DOPPLER ULTRASOUND in Pregnancy

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DOPPLER ULTRASOUND in Pregnancy Dr. Mohammed Abdalla Egypt, Domiat Hospital

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Doppler History First use of Doppler ultrasonography to study flow velocity in the fetal umbilical artery was reported in 1977

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Doppler History Fitzgerald & Drumm. Umbilical artery studies 1977BMJ Eik-Nes et al. Fetal aortic velocimetry : Dupplexscanner 1980 Lancet Campbell et al. Utero-placental circulation: Dupplex scanner 1983 Lancet Wladimiroff et al. MCA / UA PI ratio 1987 OG Kiserud et al. Ductus venosus velocimetry 1991Lancet

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Basic principalsEchoes from stationary tissues are the same from pulse to pulse. Echoes from moving objects exhibit slight differences in the time for the signal to be returned to the receiver. These differences can measured as phase shift from which the Doppler frequency is obtained. .

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T1 : time of omitted signal . T2 : time of returned signal . T2 – T1 = time difference or phase shift . from phase shift the Doppler frequency is obtained. AS TIME DIFFERENCE DECREASE THE DOPPLER FREQUENCY INCREASE.

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pulse repetition frequency(T2 –T1) phase shift with known beam / flow angle can calculate flow velocity .T1T2

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Basic PrincipalsThe time difference or phase shift are then proceeded to produce either colorflow display or a Doppler sonogram

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Basic Principals‘Doppler frequency’ is obtained by measuring the time difference for the signal to be returned when reflected from moving scatterers . Doppler frequency increase if: flow velocity increased . beam is more aligned to the direction of flow. higher transducer frequency is used.

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(the angle q between the beam and the direction of flow becomes smaller). This is of the utmost importance in the use of Doppler ultrasound. Freq.qThe angle of insonation Flow velocity321Factors affecting doppler frequency

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(the angle q between the beam and the direction of flow becomes smaller). This is of the utmost importance in the use of Doppler ultrasound. beam (A) is more aligned than (B)The beam/flow angle at (C) is almost 90° and there is a very poor Doppler signalThe flow at (D) is away from the beam and there is a negative signal.

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Aliasing If a second pulse is sent before the first is received, the receiver cannot discriminate between the reflected signal from both pulses and aliasing occur.

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Aliasing So to eliminate aliasing The pulse repetition frequency or scale is set appropriately for the flow velocities

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The volume flow in the UAs increases with advancing gestation. The high vascular impedance detected in the first trimester gradually decreases. It is attributed to growth of placental unit and increase in the number of the functioning vascular channels. Basic Principals

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Usesplays a vital role in the diagnosis of fetal cardiac defects . assessment of the hemodynamic responses to fetal hypoxia and anemia. diagnosis of other non-cardiac malformations.

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Blood supply provided by the ovarian and uterine arteries Uterine Arteries: main branches of the internal iliac arteries Uterine Arteries: Ascend through the lateral wall and anastomose with the ovarian arteriesAnatomy

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Spiral Arteries: connect the maternal circulation to the endometrium Responsible for a 10 fold increase in blood flowAnatomyArcuate Arteries: Run Circumferentially around the uterus Uterus: Blood supply to anterior and posterior walls provided by the Arcuate arteries Radial Arteries: Extend from the arcuate arteries and enter the endometrium

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Conversion of small muscular spiral arteries into large vascular channels transforms the uteroplacental circulation into a low-resistance-to-flow system. These have a dilated and tortuous lumen, a complete absence of muscular and elastic tissue, no continuous endothelial lining. Anatomy

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Umbilical artery doppler

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Doppler indices

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UMBILICAL ARTERY FLOW characteristic saw-tooth appearance of arterial flow in one direction and continuous umbilical venous blood flow in the other. Umbilical artery

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FACTORS AFFECTING UMBILICAL ARTERY DOPPLER FLOW VELOCITY WAVEFORMS*

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Benefit of Umbilical Artery Evaluation Less experienced operators can achieve highly reproducible results with simple, inexpensive continuous-wave equipment . Umbilical artery

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The 40% of the combined fetal ventricular output is directed to the placenta by two umbilical arteries. The assessment of umbilical blood flow provides information on blood perfusion of the fetoplacental unit . . Umbilical artery

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With advancing gestation, umbilical arterial Doppler waveforms demonstrate a progressive rise in the end-diastolic velocity and a decrease in the pulsatility index. Umbilical artery

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Middle cerebral artery doppler

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The possible Doppler velocimetry sites Using color flow imaging, the middle cerebral artery can be seen as a major lateral branch of the circle of Willis, running anterolaterally at the borderline between the anterior and the middle cerebral fossae Middle cerebral artery

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Last Updated: 8th March 2018

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