When is the resolution of echoes at its greatest?

Resolution of echoes refers to the ability to distinguish between two points or two structures within an image. In ultrasound imaging, this resolution is affected by factors such as the depth of the echo source and the frequency of the ultrasound waves.

When an echo source is located within the near field, the ultrasound beam is narrower and provides better lateral resolution. This is due to the focusing effect of the transducer, which makes it easier to discriminate between adjacent structures. In the near field, the ultrasound waves have not yet spread too widely, allowing for a clearer distinction between closely located echoes.

Conversely, in the far field, the beam diverges, leading to decreased lateral resolution and making it more challenging to differentiate small structures. High-frequency ultrasound does improve resolution overall but is not the sole determinant of resolution at varying depths. While larger anatomical structures may be easier to visualize due to their size, they do not inherently improve the resolution of the echoes themselves.

Thus, resolution is at its greatest when the echo source is within the near field, which enhances the ability to discern details in the imaging.