ARDMS (American Registry for Diagnostic Medical Sonography) Practice Test

What is the fundamental reason that the power and intensity of the ultrasound beam diminish as it travels through tissue?

1. Cavitation

2. Obstruction

3. Acoustic impedance

4. Absorption

The correct answer is: Absorption

The correct answer is D. Absorption. Ultrasound beams lose power and intensity as they travel through tissue primarily due to absorption. Absorption occurs as the ultrasound beam interacts with the tissue, leading to conversion of the beam's energy into heat. This process results in a decrease in the power and intensity of the beam as it penetrates deeper into the tissue. Options A, B, and C are incorrect: A. Cavitation does not directly cause the power and intensity of the ultrasound beam to diminish as it travels through tissue. Cavitation refers to the formation of gas-filled bubbles in liquid, which can have other effects but do not significantly contribute to the loss of power and intensity of the ultrasound beam. B. Obstruction may affect the path of the ultrasound beam but is not the primary reason for the decrease in power and intensity as it travels through tissue. C. Acoustic impedance relates to the difference in acoustic properties between two media, which can affect the reflection of the ultrasound beam at tissue interfaces but is not the fundamental reason for the diminishing power and intensity of the beam.