Motion artifact in a CT image can be attributed to which two factors?

Motion artifacts in a CT image primarily arise from any movement during the scanning process. Breathing is a significant contributor to these artifacts because it introduces changes in the position of the diaphragm and the surrounding anatomical structures throughout the scan. If a patient breathes during a CT imaging session, the resulting images can exhibit blurring or streaking, leading to diagnostic challenges.

The other factors listed do involve aspects that can impact image quality, but not all directly cause motion artifacts in the same way. For example, metallic implants usually lead to beam hardening or scattering effects rather than motion artifacts. Peristalsis, the movement of the intestines, can also contribute to artifacts, but it is generally less pronounced in many imaging studies compared to respiratory motion. Miscalibrated detectors would lead to image quality degradation through issues such as noise or inaccuracies in the representation of tissue densities rather than through motion effects. Thus, breathing stands out as the most direct and common cause of motion artifacts in CT imaging.