Journal of neuroimaging : official journal of the American Society of Neuroimaging
-
Geometric distortions resulting from large pose changes reduce the accuracy of motion measurements and interfere with the ability to generate artifact-free information. Our goal is to develop an algorithm and pulse sequence to enable motion-compensated, geometric distortion compensated diffusion-weighted MRI, and to evaluate its efficacy in correcting for the field inhomogeneity and position changes, induced by large and frequent head motions. ⋯ Dual-echo acquisitions with blip-reversed phase encoding can be used to generate slice-level distortion-free images, which is critical for motion-robust slice to volume registration. The distortion corrected images not only result in better motion estimates, but they also enable a more accurate final diffusion image reconstruction.
-
Cerebral blood flow (CBF) has been reported to increase after shunt surgery in patients with idiopathic normal pressure hydrocephalus (iNPH). The aims of this study were to investigate if CBF, measured using the noninvasive perfusion MRI method arterial spin labeling (ASL), increased after shunt surgery, if postoperative change in CBF correlated with improvement in symptoms, and if baseline CBF data correlated with postoperative outcome. ⋯ The clinical value of ASL in the work-up of patients with iNPH is uncertain. In this study, ASL could not predict outcome after shunt surgery and there were no correlations between change in CBF and change in clinical symptoms after shunt surgery.
-
Posterior fossa syndrome (PFS), characterized by loss of language and other neurological impairments within the immediate postoperative period, occurs in approximately 25% of children who undergo surgical resection of posterior fossa tumors. Diffusion tensor imaging connectomics offer promise for elucidation of pathway-level disruption in neural connectivity of patients with this disorder. We aim to determine differences in pre- and postoperative connectomics between children with PFS and children with mild or no language deficit after surgery. ⋯ Our findings revealed significant differences in preoperative neural connectivity involving the corticothalamic and other pathways among children who did, versus who did not, develop PFS postoperatively. Diffusion tensor imaging connectomics offers a unique opportunity to study the effect of the posterior fossa tumors on cerebello-cerebral networks and provide new insights into the mechanism of the structural plasticity/reorganization after surgery.
-
Microembolic signals (MES) are detectable by transcranial Doppler monitoring and associated with increased risk of first or recurrent ischemic stroke. MES detection can also illuminate stroke etiology and the effect of prophylactic treatment. MES detection cannot accurately distinguish between stroke-related microemboli and ultrasound contrast agents. These agents contain microbubbles and are frequently used in neuro- and cardiovascular diagnostics. We aimed to assess how long after contrast infusion microbubbles are detectable by transcranial Doppler monitoring. ⋯ None of the subjects had detectable MES for more than 77 minutes after ultrasound contrast infusion. MES detection with the intent to detect stroke-related microemboli should wait for at least this long after completed infusion.