OB-dopplerultrasound

OB-dopplerultrasound - DOPPLER ULTRASOUND in Pregnancy in...

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Unformatted text preview: DOPPLER ULTRASOUND in Pregnancy in Dr. Mohammed Abdalla Egypt, Domiat Hospital Doppler History First use of Doppler ultrasonography to study flow velocity in the fetal umbilical artery umbilical was reported in 1977 was 1977 Doppler History Doppler Fitzgerald & Drumm. Umbilical artery studies 1977BMJ Fitzgerald Umbilical Eik-Nes et al. Fetal aortic velocimetry : Dupplexscanner Eik-Nes Fetal 1980 Lancet Lancet Campbell et al. Utero-placental circulation: Dupplex Campbell Utero-placental Dupplex scanner 1983 Lancet Lancet Wladimiroff et al. MCA / UA PI ratio 1987 OG Wladimiroff MCA OG Kiserud et al. Ductus venosus velocimetry 1991Lancet Kiserud Ductus Basic principals Basic Echoes from stationary tissues are the same from Echoes pulse to pulse. Echoes from moving objects exhibit slight differences in the time for the signal to be returned to the receiver. returned These differences can measured as phase shift These phase from which the Doppler frequency is obtained. Doppler T1 : T1 T2 : time of omitted signal . time of returned signal . T2 – T1 = time difference or phase shift . shift from phase shift the Doppler from frequency is obtained. frequency AS TIME DIFFERENCE DECREASE THE AS DOPPLER FREQUENCY INCREASE. DOPPLER T2 T1 pulse repetition frequency pulse (T2 –T1) phase shift with known beam / flow angle can phase calculate flow velocity . Basic Principals The time difference or phase shift are then proceeded to produce either colorflow display or a colorflow Doppler sonogram Basic Principals Basic ‘Doppler frequency’ is obtained by measuring Doppler the time difference for the signal to be returned when reflected from moving scatterers . when Doppler frequency increase if: 1. flow velocity increased . flow 2. beam is more aligned to the direction of flow. flow. 3. higher transducer frequency is used. higher Factors affecting doppler frequency Fr eq . 3 2 q The angle of insonation Flow velocity 1 (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. (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) beam (B) The beam/flow angle at (C) is almost 90° and there is a very poor Doppler signal The is The flow at (D) is away from the beam and there is a negative signal. The is Aliasing 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. Aliasing Aliasing So to eliminate aliasing The pulse repetition frequency or scale is set appropriately for the flow velocities Basic Principals Basic 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. the Uses Uses plays a vital role in the diagnosis of plays fetal cardiac defects . cardiac assessment of the hemodynamic assessment responses to fetal hypoxia and hypoxia anemia. anemia diagnosis of other non-cardiac malformations. Anatomy Blood supply provided by the ovarian and uterine arteries arteries Uterine Arteries: main Uterine branches of the internal iliac arteries iliac Uterine Arteries: Ascend Uterine through the lateral wall and anastomose with the ovarian arteries ovarian Anatomy s s s Arcuate Arteries: Run Circumferentially around the uterus Arcuate Uterus: Blood supply to anterior and posterior walls Uterus: provided by the Arcuate arteries provided Radial Arteries: Extend from the arcuate arteries and Radial enter the endometrium enter s Spiral Arteries: connect the maternal circulation to the Spiral endometrium endometrium s Responsible for a 10 fold increase in blood flow Anatomy Anatomy sConversion 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. endothelial Umbilical artery doppler Doppler indices Umbilical artery Umbilical UMBILICAL ARTERY FLOW characteristic saw-tooth appearance of arterial flow in one direction and continuous umbilical venous blood flow in the other. FACTORS AFFECTING UMBILICAL ARTERY DOPPLER *FLOW VELOCITY WAVEFORMS FLOW Umbilical artery Benefit of Umbilical Artery Evaluation Benefit Less experienced operators can achieve Less highly reproducible results with simple, inexpensive continuous-wave equipment . equipment Umbilical artery 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 . unit Umbilical artery Umbilical With advancing gestation, umbilical arterial Doppler waveforms demonstrate a progressive rise in the end-diastolic velocity and a decrease in the pulsatility index. Middle cerebral artery doppler The possible Doppler velocimetry sites The Middle cerebral artery 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 Middle The blood velocity increases with advancing gestation, and this increase is significantly associated with the decrease in PI Middle cerebral artery Middle An early stage in fetal adaptation to hypoxemia central redistribution of blood flow central ( brain-sparing reflex) increased blood flow to protect the brain, heart, and adrenals reduced flow to the peripheral and placental circulations circulations Doppler wave form of early stage of Doppler fetal hypoxemia fetal increased end-diastolic flow in the middle cerebral artery (lower MCA pulsatility index or resistance index) index index Average of both MCAs must be calculated for more precise result Middle Cerebral Artery Middle Flow velocity waveform in the fetal middle cerebral artery Flow in a severely anemic fetus at 22 weeks (left) and in a normal fetus (right). In fetal anemia, blood velocity is increased increased Middle Cerebral Artery When the fetus is hypoxic, the cerebra arteries tend to become dilated in order to preserve the blood flow to the brain and The systolic to diastolic (A/B) ratio will decrease (due to an increase in diastolic flow) increase Doppler ultrasound for the fetal assessment in high-risk pregnancies (Cochrane Review). In: The Cochrane Library, 1999. Neilson JP and Alfirevic Z 1999. 11 Studies Included In Analysis Trudinger et al 1987 McParland et al 1988 Tyrrell et al 1990 Hofmeyr et al 1991 Newham et al 1991 Burke et al 1992 Almstrom et al 1992 Biljan et al 1992 Johnstone et al 1993 Pattison et al 1994 Nienhuis et al 1997 Doppler ultrasound for the fetal assessment in high-risk pregnancies in Meta analysis Nearly 7000 patients were included The trials compared no Doppler ultrasound to The Doppler ultrasound in high-risk pregnancy (hypertension or presumed impaired fetal growth) growth) Doppler ultrasound for the fetal assessment in high-risk pregnancies in Main results A reduction in perinatal deaths. Fewer inductions of labour . Fewer admissions to hospital . no report of adverse effects . No difference was found for fetal distress No in labour . in No difference in caesarean delivery . Biophysical profile for fetal assessment in Biophysical high risk pregnancies • When compared with conventional fetal monitoring (usually cardiotocography) biophysical profile testing showed no obvious effect (either beneficial or deleterious) on pregnancy outcome. There was an increase in the number of inductions of labour following biophysical profile in the trial. following Alfirevic Z, Neilson JP. Biophysical profile for fetal assessment in high risk pregnancies (CochraneReview). In: The Cochrane Library, 1995. ...
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This note was uploaded on 12/24/2011 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.

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