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In the diagnosis and treatment of medical development, MRI (Magnetic Resonance Imaging, MRI) technology has a pivotal position. It does this by bombardment spin atom under the constant external magnetic field, with a certain amount of RF field, so that excitation and then return to the ground state, generated during relaxation phenomena, and collected for the magnetic resonance signals. In order to enhance the signal contrast of normal tissue and diseased tissue, and to improve the sharpness of the image and the disease detection rate, more and more clinical MRI contrast agents (MRI contrast agent) to assist magnetic resonance imaging in the diagnosis. With the rapid rise of its research and development, with a more targeted, solubility, security and stability of these features to become the future trend of development of the contrast agent. Each polysaccharide polymer dextran 40 (by Dextran 40) and sodium alginate (Sodium Alginate) as the carrier, the purpose of synthesis with a high MRI signal intensity of the lymphatic system targeting the polymer contrast agent. Dextran as a carrier of chemical synthesis experiments using two methods Synthesis of contrast agent Dextran-DTPA-Gd, wherein the method one of dextran and DTPA dianhydride as raw materials, DMAP as a catalyst, the second method is a dextran as the raw material and DTPA , using DMAP and EDC · HCl for the combined catalyst, by comparative product of water-soluble and the content of Gd determined optimum preparation conditions, including Dextran-DTPA in the ratio of 1:1.5, the reaction time and temperature were 50 ℃ and 48 h, finally got the gadolinium content of 16.1% and good water-soluble polymer contrast agent; FTIR, particle size analysis to characterize the size of the structure and molecular size of Dextran-DTPA-Gd (distribution range of 100 to 150 nm, the average for the 130 nm), and applied to the body's lymphatic system targeting experiments. Using the two methods in the chemical synthesis experiments alginate as carrier synthesis of contrast agent Algin-DTPA-Gd alginic acid, sodium alginate as a first acidification, the catalysis of DMAP with DTPA dianhydride condensation, methods two will alginate converted to alginic acid ester, condensation in the catalysis of DMT-MM DTPA; the product obtained by the pH of the solution was adjusted, the second method Algin-DTPA-Gd with the gadolinium content (15.6%), good water-soluble, pH is low (pH lt; 3) characteristics; by FTIR, particle size analysis to characterize the structure of its molecules Algin-DTPA-Gd particle size (distribution range of 38 to 135 nm, an average of 108 nm ). Lymphatic system in vivo targeting experiments Healthy adult female New Zealand rabbits first 3D Fast TOF-SPGR CE-MRA sequence level sweep, respectively puncture rabbit right foot and left foot intradermal injection of synthetic polymer contrast agent Dextran-DTPA-Gd (0.4 mL, 3.96 mmol / L) as well as the positive control reagent injection of gadolinium-DTPA (Magnevist, 0.4 mL, 0.50 mol / L), between the two injection time interval of about 30 min. Rabbit 2, its left foot and right foot simultaneous injection of Dextran-DTPA-Gd (0.4 mL, 3.96 mmol / L), after the completion of the two experimental injection of contrast agent in 10,20,25,30,35,40 45,50,55 min, 1,4 and 24 h the 3D enhanced scan. Rabbit Dextran-DTPA-Gd and gadopentetate dimeglumine injection (Magnevist) experimental results compared leg magnetic resonance imaging results the popliteal lymph system signal strength measurements at different times and calculate its rate of signal enhancement (E %), draw signal enhancement rate of the lymphatic system - time curve; simultaneous contrast the rabbit rabbit leg magnetic resonance imaging Figure. The final experimental results demonstrate Dextran-DTPA-Gd has obvious lymphatic system selectivity than the injection of gadopentetate dimeglumine (maximum value of 98.3%) having a higher rate of signal enhancement (maximum value of 314.1%), in its further The application laid a foundation.
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