Magma (New York, N.Y.)
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Magma (New York, N.Y.) · Feb 2012
Residual tumor after laser ablation of human non-small-cell lung cancer demonstrated by ex vivo staining: correlation with invasive temperature measurements.
Histology is the gold standard for confirming thermally induced necrosis. Generally, however, no specimen is obtained from thermal ablation therapy for pathological examination. The aim of this study was to provide evidence for the relationship between temperatures reached and resulting tissue coagulation during laser ablation in a near-physiological ex vivo lung tumor model by combining viability staining and direct temperature measurement. ⋯ We found that coagulation size correlated positively with temperature. There was a clear trend towards the correlation of time over 44°C and ablation depth. Maximum temperatures did not significantly correlate with coagulation size. Laser ablation of lung tumors using the IHLP (isolated human lung perfusion) model represents a possible method for evaluating ex vivo the interrelationships of temperature, time of temperature exposure, and resulting coagulation.
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Magma (New York, N.Y.) · Feb 2012
Comprehensive analysis of the Cramer-Rao bounds for magnetic resonance temperature change measurement in fat-water voxels using multi-echo imaging.
The aim of this paper is to characterize the noise propagation for MRI temperature change measurement with emphasis on finding the best echo time combinations that yield the lowest temperature noise. ⋯ The results present a comprehensive analysis of the effects of different scan parameters on temperature noise, potentially benefiting the selection of scan parameters for clinical MRI thermometry.
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Magma (New York, N.Y.) · Jun 2011
An improved PSF mapping method for EPI distortion correction in human brain at ultra high field (7T).
To further improve the quality and robustness of the point-spread function (PSF) mapping method for fully automatic and accurate correction of geometric distortions in EPI at ultra high field such as 7 Tesla with high fidelity. ⋯ More precise mapping and correction of pixel shifts and blurring is accomplished with the proposed improvements. Errors in the shift map that are caused by PSF-ghost artifacts in the multi-shot PSF acquisition, e.g., from small motion during the reference scan, do not affect the improved shift estimation method.
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Magma (New York, N.Y.) · Dec 2010
ReviewGraph theoretical analysis of structural and functional connectivity MRI in normal and pathological brain networks.
Graph theoretical analysis of structural and functional connectivity MRI data (ie. diffusion tractography or cortical volume correlation and resting-state or task-related (effective) fMRI, respectively) has provided new measures of human brain organization in vivo. The most striking discovery is that the whole-brain network exhibits "small-world" properties shared with many other complex systems (social, technological, information, biological). This topology allows a high efficiency at different spatial and temporal scale with a very low wiring and energy cost. ⋯ Indeed, such topological definition provides a reliable framework for predicting behavioral consequences of focal or multifocal lesions such as stroke, tumors or multiple sclerosis. It also brings new insights into a better understanding of pathophysiology of many neurological or psychiatric diseases affecting specific local or global brain networks such as epilepsy, Alzheimer's disease or schizophrenia. Graph theoretical analysis of connectivity MRI data provides an outstanding framework to merge anatomical and functional data in order to better understand brain pathologies.
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Magma (New York, N.Y.) · Dec 2010
ReviewResting developments: a review of fMRI post-processing methodologies for spontaneous brain activity.
Analytic tools for addressing spontaneous brain activity, as acquired with fMRI during the "resting-state," have grown dramatically over the past decade. Along with each new technique, novel hypotheses about the functional organization of the brain are also available to researchers. We review six prominent categories of resting-state fMRI data analysis: seed-based functional connectivity, independent component analysis, clustering, pattern classification, graph theory, and two "local" methods. In surveying these methods, we address their underlying assumptions, methodologies, and novel applications.