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Masks Used (mask + used)
Selected AbstractsMethodological considerations for measuring rates of brain atrophyJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2003Jeffrey L. Gunter PhD Abstract Purpose To systematically compare two techniques for measuring brain atrophy rates from serial magnetic resonance imaging (MRI) studies. Materials and Methods Using the separation in atrophy rate between cohorts of cognitively normal elderly subjects and patients with Alzheimer's disease (AD) as the gold standard, we evaluated 1) different methods of computing volume change; 2) different methods for steps in image preprocessing,intensity normalization, alignment mask used, and bias field correction; 3) the effect of MRI acquisition hardware changes; and 4) the sensitivity of the method to variations in initial manual volume editing. For each of the preceding evaluations, measurements of whole-brain and ventricular atrophy rates were calculated. Results In general, greater separation between the clinical groups was seen with ventricular rather than whole-brain measures. Surprisingly, neither the use of bias field correction nor a major hardware change between the scan pairs affected group separation. Conclusion Atrophy rate measurements from serial MRI are candidates for use as surrogate markers of disease progression in AD and other dementing neurodegenerative disorders. The final method has excellent precision and accurately captures the expected biology of AD,arguably the two most important features if this technique is to be used as a biomarker of disease progression. J. Magn. Reson. Imaging 2003;18:16,24. © 2003 Wiley-Liss, Inc. [source] Surgical mask used as a harnessPEDIATRIC ANESTHESIA, Issue 5 2006Vrushali Ponde MD No abstract is available for this article. [source] The volatility of the amygdala response to masked fearful eyesHUMAN BRAIN MAPPING, Issue 10 2010Thomas Straube Abstract Recently, it has been suggested that backwardly masked, and thus subliminally presented, fearful eyes are processed by the amygdala. Here, we investigated in four functional magnetic resonance imaging experiments whether the amygdala responds to subliminally presented fearful eyes per se or whether an interaction of masked eyes with the masks or with parts of the masks used for backward masking might be responsible for the amygdala activation. In these experiments, we varied the mask as well as the position of the target eyes. The results show that the amygdala does not respond to masked fearful eyes per se but to an interaction between masked fearful eyes and the eyes of neutral faces used for masking. This finding questions the hypothesis that the amygdala processes context-free parts of the human face without awareness. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] Flow-dependent resistance of nasal masks used for non-invasive positive pressure ventilationRESPIROLOGY, Issue 4 2006Wolfram WINDISCH Objective and background: Endotracheal tube resistance is known to be flow-dependent and this understanding has improved the application of invasive ventilation. However, similar physiological studies on the interface between patients and non-invasive positive pressure ventilation (NPPV) have not been performed. Therefore, this study was aimed at investigating the resistance of nasal masks used for NPPV. Methodology: The flow-dependent pressure drop of the small (S), medium-small (MS) and medium (M) Contour Nasal Mask (Respironics Inc., Murrysville, PA, USA) was measured with and without a connecting tube (length 18 cm, internal diameter 1.5 cm) in a laboratory study. The resistance was calculated by Rohrer's equation using the standard least-squares-fit technique. The present study explicitly differentiated between the resistance of the nasal mask alone when measured against atmosphere and the additional resistance caused by the nasal mask when airtightly fitted to a model head (interaction with the face). Results: Higher flow rates resulted in a non-linearly increasing pressure drop across the interface. This flow-dependent resistance of the S/MS/M mask was comparably low when not interacting with the face, but increased when interacting with the face. This flow-dependent resistance of the mask was several-fold higher when adding the connection tube and tended to be higher during expiration. Conclusion: There is a non-linear flow-dependent pressure drop across the nasal mask which is low and independent of its size, but increases when interacting with the face. The connecting tube is the major determinant of the resistance originating from facial appliances used for NPPV. [source] | ||||||||||