How is SNR affected by increasing the number of averages in an MRI scan?

• A. Increases SNR
• B. Decreases SNR
• C. No change in SNR
• D. Causes aliasing artifacts

Answer: (A)

Increasing the number of averages in an MRI scan improves the Signal-to-Noise Ratio (SNR). SNR is a measure that compares the level of the desired signal to the level of background noise. By taking multiple averages of the acquired data during the imaging process, the actual signal becomes stronger relative to random noise. This averaging helps to filter out the noise, leading to a clearer and more defined image.

The concept relies on statistical principles: when you average multiple measurements, the random noise gets reduced because it tends to fluctuate, while the true signal remains consistent. Hence, as the number of averages rises, the SNR increases, leading to improved image quality.

While other factors contribute to SNR, such as TR (repetition time), TE (echo time), and the magnetic field strength, the core principle of averaging enhancing SNR holds true across various MRI sequences and techniques.