What QC test creates a graph of attenuation coefficients alongside the CT number during the scan?

The quality control (QC) test that creates a graph of attenuation coefficients alongside the CT number during the scan is known as linearity. This test is essential in ensuring that the CT numbers accurately reflect the linear relationship between the measured attenuation of materials and the corresponding CT numbers. Essentially, linearity evaluates how well the CT system can convert the physical properties of materials — specifically their attenuation coefficients — into digital values that are represented as CT numbers.

By conducting this test, technicians can identify any discrepancies in the CT numbers assigned to various materials, which could indicate issues with the calibration of the CT scanner. If the linearity is not maintained, it may lead to misinterpretation of images and inaccuracies in diagnosis.

In contrast, the other QC tests focus on different aspects of the imaging system. Accuracy assesses how close the CT numbers are to the true values, uniformity examines the consistency of the CT numbers across the image, and contrast resolution determines the ability to differentiate between structures with similar densities. While all these tests are important for maintaining the performance of the CT system, it is linearity that specifically correlates attenuation coefficients with CT numbers in a graphical format.