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. Tumor rim enhancement with both doses of DTPA-dextran became equivalent to that of DTPA-BMA at one hour and was greater at 24 hours (P < 0.05). Tumor rim enhancement was less intense for either dose of DTPA-dextran at peak than for DTPA-BMA (P < 0.05). Contrast enhancement of cava and aorta relative to a water phantom were significantly greater at all time points after either dose of DTPA-dextran than after DTPA-BMA (P < 0.01). Time enhancement curves for aorta, cava, and tumor rim were compared by univariate General Linear Model. Coronal 3D MR angiographic sequences were obtained before and at several time points up to 72 hours after the intravenous bolus injection of DTPA-dextran providing gadolinium at either 0.05 (n = 4) or 0.1 mmol/kg (n = 8) or DTPA-bismethylamide (BMA) providing gadolinium at 0.1 mmol/kg (n = 3). Fifteen anesthetized New Zealand White rabbits with thigh VX2 tumors were scanned in a knee coil at 1.5T. DTPA-dextran (187 gadolinium atoms per dextran, molecular weight 165 kD, diameter 17.6 nm) was synthesized. The purpose of this study was to test gadolinium-diethylenetriaminepentaacetate-dextran (DTPA-dextran) as a new water soluble macromolecular blood pool agent for MR imaging. It provides significantly greater vascular residence time than a conventional gadolinium chelate and shows promise for MR blood pool imaging.Ībstract = "Magnetic resonance (MR) imaging blood pool agents offer numerous advantages for vascular and tumor imaging. U.S.A., 96, 15256 (1999).Magnetic resonance (MR) imaging blood pool agents offer numerous advantages for vascular and tumor imaging. From these findings, it is possible that heparin-coated SPIO can be used as a good negative contrast agent in clinical MRI. From the results of in vitro cellular labeling, heparin-coated SPIO was more advantageous for cellular labeling because it could powerfully visualize the cells after a short incubation time (2 h). Both SPIO nanoparticles can be still suitable for T 2-weighted MRI because r 2 /r 1 ratio was >10. The reason was that the heparin-coated had a lower r 2/ r 1 ratio (18.2) at 1.5-T magnetic resonance imaging (MRI) compared to dextran-coated SPIO ( r 2/ r 1 ratio 32.9). In addition, the heparin-coated SPIO showed higher hyponegativity than dextran-coated SPIO. The zeta potential of heparin-coated SPIO was caused by the rich sulfonate group of heparin. The Zeta potential of non-coated SPIO was approximatelt −44 mV, whereas dextran-coated or heparin-coated SPIO was −6.4 and −33.5 mV, respectively. The zeta potential of the SPIO surface was detected to confirm the polymer coating. Compared to the uncoated SPIO, the heparin or dextran coating provided a better dispersion of SPIO nanoparticles in solution. The size of the crystalline core was adjusted to provide suitable relaxometric properties. Dextran-coated SPIO, which is commercially available as Feridex®, was prepared for the control group. In this study a potential magnetic resonance (MR) T 2 contrast agent was developed systematically based on heparin-coated superparamagnetic iron oxide (SPIO) nanoparticles.
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