ABSTRACT
Objective To improve the degree of substitution of the cholesteryl by purifying cholesteryl succinyl ester (CHS) ,one of the raw materials .Methods CHS was purified by recrystallization ,the pure CHS structure was characterizate by differential scanning calorimetry (DSC) and X ray diffraction (XRD) ,the free cholesterol content of the pure and crude were determinated by high performance liquid chromatography (HPLC) ,the degree of substitution of the cholesteryl was determina-ted before and after the purified by 1 H-NMR .Result CHS was purer after recrystallization ,with property of crystal ,which could significantly improve the degree of substitution of the cholesteryl .Conclusion The method of purification was simple and feasible ,which was the basis of improving hydrophobically modified Bletilla striata polysaccharide′s degree of substitution of the cholesteryl .
ABSTRACT
Objective:To evaluate the effects of magnetic attachment keepers on MRI images.Me-thods:In in vitro part,keepers of MAGFIT EX 400,MAGFIT EX 600 and MAGNEDISC 800 magnetic attachment systems were cast into standard root-caps with different alloy respectively,including nickel-chromium alloy and gold-palladium alloy,or not be cast for contrast.In in vivo part,volunteers with keepers in different position and amount were included.All the specimens and volunteers were imaged by a Siemens SONATA 1.5-T MRI scanner.Extent of the artifacts in every slice was measured.The magnitude of the artifacts and the distortion of the anatomic structures were compared.Results:All kinds of keepers being studied produced obvious MRI artifacts.The extent of MRI artifacts induced by MAGFIT EX 400 keepers,MAGFIT EX 600 keepers and MAGNEDISC 800 keepers are 158.94 mm,168.52 mm and 173.00 mm,respectively.The images of mental region,tongue,palate,jawbone and sinus were evidently obscured by artifacts in all cases.When keeper was put in the molar region,the keeper-related MRI artifact may obscure the imaging of brain,spinal cord.SE sequence with right-left frequency-encoding direction was more desirable in MRI for the patients with magnetic attachment keepers.Conclusion:Keepers of magnetic attachment system did induce obvious artifacts in MRI examination.