ITGSS Certified Technical Associate: Emerging Tech Practice Test

Contrast harmonics are created during reflection off of:

1. The transducer

2. Microbubbles

3. Penetrated tissues

4. Blood flow

The correct answer is: Microbubbles

The correct answer is that contrast harmonics are created during reflection off of microbubbles. This phenomenon occurs due to the nonlinear behavior of microbubbles when they are subjected to an ultrasound field. When ultrasound waves interact with microbubbles, they can oscillate in a nonlinear manner, which generates additional harmonic frequencies. These harmonics are higher frequency signals that are produced because the microbubbles do not only respond linearly to the ultrasound pressure but also expand and contract in a way that creates new frequencies distinct from the original sound wave. This process enhances the contrast of ultrasound images, making it easier to differentiate between the microbubbles and the surrounding tissues. In contrast, the other options involve reflections and responses that do not generate harmonics to the same extent as microbubbles. For instance, while a transducer may produce ultrasound waves, it does not generate harmonics during reflection; rather, it is responsible for emitting and receiving the ultrasound signal. Similarly, penetrated tissues and blood flow reflect sound waves, but they do so in a linear manner and do not produce the same nonlinear harmonic effects seen with microbubbles. Therefore, the unique physical properties of microbubbles are what specifically facilitate the creation of contrast harmonics during ultrasound imaging.