Uniform vascular contrast enhancement and reduced contrast medium volume achieved by using exponentially decelerated...

To investigate in computed tomographic (CT) angiography whether an exponentially decelerated contrast medium injection, as compared with a standard constant-rate injection, can facilitate uniform vascular contrast enhancement with a reduced contrast material volume.

CT angiography of the abdominal aorta was performed in 46 subjects by using an exponentially decelerated injection method: 134 mL of contrast medium was injected for 40 seconds, starting at 4.0 mL/sec and decreasing exponentially to 2.7 mL/sec by the end of the injection. Twenty-one of these subjects also underwent CT angiography with a constant-rate injection: 160 mL of contrast medium was injected for 40 seconds at a constant rate of 4 mL/sec. Time-enhancement curves and the magnitude of peak vascular enhancement were measured. Enhancement uniformity was evaluated by using three indexes: (a) duration of contrast enhancement achieved within 80% of the peak (80% DCE), (b) SD of the normalized contrast enhancement (SDNCE) measured from the beginning of spiral CT scanning to the time when the enhancement decreased to a level lower than the beginning level, and (c) slope of the enhancement curve calculated by using linear regression analysis.

Exponentially decelerated injection resulted in more uniform enhancement. Mean values generated by using exponentially decelerated versus constant-rate injection in 21 paired comparisons were, respectively, 30.8 seconds +/- 5.0 versus 22.6 seconds +/- 7.6 for 80% DCE, 0.052 +/- 0.017 versus 0.086 +/- 0.031 for SDNCE, and 0.47 HU/sec +/- 0.70 versus 2.27 HU/sec +/- 0.87 for slope (P <.001 for all indexes). Compared with the peak enhancement resulting from the constant-rate injection, that resulting from the exponentially decelerated injection was reduced by a mean of 17.2% +/- 10.0.

Uniform vascular contrast enhancement and reduced contrast medium volume, which are desirable in CT angiography, can be achieved with exponentially decelerated injection.