Physics II: Dynamic Range, Harmonics, and Contrast Agents

Flashcards covering dynamic range, tissue harmonics, contrast agents, and their clinical applications in ultrasound physics.

Dynamic Range

The extent to which the method of reporting a signal can vary and still be processed accurately, expressed as a ratio between the largest and smallest signals in $dB$.

Threshold

The level below which signals are too weak for the system to register or process.

Saturation

A state where signals are too strong for the system to measure or process.

Transducer Dynamic Range

The dynamic range of the transducer component, which is $120\,dB$.

Receiver Dynamic Range

The dynamic range of the receiver component, which is between $100\,dB$ and $120\,dB$.

Scan Converter Dynamic Range

The dynamic range of the scan converter component, which is between $40\,dB$ and $50\,dB$.

Display Dynamic Range

The dynamic range of the display component, which is between $20\,dB$ and $30\,dB$.

Archive Dynamic Range

The dynamic range of the archive component, which is between $10\,dB$ and $30\,dB$.

Fundamental Frequency

The original frequency of sound created by the transducer and transmitted into the tissue.

Harmonic Frequency

A frequency that is twice the fundamental frequency, created by non-linear behavior in the medium.

Tissue Harmonics

Harmonics created during transmission in tissue, caused by sound traveling faster in compressions and slower in rarefactions.

Non-linear Behavior

The physical basis for harmonics, such as sound traveling at different speeds during compressions and rarefactions, or microbubbles responding unevenly to pressure.

Mid Field (Harmonics)

The depth region where the best harmonic effects are generated in tissue harmonic imaging.

Bandpass Filter

A filter used to eliminate fundamental frequency echoes while allowing the second harmonic echo bandwidth to be processed.

Contrast Agents

Also called microbubbles, these consist of gas bubbles entrapped in a shell and are used to create strong reflections and better visualize borders in cardiac and vascular imaging.

Contrast Harmonics

Harmonics created during reflection off of a microbubble, determined by the shell, the gas, and the mechanical index ($MI$).

Mechanical Index ($MI$)

A value related to the production of contrast harmonics: a low $MI$ creates no harmonics, while a high $MI$ produces a large amount of harmonics.