Temporal resolution refers to the ability of an ultrasound system to distinguish between events occurring closely in time. It is primarily affected by the frame rate, which is the number of frames displayed per second. One of the main factors that influence the frame rate is the display depth. The deeper the imaging depth, the longer it takes for the ultrasound pulses to travel to the target and back, thus reducing the frame rate and temporal resolution. Shallower imaging depths allow for higher frame rates and better temporal resolution.

Reference

ARDMS Sonography Principles and Instrumentation (SPI) Exam Study Guide

'Diagnostic Ultrasound: Principles and Instruments' by Frederick W. Kremkau