Exam (elaborations)
PRACTICE FOR CT BOARDS EXAM QUESTIONS WITH CORRECT ANSWERS
- Course
- Institution
PRACTICE FOR CT BOARDS EXAM QUESTIONS WITH CORRECT ANSWERS
[Show more]
Content preview
MOSBY CT REGISTRY REVIEW EXAMQUESTIONS WITH CORRECT ANSWERS
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
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
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
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
*all test results must be interpreted promptly
, Using the ACR CT accreditation phantom, module 3 is used to measure which of the
following - Answer-CT number uniformity
The following QC test should be done on a monthly basis - Answer-high contrast
resolution
The CT number at the center of a uniformly filled water phantom should ideally be -
Answer-0
The ACR CT accreditation phantom is designed to perform QC measurements of -
Answer-*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 - Answer-+-7HU or +-5
preferred
The test for the average CT number of water should be tested at - Answer-*acceptance
*daily
The ACR tolerance limit for the CT number uniformity is which of the following - Answer-
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 -
Answer-mAs
For an increase from 200 mA to 400 mA in a CT exam, the result would be to - Answer-
Increase low contrast resolution
This ability is also commonly referred to as the low contrast resolution or the sensitivity
of the CT scanner - Answer-contrast resolution
The major advantage of a CT scanner over a screen-film radiography system is -
Answer-Better low contrast discrimination
For CT images, all of the following factors improve the visibility of large, low-contrast
lesions except? - Answer-Smaller pixel sizes
As the iodine concentration ? the viscosity of the substance will ? - Answer-increase,
increase
A fluid with a high viscosity is relatively - Answer-thick and flows slowly
The viscosity of a solution may be changed by regulating - Answer-temperature
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller biggdreamer. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $19.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
75323 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now