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Temporal frequency requirements for tissue velocity imaging of the fetal heart
KTH, School of Technology and Health (STH), Medical Engineering.
KTH, School of Technology and Health (STH), Medical Engineering.
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2011 (English)In: Ultrasound in Obstetrics and Gynecology, ISSN 0960-7692, E-ISSN 1469-0705, Vol. 38, no 4, 413-417 p.Article in journal (Refereed) Published
Abstract [en]

Objectives The high velocity and short duration of myocardial motion requires a high sampling rate to obtain adequate temporal resolution; this issue becomes even more important when taking into consideration the high fetal heart rate. In this study we have established optimal sampling requirements for assessing the duration of various cardiac cycle events and myocardial velocities of the fetal heart using color-coded tissue velocity imaging (TVI). Methods Recordings from 30 fetuses were acquired at an initial frame rate of 180-273 frames/s. All TVI recordings were performed from an apical four-chamber view and stored as cineloops of five to 10 consecutive cardiac cycles for subsequent offline analysis using software enabling a reduction in frame rate. Different components of the myocardial velocity curve, obtained from the basal part of the ventricular septum, were measured at the initial frame rate and compared with their equivalents at gradually decreased frame rates. Results As acquisition frame rate was reduced, there was a marked increase in deviation from the initial values, resulting in an underestimation of all systolic and diastolic velocities. For the measured durations, there was a clear tendency to underestimate isovolumetric contraction and relaxation, and a clear tendency to overestimate ventricular ejection and diastolic E-wave and A-wave. An acceptable <= 5% deviation from the value obtained at the highest frame rate corresponded to measurements obtained at above 150-200 frames/s. Conclusions A high sampling rate of at least 200 frames/s is necessary for adequate reconstruction of TVI data for the fetal heart. Frame rates that are too low result in considerable loss of temporal and velocity information.

Place, publisher, year, edition, pages
2011. Vol. 38, no 4, 413-417 p.
Keyword [en]
fetal echocardiography, frame rate, sampling frequency, temporal frequency requirements, tissue velocity imaging
National Category
Medical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-45593DOI: 10.1002/uog.8872ISI: 000295727400008Scopus ID: 2-s2.0-80052006941OAI: oai:DiVA.org:kth-45593DiVA: diva2:454039
Note
QC 20111104Available from: 2011-11-04 Created: 2011-10-31 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Prenatal Tisse Velocity Imaging of the Heart: A new approach to assess fetal myocardial function
Open this publication in new window or tab >>Prenatal Tisse Velocity Imaging of the Heart: A new approach to assess fetal myocardial function
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The general aim of this thesis has been to evaluate color‐coded tissue velocity imaging (TVI) as an approach to developing a new, non‐invasive assessment method for fetal myocardial function. Such a method could hypothetically give early indications of fetal pathology, as myocardial dysfunction is often the consequence when the circulation tries to adapt to deteriorating situations. This would be beneficial in clinical decision making when evaluating fetal well‐being in a wide range of pregnancy associated conditions, to facilitate risk assessment and to monitor the benefit of therapeutic interventions.

TVI is an ultrasound technique that enables quantification of longitudinal myocardial motion with high temporal resolution, which is essential in the identification of fetal myocardial movements of short duration. Furthermore, the longitudinal motion is mainly determined by subendocardial fibers that usually become abnormal in the very early stages of cardiac dysfunction as they are sensitive to milder degrees of hypoxia. Thus, TVI has the potential to give early indications of impaired fetal myocardial function and hypothetically facilitate the detection of intrauterine hypoxia. Hypoxia is a common phenomenon of many pathological conditions in pregnancy, from which a substantial number of children either die or acquire permanent brain injury during delivery every year.

After having established optimal sampling requirements and ensured an acceptable reproducibility for TVI measurements of the fetal myocardium, normal reference values were determined feasible and sensitive enough to provide insight into maturational changes in myocardial function. This provided a foundation that should enable further investigations and was partly accomplished using the cardiac state diagram (CSD) to accurately time the myocardial events during a cardiac cycle according to the motion shifts of the atrioventricular plane.

The demonstrated results are promising and the general conclusion of this thesis is that TVI contributes to increasing the knowledge and understanding of fetal myocardial function and dysfunction. Used together with CSD this technique has great potential as an assessment method. However, further testing of the clinical potential is needed in larger study populations concerning the pathological or physiological questions at issue, and additional development of the method is required to render the method simple enough to be of potential aid in clinical practice.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xiv, 29 p.
Series
Trita-STH : report, ISSN 1653-3836 ; 2013:3
National Category
Medical Image Processing
Identifiers
urn:nbn:se:kth:diva-120982 (URN)
Public defence
2013-05-07, Sal 4-221, Alfred Nobels allé 12, Huddinge, 13:00 (Swedish)
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Supervisors
Note

QC 20130419

Available from: 2013-04-19 Created: 2013-04-16 Last updated: 2013-04-19Bibliographically approved

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