Brain Imaging

Question 1

Plain X-Ray Mech/Use

Answer 1

Electrodes released from cathode to anode, which release X-Rays to pass through tissues. Gives info about skull but not soft contents

Question 2

Conventional Angiography Mech/Use

Answer 2

Inject soluble contrast agent and can take series of images to watch spread and see anything about circulation/aneurysms

Question 3

Computerized Tomography (CT) Mech

Answer 3

Multiple X-Rays taken rotating around and reconstructed. Resolution enhanced by reconstruction of repeated measurements at different angles

Question 4

CT Scan Use

Answer 4

80% of strokes are ischemic and thus helped by thrombolytic agents, but 20% are hemorrhagic so that makes worse. Ischemics show up as low density and hemorrhagics as high on CT so that can determine treatment quickly

Question 5

Positron Emission Tomography (PET) Mech

Answer 5

Radiolabel things we already have (C, F, etc) with unstable extra proton, which will turn into neutron and positron which is ejected. Then collides w/ e- and releases two opposite gamma rays in 180deg directions (so filter out noise). Differences b/w regions arise from distribution of radiolabeled compound

Question 6

PET Use

Answer 6

Add to glucose, so add F18 to glucose which will be taken up by GLUT but not broken down and can see active regions of brain that take up more of it

Question 7

Mean Difference Image

Answer 7

Take control state PET of brain, then subtract it from the task state to find multiple individual difference images and take their mean

Question 8

PET in Parkinson’s

Answer 8

Image postsynaptic DA Rs in Striatum w/ 11C and presynaptic uptake w/ 18F (from substantia nigra). In Parkinson’s presynaptics will have decreased labeling and postsynaptic will have normal

Question 9

PET in Alzheimer’s

Answer 9

Posterior cingulate hypometabolism bc that’s autobio region

Question 10

MRI Mech

Answer 10

Use magnetic field to cause H protons to align spins, then knock out with radio signal, then measure relaxation - time it takes for prot to realign and emit radio signal. Different environments have different rates

Question 11

MRI in MS

Answer 11

Can tell white from gray/myelinated vs. demyelinated. So can see transient demyelination areas

Question 12

fMRI Mech

Answer 12

Activated neurons take up more O2, so blood flow disproportionately increases to counteract and see more spin phasing from oxy-Hb. So effect not immediate or absolutely specific (but better resolution than PET)

Question 13

2 fMRI Uses

Answer 13

Neuroscience research and presurgical-mapping