Magnetic Resonance Imaging (MRI) Overview

<p>Time-varying magnetic field gradients (D)</p> Signup and view all the answers

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

<p>Their net spin (D)</p> Signup and view all the answers

<p>It is the most abundant in human tissue (C)</p> Signup and view all the answers

<p>Net Magnetisation Vector (B)</p> Signup and view all the answers

<p>There is a small excess of spin-up nuclei (A)</p> Signup and view all the answers

<p>It increases as field strength increases (B)</p> Signup and view all the answers

<p>4.5 per million (D)</p> Signup and view all the answers

<p>Some align parallel and some antiparallel (C)</p> Signup and view all the answers

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

<p>Transverse magnetisation decreases (D)</p> Signup and view all the answers

<p>Spin-Echo (B)</p> Signup and view all the answers

<p>To minimize T2 effects (B)</p> Signup and view all the answers

<p>Proton Density weighting (A)</p> Signup and view all the answers

<p>Common pathologies (A)</p> Signup and view all the answers

<p>Time to echo (TE) (D)</p> Signup and view all the answers

<p>T1 and T2 occur simultaneously (B)</p> Signup and view all the answers

<p>High signal may not indicate tissue health (D)</p> Signup and view all the answers

<p>Precessional pathway (B)</p> Signup and view all the answers

<p>Strength of the magnetic field (C)</p> Signup and view all the answers

<p>Flip of the net magnetization vector to 90 degrees (D)</p> Signup and view all the answers

<p>Longitudinal relaxation (T1 recovery) (D)</p> Signup and view all the answers

<p>It increases transverse magnetization (A)</p> Signup and view all the answers

<p>It decreases as nuclei lose coherence (B)</p> Signup and view all the answers

<p>Nuclei transitioning from being in phase to out of phase (A)</p> Signup and view all the answers

<p>Nuclei lose longitudinal magnetization (A)</p> Signup and view all the answers

<p>To generate fields of 0.5T or higher (B)</p> Signup and view all the answers

<p>They orientate the slice in three dimensions (D)</p> Signup and view all the answers

<p>To transmit an RF pulse and to receive signals from hydrogen nuclei (A)</p> Signup and view all the answers

<p>By causing loud noises due to magnetic field variations (D)</p> Signup and view all the answers

<p>Cryogenic cooling with liquid helium (B)</p> Signup and view all the answers

<p>To position the patient for the MRI scan (D)</p> Signup and view all the answers

<p>They are always active and generate strong magnetic fields (B)</p> Signup and view all the answers

<p>Caused by the gradient coils varying the magnetic field (A)</p> Signup and view all the answers

Atomic nuclei with a positive charge and a net spin.

The process where magnetically resonant nuclei align in a strong magnetic field.

The most abundant element in human tissue, making it ideal for MRI.

The random orientation of hydrogen nuclei, resulting in no net magnetic effect.

The alignment of hydrogen nuclei along the magnetic field lines.

The two possible orientations of hydrogen nuclei aligned with the magnetic field.

The rate at which a magnetic moment precesses (wobbles) around the magnetic field line.

The sum of all magnetic moments in aligned nuclei.

A magnetic field is generated around the moving charge.

A magnetic field is generated around the wire.

The magnetic field is concentrated and amplified.

The magnetic field is further amplified and becomes more uniform.

The strength of the magnetic field increases.

The magnetic field gets stronger and more concentrated.

A powerful magnet that operates at very low temperatures, typically using liquid helium to achieve superconductivity.

Sets of coils that create a gradient magnetic field, used to manipulate the spatial orientation of the MR signal, resulting in 3D images.

The precessing motion of a nucleus around the main magnetic field.

The phenomenon where an external force causes a system to vibrate with greater amplitude at specific frequencies.

The specific frequency at which a nucleus resonates.

The process of applying an RF pulse at the Larmor frequency to excite the nucleus, causing it to flip to the transverse plane.

The process of the nuclei returning to their aligned state with the main magnetic field after the RF pulse is turned off.

The process by which the magnetic moments of the nuclei realign with the main magnetic field, resulting in an excess of spin-up.

The process of the nuclei losing their in-phase precession, resulting in a decrease of signal strength.

A short TE (time to echo) minimizes T2 effects, resulting in increased signal intensity from tissues with a short T2 relaxation time.

A long TR (repetition time) allows for full T1 relaxation, resulting in increased signal intensity from tissues with a long T1 relaxation time.

A long TR and a short TE are used to obtain a proton density (PD) weighted image, where signal intensity is primarily determined by the number of protons in the tissue.

The ratio of the signal received from a tissue to the average noise level in the image.

A technique used to improve SNR by increasing the overall signal intensity, potentially by decreasing the TE or increasing the TR.

The process where protons in a magnetic field align themselves along the field lines, resulting in the creation of a strong magnetic field. This process is essential for forming an image in MRI.

The process where protons, initially aligned in the magnetic field, lose their alignment and begin to point in random directions, causing a decrease in the magnetic field strength. This is crucial for MRI imaging.

The time it takes for the longitudinal magnetization to recover to approximately 63% of its original strength after an RF pulse. Tissues with different T1 relaxation times appear different in T1-weighted MRI images.

The time it takes for the transverse magnetization to decay to approximately 37% of its original strength after an RF pulse. Different tissues have varying T2 relaxation times, impacting their appearance in T2-weighted images.

An MRI pulse sequence that uses two RF pulses to achieve a 'spin echo'. The first pulse excites the protons, and the second pulse brings them back into alignment, resulting in a measurable signal. It influences the tissue weighting by adjusting 'TE' and 'TR'.

An MRI pulse sequence that uses magnetic field gradients instead of a second RF pulse to bring the protons back into alignment, resulting in a signal. It gives more flexibility in controlling image weighting compared to Spin-Echo.

This image emphasizes tissues with faster T1 relaxation times, meaning they recover their longitudinal magnetization quickly. It uses short TE and short TR to enhance the signal.

This image highlights the differences in the T2 relaxation times of tissues. It utilizes long TE and long TR to emphasize tissues with slower T2 relaxation times, making them appear brighter.