Mosby CT Registry Review Questions
And Answers Already Graded A+ 2025|
2026
What is the smallest component of a digital image CORRECT ANSWERS pixel
How many CT numbers are assigned to each pixel in the image matrix? CORRECT
ANSWERS One
In a CT image, the CT number CORRECT ANSWERS 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
ANSWERS pixel
What is an element of the digital image CORRECT ANSWERS pixel
Which of the following influences the spatial resolution in cardiac CT imaging
CORRECT ANSWERS *detector size
*reconstruction interval
*pitch
As patient motion increases spatial resolution decreases CORRECT ANSWERS TRUE
Which is an advantage of using a small focal spot CORRECT ANSWERS increased
spatial resolution
Increasing the CT image matrix from 256x256 to 512x512 will likely improve?
CORRECT ANSWERS 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 ANSWERS 1.4 mm
Use of a bone filter, as opposed to a soft tissue filter, to reconstruct CT images would
likely improve? CORRECT ANSWERS Spatial resolution
The spatial resolution of a typical CT scanner is on the order of? CORRECT ANSWERS
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 ANSWERS 8.5
,When comparing a 512x512 matrix to a 1024x1024 matrix, the 1024x1024 matrix?
CORRECT ANSWERS 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 ANSWERS Biannually
To improve the high contrast spatial resolution of a CT study, one would increase _____
while keeping all other factors the same. CORRECT ANSWERS 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 ANSWERS 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 ANSWERS 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 ANSWERS 0
How many pixels are contained in a 1,024 matrix image? CORRECT ANSWERS D.
1,048,576
MATH 1024 X1024
It is located in a matrix and is a two dimensional representation of a voxel CORRECT
ANSWERS 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
ANSWERS pixel
What is defined as a picture element or the smallest component of the digital image
CORRECT ANSWERS 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 ANSWERS 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 ANSWERS 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 ANSWERS
*spatial resolution
,*sensitivity
Which of the following factors have an affect on contrast resolution CORRECT
ANSWERS *patient size
*slice thickness
*pixel size
*mAs/dose
As mAs/dose increases contrast resolution decreases CORRECT ANSWERS FALSE
As mAs/dose increases contrast resolution INCREASES CORRECT ANSWERS TRUE
The ability of a CT scanner to accurately image objects with similar densities is termed
CORRECT ANSWERS *contrast resolution
*sensitivity
Which of the following has a direct relationship on increasing contrast resolution
CORRECT ANSWERS *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 ANSWERS 50. Equation (.21-.20/.21) × 1000= 50
A CT scanner with poor contrast resolution or low sensitivity has difficulty separating
CORRECT ANSWERS tissues whose linear attenuation coefficients are nearly equal
What is the basic physical quantity being measured by a CT system CORRECT
ANSWERS 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? CORRECT ANSWERS +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? CORRECT ANSWERS 0.63
The contrast resolution of CT is approximately ? % CORRECT ANSWERS 0.3 to 0.6
This term describes the ability CT scanner to differentiate objects with MINIMAL
differences in attenuation coefficients CORRECT ANSWERS 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. CORRECT ANSWERS contrast resolution
, In order to pass ACR CT accreditation, the CT scanner's adult head protocol must be
within CORRECT ANSWERS 1.0
The QC test for the average CT number for water should be done CORRECT
ANSWERS Daily
The following are all basic tenets of a QC program for computed tomography scanner
CORRECT ANSWERS *QC test must be conducted regularly
*Accurate record keeping
*all test results must be interpreted promptly
Using the ACR CT accreditation phantom, module 3 is used to measure which of the
following CORRECT ANSWERS CT number uniformity
The following QC test should be done on a monthly basis CORRECT ANSWERS high
contrast resolution
The CT number at the center of a uniformly filled water phantom should ideally be
CORRECT ANSWERS 0
The ACR CT accreditation phantom is designed to perform QC measurements of
CORRECT ANSWERS *positioning accuracy and light accuracy alignment only
*CT number accuracy and slice thickness only
*low contrast resolution, CT number uniformity, and high contrast resolution
The ACR tolerance limit for the CT number accuracy for water is CORRECT ANSWERS
+-7HU or +-5 preferred
The test for the average CT number of water should be tested at CORRECT
ANSWERS *acceptance
*daily
The ACR tolerance limit for the CT number uniformity is which of the following
CORRECT ANSWERS The center CT number must be between plus or minus 7HU
plus the abdomen protocol must be used
To evaluate low contrast resolution, phantoms are scanned using different ? settings
CORRECT ANSWERS mAs
For an increase from 200 mA to 400 mA in a CT exam, the result would be to
CORRECT ANSWERS Increase low contrast resolution
This ability is also commonly referred to as the low contrast resolution or the sensitivity
of the CT scanner CORRECT ANSWERS contrast resolution
And Answers Already Graded A+ 2025|
2026
What is the smallest component of a digital image CORRECT ANSWERS pixel
How many CT numbers are assigned to each pixel in the image matrix? CORRECT
ANSWERS One
In a CT image, the CT number CORRECT ANSWERS 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
ANSWERS pixel
What is an element of the digital image CORRECT ANSWERS pixel
Which of the following influences the spatial resolution in cardiac CT imaging
CORRECT ANSWERS *detector size
*reconstruction interval
*pitch
As patient motion increases spatial resolution decreases CORRECT ANSWERS TRUE
Which is an advantage of using a small focal spot CORRECT ANSWERS increased
spatial resolution
Increasing the CT image matrix from 256x256 to 512x512 will likely improve?
CORRECT ANSWERS 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 ANSWERS 1.4 mm
Use of a bone filter, as opposed to a soft tissue filter, to reconstruct CT images would
likely improve? CORRECT ANSWERS Spatial resolution
The spatial resolution of a typical CT scanner is on the order of? CORRECT ANSWERS
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 ANSWERS 8.5
,When comparing a 512x512 matrix to a 1024x1024 matrix, the 1024x1024 matrix?
CORRECT ANSWERS 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 ANSWERS Biannually
To improve the high contrast spatial resolution of a CT study, one would increase _____
while keeping all other factors the same. CORRECT ANSWERS 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 ANSWERS 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 ANSWERS 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 ANSWERS 0
How many pixels are contained in a 1,024 matrix image? CORRECT ANSWERS D.
1,048,576
MATH 1024 X1024
It is located in a matrix and is a two dimensional representation of a voxel CORRECT
ANSWERS 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
ANSWERS pixel
What is defined as a picture element or the smallest component of the digital image
CORRECT ANSWERS 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 ANSWERS 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 ANSWERS 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 ANSWERS
*spatial resolution
,*sensitivity
Which of the following factors have an affect on contrast resolution CORRECT
ANSWERS *patient size
*slice thickness
*pixel size
*mAs/dose
As mAs/dose increases contrast resolution decreases CORRECT ANSWERS FALSE
As mAs/dose increases contrast resolution INCREASES CORRECT ANSWERS TRUE
The ability of a CT scanner to accurately image objects with similar densities is termed
CORRECT ANSWERS *contrast resolution
*sensitivity
Which of the following has a direct relationship on increasing contrast resolution
CORRECT ANSWERS *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 ANSWERS 50. Equation (.21-.20/.21) × 1000= 50
A CT scanner with poor contrast resolution or low sensitivity has difficulty separating
CORRECT ANSWERS tissues whose linear attenuation coefficients are nearly equal
What is the basic physical quantity being measured by a CT system CORRECT
ANSWERS 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? CORRECT ANSWERS +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? CORRECT ANSWERS 0.63
The contrast resolution of CT is approximately ? % CORRECT ANSWERS 0.3 to 0.6
This term describes the ability CT scanner to differentiate objects with MINIMAL
differences in attenuation coefficients CORRECT ANSWERS 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. CORRECT ANSWERS contrast resolution
, In order to pass ACR CT accreditation, the CT scanner's adult head protocol must be
within CORRECT ANSWERS 1.0
The QC test for the average CT number for water should be done CORRECT
ANSWERS Daily
The following are all basic tenets of a QC program for computed tomography scanner
CORRECT ANSWERS *QC test must be conducted regularly
*Accurate record keeping
*all test results must be interpreted promptly
Using the ACR CT accreditation phantom, module 3 is used to measure which of the
following CORRECT ANSWERS CT number uniformity
The following QC test should be done on a monthly basis CORRECT ANSWERS high
contrast resolution
The CT number at the center of a uniformly filled water phantom should ideally be
CORRECT ANSWERS 0
The ACR CT accreditation phantom is designed to perform QC measurements of
CORRECT ANSWERS *positioning accuracy and light accuracy alignment only
*CT number accuracy and slice thickness only
*low contrast resolution, CT number uniformity, and high contrast resolution
The ACR tolerance limit for the CT number accuracy for water is CORRECT ANSWERS
+-7HU or +-5 preferred
The test for the average CT number of water should be tested at CORRECT
ANSWERS *acceptance
*daily
The ACR tolerance limit for the CT number uniformity is which of the following
CORRECT ANSWERS The center CT number must be between plus or minus 7HU
plus the abdomen protocol must be used
To evaluate low contrast resolution, phantoms are scanned using different ? settings
CORRECT ANSWERS mAs
For an increase from 200 mA to 400 mA in a CT exam, the result would be to
CORRECT ANSWERS Increase low contrast resolution
This ability is also commonly referred to as the low contrast resolution or the sensitivity
of the CT scanner CORRECT ANSWERS contrast resolution
