ARDMS Ultrasound Physics & Instrumentation Practice Exam

What is the attenuation coefficient in soft tissue relative to operating frequency?

1. Equal to the operating frequency

2. One quarter of the operating frequency

3. One half of the operating frequency

4. Twice the operating frequency

The correct answer is: One half of the operating frequency

The attenuation coefficient in soft tissue is found to be approximately one half of the operating frequency expressed in megahertz (MHz). This relationship is grounded in the understanding of how ultrasound waves interact with tissue. As ultrasound travels through soft tissue, it undergoes scattering, absorption, and reflection, which collectively contribute to attenuation. The attenuation coefficient provides a numerical value that reflects how much the intensity of the ultrasound beam is decreased as it travels through a medium such as soft tissue. The principle behind this coefficient indicates that it increases with frequency; higher frequencies result in greater attenuation. Therefore, at a certain operating frequency, the attenuation can be estimated to be around half of that frequency. Utilizing this relationship helps sonographers and ultrasound technicians to better select the appropriate frequency for imaging based on the characteristics of the tissues being examined and ensures that the ultrasound system is optimized for the best image quality possible.