Optimal injection method for long-range computed tomography angiography.

We aimed to obtain high-stable computed tomography (CT) values for CT angiography (CTA). We verified the optimal use of the new protocol for long-range scanning using a contrast material flow phantom (Ichikawa, CT imaging theory. Igaku syoin Publishing, Tokyo, 8; Awai et al., Am J Roentgenol 186(2):379-385, 1) to obtain high-stable CT values (Fig. 2). We have developed a novel contrast injection method called the stable line imaging protocol (SLIP). This method involved a gradual reduction in the rate of administration of the contrast medium, which was accompanied by simultaneous administration of saline to compensate for the resultant decrease in the rate of administration. A saline flush was further added after the contrast medium injection. The rate of administration of the saline flush was the same as that of the initial contrast medium. We injected a contrast medium from the injector into the flow phantom. The time-enhancement curve (TEC) data were obtained five times by changing the injection method, and the average CT values were determined. The maximum simulation of the aortic peak enhancement of TEC was defined as pTEC. The time required to keep the CT value more than 80% of the pTEC was defined as the time period of contrast enhancement (p80). The pTEC of a single injection was 295.7 ± 5.3 HU, while that of SLIP was 296.5 ± 2.3 HU; the two values did not differ significantly. The p80 of a single injection was 19.1 ± 0.2 s, while that of SLIP was 23.2 ± 0.4 s; p80 of SLIP was 18% longer than that of the single injection.