Final answer:
Increasing the imaging depth will decrease temporal resolution, while decreasing the number of focal zones and using a narrow sector size will increase it. Using a low line density affects spatial resolution instead of temporal resolution.
Correct option is a. Increase the imaging depth.
Step-by-step explanation:
The action that will NOT increase (or improve) temporal resolution is 'a. Increase the imaging depth.' Increasing the imaging depth will generally decrease the temporal resolution because the ultrasound system needs more time to wait for the echo to return from deeper tissues before sending out the next pulse. As for the other options, 'b. Decrease the number of focal zones' will improve temporal resolution because fewer focal zones mean less time spent on scanning each individual zone. 'c. Use a sector size that is narrow' will also increase temporal resolution, as the system needs to scan a smaller area, which can be done more rapidly. Lastly, 'd. Use a low line density' would decrease the spatial resolution, not the temporal resolution. Temporal resolution is concerned with how quickly data can be acquired, whereas line density affects clarity and detail of the image (spatial resolution).