MRI characterization of diffusion coefficients in a rat spinal cord injury model

Abstract

Apparent diffusion coefficients (ADC) were measured in a rat spinal cord weight-drop injury model. After sacrifice, the spinal cords were fixed in situ and excised for MR imaging and ADC measurement. Diffusion is anisotropic in normal gray and white matter. There were significant decreases in ADCs measured along the longitudinal axis of the injured cord and increases in ADCs measured transverse to the cord. Injured segments demonstrated reductions in diffusion anisotropy in the white matter. Diffusion was completely isotropic at the epicenter of the weight-drop injury. Significant decreases in longitudinal ADC and increases in transverse ADC were observed in portions of the cord which appeared normal on conventional spin-echo and calculated T2 images. Thus ADC measurement may complement routine imaging for evaluation of spinal cord injury.

An image‐based finite difference model for simulating restricted diffusion

“…[3], Eq. [9] is a function of the concentrations at time step nϩ1 and, there- fore, cannot be solved explicitly. Solving the system of equations, constructed by applying Eq.…”

“…Solving the system of equations, constructed by applying Eq. [9] at every node, is more time-consuming than computing the FTCS expression for every node. Although the lack of a stability constraint allows for much larger time steps, the decreased computation time is at the expense of reduced accuracy.…”

“…[3]) to all nodes for which iϩn is even, the updated concentrations at the even nodes are then substituted into Eq. [9] to compute the new concentrations at the odd nodes. For the subsequent time step, the odd nodes are updated first using the FTCS scheme and then computations at the even nodes are carried out with Eq.…”

“…For the subsequent time step, the odd nodes are updated first using the FTCS scheme and then computations at the even nodes are carried out with Eq. [9]. In multiple dimensions, nodes are defined as odd or even according to the value of iϩjϩkϩn, where i, j, and k are the indices along the x, y, z axes.…”

Diffusion Tensor Imaging of the Normal Pediatric Spinal Cord Using an Inner Field of View Echo-Planar Imaging Sequence

“…While studies on diffusion imaging of the spinal cord in adults, 7,20,21 as well as in animal models [22][23][24][25] have been reported, a comprehensive study of the pediatric spinal cord that examines the accuracy and reproducibility of DTI measures has not yet been reported. The investigation of normative data of spinal cord DTI represents an additional important area of inquiry.…”