Final answer:
To improve lateral resolution in an ultrasound image, increasing the focal zone number is the most effective method from the given options, as it enhances detail and clarity by focusing the beam in multiple areas across different depths.
Step-by-step explanation:
The question pertains to improving lateral resolution in imaging, a concept related to ultrasound physics. To enhance lateral resolution, we can increase the frequency of the transducer. Higher frequency sound waves are more capable of differentiating between objects that are close together, which directly improves lateral resolution. However, among the given options, increasing the focal zone number is the best choice. More focal zones in an ultrasound image can lead to better resolution because the beam is focused in more places, leading to improved detail and clarity at various depths. Adjusting dynamic range affects contrast resolution, while decreasing the pulse repetition frequency (PRF) would affect temporal resolution, not lateral resolution. Decreasing transducer frequency would actually worsen lateral resolution.