Qualitative And Quantitative Study Of Articular Cartilage Changes Based On Magnetic Resonance Multimodal Images

Part ?:Feasibility of Dual Flip Angle-Based Fast 3-Dimensional T1 Mapping for Delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage of the Knee:A Histologically Controlled StudyObjective:The aim of the study was to validate dual-flip angle-based fast 3-dimensional(3D)T1 mapping for delayed gadolinium-enhanced magnetic resonance imaging(MRI)of cartilage(dGEMRIC)by means of histological analyses in the assessment of the cartilage of the knee in a porcine model.Methods:A total of 15 mini pigs were included in this study.The left knee anterior cruciate ligaments of all mini pigs were transected.The mini pigs were divided into 3 groups postoperatively,with 5 pigs randomly assigned to 1 group.Dual-flip angle-based fast T1 mapping for dGEMRIC was obtained in the sagittal planes at 0 week(group 1),3 weeks(group 2),and 6 weeks(group 3)after operation,using an 8-channel knee coil.Magnetic resonance imaging was performed at 3T with dual-flip angle-based fast 3D T1 mapping sequence for morphological cartilage assessment of dGEMRIC T1 values.After MRI analysis,histological and biochemical composition(water,collagen,and glycosaminoglycan[GAG])of the knee cartilage in the medial femoral condyle was quantified ex vivo.Results:The T1 values obtained by the dual-flip angle-based fast 3D T1 mapping were positively correlated with the glycosaminoglycan content(r = 0.85;P<0.05).The values had no significant correlation with the collagen content.The dGEMRIC-T1 values obtained by this method showed the medial femoral condyle cartilage in the anterior cruciate ligamenttransected knee after transection decreased with time(P<0.05).Histological sections of cartilage damage were correlated with MRI data.Conclusions:This study demonstrated the reliability of using dual-flip angle-based fast T1 mapping for dGEMRIC for the biochemical assessment of early cartilage degeneration.This technique is a powerful tool for researchers and clinicians to acquire sufficient resolution data within a reasonable scan time.Part ?:Use of Quantitative MRI for the Detection of Progressive Cartilage Degeneration in a Mini-pig Model of Osteoarthritis Caused by Anterior Cruciate Ligament TransectionObjective:To investigate the progression of cartilage degeneration using delayed gadolinium-enhanced MRI of carti-lage(dGEMRIC)and T2 mapping in a mini-pig model of osteoarthritis(OA)caused by anterior cruciate ligament trans-ection(ACLT).Methods:Twelve mini-pigs underwent ACLT in the left knee and were monitored by dGEMRIC(T1,gadolinium[Gd])and T2 mapping after 2,4,or 6 weeks(n=4 each).No ACLT surgery was performed in four healthy control mini-pigs,which were also monitored by dGEMRIC and T2 mapping.Cartilage samples from the weight-bearing regions of the left medial femoral condyles werecollected for macroscopic,histological,immunohistochemical,and biochemical analy-sis.Correlations between biochemical contents and T1Gd and T2 values were evaluated using Pearson correlation analysis.Results:T1Gd values were gradually reduced and T2 values increased over time.Cartilage surfaces showed roughness at 4 weeks and additional defects at 6 weeks.Glycosaminoglycan(GAG)distribution and content gradually reduced over time(P<0.05),and collagen distribution and anisotropy were obviously changed at 6 weeks.However,collagen content did not differ significantly among postoperative timepoints.GAG content was positively related to T1Gd values(r=0.888;P<0.001)and negatively related to T2 values(r=0.865;P<0.001).Collagen content had no discernible correlation with TIGd or T2 values.Conclusion:dGEMRIC and T2 mapping can monitor the progression of cartilage degeneration in a mini-pig model of ACLT-induced OA,permitting early detection of OA.Part ?Reproducibility of dual-flip angle 3D T1 mapping for delayed gadolinium enhanced MRI of cartilage(dGEMRIC)of the knee at 3.0 T in healthy animal modelObjectives:To assess the reproducibility of dual-flip angle 3D T1 mapping for delayed gadolinium-enhanced MRI of cartilage(dGEMRIC)at 3 T in healthy procine models.Methods:In 20 procine models,dual-flip angle 3D T1 mapping for 3D dGEMRIC at 3 T was acquired twice within 7 days.To correct for procine motion during acquisition,all images were rigidly registered in 3D.Eight anatomical cartilage ROIs were analysed on both images of in the left procine knee.Capability of dGEMRIC to yield T1 maps that reproducibly distinguish spatial differences in cartilage quality was assessed in two ROIs within a single slice in each patient.Reproducibility was assessed using ICCs and Bland-Altman plots.Results:ICCs ranged from 0.86 to 0.93,indicating good reproducibility.Based on the Bland-Altman plots,we defined a threshold of 115 ms to determine if a change in dGEMRIC outcome in longitudinal research was statistically significant.Conclusions:3D knee dGEMRIC at 3 T combined with 3D image registration is a highly reproducible measure of cartilage quality in early stage OA.Therefore,dGEMRIC may be a valuable tool in the non-invasive evaluation of cartilage quality changes in longitudinal research in patients with early stage OA and focal cartilage defects.