16-11-2012, 05:04 PM
Nuclear megnetic resonance (NMR)& magnetinc resonance imaging (mri)
Nuclear megnetic resonance.ppt (Size: 7.22 MB / Downloads: 88)
magnetinc resonance imaging (mri)
Magnetic nuclei are abundant in the human body (H,C,Na,P,K) and spin randomly
Since most of the body is H2O, the Hydrogen nucleus is especially prevalent
Patient is placed in a static magnetic field
Magnetized protons (spinning H nuclei) in the patient align in this field like compass needles
Radio frequency (RF) pulses then bombard the magnitized nuclei causing them to flip around
The nuclei absorb the RF energy and enter an excited state
When the magnet is turned off, excited nuclei return to normal state & give off RF energy
The energy given off reflect the number of protons in a “slice” of tissue
Different tissues absorb & give off different amounts of RF energy (different resonances)
The RF energy given off is picked up by the receiver coil & transformed into images