ASSESSMENT OF A TECHNOLOGY THAT PERMITS INDIVIDUALIZED SCAN DELAYS ONHELICAL HEPATIC CT - A TECHNIQUE TO IMPROVE EFFICIENCY IN USE OF CONTRAST MATERIAL

OBJECTIVE. We performed this study to assess the usefulness of a compu ter automated scan technology (CAST) for individualizing scan delay du ring helical CT to improve the efficiency of hepatic enhancement. SUBJ ECTS AND METHODS. We prospectively evaluated 183 patients who were ran domized into five groups. Control patients received 100 or 150 ml of c ontrast material (320 mg I/ml) with a 60-sec delay between contrast in jection at 3 ml/sec and scanning. CAST patients received 100, 125, or 150 mi. In our latter groups we used an hepatic enhancement threshold of 50 H over baseline to determine the optimum delay between contrast injection and scanning. For the intergroup comparisons, we measured th e liver on baseline and enhanced helical CT scans at the upper, mid, a nd lower levels of the liver. RESULTS. The mean enhancement in patient s who received 150 mi of contrast material was 70.7 +/- 19.4 H for the control group and 81.0 +/- 17.5 H for the CAST group (p < .05). Hepat ic enhancement above 50 H was achieved in 84% of the control subjects compared with 100% of CAST subjects; more than 60 H hepatic enhancemen t was achieved in 73% of control subjects and in 89% of CAST subjects. The use of CAST software with 125-ml contrast doses provided enhancem ent equivalent to that of control subjects who received 150 mi of cont rast material (mean enhancement in CAST subjects, 70.3 +/- 15.4 H). En hancement above 50 H was reached in 98% of CAST and 84% of control pat ients, With 100 ml of contrast material, 24% of patients failed to ini tiate CAST, resulting in enhancement similar to control patients (CAST , 54.2 +/- 11.4 H; controls, 56.9 +/- 15.2 H). CONCLUSION. Using a con trast dose of 150 mi, CAST provided significantly increased hepatic en hancement than that achieved in control subjects with less variability , For equivalent hepatic enhancement, contrast doses could be decrease d by 25 mi using CAST technology because it provides individualized sc an delays.