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MRI image basics
| Question | Answer |
|---|---|
| All of the following yield a higher signal-to-noise ratio EXCEPT: A. Increase TR B. Increase TE C. Larger FOV D. Higher NEX E. Decrease Matrix | B. Increase TE |
| High amplitude signals are stored in the: A. Outer edges of k-space B. Bottom line of k-space C. Top line of k-space D. Center portion of k-space | D. Center portion of k-space |
| A reduction in FOV will result in: A. Decrease in spatial resolution B. Increase in SNR C. Decrease in SNR D. None of the above E. A and C only | C. Decrease in SNR |
| SNR increases with all the following adjustments, EXCEPT: A. Increasing FOV B. Decreasing pixel size C. Increasing NEX/NSA D. Decreasing phase matrix | B. Decreasing pixel size |
| if a sequence with a matrix of 256 x 512 is adjusted to 512 x 512, A. The SNR will stay the same B. The scan time will decrease C. The SNR will increase and the scan time will decrease D. The SNR will decrease and the scan time will increase | D. The SNR will decrease and the scan time will increase |
| The timing of the RF pulses in an MRI pulse sequence controls: A. How long the procedure takes B. Pixel size C. Image contrast D. Spatial resolution | C. Image contrast |
| Calculate the pixel area for the following sequence: TR 4000, TE 120, FOV 28cm, 304 x 304 matrix, 2 NEX, ETL 12. A. 0.76 mm2 B. 0.85 mm2 C. 0.92 mm2 D. 1.84 mm2 | B. 0.85 mm2 FOV/matrix x FOV/matrix = pixel area. 280/304 x 280/304 = 0.85 mm2. |
| Another name for a picture element is a: A. Voxel B. Pixel C. Cubicle D. Filament | B. Pixel |
| The pixel size of the images which result from a 3D acquisition using a 240mm FOV, a 272 x 272 matrix, 32 slices and a volume of 64 mm is: A. 0.56 x 0.56 mm B. 0.88 x 0.88 mm C. 1.12 x 1.12 mm D. 1.58 x 1.58 mm | B. 0.88 x 0.88 mm |
| The central lines of k-space are associated with _____________ in a fast spin echo sequence. A. The echo train length B. Echo time C. Spatial resolution D. Contrast information | D. Contrast information |
| The scan time of a fast spin echo sequence utilizing a TR of 3500ms, a TE of 90ms, a 256x256 matrix, 1NSA, a 220mm FOV and an echo train length of 5 is ______ minutes, approximately. A. 2 B. 3 C. 8 D. 11 | B. 3 |
| Reducing the FOV (field of view) only will result in: A. Decreased spatial resolution B. Increased signal-to-noise C. Decreased signal-to-noise D. Increased T2 weighting | C. Decreased signal-to-noise |
| Decreasing the TR will: A. Lower SNR B. Reduce scan time C. Increase SNR D. Both A and B | D. Both A and B |
| As the number of phase encodings is increased from 256 to 512, SNR (signal to noise ratio): A. Increases B. Decreases C. Doubles D. Is unchanged | B. Decreases |
| All of the following affect acquisition time EXCEPT: A. TR B. TE C. NEX D. Matrix | B. TE |
| As the number of excitations (NEX) is increased from 1 to 3, which of the following does NOT occur? A. The scan time triples B. The pixel size is increased C. The image resolution remains the same D. The signal-to-noise ratio is increased | B. The pixel size is increased |
| Which parameter will provide the better spatial resolution? A. 4mm slice thickness; 256 x 192 matrix B. 4mm slice thickness; 256 x 256 matrix C. 6mm slice thickness; 256 x 192 matrix D. 6mm slice thickness; 256 x 256 matrix | B. 4mm slice thickness; 256 x 256 matrix |
| The overall signal-to-noise ratio will increase in 3D volume imaging when there is an increase in: A. Number of slices or partitions B. TE C. Phase Matrix D. Field of View E. A and/or D | E. A and/or D |
| Increasing NSA will: A. Improve SNR B. Degrade SNR C. Shorten scan time D. Have no effect on SNR | A. Improve SNR |
| A method of reducing MRI scan time by not filling as many lines of k-space in the phase direction, while maintaining spatial resolution, is known as: A. Halfscan B. Rectangular FOV C. Partial fourier D. Fast spin echo | B. Rectangular FOV |
| Each line of k-space is defined by the: A. Phase encoding gradient B. Frequency encoding gradient C. Slice select gradient D. Dictionary | A. Phase encoding gradient |
| Which would NOT compensate for the change in signal-to-noise as a result of decreasing the FOV A. Reducing the image matrix B. Reducing the number of echo train lengths C. Reducing the number of excitations D. Increasing slice thickness | C. Reducing the number of excitations |
| Calculate the pixel area for the following sequence: TR 450, TE 12, FOV 18cm, 224 x 256 matrix, 4 NEX. A. 0.56 mm2 B. 0.70 mm2 C. 0.80 mm2 D. 1.50 mm2 | A. 0.56 mm2 FOV/matrix x FOV/matrix = pixel area. 180/224 x 180/256 = 0.56 mm2 |
| With regards to k-space, the data containing signal and contrast information are located along: A. X gradient B. The phase axis C. The central lines D. The outer lines | C. The central lines |
| Reducing the slice thickness will result in: A. An increase in partial volume averaging B. Decreasing pixel size C. A decrease in SNR D. A & B only E. None of the above | C. A decrease in SNR |
| Calculate the voxel volume for the following pulse sequence: TR 2000, TE 85, FOV 28cm, Matrix 272 x 320, 5mm slice thickness, 3 NSA. A. 0.88 mm3 B. 1.03 mm3 C. 1.91mm3 D. 4.55 mm3 | D. 4.55 mm3 To calculate voxel volume, first determine pixel area. FOV/matrix x FOV/matrix = pixel area. Pixel area x slice thickness = voxel volume. 280/272 x 280/320 = 0.91 mm2. 0.91 x 5 = 4.55mm3 |
| With regards to k-space, the data containing high resolution are located along: A. The Z gradient B. The phase axis C. The central lines D. The outer lines | D. The outer lines |
| With rFOV that is twice as tall as it is wide, phase direction oriented along the smaller dimension of the FOV, which relationships between the frequency and phase steps yields square pixels? C. Phase steps must be half the number of frequency steps | C. Phase steps must be half the number of frequency steps |
| All of the following would aid in reducing scan time EXCEPT: A. Utilizing the coarsest matrix possible B. Reducing NEX C. Reducing TE D. Increasing parallel imaging factor E. Setting TR to shortest | C. Reducing TE |
| K-space is typically filled: A. With a funnel B. One line at a time C. From back to front D. From right to left | B. One line at a time |
| If the repetition time is doubled, the scan time will: A. Be 40% greater B. Double C. Be half of what it was D. Triple | Double |
| If the NEX is increased from 2 to 6, the signal-to-noise ratio increase would be: A. 1.4 B. 1.7 C. 2 D. 4 | B. 1.7 |
| An increase in TR will produce all of the following EXCEPT: A. Increase the signal-to-noise ratio B. Decrease T1 weighting C. Decrease the number of available slices D. Increase scan time | C. Decrease the number of available slices |
| _______ is when only half the views of k-space are filled in the frequency axis. A. Diffusion tensor B. Anti aliasing C. Half Fourier D. Partial or fractional echo | D. Partial or fractional echo |
| Water has a __________ T1 relaxation time and a ________ T2 relaxation time. A. short; short B. short; long C. long; short D. long; long | long; long |
| Assuming all other parameters are the same, a ___________ ms TR provides the best signal-to-noise ratio. A. 30 B. 200 C. 500 D. 800 | D. 800 |
| Choose the correct slice thickness to create an isotropic voxel for the following: TR 2000, TE 90, Matrix 256 x 256, FOV 32cm. A. 0.75 mm B. 1.25 mm C. 2.00 mm D. 2.50 mm | B. 1.25 mm |
| Acquiring a bit more than half the phase k-space samples, then interpolating the data with zeroes for the remaining half is a technique known as: A. Half Fourier B. Zero fill C. Fast spin echo D. A and/or B | D. A and/or B |
| The smallest object that can be resolved in an image acquired with a 20cm FOV and a 224 x 224 matrix is _________ mm. A. 0.54 B. 0.89 C. 1.12 D. 1.89 | B. 0.89 |
| Assuming all other parameters are the same, an echo time of ___________ ms provides the best Signal-to-Noise Ratio. A. 15 B. 30 C. 80 D. 110 | 15 |
| Which pulse sequence parameters would yield an image with the most blurring? A. 400TR, 25TE, 256 x 256, 5mm slice thickness, 1NSA B. 2000TR, 30TE, 256 x 256, 5mm slice thickness, 6 ETL, 2NSA C. 4000TR, 60TE, 256 x 256, 5mm slice thickness, 12 ETL, 4 | C. 4000TR, 60TE, 256 x 256, 5mm slice thickness, 12 ETL, 4 |
| What would the scan time be in a 3D volume acquisition as follows: TR 32 ms, TE 4 ms, Flip Angle 15°, FOV 18cm, 2mm slice thickness, 96 slices, 192 x 256 matrix, 1 NEX? A. 4 min 28 sec B. 5 min 12 sec C. 8 min 42 sec D. 9 min 50 sec | D. 9 min 50 sec |
| What formula is used to calculate the size of the pixel? A. Matrix ÷ FOV B. FOV ÷ slice thickness C. FOV ÷ matrix D. Slice thickness ÷ matrix | C. FOV ÷ matrix |
| : Reducing the number of lines filled in k-space will produce an image:- A. With a decrease in spatial resolution B. With an increase in spatial resolution C. With an decrease in overall SNR D. A and C | A. With a decrease in spatial resolution |
| Reducing the phase matrix from 256 to 192 will: A. Increase the signal-to-noise ratio B. Decrease imaging time C. Decrease spatial resolution D. All of the above | D. All of the above |
| Which of the following is NOT affected by changing the slice thickness? A. The signal-to-noise ratio of the image B. The T1 contrast C. The image resolution D. The anatomical coverage | The T1 contrast |
| Fat has a _______ T1 relaxation time and a ________ T2 relaxation time. A. short; short B. short; long C. long; short D. long; long | short; short |
| Calculate the voxel volume for the following pulse sequence parameters: TR 450, TE 20, FOV 24cm, 320 x 320 matrix, 3mm slice thickness. A. 0.75mm3 B. 1.69mm3 C. 1.75mm3 D. 2.25mm3 | B. 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 |
| In a fast spin echo sequence with a 28 cm FOV, 256 x 512 matrix, TR 2200, 90 TE, 5mm slice thickness, 8 ETL and 3 NEX, the s can time would be: A. 2 minutes 11 seconds B. 3 minutes 31 seconds C. 3 minutes 52 seconds D. 4 minutes 8 seconds | B. 3 minutes 31 seconds |
| : A set of specifically timed instructions to the magnet is known as: A. A recipe B. A pulse sequence C. Gyromagnetic instructor D. Fourier transformation | B. A pulse sequence |
Created by:
zach1710