The MR Quantitative Analysis Of Adipose Tissue Around Knee Joint And Its Correlation With Knee Cartilage Injury

Objective:To investigate the correlation between adipose tissue around knee joint and articular cartilage injury using the combination of IDEAL-IQ sequence and T2 Mapping sequences.Methods:A total of 112 subjects were collected from January 2019 to May 2020.And all subjects received 3.0T MR examination of the knee joint.The MR sequences included Sag-PDWI,SagT2 Mapping,Sag/Axial-FST2 WI,Sag/Axial-IDEAL-IQ.On FST2 WI images,subjects were divided into normal controls and KOA group(including mild,moderate,and severe cartilage injury subgroups)according to the WORMS scoring system for cartilage injury.The FF and T2 values of IPFP,SPFP,subchondral bone marrow and deep bone marrow of femoral trochlea were measured respectively,and T2 value of the most severe cartilage defect area was measured.Chi-square test was used to evaluate the differences between normal,mild,moderate,and severe cartilage injury groups.Univariate or multivariate analysis was used to analyze the correlation of significant indexes to determine whether the T2 and FF values of different tissue structures(IPFP,SPFP,subchondral bone marrow,and deep bone marrow)were correlated with the T2 values of cartilage.Results:1、The T2 value of cartilage in the KOA group was significantly higher than that in the normal group,and the increased T2 value of cartilage was statistically different with the severity of KOA(P<0.05).2、Compared with the normal controls,the FF value of IPFP significantly reduced from the mild to severe cartilage injuries in the KOA group,and the FF value of IPFP was negatively correlated with the T2 value of cartilage(r=0.250,P<0.05).The T2 value of IPFP significantly increased from the mild to severe cartilage injuries in the KOA group,and the T2 value of IPFP was positively correlated with the T2 value of cartilage(r=0.198,P<0.05).3、Compared with the normal group,the FF value and T2 value of SPFP significantly decreased from the mild to severe cartilage injuries in the KOA group.The FF value of SPFP was negatively correlated with the T2 value of cartilage(r=0.393,P<0.001).Also,T2 value of SPFP was negatively correlated with T2 value of cartilage(r=0.193,P<0.05).4、Compared with the normal group,the FF and T2 values of subchondral bone marrow significantly decreased from the mild to severe cartilage injuries in the KOA group.The FF value of subchondral bone marrow was negatively correlated with the T2 value of cartilage(r=0.412,P<0.001),whereas there was no statistically significant difference between T2 value of subchondral bone marrow and T2 value of cartilage(P > 0.05).5、Compared with the normal group,FF value of BM increased from the mild to severe cartilage injuries in the KOA group,but the difference was not statistically significant(P >0.05).There was no significant difference in the T2 value of BM among the groups.6、 Through multivariate analysis,it was concluded that the decrease of lipid content in IPFP and SPFP was an independent protective factor for the degree of cartilage injury,while the increase of IPFP and water content in cartilage was an independent risk factor for the degree of cartilage injury.Conclusion:1、IDEAL-IQ and T2 Mapping sequences could objectively and effectively reflect the changes of tissue fat and water content,which will help us to further deepen the understanding of the development of KOA,and provide an effective imaging reference for early diagnosis,prevention and treatment of OA.2、During the occurrence and development of KOA disease,IPFP plays a dual role of protection and damage to articular cartilage,while SPFP has a protective effect on cartilage.