SNR and Receiver Bandwidth
A wider bandwidth includes more noise. Remember that bandwidth (BW) = Nx / Tline where Nx is the number of frequency encoding steps and Tline is the total sampling time for a whole line of k-space. Decreasing the bandwidth by a factor of 2 results in an increase in the SNR by a factor of √2. Again, just use the SNR equation.
The confusing subject of receiver bandwidth is addressed in the receiver bandwidth tutorial.
- increases chemical shift artefact (see the chemical shift tutorial)
- longer TE (sampling time is inversely proportional to BW. A longer TE means more time for T2 dephasing, reducing SNR. However, the reduction noise contamination as a result of a smaller receiver bandwidth outweighs the decrease in SNR from the extra T2 dephasing, and overall the SNR goes up.)
- decreases number of slices (longer TE means fewer slices can be fitted into the TR period).