Christian Mitter MD, Presenter: Nothing to Disclose

Peter Christian Brugger MD, PhD, Abstract Co-Author: Nothing to Disclose

Daniela Prayer MD, Abstract Co-Author: Nothing to Disclose

Gregor Kasprian MD, Abstract Co-Author: Nothing to Disclose

Association fibers connect different cortical areas in the same hemisphere and constitute an important anatomical substrate for a diverse range of higher cognitive functions. They already have been extensively investigated in vivo in adults and children as well as postmortem in human fetal brains. In the present study fetal MRI and DTI-based tractography was used to visualize major association fiber tracts (uncinate fasciculus - UF, inferior fronto-occipital fasciculus - IFOF, inferior longitudinal fasciculus - ILF and cingulum) and the fornix in the living fetal brain in utero.

24 non-motion degraded DTI examinations of living unsedated fetuses (20–34 gestational weeks - GW) without gross cerebral abnormalities were included in the study. Orthogonal axial DTI sequences (16 directions, reconstructed voxel size 0.94/0.94/3mm, b values of 0 and 700 sec/mm2) were performed using a 1.5T MR unit. Association fiber tracts were anatomically defined using a multiple ROI approach and calculated using a deterministic linear tracking algorithm.

In utero tractography of UF and IFOF was possible as early as 20 GW. UF was found in 24/24 (100%) subjects and IFOF in 21/24 (87,5%) subjects. Visualization of the ILF was possible in only 6/24 (25,0%) subjects, most of them aged 30 GW or older. Tractography of cingulum and fornix was successful from 27 GW on in 9/24 (37,5%) and 8/24 (33,3%) of subjects respectively. Statistically significant differences in mean FA-value were found between left and right IFOF and between UF and IFOF of the right hemisphere.

Provided optimal imaging conditions DTI-based tractography can be used to visualize the morphological appearance of major association fiber tracts in the developing fetal brain in utero. Identifiable fiber tracts include the UF and the IFOF as early as 20 GW, and the ILF, the cingulum and the fornix in older fetuses. Quantitative analysis of diffusion parameters provides preliminary evidence for hemispheric asymmetry and structural differences between association fiber tracts.

The possibility to non-invasively investigate association fiber tracts in utero with DTI-based tractography may be useful for a more precise evaluation of intrauterine white matter damage.

Mitter, C, Brugger, P, Prayer, D, Kasprian, G, DTI-based in Utero Tractography of Association Fiber Tracts in the Developing Fetal Brain.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14019289.html