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Standard Resolution (standard + resolution)
Selected AbstractsFollow up of coiled intracranial aneurysms with standard resolution and higher resolution magnetic resonance angiographyJOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 1 2008S Dupre Summary Time-of-flight magnetic resonance angiography is a non-invasive alternative to digital subtraction angiography (DSA) for follow up of coiled intracranial aneurysms. Standard cranial MRA protocols are a compromise between spatial resolution and imaging time. This study compares a standard resolution MRA protocol with a protocol at higher spatial resolution MRA (HR-MRA) in 21 follow-up occasions in 17 coiled aneurysms in 15 patients. Images were reviewed for presence of residual or recurrent aneurysm and compared with DSA as the gold standard. Aneurysm flow signal on standard resolution MRA differed significantly from HR-MRA in 6/21 cases (P = 0.02) and DSA in 6/21 cases (P = 0.02). HR-MRA had 100% concordance with DSA (P = 1.0). In this study, three-dimensional time-of-flight magnetic resonance angiography carried out at standard resolution is inadequate for follow up of coiled intracranial aneurysms. HR-MRA is comparable to DSA for detection of aneurysm recurrence. [source] The benefits of rapid 3D fMRIINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 1 2010Martin A. Lindquist Abstract Functional magnetic resonance imaging (fMRI) provides the ability to image blood dynamics through the entire brain with a high spatial resolution. However, the temporal resolution is much slower than the underlying neuronal activity one seeks to infer. Recent developments in rapid imaging allow 3D fMRI studies to be performed at a temporal resolution of 100 ms; a 10-fold increase compared to standard approaches. This increase in temporal resolution offers a number of potential benefits. First, it allows the focus of analysis to be shifted from changes in blood flow taking place 5,8 s after neuronal activity to more transient changes taking place immediately following activation. We argue that studying these changes provides valuable information about the relative timing of activation across different regions of the brain, which is crucial for inferring brain pathways. Second, rapid imaging allows for the efficient modeling of physiological artifacts without problems with aliasing; something that is difficult at standard resolutions. We illustrate how removal of these artifacts provides the increase in signal-to-noise ratio required for studying the subtle changes in oxygenation we are interested in. Finally, we show how high temporal resolution data provides the opportunity to focus the analysis on the rate of change in oxygenation rather than the level of oxygenation as is the current practice. The price of performing rapid imaging studies is a decrease in spatial resolution. However, we argue that the resolution is still comparable to the effective resolution used in most fMRI studies. We illustrate our approach using two fMRI data sets. © 2010 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 20, 14,22, 2010 [source] Errors in surface rainfall rates retrieved from radar due to wind-driftATMOSPHERIC SCIENCE LETTERS, Issue 1 2005Steven A. Lack Abstract This article describes a series of experiments based on real data wherein the advection of the precipitation below the radar-sampled volume is estimated using Doppler radar determined wind fields. The experiments show that even at standard resolutions of 2 km the error can be extensive, and at higher resolutions and greater ranges (higher beam elevations) the errors become very large. Errors are assessed using different Z,R relationships and resolutions as high as 0.5 km. Copyright © 2005 Royal Meteorological Society [source] | ||||||||||