Podcast
Questions and Answers
What are the types of coils used in MRI?
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?
What is gradient amplitude?
Defined as the strength of the gradient
What is gradient rise time?
What is gradient rise time?
Time it takes for the gradient to reach its full amplitude
What is gradient slew rate?
What is gradient slew rate?
Where is k-space physically located?
Where is k-space physically located?
When ____ gradient slopes are applied, data gets mapped into the center of k-space.
When ____ gradient slopes are applied, data gets mapped into the center of k-space.
Data mapped in the _____ of k-space gets stored as spatial resolution.
Data mapped in the _____ of k-space gets stored as spatial resolution.
What must be performed on raw data for it to be stored in k-space?
What must be performed on raw data for it to be stored in k-space?
What principle enforces the reliable digitization of analogue signals?
What principle enforces the reliable digitization of analogue signals?
In order to maintain resolution when applying multiplayer reconstruction, _____ voxels should be acquired during acquisition.
In order to maintain resolution when applying multiplayer reconstruction, _____ voxels should be acquired during acquisition.
Area of free diffusion appears ____ on ADC maps.
Area of free diffusion appears ____ on ADC maps.
What combination of TR and TE would give the greatest T1 image weighting?
What combination of TR and TE would give the greatest T1 image weighting?
What combination of TR and TE would give the greater T2 image weighting?
What combination of TR and TE would give the greater T2 image weighting?
TR is the parameter that represents the time between consecutive:
TR is the parameter that represents the time between consecutive:
What parameter is described as the time between the alpha pulse and the peak of the echo?
What parameter is described as the time between the alpha pulse and the peak of the echo?
What parameter is only used in inversion recovery sequences to null the signal from specific tissues?
What parameter is only used in inversion recovery sequences to null the signal from specific tissues?
The time of inversion takes place between _____ and the excitation pulse.
The time of inversion takes place between _____ and the excitation pulse.
If the number of signal averages (NSA) is increased by a factor of 2, what happens to the signal to noise ratio (SNR)?
If the number of signal averages (NSA) is increased by a factor of 2, what happens to the signal to noise ratio (SNR)?
If the number of signal averages (NSA/NEX) is increased by a factor of 2, what happens to scan time?
If the number of signal averages (NSA/NEX) is increased by a factor of 2, what happens to scan time?
Decreasing the FOV from 180mm to 90mm will have what effect on SNR?
Decreasing the FOV from 180mm to 90mm will have what effect on SNR?
Which of the following factors influence slice thickness?
Which of the following factors influence slice thickness?
To obtain thick slices, a ______ slice select gradient slope and/or a ____ transmit bandwidth is used.
To obtain thick slices, a ______ slice select gradient slope and/or a ____ transmit bandwidth is used.
What is the parameter that represents the range of frequencies sampled while the readout gradient is active?
What is the parameter that represents the range of frequencies sampled while the readout gradient is active?
If receive bandwidth is doubled, approx ____ of SNR is ______.
If receive bandwidth is doubled, approx ____ of SNR is ______.
Which of the following directly results as the phase matrix increases?
Which of the following directly results as the phase matrix increases?
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.
