SLHS 539: 3/5 Part 3 "Neuroimaging"

Structural vs. Functional Imaging

• Structural: what the brain looks like, anatomy, static image

• Functional: how the brain FUNCTIONS, what it does

What does neuroimaging methods allow us to see?

• detailed images of brain STRUCTURES

• tells us what part of the brain is damaged

  • allows localization of stroke, tumor, etc.

—> for better diagnostic and surgical intervention

CT or CAT Scan

(computerized axial tomography scanning)

• computed axial tomography

• fancy x-ray with computer reconstruction

• requires radiation exposure

• x ray sources and x-ray detectors that move around in order to develop a 3-D image

• high density = white

  • low density = black (ex. csf)

MRI

• structural / functional ?

• how does it work

• invasive or non-invasive

• structural (magnetic resonance imaging)

• hydrogen of atoms in body can be manipulated so they generate a signal that can be mapped and turned into an image

• non-invasive

1. protons spin around randomly

2. when they are placed in a magnetic field their spins will line up

3. an rf pulse is sent via a coil which changes the protons’ spins

4. image is generated from reaction time of atoms resetting to original position

T1 MRI vs. T2 MRI

T1: water black

T2: water white

T1 scans (short TR/TE) show anatomy best, with fat appearing bright and water/fluid appearing dark. T2 scans (long TR/TE) are sensitive to water and inflammation, making fluid/pathology appear bright and fat appear darker.

3-D Lesion Reconstruction Implications

Enhanced neuropsychological research

Diffusion Tensor Imaging (DTI)

• structural / functional

• how does it work

• what does it show

• structural imagine

• used to image the white matter of the brain

• looks at how water flows along the white matter pathways in order to image and get an idea of where these pathways are

Functional Neuroimaging allows us to…

How does it work?

Hemodynamic:

Imagine brain function in real time (not just the structure)

• Increase in neuronal activity leads to increase in metabolic demand for glucose and oxygen which increase cerebral blood flow to the ACTIVE region

• Hemodynamic = method measures changes in blood flow