Diffusion Tensor Imaging Scalars Research Articles

Diffusion Tensor Imaging of Neurofibromatosis Bright Objects in Children with Neurofibromatosis Type 1

Neurofibromatosis bright objects (NBOs) are poorly understood. This article aimed to investigate: 1) differences in fractional anisotropy (FA) between NBOs based in gray matter (GM) and white matter (WM), and 2) the relationship between NBOs and the affected white matter tracts. Fourteen NF1 patients were included in this study. Apparent diffusion coefficient (ADC), FA, radial diffusivity (RD) and eigenvalues were used to compare NBOs and matching contralateral normal-appearing sites (NAS). Diffusion tensor imaging scalars were also compared with age-matched healthy controls. Fiber tractography was performed to assess NBO-induced changes in WM trajectories. ADC values were higher for GM and WM NBOs than for NAS and controls. FA values were lower in GM and WM NBOs compared with controls. In all regions, eigenvalues were higher in NBOs than in NAS and controls. Only three out of 18 NOBs appeared to disrupt WM tracts. ADC, λ2 and RD values of WM NBOs were higher in symptomatic compared to asymptomatic patients. Increased ADC, RD and eigenvalues and decreased FA values in NBOs can be explained by myelin and axonal damage. Increased ADC values and RD in WM NBOs correlated with the presence of symptoms. Tract integrity predominated in our study.

Hypertrophic olivary degeneration in a child following midbrain tumor resection: longitudinal diffusion tensor imaging studies

Hypertrophic olivary degeneration (HOD) is a dynamic process caused by disruptive lesions affecting components of the Guillain-Mollaret triangle (GMT). The authors applied diffusion tensor imaging (DTI) to investigate longitudinal changes of the GMT components in a child with HOD after neurosurgery for a midbrain tumor. Diffusion tensor imaging data were acquired on a 1.5-T MRI scanner using a balanced pair of diffusion gradients along 20 noncollinear directions 1 day and 3, 6, and 9 months after surgery. Measurements from regions of interest (ROIs) were sampled in the affected inferior olivary nucleus, ipsilateral red nucleus, and contralateral superior and inferior cerebellar peduncles and dentate nucleus. For each ROI, fractional anisotropy and the mean, axial, and radial diffusivities were calculated. In the affected inferior olivary nucleus, the authors found a decrease in fractional anisotropy and an increase in mean, axial, and radial diffusivities 3 months after surgery, while 3 months later fractional anisotropy increased and diffusivities decreased. For all other GMT components, changes in DTI scalars were less pronounced, and fractional anisotropy mildly decreased over time. A detailed analysis of longitudinal DTI scalars in the various GMT components may shed light on a better understanding of the dynamic complex histopathological processes occurring in pediatric HOD over time.

Maturation of the brainstem and cerebellar white matter tracts from the neonatal period to adolescence: a diffusion tensor imaging study

Aims: Diffusion tensor imaging (DTI) allows to study the normal development of white matter tracts. Several studies focused on the supratentorial white matter tracts. Almost no data are available about the temporal changes of DTI scalars for the infratentorial white matter tracts during the progressing myelination. We evaluated the quantitative changes of fractional anisotropy (FA) and mean (MD), axial (AD), and radial (RD) diffusivity within the brainstem and cerebellar white matter tracts from the neonatal period to adolescence.

State of the art in diffusion tensor imaging

In March 2011, Prof. Guy Sebag invited me to serve as a guest editor for a state-of-the-art minisymposium for Pediatric Radiology. Of course I accepted this honour with pleasure and pride, especially because I was allowed to choose a topic within paediatric neuroradiology. I decided to focus this symposium on diffusion tensor imaging (DTI), one of the MRI tools that has truly revolutionised paediatric neuroradiology in the last decade. This technique not only increases our diagnostic sensitivity and specificity in many acute and chronic paediatric neurological diseases but also helps us better understand many complex developmental disorders. Initially, diffusion-weighted imaging (DWI) was used for the early identification of ischaemic stroke, differentiation between vasogenic and cytotoxic oedema, and diagnosis of brain abscesses. However, with the development of DTI, multiple quantitative scalars (apparent diffusion coefficients, fractional anisotropy, radial and axial diffusivity) became available to characterise multiple normal and abnormal developmental processes within the brain like white matter myelination, progressive packing of white matter tracts and even migration of neurons. Most important, these objective, quantitative DTI scalars allow comparison with normative data. Consequently, disease processes may be diagnosed before they become visible on conventional T1/ T2-weighted MRI or even before symptoms become clinically apparent. Moreover, DTI also allows the demonstration of neuro-architecture in two and three dimensions. The integrity, density and course of white-matter tracts can be studied and displayed in vivo, as MR tractography. This is especially helpful to begin to separate complex developmental disorders whose seemingly endless variety and overlapping symptoms and signs have defied prior classification. In combination with other advanced MRI techniques, like perfusion-weightedMRI, MR spectroscopy, connectivity MRI, resting-state MRI and functional MRI, intact and injured functional centres within the brain can be studied in detail. Consequently, the various DTI scalars and DTI tools described in this symposium may guide and monitor treatment options. The unravelling of paediatric brain disorders is only possible when representatives of multiple scientific disciplines work together as a team. This is reflected in the group of authors that accepted my invitation and who all generously contributed in their respective fields. Susumu Mori and his team of MR physicists share their expertise in the quantitative evaluation of the normal brain development. Petra Hueppi and her team of developmental neuroscientists discuss the value of DTI in comparison with its competitors to better understand how the brain grows and progressively masters complex cognitive functions. Andrea Poretti, Charles Raybaud and I, a team of paediatric neuroradiologists and paediatric neurologists, present the significance of DTI in the evaluation and characterisation of complex brain malformations. Finally, neuroradiologists Jim Barkovich and Pratik Mukherjee, with physicist Duan Xu, discuss whether DTI scalars can predict functional outcome in paediatric brain injury. I hope you will share my excitement and enjoy reading these updates on DTI in paediatric neuroradiology. It was a pleasure and honour to work with these expert authors and I would like to thank them once again for sharing their knowledge and expertise with us. Without their effort and commitment this would not have been possible. Thank you, merci bien, grazie, arigatou gozaimashita, xie xie nin. Pediatr Radiol (2013) 43:14 DOI 10.1007/s00247-012-2518-8