Biomedical subjects
D B Hackney
Publications and source records attributed to D B Hackney.
A method for in vivo high resolution MRI of rat spinal cord injury.
We have developed an implanted radiofrequency coil to obtain high resolution in vivo MR images at 1.9 Tesla of rat spinal cords that have been injured using a standardized weight drop technique. The signal-to-noise ratio and motion artifact suppression of these images is superior to that achieved in earlier attempts at this field strength using an external surface coil. The high quality and spatial resolution provided by this technique afford the possibility for longitudinal studies of experimental spinal cord injury before and after treatment, as well as detailed correlation of in vivo MRI contrast, histopathological findings, and functional deficit, in a controlled setting.
MRI characterization of diffusion coefficients in a rat spinal cord injury model.
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.
Postmortem magnetic resonance imaging of experimental spinal cord injury: magnetic resonance findings versus in vivo functional deficit.
The relationship between the severity of the posttraumatic functional deficit and findings on magnetic resonance imaging (MRI) was investigated in a rat model of experimental spinal cord trauma. Thirty Sprague-Dawley rats were subjected to an identical, moderate, contusion injury of the spinal cord. Control animals underwent laminectomy without cord injury. The severity of the functional deficit was assessed with the Combined Behavioral Score (CBS). Animals were killed at 3, 7, 14, 21, or 28 days after injury, and the fixed, excised spinal cords were studied with MRI at 1.9 T. The lesion length was measured on sagittal spin-echo MRI. The lesion length measured on MRI was highly correlated with the CBS functional score (r = 0.56, P = 0.002). There were significant correlations between lesion length as determined by MRI and by histological morphometry (r = 0.44, P = 0.02), between histological morphometric lesion length and CBS functional deficit (r = 0.76, P < 0.001), and between the area of residual white matter at the lesion epicenter, determined by histological techniques, and the severity of functional deficit (r = -0.59, P = 0.001). A qualitative estimate of the area of preserved white matter, derived from MRI, was significantly correlated with the severity of functional deficit (r = -0.56, P = 0.006). A multiple regression of MRI-determined lesion length and MRI estimate of residual white matter versus CBS explained more than 42% of the variability of the functional deficit among these animals subjected to the same weight drop injury. We conclude that MRI parameters are reliable predictors of the severity of neurological deficit in experimental spinal cord trauma.
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Experimental spinal cord injury: imaging the acute lesion.
In order to obtain high resolution images of fixed excised rat spinal cords we have developed a technique using a 6-mm bore, two-turn saddle coil, with a usable imaging length of approximately 4 cm. MR imaging is performed on a prototype 31-cm bore, 1.9-T system with a 1.5-mm section thickness and 7.6-mm field of view.
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Fast spin-echo imaging of the brain and spine.
The recent advent and implementation of rapid spin-echo techniques has allowed increased imaging speed while maintaining spin-echo-like contrast. This review explains the basis of fast spin-echo imaging and attempts to elucidate the etiology of the differences between it and spin-echo imaging. Clinical applications and limitations of fast spin-echo imaging in the brain and spine will also be addressed.