Gadolinium-DTPA-dextran: a macromolecular MR blood pool contrast agent.

RATIONALE AND OBJECTIVES

Magnetic resonance (MR) imaging blood pool agents offer numerous advantages for vascular and tumor imaging. The purpose of this study was to test gadolinium-diethylenetriaminepentaacetate-dextran ([Gd]DTPA-dextran) as a new water soluble macromolecular blood pool agent for MR imaging.

MATERIALS AND METHODS

[Gd]DTPA-dextran (187 gadolinium atoms per dextran, molecular weight 165 kD, diameter 17.6 nm) was synthesized. Fifteen anesthetized New Zealand White rabbits with thigh VX2 tumors were scanned in a knee coil at 1.5T. Coronal 3D MR angiographic sequences were obtained before and at several time points up to 72 hours after the intravenous bolus injection of [Gd]DTPA-dextran providing gadolinium at either 0.05 (n = 4) or 0.1 mmol/kg (n = 8) or [Gd]DTPA-bismethylamide (BMA) providing gadolinium at 0.1 mmol/kg (n = 3). Time enhancement curves for aorta, cava, and tumor rim were compared by univariate General Linear Model.

RESULTS

Contrast enhancement of cava and aorta relative to a water phantom were significantly greater at all time points after either dose of [Gd]DTPA-dextran than after [Gd]DTPA-BMA (P < 0.01). Tumor rim enhancement was less intense for either dose of [Gd]DTPA-dextran at peak than for [Gd]DTPA-BMA (P < 0.05). Tumor rim enhancement with both doses of [Gd]DTPA-dextran became equivalent to that of [Gd]DTPA-BMA at one hour and was greater at 24 hours (P < 0.05).

CONCLUSION

[Gd]DTPA-dextran is a new macromolecular MR contrast agent that can be synthesized to carry a high density of gadolinium atoms without intra-molecular cross-linking. It provides significantly greater vascular residence time than a conventional gadolinium chelate and shows promise for MR blood pool imaging.