Presented at the Neonatal Society 2004 Spring Meeting.
Boardman JP1, Counsell S1, Bhatia KK2, Rutherford M1, Aljabar P2, Kapellou O3, Allsop J1, Hajnal J1, Rueckert D2, Edwards AD1,3
1 Imaging Sciences Department MRC Clinical Sciences Centre, Imperial College London, UK
2 Department of Computing, Imperial College London, UK
3 Department of Paediatrics, Imperial College London, UK
Introduction: Following preterm birth both diffuse white matter disease, which is quantifiable by diffusion-weighted imaging (DWI) (1), and reduced cerebral cortical development (2) are common. However the precise phenotype of cerebral structural change and its relationship with white matter disease remain unclear.
Aim: This study aimed to investigate the neuroanatomical variation associated with preterm birth by computer-assisted morphometric analysis of magnetic resonance (MR) images.
Methods: Subjects: 62 preterm infants (median gestational age at birth 29.7 weeks) were studied at term equivalent age (median 40.4 weeks), together with 12 term born control infants (median gestational age 39.6 weeks). MR image acquisition: A 1.5 Tesla MR Eclipse system was used to acquire T1 weighted volume datasets in contiguous slices with a voxel size of 1.0 x 1.0 x 1.6 mm. DWI was acquired in 60 of these infants. Regional apparent diffusion coefficient (ADC) values in white matter and central grey matter were measured using previously described methods 1. Infants with ADC >2 SD above the mean in one or more brain region were classified as having white matter disease, and those with values < 1 SD as normal. Image Processing: for volumetric analyses non-rigid image registration was used to align all images into a standard reference space before structural information about morphometric change between groups was extracted using a deformation based morphometric approach (3). Statistical analyses were implemented using SPM99 software (http://www.fil.ion.ucl.ac.uk/spm).
Results: Preterm infants at term equivalent age showed volume reduction in the lentiform and thalamic nuclei compared to term controls (t=3.21, p=0.001). The distribution of volume reduction was similar in infants born between 24 and 30 completed weeks (n=31), and those born between 31 and 34 weeks (n=31).
When 28 infants with white matter disease were compared to 11 normal infants of similar gestational age at birth, the infants with white matter disease had a wider distribution of central grey matter volume reduction (p=0.001).
Conclusions: Deformation-based morphometry is a useful technique for quantifying structural brain changes in neonates. The anatomic signature of preterm birth includes lentiform and thalamic nuclei volume reduction which is more marked in infants with white matter disease. These data support the hypothesis that white matter disease is associated with grey matter maldevelopment.
References
1. Counsell,S.J. et al. Pediatrics 112, 1-7 (2003).
2. Ajayi-Obe,M. et al. Lancet 356, 1162-1163 (2000).
3. Rueckert,D. et al. IEEE Trans. Med. Imaging 18, 712-721 (1999)