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).