MR-Angiographie: Prospektive, randomisierte Studie zum Einfluß verschiedener Kontrastmittelmengen auf das vaskuläre Signalverhalten nach i. v. Bolusinjektion

Abstract In this study we wanted to show the effects of different concentrations of contrast agent on signaltime curves and image contrast of the abdominal aorta, vena cava, portal vein, liver, spleen and kidneys in comparison to each other. 60 patients (32 women, 28 men, mean age 56 / 14 years) were included and divided into three dosage groups (0,1 mmol/kg bodyweight, 0,2 mmol/kg bw, 0,3 mmol/kg bw). The patients were randomized by a randomization list created prior of the start of the study. Neither the patient nor the evaluating researchers were informed about the administered dose. Imaging was carried out in a 1.0 Tesla clinical scanner. All patients were scanned using a time-resolved 3 D Flash sequence acquiring 58 phases with a 3,75 second acquisition time per phase. The application of the contrast agent was carried out using a power injector. Imaging started at the same time as the application of the contrast agent. Signal intensity time curves were generated with a region of interest placed in the structures of interest. Further variables were derived from the evaluated signal intensity time curves. Beside the peak signal intensity (peak SI – maximum SI during entire examination), arrival time (time from start of injection to time when SI increased at least 200% of the baseline SI), peak SI time (time to reach peak), wash-out-time (time when SI dropped to 50% of the maximum SI) and relative SI after ten minutes were determined. Statistical analyses were performed by using the freeware software R (http://www.R-project.org). The mean differences between the three contrast agent groups for weight, age, SI and image contrast parameters were investigated. Analyzed SI parameters were arrival time, relative peak SI, time to peak SI, wash out time and relative SI after ten minutes. Image contrast was calculated between the aorta and all other vessels and organs. The statistically significant mean differences between the three contrast agents groups were identified by a one-way ANOVA and corresponding p-values were corrected using Bonferroni correction. Comparing the three contrast agent groups referring to the main criterion wash out time one can find a significant difference between the portal vein and the abdominal aorta with increasing contrast agent dose leading to a longer wash out time. This should not be significant in the practical use, because wash out time with a single does is sufficient for a good contrast in first pass imaging. The largest peak SI with triple dose of contrast agent could only be determined in the abdominal aorta. The other vessels showed no significant difference of peak SI with increasing contrast agent dose. Considering the organs, the only significant difference in peak SI could be found for the kidneys using double dose instead of single dose. All other organs did not show significant results. However, we must notice that the absolute distance of the significant results is very small, so the benefit is uncertain. For some organs (spleen, kidneys, liver) we could even find a decrease of peak SI with higher dosage. Our findings suggest that a single dose seems to be sufficient for high quality in abdominal MRA.