DOPPLER ULTRASOUND

The Use of Doppler Ultrasound

Abstract

The aim of this study is to analyse the Doppler Ultrasound techniques used in gynaecology for high-risk pregnancies such as ectopic pregnancy, preeclampsia, fetal growth restriction, fetal anomalies, etc. It explains the uses of Doppler Ultrasound in the diagnosis of carotid artery stenosis.It also tells about what are the different types and different of Doppler, how they are used?It tells what are the findings in different types of fetal anomalies and pregnancy complications.It tells about the findings of Doppler in patints with carotid stenosis,and how external and internal carotid Doppler can be used in patients for diagnosis of stenosis.



The Use of Doppler Ultrasound

Introduction

In recent years, the importance of ultrasound flow imaging has greatly increased enormously. Doppler ultrasound provides new ways of diagnosis in the field of medicine. The basic principal of Doppler is to take the images of flow. In colour flow or spectral Doppler, the images are obtained from the assessment of movements. Echoes from moving objects produce different signals to be returned to the receiver, which then produce colour flow display or a Doppler sonogram.

The main properties of Doppler are:

Spectral Doppler

•It evaluates flow at one site.

•It analyses distribution of flow.

•It provides temporal resolution.

•Velocity calculations.

Color Flow

•Tells about flow in an organ.

•It shows colour flow map.

•It shows direction.

•It shows velocity information.

Types of Doppler

There are three types of Doppler ultrasound, pulsed wave, continuous wave and color flow. In both PW and CW Doppler, a specific pixel is given to the frequency of the returning signal.

Continuous Wave Doppler

It transmits and receives the signals by two crystals. It can measure high velocity blood flow. It is valuable when examining stenotic and regurgitant heart values in which blood flood velocity is very high. It can also be used to measure the pulmomnary artery pressure (Frankel &Boisblanc, 2010, pp. 67)

Pulse Wave Doppler

PW Doppler operates by one crystal. It allows detailed evaluation of flow over time at an accurate depth or point in image (Frankel & Boisblanc, 2010, pp. 67)

pp.67).

The Color Flow Doppler

It is a specific wave signal, with a unique color value given to signals that are received. A higher frequency Doppler transducer shows red and lower frequency transducer shows blue signal. It is useful in gynecological procedures (Frankel &Boisblanc, 2010, pp. 67 )

Indices of Spectral Analysis

Commonly used indices in spectral analysis are

•Resistance index.

•Systolic/diastolic .

•Pulsatility index . (Merz E., 2006, pp.15)

Use of Doppler in High-Risk Pregnancies

Ectopic pregnancy

To see the Doppler findings in ectopic pregnancy, its findings can be compared with the gray-scale ultrasound, in which a probe of 3.5 MHz is used for transabdominal ultrasound. The resolution of transabdominal probe is lower than transvaginal probe.The ultrasound signs for

as following :

•Absence of sac, including the double ring around it

•Absence of fetus within the gestational Sac.

•Presence of extra adnexal structure.

•Uterine enlargement with a thickened endometrial (Kupesic & Kurjak, 2000, pp. 169)

Blood in the cul-de-sac appears as a hyperechoic or anechoic retrouterine echoes. Transabdominal ultrasound has a low sensitivity for the detection of an ...