What effect does decreasing the FOV of a scan have on the SNR?

Decreasing the field of view (FOV) in an MRI scan generally leads to a decrease in signal-to-noise ratio (SNR). This phenomenon can be understood through the principles of how images are formed in MRI.

When the FOV is reduced, the same amount of signal is now concentrated over a smaller area. This increased signal concentration could seem beneficial; however, it actually results in a lower SNR because the noise, which is random and evenly distributed throughout the scan, does not decrease in parallel with the signal. Essentially, while the signal might be higher per unit area, the overall noise does not diminish proportionately, leading to a lower SNR.

SNR is a critical factor in MRI, as it influences the quality of the images produced. A lower SNR means that the images may have more noise, making it harder to distinguish between actual signals from tissues and the background noise, which could lead to diagnostic challenges. Thus, the impact of reducing the FOV relates closely to balancing image resolution and SNR for optimal diagnostic utility.