Diffusion Tensor Scalars Vary with Age and Across Spinal Levels in Children

Abstract

Purpose: 1) To evaluate the maturational evolution of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) of the normal pediatric cervical as well as upper thoracic cord, 2) to evaluate whether ADC and FA values vary at different levels within the spinal cord [upper cervical (UC), lower cervical (LC) and upper thoracic (UT)]. Methods:Normal pediatric MRI and diffusion tensor imaging (DTI) studies of the spinal cord obtained with a 1.5 Tesla MR scanner were retrospectively analyzed. ADC and FA maps were reconstructed from the DTI data. Regions of interest were manually placed at the center of the cervical and upper thoracic cord at the intervertebral disk levels in mid-sagittal plane. The ADC and FA values were analyzed by linear regression and a general linear model with repeated measures.Results: Forty-seven subjects ranged in age from 2 months-17.5 years (mean ± standard deviation: 74.3 ± 61.1 months) were included in the study. At all spinal cord levels a statistically significant decrease in ADC and increase in FA with increasing child's age was evident. The ADC values of the UC/LC levels were higher than those of UT while the FA values did not show significant differences.Conclusion: DTI scalars vary with age, likely due to ongoing maturational processes, and ADC values vary across levels of the spinal cord. Consequently when quantitative DTI of the spinal cord is undertaken in children; an age and levelmatched normative data should be used to accurately interpret the quantitative results.Keywords: Apparent Diffusion Coefficient (ADC), Fractional Anisotropy (FA), Diffusion Tensor Imaging (DTI) motion artifacts. These artifacts affect the thoracic cord the most at mid thoracic level, therefore the majority of the prior studies focused on cervical spine or even upper cervical spine.There are even less studies in children and hardly any normative data [5,6,11,12]. Age-specific normative data are necessary to identify and grade spinal cord pathology in developing children. Similar to the brain, many ongoing maturational processes 2 ARCHIVOS DE MEDICINA

Age related diffusion and tractography changes in typically developing pediatric cervical and thoracic spinal cord

“…In recent years, techniques like diffusion tensor imaging (DTI), a powerful quantitative tool used to measure the diffusivity of water molecules in tissue ( Mulcahey et al, 2013 ; Beaulieu, 2002 ; Maier and Mamata, 2005 ; Stiles and Jernigan, 2010 ; Hüppi and Dubois, 2006 ) as well as diffusion tensor tractography (DTT) ( Kanehiro et al, 2013 ), a visual and quantitative whiter matter fiber tracking technique, have been used to investigate these changes. These increases/decreases in tissue density have been found to strongly correlate to age-related increases/decreases in DTI and DTT metrics ( Hüppi and Dubois, 2006 ; Kanehiro et al, 2013 ; Izbudak et al, 2015 ; Singhi et al, 2012 ); fractional anisotropy (FA), apparent diffusion coefficient (MD), tract density and length of fiber tracts (average Euclidean length in mm for all streamlines within a given segment) in the brain. These findings are highly supportive of the hypothesis that age-related maturation and development continue through to adulthood.…”

Optimizing Diffusion-Tensor Imaging Acquisition for Spinal Cord Assessment: Physical Basis and Technical Adjustments

“…In addition, it is important to remember that the value of DTI parameters may also vary based on differences in sequence design (Fig 4). Further, DTI parameters can depend on the spinal cord segment evaluated and may even vary owing to age-related physiologic variations (54). Due to the limited voxel size and matrix acquisition with subsequent low spatial resolution of parametric maps, we recommend using the highest b-value image of DTI or a morphologic sequence as reference (using fusion or overlay or registration approaches).…”