Ultrasound

Ultrasound examples

Although we cannot hear ultrasound, it can be very useful in many different ways:

Ultrasound examples: Sonar

Sonar - also known as echolocation is a method for finding the distance to objects and surfaces that are difficult to reach or measure. The time that it takes for the ultrasound to bounce back from the object can be used to find the distance.

Fishing boats use ultrasound waves to find the position of fish beneath them, istockphoto

For example, fishing boats sometimes carry sonar equipment so that they can determine the depth of water that they are travelling through. Ultrasound pulses are emitted from the boat by a transmitter. The time taken for the pulses to reach the seabed and reflect back to the boat is measured using a detector (the ultrasound waves could also be directed at a shoal of fish in order to see how far away they to aid in catching them). The ultrasound signal is converted into an electrical pulse and the time taken between releasing the waves and the largest value of the electrical signal can be used along with the speed that the waves move through the water to find how deep the water is.

Ultrasound scans

Ultrasound can also be used for foetal scanning - also known as pre-natal scanning. It enables doctors to check the sex of the babies before they are born. It can also be used to see if a baby is in good health and to find what position it is in.

Ultrasound scans are used to produce images of babies and foetuses while still in the womb.

The process of foetal scanning involves moving a probe over the mother's stomach, which sends ultrasound waves into her body. Ultrasound waves are partially reflected whenever they reach a boundary between two different materials. In this case, some of the ultrasound signal will be sent back when it reaches the baby's body, which is a different material to the fluid surrounding it. The probe then detects the returning ultrasound radiation. It can be moved around to find how long it takes for the ultrasound to return at different points, which can be used along with the known speed of the waves in the fluid to produce an image of the baby.

Ultrasound uses

In addition to the examples mentioned above, ultrasound has many other uses both in medicine and industry.

Ultrasound uses: Medical applications

Ultrasound is not just used for people having babies, it can also be used for medical imaging purposes. For example, people who who are having some kind of problem with their internal organs, such as damaged lungs or kidneys.

You may have already learned about how X-rays can be used to identify internal problems with the body. There is much less risk of damage to your internal organs when using ultrasound as opposed to X-rays.

Ultrasound uses: Quality control

Ultrasound is also used in industry to check for irregularities in materials, such as metal castings. This involves sending ultrasound pulses through the material, when the waves reach a crack in the structure of the object, they will be partially reflected. This means that there will be a small pulse in the electrical signal detected that arrives at an earlier time than the time it would take for the waves to travel to the end of the object and back. This can be used along with the speed of the ultrasound waves in the material to find the exact position of the irregularity.

Ultrasound equipment can be used to detect cracks in a pipe.

Ultrasound advantages

Ultrasound is used in medicine for a variety of different medical problems. This is because it has some key advantages over other medical techniques:

• Ultrasound can be used to form images of internal organs without the need to operate on patients. This can save a lot of time and money and prevents the risks associated with invasive surgery.
• The equipment used for ultrasound is inexpensive compared to other types of medical imaging equipment. It is also quite easy to transport and operate.
• As mentioned above, ultrasound is not very harmful to internal organs (or for foetuses when it is used for foetal scanning). It does not cause any harm to the tissue in comparison with other techniques that require the patient to be exposed to ionising radiation such as X-rays which can sometimes be very damaging to cells in the body.
• Ultrasound can be used to capture images of soft tissues which will not show up when using other medical imaging techniques such as X-rays. This is because the pictures produced come from how ultrasound is partially reflected at the boundaries between materials and even if the electrical signal produced is small, the boundary can still be identified. On the other hand, X-rays work on the basis of forming a picture by passing X-ray radiation through the body and forming an image from the points where no radiation passes through (for example if it is blocked by a bone), so soft tissues will not be identified.