Exam, neuroimaging 2

Question 1

what is apparent diffusion coefficient?

Answer 1

Apparent diffusion coefficient (ADC) is a measure of the magnitude of diffusion (water molecules) within tissue, and is commonly clinically calculated using MRI with diffusion weighted imaging (DWI)

Question 2

How does the measurement time effect the ADC?

Answer 2

A larger measurement times typically result in a lower ADC value

Question 3

What is diffusion weighting MR contrast?

Answer 3

Diffusion-weighted (DW) magnetic resonance (MR) imaging provides potentially unique information on the viability of brain tissue. It provides image contrast that is dependent on the molecular motion of water, which may be substantially altered by disease.

Question 4

How does Diffusion Weighting MR contrast work?

Answer 4

The MR signal becomes sensitive to motion occurring along the direction of the diffusion gradients

Question 5

Except for the diffusion tensor model, how can we describe the diffusion signal?

Answer 5

The diffusion signal can be described by complex mathematical models

The mathematical model enables to identify multiple fibre populations within each voxel in the brain, so as to perform fibretracking in crossing fibre regions

Question 6

what is a voxel?

Answer 6

A volume element

A pixel in 2D

Question 7

What is the clinical and research application of diffusion weighted imaging mainly including?

Answer 7

1. stroke
2. tumour characterization
3. investigating changes in brain connectivity due to pathology

Question 8

How does high measurement times effect the mean square displacement of water molecules in biological tissues?

Answer 8

A high measurement time result in a plateau

Question 9

What is Diffusion Tensor MR imaging?

Answer 9

• A special kind of Diffusion weighed imaging (DWI)
• Used to map white matter tractography in the brain
• The typical parametric maps derived from DTI includes fractional anisotropy and mean diffusivity

Question 10

Name some of the recent developments in the MRI equipment!

Answer 10

1. Stronger gradient fields

2. improvements in receiver coils enabled to increase signal-to-noise and acquisition rates.

Question 11

What is the current research using Diffusion Weighted Imaging including?

Answer 11

1. improving temporal resolution

2. improving spatial localization in fMRI imaging