Which of the following is a relative contraindication to CCTA?

• A. Pregnancy
• B. Allergic to iodinated contrast
• C. Morbid obesity
• D. Prior radiation therapy

Answer: (C)

Understanding contraindications to coronary CT angiography hinges on how patient factors affect safety and diagnostic quality. Morbid obesity is a relative contraindication because excessive body habitus degrades image quality and increases radiation exposure, making it harder to obtain reliable, diagnostic images of the coronary arteries. In obese patients, image noise rises and attenuation can overwhelm the scanner’s ability to visualize small vessels, so the study may be nondiagnostic or require higher radiation doses and special protocols. This is why it’s labeled relative: the exam can still be performed with precautions, but the likelihood of a good result is reduced.

In contrast, pregnancy is an absolute contraindication due to the risk of fetal radiation exposure. An allergy to iodinated contrast is a safety concern that can often be managed with premedication or alternative imaging, but it still represents a significant consideration when planning the study. Prior chest radiation isn’t a standard contraindication to CCTA.