Psy 123_Lec 5

Deyoe 1994 must have person in a high mag eld when in

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Unformatted text preview: nce of an externally generated static magnetic field.” (DeYoe, 1994).! Must have person in a high mag. field. When in the mag field the hydrogen protons will align with mag. field and spin around, and eventually come back around... After the RF pulse, the spinning proton returns to a state of low-energy, parallel to the magnetic field. This releases electromagnetic energy that can be detected by a RF coil.! Anatomical MRI! T1 weighted images! Different tissues have different relaxation rates.! Thus some tissues will appear brighter than others Functional MRI (fMRI)! T2* weighted images! Oxygenated and deoxygenated hemoglobin also have different relaxation rates (BOLD).! magnetic field! Physics of fMRI! Physics of fMRI! VOXEL (Volumetric Pixel) Slice Thickness e.g., 6 mm In-plane resolution e.g., 192 mm / 64 = 3 mm 3 mm IN-PLANE SLICE SAGITTAL SLICE Number of Slices e.g., 10 Matrix Size e.g., 64 x 64 Field of View (FOV) e.g., 19.2 cm Collect many different slices (x25) and within each slice of data collecting data in small VOXELs of space. Typically 64 X 64 6 mm 3 mm Physics of fMRI! Conventional Imaging! 64 radio frequencies (RF) are sent with a repetition time (RT) of 50 milliseconds. One slice takes 3.2 seconds, 25 sli...
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This note was uploaded on 01/18/2014 for the course PSY 123 taught by Professor Staff during the Fall '11 term at UCSB.

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