Ultrasound is an imaging modality that utilizes high-frequency sound waves to provide cross-sectional images of the body. The ultrasound machine has the following components: monitor, keyboard, processor, data storage and probe or transducer.
A transducer performs two functions: it emits sound waves (echoes) at a certain frequency and captures the returning echoes at frequencies dependent on the tissues through which the waves traverse. The sound wave that is returned to the transducer is digitized to appear as echoes or dots on the screen. Images are acquired in real-time and can be acquired in any imaging plane.
Ultrasound may be conventional real-time or Doppler. Doppler ultrasound is used for vascular studies using the Doppler shift phenomenon. Ultrasound is cheap, easy to perform, can be moved to remote places, does not use ionizing radiation. The outcome of the study is operator dependant.
Common clinical applications
- Abdominal ultrasound: To visualize the anatomy and pathology of the liver and gallbladder, spleen, kidneys, retroperitonium, abdominal vascular structures, lymph nodes.
- Pelvic ultrasound: To assess the prostate, urinary bladder, reproductive organs, adnexial masses, vascular structures, lymph nodes.
- Cardiovascular ultrasound including echocardiography: To assess the heart and peripheral vascular structures.
- Intraluminal Ultrasound: To assess gastrointestinal tract and the blood vessels.
- Obstetric ultrasound: To assess the fetus and related structures in pregnant women.
- Small parts ultrasound: Thyroid, scrotum, breast ultrasound
- Transfontanelle ultrasound: To visualize the intracranial structures before the closure of the fontanelles in paediatric patients or through boreholes.
- Ultrasound is considered a very safe procedure with minimal known adverse effects, and no radiation exposure making it widely used in antenatal care.
- Potential complications are related to cavitation, the formation of a bubble within a biological structure. The risk of cavitation is very low at the ultrasound intensities used for medical diagnosis.