Cortical Expansion Ratio Calculator

Actual longitudinal cortical surface expansion ratio for compatible matched reconstructions; not cortical thickness or age-normalized growth. Independently measured compatible definitions/units required; ratio is not a diagnosis, efficacy measure or safety/clinical threshold.

Description

Cortical expansion ratio compares matched later and earlier surface areas.

Cortical expansion ratio compares matched later and earlier surface areas.^[1]

It describes proportional size rather than a time-normalized growth rate.

When to use Cortical Expansion Ratio Calculator

Use this tool to calculate or review the supplied observations under the stated rules. Establish the assessment or recording protocol, units, instrument version and independently applicable reference or calibration.

How to use Cortical Expansion Ratio Calculator and understand its results

Establish the assessment or recording protocol, units, instrument version and independently applicable reference or calibration.
Enter independentlyMeasuredLaterCorticalSurfaceArea, independentlyMeasuredEarlierCorticalSurfaceArea, using the field meanings and rules below, then run the tool.
Read result.observedRatio. Use the units and sign conventions below.
Correct any reported input issue and run again. Before using a successful result, check the stated units, signs, reference scope and observation coverage.

Input field	Meaning	Value type	Requirement
independentlyMeasuredLaterCorticalSurfaceArea	Independently measured later cortical surface area	number	Required
independentlyMeasuredEarlierCorticalSurfaceArea	Independently measured earlier cortical surface area	number	Required

Supply a nonnegative independentlyMeasuredLaterCorticalSurfaceArea and strictly positive independentlyMeasuredEarlierCorticalSurfaceArea. Divide the first by the second for a dimensionless ratio. The general ratio calculation does not clamp the result or require the numerator to be no greater than the denominator; a larger numerator can return above one. Establish matching observation scope and units independently.

observedRatio=1×independentlyMeasuredLaterCorticalSurfaceArea/independentlyMeasuredEarlierCorticalSurfaceArea

Use the matching field units and the exact boundary, ordering and reference rules above.

Output field	Meaning	Value type
result	Structured result; its nested fields below contain the actual calculation or selected reference	object
result.observedRatio	Observed Ratio; dimensionless ratio, without percent scaling	number

json

{
  "input": {
    "independentlyMeasuredLaterCorticalSurfaceArea": 2,
    "independentlyMeasuredEarlierCorticalSurfaceArea": 4
  },
  "output": {
    "result": {
      "observedRatio": 0.5
    }
  }
}

Limitations and assumptions

Actual acquisition, assessment protocol, instrument version and calibration determine applicability. The tool does not examine a person, classify images, administer a questionnaire or choose diagnostic cutoffs.

Missing required fields, unknown fields, wrong types and violated rules return input issues. Numeric values and outputs must be finite. Extremely large composite outputs are rejected.

Alternative or Complementary methods

For a related step, use Pruning Rate Calculator: A synapse-count reduction rate compares matched earlier and later observations. For a complementary comparison, use Brain Growth Rate Calculator: Brain-volume growth rate compares matched volumes over an established elapsed time.

References

Cortical Expansion Ratio Calculator — tool.io

Similar or alternative tools

Pruning Rate Calculator
A synapse-count reduction rate compares matched earlier and later observations.
Brain Growth Rate Calculator
Brain-volume growth rate compares matched volumes over an established elapsed time.