Our method provides an alternative to manual labeling for creating training sets for statistical models of phenotypes. Such an approach can accelerate research with large observational healthcare datasets and may also be used to create local phenotype models.
We have demonstrated that the crowd can address the challenges of scalable ontology verification, completing not only intuitive, common-sense tasks, but also expert-level, knowledge-intensive tasks.
The desire to monitor the spatial-temporal characteristics of myelination in the spinal cord (SC), in the context of pathological change in demyelinating diseases or proposed neuroregenerative protocols, has led to an interest in noninvasive imagebased myelin measurement methods. We present one strategy: a magnetic resonance-based measure that capitalizes on the characteristics of T 2 relaxation of water compartmentalized within tissue. In this study, 32-echo relaxation studies for measuring the myelin water fraction (MWF) were applied in healthy control SC in vivo using a sagittal inversion recovery multiecho sequence, and findings were supported with supplemental studies in bovine SC samples in vitro. Mean human MWF varied according the level of the SC examined: cervical, thoracic, and lumbar MWF was found to be 21. The human spinal cord (SC) is a 0.5-m long cylindrical structure in the central nervous system (CNS) that occupies the upper two thirds of the vertebral canal, and serves as a liaison for impulses between the brain and the peripheral nerves. Transverse axial sections through the SC reveal a characteristic central "butterfly" distribution of gray matter (GM) within the surrounding white matter (WM) as depicted in Figure 1; the distinction between the two depends on the presence of myelin, a lipoprotein membrane that ensheathes axons and gives rise to the glistening white appearance of WM. Myelin's primary role of potentiating action potential propagation is well known; its importance in that respect is exemplified by the devastating pathologies of demyelinating diseases such as multiple sclerosis (MS).The motivation to explore a magnetic resonance marker of myelination in the SC is two-fold. The SC is often involved in the demyelinating pathology of MS and SC. Magnetic resonance imaging (MRI) has recently been recommended as a paraclinical test for MS (1,2). Meanwhile, demyelination has been suggested as a potential strategy toward creating a permissive extracellular environment for axonal regeneration after SC injury (3). In both cases, magnetic resonance markers of myelination in the SC are of interest in monitoring disease pathology and potential regenerative therapies. Myelin and T 2 RelaxationIndirect measurement of myelin is possible with MRI. T 2 relaxation aspires to resolve multiexponential T 2 decay data into its constituent exponential components, each of which is attributable to water protons within a distinct diffusion restricted relaxation environment in tissue. The T 2 component with the shortest relaxation time (ϳ20 ms) is believed to originate from water trapped within the bilayers of the myelin sheath (4,5); this "short" relaxation time is believed to arise due to the large interfacial contact area in the multilamellar myelin compartment. The fractional contribution of the signal from this short T 2 component relative to the total area under the T 2 distribution is called the myelin water fraction (MWF) (5). Magnetic resonance studies have amassed substantial evidence that the shor...
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