In terms of ultrasound, what does the term "impedance" refer to?

Impedance in the context of ultrasound refers to the resistance that a medium poses to the transmission of sound waves. It is a critical concept because it influences how much sound is reflected versus transmitted when it encounters a boundary between different tissues. Impedance is determined by the density of the tissue and the speed of sound within it.

When ultrasound waves travel through different types of tissues in the body, varying amounts of sound are reflected back to the transducer depending on the differences in impedance. High impedance mismatches between two tissues can lead to greater reflection, which is crucial for imaging purposes. This characteristic allows sonographers to differentiate between various structures in the body, as different tissues (like fat, muscle, and fluid) will have distinct impedance values.

Understanding impedance helps in optimizing ultrasound settings and improving image quality, making it fundamental for effective diagnostics in ophthalmology and other medical fields.