MRI findings in nonalcoholic steatohepatitis: correlation with histopathology and clinical staging

Purpose

To evaluate magnetic resonance imaging (MRI) findings of nonalcoholic steatohepatitis (NASH) and to determine the correlation of MRI findings with histopathology and Mayo End-Stage Liver Disease (MELD) score.

Materials and Methods

Thirty patients (18 males, 12 females; mean age: 57±8.9 years; age range: 35–71 years) with histopathologically proven NASH who underwent MRI examinations between January 2001 and October 2005 were included in the study. Two radiologists retrospectively reviewed all magnetic resonance (MR) examinations in consensus to evaluate the presence and extent of predetermined findings of NASH including liver steatosis, early patchy liver enhancement indicating inflammation and liver fibrosis. The findings detected on MRI were correlated and compared to histopathological findings and MELD score by using nonparametric Spearman correlation coefficient and Kruskal–Wallis analysis of variance.

Results

Liver steatosis was observed in 10 of 30 patients; early patchy liver enhancement, in 8 of 30 patients and liver fibrosis in 19 of 30 patients on MR images. Liver fibrosis was reticular in all these patients. There were statistically significant moderate correlations between MRI findings of liver steatosis and histopathologic grades of steatosis (r=0.43; P<.05), and between MRI findings of fibrosis and histopathologic stages of fibrosis (r=0.61; P<.001). Early patchy enhancement did not demonstrate statistically significant correlation with inflammation (P=.28). There was no statistically significant overall correlation between MRI findings of NASH and MELD score.

Conclusion

MRI findings of liver steatosis and fibrosis in NASH showed moderate correlations with histopathologic grades of steatosis and stages of fibrosis, but MRI findings of NASH did not demonstrate any significant correlations with MELD score.     

Specific and nonspecific collapse in protein folding funnels

Experiments with fast folding proteins are beginning to address the relationship between collapse and folding. We investigate how different scenarios for folding can arise depending on whether the folding and collapse transitions are concurrent or whether a nonspecific collapse precedes folding. Many earlier studies have focused on the limit in which collapse is fast compared to the folding time; in this work we focus on the opposite limit where, at the folding temperature, collapse and folding occur simultaneously. Real proteins exist in both of these limits. The folding mechanism varies substantially in these two regimes. In the regime of concurrent folding and collapse, nonspecific collapse now occurs at a temperature below the folding temperature (but slightly above the glass transition temperature).     

Topological invariants in the study of a chaotic food chain system

The study of ecological systems has generated deep interest in exploring the complexity of chaotic food chains. The role of chaos in ecosystems is not entirely understood. One approach to have a better comprehension of ecological chaos is by analyzing it in mathematical models of basic food chains. In this article it is considered a classical chaotic food chain model from the literature. We use the theory of symbolic dynamics to study the topological entropy and the parameter space ordering of kneading sequences associated with one-dimensional maps that reproduce significant aspects of the model dynamics. The topological entropy allows us to distinguish different chaotic states in some realistic system parameter region. Another numerical invariant is introduced in order to characterize isentropic dynamics. Studying a set of maps with the same topological entropy, we exhibit numerical results about the relation between the second topological invariant and each of the control parameters in consideration. This work provides an illustration of how our understanding of ecological models can be enhanced by the theory of symbolic dynamics.     

The extended loop group: An infinite dimensional manifold associated with the loop space

A set of coordinates in the non-parametric loop-space is introduced. We show that these coordinates transform under infinite dimensional linear representations of the diffeomorphism group. An extension of the group of loops in terms of these objects is proposed. The enlarged group behaves locally as an infinite dimensional Lie group. Ordinary loops form a subgroup of this group. The algebraic properties of this new mathematical structure are analyzed in detail. Applications of the formalism to field theory, quantum gravity and knot theory are considered.     

Ultraviolet properties of maximal supergravity

We argue that recent results in string perturbation theory indicate that the four-graviton amplitude of four-dimensional N=8 supergravity might be ultraviolet finite up to eight loops. We similarly argue that the h-loop M-graviton amplitude might be finite for h<7+M/2.     

Single-shot extreme ultraviolet laser imaging of nanostructures with wavelength resolution

We have demonstrated near-wavelength resolution microscopy in the extreme ultraviolet. Images of 50 nm diameter nanotubes were obtained with a single ~1 ns duration pulse from a desktop-size 46.9 nm laser. We measured the modulation transfer function of the microscope for three different numerical aperture zone plate objectives, demonstrating that 54 nm half-period structures can be resolved. The combination of near-wavelength spatial resolution and high temporal resolution opens myriad opportunities in imaging, such as the ability to directly investigate dynamics of nanoscale structures.     

Active cancellation of occlusion: an electronic vent for hearing aids and hearing protectors

The occlusion effect is commonly described as an unnatural and mostly annoying quality of the voice of a person wearing hearing aids or hearing protectors. As a result, it is often reported by hearing aid users as a deterrent to wearing hearing aids. This paper presents an investigation into active occlusion cancellation. Measured transducer responses combined with models of an active feedback scheme are first examined in order to predict the effectiveness of occlusion reduction. The simulations predict 18 dB of occlusion reduction in completely blocked ear canals. Simulations incorporating a 1 mm vent (providing passive occlusion reduction) predict a combined active and passive occlusion reduction of 20 dB. A prototype occlusion canceling system was constructed. Averaged across 12 listeners with normal hearing, it provided 15 dB of occlusion reduction. Ten of the subjects reported a more natural own voice quality and an appreciable increase in comfort with the cancellation active, and 11 out of the 12 preferred the active system over the passive system.