• Ultrasound: Not Just For Babies

    February 8th, 2011ImogenUncategorized

    In My Humble Opinion, Ultrasound is very cool. It is not as amazing to look at as MRI, nor as potentially lethal as X-Rays, but it can be used for a lot of diagnostic purposes. Many of us may remember ultrasound imaging from that grainy black and white image someone showed you excitedly as you tried to work out what it was. Or if you are like me and have not had any pregnant friends, remember that scene in Friends? This is because pregnant women on the NHS are currently offered at least 2 sonograms during their pregnancy in order to calculate the age of the foetus and to check it is growing healthily. Therefore this is the way in which we are most aware the way of using high-frequency sound to image inside the body.

    However, the applications are much broader. The first ultrasound machines were basically modified flaw detectors. Flaw detectors were used by ship builders to detect faults in the metal hulls of boats. The sound waves travel through the metal and are reflected by the air which fills cracks and imperfections. The connection was made by Ian Donald, Regius Professor of Midwifery at the University of Glasgow (Regius means that the post was originally created by a monarch and each appointment must be approved by the crown. This position was founded in 1815 by King George III). He was a keen sailor and became familiar with Sonar and Radar while serving in the RAF in the Second World War. Sonar was developed after the sinking if the Titanic and used sound waves to probe several miles of ocean. Any reflected sound indicated the presence of a possible ship-sinking object. Radar works in a similar way but using radio waves. It was Douglas who first brought ultrasound into the hospital to peek at babies in utero. Many developments then followed to develop the machines we use today, which have a mobile computing and display unit and a small probe on a flexible arm. The first machines required the examinee to sit in water bath so that the probe could achieve a good contact. This is because however hard you press a plain old probe against the skin; some air will still exist where the two meet. The air will reflect the ultrasound waves before they even get into the patient so that you will just get a useless fuzzy image. The modern ultrasound gel is water based (easier to remove than oil-based formulations) and forms a perfect air-free join for the sound waves to pass through before and after the body. It’s true what everyone says though, it does feel very cold when they put it on.

    Unlike X-rays, ultrasound does not fall under the classification of “Ionising Radiation”. That means that when the waves pass through your body they will not cause damage and so their use as a diagnostic tool does not need to be restricted in the same way. In light of this, ultrasound is frequently used to view active functions inside the body, in particular the function of the heart. A physician may employ ultrasound to view the action of particular heart valves if he suspects that the heart is not pumping correctly. By examining arteries to the brain and lower body it is possible to assess the risk of getting a stroke or blood clot by looking for plaque in these important vessels. During the first three months of a foetus’s life, the cells are dividing more rapidly than at any other point in its existence. More cell divisions mean more opportunities for things to go wrong, so to X-ray a baby at this point would be very hazardous. Therefore, non-ionising radiation such as Ultrasound is invaluable to check up on the baby without harming it. Recently, scientists have developed a pre-natal test for Down Syndrome which does not require an extraction of cells from the uterus. This is good because tests such as amniocentesis or chronic villus sampling (both of which use a needle to take cells from the amniotic fluid or placenta respectively) carry a risk of miscarriage. In the new technique, a ultrasonographer examines the nasal bone since babies with Down Syndrome tend to have a flatter bridge of the nose and almost nonexistent nasal bone. A test for “nuchal translucency” can also estimate the thickness of the skin at the back of the neck using a high-frequency ultrasound. A higher than normal thickness can indicate a genetic abnormality.

    However, ultrasound can be used for quite different purposes. Some anti-abortion politicians in certain states in America (such as Montana) think that women seeking a termination should have to have an ultrasound scan and listen to the foetus’s heartbeat for up to one hour before making a final decision. Abortion is a highly controversial issue and if this scan was compulsory then it would not fail to emotionally affect both the woman faced with this decision and the doctor forced by law to carry out the procedure. Some very interesting moral questions are raised, but this is not a political blog, so I won’t say more on the matter.

    AND SO to haul this post back from grim opinion-ism , I would like to draw your attention to this lovely little story I read the other day about the amusing pictures ultrasound can capture. Aaaaaah.

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