Nikk's MRI quizzes for midterm
A spin echo image with a long TR and a long TE is known as what type of image? A) T2 weighted image B) T1 weighted image C) Proton density weighted image D) Spin density weighted image
A
Consider the following: TR= 500ms. TE=20ms. FOV=22cm. Matrix=192(p) x 256(f) Slice thickness = 5.0mm. Flip Angle= 90 degrees Please calculate the pixel area. A) .98mm2 B) 4.3mm2 C) 5.81 mm2 D) 1.14 mm2
A
In a conventional spin echo sequence, the phase encoding gradients are applied ______ the echo is received. A) before B) after C) none of the above D) at the same time
A
In a normal spin echo pulse sequence, the slice selection gradient is applied ______ the 90o RF is applied. A) at the same time as B) before C) None of the above D) after
A
In the presence of an external magnetic field, the hydrogen nucleus wobbles about the magnetic field as it spins. This is called A) precession B) B0 C) the gyromagnetic ratio D) recession
A
In which of the following sequences is all the transverse magnetization rewound at the end of each TR period? a)Coherent gradient echo b)Incoherent gradient echo c)EPI
A
Of the following parameters, which would give the best spatial resolution? a)256 × 256, 3 mm slice thickness, 12 cm FOV, 1 NEX b)256 × 128, 8 mm slice thickness, 40 cm FOV, 4 NEX c)512 × 256, 6 mm slice thickness, 14 cm FOV, 2 NEX
A
Please consider the following information: TR = 500 ms. TE = 20 ms. FOV = 22 cm. Matrix 192(p)x 256 (f) Slice thickness = 5.0 mm. Flip angle = 90 degrees Calculate the phase dimension of the pixel. A) 1.14 mm. B) 38.4 mm C) .87 mm. D) 2.27 ms.
A
The _____ determines the magnitude of phase shift between protons located at different points along a gradient. A) slope B) Fourier transform C) receive bandwidth D) number of signal averages
A
The area where the raw image data is stored. A) K space B) F troop C) Nyquist theorem D) Fourier transform
A
The scan time of a conventional spin echo is expressed by which equation? A) TR x Np x NSA B) TR x Matrix x NSA C) TR x Nf x NSA D) TR x Np x NSA/ ETL
A
The vertical axis of k-space represents which axis of the image? A) Phase encoding B) Frequency encoding C) None of the above D) Slice selection
A
Using a long TE enhances T2 and T2* contrast. a)true b)false
A
When the number of excitations is increased, the spatial resolution _____ . A) stays the same B) decreases C) increases
A
When the number of signal averages is doubled, by how much does the scan time change? a)× 2 b)1/2 c)22 d)√2
A
Which of these is a consequence of decreasing the TR from 2500 ms to 500 ms? a)Scan time decreases b)T1 weighting decreases c)Spatial resolution decreases d)Slice number available increases
A
A small flip angle, long TE, and short TR will produce which type of gradient echo contrast? A) T1 B) T2* C) PD D) T2
B
Combining a low flip and long TR results in saturation. a)true b)false
B
Fat has a ____ T1 relaxation time and appears _____ on a T1 weighted image when compared to water. A) Long, Bright B) Short, Bright C) Long, Dark D) Short, Dark
B
Generally, the application of a shallow gradient results in a ____ signal amplitude. A) low B) high C) insignificant
B
Gradient echo sequences use flip angles _______________ A) To reduce SAR for larger patients B) Less than 90o C) To control saturation effects D) That vary between pulse repetitions
B
Image data with high spatial resolution is stored in which area of k-space? A) Central lines B) Outer lines C) Negative lines only D) Positive lines
B
In a T1 weighted inversion recovery sequence, contrast is primarily dependent on which of the following? A) PD B) TI C) TR D) TE
B
In a conventional spin echo pulse sequence, the slice selection gradient is applied ______ the 90o RF is applied. A) after B) at the same time C) before D) none of the above
B
In the presence of an external magnetic field, most hydrogen nuclei A) flip 90° B) align parallel to the magnetic field (the low energy state) C) c and d D) align randomly E) align antiparallel to the magnetic field (the high energy state)
B
MR images that are the result of differences in the longitudinal relaxation characteristics of tissues are known as ___. A) T2 weighted images B) T1 weighted images C) Proton density weighted images D) Functional images
B
Of the following parameters, which would give the highest SNR? a)256 × 256, 3 mm slice thickness, 12 cm FOV, 1 NEX b)256 × 128, 8 mm slice thickness, 40 cm FOV, 4 NEX c)512 × 256, 6 mm slice thickness, 14 cm FOV, 2 NEX
B
The _____ determines the magnitude of phase shift between protons located at different points along a gradient. A) receive bandwidth B) Slope C) number of signal averages D) fourier transform
B
The imaging parameter which primarily controls T2 weighting is _____. A) None of the above B) Echo time C) Repetition time D) Inversion time
B
The use of small flip angles (less than 90o ) results in which of the following? A) A decrease in signal contribution B) All of the above C) A decrease in the signal- to- noise ratio D) A decrease in the component of transverse magnetization
B
What is the Larmor equation? A) a calculation of signal intensity B) an expression of symbolizing the relationship between the precessional frequency and magnetic field strength C) a method for performing vector addition D) an expression relating B1 to field strength
B
When the FOV is increased, the signal to noise ratio ______ . A) stays the same B) increases C) decreases
B
When the bandwidth is increased, the signal to noise ratio _____ . A) increases B) decreases C) stays the same
B
When the image matrix increases, acquisition time _______ . A) decreases B) increases C) stays the same
B
Which of the following does NOT occur when the receive bandwidth is reduced? a)SNR increases b)Chemical shift artefact improves c)Number of slices available decreases d)TE increases
B
Which of the following statements about partial averaging is true? a)All the lines of K space are filled b)A percentage of lines are filled and the rest is filled with zeroes c)A percentage of the lines are filled and this is used to extrapolate the missing data d)None of the lines are filled
B
Which of these is a consequence of decreasing the phase matrix? a)Truncation artefact improves b)SNR increases c)Spatial resolution increases d)Scan time increases
B
Which portion of K-space is filled with data from signals with low signal amplitude ? A) positive lines B) outer lines C) negative lines D) central lines
B
Which portion of k-space is filled with data from signals with low signal amplitude? A) Central lines B) Outer lines C) Positives lines D) Negative lines
B
Which type of imaging method samples only one half of the echo and the computer calculates the remaining data? A) Multiple NSA imaging B) Fractional echo imaging C) 2D sequential D) 2D volumetric
B
A hydrogen nuclei placed in a 1.5 T magnetic field will precess at ____MHz. A) 21.3 B) 28.4 C) 63.9 D) 42.6
C
Another name for a proton density weighted image is _____ . A) Inversion recovery B) T2 weighted C) Spin density D) Both A and B
C
Generally, the application of a shallow gradient results in a ____ signal amplitude. A) low B) insignificant C) high
C
Halving a square FOV reduces the SNR by: a)1/2 b)1/4 c)3/4 d)1/8
C
In a normal spin echo sequence, the phase encoding gradients are applied ______ the echo is received. A) after B) None of the above C) before D) at the same time
C
In a proton density weighted image, tissues with a low number of hydrogen nuclei appear ____. A) Isointense B) Hyperintense C) Hypointense D) None of the above
C
In conventional spin echo sequences, how many phase encoding steps must be performed to fill 128 lines of k-space? A) 256 B) 192 C) 128 D) 64
C
In terms of the events that take place during an MRI pulse sequence, what factor determines the frequency matrix? a)Slope of frequency encoding gradient b)Sampling time c)The number of data points in each line d)The sampling frequency
C
Please consider the following: TR= 500ms. TE= 20ms. FOV= 22cm. Matrix 192(p) x 256(f) Slice thickness= 5.0 mm. Flip angle = 90 degrees Calculate the voxel volume. A) 2.55 mm3 B) 5.7 mm3 C) 4.9 mm3 D) 4.3 mm3
C
Please consider the following: TR= 500ms. TE= 20ms. FOV= 22cm. Matrix= 192(p) x 256(f) Slice thickness= 5.0mm. Flip Angle= 90 degrees Calculate the frequency dimension of the pixel. A) .51 mm B) 1.14 mm C) .86 mm D) 11.6 mm.
C
Slice thickness is determined by: A) the RF bandwidth B) the magnitude of the gradient C) A and B D) the Fourier transform E) TR
C
T2 relaxation time is defined as when ___________ of the ______________ magnetization has decayed A) 76% Longitudinal B) 76% Tissues C) 63% Transverse D) 63% Longitudinal
C
The difference in SNR between two regions of an image is known as _____ . A) spatial resolution ratio B) signal to noise ratio C) contrast to noise ratio D) none of the above
C
The process of filling only a percentage of k-space with acquired data and filling the rest with zeros is known as ___ . A) Partial echo B) Partial voluming C) Partial averaging D) Partial saturation
C
What properties of an MR signal can we measure? A) T1, T2, and TR B) tesla, gauss and MHz C) amplitude, frequency and phase D) TR, TE, and TI
C
Which of the following statements is true in an incoherent gradient echo sequence? a)Residual transverse magnetization has the same phase as the magnetization most recently created b)The flip angle is always 10° c)The system discriminates between residual and the most recently created transverse magnetization because it has a different phase value d)It is not a steady state sequence
C
Which type of imaging method samples only one half of the echo and the computer calculates the remaining data? A) 2D volumetric B) 2D sequential C) fractional echo imaging D) multiple NSA imaging
C
Which TWO factors from the following list affect slice thickness? a)Slew rate of the slice select gradient b)Polarity of slice select gradient c)Slope of slice select gradient d)Duration of slice select gradient e)Power of transmitted RF f)Duration of transmitted RF g)Frequency of transmitted RF h)Bandwidth of transmitted RF i)Amplitude of transmitted RF
C & H
A vector possesses which two properties? A) Force and inertia B) Size and space C) Direction and latitude D) Magnitude and direction
D
Calculate the scan time for a sequence with the following parameters: TR = 2000ms TE = 80 ms FOV = 18 x 18 cm Slice thickness = 4.0 mm Slice gap = 1.0 mm Matrix = 256 x 160 NSA = 1 A) 8.53 min B) 1.37 min C) 53.3 min D) 5.3 min
D
Doubling the number of signal averages changes the SNR by how much? a)× 2 b)1/2 c)22 d)√2
D
Following a 90 degree RF pulse, the signal that is created is called A) Gradient echo B) FRE C) Spin echo D) Free induction decay
D
If a phase resolution of 256 is desired, then the TR must be repeated _______ times. A) 512 B) 192 C) twice D) 256
D
Image data along both the phase and frequency axis with the lowest signal amplitude is stored in which area of k-space? A) None of the above B) Central lines C) Positive lines only D) Outer lines
D
In a T1 weighted image, a short TE is used to ____ . A) Maximize T1 effects B) Maximize T2 effects C) Minimize T1 effects D) Minimize T2 effects
D
In a T2 weighted image, a long TR is used to ____. A) Minimize T1 effects B) Minimize T2 effects C) Maximize T1 effects D) Maximize T2 effects
D
In a T2 weighted image, tissues with a long T2 relaxation times appear ____ compared to tissues with short T2 relaxation times. A) Hypointense B) None of the above C) Isointense D) Hyperintense
D
Increasing the field strength increases SNR because: a)the flip angle increases b)the NMV increases in size because the high energy population of spins increases c)the precessional frequency increases d)the NMV increases in size because the low energy population of spins increases
D
MR images that are based on the differences in the amount of hydrogen nuclei in tissues are known as _____ . A) T1 weighted images B) Functional images C) T2 weighted images D) Proton density weighted images
D
Spins aligned in the anti-parallel direction are in A) A constant state of flux B) A resonant condition C) A low energy state D) A high energy state
D
The area in the computer (array processor) where the raw image data is stored. A) F troop B) Nyquist theorem C) Fourier transform D) K space
D
The speed at which the nuclei precess is defined as the ... A) phase B) receive bandwidth C) transmit bandwidth D) precessional frequency
D
Which best describes "net magnetization" A) the excess number of hydrogen nuclei aligned opposite to the direction of the applied magnetic field (high energy state) B) the excess number of magnetic fields applied to the tissue C) the excess number of hydrogen nuclei spinning D) the excess number of hydrogen nuclei aligned in the direction of the applied magnetic field (low energy state).
D
Which is not an advantage of a gradient echo pulse sequence? A) Short TE B) Short TR C) Speed D) Presence of T2*
D
Which of the following parameters directly affect the signal to noise ratio? A) voxel size B) number of excitations C) TR D) all of the above
D
Which of the following statements about partial echo is true? a)All of K space is filled b)The right-hand side of K space is filled but the left is filled with zeroes c)The left-hand side is filled and the right is filled with zeroes d)The right-hand side is filled and data from this is extrapolated and placed in the left-hand side of K space
D
Which of these is NOT a consequence of decreasing the TR from 2500 ms to 500 ms? a)Scan time decreases b)T1 weighting increases c)Slice number available decreases d)SNR increases
D
Which of these is NOT a consequence of decreasing the phase matrix? a)SNR increases b)Spatial resolution decreases c)Truncation artefact gets worse d)Scan time increases
D
________________ describes the condition reached within a few seconds of hydrogen being placed in a magnetic field. A) Phase coherence B) FID C) Resonance D) Equilibrium
D