In the 1990s, a new form of CAT (computed axial tomography) scan was developed called a spiral CAT scan (also called a helical CAT scan or volumetric CT). This new method uses special slip-ring technology to create a continuously moving x-ray tube, which eliminates the bulky, time-consuming cables of earlier CAT scan machines. Although some facilities still use earlier generation CAT scan machines, spiral CAT scans are expected to replace them soon.

Spiral CAT scans have several advantages over traditional CAT scans. For example, because the machine rotates in a continual spiral path it can be used to create three-dimensional images of body areas. The test can also be performed in less time than traditional CAT scans. This reduces distortion caused by movement as a patient breathes, which is inevitable during longer scans. A helical CAT scan can often be performed while the patient holds a single breath, which limits patient movement and delivers a sharper picture.

The helical CAT scan also produces results much faster. Results may even be available before the patient leaves the testing site. In addition, the test’s high level of sensitivity makes it a particularly useful tool in diagnosing small, cancerous tumors.

A new technique known as virtual endoscopy uses a small lighted tube (endoscope) during a spiral CAT scan to allow physicians to see inside organs or other body structures without surgery or special instruments. A virtual colonoscopy (also known as a CAT colonography) produces images of the colon and can be used to diagnose colon and bowel disease. It can be performed with a CAT scan or magnetic resonance imaging (MRI).