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Published byAyanna Frothingham Modified over 9 years ago
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The importance of MRI, a few numbers 10 000 MRI units worldwide in 2003 75 millions scans per year performed Constant need for over 1000 MRI technologists per year MRI magnet have 1.5-2.0 Tesla (same strength as magnet used in car junk yard) 1 Tesla=10 000 gauss, earth magnetic field=0.5 gauss
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Background Info on Magnetic Resonance Proton imaging and the use of hydrogen Magnetic field of H Behaviour in an external magnetic field Nuclear magnetic resonance
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How is an image obtained? Isolation of slice of tissue Creation of a magnetic field The perpendicular magnetic field Repetition at different angles Collection of data in computer and Fourier transform
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Diagram taken from “Basics of Magnetic Resonance Imaging” p.21
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What can we deduce from the H values obtained? The behaviour of regional hydrogen T1 of hydrogen Time required for the hydrogen nuclei to emit 63% of absorbed energy from stimulating pulse T2 of hydrogen (relaxation constant) Time necessary for 63% of signal to be lost due to dephasing Factors affecting T1 and T2
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Main component of an MRI Main magnetic field The problem of electrical resistance Aluminium as the conductor of choice Gradient coils Rf coils (radio frequency source and pulse programmer)
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MRI Limitations Shape and size Scanning time Gradient coil and noise Patient discomfort Pacemaker and artificial body part Complexity and cost
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Advantages of MRI Bones are invisibles Any plane can be scanned Tissue characterization Less tissue heating
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The Future of MRI The trend toward lower field strength Understanding Alzheimer’s disease Non-invasive quantification of blood flow Open doors in understanding brain processes
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