What scanning mode is appropriate for imaging the entire Circle of Willis in one x-ray exposure?

Helical scanning is the most appropriate mode for imaging the entire Circle of Willis in one x-ray exposure because it allows for continuous rotation of the x-ray tube around the patient while the table moves linearly. This results in a spiral or helical path of data acquisition, enabling the capture of a complete dataset in a single breath-hold or scan event.

This technique is particularly advantageous when imaging vascular structures like the Circle of Willis, as it provides high-quality images with improved temporal resolution and a reduced risk of motion artifacts. It also allows for the entire area to be captured progressively and efficiently, which is essential for thorough anatomical visualization.

Axial scanning, in contrast, acquires images slice by slice, which could require multiple exposures and breath-holds that may not capture the entire area in one continuous motion. Volume scanning, while effective, is a term often used interchangeably with helical but may not specify the benefits and efficiency of the process as clearly as helical scanning does. The option "3 mm x 7 rows" refers to specific imaging parameters rather than a scanning mode and does not by itself address the comprehensive imaging of the Circle of Willis.