Slice Thickness
Compute nominal slice thickness from RF bandwidth and slice-select gradient in explicit Hz/T and mT/m units; RF profile and off-resonance effects are not modeled.
Description
Slice selection maps RF frequency bandwidth into spatial thickness through a gradient.
Slice selection maps RF frequency bandwidth into spatial thickness through a gradient. Wider RF bandwidth or a weaker gradient increases the ideal slice thickness.
The tool returns thicknessMm (thickness mm). Input measurements and model parameters are supplied by the caller; the tool computes the stated summary rather than acquiring those measurements.
When to use Slice Thickness
Use Slice Thickness when you already have rfBandwidthHz, gammaHzPerTesla, sliceGradientMilliTeslaPerMeter and want thicknessMm. This is useful for checking a supplied calculation, documenting a measurement convention, or comparing observations prepared on the same basis.
How to use Slice Thickness and understand its results
- Enter rfBandwidthHz, gammaHzPerTesla, sliceGradientMilliTeslaPerMeter using the field table below. Match the units, ordering and data boundaries described in the calculation.
- Run the tool after checking the stated bounds and matching paired observations or categories. A malformed request gives a tool error rather than a usable measurement.
- Read thicknessMm. Use the calculation and interpretation below to distinguish amounts, ratios, signs and decision flags where applicable.
- Review the supplied parameters and assumptions before using the result in a report or comparing it with another observation.
| Input field | Meaning | Value type and bounds | Requirement |
|---|---|---|---|
| rfBandwidthHz | Rf bandwidth hz | number | Required |
| gammaHzPerTesla | Gamma hz per tesla | number | Required |
| sliceGradientMilliTeslaPerMeter | Slice gradient milli tesla per meter | number | Required |
Use positive bandwidth, gamma and gradient magnitude. The 10⁶ factor accounts for mT and mm conversions.
thicknessMm = 10⁶×RFbandwidthHz/(gammaHzPerTesla×gradientMilliTeslaPerMeter) The symbols refer to the supplied quantities or generated values described above; unit conversions and comparison boundaries follow the stated implementation.
{
"input": {
"rfBandwidthHz": 2000,
"gammaHzPerTesla": 1000000,
"sliceGradientMilliTeslaPerMeter": 10
},
"output": {
"thicknessMm": 200
}
}Limitations and assumptions
This is an ideal bandwidth-to-thickness calculation, without RF pulse profile, off-resonance or gradient nonlinearity correction.
Numerical inputs must be finite. The tool checks its declared input shape and calculation constraints; those checks do not verify the quality, calibration or representativeness of the supplied observations.
Alternative or Complementary methods
Slice Gap: Audit adjacent slice edge gaps and overlaps along a common slice-normal axis; centers and physical slice thicknesses share millimetre units. Readout Field of View: Derive frequency-encoding FOV from full signed-span receiver bandwidth and constant readout gradient, not a pixels-times-spacing lookup.
Methodological background: RAD229: MRI signal and sequence lecture notes.1
References
-
RAD229: MRI signal and sequence lecture notes — Brian Hargreaves and colleagues, Stanford University
Similar or alternative tools
- Slice Gap
Audit adjacent slice edge gaps and overlaps along a common slice-normal axis; centers and physical slice thicknesses share millimetre units.
- Readout Field of View
Derive frequency-encoding FOV from full signed-span receiver bandwidth and constant readout gradient, not a pixels-times-spacing lookup.