[Assessment of contrast enhancement using the variable contrast medium injection method in 3D-CTA of the head]

We have reported that, using the bolus-tracking method synchronized with an injector, the injection of contrast medium in a single phase up to 10 sec before the end of the study (referred to as "single-stage injection") or the combination of single-stage injection stopped 15 sec before the end of the study and a physiological saline solution flush (referred to as "saline solution flush") makes it possible to minimize the amount of contrast medium employed in 3D-CTA of the head and neck in a scanning time of approximately 30 sec. If the continuous variable method of contrast medium injection (referred to as "variable injection") can provide the same level of contrast enhancement as that obtained with a single-stage injector for constant-rate injection, it should be possible to eliminate cumbersome study procedures associated with the saline solution flush and to simplify the study protocol. We therefore performed a comparative study to assess the contrast enhancement effect in variable injection. The results showed that variable injection provided almost the same degree of contrast enhancement as single-stage injection + saline solution flush, while permitting the amount of contrast medium to be reduced. It was concluded that variable injection (with a variation parameter of 0.5) is an effective method of improving the contrast enhancement effect and minimizing the amount of contrast medium employed, as compared with the saline solution flush method. Furthermore, it permits the examination procedures to be simplified.