Non-invasive estimation of brain-volume in infants.

Background: Neurological development is determined by brain growth. Methods to measure total brain volume (TBV) in clinical settings are limited. MR-imaging represents the gold-standard.

Aims: The present study tests the hypotheses that in infants without any brain pathology, TBV - as determined by MRI - can be accurately estimated by cranial volume (CrV), measured by 3D-laser scanning. In case of good correlation of CrV with TBV it was further tested, whether CrV can be also estimated by (I) head circumference (HC) or (II) by other technology than laser scanning.

Study Design & Subjects: To test the hypothesis, that TBV can be reliably estimated by CrV-measurement, data from routine MRI and 3D-laser-scanner measurements were analyzed in infants if no major structural brain anomaly was found in MR-imaging. To test whether CrV can be predicted by HC-measurements during infancy, data from routine follow-up visits were used from preterms born in a two year period. Preterms are invited for a routine follow-up visit (which includes laser scanning of the head) at an age of 3 months and, for further follow-ups at 6, 9 or 12 months. To compare accuracy of CrV measurement by other techniques, a puppet head was measured, using different 3D-measurement principles: (i) Structured light projection system, (ii) The non-invasive laser-shape-digitizer, and (iii) Structure-from-motion (SFM) technique.

Outcome Measures: TBV was compared with CrV using a Passing-Bablok-Regression. To determine how well HC predicts CrV, the coefficient of determinant (R) was calculated for each age group.

Results: CrV and TBV of 25 infants (median age 19 month, body weight of 11 kg) showed a median bias of -86.7 mm with a slightly smaller TBV (median of 1034.1 mm, IQR 875.9 … 1179.8 mm) than CrV (median 1092.2, IQR 950.5 … 1258.4 mm). CrV was poorly estimated by HC, with R between 0.79 and 0.87 at 3 and 9 month of age respectively. For the non-invasive laser-shape-digitizer and the SFM-technique the accuracy was good (radial coordinate differences ±0.3 vs. ±0.5 mm).

Conclusion: The present study provides convincing evidence that CrV can be used to estimate TBV in routine care, whereas HC is a poor predictor of individual CrV.