What imaging technique uses high-frequency sound waves to visualize deep structures in the body?

Ultrasonography is the correct choice because this imaging technique utilizes high-frequency sound waves to create images of the internal structures of the body. The sound waves are transmitted into the body and are reflected back to a transducer, which converts them into images that can be interpreted by healthcare professionals. This method is particularly useful for visualizing organs and tissues, assessing blood flow, and diagnosing conditions in real time without the need for ionizing radiation, making it a safe option for various patient populations.

In contrast, septicemia refers to a severe and widespread infection in the bloodstream, not an imaging technique. Orchitis is the inflammation of one or both testicles and does not relate to imaging; it is a medical condition that may be evaluated through imaging but is not itself a method. A pessary is a medical device used to support pelvic organs, often in cases of pelvic organ prolapse, and is not associated with imaging techniques.