Application of hidden Markov random field approach for quantification of perfusion/diffusion mismatch in acute ischemic stroke.

The perfusion/diffusion 'mismatch model' in acute ischemic stroke provides the potential to more accurately understand the consequences of thrombolytic therapy on an individual patient basis. Few methods exist to quantify mismatch extent (ischemic penumbra) and none have shown a robust ability to predict infarcted tissue outcome. Hidden Markov random field (HMRF) approaches have been used successfully in many other applications. The aim of the study was to develop a method for rapid and reliable identification and quantification of perfusion/diffusion mismatch using an HMRF approach. An HMRF model was used in combination with automated contralateral identification to segment normal tissue from non-infarcted tissue with perfusion abnormality. The infarct was used as a seed point to initialize segmentation, along with the contralateral mirror tissue. The two seeds were then allowed to compete for ownership of all unclassified tissue. In addition, a novel method was presented for quantifying tissue salvageability by weighting the volume with the degree of hypoperfusion, allowing the penumbra voxels to contribute unequal potential damage estimates. Simulated and in vivo datasets were processed and compared with results from a conventional thresholding approach. Both simulated and in vivo experiments demonstrated a dramatic improvement in accuracy with the proposed technique. For the simulated dataset, the mean absolute error decreased from 171.9% with conventional thresholding to 2.9% for the delay-weighted HMRF approach. For the in vivo dataset, the mean absolute error decreased from 564.6% for thresholding to 34.2% for the delay-weighted HMRF approach. The described method represents a significant improvement over thresholding techniques.

Faith-placed cardiovascular health promotion: a framework for contextual and organizational factors underlying program success.

The objective of this study was to assess the literature on faith-placed cardiovascular health promotion in order to construct a framework of factors meant to facilitate effective program design. Data source was empirical studies on the contextual and organizational factors underlying faith-placed cardiovascular program performance. Study inclusion criteria were papers reported from 1984 to 2003 that include contextual and organizational variables. Success factors identified in the literature fall under the following clusters: faith support, secular support, partnership (and obstacles to it), faith organization capabilities, secular organization capabilities and caring intervention. Each cluster consists of several factors, whose relative weights cannot be ascertained from the present state of the literature. These clusters of factors can be interrelated through a simple framework that is useful in program design.

Assessment and management of neutralizing antibodies in patients with multiple sclerosis.

The development of neutralizing antibodies (NAbs) to interferon beta (IFNbeta) products during treatment of MS poses a challenge for clinicians. Given the impact of NAbs on the clinical efficacy of IFNbetas, the immunogenicity of different IFNbeta products should be one of the factors that neurologists consider in the treatment of patients with MS. However, no clear guidelines are available for the practicing neurologist concerning which patients should be tested for NAbs and how to clinically manage patients who develop NAbs. This article summarizes the content of this supplement, discusses issues related to measuring NAbs in clinical practice, and gives practical alternatives for managing MS in patients who develop NAbs during IFNbeta therapy.