MRI All in One Flashcards

Questions and Answers

What are the types of coils used in MRI?

Main magnet (correct)

Shim coils (correct)

RF coils (correct)

Gradient coils (correct)

What is gradient amplitude?

Defined as the strength of the gradient

What is gradient rise time?

Time it takes for the gradient to reach its full amplitude

What is gradient slew rate?

Speed rate of ascent or descent of a gradient from zero to its maximum amplitude Signup and view all the answers

Where is k-space physically located?

Array processor Signup and view all the answers

When ____ gradient slopes are applied, data gets mapped into the center of k-space.

shallow Signup and view all the answers

Data mapped in the _____ of k-space gets stored as spatial resolution.

periphery Signup and view all the answers

What must be performed on raw data for it to be stored in k-space?

Fast Fourier Transform (FFT) Signup and view all the answers

What principle enforces the reliable digitization of analogue signals?

Nyquist theorem Signup and view all the answers

In order to maintain resolution when applying multiplayer reconstruction, _____ voxels should be acquired during acquisition.

isotropic Signup and view all the answers

Area of free diffusion appears ____ on ADC maps.

bright Signup and view all the answers

What combination of TR and TE would give the greatest T1 image weighting?

Short TR and short TE Signup and view all the answers

What combination of TR and TE would give the greater T2 image weighting?

Long TR and long TE Signup and view all the answers

TR is the parameter that represents the time between consecutive:

Excitation pulses Signup and view all the answers

What parameter is described as the time between the alpha pulse and the peak of the echo?

TE Signup and view all the answers

What parameter is only used in inversion recovery sequences to null the signal from specific tissues?

T1 Signup and view all the answers

The time of inversion takes place between _____ and the excitation pulse.

the 180 inversion pulse Signup and view all the answers

If the number of signal averages (NSA) is increased by a factor of 2, what happens to the signal to noise ratio (SNR)?

SNR increased by the square root of 2 or by a factor of 1.41 (41%) Signup and view all the answers

If the number of signal averages (NSA/NEX) is increased by a factor of 2, what happens to scan time?

Scan time doubles Signup and view all the answers

Decreasing the FOV from 180mm to 90mm will have what effect on SNR?

SNR decreases by a factor of 4 Signup and view all the answers

Which of the following factors influence slice thickness?

Slice select gradient slope Signup and view all the answers

To obtain thick slices, a __ slice select gradient slope and/or a transmit bandwidth is used.

shallow, broad Signup and view all the answers

What is the parameter that represents the range of frequencies sampled while the readout gradient is active?

Receive bandwidth Signup and view all the answers

If receive bandwidth is doubled, approx of SNR is __.

40%, lost Signup and view all the answers

Which of the following directly results as the phase matrix increases?

SNR decreases Signup and view all the answers

Study Notes

MRI Coil Composition

Four types of coils are crucial: RF coils, gradient coils, shim coils, and the main magnet.

Gradient Characteristics

Gradient amplitude indicates the strength of the gradient applied in MRI.
Gradient rise time measures how quickly the gradient reaches its maximum strength.
Gradient slew rate refers to the speed of transition from zero to maximum amplitude.

K-Space and Data Storage

K-space is physically located within an array processor.
Shallow gradient slopes lead to data being mapped to the center of k-space.
Data mapped to the periphery of k-space represents spatial resolution.

Data Processing and Transformation

Fast Fourier Transform (FFT) is necessary to convert raw data for storage in k-space.
Nyquist theorem ensures reliable digitization of analog signals.

Image Acquisition Principles

Isotropic voxels are required for maintaining resolution during multiplayer reconstruction.
Areas of free diffusion appear bright on ADC maps.

T1 and T2 Weighting

Short TR (Repetition Time) and short TE (Echo Time) maximize T1 image weighting.
Long TR and long TE enhance T2 image weighting.
TR defines the interval between consecutive excitation pulses.

Timing Parameters

TE represents the duration between the alpha excitation pulse and the echo peak.
T1 is specifically used in inversion recovery sequences to nullify signals from targeted tissues.

Inversion Pulse Details

The timing of the inversion occurs between the 180-degree inversion pulse and the excitation pulse.

Signal-to-Noise Ratio (SNR)

Increasing the number of signal averages (NSA) by a factor of 2 raises SNR by approximately 41% (factor of 1.41).
Doubling the NSA also results in the scan time doubling.
Decreasing the field of view (FOV) from 180mm to 90mm leads to a decrease in SNR by a factor of 4.

Slice Thickness Influences

Slice thickness is affected by slice select gradient slope and transmit bandwidth.
Thick slices require shallow slice select gradient slopes or broad transmit bandwidths.

Receive Bandwidth Insights

Receive bandwidth indicates the frequency range sampled during the active readout gradient.
Doubling the receive bandwidth results in approximately a 40% loss of SNR.

Phase Matrix Impact

Increasing the phase matrix directly results in a decrease in SNR.

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Description

Test your knowledge on MRI terminology with these comprehensive flashcards. This quiz covers essential concepts such as RF coils, gradient amplitude, and slew rates to help you enhance your understanding of MRI technology and its components.