Which of the following contributes to the resolution of an ultrasound image?

Resolution in an ultrasound image is influenced by various factors, making the choice of "all of the above" the most comprehensive answer.

Spatial pulse length is crucial because it directly affects axial resolution. A shorter spatial pulse length results in better resolution, allowing for finer details to be distinguished in the image. This ultimately enhances the quality and clarity of the structures being examined.

Pulse repetition frequency (PRF) also plays a role, although it primarily affects frame rate and can indirectly influence the resolution by allowing more frames to be captured per second. This can lead to a smoother and more precise representation of motion and dynamic structures, which is important in imaging.

The number of cycles in a pulse influences the lateral resolution. A pulse with fewer cycles tends to be more focused and results in narrower beam widths, which helps in distinguishing two closely spaced structures.

Therefore, all these factors—spatial pulse length, pulse repetition frequency, and number of cycles—contribute to the overall resolution of an ultrasound image, making "all of the above" the correct choice.