USG Basics, Part 3: Echogenicity: How Sound Waves Create Images of the Body

In the Article - Unlocking the mysteries of echogenicity: Discover how sound waves create images of the body in this informative blog post on ultrasound basics.

Introduction - One of the medical imaging techniques that uses sound waves to produce pictures of the body’s internal structures is ultrasound. Ultrasound can be useful for diagnosing various diseases, monitoring the health of organs, and guiding procedures. However, ultrasound pictures are not always easy to see and understand. Echogenicity is one of the factors that influence how ultrasound pictures look and how clear they are.

Echogenicity -

Echogenicity refers to how well a tissue or an object reflects sound waves back to the ultrasound device. The more sound waves are bounced back, the higher the echogenicity. The fewer sound waves are bounced back, the lower the echogenicity.

Echogenicity is not a constant characteristic of a tissue or an object. It varies depending on the sound wave frequency, the angle of the sound wave, and the contrast with the nearby tissues. Echogenicity can also be affected by different pathological or physiological changes that alter the density, composition, or structure of the tissue or the object.

Ultrasound waves have different interactions with different body structures and create different levels of brightness in the picture. Based on Echogenicity strictures can be classified into

• Anechoic Structure - No echoes are reflected by structures that are anechoic and they appear as black on a picture made by ultrasound.

• Hypoechoic Structure -Blood, effusions, and cysts are examples of structures that are hypoechoic. They have a low level of echogenicity and reflect few echoes. They look dark in an ultrasound picture.

• Hyperechoic Structure -Skin, calcium, ligaments, gallstones, and pericardium are very reflective and have high echogenicity. They are called hyperechoic and look bright on a picture made by ultrasound.

• Isoechoic Structure –Two or more tissues that have the same level of brightness on an ultrasound picture are called isoechoic. They reflect the same amount of sound waves as measured by ultrasound. The kidneys, liver, and myocardium are examples of isoechoic tissues because they have a similar grayscale.

Homogeneous vs. heterogeneous areas in ultrasound -

Homogeneous vs. heterogeneous areas in ultrasound are terms that describe the texture and uniformity of the tissues or objects on ultrasound images.

Homogeneous means that the tissue or the object has a smooth and consistent appearance on ultrasound images. The sound waves are reflected evenly and the echogenicity is similar throughout the tissue or the object. Homogeneous areas usually indicate normal or benign conditions. Examples of homogeneous tissues or objects are the thyroid gland, the liver, the spleen, the kidney, the bladder, and simple cysts.

Heterogeneous means that the tissue or the object has a rough and irregular appearance on ultrasound images. The sound waves are reflected unevenly and the echogenicity varies throughout the tissue or the object. Heterogeneous areas usually indicate abnormal or malignant conditions. Examples of heterogeneous tissues or objects are the breast, the prostate, the pancreas, the uterus, the ovary, and complex cysts.

About the Author -

Dr. Debjyoti Dutta, a distinguished author and pain physician, practices at Samobathi Pain Clinic and Fortis Hospital, Kolkata. Serving as the registrar of the Indian Academy of Pain Medicine, he specializes in interventional pain management and musculoskeletal ultrasound. Renowned globally, he authored key books like "Musculoskeletal Ultrasound in Pain Medicine" and "Clinical Methods in Pain Medicine," offering comprehensive insights into pain management.