When the pitch of a CT scan is greater than 1, what does it indicate about the table movement?

When the pitch of a CT scan is greater than 1, it indicates that the table moves more than the beam width during the rotation of the x-ray tube. Pitch is defined as the ratio of the table movement to the beam width for a single rotation of the x-ray tube; a pitch greater than 1 means the distance the table moves in one complete rotation exceeds the width of the x-ray beam.

For example, if the CT scanner has a beam width of 5 mm and the pitch is set at 1.5, it means that for each complete 360-degree rotation of the x-ray tube, the table advances 7.5 mm (1.5 times the beam width). This increased movement leads to increased coverage of the anatomy being scanned in less time but can also result in decreased image quality due to potential under-sampling of the tissues, as there may be gaps in the data collected.

This relationship clarifies why the correct answer is associated with the table moving more than the beam width when the pitch exceeds 1.