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Transcript of MRI physics
= 1 excess
= 6 excess
= 6 excess
T 1 relaxation
enhance T1 and T2 relaxation
Superparamagnetic Iron Oxide (SPIO, USPIO)
T2 and T2* signal drop
Non -enhanced and Gadolinium Enhanced
Tanimoto A. Eur J Radiol. 2006
Small Animal protocols: intra-cranial
to define lesion margins
and increase detection
@ 1T, only 6 per 1,000,000 are in excess
1 drop of water will still have 15 million billion excess protons available.
MW <180 da
T2 relaxation / spin spin
Spatial Resolution and multiplanar imaging
out of phase
out of phase
TR = Repetition time. Time between applied pulses.
TE = Echo time. Time to listen for echo pulse back.
T1, T2* and T2 effects are happening in close timing to each other. Over a couple milliseconds.
mw: ~590 da
Abundance in tissue!
MRI is the utilisation of Nuclear Magnetic Resonance for the formation of medical images depicting internal structures.
There is no ionizing radiation.
Large Magnetic Field needed
RF pulse applied to excite protons
Relaxing protons emit RF echo.
Receiver Coil detects this echo at a specified time.
Bright = High Signal = hypERintense
Dark = Low Signal = hypOintense
T2 = Bright fluid & fat
T1 = Bright fat only
Small Animal protocols: spinal
Equine Imaging Protocols
Magnetic fields and Hydrogen Atoms
Excitation and Relaxation
Fat and Water are hyperintense.
Provides best neuro tissue contrast
Only fat is Hyperintense
Provides homogenous soft tissue contrast.
Pre and Post contrast sequences
Highly susceptible to changes in the magnetic field.
(e.g. Metallic composition or gas)
Suppresses free water molecules (CSF in ventricles), but not bound water molecules (Oedema)
Suppresses Fat signal, but not water.
Visualisation of overall proton density. Hydrated tissues such as neuro tissue will be more hyperintense than bone.
58 µT = Earth's Magnetic Field Strength
0.05 T = Fridge magnet.
0.3T = LAC low field magnet.
1.5T - 3T = Typical Medical Strength Scanners