Spin Echo Signal Intensity
Evaluate an ideal saturation-recovery spin-echo signal M0(1−e^(−TR/T1))e^(−TE/T2); refocusing imperfections and stimulated echoes are excluded.
Description
An ideal spin-echo signal combines longitudinal recovery during TR with transverse decay during TE.
An ideal spin-echo signal combines longitudinal recovery during TR with transverse decay during TE. The two relaxation times control different contrast contributions.
The tool returns signalAmplitude (signal amplitude). Input measurements and model parameters are supplied by the caller; the tool computes the stated summary rather than acquiring those measurements.
When to use Spin Echo Signal Intensity
Use Spin Echo Signal Intensity when you already have equilibriumAmplitude, trMs, t1Ms, teMs, t2Ms and want signalAmplitude. This is useful for checking a supplied calculation, documenting a measurement convention, or comparing observations prepared on the same basis.
How to use Spin Echo Signal Intensity and understand its results
- Enter equilibriumAmplitude, trMs, t1Ms, teMs, t2Ms 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 signalAmplitude. 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 |
|---|---|---|---|
| equilibriumAmplitude | Equilibrium amplitude | number | Required |
| trMs | Tr ms | number | Required |
| t1Ms | T1 ms | number | Required |
| teMs | Te ms | number | Required |
| t2Ms | T2 ms | number | Required |
Use nonnegative amplitude, positive TR/T1/T2 and 0≤TE<TR, with all times in ms.
S = M0(1−exp(−TR/T1))exp(−TE/T2) The symbols refer to the supplied quantities or generated values described above; unit conversions and comparison boundaries follow the stated implementation.
{
"input": {
"equilibriumAmplitude": 100,
"trMs": 1000,
"t1Ms": 1000,
"teMs": 100,
"t2Ms": 100
},
"output": {
"signalAmplitude": 23.254415793482963
}
}Limitations and assumptions
Ideal excitation and refocusing are assumed. Stimulated echoes, flow, diffusion and pulse imperfections are not modelled.
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
SPGR Signal Intensity: Evaluate ideal fully spoiled gradient-echo steady-state signal with explicit T2* attenuation; receiver gain is included in caller equilibrium amplitude. Echo Time TE: Audit ideal Hahn-echo center timing against a supplied ADC echo center; finite pulse widths, gradient echoes and off-resonance phase are not solved.
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
- SPGR Signal Intensity
Evaluate ideal fully spoiled gradient-echo steady-state signal with explicit T2* attenuation; receiver gain is included in caller equilibrium amplitude.
- Echo Time TE
Audit ideal Hahn-echo center timing against a supplied ADC echo center; finite pulse widths, gradient echoes and off-resonance phase are not solved.