DIFFERENCES IN INJECTION RATES ON CONTRAST-ENHANCED BREATH-HOLD 3-DIMENSIONAL MR-ANGIOGRAPHY

OBJECTIVE, The aim of the study was to evaluate the optimization of in jection rates with an automatic power injector versus manual injection for contrast-enhanced breath-hold three-dimensional (3D) MR angiograp hy of the abdominal aorta and its branches. SUBJECTS AND METHODS. In a prospective study, 50 patients underwent breath-hold 3D MR angiograph y (5/2 [TR/TE]; flip angle, 30 degrees) of the abdominal vessels on a 1.5-T system. Each patient received 0.15 mmol/kg of gadopentetate dime glumine. All patients were randomly assigned to one of five equally si zed groups. The contrast bolus was injected manually in group 1, alway s by the same investigator, who tried to perform a steady injection ra te of 2 ml/sec. An automatic injector was used in groups 2-5 with inje ction flow rates of 0.5 ml/sec, 2 ml/sec, 4 ml/sec, and 6 ml/sec. The start of the MR sequence was tailored individually to the applied volu me of contrast material after determination of circulation limes by a test bolus. We measured the signal-to-noise and contrast-to-noise rati os as well as the relative vascular enhancement. The visualization of different abdominal vessel segments was independently ranked on a scal e of 1-5 (1 = not visible; 5 = excellent visualization) by three revie wers who were unaware of the applied contrast material injection rate. RESULTS. The signal-to-noise and contrast-to-noise ratios of groups 3 and 4 (2 ml/sec and 4 ml/sec, respectively) were significantly (p <.0 5) higher than the ratios of groups 1, 2, and 5. The average relative vascular enhancement of groups 3 and 4 was significantly higher (p <.0 5) than the enhancement of all other groups. The contrast bolus applie d with a faster injection rate (group 5) did not cover large parts of the K-space, resulting in increased blurring of the vessel contours. T he subjective evaluation of large and small diameter vessels showed si gnificantly better results in groups 3 and 4 than in groups 1, 2, and 5. CONCLUSION, The use of an automatic MR power injector proved superi or to manual injection of contrast material. The optimal injection rat e was 2 ml/sec for 3D breath-hold MR angiography of the abdominal vess els.