Readout Field of View
Derive frequency-encoding FOV from full signed-span receiver bandwidth and constant readout gradient, not a pixels-times-spacing lookup.
Description
Readout field of view relates total receiver bandwidth to the frequency variation produced by the readout gradient.
Readout field of view relates total receiver bandwidth to the frequency variation produced by the readout gradient.
The tool returns readoutFovMm (readout fov 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 Readout Field of View
Use Readout Field of View when you already have receiverBandwidthHz, gammaHzPerTesla, readoutGradientMilliTeslaPerMeter and want readoutFovMm. This is useful for checking a supplied calculation, documenting a measurement convention, or comparing observations prepared on the same basis.
How to use Readout Field of View and understand its results
- Enter receiverBandwidthHz, gammaHzPerTesla, readoutGradientMilliTeslaPerMeter 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 readoutFovMm. 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 |
|---|---|---|---|
| receiverBandwidthHz | Receiver bandwidth hz | number | Required |
| gammaHzPerTesla | Gamma hz per tesla | number | Required |
| readoutGradientMilliTeslaPerMeter | Readout gradient milli tesla per meter | number | Required |
Require positive total bandwidth, gamma and gradient magnitude.
FOVmm = 10⁶×bandwidthHz/(gammaHzPerTesla×gradientMilliTeslaPerMeter) The symbols refer to the supplied quantities or generated values described above; unit conversions and comparison boundaries follow the stated implementation.
{
"input": {
"receiverBandwidthHz": 2560,
"gammaHzPerTesla": 1000000,
"readoutGradientMilliTeslaPerMeter": 10
},
"output": {
"readoutFovMm": 256
}
}Limitations and assumptions
The bandwidth must be the full acquired span under the stated convention. No oversampling or reconstructed cropping is inferred.
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
Bandwidth Per Pixel: Convert full-span ADC receiver bandwidth to frequency-encoding bandwidth per reconstructed readout sample; vendor half-bandwidth conventions must be converted first. Gradient Amplitude Required: Derive constant readout gradient from desired k-space traversal span and duration; prephasers, ramps and gradient hardware feasibility are excluded.
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
- Bandwidth Per Pixel
Convert full-span ADC receiver bandwidth to frequency-encoding bandwidth per reconstructed readout sample; vendor half-bandwidth conventions must be converted first.
- Gradient Amplitude Required
Derive constant readout gradient from desired k-space traversal span and duration; prephasers, ramps and gradient hardware feasibility are excluded.