An ultrasound scan is a diagnostic procedure commonly used to assess soft tissue structures such as the organs, muscles, blood vessels and some glands such as the thyroid and parathyroid. Ultrasound is more often known for its use in pregnancy, but is actually used for many, many areas of the body.
Your ultrasound scan will be performed by a Radiologist or a Sonographer who has been highly trained in performing, interpreting and reporting ultrasound scans.
An ultrasound scan uses a handheld transducer (also called a probe) to create electronic images of the area being examined. The transducer is placed on the skin and moved across the body with varying levels of pressure. The transducer generates high frequency ultrasound waves which travel through the skin to the tissues and organs. The ultrasound waves bounce off these structures like an echo, and return to the transducer where they are converted by the scan machine’s computer into an electronic picture seen on the monitor.
Different types of body tissues and organs will create a different grey scale signals. The range of greys on the monitor, along with the pattern and placement of the echoes will be interpreted by the Sonographer or Radiologist.
Generally, high density structures such as bone will appear as bright grey/white, and low density structures such as fluid will appear as dark grey/back. Some structures, like bone, can block the path of the ultrasound waves. This is called an acoustic shadow, and can sometimes obscure the image.
A water based gel is used to prevent any air getting between the transducer and skin. This gel also allows the sounds waves to pass into the body and helps with the gliding movement of the transducer over the skin surface.
Ultrasound scans views the body’s tissues and organs in ‘real time’. This allows us to assess the function of some of the body’s anatomy at the time of the scan, especially the tendons and muscles.
Risks
Diagnostic ultrasound is generally regarded as one of the safest ways to image inside the body as it does not use ionizing radiation.
Qualified ultrasound practitioners only scan for as long as necessary to obtain the information required and will not scan beyond this time to avoid any ill-effects. There are no known side effects from a medically diagnostic scan of an appropriate length.
Although ultrasound is a valuable tool, it does have its limitations. Sound waves don’t travel well through air or bone, for example, ultrasound is not effective at imaging parts of your body that have gas in them (such as the bowel) or that are situated underneath air-filled bowel or bone. Ultrasound also has limited depth capability, so if the structure being examined is too deep in your body, the ultrasound image may be poor. When ultrasound examinations fail to produce diagnostic images, your referring doctor may choose a different type of scan for you, such as a CT or MRI scan.
What to Expect
When you enter the scan room, you will be met by the Radiologist or Sonographer who will be performing your scan, plus an assistant who is there to help both you and them. As George Eliot Hospital NHS Trust is a teaching hospital, there may also be a student present, however the Radiologist/Sonographer will ask for your consent for them to remain in the room.
For the scan, you will be asked to lie or sit on an examination couch and the ultrasound gel will be applied to the area of your body that is going to be examined. The transducer will be moved in different areas to view the area from many different angles. You may be asked to control your breathing or hold your breath at various points during the scan. This helps hold the organs still so they can be visualised without being blurry, and sometimes it helps to move them out of the way of other structures such as overlying ribs. The sonographer or Radiologist will usually take measurements during the scan which can sometimes be alarming, but this is a normal part of most scans.
Your ultrasound scan should not be painful, however the Radiologist or Sonographer has to apply some pressure in order to obtain clear images. The level of pressure required varies from patient to patient. Some examinations, especially scans looking for blood clots in the veins, do require quite firm pressure to be applied. During any scan, if you find it too difficult or uncomfortable, please tell the Sonographer/ Radiologist and you will usually be able to have a short break from the pressure. The Sonographer/Radiologist will never continue scanning if you need them to stop.
At the end of the scan, you will be given some paper tissue to remove the ultrasound gel. If your skin still feels sticky any remaining gel can be washed off with soap and water, but it also dries quickly on its own. An ultrasound scan usually takes 10-20 minutes, depending on the area of your body that is being scanned.
For ultrasound examinations of the uterus (womb) and ovaries, it is often beneficial to have an internal scan called a transvaginal scan (TVS). This type of scan would always be discussed with you before you give your consent, and you may decline it if you choose. During a TVS, the ultrasound probe is shaped like a long wand. The probe is sterilised, a sterile cover is applied to the probe and the tip of the probe is inserted into the vagina. The rest of the probe is used as a handle for the Sonographer/Radiologist to steer it externally. This type of internal examination does not use a speculum and most people do not find it uncomfortable at all. Like any scan, if at any point during the scan you ask the Sonographer or Radiologist to stop, they will do so straight away.
Afterwards
After the examination you can get dressed (if you were changed into a gown) and leave the department. The results of your examination will not usually be given to you on the same day. The results are sent electronically to the department who referred you for your scan, or to your GP. The results usually only take a few days to be accessible by the referring doctor or nurse, however they may then have further results or tests to wait for before they contact you.
You will be told after the examination who your results are being sent to, and advised how you are likely to get your results.
GEH 640 21-24 July 2021