Computed Tomography Test Computed Tomography (CT) 2 — Questions and Answers
Question 1: What is the primary purpose of a CT gantry tilt?
- To increase patient comfort
- To align the scan plane with anatomical structures while avoiding radiation-sensitive organs (Correct answer)
- To improve contrast resolution
- To reduce scan time
Correct answer: To align the scan plane with anatomical structures while avoiding radiation-sensitive organs
Gantry tilt allows the scan plane to be angled relative to the patient's body axis to align with anatomy or minimize dose to sensitive structures like the lens of the eye.
Question 2: Which CT image reconstruction algorithm produces the sharpest edges but introduces the most noise?
- Soft tissue kernel
- Standard kernel
- Bone (sharp) kernel (Correct answer)
- Lung kernel
Correct answer: Bone (sharp) kernel
Bone or high-frequency kernels enhance edge detail for structures like cortical bone but amplify image noise compared to smooth kernels.
Question 3: In CT angiography, what timing method uses real-time monitoring of contrast arrival in a target vessel?
- Test bolus technique
- Bolus tracking (SmartPrep/Care Bolus) (Correct answer)
- Fixed delay scanning
- Saline flush technique
Correct answer: Bolus tracking (SmartPrep/Care Bolus)
Bolus tracking monitors a region of interest in real time and automatically triggers scanning when contrast attenuation reaches a preset threshold.
Question 4: What does the term 'pitch' refer to in helical CT?
- The angle of the X-ray beam
- Table movement per rotation divided by total beam collimation (Correct answer)
- The number of detector rows
- The rotation speed of the gantry
Correct answer: Table movement per rotation divided by total beam collimation
Pitch is defined as table feed per 360° gantry rotation divided by the total X-ray beam width (collimation), affecting coverage speed and dose.
Question 5: Which parameter most directly controls CT image noise?
- kVp
- mAs (Correct answer)
- FOV
- Reconstruction interval
Correct answer: mAs
mAs (milliampere-seconds) determines the quantity of X-ray photons produced; higher mAs means more photons, less quantum noise, and better image quality.
Question 6: A patient's kidneys appear hyperdense on a non-contrast CT. What is the most likely cause?
- Renal cell carcinoma
- Simple renal cysts
- Recent IV contrast administration or nephrocalcinosis (Correct answer)
- Hydronephrosis
Correct answer: Recent IV contrast administration or nephrocalcinosis
Hyperdense kidneys on non-contrast CT are most commonly due to residual contrast from a recent scan or calcifications (nephrocalcinosis).
Question 7: What is the advantage of using a smaller CT field of view (FOV)?
- Faster scan time
- Reduced patient dose
- Improved spatial resolution for the targeted anatomy (Correct answer)
- Wider anatomical coverage
Correct answer: Improved spatial resolution for the targeted anatomy
A smaller FOV assigns more pixels per unit area, increasing spatial resolution and displaying finer anatomical detail in the region of interest.
Computed Tomography Test Computed Tomography (CT) 2
What is the primary purpose of a CT gantry tilt?