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.
Description
Average SAR is absorbed RF energy divided by elapsed averaging time and exposed mass.
Average SAR is absorbed RF energy divided by elapsed averaging time and exposed mass. Its units are watts per kilogram.
The tool returns averageSarWattsPerKg (average sar watts per kg); exceedsComparisonLevel (exceeds comparison level). Input measurements and model parameters are supplied by the caller; the tool computes the stated summary rather than acquiring those measurements.
When to use Specific Absorption Rate SAR
Use Specific Absorption Rate SAR when you already have absorbedRfEnergiesJ, averagingWindowSeconds, exposedMassKg, comparisonLevelWattsPerKg and want averageSarWattsPerKg, exceedsComparisonLevel. This is useful for checking a supplied calculation, documenting a measurement convention, or comparing observations prepared on the same basis.
How to use Specific Absorption Rate SAR and understand its results
- Enter absorbedRfEnergiesJ, averagingWindowSeconds, exposedMassKg, comparisonLevelWattsPerKg 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 averageSarWattsPerKg, exceedsComparisonLevel. 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 |
|---|---|---|---|
| absorbedRfEnergiesJ | Absorbed rf energies j | list of number | Required |
| averagingWindowSeconds | Averaging window seconds | number | Required |
| exposedMassKg | Exposed mass kg | number | Required |
| comparisonLevelWattsPerKg | Comparison level watts per kg | number | Required |
Use nonempty nonnegative energies and positive window, mass and comparison level. Flag SAR strictly above the comparison; equality is not an exceedance.
SAR = ΣabsorbedEnergyJ/(windowSeconds×massKg) The symbols refer to the supplied quantities or generated values described above; unit conversions and comparison boundaries follow the stated implementation.
{
"input": {
"absorbedRfEnergiesJ": [
10,
20
],
"averagingWindowSeconds": 10,
"exposedMassKg": 5,
"comparisonLevelWattsPerKg": 1
},
"output": {
"averageSarWattsPerKg": 0.6,
"exceedsComparisonLevel": false
}
}Limitations and assumptions
Absorbed energy is supplied rather than derived from scanner settings. The chosen comparison is not an automatically selected regulatory limit.
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
Local 10g SAR: Compute local SAR for caller-supplied spatial 10-gram voxel-fraction regions; does not construct IEC-compliant regions, solve RF fields, or certify scanner safety. 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.
Methodological background: Protection of patients and volunteers undergoing MRI procedures.1
References
-
Protection of patients and volunteers undergoing MRI procedures — UK Health Protection Agency
Similar or alternative tools
- Local 10g SAR
Compute local SAR for caller-supplied spatial 10-gram voxel-fraction regions; does not construct IEC-compliant regions, solve RF fields, or certify scanner safety.
- 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.