OPTIMIZATION OF CONTRAST TIMING FOR BREATH-HOLD 3-DIMENSIONAL MR-ANGIOGRAPHY

The purpose of this study was to determine the influence of various fa ctors (age, weight, breathing, saline flush) on the contrast kinetics of a test bolus injection for the purpose of calculating the scan dela y for optimized contrast-enhanced three-dimensional MR angiography. In itially, the test bolus administration was optimized by evaluating the influence of breathing [breathing versus breath-hold) and the adminis tration of a saline hush after the contrast injection (no hush versus flush) on the kinetics of a 4-ml Gd-DTPA test bolus injection in three healthy volunteers, Subsequently, in 33 patients referred for three-d imensional MR angiography of the renal arteries, test bolus kinetics w ere correlated to age, weight, and heart rate. Zn addition, the image quality of the three-dimensional MR angiograms was assessed on a four- point scale with regard to vessel visibility. The administration of a saline Rush after the contrast injection significantly shortened the f irst appearance time (14 versus 16 seconds, P <.05), as well as the ti me to maximal signal intensity (SI) (6 versus 10 seconds, P <.05) and increased both maximum (67 versus 151 seconds, P <.05] and the SI slop e (6.4 versus 20.5 seconds, P <.05), Breath-holding was shown to have no significant affect on the test bolus kinetics, No correlation was f ound between physiologic parameters and test bolus kinetics in the pat ient group. Image quality was graded as sufficient for diagnostic purp oses in 32 of 33 patients. The contrast travel time from injection sit e to the vascular system under consideration cannot be predicted based on physiologic parameters, This time interval can be reliably and acc urately determined by a test bolus injection of a small volume of cont rast agent followed by a saline flush during normal breathing.