fMRI and MR Spectroscopy

BOLD

• BOLD=Blood Oxygenation Level Dependant contrast

• Neurons at work use oxygen (carried by hemoglobin)

• 1-5 s. delay, peaks at 4-5 s.• T2 or T2* contrast• 2-4 mm spatial resolution• 1-4 s. temporal resolution

fMRI exam

• High resolution image of brain taken• Series of scans over time

– Lower resolution– T2 or T2* weighted

• Subject performs task, rests, performs task, rest, etc.

• Task can be visual, auditory, sensory, cognitive…

• Statistical analysis performed

Activated Regions

3D Reconstruction

http://www.fmrib.ox.ac.uk/fmri_intro/trans_anim.gif

Stroop Test

• http://www.david.tam.name/SelfTests/StroopEffects.html

• http://www2.b3ta.com/clickthecolour/• http://www.pbs.org/wgbh/nova/everest/exp

osure/strooptest.html• Results:• http://spnl.stanford.edu/healthy_brain/studi

es/hb_study_03.htm

Other Cognitive tests

• http://www.cogtest.com/int_test/GoNoGoFlash1.html

• Face recognition results• http://www.perceptionandaction.com/pdf/

publications/MarottaGenoveseBehrmann-2001-002.pdf

MRS• Image 1H NOT in water

– Large voxel• Molecules have distinct RFs

– ‘chemical shift’ = distance from RF of water• Supress water signal to ‘see’ other signals

Chemical Shift• Area under peak gives concentration

http://www.mrispectroscopy.com/mrs.htm

Cases

http://www.mrispectroscopy.com/Case_list.htm