Use the drop-down menu to select the answer that completes each sentence. Imaging techniques have different uses; for example, the magnets used by show different tissues and structures than X-ray imaging. is used to create a three-dimensional image of internal structures, such as tumors in the gut. Although CAT scans use X-rays, uses sound to create an image. Although both measure electrical activity in a similar way, measures the activity of the heart, while measures the activity of the brain.