Neuroimaging

1. What is neuroimaging?
   Neuroimaging encompasses various medical imaging techniques that allow visualization of the brain and its function. The main methods are MRI (magnetic resonance imaging) for structural and functional imaging, and PET (positron emission tomography) for observing molecular processes. It is essential in both research and clinical settings for diagnosing and monitoring neurological diseases.

2. What is the difference between functional and structural MRI?
    • Structural MRI provides detailed images of brain anatomy, such as volume and regional atrophy.
    • Functional MRI (fMRI) measures brain activity by detecting changes in blood flow related to neuronal activity, often at rest or during specific tasks, allowing the study of connectivity and the function of brain networks.

3. What is PET used for in neuroimaging?
   PET uses radioactive tracers to detect specific molecules in the brain. It enables visualization of biochemical processes such as glucose metabolism or the presence of pathological proteins (amyloid, tau). PET is particularly useful in diagnosing and tracking the progression of neurodegenerative diseases.

4. What is brain connectivity in neuroimaging?
   Brain connectivity refers to the structural and functional links between different brain regions. It can be studied using functional MRI, which analyzes synchronized activity between areas, or diffusion MRI, which maps white matter fibers connecting those regions. Understanding connectivity is crucial for exploring both normal and pathological brain function.

5. What is diffusion MRI and what is it used for?
   Diffusion MRI measures the movement of water molecules in brain tissue, enabling visualization of white matter fibers. This technique reveals structural connectivity in the brain and is particularly useful in studying neurological disorders affecting nerve pathways, such as demyelinating diseases or brain injuries.

6. How is neuroimaging evolving with artificial intelligence?
   Artificial intelligence enables faster and more accurate analysis of large-scale neuroimaging data. It helps detect subtle patterns, improves diagnosis and prediction of disease progression, and paves the way for personalized medicine by integrating clinical and biological data.

7. What is neuroimaging in Alzheimer’s disease?
   Neuroimaging includes brain imaging techniques like MRI and PET that allow visualization of brain structure and function. It helps detect typical Alzheimer’s-related changes, such as hippocampal atrophy or the accumulation of pathological proteins (amyloid, tau), thereby supporting early diagnosis and disease monitoring.

8. How does neuroimaging aid in diagnosing neurodegenerative diseases?
   Neuroimaging detects characteristic brain abnormalities such as regional atrophy or accumulation of pathological proteins. These biomarkers support early diagnosis of diseases such as Alzheimer’s, Parkinson’s, or multiple sclerosis, and help distinguish between conditions for more tailored treatment.

9. What structural MRI markers are visible in Alzheimer’s disease?
   MRI reveals brain atrophy, particularly in the hippocampus and temporal cortex, which are heavily affected in Alzheimer’s. It can also show white matter hyperintensities (WMHs), often linked to vascular factors, and can help differentiate Alzheimer’s from other neurodegenerative disorders.

10. What is the role of amyloid and tau PET imaging in Alzheimer’s diagnosis and monitoring, including in cognitively normal individuals?
    Amyloid and tau PET are molecular imaging techniques used to better understand, diagnose, and monitor Alzheimer’s disease.

 • Amyloid PET visualizes the buildup of beta-amyloid plaques, an early hallmark of Alzheimer’s. It is useful both in cognitively impaired individuals to confirm amyloid pathology, and in cognitively normal individuals to detect risk before symptoms appear, making it a key tool for early diagnosis, longitudinal monitoring, and prevention trials.

 • Tau PET detects abnormal tau protein deposits, which are linked to clinical severity and cognitive decline. It provides crucial insight into disease progression and the extent of neurodegeneration.

11. What is the role of hippocampal subfields in early diagnosis of Alzheimer’s disease?
    Subregions of the hippocampus, such as CA1, are especially vulnerable in the early stages of the disease. Advanced imaging techniques have shown that fine-grained analysis of these subfields offers greater precision in detecting early stages than total hippocampal volume, thus enhancing preclinical diagnosis.

12. Is hippocampal atrophy a reliable marker for Alzheimer’s disease?
    Yes, hippocampal atrophy is a key marker for Alzheimer’s, as the hippocampus is one of the first regions affected. It is widely used in both clinical and research settings. However, it is not specific (also seen in other conditions) and not the earliest marker. It should be interpreted alongside other biomarkers (e.g., amyloid PET, CSF, cognitive testing) for a more accurate diagnosis.

13. Are white matter hyperintensities (WMHs) related to Alzheimer’s or normal aging?
    WMHs are common with aging. When mild and primarily frontal, they may be related to normal aging and are typically of vascular origin. However, when they are more extensive, particularly in posterior regions, they are often associated with Alzheimer’s disease and more pronounced cognitive decline.

14. Which TDP-43, tau, or neuroinflammation markers are visible in neuroimaging?

 • TDP-43 detection via neuroimaging is still limited, though PET tracers for this protein are under development.

 • Tau pathology, on the other hand, is well visualized using tau PET tracers like [18F]flortaucipir, [18F]MK6240, and [18F]PI2620, which bind to tau aggregates, especially in Alzheimer’s.

 • Neuroinflammation can be assessed using PET tracers targeting TSPO, such as [11C]PK11195, to evaluate microglial activation, a key indicator of brain inflammation.