The Application Of T2*-Mapping In Quantitative Evaluation Of The Normal Cartilage And Osteoarthritis Model Of Rhesus Monkey Knee

Objective:(1)To explore the distribution characteristics of T2*value,thickness and delamination of normal cartilage of rhesus monkey knee,so as to provide imaging basis for the quantitative evaluation of cartilage injury in rhesus monkey knee osteoarthritis model;(2)To explore the application value of T2*-mapping in evaluating osteoarthritis model of rhesus monkey knee,and to evaluate the efficacy of adipose stem cells in the treatment of knee osteoarthritisMethods:Twenty-two healthy rhesus monkeys aged 9-17 years old were included,regardless of gender,weight 4.8?9.0Kg.T1WI,PDWI,3D-FS-SPGR and T2*-mapping imaging of knee joint were performed with dynamic multipole 3.0T superconducting magnetic resonance uMR770 scanner and 12-channel rat body coil.According to the whole organ magnetic resonance imaging scoring system(WORMS),the knee cartilage was divided into 9 subregions:the region of patellar(P),the anterior region of medial femoral condyle(MFa),the central region of medial femoral condyle(MFc),the posterior region of medial femoral condyle(MFp),the anterior region of lateral femoral condyle(LFa),the central region of lateral femoral condyle(LFc),the posterior region of lateral femoral condyle(LFp),the medial region of tibial plateau(MT)and the lateral region of tibial plateau(LT).(1)The T2*values of articular cartilage in P,MFc,MFp,LFc,LFp,MT and LT and the thickness values of articular cartilage in normal knee joints of P,MFa,MFc,MFp,LFa,LFc,LFp,MT and LT were obtained in 22 rhesus monkeys.The differences of articular cartilage thickness and T2*values in different subregions were compared,and the signal and morphology of articular cartilage were observed.(2)The osteoarthritis model of bilateral knee joints of 10 healthy rhesus monkeys was established by modified Hulth method,the articular cartilage of one rhesus monkey was randomly selected for pathological examination,it was confirmed that the knee osteoarthritis model was established successfully.The remaining 9 rhesus monkeys were examined by MRI at 2.6 and 6 months after modeling.The articular cartilage before modeling was used as group A,for normal control group,group B at 2.6 months after modeling,and group C at 6 months after modeling.The T2*values of articular cartilage in P,MFc,MFp,LFc,LFp,MT and LT7 of 9 rhesus monkeys in group A,B and C were obtained.The differences of T2*among groups were compared,and the morphological changes such as signal,continuity and surface smoothness of articular cartilage in each group were observed.Results:1.The T2*value,thickness and cartilage stratification of normal cartilage of rhesus monkey knee:(1)There were significant differences in T2*values between MFP and LFC,LFC and LFP,LT and MT,MT and MFC,MT and MFP,MT and LFC,MT and LFP,P and MFC,P and LFC,P and LFP,P and MT,P and LT(P<0.05).There was no significant difference in T2*values of other subregions(P>0.05).The average value of T2*in the knee of rhesus monkey was(12.81�1.47)ms,the value of T2*in the the central region of lateral femoral condyle was(12.90�1.18)ms,the value of T2*in the central area and the lateral tibial plateau of femur the lateral region of tibial plateau was(12.37�1.17)ms,the value of T2*in the posterior region of lateral femoral condyle was(13.21�1.33)ms,the value of T2*in the medial region of tibial plateau was(14.59�1.03)ms,the value of T2*in the region of patellar was(11.29�0.84)ms.(2)There were significant differences in cartilage thickness between MFa and MFp,MFa and LFp,MFc and MFp,MFc and LFp,MFp and LFa,MFp and LFc,MFp and LFp,LFa and LFp,LFc and LFp,MT and LT,MT and MFa,MT and MFc,MT and LFa,MT and LFc,MT and LFp,LT and MFp,LT and LFp,P and MFa,P and MFc,P and MFp,P and MFp,P and MFp(P<0.01).There was no significant difference in cartilage thickness of other subregions(P>0.05).The average thickness of knee cartilage in rhesus monkeys was(0.89�0.32)mm.The thickness of cartilage in medial tibial plateau and the posterior region of medial femoral condyle,the posterior region of lateral femoral condyle,the region of patellar,the anterior and central regions of medial and lateral femoral condy andlemedial and medial femoral condyle and the lateral region of tibial plateau were(1.38�0.24)mm,(0.91�0.29)mm,(0.79�0.09)mm and(0.71�0.25)mm,respectively.(3)In the PDWI,3D-FS-SPGR and T2*-mapping gray scale images of normal rhesus monkey knee cartilage,the cartilage was divided into three layers in MFp region,MT region and LFp region.It is obvious in MFp region and MT region,high signal in surface and deep layer,low signal in middle layer,no delamination in the other subregions and slightly high signal in monolayer and high signal intensity,and the stratification phenomenon is the most significant in 3D-FS-SPGR.In T2*-mapping,with the increase of TE value,the delamination of cartilage gradually became blurred.Spearman correlation analysis showed that there was a correlation between cartilage delamination and cartilage thickness(r=0.710,P<0.01),and the delamination was obvious when cartilage thickness>1.2mm.2.T2*-mapping findings of knee osteoarthritis model in rhesus monkey:(1)It was proved by pathology that the animal model of osteoarthritis could be successfully constructed by the modified Hulth method.In the conventional PDWI,there were high signal shadows of thin strip and dot shape in the articular cartilage of OA model,the surface of cartilage was still smooth,and there were full-thickness cartilage defects in the operation model area;The 3D-FS-SPGR showed that the OA model articular cartilage was full-thickness cartilage defect in the operation modeling area,and the cartilage in other areas was continuous and smooth,and no clear abnormality was found in the signal;The pseudocolor images of T2*-Mapping showed that the color scale of articular cartilage was not continuous and smooth,the color of cartilage was mixed,and there was a speckled green color in the blue color.With the extension of time,there were spots of yellow and red in the blue color of articular cartilage;(2)The average T2*value of cartilage in group A was(12.62�1.15)ms,that in group B was(14.56�1.87)ms,and that in group C was(17.07�2.00)ms.The T2*value of cartilage in each subregion was not equal among group A,group B and group C,and the difference was statistically significant(P<0.01),the T2*value of cartilage in group B and C was higher than that in group A,the T2*value of cartilage in each subregion increased gradually with the extension of modeling time.Compared with group A,the T2*values of MFc and LFc in group B changed significantly.Compared with group A,the T2*values of MFc,MFp,LFc,LFp and P in group C changed more significantly,and the changes of T2*values in MFp and LFp in group C were the most significant compared with those in group B.(3)There was no significant difference in T2*value of MT cartilage between group A and group B(P>0.05),and there was significant difference in T2*value of cartilage between other subgroups(P<0.05).Conclusion(s):1.The normal knee cartilage of rhesus monkeys has delamination,which is mainly distributed in the area with thicker cartilage thickness,and the delamination phenomenon is the most significant in 3D-FS-SPGR sequence.2.There were differences in cartilage T2*values and thickness in different regions of normal knee joints of rhesus monkeys,it can provide imaging basis for the quantitative evaluation of cartilage injury in rhesus monkey knee osteoarthritis model.3.The T2*value of cartilage of rhesus monkey knee osteoarthritis model was higher than that of normal cartilage,and increased gradually with the extension of modeling time.T2*-mapping has a certain practical value in the quantitative evaluation of biochemical changes of rhesus monkey knee osteoarthritis cartilage,and can be used to evaluate the efficacy of adipose stem cells in the treatment of knee osteoarthritis.