- Used for
- Language localization
- Reading
- Noun thinking
- Motor localization
- Hand movement
- Lip puckering
- Mechanism
- Uses BOLD (blood-oxygen level dependent) contrast method.
- Taking advantage of neurovascular coupling: close relationship between local neuronal activity and blood flow
- Steps
- Pilot Scan
- Used to plan other scans
- Structural scans to overlay fMRl on
- 6-8 minute 3D scan
- Patient given task in MRI scanner causing Brain activation
- Typically last 5-8 minutes
- Collect at least 100 scans
- 50 task scans, 50 rest scans
- Task: Alternating active and baseline condition
- Finger motion & other motor tasks
- Language (comprehension & expression/ production)
- fMRI with motor paradigms
- Pre-operative planning for migrational anomaly, tumour or vascular lesion in close proximity to eloquent motor areas
- This includes hand, foot and face motor cortex, SMA, visual cortex
- Overall scan time 1-1.5 hours
- Post-processing Physics (up to 24 hours)
- Areas of brain activity has high blood flow → decrease deoxyHb in the area → decrease paramagnetic effect → decrease susceptibility of blood (deoxyHb) → increase intensity of signal of active brain
- T2* effect of
- Deoxyhb (paramagnetic- Has magnetic field disturbance)
- OxyHb (Diamagnetic - No magnetic field disturbance)
- Signal is small compared to noise in images
- Maximum change 3-5%
- How can we tell if a change in signal is real or just noise?
- Repeat the experiment lots of times!!
- >100 measurements required
- Need complex statistical software (SPM, FSL, Brain Voyager)
- Blood oxygen level dependent MRI (BOLD)
- False negative haemodynamic activation in vascular lesions and tumour with BBB breakdown
Sensitive scan
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