Mosby CT Registry Review questions with accurate detailed
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solutions
What is the smallest component of a digital image - correct answer✔✔pixel
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How many CT numbers are assigned to each pixel in the image matrix? - correct
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answer✔✔One
In a CT image, the CT number - correct answer✔✔Of a material is dependent on its linear
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attenuation coefficient ||
Each two-dimensional square of data that make up the CT image is called a - correct
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answer✔✔pixel
What is an element of the digital image - correct answer✔✔pixel
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Which of the following influences the spatial resolution in cardiac CT imaging - correct
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answer✔✔*detector size ||
*reconstruction interval ||
*pitch
As patient motion increases spatial resolution decreases - correct answer✔✔TRUE
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Which is an advantage of using a small focal spot - correct answer✔✔increased spatial
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resolution
,Increasing the CT image matrix from 256x256 to 512x512 will likely improve? - correct
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answer✔✔High-contrast spatial resolution || ||
The practical limiting spatial resolution of a CT scanner is 3.6 lp/cm. What size object does
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this correspond to? - correct answer✔✔1.4 mm
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Use of a bone filter, as opposed to a soft tissue filter, to reconstruct CT images would likely
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improve? - correct answer✔✔Spatial resolution || || || ||
The spatial resolution of a typical CT scanner is on the order of? - correct answer✔✔1 mm
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A 512 x 512 matrix CT image over a 30-cm field of view could show a spatial resolution of
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no better than ? lp/cm? - correct answer✔✔8.5
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When comparing a 512x512 matrix to a 1024x1024 matrix, the 1024x1024 matrix? - correct
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answer✔✔Contains four times as many pixels: 1024 x 1024 =1048576 then 512 x 512= || || || || || || || || || || || || || ||
262144...then divide 1048576 /262144 = 4 || || || || ||
High contrast spatial resolution and low contrast resolution are typically measured baseline
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and ? thereafter - correct answer✔✔Biannually
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To improve the high contrast spatial resolution of a CT study, one would increase _____
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while keeping all other factors the same. - correct answer✔✔Matrix size (128x128 to
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512x512)
A radiologist wants to improve the high-contrast spatial resolution of anatomy which
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he/she is examining by CT. The change which would best lead to this improvement is -
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correct answer✔✔Increase the matrix size
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,To improve the high-contrast spatial resolution of a CT study, one could increase ? while
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keeping all other factors the same? - correct answer✔✔Matrix size
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A voxel contains 25% air, 50% water and 25% bone. The CT number for this voxel would be
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expected to be _____ HU? - correct answer✔✔0 || || || || || || ||
How many pixels are contained in a 1,024 matrix image? - correct answer✔✔D. 1,048,576
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MATH 1024 X1024 || ||
It is located in a matrix and is a two dimensional representation of a voxel - correct
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answer✔✔pixel
When CT numbers are calculated for voxels (volume elements) of tissue what is assigned
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the calculated number and a subsequent shade of gray - correct answer✔✔pixel
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What is defined as a picture element or the smallest component of the digital image -
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correct answer✔✔pixel ||
A CT scan produces a 512x512 matrix transverse image of a 30 cm diameter FOV. Each pixel
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is approximately _____ mm on a side. - correct answer✔✔0.6 equation: 30cm/512= .058cm
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convert to mm and its .58 which is approximately 0.6|| || || || || || || || ||
The ability of a system to define small objects distinctly is referred to as which of the
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following? - correct answer✔✔spatial resolution || || || ||
Which of the following terms is/are commonly used to describe a CT scanner's ability to
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differentiate objects with similar linear attenuation coeffiecents - correct answer✔✔*spatial || || || || || || || || || ||
resolution
, *sensitivity
Which of the following factors have an affect on contrast resolution - correct
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answer✔✔*patient size ||
*slice thickness ||
*pixel size ||
*mAs/dose
As mAs/dose increases contrast resolution decreases - correct answer✔✔FALSE
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As mAs/dose increases contrast resolution INCREASES - correct answer✔✔TRUE
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The ability of a CT scanner to accurately image objects with similar densities is termed -
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correct answer✔✔*contrast resolution
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*sensitivity
Which of the following has a direct relationship on increasing contrast resolution - correct
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answer✔✔*mAs/dose increase ||
*Slice thickness ||
For a particular CT scanner's beam quality, the linear attenuation coefficient for water is
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0.20 cm-1 and for a certain tumor is 0.21 cm-1. What is the CT number of the tumor? -
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correct answer✔✔50. Equation (.21-.20/.21) × 1000= 50
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A CT scanner with poor contrast resolution or low sensitivity has difficulty separating -
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correct answer✔✔tissues whose linear attenuation coefficients are nearly equal
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solutions
What is the smallest component of a digital image - correct answer✔✔pixel
|| || || || || || || || || || ||
How many CT numbers are assigned to each pixel in the image matrix? - correct
|| || || || || || || || || || || || || || ||
answer✔✔One
In a CT image, the CT number - correct answer✔✔Of a material is dependent on its linear
|| || || || || || || || || || || || || || || || ||
attenuation coefficient ||
Each two-dimensional square of data that make up the CT image is called a - correct
|| || || || || || || || || || || || || || || ||
answer✔✔pixel
What is an element of the digital image - correct answer✔✔pixel
|| || || || || || || || || ||
Which of the following influences the spatial resolution in cardiac CT imaging - correct
|| || || || || || || || || || || || || ||
answer✔✔*detector size ||
*reconstruction interval ||
*pitch
As patient motion increases spatial resolution decreases - correct answer✔✔TRUE
|| || || || || || || || ||
Which is an advantage of using a small focal spot - correct answer✔✔increased spatial
|| || || || || || || || || || || || || ||
resolution
,Increasing the CT image matrix from 256x256 to 512x512 will likely improve? - correct
|| || || || || || || || || || || || || ||
answer✔✔High-contrast spatial resolution || ||
The practical limiting spatial resolution of a CT scanner is 3.6 lp/cm. What size object does
|| || || || || || || || || || || || || || || ||
this correspond to? - correct answer✔✔1.4 mm
|| || || || || ||
Use of a bone filter, as opposed to a soft tissue filter, to reconstruct CT images would likely
|| || || || || || || || || || || || || || || || || ||
improve? - correct answer✔✔Spatial resolution || || || ||
The spatial resolution of a typical CT scanner is on the order of? - correct answer✔✔1 mm
|| || || || || || || || || || || || || || || ||
A 512 x 512 matrix CT image over a 30-cm field of view could show a spatial resolution of
|| || || || || || || || || || || || || || || || || || ||
no better than ? lp/cm? - correct answer✔✔8.5
|| || || || || || ||
When comparing a 512x512 matrix to a 1024x1024 matrix, the 1024x1024 matrix? - correct
|| || || || || || || || || || || || || ||
answer✔✔Contains four times as many pixels: 1024 x 1024 =1048576 then 512 x 512= || || || || || || || || || || || || || ||
262144...then divide 1048576 /262144 = 4 || || || || ||
High contrast spatial resolution and low contrast resolution are typically measured baseline
|| || || || || || || || || || || ||
and ? thereafter - correct answer✔✔Biannually
|| || || || ||
To improve the high contrast spatial resolution of a CT study, one would increase _____
|| || || || || || || || || || || || || || ||
while keeping all other factors the same. - correct answer✔✔Matrix size (128x128 to
|| || || || || || || || || || || || ||
512x512)
A radiologist wants to improve the high-contrast spatial resolution of anatomy which
|| || || || || || || || || || || ||
he/she is examining by CT. The change which would best lead to this improvement is -
|| || || || || || || || || || || || || || || ||
correct answer✔✔Increase the matrix size
|| || || ||
,To improve the high-contrast spatial resolution of a CT study, one could increase ? while
|| || || || || || || || || || || || || || ||
keeping all other factors the same? - correct answer✔✔Matrix size
|| || || || || || || || ||
A voxel contains 25% air, 50% water and 25% bone. The CT number for this voxel would be
|| || || || || || || || || || || || || || || || || ||
expected to be _____ HU? - correct answer✔✔0 || || || || || || ||
How many pixels are contained in a 1,024 matrix image? - correct answer✔✔D. 1,048,576
|| || || || || || || || || || || || || ||
MATH 1024 X1024 || ||
It is located in a matrix and is a two dimensional representation of a voxel - correct
|| || || || || || || || || || || || || || || || ||
answer✔✔pixel
When CT numbers are calculated for voxels (volume elements) of tissue what is assigned
|| || || || || || || || || || || || || ||
the calculated number and a subsequent shade of gray - correct answer✔✔pixel
|| || || || || || || || || || ||
What is defined as a picture element or the smallest component of the digital image -
|| || || || || || || || || || || || || || || ||
correct answer✔✔pixel ||
A CT scan produces a 512x512 matrix transverse image of a 30 cm diameter FOV. Each pixel
|| || || || || || || || || || || || || || || ||
is approximately _____ mm on a side. - correct answer✔✔0.6 equation: 30cm/512= .058cm
|| || || || || || || || || || || || || ||
convert to mm and its .58 which is approximately 0.6|| || || || || || || || ||
The ability of a system to define small objects distinctly is referred to as which of the
|| || || || || || || || || || || || || || || || ||
following? - correct answer✔✔spatial resolution || || || ||
Which of the following terms is/are commonly used to describe a CT scanner's ability to
|| || || || || || || || || || || || || || ||
differentiate objects with similar linear attenuation coeffiecents - correct answer✔✔*spatial || || || || || || || || || ||
resolution
, *sensitivity
Which of the following factors have an affect on contrast resolution - correct
|| || || || || || || || || || || || ||
answer✔✔*patient size ||
*slice thickness ||
*pixel size ||
*mAs/dose
As mAs/dose increases contrast resolution decreases - correct answer✔✔FALSE
|| || || || || || || ||
As mAs/dose increases contrast resolution INCREASES - correct answer✔✔TRUE
|| || || || || || || ||
The ability of a CT scanner to accurately image objects with similar densities is termed -
|| || || || || || || || || || || || || || || ||
correct answer✔✔*contrast resolution
|| || ||
*sensitivity
Which of the following has a direct relationship on increasing contrast resolution - correct
|| || || || || || || || || || || || || ||
answer✔✔*mAs/dose increase ||
*Slice thickness ||
For a particular CT scanner's beam quality, the linear attenuation coefficient for water is
|| || || || || || || || || || || || || ||
0.20 cm-1 and for a certain tumor is 0.21 cm-1. What is the CT number of the tumor? -
|| || || || || || || || || || || || || || || || || || ||
correct answer✔✔50. Equation (.21-.20/.21) × 1000= 50
|| || || || || ||
A CT scanner with poor contrast resolution or low sensitivity has difficulty separating -
|| || || || || || || || || || || || || ||
correct answer✔✔tissues whose linear attenuation coefficients are nearly equal
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