How is the quality factor defined in ultrasound?

The quality factor in ultrasound is defined as the ratio of the operating frequency to the bandwidth of the transducer. This concept is crucial in understanding how effectively a transducer can operate within a given frequency range. The operating frequency refers to the central frequency at which the transducer is designed to emit sound waves, while the bandwidth indicates the range of frequencies around the center frequency that the transducer can efficiently transmit.

A higher quality factor means that the transducer is more selective, operating predominantly at its center frequency and less effectively at frequencies outside of its bandwidth. In clinical practice, this selection is important because it affects imaging resolution and the ability to differentiate between structures of different sizes.

The other options do not accurately represent the relationship between operating frequency and bandwidth as it pertains to the quality factor, thus reinforcing why the correct answer is to divide the operating frequency by the bandwidth. This relationship highlights the ability of ultrasound equipment to focus on specific frequency ranges, thereby maximizing imaging performance.