Which two statements correctly describe data acquisition in helical scanning?

The correct statement describing data acquisition in helical scanning is that the patient table is in constant motion. In helical (or spiral) scanning, the patient table moves continuously during the data acquisition process, allowing the x-ray tube to rotate around the patient in a helical trajectory. This method enables the simultaneous collection of multiple slices as the patient moves through the scanner, resulting in faster scan times and improved image quality. The continuous motion of the table allows for a more comprehensive data set to be captured without the need for the table to stop between each exposure, which is a characteristic feature of helical scanning.

In contrast, if the table were to move only between x-ray exposures, it would more closely resemble traditional sequential (or step-and-shoot) scanning rather than the efficient, continuous acquisition of data that characterizes helical scanning. The other options imply that data acquisition occurs in less efficient or conventional methods, highlighting why the constant motion of the patient table is a defining aspect of helix-based data acquisition.