Axial resolution in ultrasound is primarily determined by what factor?

Axial resolution in ultrasound is primarily determined by spatial pulse length. Axial resolution refers to the ability of an ultrasound system to distinguish between two structures that are positioned along the direction of the sound beam. The smaller the spatial pulse length, the better the axial resolution because it allows for the detection of closely spaced structures.

Spatial pulse length is directly influenced by the number of cycles in the pulse and the wavelength of the ultrasound waves. A shorter spatial pulse length results in improved distinction between reflectors located closely together. This is crucial in clinical practice, as better axial resolution leads to clearer imaging and more accurate diagnoses.

Although transducer frequency also plays a role in spatial pulse length—higher frequencies generally produce shorter wavelengths, leading to better resolution—the fundamental determination of axial resolution hinges on the spatial pulse length itself. Therefore, choice regarding the relationship between spatial pulse length and axial resolution accurately reflects the underlying physics of ultrasound imaging.