Lecture 3+4 AI generated

Question 1

Describe the basic physics of MRI.

Answer 1

MRI is based on nuclear magnetic resonance imaging. It involves a static magnetic field, radiofrequency pulses, and magnetic gradients to image hydrogen protons from water.

Question 2

Explain the differences between MRI and functional MRI.

Answer 2

MRI focuses on anatomy and structure, while functional MRI (fMRI) measures brain activity by detecting changes in blood flow.

Question 3

Identify and describe the major steps in fMRI data analysis.

Answer 3

The major steps in fMRI data analysis include preprocessing, statistical analysis, and interpretation of results.

Question 4

Define EEG and fMRI.

Answer 4

EEG (Electroencephalography) measures electrical activity in the brain, while fMRI (functional Magnetic Resonance Imaging) measures brain activity by detecting changes in blood flow.

Question 5

How do different types of design for fMRI experiments differ (blocked, event-related, parametric)?

Answer 5

Blocked design involves grouping stimuli together, event-related design presents stimuli randomly, and parametric design varies stimulus intensity to study brain response.

Question 6

Describe the pros and cons of fMRI compared to other neuroimaging techniques like EEG.

Answer 6

fMRI provides detailed spatial information but has lower temporal resolution compared to EEG, which offers high temporal resolution but lower spatial detail.

Question 7

Explain the concept of net magnetization in MRI.

Answer 7

In MRI, the magnetic field causes hydrogen protons to align in parallel or anti-parallel states, resulting in net magnetization in the direction of the magnetic field.

Question 8

What are the basic ingredients for MRI?

Answer 8

The basic ingredients for MRI include a static magnetic field (Tesla), radiofrequency pulses (RF), and magnetic gradients (mT).

Question 9

Do accidents related to MRI usually involve the magnet?

Answer 9

Yes, accidents related to MRI often have something to do with the magnet since it is always on and extremely powerful.

Question 10

Describe the process of excitation in MRI.

Answer 10

Excitation in MRI involves applying energy at the resonant frequency to nuclei, causing some to transition from low-energy to high-energy states, converting longitudinal magnetization into transverse magnetization.

Question 11

What is the role of net magnetization in MRI signal generation?

Answer 11

Net magnetization, resulting from more nuclei in the low-energy state, contributes to the generation of the MR signal parallel to the magnetic field.

Question 12

Define nuclear magnetic resonance (NMR) property in the context of MRI.

Answer 12

Nuclear magnetic resonance (NMR) property refers to the requirement for a nucleus to have both a magnetic moment and an angular momentum to be useful for MRI.

Question 13

How does relaxation in MRI involve the longitudinal and transverse magnetization?

Answer 13

Relaxation in MRI includes the recovery of longitudinal magnetization and the decay of transverse magnetization, which are key processes influencing image formation.

Question 14

Describe the concept of reception in MRI signal processing.

Answer 14

Reception in MRI refers to the recording of the MR signal data that contributes to the formation of images.

Question 15

What is the significance of the resonant frequency in MRI excitation?

Answer 15

The resonant frequency in MRI excitation is crucial as it allows low-energy nuclei to absorb energy and transition to high-energy states, facilitating the conversion of longitudinal to transverse magnetization.

Question 16

Describe the process of making an image using MRI technology.

Answer 16

To make an image using MRI, spatial coding is required. Gradients are applied to create different signals in the scanner, with extra magnetic fields causing variations in signal strength. By applying gradients in the Z-, X-, and Y-directions, an image of the body can be generated.

Question 17

What is the purpose of applying gradients in MRI imaging?

Answer 17

Gradients are applied in MRI imaging to create spatial variations in the magnetic field strength, allowing for the differentiation of signals from different locations in the scanner.

Question 18

Define frequency encoding in MRI imaging.

Answer 18

Frequency encoding in MRI imaging involves applying a gradient along the z-axis to cause a difference in Larmor frequency along the gradient. This allows the RF pulse to energize specific parts matching the Larmor Frequency, known as a slice.

Question 19

How does phase encoding work in MRI imaging?

Answer 19

Phase encoding in MRI imaging involves adding a gradient pulse to alter the phase of spins, enabling differentiation between signals from various directions. This process contributes to the creation of the final image.

Question 20

Describe the difference between MRI and functional MRI (fMRI).

Answer 20

MRI focuses on studying brain anatomy through detailed 3D imaging, while fMRI examines brain function by capturing 3D images over time. fMRI relies on the BOLD signal to detect changes in blood oxygen levels related to neural activity.

Question 21

What is the significance of Blood Oxygenation Level-Dependent (BOLD) signal in fMRI?

Answer 21

The BOLD signal in fMRI indicates changes in blood oxygen levels due to neural activity. An increase in neural activity leads to increased blood oxygen, which is reflected in the fMRI signal, allowing for the study of brain function.

Question 22

Explain the role of TR and TE in MRI imaging.

Answer 22

TR (repetition time) is the time between repeating the excitation process, while TE (echo time) is the time between transmitting the RF pulse and listening to the RF emission. TR and TE influence imaging contrast by affecting relaxation times of different tissues.

Question 23

What is the main disadvantage of MRI scans?

Answer 23

One of the main disadvantages of MRI scans is the noise generated during imaging, primarily caused by the switching of gradients. This noise can be disruptive and uncomfortable for patients undergoing MRI procedures.

Question 24

Describe the pros of using fMRI.

Answer 24

Non-invasive method to study the ‘brain in action’, repeated measures possible, reveals adaptive reorganization in the brain, shows functional connectivity between brain regions.

Question 25

What are the cons of using fMRI?

Answer 25

BOLD signal is an indirect measure of neuronal activity, BOLD response is slow with low temporal resolution, task design is crucial and not naturalistic, scan environment and magnetic field pose restrictions, relatively expensive and time-consuming.

Question 26

How can fMRI data be sensibly interpreted?

Answer 26

By contrasting neuronal activity of interest with a suitable baseline or control condition.

Question 27

Define cognitive subtraction in fMRI experiments.

Answer 27

Testing for differences in BOLD signal between conditions by alternating experimental events with control events to isolate the cognitive process of interest.

Question 28

Describe the basic design of blocked fMRI experiments.

Answer 28

Alternating blocks with ‘on’ and ‘off’ stimuli to maximize detection power and simplify implementation.

Question 29

What are the pros of using blocked fMRI designs?

Answer 29

Maximum detection power for localization, simple and easy to implement.

Question 30

What are the cons of blocked fMRI designs?

Answer 30

Poor estimation power for determining time course, inability to mix trial types within blocks, potential habituation, and some events cannot be blocked.

Question 31

Explain the importance of fMRI task design.

Answer 31

It is necessary to contrast neuronal activity of interest with a suitable baseline or control condition to interpret BOLD fMRI data sensibly.

Question 32

Describe the characteristics of rapid-related designs in fMRI studies.

Answer 32

Rapid event-related designs involve short inter-stimulus intervals, brief discrete events, and temporally jittered trials to prevent habituation.

Question 33

What is parametric modulation in fMRI studies?

Answer 33

Parametric modulation involves varying variables of interest over trials in blocks to examine how brain activation co-varies with these variables.

Question 34

Define perfusion fMRI and its process.

Answer 34

Perfusion fMRI involves measuring brain perfusion non-invasively by labeling protons in arterial blood magnetically to calculate cerebral blood flow.

Question 35

How does arterial spin labeling fMRI work?

Answer 35

Arterial spin labeling fMRI labels protons in arterial blood magnetically, acquires labeled images, then subtracts them from control images to measure cerebral blood flow.

Question 36

Describe the advantages of arterial spin labeling fMRI.

Answer 36

Arterial spin labeling fMRI allows for non-invasive measurement of brain perfusion, provides a reasonable estimate of regional cerebral blood flow, and is well-suited for detecting changes in brain activity.

Question 37

What are the disadvantages of rapid event-related designs in fMRI studies?

Answer 37

Disadvantages of rapid event-related designs include dependence on linearity assumption, limited single trial classification, and potential challenges in maintaining trial order consistency.