Ultrasound uses high-frequency sound waves to produce images of inside organs. Prior to the examination, a special lubricating jelly, which helps transmit sound wave, is applied on the skin surface. When the transducer sends high-frequency sound waves through the body, the waves echo as an internal structure is reached and these echoes are subsequently reflected back to form images. Depending on the area being examined, the differences in echo time and intensity give rise to a unique image.
The ultrasound image is white or grey depending on the intensity of the reflection. Unlike other imaging modalities, ultrasound does not detect tissue density but rather the reflection of sound. Water, such as in cystic lesions, hardly reflects echoes and thus appear black on an ultrasound image. Conversely, highly dense tissues, such as bone or stones, readily reflect echoes and thus appear bright white on an ultrasound.
Moreover, as ultrasound produces real-time images, it can be used to examine blood flow. Coupled with the advantage of being radiation-free, it is widely used in pregnancy women for assessing fetal heart rate or detecting the location of placenta.
However, as Ultrasound does not travel well through air or bone, it might not be effective at imaging bony structures or hollow organs, such as the stomach and intestines. Should there be any concerns, patients may seek advice from doctors for the most effective imaging option.
Below is the information regarding the uses, safety issues, concerns of undergoing an Ultrasound examination and its advantages and limitations in comparison with other types of imaging modalities.