MRI & subcortex ARTICLE (mini-quiz 4)

Question 1

What does computational neuroanatomy aim to study through imaging?

Answer 1

Computational neuroanatomy quantifies brain structure dynamics in both healthy and clinical populations using imaging and computational models.

Question 2

What imaging method is central to computational neuroanatomy, providing non-invasive structural insights?

Answer 2

Magnetic Resonance Imaging (MRI).

Question 3

What new field has emerged from biophysical modeling of MRI data, allowing for brain histology in living subjects?

Answer 3

In-vivo histology using MRI (hMRI).

Question 4

How does quantitative MRI (qMRI) improve neuroanatomical studies?

Answer 4

qMRI provides standardized, site-independent data, improving comparability across studies and longitudinal tracking.

Question 5

Name two tissue characteristics measurable by qMRI that are significant for studying brain microstructure.

Answer 5

Myelin and iron content.

Question 6

Which relaxation times in MRI (T1 and T2) are influenced by tissue microstructure and are markers for what component in brain tissue?

Answer 6

Both T1 and T2 relaxation times are influenced by myelin content in brain tissue.

Question 7

What does Magnetization Transfer (MT) measure, and why is it useful in brain imaging?

Answer 7

MT measures the exchange of magnetization between macromolecules and water, useful for assessing myelin density.

Question 8

How does diffusion imaging contribute to understanding brain microstructure?

Answer 8

Diffusion imaging reveals the microstructural organization by highlighting axonal properties and tissue density, providing insights into fiber tracts.

Question 9

What parameter derived from MRI is sensitive to brain iron concentrations, aiding in studies of neurodegeneration?

Answer 9

Magnetic susceptibility.

Question 10

What benefit does voxel-based morphometry (VBM) provide in MRI analysis?

Answer 10

VBM assesses differences in brain volume and tissue density across subjects, enabling studies on structural brain variations.

Question 11

Why are T1 and MT mapping techniques valuable for cortical myelination studies?

Answer 11

These techniques allow for non-invasive mapping of myelin content, enabling the delineation of cortical areas based on myelination.

Question 12

How does high spatial resolution improve qMRI-based computational neuroanatomy?

Answer 12

High spatial resolution enables detailed mapping of small brain structures and layers, increasing accuracy in identifying microstructural variations.

Question 13

Describe the “g-ratio” and its significance in MRI-based studies.

Answer 13

The g-ratio is the ratio of the inner axonal diameter to the total axon diameter, indicative of myelination efficiency and axonal conductance speed.

Question 14

Which type of MRI model integrates multiple qMRI parameters to estimate tissue features like myelin density and axonal properties?

Answer 14

Multi-compartment models.

Question 15

How does susceptibility-based imaging differ from other MRI modalities in detecting microstructure?

Answer 15

It detects magnetic susceptibility variations caused by iron or myelin, aiding in distinguishing calcifications from blood deposits.

Question 16

What are potential clinical applications of hMRI in neurodegenerative diseases?

Answer 16

hMRI can detect early microstructural changes, aiding in the diagnosis and monitoring of diseases like multiple sclerosis and Alzheimer’s.

Question 17

Why is standardized MRI important in large-scale neuroimaging studies?

Answer 17

It ensures consistency and comparability across different sites and time points, enabling robust multi-center and longitudinal studies.

Question 18

How does qMRI support research on age-related brain changes?

Answer 18

qMRI reveals patterns of microstructural changes, such as demyelination or iron accumulation, that correlate with aging.

Question 19

What does effective proton density (PD) mapping contribute to in MRI?*

Answer 19

PD* mapping aids in differentiating tissue classes and improving segmentation in morphometric analyses.

Question 20

Which techniques are used to compensate for motion artifacts in MRI-based studies of neuroanatomy?

Answer 20

Techniques like prospective motion correction and adaptive de-noising.

Question 21

What is the primary purpose of MR pulse sequences in MRI technology?

Answer 21

To manipulate and control the timing of radiofrequency pulses and gradients for optimal image acquisition.

Question 22

What are the basic components involved in an MR pulse sequence?

Answer 22

Radiofrequency pulses, gradients, and data acquisition windows.

Question 23

Explain the significance of the TR (Repetition Time) and TE (Echo Time) in MR imaging.

Answer 23

TR is the time between successive pulse sequences applied to the same slice. TE is the time between the delivery of the RF pulse and the peak of the signal received.

Question 24

What does the term ‘flip angle’ refer to in MR imaging?

Answer 24

The angle to which the net magnetization vector is tilted away from the magnetic field direction.

Question 25

What is a ‘spin echo’ in MRI?

Answer 25

A sequence that uses a 180-degree RF pulse to refocus dephased spins and generate a stronger signal.

Question 26

What is T1-weighted imaging, and what kind of information does it provide?

Answer 26

An imaging sequence that highlights tissues with short T1 times, like fat, to produce high-contrast images of anatomical structure.

Question 27

Describe the concept of T2-weighted imaging.

Answer 27

T2-weighted imaging emphasizes tissues with longer T2 relaxation times, often used to highlight differences between water and fat content.

Question 28

What role does the gradient echo play in MR imaging?

Answer 28

It provides a fast imaging technique that uses variable flip angles, making it useful for dynamic studies.

Question 29

What are inversion recovery sequences used for?

Answer 29

To null the signal from certain tissues, such as fat or fluid, to enhance contrast.

Question 30

To null the signal from certain tissues, such as fat or fluid, to enhance contrast.

Answer 30

Fluid-Attenuated Inversion Recovery is used to suppress fluid signals in the brain to better visualize lesions.

Question 31

Why is spatial resolution important in MRI, and how can it be optimized?

Answer 31

It determines the level of detail in the image and can be improved by adjusting the matrix size, field of view, and slice thickness.

Question 32

What are the trade-offs between signal-to-noise ratio (SNR) and resolution in MR imaging?

Answer 32

Increasing resolution generally decreases SNR, which requires adjustments in acquisition parameters to optimize both.

Question 33

What is the role of contrast agents in MR imaging?

Answer 33

To enhance the visibility of blood vessels, tumors, or other structures by altering the local magnetic environment.

Question 34

Explain the difference between gradient-echo and spin-echo sequences.

Answer 34

Gradient-echo sequences are faster and use gradient fields to refocus spins, while spin-echo sequences use a 180-degree RF pulse for refocusing, resulting in different image contrasts.

Question 35

How does diffusion-weighted imaging work, and what does it detect?

Answer 35

It measures the diffusion of water molecules in tissues, useful for detecting strokes and other abnormalities.

Question 36

What is the purpose of fat suppression techniques in MR imaging?

Answer 36

To reduce the bright signal from fat, improving the visibility of underlying tissues.

Question 37

Describe the concept of k-space in MRI.

Answer 37

K-space is a data storage space used to store raw MR signals before they are transformed into an image using Fourier transformation.

Question 38

What is susceptibility-weighted imaging (SWI), and when is it particularly useful?

Answer 38

An MRI technique that enhances the visibility of blood vessels and microhemorrhages, valuable in neuroimaging.

Question 39

What factors influence the selection of pulse sequences in MRI?

Answer 39

The desired contrast, resolution, speed, and specific diagnostic requirements.

Question 40

How does MR spectroscopy differ from traditional MRI?

Answer 40

It provides chemical composition data of tissues rather than anatomical images, useful for identifying metabolic changes.

Question 41

IN CLASS MINI-QUIZ QUESTION 1:

How is the tripartite subdivision of the STN defined?

Question 42

IN CLASS MINI-QUIZ QUESTION 2:

Provide one argument in favor of the tripartite subdivision hypothesis, and one against it.