QCM : Cardiac CT Imaging Techniques — 9 questions

Questions et réponses du QCM

1. What is the primary advantage of prospective ECG gating in cardiac CT imaging?

It eliminates the need for contrast agents.
It provides higher temporal resolution than retrospective gating.
It allows for functional assessment of the heart.
It reduces radiation dose by triggering scans during specific cardiac phases.

It reduces radiation dose by triggering scans during specific cardiac phases.

Explication

Prospective ECG gating reduces radiation exposure by triggering the scan only during a specific phase of the cardiac cycle, typically when motion artifacts are minimized. This targeted approach results in a lower dose compared to retrospective gating, which continuously scans and reconstructs images over multiple cardiac cycles.

2. What is the primary advantage of prospective ECG gating in cardiac CT imaging?

It reduces radiation dose.
It provides functional assessment data.
It improves temporal resolution.
It eliminates the need for contrast agents.

It reduces radiation dose.

Explication

Prospective ECG gating effectively reduces radiation exposure by only acquiring images during a specific cardiac phase, unlike retrospective gating which continuously acquires data.

3. Why is it recommended to lower the heart rate below 65 bpm before a cardiac CT scan?

To decrease the need for contrast agents.
To reduce motion artifacts and improve image quality.
To shorten the scan time.
To improve the contrast enhancement.

To reduce motion artifacts and improve image quality.

Explication

A heart rate below 65 bpm minimizes cardiac motion during imaging, reducing motion artifacts and resulting in clearer, higher-quality images. Beta-blockers are often used to achieve this target heart rate, especially in patients with higher resting heart rates.

4. Which heart rate is considered optimal for obtaining high-quality cardiac CT images?

Above 75 bpm
Between 65 and 75 bpm
Less than 65 bpm
Exactly 70 bpm

Less than 65 bpm

Explication

A heart rate below 65 bpm is optimal as it reduces motion artifacts and improves image clarity, especially in non-ECG-gated scans.

5. Which technological advancement significantly improves temporal resolution in cardiac CT imaging?

Increased mA settings.
Wide-detector CT technology.
Dual-source CT technology.
Use of higher kVp settings.

Dual-source CT technology.

Explication

Dual-source CT technology employs two X-ray sources and detectors, which allows for a faster gantry rotation and thus improves temporal resolution to approximately 75 ms. This enhancement is crucial for reducing motion artifacts, especially in patients with higher heart rates.

6. How does dual-source CT improve imaging at high heart rates?

By increasing radiation dose.
By halving the temporal resolution to approximately 75 ms.
By decreasing the amount of contrast needed.
By extending scan time.

By halving the temporal resolution to approximately 75 ms.

Explication

Dual-source CT uses two x-ray tubes and detectors, halving the temporal resolution to about 75 ms, which helps minimize motion artifacts during high heart rate scans.

7. Why is timing of contrast bolus critical in cardiac CT imaging?

It ensures the contrast peaks at 15-20 seconds for optimal coronary artery visualization.
It prevents contrast from binding to cardiac tissue.
It reduces the total amount of contrast needed.
It diminishes motion artifacts from rapid heartbeats.

It ensures the contrast peaks at 15-20 seconds for optimal coronary artery visualization.

Explication

Timing the contrast bolus so that peak arterial enhancement occurs at 15-20 seconds is essential to maximize visualization of coronary arteries.

8. What is one benefit of using wide-detector CT in cardiac imaging?

It allows entire heart coverage in a single rotation.
It increases the radiation dose.
It requires a higher heart rate for proper imaging.
It eliminates the need for contrast agents.

It allows entire heart coverage in a single rotation.

Explication

Wide-detector CT captures the whole heart in a single rotation, reducing scan time and motion artifacts, facilitating faster imaging.

9. Which of the following techniques can aid in dose reduction during cardiac CT scans?

ECG-based dose modulation, lower kVp/mA, iterative reconstruction algorithms.
Increasing both kVp and mA.
Using retrospective gating without ECG modification.
Administering higher doses of contrast.

ECG-based dose modulation, lower kVp/mA, iterative reconstruction algorithms.

Explication

Dose reduction strategies include ECG-based modulation, lowering kVp and mA, and using iterative reconstruction algorithms to maintain image quality with less radiation exposure.

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ECG gating — types?

Prospective reduces dose; retrospective allows functional data.

ECG gating — purpose?

Synchronizes image with cardiac cycle.

Optimal heart rate — threshold?

Below 65 bpm for best image quality.

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