Which of the following is identified as a daily QC test for a CT scanner?

The identification of CT number accuracy as a daily quality control (QC) test for a CT scanner is significant because it directly impacts the reliability and consistency of the imaging results produced by the scanner. CT number accuracy, often referred to as Hounsfield unit (HU) accuracy, ensures that the scanner produces the correct values for different tissue types. This is crucial for proper diagnosis, as these values help radiologists differentiate between various structures and conditions in the body.

Daily verification of CT number accuracy involves scanning a standardized phantom and ensuring that the measured values correspond to the expected Hounsfield units. If the numbers fall outside acceptable ranges, it indicates that the scanner may need servicing or calibration, preventing potential misdiagnoses due to inaccurate imaging data.

While the other options mentioned play important roles in the overall quality assurance of a CT scanner, they do not typically require daily assessment. For instance, exposure time calibration is often performed less frequently and focuses more on the temporal aspect of imaging rather than the direct output values of the scan. Geometric distortion assessment and contrast resolution evaluations are critical for ensuring image quality but are usually conducted on a weekly or monthly basis rather than daily. Thus, daily monitoring of CT number accuracy ensures ongoing reliability and effectiveness in clinical imaging settings.