Presented at the Neonatal Society 2010 Autumn Meeting.
Serag A1, Counsell SJ2, Aljabar P1, Ball G2, Hajnal J2, Edwards AD2, Rueckert D1, Boardman JP2,3
1 Visual Information Processing, Department of Computing, Imperial College London
2 Imaging Sciences Department, MRC Institute of Clinical Sciences, Imperial College London
3 Simpson Centre for Reproductive Health, Royal Infirmary of Edinburgh
Background: Between 24 and 44 weeks postmenstrual age (PMA), the brain undergoes significant changes in size, shape and structure, but longitudinal quantitative markers of development are limited. Changes in the magnetic resonance (MR) signal intensity (SI) may reflect maturational changes in water content (1) and changing tissue characteristics associated with pre-myelination (2). The aim of our work is to quantify signal intensity changes on a longitudinal data set of MR images acquired from premature infants.
Methods: Approval was granted by the local Research Ethics Committee. This study was carried out using 116 T1 and T2 weighted MR images from premature neonates acquired between 29-44 weeks PMA (mean PMA at birth 29+4 weeks, range 24+5 to 35+2). Infants with major focal lesions were excluded from the study. We aligned each image at specified time points within and between subjects into a common coordinate space followed by image intensity normalization, and kernel regression. The changes over time in T1 and T2 weighted signal intensity were measured in sub-cortical grey matter and white matter and displayed as a 3- dimensional change map (figure).
Results: Figure (upper panel). Map of total change (TC) in T1 weighted signal intensity over time (red represents greatest change and blue represents least change). The frontal and occipital white matter, corticospinal tracts, posterior limb of internal capsule and head of caudate show greatest change. Figure (lower panel). Maximal changes in T2 signal were present throughout white matter, in the posterior limb of the internal capsule, and in the basal ganglia and thalami. The spatio-temporal patterns of signal change were different on T1 and T2 weighted MR images: while both trajectories conform to a sigmoid distribution, T1 weighted intensities increase as a function of age, and T2 weighted intensities decrease over the same time period.
Conclusion: We have quantified spatio-temporal signal intensity changes during early development using multi-modal MR imaging and non-rigid registration. The results demonstrate maturational processes in tissue characteristics from 29 weeks onwards following preterm birth which are likely to represent pre-myelination changes and alterations in water content. The approach provides quantitative trajectories of SI change that may be useful: to provide age-specific normal values; for mechanistic studies of preterm brain injury and for studying the effects of interventions designed to improve outcome following preterm birth.
Corresponding author: j.boardman@imperial.ac.uk
References
1. Dobbing J & Sands J 1973. Quantitative growth and development of human brain. Arch Dis child vol 48, no 10, pp 757-767.
2. Yakolev PI & Lecours AR 1967. The myelogenic cycles of regional maturation of the brain. In Regional development of the brain in early life. Minowski A (editor). Blackwell, Oxford pp 3-70.