How does increasing the repetition time (TR) influence the SNR?

• A. SNR decreases
• B. SNR is unaffected
• C. SNR increases
• D. SNR becomes inconsistent

Answer: (C)

Increasing the repetition time (TR) has a direct and positive impact on the signal-to-noise ratio (SNR) in magnetic resonance imaging (MRI). When TR is lengthened, it allows for more time for the longitudinal magnetization of the tissues to recover before subsequent radiofrequency (RF) pulses are applied. With additional time for recovery, the signals from the tissues can be acquired at a higher strength, leading to clearer and stronger images.

As a result, the noise in the images becomes less significant compared to the useful signal, thus enhancing the overall SNR. In contrast, a shorter TR would not allow for adequate recovery of magnetization, potentially reducing the quality of the signal captured, hence diminishing the SNR. This is why an increase in TR is associated with enhanced SNR in MRI imaging.