Spatial Pulse Length is determined by which factors?

Spatial Pulse Length is determined by which factors?

• A. Number of cycles in the pulse
• B. Wavelength
• C. Frequency
• D. Both the number of cycles in the pulse and the wavelength

Answer: (D)

Spatial pulse length is the physical length of the ultrasound pulse in tissue. It is determined by how many cycles are contained in the transmitted burst and by how long each cycle extends in space, i.e., the wavelength. If you increase the number of cycles, SPL grows proportionally. If you increase the wavelength (for example, by lowering the frequency or changing tissue speed), SPL also grows. Since wavelength is tied to frequency through λ = c/f in tissue, SPL can depend on frequency indirectly, but directly it depends on the number of cycles and the wavelength. Therefore, it is determined by both the number of cycles in the pulse and the wavelength.