The importance of MRI, a few numbers  MRI units worldwide in 2003  75 millions scans per year performed  Constant need for over 1000 MRI technologists per year  MRI magnet have Tesla (same strength as magnet used in car junk yard)  1 Tesla= gauss, earth magnetic field=0.5 gauss

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

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

Diagram taken from “Basics of Magnetic Resonance Imaging” p.21

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

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)

MRI Limitations  Shape and size  Scanning time  Gradient coil and noise  Patient discomfort  Pacemaker and artificial body part  Complexity and cost

Advantages of MRI  Bones are invisibles  Any plane can be scanned  Tissue characterization  Less tissue heating

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