Untitled Quiz

<p>It indicates neuronal activity through blood flow changes. (C), It measures differences in magnetic susceptibility between oxygenated and deoxygenated hemoglobin. (D)</p> Signup and view all the answers

<p>FLAIR suppresses fat to visualize normal tissues clearly. (D)</p> Signup and view all the answers

<p>To suppress signals from fat, allowing better visualization of lesions. (D)</p> Signup and view all the answers

<p>The Larmor frequency at different locations varies. (B)</p> Signup and view all the answers

<p>MRI typically offers better soft tissue contrast than CT. (B)</p> Signup and view all the answers

<p>The number of protons in any chemical element within the sample (C)</p> Signup and view all the answers

<p>The strength of the field becomes non-uniform (C)</p> Signup and view all the answers

<p>To flip the magnetization vectors to the other side of the transverse plane (D)</p> Signup and view all the answers

<p>Field inhomogeneity effects (D)</p> Signup and view all the answers

<p>It uses differences in the magnetic susceptibility of oxygenated and deoxygenated hemoglobin (A)</p> Signup and view all the answers

<p>T2 has no effect on the intensity of the recovered echo (A)</p> Signup and view all the answers

<p>Images rely on variations in temperature (A)</p> Signup and view all the answers

<p>They differ due to the influence of the x-gradient (D)</p> Signup and view all the answers

<p>The direction of the diffusion (C)</p> Signup and view all the answers

<p>In T1-weighted images, transverse magnetization rates are emphasized compared to longitudinal rates. (C)</p> Signup and view all the answers

<p>By applying a magnetic gradient orthogonal to the slice of interest (D)</p> Signup and view all the answers

<p>The observed signal in MRI is produced by longitudinal magnetization. (C)</p> Signup and view all the answers

<p>Phase encoding is generally used after slice selection and frequency encoding. (D)</p> Signup and view all the answers

<p>Proton density-weighted imaging (C)</p> Signup and view all the answers

<p>T1 emphasizes differences in the rate of longitudinal reformation. (A)</p> Signup and view all the answers

<p>Differences in magnetic resonance properties between solid and liquid phases (C)</p> Signup and view all the answers

<p>I, II, and III (C)</p> Signup and view all the answers

<p>Proton Density, T2, T1, Grey Matter, White Matter. (D)</p> Signup and view all the answers

<p>Nuclei with even atomic number have certain non-zero angular momentum. (C)</p> Signup and view all the answers

<p>T2* relaxation is shorter due to spin-spin relaxation and field inhomogeneity. (C)</p> Signup and view all the answers

<p>It rotates vector M to the negative z-axis. (B)</p> Signup and view all the answers

<p>It is influenced by magnetic field inhomogeneity. (C)</p> Signup and view all the answers

<p>It reduces T1 or T2 relaxation times of protons nearby. (C)</p> Signup and view all the answers

<p>T1 and T2 values vary between different tissue types. (D)</p> Signup and view all the answers

<p>It has a longer T 2∗ and produces a stronger signal. (B)</p> Signup and view all the answers

<p>The gradient field makes the overall magnetic field uniform. (D)</p> Signup and view all the answers

<p>Only hydrogen can be imaged using MRI. (C)</p> Signup and view all the answers

<p>Magnetic field inhomogeneity (C), Spin-spin relaxation (D)</p> Signup and view all the answers

<p>By applying a linear magnetic gradient limiting RF interaction to specific Larmor frequencies. (A)</p> Signup and view all the answers

<p>To minimize the effects of gradient field non-uniformity. (B)</p> Signup and view all the answers

<p>Different T1 and T2 values for tissues (D)</p> Signup and view all the answers

<p>They adjust the strength of the magnetic field. (D)</p> Signup and view all the answers

<p>The overall magnetic field strength varies depending on x-coordinates. (B)</p> Signup and view all the answers

<p>Using a larger z-gradient (A), Using a smaller RF bandwidth (C)</p> Signup and view all the answers

<p>Variations in local magnetic field strength. (B)</p> Signup and view all the answers

<p>They receive the MR signals, which vary in size. (C)</p> Signup and view all the answers

<p>Values in k-space are complex numbers. (C)</p> Signup and view all the answers

<p>Volume coils have uniform sensitivity patterns. (A)</p> Signup and view all the answers

<p>Thickens the slice selection. (D)</p> Signup and view all the answers

<p>Spatial encoding of the image data. (D)</p> Signup and view all the answers

Tensors in MRI allow analysis of the direction of diffusion in three dimensions, beyond just its magnitude, providing a more complete picture of water movement in tissues.

TR (repetition time) is the time between RF excitations, while TE (echo time) is the time between excitation and echo formation. TR is generally longer than TE.

In T1-weighted images, differences in the speed of longitudinal magnetization recovery are emphasized. Tissues with faster recovery appear brighter. This contrasts with T2-weighted images, which highlight differences in transverse magnetization dephasing rates.

In T2-weighted images, differences in the dephasing rates of the transverse magnetization are emphasized. Tissues with slower dephasing rates appear brighter.

These images obtain signals quickly after the RF pulse, before T2 effects decay the signal. The intensity is proportional to the number of hydrogen nuclei in the tissue.

Slice selection in MRI is achieved by applying a magnetic gradient orthogonal to the desired slice. This gradient manipulates the magnetic field strength across the tissue, allowing only the targeted slice to resonate with the RF pulse.

The signal observed in MRI is an RF signal produced by the rapidly rotating transverse magnetization of hydrogen nuclei. This signal is then processed to create an image.

The Larmor frequency of hydrogen varies slightly for different chemical environments, such as fat and water. This difference can lead to misalignment artifacts in the image, creating a 'chemical shift' effect.

Magnetic Resonance Angiography (MRA) uses different techniques to visualize blood flow. These include injecting contrast agents to alter signal intensity, detecting Doppler shifts in Larmor frequency, and using saturation techniques to highlight fresh blood entering a slice.

A contrast agent like gadolinium is injected into the bloodstream to reduce the T1 or T2 relaxation time of protons near blood vessels. This makes the blood vessels appear brighter in the image.

The Doppler effect is used in MRA to detect blood flow. The Larmor frequency of protons in moving blood shifts, allowing the direction and speed of blood flow to be measured.

This technique saturates the magnetization in a slice, so only fresh blood entering from outside the slice gives off a signal. This method doesn't require a contrast agent.

An MRI image that is primarily sensitive to the number of protons in a tissue. It shows the density of hydrogen atoms, which is roughly proportional to the water content.

Different MRI image sequences (T1-weighted, T2-weighted, Proton Density) are used to highlight specific tissue properties: T1 for fat and water, T2 for fluid and inflammation, and Proton Density for overall water content.

Images that emphasize the number of hydrogen nuclei in a tissue. They have the highest signal-to-noise ratio, especially with a π/2 tip angle.

A common contrast agent used in MRI. It enhances the visibility of specific tissues by altering their magnetic properties.

A magnetic field gradient applied in a specific direction (e.g., x-gradient) that varies the magnetic field strength along that direction. This helps to differentiate between different locations in the tissue.

A type of MRI sequence used to suppress fat signal, which can be helpful in visualizing other structures (e.g., tumors) that are not obscured by fat.

An MRI sequence designed to suppress watery fluids like CSF, allowing for clearer visualization of brain structures and lesions.

MRI is better for imaging soft tissues, while CT is better for imaging bones. MRI does not use ionizing radiation, while CT does.

MRI is generally more expensive than CT.

A non-uniform magnetic field applied to a sample. This gradient increases or decreases the field strength along a specific direction (e.g., x, y, or z).

The specific frequency at which a nucleus spins and precesses in a magnetic field. This frequency varies depending on the strength of the field and the type of nucleus.

An MRI pulse sequence that employs a 180° RF pulse to refocus the spins and counteract the effects of T2* relaxation, which includes field inhomogeneity.

The decay of the transverse magnetization due to both spin-spin interactions (T2) and field inhomogeneity. This results in signal loss during the echo time.

Functional MRI technique utilizing differences in magnetic susceptibility between oxygenated and deoxygenated hemoglobin to detect neuronal activity.

The time it takes for the transverse magnetization of a sample to decay to 1/e of its initial value due to both spin-spin relaxation (T2) and inhomogeneity in the magnetic field.

A type of MRI that measures the diffusion of water molecules in the brain, revealing the direction and extent of white matter tracts.

A magnetic field that varies linearly along a specific direction (x, y, or z).

A strong magnetic field (B0) is used in MRI to align the protons of hydrogen atoms in the body, creating a measurable signal.

The gradient field allows for spatial encoding in MRI by creating a linear variation in the magnetic field strength along a specific direction (x, y, or z).

The chemical shift artifact in MRI arises because protons in different chemical environments (e.g., fat and water) have slightly different Larmor frequencies.

Only atoms with odd atomic numbers or odd mass numbers have a non-zero magnetic moment and can be used for MRI. This is why hydrogen is the most common nucleus used in MRI.

Slice selection in MRI is achieved by applying a linear magnetic gradient along the z-axis, which limits the interaction of the RF pulse to protons with a specific Larmor frequency, thus selecting a specific slice.

Different tissues have varying T1 and T2 relaxation times, leading to different signal intensities in MR images, enabling us to distinguish them.

These coils alter the magnetic field strength, creating gradients that help select specific slices and encode spatial location.

These coils emit and receive radio frequency pulses, used to excite and acquire signals from specific slices.

Type of RF coil that covers a large area, providing more uniform signal across the body.

Type of RF coil that targets specific areas, providing better sensitivity to those regions.

Achieved by applying a magnetic gradient perpendicular to the desired slice, enabling specific slices to resonate with the RF pulse

A wider sinc pulse produces a narrower band of frequencies, resulting in a thinner slice selection.

A frequency domain representation of MR data. Points in k-space correspond to different spatial frequencies, creating a representation of signal intensity in different spatial directions.