Helical CAT scan: Helical computed axial tomography scan (CAT scan or CT scan) is another name for a CT scan, and is also called a spiral CT scan. Until approximately the mid to late 1990's, CT images were obtained one slice at a time, with the patient table moving step by step through the gantry. Scans obtained using this older technique often required 30 or 45 minutes, and the patient held his or her breath for every slice. Helical or spiral CT scans are obtained usually with one breath hold and obtain a volume of X-rayed tissue while the table moves rapidly through the gantry. Complete exams can be performed in less than five minutes. With the advent of helical or spiral CT scanning and rapid image acquisition, CT scanning has become the main diagnostic imaging tool in the radiology department.