Written for Doctify by Dr Russell Young
Radiologist Dr Russell Young tells us everything you can expect from ultrasound scans.
What are the origins of ultrasound scanners?
The era of modern ultrasound advanced rapidly due to World War I, and the sinking of the Titanic. In 1914 it was used to detect submarines and icebergs, and then RADAR was developed just before World War II. In the 1940s, ultrasound was used to detect flaws in metals.
Then over the next 20 years, various medical uses were described involving imaging of the brain, gallbladder, heart, and in obstetrics and gynaecology. It was also used to treat rheumatoid arthritis. The biggest benefit was for pregnant women so a foetus could be checked for abnormalities, as other types of scans were too risky because of radiation.
The first handheld ultrasound scanner was introduced in 1963. Over the next 40 years, there were the quality and speed of ultrasound scanning was improved, allowing higher resolution to depths of 20 cm. More recently portable ultrasound machines have become available, as well as 3D sonography used mostly to visualize foetuses in the womb.
What is an ultrasound scan?
The key part of an ultrasound machine is the transducer, which generates and detects the ultrasound waves, which are then analysed and displayed on a screen for the radiologist to interpret.
Most ultrasound scans are performed externally using the transducer on the skin with gel to removal signal interference from the air. Some scans can be done internally, for example scanning in the oesophagus to see closer to the heart (tran-oesphageal echocardiogram), or transvaginal ultrasound to see the ovaries and uterus, or a foetus during the early weeks of pregnancy.
Ultrasound is usually painless, and most scans take less than half of an hour.
Do you have any facts and figures about ultrasound?
- Pythagoras developed the Sonometer, which measured musical sounds and the frequency of a tuning fork.
- In 1794, bats were shown to use sound waves for spatial orientation.
- In 1826, sound was shown to travel faster through water than air, using a church bell rung underwater at Lake Geneva.
- In 1842, the Doppler effect proposed that the frequency of sound waves depended on the speed of the source (think of ambulance sirens).
- Ultrasound is too high frequency for humans to hear, but dogs and cats can hear them.
- In the 1950s, patients had to be completely submerged in water during a scan.
- Now, one of the smallest ultrasound transducers can fit into a blood vessel.
- There are many non-medical uses including testing for metal fatigue, and cleaning jewellery, lenses, and watches.
What are the advantages?
- Most ultrasound is non-invasive (no needles or injections).
- Ultrasound is widely available and less expensive than other scans.
- Ultrasound imaging is extremely safe (no ionizing radiation).
- Ultrasound scanning can see soft tissues that do not show up well on x-rays, for example moving tendons.
- Ultrasound can be used to help guide biopsies, injections, stents, drainages, and during surgical operations.
- You can discuss your symptoms with the Doctor during the scan.
- Colour Doppler Ultrasound is very good at evaluating blood flow.
- Ultrasound likes soft tissues that are solid and uniform or filled with fluid.
- Ultrasound has a higher resolution than MRI and is better at seeing more superficial structures.
And the disadvantages?
- It requires a lot of training to learn to perform and interpret ultrasound scans, particularly as there are lots of different techniques.
- There is a risk of heating soft tissues in therapeutic higher frequency ultrasound.
- Ultrasound waves are disrupted by air and bone, so ultrasound cannot always see the bowel or inside bones.
- It is harder to see inside larger patients, as sound waves are weakened passing through increased soft tissue.
- MRI scans tend to be better for muscle injuries, stress fractures, and assessing the inside of bone and joints, although both tests can often be used well in combination.
What is ultrasound best for in musculoskeletal radiology?
- Lumps and bumps, collections, large bruises, and cysts.
- Tendons – rotator cuff, tennis elbow, wrist, hip, knee, ankle including the Achilles.
- Abdominal wall and groin hernias.
- Ankle ligaments.
- Arthritis and some muscle injuries.
- Injection treatments for tendinopathy and arthritis
- High-volume injections (hydrodilatation) for frozen shoulder.
Are there different types of ultrasound scan?
Different types of transducer can assess different structures:
- Head and Neck – eyes, thyroid and parathyroid glands
- Chest – heart, breasts, and fluid on the lungs
- Abdomen – liver, gallbladder, spleen, pancreas, kidneys
- Pelvis – bladder, uterus, ovaries, prostate, scrotum and testicles
- Foetus in pregnant patients
- Infants – brain, hips, and spine
- Musculoskeletal system – see above
- Blood vessels – arteries (carotid) and veins (DVT)
Recent developments in ultrasound scanning
- 3D ultrasound scanning of the breast for better detection of cancer.
- Mobile handheld ultrasound equipment that can connect to a tablet or smartphone.
- Wearable ultrasound devices used for the treatment of chronic pain.
- Treatment of rheumatoid arthritis and soft tissue sports injuries.
