MOSBY CT REGISTRY REVIEW EXAM WITH
HIGHEST PROBILITY 100%PASS.
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
HIGHEST PROBILITY 100%PASS.
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
