What is the effect on SNR when the receiver bandwidth of a pulse sequence is reduced?

• A. SNR increases
• B. SNR decreases
• C. SNR remains unchanged
• D. SNR is inconsistent

Answer: (A)

When the receiver bandwidth of a pulse sequence is reduced, the signal-to-noise ratio (SNR) increases. This happens because a narrower bandwidth allows for the collection of signals with better fidelity, as it effectively allows more of the true signal’s energy to be captured while simultaneously filtering out some of the noise present in the wider bandwidth.

The relationship between bandwidth and SNR is crucial in magnetic resonance imaging (MRI). A reduced receiver bandwidth means that fewer frequency components are being sampled, which directly enhances the SNR. This is because the noise in MRI is typically uniformly distributed across the frequency spectrum. By narrowing the bandwidth, the overall amount of noise being captured is decreased relative to the desired signal, thus improving the SNR.

In many imaging scenarios, an increase in SNR can lead to better image quality and contrast, allowing for clearer differentiation between tissue types. This concept is particularly important for optimizing pulse sequences where image quality is paramount.