Effect of contrast dilution on contrast-enhanced MR angiography of the aorta and renal arteries.

The aim of this study was to investigate the effect of gadolinium chelate dilution on vascular enhancement in contrast-enhanced two-dimensional (2D) MR subtraction angiography of aorta and renal arteries. Twenty patients were prospectively included. 2D subtraction MR angiography consisted of successive multisection breathhold GRE acquisitions of 16 s (2D FLASH, TR/TE 72/4, flip angle 60 degrees) obtained in the coronal plane before and after intravenous bolus administration of 0.1 mmol/kg BW gadolinium chelate. Patients underwent both diluted and undiluted gadolinium chelate administration in a random order. The data were studied both qualitatively and quantitatively on source and maximum intensity projection images. The length of renal arteries opacified was found not to differ significantly according to contrast dilution. The contrast enhancement percentage was not significantly modified according to the dilution used, but the time to peak enhancement was observed to be longer with the diluted contrast. Qualitatively, the best MR images were those obtained when undiluted contrast was injected first (chi2, P = 0.01). At a dosage of gadolinium chelate 0.1 mmol/kg BW, undiluted contrast 2D MR subtraction angiography seems to be more appropriate for studying diseases of the aorta and renal arteries than a similar diluted dose.