1. Basics of MRI and MRI safety
BCS204 Week 10.1
3/18/2019

2. MRI scanner: a gigantic magnet
How big?
Most scanners for research: 3 Tesla (or 30,000 gauss)
Earth magnetic field: 0.5 gauss
Strong magnetic field formed by superconductive coil
No radiation (unlike X-ray and CT scans)

3. What happens if someone brought metal into the scanner room…
Anything metal can be disastrous in the scanner room!!

4. Quenching a magnet (the last resort)

5. How MRI scan works
Protons in water molecules align in the same or opposite direction with the magnetic field
Some with high, and some with low energy (LE)
RF pulse disturbs the alignment of LE protons
RF pulse stops; LE protons resume the original alignment
Receiver coil gets the signal

6. Inside the scanner

7. Inside the scanner MAGNET IS ALWAYS ON (UNLESS QUENCHED)!!!

8. MRI scanner at Center for Advanced Brain Imaging and Neurophysiology (CABIN)
SIEMENS PRISMA, 3 Tesla

9. A typical fMRI scan protocol
Each of the following is a pulse sequence. A series of pulse sequences is called a protocol.
Localizer (~15 s): a low resolution anatomical scan; just to locate the brain so that the following scans can be performed.
Some studies also employ a “Turbo Flash Localizer” (”TFL”) – a bit higher resolution - for studies that care about the coverage of certain regions
Anatomical scan (~4-6 mins): to get the anatomical structure of the brain
Functional scan (BOLD) (length dependent on experiment)

10. Most common parameters manipulated by experimenters in a pulse sequence
Repetition time (TR): the time between RF pulses
1 scan/shot generated per TR
Number of slices
If 42 slices, each scan/shot contains a mosaic of 42 smaller images, each of which is a slice.
Slice thickness (2-3mm)
Resolution (2 by 2 by 2mm of one voxel)