12 results found
Wardlaw JM, Brindle W, Casado AM, et al., A systematic review of the utility of 1.5 versus 3 Tesla magnetic resonance brain imaging in clinical practice and research, European Journal of Radiology, ISSN: 0720-048X
Brazzelli M, Shuler K, Quayyum Z, et al., 2013, Clinical and imaging services for TIA and minor stroke: results of two surveys of practice across the UK, BMJ Open, Vol: 3, Pages: e003359-e003359, ISSN: 2044-6055
Wardlaw JM, Brindle W, Casado AM, et al., 2012, A systematic review of the utility of 1.5 versus 3 Tesla magnetic resonance brain imaging in clinical practice and research, EUROPEAN RADIOLOGY, Vol: 22, Pages: 2295-2303, ISSN: 0938-7994
Wardlaw JM, O'Connell G, Shuler K, et al., 2011, “Can It Read My Mind?” – What Do the Public and Experts Think of the Current (Mis)Uses of Neuroimaging?, PLoS ONE, Vol: 6, Pages: e25829-e25829
Gowland PA, De Wilde J, 2008, Temperature increase in the fetus due to radio frequency exposure during magnetic resonance scanning, Physics in Medicine and Biology, Vol: 53, Pages: L15-L18, ISSN: 0031-9155
De Wilde JP, Grainger D, Price DL, et al., 2007, Magnetic resonance imaging safety issues including an analysis of recorded incidents within the UK, PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY, Vol: 51, Pages: 37-48, ISSN: 0079-6565
De Wilde JP, Rivers AW, Price DL, 2005, A review of the current use of magnetic resonance imaging in pregnancy and safety implications for the fetus, PROGRESS IN BIOPHYSICS & MOLECULAR BIOLOGY, Vol: 87, Pages: 335-353, ISSN: 0079-6107
Delakis I, Petala K, De Wilde JP, 2005, MRI receiver frequency response as a contributor to Nyquist ghosting in echo planar imaging., J Magn Reson Imaging, Vol: 22, Pages: 324-328, ISSN: 1053-1807
PURPOSE: To study the frequency response characteristic of the MRI signal receiver system as a contributing factor to the formation of Nyquist ghosting in echo-planar imaging (EPI). MATERIALS AND METHODS: Experimental work was undertaken on a 1.5 T system. A cylindrical test object filled with water was imaged axially with EPI in the center of the quadrature, transmit-receive head coil. In the first set of experiments, the water conductivity was increased progressively with the addition of salt between EPI acquisitions. In the second set of experiments, the conductivity of the water in the test object was kept constant and EPI images were acquired at several different bandwidths. A computer simulation was also implemented to demonstrate the impact of changes in the frequency response characteristic of the signal receiver system on EPI Nyquist ghosting. RESULTS: Experimental and simulation results showed that Nyquist ghosting increased with the variation of the frequency response characteristic within the effective frequency range determined by the image bandwidth. One can increase the variation in the frequency response characteristic by increasing its steepness over the image's bandwidth window when coil loading is decreased, or by increasing the effective frequency range when image bandwidth is increased. CONCLUSIONS: The results of this research may help reduce Nyquist ghosting in EPI studies when the imaging coil is not sufficiently loaded, such as in pediatric and phantom studies.
Delakis I, Moore EM, Leach MO, et al., 2004, Developing a quality control protocol for diffusion imaging on a clinical MRI system, PHYSICS IN MEDICINE AND BIOLOGY, Vol: 49, Pages: 1409-1422, ISSN: 0031-9155
Price DL, De Wilde JP, Papadaki AM, et al., 2001, Investigation of acoustic noise on 15 MRI scanners from 0.2 T to 3 T, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 13, Pages: 288-293, ISSN: 1053-1807
De Wilde JP, Lunt JA, Straughan K, 1997, Information in magnetic resonance images: evaluation of signal, noise and contrast., Med Biol Eng Comput, Vol: 35, Pages: 259-265, ISSN: 0140-0118
The assessment of diagnostic image quality for MRI is considered. The assessment of three key image quality determinants is addressed: signal, noise and contrast. There is a distinction between random noise evaluation, for the calculation of the SNR, and structured noise evaluation for the assessment of image artefacts. Specific methods used are correlation techniques and the Wiener spectrum. Contrast is assessed by comparison of experimental data and theoretical predictions. For each assessment, the theory and method of the evaluation strategy are discussed. The discussion is illustrated with analysis results from commercial MR systems. The choice of analysis method and the subsequent derivation of quality indices are shown to be critical in respect of robustness and accuracy.
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