Showing papers on "Neural tract published in 2006"

3D histological reconstruction of fiber tracts and direct comparison with diffusion tensor MRI tractography

Abstract: A classical neural tract tracer, WGA-HRP, was injected at multiple sites within the brain of a macaque monkey. Histological sections of the labeled fiber tracts were reconstructed in 3D, and the fibers were segmented and registered with the anatomical post-mortem MRI from the same animal. Fiber tracing along the same pathways was performed on the DTI data using a classical diffusion tracing technique. The fibers derived from the DTI were compared with those segmented from the histology in order to evaluate the performance of DTI fiber tracing. While there was generally good agreement between the two methods, our results reveal certain limitations of DTI tractography, particularly at regions of fiber tract crossing or bifurcation.

The effect of paramagnetic manganese cations on 1H MR spectroscopy of the brain

Abstract: Introduction The paramagnetic properties of divalent manganese cations (Mn) and their in vivo resemblance to calcium cations (Ca) has led to their use in morphological [1] and neural pathway [2] imaging. Mn is taken up through Ca-channels during neural activity and subsequently transported anterograde along microtubules at a velocity equivalent to fast axonal transport thereby making the metal suitable for neural tract tracing [2]. Mn is an essential trace element found at low concentrations in the brain. Elevated levels of Mn are neurotoxic and influence a range of neurophysiologic and metabolic processes and chronic exposure to Mn may lead to neurodegeneration [3]. The administration of Mn to observe, for example, neural pathways may therefore influence those same pathways due to the high local concentrations of Mn required to provide MRI contrast. As a result, the use of H MRS to obtain a metabolic profile of the brain may be influenced by both Mn-induced metabolic changes and the effect of the paramagnetic metal ion on the relaxation of the metabolites themselves if the Mn cations and metabolites are in the same cellular compartment. Consequently, this study has investigated the effect of Mn on H MR spectroscopy using an in vivo Mn-enhanced optic tract imaging model [2] together with phantom experiments.