MRI & subcortex ARTICLE (mini-quiz 4) Flashcards
Topographic organization of the human and non-human primate subthalamic nucleus & Advances in MRI-based computational neuroanatomy: from morphometry to in-vivo histology & MR Pulse Sequences: What Every Radiologist Wants to Know but Is Afraid to Ask
What does computational neuroanatomy aim to study through imaging?
Computational neuroanatomy quantifies brain structure dynamics in both healthy and clinical populations using imaging and computational models.
What imaging method is central to computational neuroanatomy, providing non-invasive structural insights?
Magnetic Resonance Imaging (MRI).
What new field has emerged from biophysical modeling of MRI data, allowing for brain histology in living subjects?
In-vivo histology using MRI (hMRI).
How does quantitative MRI (qMRI) improve neuroanatomical studies?
qMRI provides standardized, site-independent data, improving comparability across studies and longitudinal tracking.
Name two tissue characteristics measurable by qMRI that are significant for studying brain microstructure.
Myelin and iron content.
Which relaxation times in MRI (T1 and T2) are influenced by tissue microstructure and are markers for what component in brain tissue?
Both T1 and T2 relaxation times are influenced by myelin content in brain tissue.
What does Magnetization Transfer (MT) measure, and why is it useful in brain imaging?
MT measures the exchange of magnetization between macromolecules and water, useful for assessing myelin density.
How does diffusion imaging contribute to understanding brain microstructure?
Diffusion imaging reveals the microstructural organization by highlighting axonal properties and tissue density, providing insights into fiber tracts.
What parameter derived from MRI is sensitive to brain iron concentrations, aiding in studies of neurodegeneration?
Magnetic susceptibility.
What benefit does voxel-based morphometry (VBM) provide in MRI analysis?
VBM assesses differences in brain volume and tissue density across subjects, enabling studies on structural brain variations.
Why are T1 and MT mapping techniques valuable for cortical myelination studies?
These techniques allow for non-invasive mapping of myelin content, enabling the delineation of cortical areas based on myelination.
How does high spatial resolution improve qMRI-based computational neuroanatomy?
High spatial resolution enables detailed mapping of small brain structures and layers, increasing accuracy in identifying microstructural variations.
Describe the “g-ratio” and its significance in MRI-based studies.
The g-ratio is the ratio of the inner axonal diameter to the total axon diameter, indicative of myelination efficiency and axonal conductance speed.
Which type of MRI model integrates multiple qMRI parameters to estimate tissue features like myelin density and axonal properties?
Multi-compartment models.
How does susceptibility-based imaging differ from other MRI modalities in detecting microstructure?
It detects magnetic susceptibility variations caused by iron or myelin, aiding in distinguishing calcifications from blood deposits.
What are potential clinical applications of hMRI in neurodegenerative diseases?
hMRI can detect early microstructural changes, aiding in the diagnosis and monitoring of diseases like multiple sclerosis and Alzheimer’s.
Why is standardized MRI important in large-scale neuroimaging studies?
It ensures consistency and comparability across different sites and time points, enabling robust multi-center and longitudinal studies.
How does qMRI support research on age-related brain changes?
qMRI reveals patterns of microstructural changes, such as demyelination or iron accumulation, that correlate with aging.
What does effective proton density (PD) mapping contribute to in MRI?*
PD* mapping aids in differentiating tissue classes and improving segmentation in morphometric analyses.
Which techniques are used to compensate for motion artifacts in MRI-based studies of neuroanatomy?
Techniques like prospective motion correction and adaptive de-noising.
What is the primary purpose of MR pulse sequences in MRI technology?
To manipulate and control the timing of radiofrequency pulses and gradients for optimal image acquisition.
What are the basic components involved in an MR pulse sequence?
Radiofrequency pulses, gradients, and data acquisition windows.
Explain the significance of the TR (Repetition Time) and TE (Echo Time) in MR imaging.
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.
What does the term ‘flip angle’ refer to in MR imaging?
The angle to which the net magnetization vector is tilted away from the magnetic field direction.
What is a ‘spin echo’ in MRI?
A sequence that uses a 180-degree RF pulse to refocus dephased spins and generate a stronger signal.
What is T1-weighted imaging, and what kind of information does it provide?
An imaging sequence that highlights tissues with short T1 times, like fat, to produce high-contrast images of anatomical structure.
Describe the concept of T2-weighted imaging.
T2-weighted imaging emphasizes tissues with longer T2 relaxation times, often used to highlight differences between water and fat content.
What role does the gradient echo play in MR imaging?
It provides a fast imaging technique that uses variable flip angles, making it useful for dynamic studies.
What are inversion recovery sequences used for?
To null the signal from certain tissues, such as fat or fluid, to enhance contrast.
To null the signal from certain tissues, such as fat or fluid, to enhance contrast.
Fluid-Attenuated Inversion Recovery is used to suppress fluid signals in the brain to better visualize lesions.
Why is spatial resolution important in MRI, and how can it be optimized?
It determines the level of detail in the image and can be improved by adjusting the matrix size, field of view, and slice thickness.
What are the trade-offs between signal-to-noise ratio (SNR) and resolution in MR imaging?
Increasing resolution generally decreases SNR, which requires adjustments in acquisition parameters to optimize both.
What is the role of contrast agents in MR imaging?
To enhance the visibility of blood vessels, tumors, or other structures by altering the local magnetic environment.
Explain the difference between gradient-echo and spin-echo sequences.
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.
How does diffusion-weighted imaging work, and what does it detect?
It measures the diffusion of water molecules in tissues, useful for detecting strokes and other abnormalities.
What is the purpose of fat suppression techniques in MR imaging?
To reduce the bright signal from fat, improving the visibility of underlying tissues.
Describe the concept of k-space in MRI.
K-space is a data storage space used to store raw MR signals before they are transformed into an image using Fourier transformation.
What is susceptibility-weighted imaging (SWI), and when is it particularly useful?
An MRI technique that enhances the visibility of blood vessels and microhemorrhages, valuable in neuroimaging.
What factors influence the selection of pulse sequences in MRI?
The desired contrast, resolution, speed, and specific diagnostic requirements.
How does MR spectroscopy differ from traditional MRI?
It provides chemical composition data of tissues rather than anatomical images, useful for identifying metabolic changes.
IN CLASS MINI-QUIZ QUESTION 1:
How is the tripartite subdivision of the STN defined?
IN CLASS MINI-QUIZ QUESTION 2:
Provide one argument in favor of the tripartite subdivision hypothesis, and one against it.
