lecture 4

Question 1

CAT
PET
MRI

Answer 1

c = X-ray
p= function
m = high resolution - closest to real.

Question 2

CAT (CT)

Answer 2

dark = low density
light = high density
put all 6 slices together to get 3D image.

Question 3

image acquisition - slicing orientation

Answer 3

• ascending: bottom to top
• descending: top to bottom
• interleaved: odd numbers up, then even numbers up. try to get from top to bottom quickest - then fill in gaps.

Question 4

MRI

Answer 4

static coil - always on. aligns hydrogen atoms in water in body.
radio frequency field pulse sequence:
-transmitter coil: perturbs static field, excited H for it to absorb energy, . once turned off, H re-align = detected & create image.
- receivor coil: reception, image acquisition.
gradient field: spatial info - help tell where image is coming from.

Question 5

anatomical vs functional imaging

Answer 5

A = MRI, CAT = what brain looks like
F= PET = how brain works.

Question 6

first functional brain experiment

Answer 6

Mosso - tippy scale. patient balanced on it. as they started thinking the scale would tip more towards their head

Question 7

PET

Answer 7

positron emission tomography. functional technique
-radioactive tracers, O2, Glucose. go to area where there s high blood flow/brain activity. radioactive metabolized = releases positron, attract electron. when they meet = ollide & annihilate each other = give off energy as light.

Question 8

PET activation
subtraction
averaging

Answer 8

Start with control = no stimulation - image brain. baseline.
activation = activated areas by observing/listening or other cognitive task.
subtraction = subtract baseline/control from stimulation image to get area that is only related to stimulated. average many stimulated within one patient.
averaging = average within one patient, many rounds and later, many patients average of rounds.

Question 9

fMRI

- BOLD signal

Answer 9

Blood Oxygenation Level Dependent (BBOLD) signal - measure of neural activity.
neurovascular coupling = neurons fire = need more O2 = attain fMRI image that way.

Question 10

clinical uses of fMRI

Answer 10

brain tumor
drug abuse/addiction (long term use, treatment)
drug studies (drug on cognition/brain)
neuropsychological disorders.  (function = distinction among subtypes(

Question 11

fMRI - working memory, alcoholics

Answer 11

chronic alcoholics = significantly less brain function during working memory use. 
function can come back within 8 days.

Question 12

fMRI setup for visual test

Answer 12

• glass/mirror system. project video screen without putting metal screen in MRI machine.

Question 13

contrast: anatomical

define

Answer 13

the ability to distinguish between 2+ different properties of tissue

Question 14

functional contrast

define

Answer 14

contrast should really be considered as “contrast to noise”: how effectively can we decide whether a given brain region has property X or property Y

Question 15

spatial resolution: voxels

different between functional and anatomical

Answer 15

voxel - small cubic prism that is the basic sampling unit of fMRI. typical functional voxel: 3mm^3, typical anatomical voxel: 1mm^3

Question 16

spatial resolution
temporal resolution
invasiveness

higher field strength = greater resolution in MRI

Answer 16

SR = how fine can we see things in the brain
TR = time, slow or real time.
invasive ness.

higher field strength = greater resolution in MRI. limits how much and how often you can put someone in there.

Question 17

hemodynamic lag

Answer 17

blood flow to brain is slow, so real time response pictured by fMRI is a little bit slower than the activation of the area.

Question 18

MRI safety

Answer 18

appropriate risk level : research participant < clinical patient.

Question 19

x-ray

Answer 19

2D - x-ray passes thru skull onto x-ray sensitive film. absorbed at different degrees by different tissues.

Question 20

pneumoencephalography

Answer 20

take CSF out, and put air in. as it enters the ventricles = ventricles stand out clearly

Question 21

angiography

Answer 21

imaging blood vessel. substance absorbs x-ray injected into blood stream.

Question 22

cortical thickness thru development

Answer 22

frontal cortex = thinner

language area =thicker