Peripheral Nerve Stimulation Threshold
Screen a supplied gradient ramp against an externally calibrated strength-duration model; coil geometry, body coupling and multi-axis effects are not modeled, so this is not a patient safety determination.
Description
A calibrated strength-duration model expresses a stimulation threshold as a rheobase term modified by ramp duration and chronaxie.
A calibrated strength-duration model expresses a stimulation threshold as a rheobase term modified by ramp duration and chronaxie. Comparing slew with that threshold gives a model fraction.
The tool returns modelThresholdSlew (model threshold slew); thresholdFraction (threshold fraction); aboveModelThreshold (above model threshold). Input measurements and model parameters are supplied by the caller; the tool computes the stated summary rather than acquiring those measurements.
When to use Peripheral Nerve Stimulation Threshold
Use Peripheral Nerve Stimulation Threshold when you already have observedSlewTeslaPerMeterSecond, rheobaseSlewTeslaPerMeterSecond, rampDurationMicroseconds, chronaxieMicroseconds and want modelThresholdSlew, thresholdFraction, aboveModelThreshold. This is useful for checking a supplied calculation, documenting a measurement convention, or comparing observations prepared on the same basis.
How to use Peripheral Nerve Stimulation Threshold and understand its results
- Enter observedSlewTeslaPerMeterSecond, rheobaseSlewTeslaPerMeterSecond, rampDurationMicroseconds, chronaxieMicroseconds 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 modelThresholdSlew, thresholdFraction, aboveModelThreshold. 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 |
|---|---|---|---|
| observedSlewTeslaPerMeterSecond | Observed slew tesla per meter second | number | Required |
| rheobaseSlewTeslaPerMeterSecond | Rheobase slew tesla per meter second | number | Required |
| rampDurationMicroseconds | Ramp duration microseconds | number | Required |
| chronaxieMicroseconds | Chronaxie microseconds | number | Required |
Use nonnegative observed slew and chronaxie, positive rheobase and ramp duration. Flag a fraction strictly above one.
threshold = rheobaseSlew×(1+chronaxie/rampDuration); fraction = observedSlew/threshold The symbols refer to the supplied quantities or generated values described above; unit conversions and comparison boundaries follow the stated implementation.
{
"input": {
"observedSlewTeslaPerMeterSecond": 12,
"rheobaseSlewTeslaPerMeterSecond": 10,
"rampDurationMicroseconds": 200,
"chronaxieMicroseconds": 100
},
"output": {
"modelThresholdSlew": 15,
"thresholdFraction": 0.8,
"aboveModelThreshold": false
}
}Limitations and assumptions
Calibration must be specific to the intended system and context. This simplified screen does not determine individual stimulation or scanner safety compliance.
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
Gradient Slew Rate: Measure signed piecewise-linear gradient slew from timestamped mT/m samples; mT/m per ms equals T/m/s and between-sample excursions are not observable. Specific Absorption Rate SAR: Summarize supplied absorbed RF energy over an explicit time window and mass; a caller comparison level is not a scanner safety certification or regulatory recommendation.
Methodological background: Influence of peripheral axon geometry and local anatomy on magnetostimulation chronaxie.1
References
-
Influence of peripheral axon geometry and local anatomy on magnetostimulation chronaxie — Ferris et al.; Journal of Neural Engineering
Similar or alternative tools
- Gradient Slew Rate
Measure signed piecewise-linear gradient slew from timestamped mT/m samples; mT/m per ms equals T/m/s and between-sample excursions are not observable.
- Specific Absorption Rate SAR
Summarize supplied absorbed RF energy over an explicit time window and mass; a caller comparison level is not a scanner safety certification or regulatory recommendation.