Which two factors determine spatial pulse length?

Which two factors determine spatial pulse length?

• A. The transducer type only
• B. The source and the medium
• C. The patient type only
• D. The measurement instrument

Answer: (B)

Spatial pulse length is determined by how long the pulse lasts in space, which depends on two things: how many cycles are in the pulse and the distance each cycle travels (the wavelength). The wavelength in tissue is set by the speed of sound in the medium, while the number of cycles is set by the emitted pulse from the source (the transducer). Put simply, SPL = (number of cycles in the pulse) × (wavelength), and wavelength = speed of sound in the medium ÷ transmitted frequency. So the two factors that determine spatial pulse length are the source (the transmitted frequency) and the medium (the speed of sound). The patient type or the measurement instrument don’t set SPL themselves.

Spatial pulse length is determined by how long the pulse lasts in space, which depends on two things: how many cycles are in the pulse and the distance each cycle travels (the wavelength). The wavelength in tissue is set by the speed of sound in the medium, while the number of cycles is set by the emitted pulse from the source (the transducer). Put simply, SPL = (number of cycles in the pulse) × (wavelength), and wavelength = speed of sound in the medium ÷ transmitted frequency. So the two factors that determine spatial pulse length are the source (the transmitted frequency) and the medium (the speed of sound). The patient type or the measurement instrument don’t set SPL themselves.