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	Obstretics & Gynaecological Colour Doppler Ultrasound
	flow velocity waveforms
	3-D Ultrasound/Colour Doppler
	2-D image can be very nicely depicted.
	2-D image can be very nicely depicted.

Obstretics & Gynaecological Colour Doppler Ultrasound

The doppler shift principle has been used for a long time in fetal heart rate detectors. Further developments in doppler ultrasound technology in recent years have enabled a great expansion in it's application in Obstetrics, particularly in the area of assessing and monitoring the well-being of the fetus, and the diagnosis of cardiac malformations. Doppler ultrasound is presently most widely employed in the detection of fetal cardiac pulsations and pulsations in the various fetal blood vessels. The "Doptone" fetal pulse detector is a commonly used handheld device to detect fetal heartbeat using the same doppler principle.

Blood flow characteristics in the fetal blood vessels can be assessed with Doppler 'flow velocity waveforms'. Diminished flow, particularly in the diastolic phase of a pulse cycle is associated with compromise in the fetus. Various ratios of the systolic to diastolic flow are used as a measure of this compromise. The blood vessels commonly interrogated include the umbilical artery, the aorta, the middle cerebral arteries and the uterine arcuate arteries.

The use of color flow mapping can clearly depict the flow of blood in fetal blood vessels in a realtime scan, the direction of the flow being represented by different colors. 'Color' doppler is particularly indispensible in the diagnosis and assessment of congenital heart abnormalities.

Another recent development is the Power Doppler (Doppler angiography). It uses amplitude information from doppler signals rather than flow velocity information to visualize slow flow in smaller blood vessels. A color perfusion-like display of a particular organ such as the placenta overlapping on the 2-D image can be very nicely depicted. Doppler examinations can be performed abdominally and via the transvaginal route. The power emitted by a doppler device is generally greater than that used in a conventional 2-D scan.

3-D Ultrasound/Colour Doppler

3-dimensional ultrasound is quickly moving out of the research and development stages and is now widely employed in a clinical setting. It too, is very much in the News. Faster and more advanced commercial models are coming into the market. The scans requires special probes and software to accumulate and render the images, and the rendering time has been reduced from minutes to fractions of a seconds.

A good 3-D image is often very impressive to the parents. Further 2-D scans may be extracted from 3-D blocks of scanned information. Volumetric measurements are more accurate and both doctors and parents can better appreciate a certain abnormality or the absence of a certain abnormality in a 3-D scan than a 2-D one and there is the possibility of increasing psychological bonding between the parents and the baby.

An increasing volume of literature is accumulating on the usefulness of 3-D scans and the diagnosis of congenital anomalies could receive revived attention. Present evidence has already suggested that smaller defects such as spina bifida, cleft lips/palate, and polydactyl may be more lucidly demonstrated. Other more subtle features such as low-set ears, facial dysmorphia or clubbing of feet can be better assessed, leading to more effective diagnosis of chromosomal abnormalities. The study of fetal cardiac malformations is also receiving attention. The ability to obtain a good 3-D picture is nevertheless still very much dependent on operator skill, the amount of liquor (amniotic fluid) around the fetus, it's position and the degree of maternal obesity, so that a good image is not always readily obtainable.

More recently, 4-D or dynamic 3-D scanners are in the market and the attraction of being able to look at the face and movements of your baby before birth was also enthusiastically reported in parenting and health magazines. This is thought to have an important catalytic effect for mothers to bond to their babies before birth. What are known as 're-assurance scans' and the rather misnamed 'entertainment scans' have quickly become popular.

Most experts do not consider that 3-D and 4-D ultrasound will be a mandatory evolution of our conventional 2D scans, rather it is an additional piece of tool like doppler ultrasound. 3-D ultrasound appears to have great potential in research and in the study of fetal embryology. Whether 3-D ultrasound will provide unique information or merely supplemental information to the conventional 2-D scans will remain to be seen.