How does the calculation for scan time in a fast/turbo spin echo compare to a spin echo?

In fast or turbo spin echo sequences, the calculation of scan time differs notably from that of conventional spin echo sequences. The correct approach for calculating scan time in a fast or turbo spin echo sequence involves factoring in the echo train length. The echo train length refers to the number of consecutive echoes that are collected for each excitation pulse.

In a standard spin echo, each excitation pulse leads to the acquisition of a single echo, so the scan time is primarily determined by the repetition time (TR) and the number of slices. However, in fast spin echo sequences, multiple echoes are captured with each excitation, significantly affecting the overall scan time.

By dividing the overall TR by the echo train length, you effectively reduce the scan time because multiple data points are obtained with each TR period. This is a key advantage of fast spin echo techniques, allowing for faster imaging while still maintaining image quality.

Understanding this relationship helps radiographers and technologists optimize scan parameters for efficiency without compromising diagnostic utility. In summary, recognizing the impact of echo train length on scan time calculations is crucial for the effective use of fast spin echo sequences in clinical practice.