* High-Frequency Transducer: These provide better resolution but do not directly cause posterior enhancement.
* Low-Frequency Transducer: These provide better penetration but are not the cause of posterior enhancement.
* Strongly Attenuating Structure: This would cause acoustic shadowing rather than enhancement.
* Weakly Attenuating Structure: Structures that attenuate the ultrasound beam less than the surrounding tissues allow more sound waves to pass through, resulting in increased brightness or "enhancement" behind the structure.
References:
"Ultrasound Physics and Instrumentation" by Frank Miele
ARDMS Sonography Principles and Instrumentation study materials

Doppler Scale Too High: This would prevent aliasing but could result in loss of low-velocity signals.
Doppler Scale Too Low: When the scale is set too low, velocities exceed the Nyquist limit, resulting in aliasing where the Doppler signal wraps around the baseline.
Doppler Gain Too High: High gain may result in noise and overamplified signals but does not directly cause aliasing.
Doppler Gain Too Low: Low gain results in weak signal detection but does not cause aliasing.
Reference:
"Diagnostic Ultrasound: Principles and Instruments" by Frederick W. Kremkau ARDMS Sonography Principles and Instrumentation study materials

Changing the displayed depth control directly affects the pulse repetition frequency (PRF). When the depth setting is increased, the ultrasound system needs more time to send and receive echoes from deeper structures, resulting in a lower PRF. Conversely, decreasing the depth allows for a higher PRF since the time required for the sound waves to travel to and from the structures is shorter. PRF is crucial for determining the maximum detectable velocity in Doppler ultrasound without aliasing. Reference:
ARDMS Sonography Principles and Instrumentation guidelines
"Understanding Ultrasound Physics" by Sidney K. Edelman

Heat and Transient: Heat and transient are not classifications of cavitation.
Thermal and Mechanical: These terms refer to different bioeffects of ultrasound but are not types of cavitation.
Stable and Transient: These are the two types of cavitation observed in tissues during ultrasound. Stable cavitation involves the oscillation of gas bubbles without collapse, while transient cavitation involves the violent collapse of gas bubbles, which can generate high temperatures and shock waves.
Thermal and Stable: Thermal effects are a different concept related to tissue heating, not a type of cavitation.
Reference:
"Diagnostic Ultrasound: Principles and Instruments" by Frederick W. Kremkau ARDMS Sonography Principles and Instrumentation study materials

Axial resolution refers to the ability to distinguish two structures that are close to each other along the direction of the sound beam. It is determined by the spatial pulse length (SPL), which is the product of the number of cycles in a pulse and the wavelength. Shorter SPL means shorter pulse duration, which leads to better axial resolution. This is because shorter pulses allow for better separation of echoes from closely spaced structures.
Reference:
ARDMS Sonography Principles and Instrumentation guidelines
Kremkau, F. W. (2015). Diagnostic Ultrasound: Principles and Instruments.