MRI

• Magnetic Resonance Imaging (MRI) is a computer-based cross-sectional imaging modality that uses magnetic fields and radio waves to obtain a mathematically reconstructed image.
• MRI was originally called Nuclear Magnetic Resonance.
• The main advantage of MRI is its low contrast resolution.
• X-ray attenuation coefficient in soft tissue differs by less than 1%.
• Spin density and T1 differ by 20-30% in the same tissue.
• T2 differs by 40% in the same tissue.
• MRI does not use ionizing radiation.
• MRI provides clear images without superimposition of structures and can resolve relatively small contrast differences among tissues.
• Contrast in MRI depends on the interaction of matter with electromagnetic forces.
• Conventional radiography provides a "flat" image with structures superimposed and requires contrast media to clearly distinguish one anatomic structure or organ from one another.
• MRI contraindications include cardiac pacemakers, aneurysm clips, claustrophobia, metallic fragments in the eye, cochlear implants, internal drug infusion pumps, neurostimulators, and bone growth stimulators.
• In the 1940s, Felix Bloch and Edward Purcell discovered the properties of magnetic resonance and used the technique for analysis of complex molecular structures and dynamic chemical processes.
• Raymond Damadian showed in 1971 that the relaxation time of water in the tumor differed from the relaxation time of water in normal tissue.
• Paul Lauterber published the first cross-sectional image of objects obtained with the MRI technique in 1973
• The first human head scans were obtained followed by the first human body scans in the 1978
• The original name of the first MRI machine was Indomitable.
• 1952, Felix Bloch and Edward Purcell shared a Nobel Prize in Physics
• 1975, Raymond damadian obtained the first animal images
• 1970, MRI progressing rapidly
• MRI Contraindication: Cardiac Pacemakers, Aneurysm Clips, Claustrophobia, Metallic fragments in the eye, Cochlear Implants, Internal drug infusion pumps, Neurostimulators, Bone growth stimulators
• Antenna is a device transmitting or receiving radio waves
• Artifacts a spurious finding in or distortion of an image
• Attenuation a reduction in energy amount of a beam of radiation when it passes through tissue or other substances
• Coil a single multiple loops of wire designed to produce a magnetic field from current flowing through the wire
• Claustrophobia is the fear of having no escape or being in closed spaces or rooms
• Cryogenic relating to extremely low temperature
• Diffusion is a spontaneous random motion of molecules in a medium
• Fat Suppresed Image is a fat tissue in the image is made to be of a lower, darker signal intensity
• Free Induction Decay is a signal-emitted by tissue after RF excitation
• Gating is used in reducing motion artifacts
• Gradient Echo: Fast pulse sequence, Often used with 3D imaging to generated T2 - weighted images
• What is Gradient Echo?

  Fast Pulse sequence, Often used with 3D imaging to generate T2 weighted images
• Gyromagnetic Ration is a constant specific ratio for each nucleus, half life in MRI
• Gyromagnetic Ratio UNIT: MHz/T
• Gyromagnetic Ratio is the most abundant element in the body of 60%
• Inverse Recovery is a standard pulse sequence available in most MRI images, used for t1 weighted images
• Larmor Frequency is the frequency at which a nucleus precesses in the magnetic field. UNIT:MHz
• Magnetic Moment is a force created when magnetic dipole is in a magnetic field. The inherent magnetism. UNIT: T
• Magnetization is the large scale macroscopic magnetic moment resulting from many nuclear magnetic moments
• Net Magnetization is a magnetic of individual nuclei aligned in the external magnetic field