L2-Safety

L2-Safety - Zhong-Lin Lu Laboratory of Brain...

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Unformatted text preview: Zhong-Lin Lu Laboratory of Brain Processes (LOBES) Dana and David Dornsife Cognitive Neuroscience Imaging Center University of Southern California 1) Put subject in big static magnetic field [e.g., 3 T] 2) Transmit radio waves into subject [about 3 ms] 3) Turn off radio wave transmitter 4) Receive radio waves re-transmitted by subject – Manipulate re-transmission with magnetic fields during this readout interval [10-100 ms: MRI is not a snapshot] 5) Store measured radio wave data vs. time – Now go back to 2) to get some more data 6) Process raw data to reconstruct images The basic MRI procedure MRI/fMRI utilizes a very strong static magnetic field, time varying smaller magnetic fields (‘gradients’) and an electromagnetic, radio frequency field to create images. The static field is time invariant and is always on. The radio frequency electromagentic field (B1) used to excite the spins, and the gradient magnetic fields used to spatially encode, are rapidly turned on and off during scanning. Coils are used to create these fields, imposing a particular geometry upon the device itself. Finally, the ramping up and down of the gradient fields causes the coils to vibrate, causing loud noise associated with scanning.with scanning....
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This note was uploaded on 08/31/2009 for the course PSYC 425 taught by Professor Lu during the Spring '08 term at USC.

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L2-Safety - Zhong-Lin Lu Laboratory of Brain...

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