Osteoporosis Model Of Cynomolgus Monkey Followed Up In DXA And MRI

Objective The castrated osteoporosis model of cynomolgus macaque was established and the process of osteoporosis was monitored with DXA and magnetic resonance imaging(MRI)chemical displacement imaging(CSI)and magnetic resonance spectroscopy(MRS),and the sensitivity and consistency of each index were compared.Materials and methods A total of 10 healthy adult female cynomolgus monkeys at the age of 11-12 in the same family were fed with common feed,and other diseases were excluded from the experimental animals before the experiment.Before the castration operation,the weight of each experimental animal was recorded and10 experimental monkeys were scanned with DXA and MRI.The images of the bone density of the lumbar vertebrae,the whole body bone mineral density and the percentage of body fat were obtained on DXA,and the numerical results were recorded.The signal intensity index(SIR)was obtained on CSI by the post-processing soft parts on the MRI.Water peak area(Sw),fat peak area(Sf),fat fraction(fat fraction,FF)and lipid water ratio(LWR)were obtained in the MRS spectrum image to evaluate the body fat content in the vertebral body.The region of interest(ROI)was manually outlined in the bone cancellous region of L5 vertebral body(ROI),and each site was measured 3 times.After the examination,the 10 female cynomolgus monkeys were treated with bilateral ovariectomy;the weight was measured at first,second,third months after the castration and the DXA and MRI examinations were performed and the same indexes were recorded before the castration.SPSS 19 software was used for statistical analysis and normal distribution test for samples.Two observers were selected to observe the difference between the zeroth and first,second,third MRI images before and after castration.Paired T test was used to compare the differences in body fat content,L5 vertebral body bone mineral density,SIR and Sw,Sf,FF and LWR between zeroth months and first,second,third months before castration.Pearson correlation analysis was used to evaluate the correlation between the total body fat content,CSI and MRS measured by DXA,SIR,FF,LWR and bone mineral density of L5 vertebrae,and the linear regression analysis was carried out with bone density as the dependent variable.Result There was no significant difference in bone mineral density,SIR,Sw,Sf,FF and LWR in L5 vertebrae of castrated macaques before zeroth months after castration and first months after castration.Zeroth months and second months before castration,the L5 vertebral body bone mineral density,L5 vertebral body SIR,Sf,FF and LWR were statistically different.There was no significant difference in BMD,fat percentage and Sw between the two groups.The total body fat percentage,L5 vertebral bone density,SIR,Sw,Sf,FF and LWR in the castrated rhesus monkeys were significantly different in the first zeroth months and third months after the castration,and there was no significant difference in the total bone mineral density.L5 lumbar vertebra bone density was negatively correlated with FF and LWR in MRS,and the correlation coefficient was r=-0.795,-0.786,P= < 0.001,0.001;there was no correlation with the body fat content(r=0.028,p=0.873)and SIR(r=-0.265,P=0.098).FF was positively correlated with SIR,and the correlation coefficient was r=0.350,P=0.027;L5 vertebral bone density and FF,LWR linear regression analysis calculated the absolute deviation coefficient absolute value B=4.738,4.075,P <0.001,F=26.53,P < 0.001,R2=0.689,and calculate the absolute value B=0.907,0.561,P < 0.001 of the standard partial regression coefficient of FF and lipid peak and water peak area.F=80.94,P < 0.001,R2=0.885.Conclusion1.During the formation of osteoporosis,MRS changes include the increase of fat peak area and the decrease of two parts of the water peak area.The change of the area under the fat peak is the main factor affecting the fat fraction FF,and the two technical indexes of the fat fraction FF and the signal intensity index SIR can be confirmed to a certain extent.2.The bone mineral density(BMD)of L5 vertebral body has a good correlation with the fat fraction FF,and the change of FF can be used as one of the auxiliary indexes reflecting the bone change during the formation of osteoporosis.3.The percentage of body fat(FTM)and signal intensity index(SIR)are important factors affecting the bone mineral density of the animal model after castration,but it can not be used as a quantitative marker to assist the diagnosis.4.For the changes of bone marrow fat cells and water molecules in the development of osteoporotic vertebral body,the accuracy of the conventional MRI sequence was significantly lower than that of the CSI and MRS parameters.