Use the SNR and resolution calculator to investigate the effect of various parameter changes in MRI.
The calculator reports the relative (to default parameters) SNR, pixel size and scan time.
Note: this works best on a computer. It will also work on Android and IOS mobile devices.
Explanation of the parameters
No slices – number of 2D slices. The maximum value is indicated in italics. This will change as TR, TE/echo spacing and Turbo factor ETL is changed.
Slice width (mm) – the slice width or thickness. Default value is 5mm.
FOV – Image field of view in mm.
RFOV – rectangular field of view (phase FOV). Value of 1 indicates a square FOV.
Scan %/ phase res – the percentage of k-space (raw data) acquired. This affects SNR and pixel size.
Phase oversampling – an additional % of phase encode steps to reduce aliassing artefact. This changes scan time and SNR.
TR – the repetition time of the sequence in milliseconds.
TE – the echo time. This must be a multiple of the echo spacing.
Echo spacing – the minimum echo time for fast/turbo spin echo. This is restricted by bandwidth.
pix bw – the bandwidth per pixel in hertz (Hz). In Philips scanners this is denoted “water-fat pixel shift”. GE and Toshiba/Canon scanners operate an overall receive bandwidth regime (kHz).
PI reduction factor – this is the Reduction Factor in parallel imaging. Sometimes denoted SENSE factor or iPAT factor.
NSA/NEX – the number of signal averages or excitations.
Turbo/ETL – In fast/turbo spin echo, this is the number of echoes used for spacial encoding, or the “speed up” factor.