Sequence Parameters and Options Flashcards
What is the most common data acquisition option in which a single line of K space is filled by data acquired from each slice before the TR period is repeated?
2D Imaging
What is a type of data acquisitioning option in which all data is acquired as volume with no space gap?
3D imaging
During 3D imaging, slice encoding occurs when?
Post data acquisiton
When data is acquired from each slice consecutively, one after the other is?
Sequential Slice Order
How much gap is needed to prevent image artifacts when acquiring slices sequentially?
at least 30% gap
When data is acquired from alternate slices through two separate acquisitions.
Interleaving slice order
What is typically not need to prevent image artifacts when using slice interleaving option?
Slice Gap
–Because Slice Interleaving DOES NOT acquire sequentially–
Spatial Saturation - (?)
Image option where a 90 degree RF pulse prior to the initial pulse in order to null the signal from user-specified AREAS OF UNWANTED ANATOMY.
Using an extra 90-degree RF pulse and _____, spatial saturation is able to saturate all other tissues in a specified area.
Broad Transmisson Bandwidth
The use of spatial saturation pulses will affect what 3 things?
Tissue Heating
SAR levels
Max # of slices available per acquisition
Gradient Moment Nulling (GMN) is..
Imaging option whose primary purpose is to compensate for flow within the image volume.
What type of flow is GMN most efficient at rephasing?
Laminar Flow (1st order flow)
When GMN is applied to axial images, which gradient is used for flow compensation?
Slice-Select Gradient
On Sagittal and Coronal images, which gradient is used when using GMN?
Frequency Encoding
What 3 things are true when using GMN?
It’s most effective using slow laminar flow.
It reduces intra-voxel dephasing.
It used the slice-select gradient or frequency encoding gradient to rephase flowing spins.
Which imaging option applies a 90 degree RF pulse prior to the initial pulse in order to null the signal from a specified tissue THROUGHOUT THE ENTIRE IMAGE VOLUME?
Chemical Supression.
Chemical Sat. pulse is capable of saturating tissues throughout the entire volume using an initial RF pulse of 90 degrees and what?
Narrow Transmission Bandwidth
A ___ is used to improve magnetic field homogeneity when using chemical suppression techniques.
Shim
When using chemical suppression, magnetic field homogeneity is crucial for ensuring that targeted hydrogen protons are precessing at ____________________
MATCHING the frequency created by the chemical saturation pulse.
What determines the time period between the 90 degree saturation pulse and the alpha pulse when applying the chemical sat. technique?
Sat TR
What equation is used to calculate the Sat TR needed when using chemical suppression?
TR / # of slices
Sat TR is usually represented by?
ms (milliseconds)
An imaging option used to track physiological motion so that the data acquisition can be properly timed for minimization of motion.
Physiological Gating/Triggering
The P wave of the cardiac cycle represents what?
Atrial Systole
The QRS wave of the cardiac cycle represents what?
Ventricular Systole
The T wave of the cardiac cycle represents what?
Ventricular Diastole
During MRI an increase of the amplitude of the T wave is commonly caused by -
Both magneto-HEMOdynamic and magneto-HYDROdynamic effects.
Which component of the QRS phase is of utmost importance?
R phase
The R phase represents what?
The PEAK of the QRS complex as well as the PEAK of ventricular contraction.
What is the time period between consecutive R phases known as?
R to R interval
The R to R interval during MRI is dependent on the patients what?
Heart Rate
When applying cardiac gating, what influences the TR?
Pt. Heart Rate
R to R interval
Desired Image Weighting
What is the equation to determine the length of one R to R interval?
60,000ms / BPM
The time period between R phases of the R to R interval is represented by what?
TR
R to R interval is measured in?
milliseconds (ms)
As a patient’s heart rate increase, the R to R interval ______
Shortens
If a pt. has a considerable high heart rate and only one R to R interval can be selected, a short TR CANNOT be used. (T/F)
False
During cardiac imaging, the period when the system stops acquiring data in order to detect the next R phase is called what?
Trigger Window (shown as a %)
The Trigger Window is used to help compensate for the fluctuations in pts. what?
Heart Rate
A trigger window of what percent is commonly used to compensate for heart rate fluctuations.
10-20%
The waiting period following each R phase is
Trigger Delay
A trigger delay of what (ms) is common in modern MR systems?
5-10ms
Extending the trigger delay is a technique sometimes used to image the heart during
Diastole
A form of physiological gating/triggering commonly used to prevent motion artifact from occurring due to blood flow within the extremities and CSF flow within the brain and spine.
Peripheral gating/triggering
During peripheral Gaiting/Triggering, motion is tracked using what device?
Pulse Ox
A respiratory bellow is a device that converts the ____ from breathing motion into a ___ that the MRI system can detect.
Mechanical Energy - Electrical Signal
a respiratory bellow uses a________________ to convert mechanical energy from breathing motion to electrical signal.
Transducer
A respiratory navigator echo tracks respiratory motion by monitoring ___ from within its prescribed ROI.
Signal Intensity
In phase imaging is achieved by selecting TE values in multiples of -
4.2ms
Using a rectangular FOV is an option that uses a -
Phase FOV SMALLER THAN the Frequency FOV.
The imaging option that increases the number of phase-encodings performed in the phase direction is?
Anti-Aliasing (over-sampling, no phase wrap, anti-fold over)
