TOP VIEW · SCHEMATIC
01 / HC
Head circumference
A closed scalp perimeter passing anteriorly over the glabella and posteriorly over the maximal occipital prominence.
THE TRIPLE-MEASURE MODEL
Estimate endocranial volume.
Three scalp measurements. A fixed model. A clearer view of your data.
Enter measurements
Trace the scalp surface using the study protocol.
TRIPLE-MEASURE ESTIMATETM MODEL
—cm³
Estimated endocranial volume
Combined measurement— cm
HC —+SA —+CA —
ICV = 21.322 × (HC + SA + CA) − 992.36
Compare the models
Same measurements, two estimates Head circumference only— cm³47.61 × HC − 1271.91
TM − HC difference— cm³Model estimates may differ
TM signed error—
HC signed error—
Signed error = estimated volume − CT reference volumeAdd to your study
Save measurements with a de-identified case code.
A research estimate of the cranial cavity. This is not a brain tissue measurement or a diagnosis. The supplied study validates adults; this workspace does not apply paediatric growth centiles.
YOUR ADULT CT COHORT
Study records.
Keep de-identified measurements together, ready for analysis.
Recorded cases0Target cohort: 100 adults
CT reference available0Included in model validation
Observer pairs0Cases with repeat observations
Study progress0%
| Case code | Age / sex | HC cm | SA cm | CA cm | TM estimate cm³ | CT reference cm³ | Actions |
|---|
Your study starts here
Add your first adult case, or import measurements from a CSV file.
Enter measurements0 casesSaved in this browser only · export regularly
Use study codes only. Browser storage is not an institutional archive and does not synchronise across devices. Store exported study files in your approved research location.
FIXED EQUATIONS · NO REFITTING
Model validation.
Compare both estimates with the same segmented CT reference volumes.
Synthetic demonstration data. These 24 illustrative cases are not study findings and are never added to your records.
Ready when your reference data is
Save at least two cases with CT reference volumes to see agreement plots.
You can explore a clearly labelled synthetic example now.
Paired CT cases—Your study records
Triple-Measure MAE cm³—Mean absolute prediction error
Triple-Measure RMSE cm³—Root mean squared error
Triple-Measure bias cm³—Mean predicted − reference
Predicted vs reference
Points closer to the diagonal show closer estimates.
Triple-Measure Perfect agreement
Bland–Altman agreement
Predicted − reference, against their mean.
Mean bias 95% limits of agreement
Prediction accuracy & agreement
All values in cm³. Each model uses the same complete cases.
| Model | N | MAE | RMSE | Mean bias | Lower LoA | Upper LoA |
|---|
Limits of agreement = mean bias ± 1.96 × sample SD of differences. These are not confidence intervals. Results are descriptive; no significance tests or clinical cut-offs are applied.
REPEATED MEASUREMENTS
Observer reliability.
Compare the primary reading with a repeat reading and an independent observer.
Record repeat observations
All arc values in cm; CT volumes in cm³.
Absolute agreement
ICC(A,1) · two-way mixed · single measurement
| Measurement | Intra n / ICC | Inter n / ICC |
|---|
Point estimates only. Export the observations to calculate 95% confidence intervals in your statistical software.
The proposal plans 20 repeated adult CT cases and a minimum two-week repeat interval. ICC is undefined with fewer than two complete pairs or no measurable variation.
MEASUREMENT & INTERPRETATION
The protocol behind the numbers.
Based on the supplied October 2026 USM adult CT validation proposal.
01—03
Measure curves, not straight-line distances
Align the reconstruction to the Frankfort horizontal plane. Trace each curve along the scalp surface using consistent anatomical landmarks. Enter all three lengths in the same unit; the calculator converts millimetres to centimetres before applying the equations.
SIDE VIEW · SCHEMATIC
02 / SA
Sagittal arc
A midsagittal scalp curve over the vertex between the anterior and posterior intersections with the circumference line.
FRONT VIEW · SCHEMATIC
03 / CA
Coronal arc
A transverse scalp curve over the vertex between homologous temporozygomatic landmarks above each ear, as defined by the study.
Fixed regression equations
Triple-Measure modelTM = HC + SA + CAICV = 21.322 × TM − 992.36
Head circumference modelICV = 47.61 × HC − 1271.91
Lengths are in centimetres. Estimated endocranial volume (ICV) is in cm³, numerically equivalent to mL. Coefficients are reproduced from section 3.6 of the supplied proposal and are never refitted to your entered cases.
CT reference
Use the segmented internal cranial cavity bounded by the inner skull surface, sealed inferiorly at the protocol’s basion–opisthion plane. CT segmentation is performed outside this application.
Study scope & interpretation
- Adult validation cohort: age 18 years or older; target N = 100 independent cases.
- Endocranial volume includes the cranial cavity contents. It is not equivalent to brain parenchymal volume.
- No normal/abnormal classification, age or sex correction, paediatric centiles, or brain tissue conversion is applied.
- Agreement plots use estimated minus reference volume. Positive bias indicates overestimation.
- Reliability uses ICC(A,1) with paired readings. Negative ICC values are retained; confidence intervals are not calculated here.
- Measurements and exports are stored on your device. No patient identifiers or DICOM files should be entered.
Source & research team
Muhammad Dany Zhafran bin Md Daud · Research proposal, October 2026.
Supervisor: Dr. Johari bin Abdullah · Co-supervisor: Dr. Cicero Moraes.
School of Dental Sciences, Health Campus, Universiti Sains Malaysia.
Moraes C, Abdullah JY, et al. A Triple-Measure Model for Estimating Cranial–Brain Size Across Age Groups. bioRxiv preprint (2026). View source paper ↗
This application implements the supplied proposal. It does not establish clinical validity or replace the study’s independent validation.