Presented at the Neonatal Society 2014 Autumn Meeting.
Lingam I1,2, Kapetanakis A2, Tusor N1, Wurie J1, Nongena P3, Allsop JM1, Edwards AD1,2, Tournier JD1, Counsell SJ1
1 Centre for the Developing Brain, Division of Imaging Sciences & Biomedical Engineering, King’s College London, UK
2 NICU, St Thomas’ Hospital, King’s College London, UK,
3 Department of Paediatrics, Imperial College London, UK
Background: Magnetic resonance (MR) tractography allows visualisation of white matter tracts by assessing the directional dependence of water molecular diffusion in tissue (anisotropy). Constrained Spherical Deconvolution (CSD) is an approach that better resolves crossing fibres compared to tensor based methods. This project assessed the feasibility of performing CSD of the middle cerebral peduncle (MCP) and corticospinal tract (CST) in the neonatal brain. Results were compared to diffusion tensor based fibre tracking methods used in this population.
Methods: Ethical Committee permission for this study was granted and parental consent obtained prior to imaging. High angular resolution diffusion images (HARDI) were acquired with a 3 Tesla MR scanner (64 directions, b = 2500 s/mm3). Using the MRtrix software package1, CSD and Diffusion Tensor Tracking (DTT) of the MCP and CSTs were performed and compared qualitatively and quantitatively. Secondary analysis included determining the impact of selected perinatal clinical factors on mean fractional anisotropy (FA) values. This study was funded by a Strategic Grant from the MRC.
Results: Clinical data and images were available for 44 infants, comprising of 41 preterm and 3 term infants. Image acquisition times were approximately 10 minutes. The CSD approach generated significantly more detailed images of the MCP and CSTs. The images of the MCP generated by CSD demonstrated wide fibre bundles spreading across the cerebellar hemispheres. The CST fibres could be seen fanning out across the motor cortex, in contrast to the DTT images that only demonstrated fibres travelling vertically. The mean FA generated by CSD was significantly lower than DTT (p<0.0001). Both methods of tractography demonstrated a significant increase in mean FA with post-menstrual age, correcting for gestational age and birth weight (p<0.005). In the subgroup of infants born at 33 weeks gestational age and below, this association was significant in the CSD approach (p<0.001), but not the DTT method (p=0.10).
Conclusion: CSD has the ability to resolve complex, crossing fibres and provides a richer depiction of neuronal tracks compared to deterministic methods in preterm and term infants. CSD is a more sensitive method of tractography with potential to assess the developing brain in unprecedented detail.
Corresponding author: Ingran@gmail.com
1. http://www.brain.org.au/software/ (JD Tournier)