Question

Cardiac images obtained with conventional CT may not be precise due to:

• A. Limited number of detectors
• B. Size of the detectors
• C. Power line interference
• D. Motion artifact

Hint:

In medical imaging physics: - Anatomical Motion during projection acquisition causes Motion Artifacts (blurring and streaks). - Because conventional CT scanners have slow rotation speeds relative to a beating heart, they blur cardiac structural details. Resolving coronary arteries clearly requires ultra-fast rotation times or ECG-gated acquisition loops.

Answer 1

The Correct Option is D

Concept: Computed Tomography relies on rotating an x-ray tube and detector array around a patient to gather multiple projections from different angles. To reconstruct sharp, mathematically accurate cross-sectional images, the target organ must remain completely still while the scanner collects these projections. If the target structure moves during data acquisition, the projection paths blur, introducing severe structural streak distortions known as motion artifacts.

Step 1: Assessing the challenge of cardiac imaging.
The human heart is a highly dynamic organ that beats continuously, causing rapid structural movement of the myocardium and coronary arteries throughout the cardiac cycle. Conventional, older generation CT scanners have relatively slow gantry rotation speeds (taking $1 \text{ to } 2\text{ seconds}$ per revolution). Because this acquisition time is significantly longer than a single heartbeat, the heart moves substantially while the scanner collects its projections, resulting in severe motion blurring.

Step 2: Reviewing modern technological solutions.
To overcome these cardiac motion artifacts, modern clinical imaging systems utilize specialized high-speed advancements:
• Ultra-fast gantry rotation speeds ($< 0.25\text{ seconds}$ per rotation).
• Dual-Source CT systems that deploy two paired x-ray tubes and detectors at $90^\circ$ angles to cut the required scan time in half.
• ECG Gating software that cross-references data acquisition with a simultaneous ECG signal, ensuring the scanner only uses projections collected during the quietest part of the heartbeat (diastole). Conventional CT systems lack these high-speed stabilization mechanisms, making motion artifacts the primary cause of poor precision in cardiac imaging. This matches Option (D).