Decreasing the FOV of a scan will have what effect on the SNR?

• A. SNR will increase
• B. SNR will stay the same
• C. SNR will decrease
• D. SNR will fluctuate

Answer: (C)

Decreasing the Field of View (FOV) in an MRI scan leads to an increase in spatial resolution, but it also affects the Signal-to-Noise Ratio (SNR). The SNR is fundamentally influenced by the amount of signal collected relative to the amount of noise present in the image.

When the FOV is decreased, the area being scanned is reduced, meaning that for the same number of received signals, the noise is being concentrated in a smaller region. This can lead to a decrease in the overall signal strength relative to the noise level. As a result, the noise becomes more significant when compared to the signal, which causes the SNR to decrease.

This principle is critical in MRI imaging, as a higher FOV typically allows for more signal averaging over a larger area, which helps to improve SNR. Hence, when you decrease the FOV without adjusting other parameters such as acquisition time or the number of averages, the SNR will not improve and may indeed get worse. This understanding is crucial for technologists when optimizing scan parameters for better image quality.