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COMPUTED TOMOGRAPHY > CT - MIDTERM L2 > Flashcards

CT - MIDTERM L2 Flashcards

1
Q

This is collimated to pass only through the slice of interest

A

Pre-patient Beam

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2
Q

Detected photon inversity is converted to ______ electrical signal

A

Analog

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2
Q

The pre-patient beam is shaped by a _______ for uniformity

A

Special Bow Tie Filter

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2
Q

Which is the part of the beam falling onto a single detector

A

CT Ray

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2
Q

TRUE OR FALSE

Each CT Ray attenuated by patient is projected onto one detector

A

TRUE

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2
Q

This is the number of simultaneously collected rays

A

CT View

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3
Q

Spiral geometry/rotation of the CT Tube requires ______ technology

A

Slip Ring

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4
Q

TRUE OR FALSE

Continuous scanning means that heat will be added to tube slower

A

FALSE

Continuous scanning means that heat will be added to tube FASTER

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5
Q

What are the considerations for Geometry in terms of Improving Quality and Detection in CT (6):

A
  1. Smaller Detectors
  2. Smaller Focal Spot
  3. Larger Focus-detector Distance
  4. Smaller Patient-Detector Distance
  5. Thinner Slices
  6. Less Patient Variation Over Slice Thickness Distance
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6
Q

X-ray tube and detectors rotate around the patient, taking multiple measurements from one angle only. As the X-ray tube and detectors rotate, the patient moves through the scanner in small increments, allowing for the creation of multiple slices through different parts of the body

A. First Statement is Correct; Second Statement is Incorrect

B. First Statement is Incorrect; Second Statement is Correct

C. Both Statements are Correct

D. None of the Statements are Correct

A

B. First Statement is Incorrect; Second Statement is Correct

(X-ray tube and detectors rotate around the patient, taking multiple measurements from VARIOUS ANGLES. As the X-ray tube and detectors rotate, the patient moves through the scanner in small increments, allowing for the creation of multiple slices through different parts of the body.)

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7
Q

Generated sets of data from collected data of detectors at different angles is called _____

A

Projection Data

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8
Q

TRUE OR FALSE

The more projection angles and data points that are collected, the lower the image quality and resolution.

A

FALSE

The more projection angles and data points that are collected, the HIGHER the image quality and resolution.

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9
Q

The process involves converting the raw projection data into interpretable
images using specialized algorithms.

A

Reconstruction of Data

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10
Q

A process where the projection data is mathematically “reversed” to simulate the X-ray paths back through the body,

A

Back-projection

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10
Q

It uses a filter to modify the back-projected data, reducing blurring and producing sharper images

A

Filtered Back-projection (FBP)

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11
Q

These are techniques that repeatedly refine the image through multiple iterations,
improving the accuracy of the reconstructed image.

A

Iterative Techniques (IR)

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12
Q

Enumerate the four (4) Factors Affecting Data Acquisition:

A
  1. X-ray Tube and Detector Sensitivity
  2. Slice Thickness
  3. Scan Time
  4. Radiation Dose
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12
Q

A radiograph may have an unintended _______ that may result to CT artifacts

A

Optical Density

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13
Q

CT Numbers / HU may display ______, causing artifacts in a CT image

A

Systematic Discrepancy

14
Q

CT images may also have an unwanted ______ that may also be considered as artifact/s.

A

Aberration

14
Q

This is a CT artifact due to an inconsistency in a single measurement

15
Q

It is a CT artifact due to a group of channels or views deviating gradually from the true measurement

15
Q

This is caused by Patient movement, Presence of metallic materials

A

Patient-based Artifacts

16
Q

This is a CT artifact due to helical reconstruction

A

Distortion

16
It is a CT artifact due to errors in an individual detector calibration
Rings
16
This is caused by image reconstruction process
Helical and Multisection Artifacts
16
This is caused by imperfections in scanner function
Scanner-based Artifacts
16
What are the four (4) Categories of CT Artifacts:
1. Physics-based Artifacts 2. Patient-based Artifacts 3. Scanner-based Artifacts 4. Helical and Multisection Artifacts
17
This is caused by physical processes involved in the acquisition of CT data
Physics-based Artifacts
17
These are artifacts caused by the polychromatic nature of the x-ray beam with increased mean energy of the x-ray beam when it passes through an object
Beam-Hardening Artifact
17
The beam is hardened more in the MIDDLE PORTION of an object than those in the edges, making the image appear darker than the periphery
Cupping Artifact
18
These appear between two dense objects that may be caused by metals, beam hardening, poisson noise, patient motion, and edge effecrs
Streak and Dark Band Artifacts
19
This is caused by anatomy / variety of tissue types being contained within a single voxel that causes a distortion of signal intensity
Partial Volume Artifacts
20
This is caused by high x-ray attenuation that may become as a potential source of streaking artifacts, resulting into insufficient x-ray photons that reach the detector
Photon Starvation Artifacts
20
This is due misregistration by the computer of information relating to sharp edges and small objects, manifested as two large intervals between projections resulting into view aliasing
Under Sampling Artifacts
21
This is caused by the presence of metal object in the scan field
Metal Artifacts
22
It is caused by involuntary and voluntary movement of patients during the scan
Motion Artifacts
23
This is due to a portion of anatomy that lies outside the scan FOV, producing incomplete information of the anatomy by the computer
Incomplete Projection
24
Ring artifacts are seen in what generation of CT Scanners ?
Third (3rd)
25
The x-ray beam becomes cone-shaped rather than fan-shaped due to increased number of sections acquired per rotation
Cone Beam Effect
26
These are SERRATIONS on coronal or sagittal reformats seen with helical and multidetector row CT
Stair Step Artifacts
26
These are PERIODIC STRIPES of more or less noise at the image periphery seen on coronal or sagittal reformats
Zebra Artifacts
27
Which of the following is a Helical CT Artifacts ? A. Cone Beam Effect B. Stair Step Artifacts C. Zebra Artifacts D. NOTA
A. Cone Beam Effect
28
Which of the following is a Multi-Section CT artifact ? A. Cone Beam Effect B. Stair Step Artifacts C. Zebra Artifacts D. NOTA
Either B or C
29
The following are patient-based artifacts EXCEPT: A. Metallic Materials B. Patient Motion C. Incomplete Projection D. Ring Artifacts
D. Ring Artifacts

COMPUTED TOMOGRAPHY (4 decks)

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