Upgrade to remove ads
Only $35.99/year

mri :)

Terms in this set (40)

In which of the following pulse sequences would you expect to find the shortest TR?
Gradient echo
In a Fast Spin Echo sequence, the effective TE are the echoes that are encoded:
With a low amplitude phase encoding gradient
In a Fast Spin Echo sequence, the effective TE are the echoes that are encoded with a low amplitude phase encoding gradient. This would occur at the line that is closest to the center of k-space (k0)
In a spin echo sequence, the time between the 90° RF pulse and the 180° RF pulse is known as the:
1/2 TE

In a spin echo sequence, the time between the 90° RF pulse and the 180° RF pulse is known as the 1/2 TE time.
Which RF pulse refocuses a decaying spin echo?
180°
As the TR is increased,
I. SNR is increased
II. Available number of slices is increased
III. T2 information is maximized
I and II only
In a spin echo pulse sequence, an echo is produced from:
A combination of two or more RF pulses
What specifically is a SPGR sequence spoiling?
Transverse magnetization
_________ is defined as the cause or origin of a disease.
Etiology
________ is defined as a decrease in the amount of oxygen in the body.
Hypoxia
An example of a parenteral method of drug delivery is taking a drug by mouth.
True/False
False
An intramuscular injection of Glucagon for an MR Enterography is an example of a parenteral method of drug delivery.
True/ False
True
If the repetition time is doubled, the scan time will:
Double
Which of the following would NOT compensate for the change in signal-to-noise as a result of decreasing the FOV?
Reducing the number of excitations
Which parameter will provide the better spatial resolution?
4mm slice thickness; 256 x 256 matrix
Reducing the number of lines filled in k-space will produce an image:
With a decrease in spatial resolution
Calculate the voxel volume for the following pulse sequence parameters: TR 450, TE 20, FOV 24cm, 320 x 320 matrix, 3mm slice thickness.
1.69mm3

To calculate voxel volume, first determine pixel area. FOV/matrix x FOV/matrix = pixel area. Pixel area x slice thickness = voxel volume. 240/320 x 240/320 = 0.5625 mm2. 0.5625 x 3 = 1.69mm3
Calculate the voxel volume for the following pulse sequence: TR 2000, TE 85, FOV 28cm, Matrix 272 x 320, 5mm slice thickness, 3 NSA.
4.55 mm3
Calculate the pixel area for the following sequence: TR 450, TE 12, FOV 18cm, 224 x 256 matrix, 4 NEX.
0.56 mm2

FOV/matrix x FOV/matrix = pixel area. 180/224 x 180/256 = 0.56 mm2
Calculate the pixel area for the following sequence: TR 4000, TE 120, FOV 28cm, 304 x 304 matrix, 2 NEX, ETL 12.
0.85 mm2

FOV/matrix x FOV/matrix = pixel area. 280/304 x 280/304 = 0.85 mm2.
Which of the following's primary biological effect is tissue heating/deposition?
Oscillating magnetic fields (radiofrequency)
The effects of time varying magnetic fields can include all of the following EXCEPT:
Warmth and/or increase in body temperature
The strength of the gradient over a specific distance is known as the:
Slew rate
What is wrong with a T2 weighted, fast spin echo image that has a 1.1 second TR and an 90 millisecond TE?
The TR does not sufficiently minimize the T1 weighted contrast
Enabling Driven Equilibrium will enable the operator to:
Reduce TR and preserve contrast
A proton density weighted image will have a repetition time (TR) in the range of:
1600 - 4000 ms
All of the following are properties of T2 weighting EXCEPT:
Flip angle controls contrast
Structures that will always appear black on an MR image include all of the following EXCEPT:
CSF
In an inversion recovery sequence, image contrast is controlled by:
In an inversion recovery sequence, image contrast is controlled by TR (repetition time), TE (echo time) and TI (inversion time)
A gradient echo sequence in which all the remaining residual transverse magnetization is removed prior to the next excitation pulse is known as:
Incoherent or spoiled
Gradient echo sequences requiring high signal from fluid are known as all of the following EXCEPT:
Incoherent gradient echo
Calculate the voxel volume for the following pulse sequence: TR 2000, TE 85, FOV 24cm, Matrix 272 x 320, 3mm slice thickness, 3 NSA.
1.98mm3
To calculate voxel volume, first determine pixel area. FOV/matrix x FOV/matrix = pixel area. Pixel area x slice thickness = voxel volume. 240/272 x 240/320 = 0.66 mm2 (pixel area). 0.66 x 3 = 1.98mm3
Phase contrast MRA techniques produce images in which the signal intensity within the vessel is dependent upon the:
Velocity of the flowing blood

The velocity or speed of the vessel(s) of interest determines the signal intensities in phase contrast MR angiography (PCA
Active shielding can be defined as:
Superconducting windings within the MR scanner, reducing the fringe magnetic field
: Magnetic field inhomogeneity is expressed in:
Parts per million
In an MRA sequence, the removal of signal from vessels is accomplished by:
Spatial presaturation
In order to generate thin slices, a ___________ is used
.I. Steep slice selection gradient
II. High amplitude slice select gradient
III. Low amplitude slice select gradient
IV. Narrow transmit bandwidth (tBW)
V. Wide transmit bandwidth (tBW)
VI. Narrow receiver bandwidth (rBW)
I, II and IV

A thin slice thickness is achieved through the utilization of a steep, high amplitude slice select gradient, and a narrow transmit bandwidth (tBW).
The receiver bandwidth (rBW) affects:
I. Signal-to-noise ratio (SNR)
II. Slice thickness
III. Chemical shift
IV. Spatial resolution
I and III only
The receiver bandwidth (rBW) affects the signal-to-noise ratio (SNR) in the image, but also has an effect on chemical shift (decreasing the receiver bandwidth increases chemical shift)
The B1 magnetic field is produced by a:
Radiofrequency coil
Reducing the FOV by a factor of 2 will reduce the voxel volume by a factor of:
4

Remember, the FOV is measured in phase and frequency dimensions, therefore reducing the FOV in half will reduce the phase AND frequency dimensions EACH by 2, for a total reduction of a factor of 4.
Calculate the available imaging time for a patient with a heart rate of 90 beats/min, trigger window 15% and trigger delay of 80ms.
487 ms

Heart Rate 90bpm, Trigger delay 50ms, Trigger window 10%, what is the available imaging time? 60000 ÷ 90 = 667ms. 667 - (100 <15% of 667> + 80 ---180) = 487 ms total available imaging time.
Verified questions
astronomy
Choose the best answer to given following. Explain your reasoning with one or more complete sentences.\ What do we conclude if a planet has few impact craters of any size?\ (a) The planet was never bombarded by asteroids or comets.\ (b) Its atmosphere stopped impactors of all sizes.\ (c) Other geological processes have wiped out craters
Verified answer
biology
Stretches of noncoding nucleotides found in RNA transcripts that interrupt coding sequences $$ \textbf{\ \ a.}\text{ exons.} $$ $$ \textbf{\ \ b.}\text{ codons.} $$ $$ \textbf{\ \ c.}\text{ anticodons.} $$ $$ \textbf{\ \ d.}\text{ introns.} $$
Verified answer
computer science
Show the FSM for an imaginary machine with three states: A (starting state),B, and C; and four events: events 1, 2, 3, and 4. The following specify the behavior of the machine: **a**. When in state A, two events may occur: event 1 and event 2. If event 1 occurs, the machine performs action 1 and moves to state B. If event 2 occurs, the machine moves to state C (no action). **b**. When in state B, two events may occur: event 3 and event 4. If event 3 occurs, the machine performs action 2, but remains in state B. If event 4 occurs, the machine just moves to state C. **c**. When in state C, the machine remains in this state forever.
Verified answer
biology
For the question, write on a separate sheet of paper the letter of the correct answer. Where does fertilization usually take place? A. cervix B. epididymis C. fallopian tubes D. uterus
Verified answer