CAMRT Radiography Practice Exam

A ring artifact on a CT image may indicate what issue?

1. Image overexposure

2. Patient movement

3. Detector malfunction

4. Incorrect windowing settings

The correct answer is: Detector malfunction

A ring artifact on a CT image is often indicative of detector malfunction. This type of artifact occurs when one or more of the CT detectors are not functioning correctly, leading to inconsistent data capture as the scanner rotates around the patient. This malfunction can manifest as a circular or ring-like pattern on the images produced, which is not representative of the actual anatomy being scanned. These artifacts are usually due to issues such as misalignment, calibration errors, or the failure of individual detectors to respond uniformly to the X-ray beams. As a result, the data collected from the malfunctioning detector can cause specific pixels in the reconstructed images to consistently display erroneous readings, creating the characteristic ring appearance. In contrast, other options relate to different issues: image overexposure generally results in overly bright images with reduced contrast, patient movement would typically cause blurring or streaking rather than a defined ring pattern, and incorrect windowing settings affect the visualization of the image but do not create structural artifacts like a ring. Thus, problems associated with the detector are primarily responsible for the appearance of ring artifacts in CT imaging.