Neuroimaging Methods - Eppp Knowledge

1. Which functional method has the best temporal resolution for neural activity: EEG or fMRI?

   EEG (millisecond range). EEG captures rapid electrical fluctuations from neural populations, offering temporal precision far superior to fMRI's hemodynamic delays.

2. Which imaging method is best for detecting acute ischemic stroke early: CT or diffusion MRI?

   Diffusion-weighted MRI (DWI). DWI identifies restricted water diffusion in ischemic tissue within minutes, providing earlier and more sensitive detection than CT's density changes.

3. What does structural MRI primarily measure to create anatomical images?

   Differences in tissue properties (especially water content) via magnetic resonance. MRI exploits variations in proton relaxation times, influenced by water content and tissue composition, to generate high-contrast anatomical images.

4. Which method is most appropriate to study task-related language lateralization pre-surgery: fMRI or CT?

   fMRI. fMRI maps activation during language tasks to determine hemispheric dominance, guiding surgical planning unlike CT's anatomical focus.

5. Which functional imaging method uses radiotracers to estimate regional cerebral blood flow?

   SPECT (single-photon emission computed tomography). SPECT employs gamma-emitting tracers to map perfusion patterns, indicating functional activity through blood flow distribution in brain tissue.

6. Which method provides a structural measure of cortical thickness and gray-matter volume?

   Structural MRI morphometry (e.g., voxel-based morphometry). Morphometric techniques analyze MRI data to quantify regional brain volume and thickness, enabling detection of atrophy or developmental abnormalities.

7. What does the BOLD fMRI signal reflect most directly?

   Changes in blood oxygenation secondary to neural activity (hemodynamic response). BOLD signals arise from increased blood flow and oxygenation in active brain regions, correlating with but lagging behind neuronal firing.

8. Identify the best method to measure millisecond-level auditory evoked responses in the cortex.

   EEG (event-related potentials) or MEG; EEG is most common. EEG and MEG capture time-locked evoked potentials with millisecond precision, with EEG's accessibility making it standard for auditory neuroscience studies.

9. Which functional imaging method uses radiotracers to measure glucose metabolism?

   FDG-PET (positron emission tomography). FDG-PET tracks fluorodeoxyglucose uptake, reflecting metabolic rates in active brain regions as a proxy for neuronal energy demand.

10. Which functional method is most commonly used to localize seizure foci noninvasively?

    EEG (and sometimes MEG for source localization). EEG identifies abnormal electrical patterns during seizures, with MEG enhancing localization by modeling magnetic sources in epileptic networks.

11. Which is generally higher sensitivity for functional imaging: PET or fMRI?

    PET is highly sensitive to molecular targets; fMRI is sensitive to hemodynamics. PET detects radioligands at nanomolar concentrations for specific molecular imaging, offering greater sensitivity than fMRI's hemodynamic-based detection.

12. What is the key limitation of fMRI for timing of neural events?

    Poor temporal resolution due to delayed hemodynamic response. The BOLD response peaks seconds after neural events, limiting fMRI's ability to resolve rapid temporal sequences in brain processing.

13. What is the primary application of DTI in neuropsychology and neurology?

    Assessing white-matter tracts and connectivity (e.g., demyelination, TBI). DTI quantifies diffusion directionality to map white-matter pathways, aiding diagnosis of conditions disrupting tract connectivity like multiple sclerosis or trauma.

14. What is the main clinical advantage of CT compared with MRI in acute settings?

    Faster and better for acute hemorrhage and bone. CT scans are quicker to acquire and excel at detecting acute blood and bony structures, making them preferable in time-sensitive emergencies.

15. Identify the best imaging choice to rule out intracranial hemorrhage rapidly in the emergency department.

    Noncontrast CT head. Noncontrast CT rapidly visualizes hyperdense blood in hemorrhages without contrast risks, making it the initial choice in acute trauma evaluations.

16. Which structural method is most sensitive to white-matter microstructure and diffusion directionality?

    Diffusion tensor imaging (DTI). DTI tracks water molecule diffusion anisotropy in white matter, revealing fiber tract integrity and orientation not visible in standard MRI.

17. Which imaging method is most appropriate to assess amyloid or dopamine receptor binding in vivo?

    PET with an appropriate molecular radioligand. PET uses targeted radioligands to quantify protein binding in living brains, enabling in vivo molecular pathology assessment not possible with other methods.

18. Which functional method measures magnetic fields produced by neural currents?

    Magnetoencephalography (MEG). MEG detects weak magnetic fields from intracellular currents, offering non-invasive insights into neural dynamics with minimal signal distortion.

19. Which is generally higher spatial resolution for functional imaging: PET or SPECT?

    PET (generally higher spatial resolution than SPECT). PET's coincidence detection of positron emissions yields sharper images and better resolution than SPECT's single-photon approach.

20. Which method has the best spatial resolution for functional localization: fMRI or EEG?

    fMRI. fMRI achieves millimeter-scale precision in localizing activity, surpassing EEG's coarser spatial accuracy due to signal dispersion at the scalp.

21. Which functional imaging method directly measures postsynaptic electrical potentials at the scalp?

    Electroencephalography (EEG). EEG records summed electrical fields from pyramidal neuron postsynaptic potentials, providing direct, real-time indices of cortical activity.

22. Which neuroimaging method is best for high-resolution brain anatomy: CT or MRI?

    MRI. MRI provides superior soft-tissue contrast and resolution for detailed brain anatomy compared to CT's limitations in differentiating gray and white matter.

23. Which functional imaging method measures blood-oxygen-level-dependent signal changes?

    Functional MRI (fMRI), BOLD signal. fMRI detects BOLD contrasts from deoxyhemoglobin changes, providing indirect measures of neural activity through hemodynamic responses.

24. Which imaging method uses ionizing radiation: MRI or CT?

    CT uses ionizing radiation; MRI does not. CT relies on X-rays, which involve ionizing radiation, whereas MRI uses magnetic fields and radiofrequency pulses without radiation exposure.

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