Normalized Hippocampal Volume
Report bilateral hippocampal volume, ICV fraction and regression-based ICV adjustment using a supplied normative slope and reference; segmentation validity is external.
Description
Hippocampal volume can be normalized by intracranial volume or adjusted using a supplied regression slope and reference head size.
Hippocampal volume can be normalized by intracranial volume or adjusted using a supplied regression slope and reference head size. These conventions answer different questions.
The tool returns bilateralVolumeMm3 (bilateral volume mm3); icvFraction (icv fraction); regressionAdjustedVolumeMm3 (regression adjusted volume mm3). Input measurements and model parameters are supplied by the caller; the tool computes the stated summary rather than acquiring those measurements.
When to use Normalized Hippocampal Volume
Use Normalized Hippocampal Volume when you already have leftVolumeMm3, rightVolumeMm3, intracranialVolumeMm3, referenceIntracranialVolumeMm3, regressionSlope and want bilateralVolumeMm3, icvFraction, regressionAdjustedVolumeMm3. This is useful for checking a supplied calculation, documenting a measurement convention, or comparing observations prepared on the same basis.
How to use Normalized Hippocampal Volume and understand its results
- Enter leftVolumeMm3, rightVolumeMm3, intracranialVolumeMm3, referenceIntracranialVolumeMm3, regressionSlope 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 bilateralVolumeMm3, icvFraction, regressionAdjustedVolumeMm3. 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 |
|---|---|---|---|
| leftVolumeMm3 | Left volume mm3 | number | Required |
| rightVolumeMm3 | Right volume mm3 | number | Required |
| intracranialVolumeMm3 | Intracranial volume mm3 | number | Required |
| referenceIntracranialVolumeMm3 | Reference intracranial volume mm3 | number | Required |
| regressionSlope | Regression slope | number | Required |
Sum nonnegative regional volumes, require positive ICV and reference ICV, and reject a bilateral volume greater than ICV.
ICV fraction = bilateral/ICV; adjusted = bilateral−slope×(ICV−referenceICV) The symbols refer to the supplied quantities or generated values described above; unit conversions and comparison boundaries follow the stated implementation.
{
"input": {
"leftVolumeMm3": 3000,
"rightVolumeMm3": 3200,
"intracranialVolumeMm3": 1400000,
"referenceIntracranialVolumeMm3": 1500000,
"regressionSlope": 0.004
},
"output": {
"bilateralVolumeMm3": 6200,
"icvFraction": 0.004428571428571428,
"regressionAdjustedVolumeMm3": 6600
}
}Limitations and assumptions
The regression slope is supplied, not learned. The adjusted result is not clipped and is not an age- or disease-specific normative percentile.
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
Hippocampal Atrophy Rate: Fit all supplied longitudinal bilateral hippocampal volumes in log and linear space; signed annual log change and signed volume loss preserve growth rather than forcing atrophy. Lesion Volume: Integrate lesion voxel fractions using anisotropic voxel dimensions; segmentation and partial-volume probabilities must be supplied.
Methodological background: Least squares estimation.1
References
-
Least squares estimation — NIST/SEMATECH
Similar or alternative tools
- Hippocampal Atrophy Rate
Fit all supplied longitudinal bilateral hippocampal volumes in log and linear space; signed annual log change and signed volume loss preserve growth rather than forcing atrophy.
- Lesion Volume
Integrate lesion voxel fractions using anisotropic voxel dimensions; segmentation and partial-volume probabilities must be supplied.