What is the unit of spatial pulse length?

Spatial pulse length is defined as the length of a pulse of ultrasound as it travels through the medium. It is calculated as the product of the number of cycles in the pulse and the wavelength of those cycles. Since spatial pulse length refers to a physical distance, it is expressed in meters or other units of length.

In ultrasound, spatial pulse length is crucial because it affects the axial resolution, which is the ability to distinguish between two structures that are close together along the direction of the ultrasound beam. A shorter spatial pulse length generally improves resolution and provides clearer images.

The other units presented in the choices have different definitions: seconds measure time, decibels measure intensity levels in a logarithmic scale, and hertz measure frequency, which relates to the number of cycles per second. None of these directly relate to the spatial dimension that is being described by spatial pulse length.