TR and TE are typically expressed in ______.

TR and TE are typically expressed in ______.

• A. Seconds
• B. Milliseconds (ms)
• C. Microseconds
• D. Nanoseconds

Answer: (B)

TR and TE are measured in milliseconds because these timing values reflect how MRI pulse sequences and the resulting echoes unfold over short, practical time spans. TR, the interval between successive radiofrequency excitations, and TE, the delay from excitation to the echo, both occur during tissue relaxation and signal formation that typically happen within tens to hundreds of milliseconds. Using seconds would be too coarse for controlling and comparing sequences, while microseconds or nanoseconds are far too precise for the imaging processes involved. In common sequences, TR often ranges from a few hundred to a couple thousand milliseconds and TE from about 10 to a few dozen milliseconds, illustrating why milliseconds are the standard unit.

TR and TE are measured in milliseconds because these timing values reflect how MRI pulse sequences and the resulting echoes unfold over short, practical time spans. TR, the interval between successive radiofrequency excitations, and TE, the delay from excitation to the echo, both occur during tissue relaxation and signal formation that typically happen within tens to hundreds of milliseconds. Using seconds would be too coarse for controlling and comparing sequences, while microseconds or nanoseconds are far too precise for the imaging processes involved. In common sequences, TR often ranges from a few hundred to a couple thousand milliseconds and TE from about 10 to a few dozen milliseconds, illustrating why milliseconds are the standard unit.