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Objective To investigate the ability of T2 mapping in early detection of the change of cartilage collagen by quantitative analysis.Methods 20 porcine patellae were randomly assigned into 4 groups,3 treated groups and 1 control group.The samples of 3 treated groups were respectively immersed in PBS with 100 mg/100 mL,1 50 mg/100 mL and 200 mg/100 mL typeⅡ collagenase for 4 h,whereas control group samples in PBS for 4 h.T2 relaxation times of superficial,deep and full layers of cartilage and mean densi-ty after Van Gieson stain were measured.The correlation of T2 relaxation times and mean density were statistically analyzed.Results Gross pathology showed all articular cartilages maintained intact after treatment.T2 relaxation times of superficial and full layers and mean density increased significantly in any treated group in comparison with control group(P 0.05).Pearson correlation analysis showed a close correlation(r=-0.837)between T2 relaxation times of full layers and mean density.Conclusion T2 map-ping can adequately detect the change of cartilage collagen in the early stage of osteoarthritis,and shows a good clinical application prospect.
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Objective To assess the advantages of multi-source RF transmission(MT) for balanced fast field echo(BFFE) cardiac cine imaging.Methods Fifteen volunteers were scanned on a clinical 3.0 T MR system equipped with MT.Acquisition of B1 maps with and without MT were followed by axial and four chambers BFFE cine imaging for all subjects with different transmission modes[single source RF transmission (ST),MT and MT with allowable shortest TR(MTS)].The B1 field uniformity and contrast to noise ratio (CNR) were quantitatively analyzed.The B1 field uniformity was evaluated by the pixel values within the ROI and was compared with Student t test.CNR was defined as follows:(SIblood-SImyocardium)/ 0.5 ×(SDblood + SDmyocardium).CNR were tested with one-way ANOVA for three groups comparision and with LSD for inter-group comparison.Image qualities were blindly assessed by 2 readers with a 4-score scale.Global image quality scores were tested for statistical significance by using the nonparametric paired sample Friedman rank test for three groups and the Wilcoxon signed rank test for further inter-group comparison.The Kappa statistics was used to assess interreader agreement.Results B1 homogeneity was significantly improved for images with MT compared with ST under the condition of other parameters unchanged (t =21.632,P ＜0.01).In left ventricular,CNR of blood and myocardium was improved from 10.8 ±2.2 for ST to 14.4 ± 2.4 for MT and 14.1 ± 2.2 for MTS.In fight ventricular,it was improved from 7.7 ± 1.2 for ST to 12.2 ± 1.4 for MT and 12.0 ± 1.2 for MTS.The differences were statistically significant (F =11.617,61.472,P ＜0.01).The images of MT and MTS groups demonstrated greater CNR versus the ST images.There was no statistical difference between latter two groups.The image scores of Reader 1 and 2 were 4.60 ± 1.18 and 4.73 ± 1.10 for ST,6.53 ± 1.19 and 6.67 ± 1.29 for MT and 6.73 ± 1.03 and 6.73 ± 0.88 for MTS respectively.There were statistically differences among three groups (x2 =23.577,24.275,P ＜ 0.01).The image quality was improved on BFFE images using MT and MTS technology compared to ST technology,and there were also significant differences.The interreader agreement between two readers was good [K=0.643,0.722 and 0.814(P ＜0.05) for ST,MT,and MTS group respectively].Conclusions MT technology significantly improves B1 field uniformity,increases CNR and reduces artifact on BFFE cardiac cine images.The TR is decreased within the normal SAR ranges,and thus scanning speed is increased.
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Objective To investigate the role of dual-source parallel radio frequence (RF) and single-source excitation in liver imaging at 3.0 T MR.Methods This study was a retrospective analysis.One hundred and seven subjects underwent a 3.0 T TX MR scanning including axial spectrally selective attenuated inversion recovery (SPAIR) T2WI,axial DWI and coronal balanced-fast field echo( Balanced FFE).Each sequence was carried out with both single-source and dual-source RF excitation.Student＇s t test was used to compare the differences between single-source and dual-source RF excitation in the image uniformity,signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR).Wilcoxon signed rank test was used to determine whether there was difference between conventional and parallel transmission in the score of image quality.Reader agreement was assessed using the Cohen＇s Kappa test.Results For the image uniformity,there was significant difference between single-source and dual-source excitation (418.40 ± 66.75 for single-source vs.416.26 ± 50.61 for dual-source,t =2.524,P ＜ 0.05 ).There also existed significant difference between single-source and dual-source excitation in SNR and CNR,respectively.The SNR and CNR of parallel transmission (22.03 + 12.16 and 18.33 ± 10.01,respectively) were both higher than those of single transmission (20.36 ± 11.21 and 15.22 ± 8.95,respectively) ( t =- 2.630,P ＜ 0.05 for SNR and t =- 4.238,P ＜ 0.05 for CNR).Image quality comparisons revealed significantly better results with dual-source than single-source RF excitation at SPAIR T2 WI ( 1.40 + 0.42 vs.1.81 ± 0.27 ),DWI ( 1.08 ± 0.40 vs.1.63 ± 0.36 ) and Balanced FFE sequence ( 0.95 ± 0.45 vs.1.65 ± 0.37,Z =- 5.894,- 5.801 and - 6.985,respectively,P ＜ 0.01 ).In the comparison of image quality,the agreement between the two readers was very good ( Kappa ＞ 0.8,P ＜ 0.05 ).Conclusion Dual-source parallel RF excitation MR imaging in liver enables reducing dielectric shading,improving homogeneity of the RF magnetic induction field,and increasing SNR and CNR at 3.0 T.