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 and does not work yet on IOS devices. It will work on Android 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.
TR – the repetition time of the sequence in milliseconds.
TE/echo sp – Echo time or (for fast/turbo spin echo) the inter-echo spacing. 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 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.