Study on isotropic elasticity reconstruction algorithms for magnetic resonance elastography / 医疗卫生装备

Objective To analyze the advantages and disadvantages of various harmonic magnetic resonance elasticity reconstruction algorithms.Methods Different reconstruction algorithms were categorized according to their mathematical hypotheses.The influence of different assumptions on elasticity reconstruction was investigated with experiments and from mathematical fundamentals.Results The finite element full inversion method had higher precision while more computational time.The algorithms with local homogeneity and incompressibility assumptions were faster while less accurate.The algorithms considering the local change of elastic moduli could effectively reduce boundary artifacts.Conclnsion Different assumptions of algorithms may cause levels of errors between the estimated and real elastic moduli.The selection of elasticity reconstruction algorithms in practical experiment requires a comprehensive tradeoff.

Construction and identification of pIRES2-GDNF-VEGF165 bicistronic eukaryotic expression vector / 中国组织工程研究

BACKGROUND:Human glial cellline-derived neurotrophic factor (GDNF) and vascular endothelial growth factor 165 (VEGF 165 ) are essential genes for celldifferentiation. OBJECTIVE:To construct and identify pIRES 2-GDNF-VEGF 165 bicistronic eukaryotic expression vector. METHODS:Human GDNF genes were obtained from the genomic DNA of human peripheral blood mononuclear cells by PCR. Then the GDNF cDNA fragment was inserted into the multiple cloning sites of pIRES 2-EGFP, to generate the bicistronic eukaryotic expression plasmid pIRES 2-GDNF-EGFP. The VEGF 165 gene was obtained from pIRES 2-VEGF 165-EGFP plasmid by twin PCR. Then VEGF 165 cDNA fragment was cloned into the pIRES 2-GDNF-EGFP, instead of EGFP, to create a double gene co-expressing vector plasmid pIRES 2-GDNF-VEGF 165 containing internal ribosome entry sites. Then pIRES 2-GDNF-VEGF 165 was used to transfect HEK293 cells. RT-PCR and western blot analysis were performed to test the co-expression of double genes. RESULTS AND CONCLUSION:DNA sequencing analysis demonstrated that the GDNF and VEGF 165 were exactly consistent with the sequence recorded in the GenBank. The size of GDNF gene was 636 bp and the size of VEGF165 gene was 576 bp. Enzyme digestion analysis indicated that, pIRES2-GDNF-VEGF165 bicistronic eukaryotic expression vector inserted GDNF band by Bgl II/Bam HI, inserted IRES-VEGF 165 fragment by Bam HI/Not I, and inserted GDNF-IRES-VEGF165 fragment by Bgl II/Not I. RT-PCR and western blot analysis showed that, after HEK293 cells were transfected with pIRES 2-GDNF-VEGF 165 , double genes were expressed at the mRNA and protein levels. The pIRES 2-GDNF-VEGF 165 bicistronic eukaryotic expression vector is successful y constructed.

Construction and Identification of pIRES 2-BDNF-VEGF 165 bicistronic eukaryotic expression vector / 中国组织工程研究

BACKGROUND:Brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor 165 (VEGF 165 ) are essential genes for celldifferentiation. Virus mediated method has been used numerously in researches, but the security is the most important problem. Eukaryotic expressing vector is a way to solve this question. OBJECTIVE:To construct and identify pIRES 2-BDNF-VEGF 165 bicistronic eukaryotic expression vector. METHODS:BDNF genes were obtained from the genomic DNA of human peripheral blood mononuclear cells by PCR. Then, the BDNF cDNA fragment was inserted into the multiple cloning sites of pIRES 2-EGFP to generate the bicistronic eukaryotic expression plasmid pIRES 2-BDNF-EGFP. The VEGF 165 gene was obtained from pIRES 2-VEGF 165-EGFP plasmid by double PCR. Next step was that VEGF 165 cDNA fragment was cloned into the pIRES2BDNF-EGFP instead of EGFP to create a double gene co-expressing vector plasmid pIRES 2-BDNF-VEGF 165 . Then, pIRES 2-BDNF-VEGF 165 was used to transfect HEK293 cells, and RT-PCR and western-blot assay were employed to test the co-expression of double genes. RESULTS AND CONCLUSION:BDNF and VEGF 165 genes were cloned in this study. The DNA sequencing analysis demonstrated that the BDNF and VEGF 165 were exactly consistent with the sequence recorded in the GenBank. The size of BDNF gene was 744 bp. The VEGF 165 gene was obtained from pIRES 2-VEGF 165-EGFP plasmid by PCR, and the size of VEGF 165 gene was 576 bp. Enzyme digestion analysis indicated that BDNF and VEGF 165 genes were inserted into the expression vector pIRES 2-EGFP correctly and the BDNF and VEGF165 co-expression plasmid was successful y constructed. Then, by transfecting pIRES 2-BDNF-VEGF 165 into HEK293 cells, double genes were expressed at the mRNA and protein level. It provides a novel expression system, which enables further study on the functions of BDNF and VEGF 165 genes.

Quantifying the amplitude of microvolt T wave alternans with sparse principal component analysis / 生物医学工程学杂志

T wave alternans in ECG is an important prediction factor for a sudden death. It is crucial in clinic to quantify the amplitude of T wave alternans. However, T wave alternans are highly non-stationary, which makes accurate quantification very difficult. In this study, we proposed a new method to improve the amplitude quantification. We identified T wave alternans by principal component analysis (PCA) with statistical test, and processed the principal components with T wave alternans further by imposing sparse constraint. We evaluated and compared our method against other 4 popular solutions on an international benchmark database. The results including rank correlation coefficient and relative error indicate that this sparse principal component (SPC) based method is better than others.