Brain Imaging

Question 1

What are the advantages of brain imaging?

Answer 1

1. Provides important information about the structure and function of the brain
2. Diagnosis of neurological disorders and trauma. Non-invasive technique
3. Important for research: neuroscience, medical, psychology

Question 2

What are the techniques of this lecture?

Answer 2

CT: computed tomography
MRI: magnetic resonance imaging
PET: positron emission tomography
MRA: magnetic resonance angiography

Question 3

CT scan?

Answer 3

uses (3D) multidimensional x-ray scanning with computer-aided reconstruction; it scans 180

Question 4

What do CT scans look like?

Answer 4

Bones appear white (obviously). Matter is gray. CSF filled areas are dark. Left side of the brain appears on the right side of the image.

Question 5

What is MRI?

Answer 5

It is a techqnique that provides images using magnetic fields (of hydrogen atoms) and pulsed radiofrequency waves

Question 6

Who developed MRI?

Answer 6

Lauterbur, Mansfield and Damadian.

Question 7

How does MRI work at the level of the proton?

Answer 7

1. A vertical external magnetic field is applied to align all the protons in the same direction.
2. Then a horizontal magnetic field pulse forces the wobble or precess in phase. Which creates an electrical signal in the RF coil
3. When you turn off the radio frequency pulse, the relaxation of the magnetic signal is measured. T2 weighted images
4. Protons realign with vertical field. T1 weighted images

Question 8

What do T1 weighted images look like?

Answer 8

liquid appear dark, matter appears bright

Question 9

What do T2 weighted images look like?

Answer 9

liquid appears bright, white matter appears dark

Question 10

What happens with the electrical signal?

Answer 10

1. RF coil sends signal to A/D converter
2. Image processor Fourier transformation to create actual image
3. Computer reconstructs the 3D information

Question 11

What is fMRI?

Answer 11

It is a functional MRI that measures neuronal activity by measuring small changes in blood flow or the ratio of oxyhemoglobin/deoxyhemoglobin.

Question 12

What is PET scan?

Answer 12

1. It is a technique that injects FDG (F-fluoro-2-deoxyglucose) into the bloodstream. FDG is taken up by cells but not metabolized.
2. FDG emits positrons which reacts with electron emitting opposing gamma rays to release two photons (light).

Question 13

How do you interpret PET scans?

Answer 13

Red and yellow indicate high activity. Blue indicates low activity.