MRI103: Parameters and Options EXAM 1

Doubling the number of signal averages (NSA or NEX) results in what percentage of SNR? 50 75 100 141

141

For the human eye to detect an increase in the SNR of the image, the SNR must be increased by a minimum of approximately what percentage? 50% 100% 20% 40%

20%

For the human eye to detect an increase in the SNR of the image, the SNR must be increased by a minimum of approximately what percentage? 50% 40% 20% 100%

20%

If SNR is 100%, quadrupling the NEX will increase it to: 40% 141% 200% 400%

200%

Which of the following field strengths has the highest inherent signal-to-noise ratio? 0.5 tesla 0.3 tesla 3.0 tesla 1.5 tesla

3.0 tesla

How many NEX are needed to maintain the SNR at 100% if the slice thickness is changed from 5 to 2.5? 2 4 8 16

4

Halving the receive bandwidth increases the SNR by: 30% 40% 50% 75%

40%

The coil selected for a procedure will have a direct impact on the SNR of the image. The coil that will provide better SNR is: The one that have more channels The one with the smallest size that covers the area of interest The one that is closer to the anatomy All answers are correct

All answers are correct

Which of the following parameters directly impacts the signal-to-noise ratio? Voxel size Number of excitations Repetition time All answers are correct

All answers are correct

Which of the following is a parameter that directly affects the signal-to-noise ratio? Flip Angle Number of excitations Repetition time All of the above

All of the above

By keeping all other parameters constant.Decreasing the slice thickness will ______ SNR. Increase Decrease Not affect

Decrease

Keeping all other parameters constant, decreasing the slice thickness will ______ Increase Decrease Not affected

Decrease

When increasing the matrix, the pixel size will: Increase Stays the same Decrease Vary

Decrease

When echo time is increased, signal-to-noise ratio _____ Stays the same Decreases Increases

Decreases

When the receiver bandwidth is increased, signal to noise ratio _____ Decreases Increases It is not affected

Decreases

For the following spin-echo protocol:FOV: 320/ TR:500/ TE:25/ SliceThick.:5mm/ Slice Gap:1mm/ Slice.#:9/ NEX:4, Matrix:192Decreasing Slice thickness will: Increases SNR Decreases SNR Increase Matrix

Decreases SNR

Noise that degrades image quality in a specific location within an MRI image is known as what? Contrast interference Random noise interference Discrete noise interference Inherent noise interference

Discrete noise interference

The in-plane pixel size can be determined by which of the following methods? Dividing the TR by the NEX Dividing the TR by the slice thickness Dividing the FOV by the Matrix Dividing the NEX by the FOV

Dividing the FOV by the Matrix

In-plane resolution is affected by: FOV Slice Thickness Matrix FOV & Matrix

FOV & Matrix

In a 3D acquisition, which parameter selection will produce a higher-resolution image? FOV 20 cm Matrix 200 x 200 Volume thickness 400 # of slices 400 FOV 200 mm Matrix 100 x 200 Volume thickness 800 mm # of slices 400 FOV 400 mm Matrix 200 x 200 Volume thickness 400 # of slices 200 FOV 40 cm Matrix 100 x 100 Volume thickness 400 # of slices 400

FOV 20 cm Matrix 200 x 200 Volume thickness 400 # of slices 400

Using a narrow receiver bandwidth might result in an Aliasing artifact. True False

False

Bigger voxels will produce images with: Low SNR High SNR Will not affect SNR

High SNR

When slice thickness is increased, signal to noise ratio______ Stays the same Decreases Increase

Increase

What effect does increasing the TR have on SNR? Decrease SNR SNR in unaffected Increase SNR TR only controls length of scan

Increase SNR

What effect does increasing the TR have on SNR? Increase SNR Decrease SNR TR only controls length of scan SNR in unaffected

Increase SNR

What effect does increasing the TR have on SNR? TR only controls length of scan Decrease SNR Increase SNR SNR in unaffected

Increase SNR

What effect does increasing the TR have on SNR? TR only controls length of scan Increase SNR SNR in unaffected Decrease SNR

Increase SNR

Which of the following parameters would NOT increase SNR? Increased TR Increased receiver bandwidth Increased FOV Decreased image matrix

Increased receiver bandwidth

When pixel size increases, signal to noise ratio________ Increases Decreases Stays the same

Increases

When the image matrix is increased, spatial resolution______ Increases Stays the same Decreases

Increases

Which of the following methods will improve SNR the most? Increasing the NEX by 3 Doubling the Transmitter bandwidth Doubling the Receiver bandwidth Cutting by half the Receiver bandwidth

Increasing the NEX by 3

Increasing the Receive Bandwidth will decrease the SNR by: Increasing the amount of signal sample Decreasing the amount of signal sample Increasing the amount of noise sample Decreasing the amount of noise sample

Increasing the amount of noise sample

With the parameters given, which protocol provides the highest signal-to-noise ratio? Long TR/Short TE/ 90 flip angle Long TR/Short TE/ 45 flip angle Long TR/Long TE/ 90 flip angle Short TR/Long TE/ 90 flip angle

Long TR/Short TE/ 90 flip angle

The spatial resolution is directly proportional to: Slice thickness Matrix FOV NEX

Matrix

Which of the following sets of parameters will provide the highest SNR, if all the other parameters remain the same? Matrix 320x320, 2.5 mm slice thickness, FOV 180 Matrix 256x256, 3 mm slice thickness, FOV 200 Matrix 128x128, 1 mm slice thickness, FOV 150 Matrix 512x512, 2mm slice thickness, FOV 120

Matrix 256x256, 3 mm slice thickness, FOV 200

Large voxels produce a higher SNR than small voxels due to which of the following reasons? Shorter T1 vlues Longer T2 value Higher resolution More H nuclei

More H nuclei

__________ sides determine the volume of an element? Dividing its 3 Multiplying its 3 Adding its 3 Multiplying its 2

Multiplying its 3

The "best" technique for improving the overall image quality is to increase: TR NEX Matrix FOV

NEX

The term used to describe a picture element is known as a __ Voxel Volume element Image element Pixel

Pixel

Which of the following terms is more directly related to the image matrix? Voxel Volume Slice thickness Pixel area k-space

Pixel area

What is the formula used to calculate the pixel area? Pixel size = FOV x Matrix Pixel size = FOV x NEX Pixel size = FOV / Matrix Pixel size = FOV / NEX

Pixel size = FOV / Matrix

Which of the following changes will reduce SNR the most? Reducing FOV by half Doubling the PES Reducing slice thickness by half All will produce 50% reduction in the SNR

Reducing FOV by half

Three characteristics commonly used to define the quality of an MRI image are ____ Resolution, Contrast, Signal to noise Resolution, Matrix, Signal to noise Contrast, Resolution, Matrix Signal to noise, Excitations, Contrast

Resolution, Contrast, Signal to noise

As TE increases Scan time increases SNR decreases Spatial Resolution increases All of the above

SNR decreases

How does increasing the number of frequency encoding steps affect the SNR? SNR decreases SNR increases SNR stays the same Phase encoding steps increase

SNR decreases

Keeping other parameters consistent, decreasing the matrix from 512x512 to 320x320 yields what effect? Matrix size does not affect SNR SNR remain the same SNR increases SNR decreases

SNR increases

What is the effect on SNR when reducing the receiver bandwidth of a pulse sequence? SNR decreases SNR is not affected by bandwidth SNR remains the same SNR increases

SNR increases

Increasing the slice thickness by 50% has what effect on SNR? SNR decreases by 50% SNR increases by 10% SNR increases by 400% SNR increases by 50%

SNR increases by 50%

How is SNR affected when the Field of View is decreased? SNR is increased SNR is decreased SNR remains the same Field-of-view cannot decrease

SNR is decreased

Increasing slice thickness increases SNR by which of the following methods? Sampling more spins in the excitation area Increasing the relative FOV Decreasing the number frequency encoding steps Increasing the number of signal averages by 50%

Sampling more spins in the excitation area

Which of the following is true when NEX double? Scan Time is doubled SNR is doubled Spatial Resolution is doubled Contrast to Noise is doubled

Scan Time is doubled

If the slice thickness is increased from 5 to 10 mm: Signal will increase Resolution will increase Anatomical coverage will decrease Partial volume will decrease

Signal will increase

The depth of a volume element is determined by what parameter? Slice thickness Matrix Repetition time NEX

Slice thickness

The width of a volume element is determined by what parameter? Slice thickness FOV/PES NEX

Slice thickness

Which of the following parameters combination will produce an image with less resolution? Slice thickness 3 mm, matrix 192 X 256, FOV 48 cm. Slice thickness 3 mm, matrix 192 X 256, FOV 24 cm. Slice thickness 6 mm, matrix 192 X 256, FOV 48 cm. Slice thickness 3 mm, matrix 192 X 192, FOV 24 cm.

Slice thickness 6 mm, matrix 192 X 256, FOV 48 cm.

As Frequency encoding steps increase: Scan time increases SNR increases Spatial Resolution increases All of the above

Spatial Resolution increases

The ability to distinguish one structure from another on an image is known as ____ Contrast to noise Spatial contrast Spatial resolution Signal to noise

Spatial resolution

Increasing the NEX increases SNR by the: Same number of NEX Square root of the NEX Double of the NEX All of the above

Square root of the NEX

If TE is decreased, what would happen to the spatial resolution: Stays the same Increases Decreases

Stays the same

When the number of excitations is increased, spatial resolution _____ Stays the same Increases Decreases

Stays the same

With similar imaging parameters, what is the weighted image with lower SNR? T1 T2 PD T2*

T2*

Reducing the receive bandwidth might have a direct impact on the minimum ___. TR TI TE TSE

TE

Which of the following parameters combination will produce an image with higher resolution? TR 500 ms, matrix 256 x 256, TE 20 ms, slice thickness 3 mm, FOV 24 cm. TR 800 ms, matrix 512 x 512, TE 10 ms, slice thickness 6 mm, FOV 24 cm. TR 4000 ms, matrix 256 x 256, TE 90 ms, slice thickness 6 mm, FOV 12 cm. TR 2500 ms, matrix 512 x 512, TE 10 ms, slice thickness 3 mm, FOV 12 cm.

TR 2500 ms, matrix 512 x 512, TE 10 ms, slice thickness 3 mm, FOV 12 cm.

The flip angle which produces the best SNR for a given TR and tissue type, is known as: The Ernst angle The perfect angle The Nyquist angle

The Ernst angle

With the parameters given, which protocol provides the highest signal-to-noise ratio? Thick slice/High TE/Small FOV Thin slice/Low TE/Small FOV Thin slice/High TE/Small FOV Thick slice/Low TE/Large FOV

Thick slice/Low TE/Large FOV

Is this voxel isotropic?FOVf: 256 mmFOVp: 75%FES: 256PES: 192Volume Thickness:25 cm# of Slices:250 True False

True

What would be the best choice to improve image quality without affecting the SNR, Resolution, and scan time? Use the smallest possible coil Use large coil Increase Matrix Increase FOV

Use the smallest possible coil

Which of the following will better describe a fine matrix? With low number of frequency encoding and phase encoding and results in large pixels in the FOV With high number of frequency encoding and phase encoding and results in small pixels in the FOV With more number of phases encoding steps compare to frequency encoding steps and results in rectangular pixels With the same number of phase encoding steps and frequency encoding steps and results in square pixels

With high number of frequency encoding and phase encoding and results in small pixels in the FOV

Spatial Resolution is an image quality factor determined by _______ and ________. field strength/receiver coil flip angle/TE TR/NEX slice thickness/pixel area

slice thickness/pixel area