BM402: Engineering in Medicine - MRI
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Questions and Answers

What does the BOLD technique in fMRI primarily measure?

  • Neuronal activity
  • Blood oxygen levels (correct)
  • Blood flow rate
  • Temperature changes in the brain

Which cellular structures are involved in providing oxygen to the brain's energy supply?

  • Dendrites
  • Glial cells
  • Neurons
  • Arteries, veins, and capillaries (correct)

What distinguishes the simplest fMRI task design mentioned?

  • Visualizing specific images
  • Listening to music while resting
  • Performing math problems
  • Eyes open versus eyes closed (correct)

What is referred to by ‘functional connectivity’ in the context of fMRI?

<p>Inter-regional correlations in neuronal variability (C)</p> Signup and view all the answers

The increase in cerebral blood flow (CBF) during visual stimulation is primarily seen in which brain area?

<p>Calcarine cortex (C)</p> Signup and view all the answers

Which of the following best describes the T2*-sensitive sequences used in fMRI?

<p>Sequences sensitive to blood oxygen variations (C)</p> Signup and view all the answers

In the historical context, what was Mosso's apparatus used for?

<p>Recording changes in brain volume (B)</p> Signup and view all the answers

What percentage of the brain's energy supply is accounted for by arteries, veins, and capillaries?

<p>20% (B)</p> Signup and view all the answers

What is the Larmor frequency in relation to a spin system?

<p>The natural precession frequency of the spin system (A)</p> Signup and view all the answers

How does a wider range of coverage in k-space impact image resolution?

<p>It results in higher spatial resolution with smaller voxels (B)</p> Signup and view all the answers

What information does the center of k-space provide?

<p>Low spatial-frequency information retaining most of the signal (C)</p> Signup and view all the answers

In the equation ω = γB, what does each variable represent?

<p>ω is the Larmor frequency, γ is the gyromagnetic ratio, B is the magnetic field strength (B)</p> Signup and view all the answers

What does the periphery of k-space provide in terms of image information?

<p>High spatial-frequency information contributing little signal (A)</p> Signup and view all the answers

What do basic sampling units differ between k-space and image space?

<p>Spatial frequency in k-space and distance in image space (B)</p> Signup and view all the answers

What does the Fourier Transform accomplish in the context of MRI?

<p>It transforms data from k-space into image space (A)</p> Signup and view all the answers

What is the role of the head coil in MRI focusing?

<p>To focus and enhance the magnetic field around the head (D)</p> Signup and view all the answers

What is primarily affected in Parkinson's disease?

<p>Movement (C)</p> Signup and view all the answers

In fMRI studies of Alzheimer's disease (AD), what is suggested by hyperactivity during memory trials?

<p>It indicates a compensatory strategy in early stages. (D)</p> Signup and view all the answers

What neuroimaging technique is sensitive to iron presence in the brain?

<p>T2-weighted imaging (D)</p> Signup and view all the answers

What may contribute to the loss of dopamine-producing neurons in Parkinson's disease?

<p>Iron overload (D)</p> Signup and view all the answers

What cognitive abilities were observed in at-risk patients during fMRI tasks in studies related to Alzheimer's disease?

<p>Hyperactivity despite potential cognitive impairment (B)</p> Signup and view all the answers

How do iron-rich structures appear on T2-weighted MRI images?

<p>Hypointense (dark) (D)</p> Signup and view all the answers

What effect does repeated exposure to jet lag have on salivary cortisol levels in cabin crew?

<p>Increased levels compared to short flights (A)</p> Signup and view all the answers

What hypothesis is suggested regarding high cortisol elevations and their effects?

<p>They induce hippocampal atrophy. (C)</p> Signup and view all the answers

What characterized the short-recovery group of flight attendants?

<p>Their recovery intervals were less than 5 days between flights. (D)</p> Signup and view all the answers

How many subjects were tested in each flight attendant group?

<p>10 subjects (B)</p> Signup and view all the answers

What is the primary measurement method mentioned for assessing brain activity?

<p>Electroencephalogram (EEG) (A)</p> Signup and view all the answers

What aspect of brain structure was examined in relation to jet lag?

<p>Temporal lobe volume (C)</p> Signup and view all the answers

Which group had recovery intervals of more than 14 days?

<p>Long-recovery group (C)</p> Signup and view all the answers

Which of the following best describes brainwaves?

<p>They are electrical patterns reflecting cortical activity. (D)</p> Signup and view all the answers

What was a key difference between the two flight attendant groups studied?

<p>The length of recovery periods between flights. (A)</p> Signup and view all the answers

Which term refers to the measurement of electrical patterns on the scalp?

<p>Electroencephalogram (C)</p> Signup and view all the answers

What are the primary functions of RF coils in an MRI system?

<p>To excite magnetization and receive signals. (C)</p> Signup and view all the answers

What ensures the homogeneity of the static magnetic field in MRI?

<p>Shimming coils (B)</p> Signup and view all the answers

Which of the following statements about T1 and T2 is correct?

<p>Both T1 and T2 are inherent properties fixed for specific tissues. (C)</p> Signup and view all the answers

Which component begins to recover after RF is turned off in MRI?

<p>Longitudinal magnetization (A)</p> Signup and view all the answers

What type of MRI images are produced by using short acquisition times?

<p>T1-weighted images (D)</p> Signup and view all the answers

Time to Echo (TE) refers to which aspect of MRI imaging?

<p>Time between RF pulse and echo signal receipt. (D)</p> Signup and view all the answers

Which property does T2* depend on in addition to tissue characteristics?

<p>Inhomogeneities in the magnetic field. (C)</p> Signup and view all the answers

What is the consequence of spins getting out of phase with each other in MRI?

<p>Decay of transverse magnetization. (B)</p> Signup and view all the answers

What is a primary cognitive domain affected by cognitive impairment?

<p>Language (C)</p> Signup and view all the answers

Which of the following is NOT a factor contributing to cognitive impairment?

<p>Increased social engagement (B)</p> Signup and view all the answers

What cognitive function is primarily associated with changes in the hippocampus?

<p>Memory processes (D)</p> Signup and view all the answers

Which symptom is characteristic of Alzheimer's disease?

<p>Memory loss, particularly of recent events (A)</p> Signup and view all the answers

Mild Cognitive Impairment (MCI) is best described as:

<p>An intermediate stage between normal aging and more serious cognitive issues (C)</p> Signup and view all the answers

Which of the following is a potential underlying cause of Mild Cognitive Impairment?

<p>Age-related changes (D)</p> Signup and view all the answers

Neurofibrillary tangles are associated with which condition?

<p>Alzheimer's disease (A)</p> Signup and view all the answers

What effect does impaired neurotransmission have on cognitive function?

<p>It leads to difficulties in cognitive processes (C)</p> Signup and view all the answers

Flashcards

Fourier Transform

A mathematical method to convert electrical current in a coil into an image.

Larmor frequency

The natural precession frequency of a spin system.

Larmor equation

ω = γB (omega = gyromagnetic ratio * magnetic field strength).

k-space

A representation of image data using spatial frequencies.

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Spatial Frequency

Frequency of spatial changes in an image.

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Image Space

Representation of images using distance measurements.

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High spatial resolution

Fine detail within an image.

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k-space and spatial resolution

A wider range of coverage in k-space corresponds to higher spatial resolution in image space, enabling smaller voxels.

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RF coils

Antennas in MRI that transmit and receive radio waves for exciting and detecting magnetization.

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Static magnetic field

A strong, stable magnetic field used to align atomic nuclei in the body for MRI.

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Gradient coils

Coils that create varying magnetic fields that spatially encode the signal in MRI.

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T1-weighted images

MRI images emphasizing differences in tissue relaxation times (T1).

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T2-weighted images

MRI images emphasizing differences in tissue relaxation times (T2).

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Time to Echo (TE)

Time between the RF pulse and the echo signal detection in MRI.

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T2* image

MRI image that shows signal variations due to inhomogeneities in the main magnetic field, especially useful in detecting blood products.

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Shimming coils

Coils that adjust the homogeneity of the static magnetic field for improved image quality in MRI.

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Functional MRI (fMRI)

A technique using T2*-sensitive sequences to measure brain activity by detecting changes in blood oxygenation level.

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BOLD (Blood Oxygen Level Dependent) technique

A method in fMRI that detects brain activity by measuring changes in blood oxygenation.

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T2*-sensitive sequences

MRI sequences used to measure changes in blood oxygenation.

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Primary visual cortex

Brain region that processes visual inputs, demonstrated in fMRI studies.

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Cerebral blood flow (CBF)

The rate of blood flow through the blood vessels in the brain.

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Eyes open/eyes closed task

A basic fMRI task design where changes in brain activity related to visual input are measured.

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Functional connectivity

Study of correlations among regions of the brain in spontaneous brain activity.

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Mosso's experiment

Early experiment demonstrating relationship between brain activity and blood flow using patients with skull defects.

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Cognitive Impairment

A range of difficulties with thinking skills, including things like remembering, paying attention, speaking, planning, and understanding visual information.

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Alzheimer's Disease (AD)

A brain disease that causes serious memory loss, trouble communicating, problems with reasoning, and mood changes.

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Mild Cognitive Impairment (MCI)

A stage between normal aging and more serious cognitive problems like dementia.

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Hippocampus

A brain region crucial for memory, especially forming new memories.

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Amyloid Plaques

Clumps of protein that build up in the brain, especially in Alzheimer's Disease.

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Neurofibrillary Tangles

Twisted fibers inside brain cells that can cause damage and death in Alzheimer's disease.

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Neuronal Loss

The death of brain cells, which occurs in various neurological conditions.

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Shrinkage of Brain Tissue

The brain's volume decreases due to cell death or damage, impacting its ability to function properly.

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fMRI Hyperactivity in AD

Increased brain activity observed in fMRI scans of individuals with early Alzheimer's disease (AD) during successful memory tasks.

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Iron Overload in Parkinson's

Excess iron accumulation in the brain, particularly in the substantia nigra, leading to a loss of dopamine-producing neurons.

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Substantia Nigra

Brain region severely affected in Parkinson's disease, responsible for dopamine production.

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Dopamine's Role in Movement

Neurotransmitter crucial for regulating smooth and coordinated movements. Its deficiency leads to Parkinson's symptoms.

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Jet Lag's Impact on Cortisol

Repeated jet lag significantly elevates salivary cortisol levels, potentially contributing to brain damage.

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Hippocampal Atrophy and Memory

High cortisol levels can damage the hippocampus, a brain region involved in learning and memory, leading to memory deficits.

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Cognitive Impairment in AD

Alzheimer's disease affects various cognitive abilities, including memory, attention, and language understanding.

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Jet lag's impact

Repeated jet lag can affect the volume of the temporal lobe and hippocampus, impacting memory performance.

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Temporal Lobe

A part of the brain responsible for memory, language, and some aspects of auditory perception.

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Jet Lag Recovery

The time it takes for the body's internal clock to adjust after a long flight across multiple time zones.

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EEG

Electroencephalogram, a test that measures electrical activity in the brain.

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Brainwaves

Patterns of electrical activity in the brain that are measured by EEG.

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Cortical Activity

The electrical activity generated by the brain's outer layer, the cortex, which is involved in complex thought processes.

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EEG Applications

EEG is used to diagnose sleep disorders, epilepsy, and to study brain activity during various mental states.

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Study Notes

BM402: Engineering in Medicine

  • Course name: Engineering in Medicine
  • Date: October 17, 2024
  • Location: M 2170 - South Campus

MRI

  • MRI type: Functional MRI
  • Applications: MRI and fMRI
  • Other imaging type: EEG
  • Applications: EEG
  • Other imaging type: Multimodal Imaging

Brain Imaging

  • Imaging techniques: X-Ray, CT, PET Scan, MRI, MRA
  • Specific MRI Anatomical Scan: Axial view, Sagittal view, Healthy volunteer, Siemens 3T MR Scanner

fMRI: Functional Scan

  • Functional network types: Primary visual, Lateral visual, Medial visual, Sensory-motor, Right lateral, Left lateral, Precuneus, Ventral stream, Medial temporal, Salience, Task positive, Auditory, Default mode
  • Z-score data: Veer et al. 2010

Magnetic Resonance Imaging: MRI

  • MRI scanner: Giant magnet
  • Magnet strength: Measured in Tesla (T)
  • Earth's magnetic field strength: ~0.00006 T
  • 3T MRI scanner strength: ~50,000 times stronger than Earth's field
  • Clinical MRI scanners: 1.5T or 3T
  • Research MRI scanners: 7T, 10.4T and 11.7T
  • Helium for cooling coils: ~35,000 liters required for 11.7T scanner

MRI: How it Works

  • Hydrogen protons in H2O molecules
  • Protons spin in a magnetic field
  • Precessional frequency: Rate of proton spin in a magnetic field
  • RF: Radio frequency pulse, tips protons away from B0 field
  • On Resonance: Protons have same frequency
  • Fourier Transform: Changes electrical current in a coil to create an image, relates the Larmor frequency.

MRI: Focusing Our Imaging

  • Magnetic field strength
  • White Matter
  • CSF
  • Grey Matter
  • Coil
  • Current

MRI: Image Formation (detailed)

  • Main Magnet
  • Coils (x, y, z gradient coils, rf receiver coil, rf transmitter (body) coil)
  • Patient table
  • RF pulse (90 degree rf pulse)
  • Gradient pulse (applied along z axis)
  • Fourier Transform (FT)

Fourier Transform

  • 2D Inverse Fast Fourier Transform (2D IFFT) converts from k-space to image space

Converting from k-space to image space

  • Image space: Basic sampling unit is distance
  • K-space: Basic sampling unit is spatial frequency (1/distance)
  • Wider k-space coverage: Higher spatial resolution in image space (smaller voxels)
  • Center of k-space (B): Low-spatial frequency info, retains most signal but not fine details
  • Periphery of k-space (C): High spatial-frequency info, finer details, contributes relatively little signal

First MR Image

  • 2003 Nobel Prize not for medical applications of MRI but development of imaging techniques
  • Early large-bore MRI scanner labeled "Indomitable" by Damadian et al. (1977)
  • The first image of a human body, subject Larry Minkoff

MRI Basics

  • Rabi used strong magnetic field to measure spin properties of nuclei
  • MRI scanners use strong magnetic field to induce changes in proton spin
  • Bloch detected nuclear induction
  • Lauterbur manipulated magnetic field strength creating image
  • MRI studies use magnetic gradients for image creation

MRI Hardware

  • Static magnetic field
  • Gradient coils
  • RF coils (Tx-Coil and Rx-Coil): excitation and signal reception
  • Shimming coils

MRI Image Contrast (T1, T2, T2*)

  • T1 and T2: Inherent to tissues (fixed for specific tissues at given magnetic field strength)
  • T2*: Depends on inhomogeneities in main magnetic field
  • T1-weighted images: Short acquisition times, white matter appears light
  • T2-weighted images: Longer times, gray matter appears bright
  • T2, T2*, Free Induction Decay (FID)

T2* and Functional MRI (fMRI)

  • BOLD (Blood Oxygen Level Dependent) technique: Image contrast based on deoxy- and oxy-hemoglobin levels in local brain
  • Deoxyhemoglobin: Paramagnetic, shortens T2 and T2* and decreases signal
  • Neural activity: Affects blood oxygen levels
  • Blood oxygenation changes: Changes in MR signal

Functional MRI – Task Design

  • Simplest task: eyes open and eyes closed
  • BOLD signal intensity differences in primary visual cortex observed.

Functional Connectivity

  • Correlations in spontaneous blood oxygen level dependent (BOLD) fluctuations
  • Examining inter-regional correlations in neuronal variability

Jetlag

  • Chronic 'jet lag' causes temporal lobe atrophy and spatial cognitive deficits
  • Repeated exposure to jet lag leads to reduced temporal lobe volume and deficits in spatial learning and memory
  • High cortisol associated with cognitive deficits
  • Cortisol levels higher in cabin crew with repeated jet lag compared to short distance flights

EEG Basics

  • Electro-encephalo-gram (EEG): Measurement of electrical patterns at the surface of the scalp, reflecting cortical activity
  • Electrical activity: Brainwaves (Delta, Theta, Alpha, Beta, Gamma)

EEG History

  • Hans Berger: Initial observations
  • Technology advances over time (EEG recording equipment, computer-aided signal processing)

EEG - Brain Rhythms

  • Different brainwave frequencies (Delta, Theta, Alpha, Beta, Gamma)
  • Associated with different brain functions and mental states

Electrocorticography

  • ECOG, IEEG
  • Intracortical microelectrodes: deep brain recording
  • Grid and stick electrodes: recording brain activity

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Description

Dive into the essential concepts of Engineering in Medicine with a focus on Magnetic Resonance Imaging (MRI) and its applications in brain imaging. This quiz explores various types of MRI, functionalities of fMRI, and comparisons with other imaging techniques like EEG and PET scans. Prepare to test your knowledge on the anatomical and functional aspects of MRI in a clinical and research context.

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