What two factors primarily determine frame rate in ultrasound imaging?

Frame rate in ultrasound imaging is primarily determined by the speed of sound in the medium and the depth of the image being obtained. Sound speed is crucial because it influences how quickly the ultrasound waves travel through the tissue to return to the transducer. In a medium like soft tissue, for instance, sound travels at approximately 1540 meters per second.

When considering depth, as the depth of the imaging area increases, the time it takes for the ultrasound pulse to travel to the deeper tissues and return also increases. This longer travel time reduces the number of frames that can be captured in a second, which means a lower frame rate. Consequently, for deeper structures, the frame rate tends to be lower due to the increased distance the waves must cover.

Other factors mentioned in the other answer choices, such as image resolution, patient size, frequency of the ultrasound, or operator skill, play roles in different aspects of ultrasound performance but do not directly determine the frame rate. Frame rate is fundamentally dependent on how quickly pulses can occur, which directly ties back to sound speed in the imaging medium and the distances being scanned.