Factors Affecting Temporal Resolution
Speed of hemodynamic response to electrical activity
- typically a 4 to 8 second rise to full amplitude
T1 recovery time of magnetisation
- for EPI, should leave ideally > T1 between acquisitions of the same slice (T1?1?1.5s)
Speed of scanner image acquisition
- gradient duty cycle, peripheral nerve stimulation by fast-switching field gradients limits to < 10 images/sec.
Signal (contrast) to noise ratio
- insufficient TR or short stimulus duration leads to low CNR