Mosby CT Registry LATTEST UPDATE QUESTIONS AND
ANSWERS 100% CORRECT 2024-2025
What is the smallest component of a digital image - ANSWER: pixel
How many CT numbers are assigned to each pixel in the image matrix? - ANSWER: One
In a CT image, the CT number - 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 - ANSWER: pixel
What is an element of the digital image - ANSWER: pixel
Which of the following influences the spatial resolution in cardiac CT imaging - ANSWER: *detector
size
*reconstruction interval
*pitch
As patient motion increases spatial resolution decreases - ANSWER: TRUE
Which is an advantage of using a small focal spot - ANSWER: increased spatial resolution
Increasing the CT image matrix from 256x256 to 512x512 will likely improve? - 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? - ANSWER: 1.4 mm
Use of a bone filter, as opposed to a soft tissue filter, to reconstruct CT images would likely improve?
- ANSWER: Spatial resolution
The spatial resolution of a typical CT scanner is on the order of? - ANSWER: 1 mm
,Mosby CT Registry LATTEST UPDATE QUESTIONS AND
ANSWERS 100% CORRECT 2024-2025
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? - ANSWER: 8.5
When comparing a 512x512 matrix to a 1024x1024 matrix, the 1024x1024 matrix? - 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 - ANSWER: Biannually
To improve the high contrast spatial resolution of a CT study, one would increase _____ while
keeping all other factors the same. - 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 - 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? - 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? - ANSWER: 0
How many pixels are contained in a 1,024 matrix image? - ANSWER: D. 1,048,576
MATH 1024 X1024
It is located in a matrix and is a two dimensional representation of a voxel - 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 - ANSWER: pixel
,Mosby CT Registry LATTEST UPDATE QUESTIONS AND
ANSWERS 100% CORRECT 2024-2025
What is defined as a picture element or the smallest component of the digital image - 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. - 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? -
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 - ANSWER: *spatial resolution
*sensitivity
Which of the following factors have an affect on contrast resolution - ANSWER: *patient size
*slice thickness
*pixel size
*mAs/dose
As mAs/dose increases contrast resolution decreases - ANSWER: FALSE
As mAs/dose increases contrast resolution INCREASES - ANSWER: TRUE
The ability of a CT scanner to accurately image objects with similar densities is termed - ANSWER:
*contrast resolution
*sensitivity
Which of the following has a direct relationship on increasing contrast resolution - ANSWER:
*mAs/dose increase
*Slice thickness
, Mosby CT Registry LATTEST UPDATE QUESTIONS AND
ANSWERS 100% CORRECT 2024-2025
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? - ANSWER: 50. Equation
(.21-.20/.21) × 1000= 50
A CT scanner with poor contrast resolution or low sensitivity has difficulty separating - ANSWER:
tissues whose linear attenuation coefficients are nearly equal
What is the basic physical quantity being measured by a CT system - ANSWER: Linear attenuation
coefficient
Assume the linear attenuation coefficient is 0.20 cm-1 for water and 0.40 cm-1 for tissue within a
given voxel. What is the CT number in Hounsfield units for the pixel representing this voxel? -
ANSWER: +1,000....Equation { (.4-.2) /.2} x 1000
What fraction of monoenergetic x-rays will be absorbed by a 20-cm thick material having a linear
attenuation coefficient of 0.05 cm-1? - ANSWER: 0.63
The contrast resolution of CT is approximately ? % - ANSWER: 0.3 to 0.6
This term describes the ability CT scanner to differentiate objects with MINIMAL differences in
attenuation coefficients - ANSWER: contrast resolution
What is the term for resolution of a CT scanner referred to as the system's ability to differentiate
objects with SIMILAR densities. - ANSWER: contrast resolution
In order to pass ACR CT accreditation, the CT scanner's adult head protocol must be within -
ANSWER: 1.0
The QC test for the average CT number for water should be done - ANSWER: Daily
The following are all basic tenets of a QC program for computed tomography scanner - ANSWER:
*QC test must be conducted regularly
*Accurate record keeping
ANSWERS 100% CORRECT 2024-2025
What is the smallest component of a digital image - ANSWER: pixel
How many CT numbers are assigned to each pixel in the image matrix? - ANSWER: One
In a CT image, the CT number - 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 - ANSWER: pixel
What is an element of the digital image - ANSWER: pixel
Which of the following influences the spatial resolution in cardiac CT imaging - ANSWER: *detector
size
*reconstruction interval
*pitch
As patient motion increases spatial resolution decreases - ANSWER: TRUE
Which is an advantage of using a small focal spot - ANSWER: increased spatial resolution
Increasing the CT image matrix from 256x256 to 512x512 will likely improve? - 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? - ANSWER: 1.4 mm
Use of a bone filter, as opposed to a soft tissue filter, to reconstruct CT images would likely improve?
- ANSWER: Spatial resolution
The spatial resolution of a typical CT scanner is on the order of? - ANSWER: 1 mm
,Mosby CT Registry LATTEST UPDATE QUESTIONS AND
ANSWERS 100% CORRECT 2024-2025
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? - ANSWER: 8.5
When comparing a 512x512 matrix to a 1024x1024 matrix, the 1024x1024 matrix? - 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 - ANSWER: Biannually
To improve the high contrast spatial resolution of a CT study, one would increase _____ while
keeping all other factors the same. - 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 - 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? - 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? - ANSWER: 0
How many pixels are contained in a 1,024 matrix image? - ANSWER: D. 1,048,576
MATH 1024 X1024
It is located in a matrix and is a two dimensional representation of a voxel - 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 - ANSWER: pixel
,Mosby CT Registry LATTEST UPDATE QUESTIONS AND
ANSWERS 100% CORRECT 2024-2025
What is defined as a picture element or the smallest component of the digital image - 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. - 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? -
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 - ANSWER: *spatial resolution
*sensitivity
Which of the following factors have an affect on contrast resolution - ANSWER: *patient size
*slice thickness
*pixel size
*mAs/dose
As mAs/dose increases contrast resolution decreases - ANSWER: FALSE
As mAs/dose increases contrast resolution INCREASES - ANSWER: TRUE
The ability of a CT scanner to accurately image objects with similar densities is termed - ANSWER:
*contrast resolution
*sensitivity
Which of the following has a direct relationship on increasing contrast resolution - ANSWER:
*mAs/dose increase
*Slice thickness
, Mosby CT Registry LATTEST UPDATE QUESTIONS AND
ANSWERS 100% CORRECT 2024-2025
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? - ANSWER: 50. Equation
(.21-.20/.21) × 1000= 50
A CT scanner with poor contrast resolution or low sensitivity has difficulty separating - ANSWER:
tissues whose linear attenuation coefficients are nearly equal
What is the basic physical quantity being measured by a CT system - ANSWER: Linear attenuation
coefficient
Assume the linear attenuation coefficient is 0.20 cm-1 for water and 0.40 cm-1 for tissue within a
given voxel. What is the CT number in Hounsfield units for the pixel representing this voxel? -
ANSWER: +1,000....Equation { (.4-.2) /.2} x 1000
What fraction of monoenergetic x-rays will be absorbed by a 20-cm thick material having a linear
attenuation coefficient of 0.05 cm-1? - ANSWER: 0.63
The contrast resolution of CT is approximately ? % - ANSWER: 0.3 to 0.6
This term describes the ability CT scanner to differentiate objects with MINIMAL differences in
attenuation coefficients - ANSWER: contrast resolution
What is the term for resolution of a CT scanner referred to as the system's ability to differentiate
objects with SIMILAR densities. - ANSWER: contrast resolution
In order to pass ACR CT accreditation, the CT scanner's adult head protocol must be within -
ANSWER: 1.0
The QC test for the average CT number for water should be done - ANSWER: Daily
The following are all basic tenets of a QC program for computed tomography scanner - ANSWER:
*QC test must be conducted regularly
*Accurate record keeping
