ARDMS Ultrasound Physics & Instrumentation Practice Exam 2025 – Complete Study Resource

The physical property of tissues that primarily affects reflectivity in ultrasound is the differences in acoustic impedance between the tissues. Acoustic impedance is a property derived from both the density of a tissue and the speed of sound within that tissue. When ultrasound waves travel from one tissue type to another, a change in acoustic impedance results in reflection of some of the sound energy at the boundary between the tissues.

High reflectivity occurs when there is a significant difference in acoustic impedance between the two adjacent tissues, leading to more pronounced echoes that can be detected by the ultrasound machine. For example, interfaces between structures such as fat and muscle or muscle and bone create strong reflections due to their differing acoustic impedances, which allows for effective imaging of those boundaries.

While variations in density within tissues, conductivity of tissue material, and elasticity of tissue fiber can influence various aspects of sound transmission and tissue characteristics, they do not have the same direct and significant impact on reflectivity as acoustic impedance differences do. These other properties may play roles in aspects such as wave propagation and attenuation but are not the primary determinants of reflectivity within the context of ultrasound imaging.