Which parameter adjustments will LENGTHEN scan time in an MR pulse sequence?

Increasing the repetition time (TR) in an MR pulse sequence lengthens the scan time. TR refers to the time interval between successive pulse sequences applied to the same slice. When TR is increased, it allows more time for the protons to relax between pulse sequences, which can improve image contrast and signal-to-noise ratio (SNR), particularly in T1-weighted imaging.

Since more time is required before the next pulse sequence can be applied, this directly affects the overall duration of the scan. This contrasts with other parameters such as decreasing TR, which would shorten the time, or decreasing the number of excitations (NEX), which would also reduce the overall scan time. Enabling half-fourier also optimizes scan efficiency and can help decrease scan time by using less data than a full Fourier transform would require. Therefore, increasing TR is the correct approach for lengthening scan time in an MR pulse sequence.