A Quantitative MRI Research For Changes Of Articular Cartilage In Osteoarthritis Of Knee

Objective: To measure the T2 values of deep,middle,superficial layers of articular cartilage in knee joint by quantitative MRI—T2 mapping.To discuss the difference in T2 value among the Asymptomatic,Symptomatic,Patients scheduled for Knee Replacement Surgery,to obtain the gist for the imaging diagnosis in early KOA.Materials and Method: Three kinds of volunteers were chosen in our study to collect the knee MR images: Asymptomatic knee(Group A),Symptomatic knee(Group B)and Patients scheduled for Knee Replacement Surgery(Group C),185 knees in total.In Group A and Group B: T2 values in deep,middle,and superficial layers(three values of each layer to get the average T2 value)of knee cartilage were measured by dividing the whole knee articular cartilage into thirteen sub-regions: PL,FMA,FMC,FMP,FLA,FLC,FLP,TMA,TMC,TMP,TLA,TLC,TLP(excluding the thin or morphologically damaged cartilage which couldn't be measured by zonal way).In Group C were measured one,two or three layers on each sub-region which depends upon the thickness,(three values of each layer to get the average T2 value).T2 value of full thickness on each sub-region is the average of the three layers in Group A,B and C.Compare the T2 values of full thickness cartilage of PL,FMC,FMP,FLC,FLP sub-region among Group A,B,C;likewise,T2 values in deep,middle and superficial layers of 13 sub-regions were compared between Group A and Group B.Further,T2 values of each layer was compared among FMC,FMP,FLC and FLP sub-regions in Groups A and B;and T2 values on each layer of PL,FMC,FMP,FLC and FLP sub-regions between Group A and B.Result:(1)On colorized T2 mapping image,there is a zonal characteristic of the cartilage color: yellow in deep layer,green in middle layer,blue in superficial layer(threshold 0-80ms);(2)on full thickness cartilage T2 values of PL,FMC,FMP,FLP sub-region had statistically significant different between Group A and Group B,Group A and Group C(P<0.05),T2 value of full thickness cartilage in FLC sub-regions had statistically significant differences in between Group B and Group C(P<0.05);(3)In Group A,cartilage T2 values of the 13 sub-regions had statistically significant differences among deep,middle and superficial layer(P<0.05),except FMP,FLP,TMP,TLA,TLP sub-region's middle and superficial layer,and the T2 values of superficial layer>middle layer>deep layer.In Group B,cartilage T2 values of the PL,FMA,FMC,FLA,FLC,TMC,TLA,and TLC sub-regions had statistically significant differences among deep,middle,and superficial layers(P<0.05),as well as between deep and superficial layers;and deep and middle layers of the FMP,FLP,and TLP sub-regions(P<0.05);(4)In Group A,on comparison of the same side compartment,cartilage T2 values of deep layer ?middle layer had statistically significant differences between FMC and FMP(P<0.05),cartilage T2 values of deep,middle,and superficial layers had statistically significant differences between FLC and FLP(P<0.05).On comparison between middle and lateral side,cartilage T2 values of middle layer were significantly different between FMC and FLC(P<0.05).In Group B,on comparison between the same side of compartment,cartilage T2 values of deep layer?middle layer had statistically significant differences between FMC and FMP,and between FLC and FLP(P<0.05.On comparison between the middle and lateral side,cartilage T2 values of middle layer had significant differences between FMC and FLC(P<0.05),and between middle layer and superficial layer were significantly different between FMP and FLP(P<0.05);(5)Cartilage T2 values of deep,middle,and superficial layers in FMC and FMP sub-regions had significant differences between Group A and Group B.On comparison between deep and middle layers in PL,FMC,FMP,FLC,FLP sub-regions had statistically significant differences between Group A and Group B(P<0.05).Conclusion:(1)The T2 value of superficial layer>middle layer>deep layer in normal cartilage;(2)The early stage of cartilage degeneration caused by the change of water and cartilage fiber is easier to be detected by T2 value of deep layer;(3)The T2 value of femur non-bearing area is higher than bearing area in both Asymptomatic and Symptomatic Knee cartilage,it's necessary to separate the knee cartilage in different subregion for research;(4)It's a diffusibility change of biochemistry content in cartilage before morphology change.