Trade offs

Last revised by Andrew Murphy on 2 Apr 2020

Trade-offs exist when changing imaging parameters to obtain the best images possible. The SNR, resolution, and acquisition time, are all interrelated. Changing one effects the others. An important job of the radiologist and MR radiographer is to decide what factors are more important for an examination of a particular body part, patient and suspected abnormality.

 When looking at the pituitary or cranial nerves, for example, you may want to sacrifice some SNR or longer acquisition time for improved spatial resolution. On the other hand, in a claustrophobic of patient in pain who may be moving around, you may sacrifice both resolution and SNR for the shortest possible examination time. The table summarizes the trade offs between SNR, resolution, time, maximum number of slices and distance covered.

Summary of imaging parameter trade-offs
Increase Parameters below SNR Resolution Acquisition Time Distance Covered Max. Number of Slices
FOV  +       -       nc        nc         nc
NEX  +       nc       +        nc         nc
Slice Thick  +       -       nc        +         nc
Gap  +       -       nc        +         nc
TR  +       nc       +        nc         +
TE  -       nc       nc        nc         -
Matrix size  -       +       +        nc         nc
Bandwidth  -       nc       nc        nc         +
Magnet strength  +       nc       nc        nc         nc

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