Imaging of the brain

Question 1

AD on MRI

Answer 1

Reduced hippocampal volume

Parietal atrophy

Question 2

FTD on MRI

Answer 2

Atrophy in frontal or temporal lobes

Question 3

Neurodegenerative disease PET scan

Answer 3

AD metabolism (sugar or tau protein) - reduced perfusion in brain

Question 4

DAT scans

Answer 4

• Ioflupane (I-123)

- High affinity for presynaptic dopamine transporters (DAT) which are abundant in striatal region

Question 5

Advanced MRI - arterial spin labelling

Answer 5

• Endogenous contrast media (blood) rather than exogenous contrast (gadolinium)
• Signal can be used as a surrogate for perfusion of brain to determine pathologies that aren’t visible on structural imaging alone

Question 6

Magnetic resonance spectroscopy

Answer 6

• Distribution of electrons in an atom
• Small differences in resonant frequencies between atoms = different MR signals
• MR spectra can be calculated from MR signals made by these atoms
• Provides info about chemical composition of tissues - tumour characterisation and treatment response
• As grade of tumour increases, NAA and creatine decrease but lipids and lactate increase
• High grade brain tumour = reduced NAA peak

Question 7

Diffusion tensor imaging

Answer 7

• Estimates white matter of brain
• Diffusion weighted imaging evaluates stroke
• We can see when a tumour disrupts white matter tracts

Question 8

fMRI

Answer 8

• Deoxyhaemoglobin used as paramagnetic contrast agent (BOLD effect)
• BOLD used as surrogate for neuronal activity - related to glutamate uptake in astrocytes (initial increase in deoxyHb with neuronal activity = reduced signal but rCBF then increases and increases signal as excess oxygenation)
• Visual, motor, speech and memory paradigms