MR glossary

Question 1

_____________ is a term describing the containment of the static magnetic field through the use of secondary coils attached around the MRI scanner.

Answer 1

Active shielding

Question 2

: ____________ is a term used to describe the adjustment of the current within the shim coils on a per patient or per sequence basis.

Answer 2

Active shimming

Question 3

3 : __________ are reconstructed from diffusion weighted images with multiple b-values, and corresponds to the spatially distributed diffusion coefficients of the target tissues

Answer 3

ADC images

Question 4

: ____________ occurs when tissue outside the Field of View is undersampled, causing a misregistration of anatomical location, in the phase direction, but on the opposite side of the anatomical location, also known as wrap-around artifact

Answer 4

Aliasing artifact

Question 5

The ____________ is part of the computer system that converts the analog acquired MR signal into a digital signal

Answer 5

Analog-to-digital converter (ADC)

Question 6

: An ________ comprises a multiprocessor that is switched in sequence and in parallel while simultaneously performing a computing task.

Answer 6

Array processor

Question 7

An _____________ is one that has uneven measurements, with regards to the phase, frequency and slice thickness dimensions.

Answer 7

Anisotropic voxel

Question 8

____________ are signal misrepresentations that do not correspond to the spatial location of the specific tissue imaged

Answer 8

Artifacts

Question 9

: _______________ is defined as the range or spectrum of frequencies (minimum to maximum processed frequency)of a pulse sequence acquired by an RF system.

Answer 9

Bandwidth

Question 10

The ____________ is an integrated part of the magnet design that acts as its own transceiver coil, with large FOV capabilities, but lacking the high SNR of localized coils

Answer 10

Body coil

Question 11

The __________ is defined as a factor in diffusion weighted imaging; the higher the factor, the stronger the diffusion weighting.

Answer 11

B-value

Question 12

The ___________ is defined as the static main magnetic field of an MR system.

Answer 12

B0

Question 13

The __________ is the alternating magnetic field generated by the RF in a transceiver coil

Answer 13

B1

Question 14

_____________ prevents or reduces motion artifacts in an MR image caused by the beating heart or pulsating blood flow and enables the images to be acquired synchronized to movement

Answer 14

Cardiac triggering

Question 15

________________ is due to the difference in resonant frequencies between fat and water, causing a phase shift in voxels containing fat and water

Answer 15

Chemical shift artifact

Question 16

Describing image display, the ________ function scrolls through the entire sequence’s images, giving the appearance of CSF flowing or cardiac movement, from the cycle of the images acquired.

Answer 16

Cine

Question 17

: __________ can be defined as the signal strength differences between two adjacent tissue types.

Answer 17

Contrast

Question 18

_______________ utilizes the reduced T1 relaxation time of blood through the use of an intravenously injected Gadolinium contrast agent

Answer 18

CE MRA

Question 19

: _______________ occurs when slices are positioned too close together, causing signals from adjacent slices to affect one another

Answer 19

Cross talk artifact

Question 20

_________ occurs after initial RF application, causing phase differences to appear between precessing spins, resulting in decay of transverse magnetization

Answer 20

Dephasing

Question 21

: ___________ is an effect resulting in a slightly weakened magnetic field when a substance is introduced into it. This material is considered to have a negative magnetic susceptibility.

Answer 21

Diamagnetism

Question 22

An ________ is the MR signal generated by an RF or a gradient pulse

Answer 22

Echo

Question 23

: _________ is simply defined as the distance between echoes.

Answer 23

Echo spacing

Question 24

The time between the excitation pulse of a sequence and the resulting echo used as the MR signal is known as:

Answer 24

Echo time

Question 25

A technique used to suppress fluids, utilizing a long echo time coupled with a long Inversion time is known as \_\_\_\_\_\_\_\_\_\_.

Answer 25

FLAIR

Question 26

\_\_\_\_\_\_\_\_\_\_ materials, such as iron, contain unpaired electrons, each with a small magnetic field of its own, that align readily with each other in response to an external magnetic field.

Answer 26

Ferromagnetic

Question 27

The mathematical process of converting raw data into an image suitable for display is known as \_\_\_\_\_\_\_\_\_.

Answer 27

Fourier transform

Question 28

The angle to which the longitudinal magnetization is tipped into the transverse plane, following the initial RF excitation pulse, is known as \_\_\_\_\_\_\_\_.

Answer 28

Flip angle

Question 29

\_\_\_\_\_\_\_\_\_ is defined as the number of times that a periodic function or vibration repeats itself in a specified time. It is usually measured in hertz (Hz).

Answer 29

Frequency

Question 30

The timing the collection of MR data to physiological motion in order to minimize motion artifacts is known as:

Answer 30

Gating

Question 31

The linear increased or decreased change in the magnetic field of a certain orientation is defined as a \_\_\_\_\_

Answer 31

Gradient

Question 32

: ________ is defined as the ratio of the magnetic moment (field strength) of a rotating charged particle, such as an electron, to its angular momentum (frequency).

Answer 32

Gyromagnetic ratio

Question 33

What is the term for the echo generated by switching a pair of dephasing and rephasing gradients, without the use of a 180° refocusing pulse?

Answer 33

Gradient echo

Question 34

An MR sequence that begins with 180º RF inverting pulse followed by 90º RF excitation pulse, then 180º RF refocusing pulse is known as

Answer 34

: Inversion recovery

Question 35

: _________ is known as the specific frequency at which magnetic resonance in a nucleus can be excited and detected, and varies directly with magnetic field strength.

Answer 35

Larmor frequency

Question 36

\_\_\_\_\_\_\_\_\_ is the magnetic and thermal environment through which nuclei exchange energy in longitudinal (T1) relaxation

Answer 36

Lattice

Question 37

\_\_\_\_\_\_\_\_\_\_\_ is defined as the Z component of the net magnetization vector in the direction of the static magnetic field

Answer 37

Longitudinal magnetization

Question 38

MR technique utilized to image flowing blood and specific vasculature structures

Answer 38

Magnetic resonance angiography (MRA)

Question 39

MR technique which quantitatively assesses the mechanical properties of tissues, based on the propagation of shear waves:

Answer 39

Magnetic resonance elastography (MRE)

Question 40

MR technique generating a spectrum of metabolites in a specific volume of interest:

Answer 40

Magnetic resonance spectroscopy (MRS)

Question 41

\_\_\_\_\_\_\_\_\_\_ is defined as the magnitude and direction of the magnetization resulting from the collection of atomic nuclei.

Answer 41

: Net magnetization vector

Question 42

What is an uncharged neutral particle located in the nucleus of most atoms which serves as a stabilizer?

Answer 42

Neutron

Question 43

: _________ is defined as a loss of resolution due to excessively large voxels, typically caused by slices that are too thick

Answer 43

Partial volume averaging

Question 44

An artificial object that can be imaged to test the performance and quality of a magnetic resonance system would be

Answer 44

Phantom

Question 45

\_\_\_\_\_\_\_\_ is comprised of the components of the magnetization in the imaging object after excitation, sampled from the receiver coil signal and stored as a function of time during the data acquisition of an MR imaging sequence

Answer 45

Raw data

Question 46

\_\_\_\_\_\_\_\_\_ gradient – magnetic field gradient applied during the moment when the echo is formed

Answer 46

Readout

Question 47

\_\_\_\_\_\_\_\_\_ is defined as an event in a superconducting MR system causing a loss of superconductivity, a rapid loss of the magnet cryogens

Answer 47

Quench

Question 48

Short TI Inversion Recovery: a version of the Inversion Recovery pulse sequence where the inversion time (TI) is set to ______ times the T1 of fat, nulling the signal from fat at the specific field strength in which it’s being acquired

Answer 48

0.69

Question 49

MRA technique relying on flow related enhancement to distinguish between stationary spins and flowing spins:

Answer 49

Time of flight

Question 50

\_\_\_\_\_\_\_\_\_ is defined as a volume element with 3-Dimensional characteristics

Answer 50

Voxel