What is a pixel? Calculate the pixel size for a scan of the abdomen using
Change in Spatial Resolution
1) Increased pixel size -->
2) Decreased matrix size -->
3) Decreased DFOV -->
4) 512 x 512 matrix to 1024 x 1024 matrix -->
5) 22 cm DFOV to 25 cm DFOV -->
An acceptable WW and WL for imaging of bone is WW 2300 and WL 500. If a certain pixel has a CT number of +799 HU, what color will the pixel be on the screen? Black, white, or a shade of gray?
Define window width and window level.
In the context of a digital matrix, 1024 x 1024 refers to:
A.the number of pixels in the matrix
B.the size of pixels in the matrix
C.the number of brightness levels displayed in the matrix
D.the physical measurement of the matrix
Increasing the display field-of-view will have what effect on the pixel size?
A.No effect
B.Increased pixel size
C.Decreased pixel size
Calculate the pixel size given these variables:
Matrix size = 512 x 512
Display field-of-View = 12 cm
Scan field-of-view = 25 cm
Reconstruction thickness = 1.25 mm
A.0.023 cm
B.42 cm
C.0.000046 cm
D.0.49 cm
The thickness of a voxel in CT is defined by which of these variables?
A.Acquisition thickness
B.Reconstruction slice thickness
C.Total beam collimation
D.Matrix dimensions
Consider a voxel that includes these materials: air, blood, bile, and feces. What CT number will be displayed by the pixel in the reconstructed image?
A.The total of all tissues
B.The tissue with the maximum CT number
C.The tissue with the minimum CT number
D.The average of all tissues
Increasing the window level of a CT image will result in:
A.Increased brightness
B.Decreased brightness
C.Increases contrast
D.Decreased contrast
How will increasing the window width of a digital image affect the overall appearance of the image?
A.Increased brightness
B.Decreased brightness
C.Increases contrast
D.Decreased contrast
Which of these widowing techniques will result in the brightest overall image?
A.window width = 450, window level = 45
B.window width = 1500, window level = 40
C.window width = 300, window level = 100
D.window width = 40, window level = -30
Which of these scenarios will produce cervical spine images with the best spatial resolution?
A. 12 cm display field-of-view (DFOV)
B. 15 cm display field-of-view (DFOV)
C. 17 cm display field-of-view (DFOV)
D. 22 cm display-field-of-view (DFOV)
Which of these matrices will have the best spatial resolution?
A. 1024 x 1024
B. 512 x 512
C. 256 x 256
D. 2048 x 2048
Which of these factors would produce a radiographic image with the highest spatial resolution?
increased pixel size
increased matrix size
increase field-of-view
Consider this scenario: A new CT scanner in the radiology has a matrix size of 1024 x 1024. What variable change can increase the matrix size?
A. Increase the display field-of-view
B. Increase the scan field-of-view
C. Increase the acquisition thickness
D. None of these changes will affect of the matrix
Which of these variable changes can a technologist make to increase the spatial resolution of a CT image?
A. Increase the matrix size
B. Decrease the matrix size
C. Increase the display field-of-view (DFOV)
D. Decrease the display field-of-view (DFOV)
The thickness of a voxel in CT is defined by which of these variables?
A. Acquisition thickness
B. Reconstruction slice thickness
C. Total beam collimation
D. Matrix dimensions
Changing the thickness of a voxel may also change:
A. The tissue types included in the voxel
B. The matrix size of the digital image
C. The pixel size in the digital image
In CT imaging, window width refers to:
A. Brightness of the displayed image
B. Contrast of the displayed image
C. Center point of Hounsfield values in the displayed image
Increasing the window level of a CT image will result in:
A. Increased brightness
B. Decreased brightness
C. Increases contrast
D. Decreased contrast
How will increasing the window width of a digital image affect the overall appearance of the image?
A. Increased brightness
B. Decreased brightness
C. Increases contrast
D. Decreased contrast
Which of these widowing techniques will result in the brightest overall image?
A. window width = 450, window level = 45
B. window width = 1500, window level = 40
C. window width = 300, window level = 100
D. window width = 40, window level = -30
Consider an imaging protocol that calls for very high contrast images of the brain. Which of these settings will display an image with the highest contrast?
A. window width = 550, window level = 45
B. window width = 1500, window level = 50
C. window width = 300, window level = 80
D. window width = 40, window level = 30
Read this scenario and answer the question that follows:
A radiologist is requesting changes to the brightness and contrast of images being used for a CT-guided biopsy in the pelvis. Which of these windowing techniques will result in the darkest image with the highest contrast?
A. window width = 450, window level = 45
B. window width = 1500, window level = 40
C. window width = 300, window level = 30
D. window width = 40, window level = 100
A CT myelogram calls for a 2100 window width and a 700 window level. What pixel values will be displayed as black?
A. CT numbers above 1750
B. CT numbers below -350
C. CT numbers above 2800
D. CT numbers below -1400
When using an 80 WW and 30 WL, what range of pixel intensities will be assigned a shade of gray?
A. 30 to 80
B. -50 to 110
C. -10 to 70
D. 50 to 110
Which of these window settings would be appropriate for viewing the major organs of the abdomen?
A. 2500 WW and 600 WL
B. 400 WW and 40 WL
C. 1800 WW and -600 WL
D. 80 WW and 30 WL
If using a 400 WW and 40 WL, the cerebral spinal fluid in the brain will appear as:
A. White
B. Gray
C. Black-->
a 40 cm DFOV and a 1024 x 1024 matrix.
In the table below, indicate how the listed technical changes affect spatial resolution.
Technical change --> Change in Spatial Resolution
1) Increased pixel size -->
2) Decreased matrix size -->
3) Decreased DFOV -->
4) 512 x 512 matrix to 1024 x 1024 matrix -->
5) 22 cm DFOV to 25 cm DFOV -->
An acceptable
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