

    Blood flow measurement using an improved surface integration of velocity vectors (SIVV) technique was tested in in vitro phantoms. SIVV was compared with true flow (12–116 mL/s) in a steady-state model using two angles of insonation (45° and 60°) and two vessel sizes (internal diameter = 11 and 19 mm). Repeatability of the method was tested at various flow rates for each angle of insonation and vessel. In a univentricular pulsatile model, SIVV flow measured at the mitral inlet was compared to true flow (29–61 mL/s). Correlation was excellent for the 19-mm vessel (r2= 0.99). There was a systematic bias but close limits of agreement (mean ± 2 SD = −24.1% ± 7.6% at 45 °; +16.4% ± 11.0% at 60 °). Using the 11-mm vessel, a quadratic relationship was demonstrated between between SIVV and true flow (r2 = 0.98–0.99), regardless of the angle of insonation. In the pulsatile system, good agreement and correlation were shown (r2 = 0.94, mean ± 2 SD = −4.7 ± 10.1%). The coefficients of variation for repeated SIVV measurements ranged from 0.9% to 10.3%. This method demonstrates precision and repeatability, and is potentially useful for clinical measurements.

  • 3. Chew, Michelle S
    et al.
    Brandberg, Joakim
    Canard, P
    Sloth, E
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Hasenkam, J Michael
    Doppler flow measurement using surface integration of velocity vectors (SIVV): in vitro validation.2000In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 26, no 2, p. 255-262Article in journal (Refereed)
    Abstract [en]

    Blood flow measurement using an improved surface integration of velocity vectors (SIVV) technique was tested in in vitro phantoms. SIVV was compared with true flow (12-116 mL/s) in a steady-state model using two angles of insonation (45 degrees and 60 degrees ) and two vessel sizes (internal diameter = 11 and 19 mm). Repeatability of the method was tested at various flow rates for each angle of insonation and vessel. In a univentricular pulsatile model, SIVV flow measured at the mitral inlet was compared to true flow (29-61 mL/s). Correlation was excellent for the 19-mm vessel (r(2)= 0.99). There was a systematic bias but close limits of agreement (mean +/- 2 SD = -24.1% +/- 7.6% at 45 degrees; +16.4% +/- 11.0% at 60 degrees ). Using the 11-mm vessel, a quadratic relationship was demonstrated between between SIVV and true flow (r(2) = 0.98-0.99), regardless of the angle of insonation. In the pulsatile system, good agreement and correlation were shown (r(2) = 0.94, mean +/- 2 SD = -4.7 +/- 10.1%). The coefficients of variation for repeated SIVV measurements ranged from 0.9% to 10.3%. This method demonstrates precision and repeatability, and is potentially useful for clinical measurements.

  • 4.
    Hedman, Kristofer
    et al.
    Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Nylander, Eva
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Henriksson, Jan
    Karolinska Institute, Sweden.
    Bjarnegård, Niclas
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. County Hospital Ryhov, Sweden.
    Brudin, Lars
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. County Hospital, Sweden.
    Tamas, Eva
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    ECHOCARDIOGRAPHIC CHARACTERIZATION OF THE INFERIOR VENA CAVA IN TRAINED AND UNTRAINED FEMALES2016In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 42, no 12, p. 2794-2802Article in journal (Refereed)
    Abstract [en]

    The aim of the study was to explore the long-and short-axis dimensions, shape and collapsibility of the inferior vena cava in 46 trained and 48 untrained females (mean age: 21 +/- 2 y). Echocardiography in the subcostal view revealed a larger expiratory long-axis diameter (mean: 24 +/- 3 vs. 20 +/- 3 mm, p amp;lt; 0.001) and short-axis area (mean: 5.5 +/- 1.5 vs. 4.7 +/- 1.4 cm(2), p = 0.014) in trained females. IVC shape (the ratio of short-axis major to minor diameters) and the relative decrease in IVC dimension with inspiration were similar for the two groups. The IVC long-axis diameter reflected short-axis minor diameter and was correlated to maximal oxygen uptake (r = 0.52, p amp;lt; 0.01). In summary, the results indicate that trained females have a larger IVC similar in shape and respiratory decrease in dimensions to that of untrained females. The long-axis diameter corresponded closely to short-axis minor diameter and, thus, underestimates maximal IVC diameter. (E-mail: kristofer.hedman@liu.se) (C) 2016 The Authors. Published by Elsevier Inc. on behalf of World Federation for Ultrasound in Medicine amp; Biology.

  • 5.
    Janerot-Sjöberg, Birgitta
    et al.
    Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    von Schmalensee, Niklas
    Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Schreckenberger, Anja
    Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Richter, Arina
    Östergötlands Läns Landsting, Heart Centre, Department of Cardiology.
    Brandt, Einar
    Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Kirkhorn, Johan
    Norwegian University of Science and Technology, Trondheim, Norway.
    Wilkenshoff, Ursula
    Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Influence of respiration on myocardial signal intensity2001In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 27, no 4, p. 473-479Article in journal (Refereed)
    Abstract [en]

    Echocardiographic quantification of myocardial perfusion after IV contrast is possible, based on the intensity of the received intermittent second harmonic signal. To investigate the influence of respiration on the intensity of myocardial signals, we examined nine patients with normal coronary angiograms. At baseline, end-expiratory and end-inspiratory images were obtained in broadband radiofrequency (RF) and intermittent second harmonic modes, the latter repeated during IV contrast at rest and at peak stress. In mid-septum at baseline, end-inspiratory integrated backscatter intensity was 4 dB higher (p < 0.05, both in second harmonic and fundamental domains) than end-expiratory intensity. In second harmonic imaging, contrast increased signal intensity by 4 dB (p < 0.05) in six examined segments, but the increase in the midseptal region (2 dB) was not significant. Contrast-enhanced intensity at end-inspiration was higher (3 dB, p < 0.01) than baseline intensity at end-expiration. We conclude that the increase in myocardial signal intensity during inspiration may resemble the contrast effect in intermittent second harmonic mode. The respiratory variation persists after contrast and may mask or exaggerate the effect of myocardial contrast.

  • 6.
    Peterson, Gunnel
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Physiotherapy. Linköping University, Faculty of Medicine and Health Sciences. Uppsala University, Sweden.
    Nilsson, David
    Umeå University, Sweden.
    Peterson, Simon
    Linköping University, Department of Medical and Health Sciences, Division of Physiotherapy. Linköping University, Faculty of Medicine and Health Sciences.
    Dedering, Asa
    Karolinska Institute, Sweden; Karolinska University Hospital, Sweden.
    Trygg, Johan
    Umeå University, Sweden.
    Wallman, Thorne
    Uppsala University, Sweden.
    Peolsson, Anneli
    Linköping University, Department of Medical and Health Sciences, Division of Physiotherapy. Linköping University, Faculty of Medicine and Health Sciences.
    CHANGES IN DORSAL NECK MUSCLE FUNCTION IN INDIVIDUALS WITH CHRONIC WHIPLASH-ASSOCIATED DISORDERS: A REAL-TIME ULTRASOUND CASE-CONTROL STUDY2016In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 42, no 5, p. 1090-1102Article in journal (Refereed)
    Abstract [en]

    Impaired neck muscle function leads to disability in individuals with chronic whiplash-associated disorder (WAD), but diagnostic tools are lacking. In this study, deformations and deformation rates were investigated in five dorsal neck muscles during 10 arm elevations by ultrasonography with speckle tracking analyses. Forty individuals with chronic WAD (28 women and 12 men, mean age = 37 y) and 40 healthy controls matched for age and sex were included. The WAD group had higher deformation rates in the multifidus muscle during the first (p &lt; 0.04) and 10th (only women, p &lt; 0.01) arm elevations compared with the control group. Linear relationships between the neck muscles for deformation rate (controls: R-2 = 0.24-0.82, WAD: R-2 = 0.05-0.74) and deformation of the deepest muscles (controls: R-2 = 0.61-0.32, WAD: R-2 = 0.15-0.01) were stronger for women in the control group versus women with WAD, indicating there is altered interplay between dorsal neck muscles in chronic WAD. (C) 2016 World Federation for Ultrasound in Medicine & Biology.

  • 7.
    Pislaru, Cristina
    et al.
    Departments of Cardiology University of Leuven, Leuven, Belgium.
    D'hooge, Jan
    Department of Electrical Engineering, Medical Image Computing, University of Leuven, Leuven, Belgium.
    Pislaru, Sorin V
    Departments of Cardiology University of Leuven, Leuven, Belgium.
    Brandt, Einar
    Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Cipic, Roberg
    Department of Cardiology, Klinikum Innenstadt, University of Munich, Munich, Germany.
    Angermann, Christiane E
    Department of Cardiology, Klinikum Innenstadt, University of Munich, Munich, Germany.
    Van de Werf, Frans
    Departments of Cardiology University of Leuven, Leuven, Belgium.
    Bijnens, Bart
    Departments of Cardiology University of Leuven, Leuven, Belgium.
    Herregods, Marie-Christine
    Departments of Cardiology University of Leuven, Leuven, Belgium.
    Sutherland, George R
    Departments of Cardiology University of Leuven, Leuven, Belgium.
    Is there a change in myocardial nonlinearity during the cardiac cycle?2001In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 27, no 3, p. 389-398Article in journal (Refereed)
    Abstract [en]

    The distortion of a sound wave during propagation results in progressive transfer of the energy from fundamental to higher harmonics, and is dependent on the nonlinearity of the medium. We studied if relative changes in acoustical nonlinearity occur in healthy myocardium during the cardiac cycle. Radiofrequency data were acquired from transthoracic echocardiography (2.5 and 3.5 MHz), parasternal long axis view, from five dogs and nine healthy volunteers. Integrated backscatter was calculated after filtering for fundamental (FIB) and second harmonic frequencies (SHIB), from a region in the posterior myocardial wall. The results suggest that there is little difference between the SHIB and FIB, although there were large variations between individuals. The maximal changes in nonlinearity, as estimated by SHIB/FIB ratio, mostly occurred during systole. SHIB presented similar cyclic variation with FIB (p = NS). Further studies are necessary to separate the role of myocardial nonlinearity, attenuation, propagating distance, or acoustical properties of the blood. The results are important in further tissue characterization studies employing second harmonic data.

  • 8.
    Ressner, Marcus
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Jansson, Tomas
    Lund University.
    Cedefamn, Jonny
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Janerot Sjöberg, Birgitta
    Linköping University, Department of Medicine and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Contrast Biases the Autocorrelation Phase Shift Estimation in Doppler Tissue Imaging2009In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 35, no 3, p. 447-457Article in journal (Refereed)
    Abstract [en]

    Quantitative assessment of regional myocardial function at rest and during stress with Doppler tissue imaging (DTI) plays an important role in daily routine echocardiography. However, reliable visual analysis is largely dependent on image quality and adequate border delineation, which still remains a challenge in a significant number of patients. In this respect, an ultrasound contrast agent (UCA) is often used to improve visualization in patients with suboptimal image quality. The knowledge of how DTI measurements will be affected by UCA present in the tissue is therefore of significant importance for an accurate interpretation of local myocardial motion. The aim of this paper was to investigate how signal contribution from UCA and nonlinear wave propagation influence the performance of the autocorrelation phase shift estimator used for DTI applications. Our results are based on model experiments with a clinical 2-D grayscale scanner and computational simulations or the DTI velocity estimator for synthetically-derived pulses, simulated bubble echoes and experimentally-sampled RF data of transmitted pulses and backscattered contrast echoes. The results show that destruction of UCA present in the tissue will give rise to an apparent bidirectional velocity bias of individual velocity estimates, but that spatial averaging of individual velocity measurements within a region-of-interest will result in a negative bias (away from the transducer) of the estimated mean or mean peak velocity. The UCA destruction will also have a significant impact on the measured integrated mean velocity over time, i.e., displacement. To achieve improved visualization with UCA during DTI-examinations, we either recommend that it is performed at low acoustic powers, mechanical index <= 0.3, thereby minimizing the effects from bubble rupture, or that each Doppler pulse package is preceded by a destruction burst similar to "Flash imaging" to clear the target area of contrast microbubbles.

  • 9. Rydén Ahlgren, Åsa
    et al.
    Åstrand, Håkan
    Sandgren, Thomas
    Vernersson, Einar
    Sonesson, Björn
    Länne, Toste
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Vascular surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Dynamic behaviour of the common femoral artery: Age and gender of minor importance2001In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 27, no 2, p. 181-188Article in journal (Refereed)
    Abstract [en]

    The distensibility of elastic arteries has been extensively studied, while studies of muscular arteries are sparse. The influences of age and gender on the mechanical properties of the common femoral artery (CFA) were studied. The pulsatile diameter changes of the CFA were noninvasively measured using echo-tracking sonography in 173 healthy volunteers (95 females, 78 males, range 7-81 years). In combination with blood pressure measurements, stiffness (▀) and pressure strain elastic modulus (Ep) were calculated. Neither ▀ nor Ep was related to age or gender and a considerable interindividual variation was present. The CFA diameter increased with age. In conclusion, the distensibility of this muscular artery is not clearly affected by age or gender, although the diameter increases with age. This indicates remodelling of the arterial wall and an impact of vascular smooth muscles on long-term wall mechanics. Thus, there appear to be fundamental differences in the dynamic behaviour of the common femoral artery when compared to elastic arteries, such as the aorta and the common carotid artery. (E-mail:asa.ryden-ahlgren@klinfys.mas.lu.se) Copyright

  • 10.
    Sommerlade, Linda
    et al.
    University of Freiburg, Germany .
    Schelter, Bjoern
    University of Freiburg, Germany.
    Timmer, Jens
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Reinhard, Matthias
    University of Freiburg, Germany .
    GRADING OF DYNAMIC CEREBRAL AUTOREGULATION WITHOUT BLOOD PRESSURE RECORDINGS: A SIMPLE DOPPLER-BASED METHOD2012In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 38, no 9, p. 1546-1551Article in journal (Refereed)
    Abstract [en]

    Transcranial Doppler sonography allows for noninvasive assessment of dynamic cerebral autoregulation. A wider clinical use of this approach has been hampered by the need for continuous arterial blood pressure (ABP) measurements. We describe a new method of a pure Doppler signal based estimation of dynamic autoregulation using heart rate (HR) and cerebral blood flow velocity (CBFV) information. The phase between these two signals was assessed from 0.1 Hz oscillations induced by regular breathing. We compared this new approach with the standard method (phase between ABP and CBFV oscillations) in 93 patients with unilateral severe carotid artery obstruction. On a group level, the phase HR-CBFV differed significantly between ipsi- and contralateral sides (p = 0.024) and correlated significantly with the standard phase ABP-CBFV (r = 0.369, p andlt; 0.001). The proposed method can, thus, detect impaired dynamic autoregulation in occlusive carotid artery disease using a single Doppler probe.

  • 11.
    Walker, Andrew
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Henriksen, Egil
    Centre for Clinical Research, Central Hospital, Västerås, Sweden.
    Ringqvist, Ivar
    Department of Clinical Physiology, Central Hospital, Västerås, Sweden.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    A Rotating Cylinder Phantom for Flow and Tissue Color Doppler Testing2009In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 35, no 11, p. 1892-1898Article in journal (Refereed)
    Abstract [en]

    Ultrasound Doppler using two-dimensional (2D) techniques is commonly used to study blood flow and myocardial tissue motion. This use includes measurement of velocity and time intervals, often in relation to the electrocardiogram (ECG) signal. 2D Doppler is frequently considered a real-time technique but in reality the acquisition time can be as long as 200 ms per image. We have developed a test-phantom using a rotating cylinder to simulate blood flow and tissue motion in a whole sector or space angle to evaluate velocity and timing characteristics.The phantom can produce constant velocities for velocity testing, as well as accelerating movement for testing the timing characteristics of ultrasound systems. Our investigation shows that the cylinder phantom is especially suitable for timing measurements in 2D Doppler imaging and that time delays between the Dopplersignals and the ECG signal exist in the tested ultrasound system.

  • 12.
    Walker, Andrew
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Olsson, Eva
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Wranne, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Ringqvist, Ivar
    Centrallasarettet i Västerås.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Accuracy of spectral Doppler flow and tissue velocity measurements in ultrasound systems2004In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 30, no 1, p. 127-132Article in journal (Refereed)
    Abstract [en]

    Blood and tissue velocity are measured and analysed in cardiac, vascular and other applications of diagnostic ultrasound (US). An error in system calibration is a potential risk for misinterpretation of the measurements. To determine the accuracy in velocity calibration, we tested three common commercial US systems using a Doppler string phantom. We tested pulsed and continuous-wave Doppler modes for velocities relevant to both cardiac blood flow and tissue-velocity estimation. The US systems were tested with settings and transducers commonly used in cardiac applications. One system consistently overestimated velocity by about 5%, whereas the other two systems were quite accurate in velocity estimation. These findings emphasize the importance of continuous quality control of US equipment.

  • 13.
    Walker, Andrew
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Olsson, Eva
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Wranne, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Ringqvist, Ivar
    Västerås.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering.
    Time delays in ultrasound systems can result in fallacious measurements.2002In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 28, p. 259-263Article in journal (Refereed)
    Abstract [en]

    Even short time delays (less than 30 ms) in cardiac motion pattern may have clinical relevance. These delays can be measured with echocardiography, using techniques such as flow and tissue Doppler and M-mode together with external signals (e.g., ECG and phonocardiography). If one or more of these signals are delayed in relation to the other signals (asynchronous), an incorrect definition of cardiac time intervals can occur, the consequence of which is invalid measurement. To determine if this time delay in signal processing is a problem, we tested three common ultrasound (US) systems using the ECG as the reference signal. We used a digital ECG simulator and a Doppler string phantom to obtain test signals for flow and tissue pulsed Doppler, M-mode, phonocardiography, auxiliary and ECG signals. We found long time delays of up to 90 ms in one system, whereas delays were mostly short in the two other systems. The time delays varied relative to system settings. Consequently, to avoid these errors, precise knowledge of the characteristics of the system being used is essential.

    Federation for Ultrasound in Medicine & Biology.

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