Pulse length is determined by which factors?

Pulse length is determined by which factors?

• A. The transducer only
• B. The patient only
• C. Both the source and the medium
• D. The frequency setting only

Answer: (C)

Pulse length is the distance from the start to the end of a single ultrasound pulse, and it depends on both the source and the medium. This length equals the number of cycles in the pulse multiplied by the wavelength of those cycles. The wavelength, in turn, is speed of sound in the medium divided by the transmitted frequency. So the source sets how many cycles are in a pulse and the frequency you’re using, while the medium fixes how fast sound travels and thus the wavelength. Together, they determine the pulse length. For example, in soft tissue the speed is about 1540 m/s; at a given frequency (say 5 MHz) the wavelength is around 0.31 mm, and multiplying by the number of cycles in the pulse gives the final pulse length. That’s why both the source and the medium matter.

Pulse length is the distance from the start to the end of a single ultrasound pulse, and it depends on both the source and the medium. This length equals the number of cycles in the pulse multiplied by the wavelength of those cycles. The wavelength, in turn, is speed of sound in the medium divided by the transmitted frequency. So the source sets how many cycles are in a pulse and the frequency you’re using, while the medium fixes how fast sound travels and thus the wavelength. Together, they determine the pulse length. For example, in soft tissue the speed is about 1540 m/s; at a given frequency (say 5 MHz) the wavelength is around 0.31 mm, and multiplying by the number of cycles in the pulse gives the final pulse length. That’s why both the source and the medium matter.