VARIABLE-MODE HELICAL CT - IMAGING PROTOCOLS

Helical CT provides a rapidly acquired, accurately registered, two-dim ensional data set during the phase of maximum vascular and parenchymal enhancement, The z-axis can be covered by using either a single acqui sition, single breath-hold technique or by using multiple helical grou ps with intergroup delays for the patient's breathing. The fatter appr oach, called variable-mode helical CT, allows large z-axis coverage of more than one anatomic region during injection of a single bolus of c ontrast material. We discuss helical scanning protocols, both single-a cquisition and variable-mode, that we have developed for detection of disease involving major blood vessels (pulmonary arteries and aorta), perivascular tissue planes (neck, thorax, and pelvis), and abdominal v iscera (liver, pancreas, and kidneys).