Electromagnetic Spectrum and MRI Fundamentals

These flashcards cover key vocabulary terms related to the electromagnetic spectrum and MRI principles and techniques.

Electromagnetic Spectrum

The range of all electromagnetic radiation frequencies, including visible light, radio waves, and X-rays.

MRI RF (Radiofrequency)

Electromagnetic radiation used in MRI, typically from 1 to 100 MHz.

Tesla

The SI unit of magnetic field strength, also the name of an international unit used to measure magnetic strength.

Magnetism

A fundamental property of nature related to magnetic fields and forces from magnets or electric currents.

Nucleus

The central part of an atom, composed of protons and neutrons.

Spin Density

The concentration of hydrogen nuclei in tissue that contributes to the MRI signal.

T1 Relaxation Time

The time required for nuclear spins to align with the magnetic field after RF excitation.

T2 Relaxation Time

The time required for transverse magnetization to decay due to interactions between nuclear spins.

Free-Induction Decay (FID)

The signal emitted by tissue after being excited by an RF pulse in MRI.

Gradient Echo

A type of MRI technique that uses magnetic field gradients to create echoes without 180-degree refocusing pulses.

Fat Saturation (FATSAT)

A technique in MRI to reduce or eliminate the signal from fat protons to enhance the visibility of other tissues.

Dixon Method

An MRI technique that separates fat and water signals based on their chemical shift differences.

Fringe Field

The portion of the magnetic field extending from the MRI magnet that affects nearby equipment or personnel.

Spatial Resolution

The ability to distinguish between two closely spaced objects in an image, measured in line pair/mm.

Contrast Resolution

The ability of an imaging technique to differentiate between adjacent soft tissues.

Wave Function

A mathematical function that describes the behavior of quanta, determining the probability of finding a particle in a given state.

Aliasing

A phenomenon in MRI where an artificial wraparound image occurs due to misregistration of high-frequency components.

Voxel

A 3D volumetric portion of an image, whose viewing face is a pixel and depth is the third dimension.

Larmor Frequency

The frequency at which a magnetic moment precesses in a magnetic field, important for MRI signal generation.

Specific Absorption Rate (SAR)

The measure of power absorbed by tissue during RF irradiation in MRI.

Gating

A technique used to synchronize the imaging process with physiological cycles like the heartbeat to improve image quality.

Pulse Sequence

A series of radiowave pulses in MRI designed to excite nuclei for varying contributions to the signal.

Fourier Transform (FT)

A mathematical operation applied to MR signals to convert them from time domain to frequency domain.

Magnetic Moment

The tendency of an object to align itself with the external magnetic field, influenced by magnetic dipoles.

Gradient Magnetic Field

Changes in the intensity of a magnetic field in space, used in MRI for spatial encoding.

T1-weighted images

MRI images that provide good contrast between fat and water, highlighting fat deposition.

T2-weighted images

MRI images that differentiate based on T2 relaxation times, with water appearing lighter than fat.