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CT PHYSICS & SCANNER TECHNOLOGY (Q1–20)
1. Increasing tube current (mA) primarily affects:
A. Spatial resolution
B. Image noise
C. Temporal resolution
D. Beam hardening
Answer: B — Tube current controls the number of photons, which primarily determines
image noise .
2. Which scanner architecture provides the highest spatial resolution for coronary
imaging?
A. 64-slice single-source CT
B. Dual-source CT with 0.33 mm detector rows
C. Wide-detector 256-slice CT
D. Photon-counting CT (PCCT)
Answer: D — Photon-counting detectors eliminate electronic noise and enable sub-0.3 mm
isotropic resolution .
3. Temporal resolution in single-source CT is approximately:
A. The full gantry rotation time
B. Half the gantry rotation time
C. Quarter the gantry rotation time
D. Independent of gantry rotation
Answer: B — Half-scan reconstruction uses 180° of data, yielding temporal resolution =
rotation time / 2 .
4. Which reconstruction technique reduces image noise while maintaining spatial
resolution?
A. Filtered back-projection
B. Iterative reconstruction
C. Simple back-projection
D. Longitudinal interpolation
Answer: B — Iterative reconstruction reduces noise compared to filtered back-projection .
5. The main advantage of dual-source CT for cardiac imaging is:
A. Lower radiation dose
B. Improved temporal resolution
C. Higher spatial resolution
D. Better contrast resolution
Answer: B — Two X-ray tubes enable quarter-rotation reconstruction, improving temporal
resolution .
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6. Which parameter most directly determines temporal resolution in MDCT?
A. Tube voltage (kV)
B. Gantry rotation time
C. Slice thickness
D. Field of view
Answer: B — Temporal resolution = gantry rotation time / 2 for single-source CT .
7. Spectral CT (dual-energy) primarily enables:
A. Faster gantry rotation
B. Material decomposition and iodine quantification
C. Elimination of motion artifacts
D. Direct FFR measurement
Answer: B — Dual-energy CT can separate materials based on attenuation profiles at
different energies .
8. The primary determinant of spatial resolution in CT is:
A. Tube current
B. Detector element size
C. Gantry rotation speed
D. Reconstruction kernel
Answer: B — Smaller detector elements improve spatial resolution .
9. Which artifact is caused by high-density objects like metal clips or dense calcification?
A. Motion artifact
B. Beam hardening (streak) artifact
C. Partial volume averaging
D. Step artifact
Answer: B — High-density objects absorb lower-energy photons, causing streaks .
10. The "ALARA" principle in Cardiac CT stands for:
A. As Low As Reasonably Achievable
B. Always Lower All Radiation Amounts
C. As Little As Reasonably Allowed
D. Accurate Levels And Radiation Assessment
Answer: A — Fundamental safety principle to minimize radiation exposure .
11. Effective radiation dose in cardiac CT is measured in:
A. Hounsfield Units (HU)
B. Millisieverts (mSv)
C. Millimeters (mm)
D. Beats per minute (bpm)
Answer: B — mSv is the unit for effective dose .
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12. Which kVp setting is most appropriate for a thin patient to reduce dose and increase
contrast?
A. 80 kVp
B. 120 kVp
C. 140 kVp
D. 100 kVp
Answer: A — Lower kVp (80–100) increases iodine signal and reduces radiation in smaller
patients .
13. A "voxel" in CT refers to:
A. A 2D pixel
B. A 3D volume element
C. The speed of the gantry
D. The contrast concentration
Answer: B — Voxel is the 3D unit representing volume in a CT image .
14. Which scan mode acquires data continuously while the table moves?
A. Step-and-shoot
B. Spiral (helical)
C. Stationary full-coverage
D. Dynamic acquisition
Answer: B — Spiral mode acquires data continuously during table movement .
15. Prospective ECG-triggered CT protocols are preferred because they:
A. Allow retrospective reconstruction
B. Reduce radiation dose
C. Eliminate motion artifacts completely
D. Provide dynamic flow information
Answer: B — Prospective triggering acquires data only during a predefined phase, reducing
dose .
16. Which reconstruction parameter affects the trade-off between noise and spatial
resolution?
A. Slice thickness
B. Tube voltage
C. Pitch
D. Contrast injection rate
Answer: A — Thinner slices improve spatial resolution but increase noise .
17. The primary purpose of ECG editing in cardiac CT is to:
A. Reduce radiation dose
B. Correct for arrhythmia-related artifacts
C. Improve contrast enhancement
CT PHYSICS & SCANNER TECHNOLOGY (Q1–20)
1. Increasing tube current (mA) primarily affects:
A. Spatial resolution
B. Image noise
C. Temporal resolution
D. Beam hardening
Answer: B — Tube current controls the number of photons, which primarily determines
image noise .
2. Which scanner architecture provides the highest spatial resolution for coronary
imaging?
A. 64-slice single-source CT
B. Dual-source CT with 0.33 mm detector rows
C. Wide-detector 256-slice CT
D. Photon-counting CT (PCCT)
Answer: D — Photon-counting detectors eliminate electronic noise and enable sub-0.3 mm
isotropic resolution .
3. Temporal resolution in single-source CT is approximately:
A. The full gantry rotation time
B. Half the gantry rotation time
C. Quarter the gantry rotation time
D. Independent of gantry rotation
Answer: B — Half-scan reconstruction uses 180° of data, yielding temporal resolution =
rotation time / 2 .
4. Which reconstruction technique reduces image noise while maintaining spatial
resolution?
A. Filtered back-projection
B. Iterative reconstruction
C. Simple back-projection
D. Longitudinal interpolation
Answer: B — Iterative reconstruction reduces noise compared to filtered back-projection .
5. The main advantage of dual-source CT for cardiac imaging is:
A. Lower radiation dose
B. Improved temporal resolution
C. Higher spatial resolution
D. Better contrast resolution
Answer: B — Two X-ray tubes enable quarter-rotation reconstruction, improving temporal
resolution .
, 2
6. Which parameter most directly determines temporal resolution in MDCT?
A. Tube voltage (kV)
B. Gantry rotation time
C. Slice thickness
D. Field of view
Answer: B — Temporal resolution = gantry rotation time / 2 for single-source CT .
7. Spectral CT (dual-energy) primarily enables:
A. Faster gantry rotation
B. Material decomposition and iodine quantification
C. Elimination of motion artifacts
D. Direct FFR measurement
Answer: B — Dual-energy CT can separate materials based on attenuation profiles at
different energies .
8. The primary determinant of spatial resolution in CT is:
A. Tube current
B. Detector element size
C. Gantry rotation speed
D. Reconstruction kernel
Answer: B — Smaller detector elements improve spatial resolution .
9. Which artifact is caused by high-density objects like metal clips or dense calcification?
A. Motion artifact
B. Beam hardening (streak) artifact
C. Partial volume averaging
D. Step artifact
Answer: B — High-density objects absorb lower-energy photons, causing streaks .
10. The "ALARA" principle in Cardiac CT stands for:
A. As Low As Reasonably Achievable
B. Always Lower All Radiation Amounts
C. As Little As Reasonably Allowed
D. Accurate Levels And Radiation Assessment
Answer: A — Fundamental safety principle to minimize radiation exposure .
11. Effective radiation dose in cardiac CT is measured in:
A. Hounsfield Units (HU)
B. Millisieverts (mSv)
C. Millimeters (mm)
D. Beats per minute (bpm)
Answer: B — mSv is the unit for effective dose .
, 3
12. Which kVp setting is most appropriate for a thin patient to reduce dose and increase
contrast?
A. 80 kVp
B. 120 kVp
C. 140 kVp
D. 100 kVp
Answer: A — Lower kVp (80–100) increases iodine signal and reduces radiation in smaller
patients .
13. A "voxel" in CT refers to:
A. A 2D pixel
B. A 3D volume element
C. The speed of the gantry
D. The contrast concentration
Answer: B — Voxel is the 3D unit representing volume in a CT image .
14. Which scan mode acquires data continuously while the table moves?
A. Step-and-shoot
B. Spiral (helical)
C. Stationary full-coverage
D. Dynamic acquisition
Answer: B — Spiral mode acquires data continuously during table movement .
15. Prospective ECG-triggered CT protocols are preferred because they:
A. Allow retrospective reconstruction
B. Reduce radiation dose
C. Eliminate motion artifacts completely
D. Provide dynamic flow information
Answer: B — Prospective triggering acquires data only during a predefined phase, reducing
dose .
16. Which reconstruction parameter affects the trade-off between noise and spatial
resolution?
A. Slice thickness
B. Tube voltage
C. Pitch
D. Contrast injection rate
Answer: A — Thinner slices improve spatial resolution but increase noise .
17. The primary purpose of ECG editing in cardiac CT is to:
A. Reduce radiation dose
B. Correct for arrhythmia-related artifacts
C. Improve contrast enhancement
