Experimental Study On The Distribution Of ^99mTc-MDP In The Repair Of Femoral Bone Injury In Rabbits

Objective:To investigate the distribution of bone imaging agent 99mTc-MDP at different stages of bone injury repair.Methods:A total of 30 models of femur bone injury in rabbits were made by electric drill method.The left femur is the model side and the right femur is the control side.The model rabbit was made without any intervention after the model rabbit was made.According to the different stages of bone injury repair,they were divided into three groups（group A,group B and group C）.From the day of making the model,the first week to the natural repair is set to group A,the second week from the day of making the model to the repair is group B,the third week from the day of making the model to the repair is group C.There were 10 model rabbits in each group.The ear margin of each group was injected intravenously with 37 MBq ^99mTc-MDP at different stages of bone injury repair.After the bone imaging agent was metabolized in the model rabbit for 2 hours,SPECT/CT femur bone scan was performed.In the post-processing system,the region of interest was defined as the site of bone injury on the model side and the normal area on the control side,and the corresponding radiation count was obtained.The test radiometric count value was compared with the control side radiometric count value to obtain the odds ratio of T/B,and the statistical method of single factor variance analysis was applied to compare whether there was any difference in T/B among the three groups.LSD is compared in pairs.The maximum radiometric value Max of the test and control sides of rabbits in each group was obtained,and the statistical method of paired t test was used to compare the radiometric value differences between the test and control sides of rabbits in each group.The rabbits were sacrificed after the SPECT/CT scanning,taken the test femur and the phosphor screen imaging plate was exposed to light for 30min.The phosphor screen imaging software was applied to analyze the image data,calculate the light intensity in the image area of interest,and compare the in vitro radioactivity differences of the three groups of model rabbits.The test defect area was cut into small bone pieces and the hard tissue section of rabbit thigh defect was made by using hard tissue slicer and slice mill.The hard tissue sections with defects were coated with nucleated-4 latex and exposed in 4 refrigerators for 48 hours.Development and fixing,autoradiography correlation was performed.After HE staining,the specific location of silver particle deposition in three groups of bone injury tissue sections before and after autoradiography was observed under the microscope.Results:The SPECT/CT scanning plane image of rabbit femur bone injury model showed that the distribution of imaging agent ^99mTc-MDP increased at different stages of bone repair.All three groups of model rabbits showed higher concentration of radiation on the test side than on the control side.The T/B values of radioactive Max among the three groups show as follows:At the second week,the concentration of^99mTc-MDP in the bone defect area was higher than that in the other two groups.There were significant differences in the T/B values（group A 1.16±0.14,group B 1.39±0.23,group C 1.18±0.10）of the radiometric counts among the three groups（F=5.83,p=0.02）.There was a significant difference between group A and group B（p=0.01）.The difference between group A and group C was not significant（p=0.83）.There was a significant difference between group B and group C（p=0.02）.Comparison of maximum radiometric counts on the mold side and control side in three groups,group A（the test side 50.00±12.25,the control side 43.20±9.57,p=0.01）,group B（the test side 55.10±9.26,the control side 44.30±6.50,p<0.01）,group C（the test side 55.10±9.26,the control side 44.30±6.50,p=0.02）.There were significant differences between the maximum radiation count on the test side and the control side in the three groups,all of which were statistically significant.Group B showed the most significant difference.The phosphor screen image showed that there was a significant difference in radioactivity uptake in the three groups of modeled lateral bone samples（F=8.25,p=0.02）.Compared with each other,there was A significant difference between group A and group B（p<0.01）.The difference between group A and group C was not significant（p=0.31）.There was a significant difference between group B and group C（p=0.03）.Silver particles were deposited in both intracellular and extracellular during different stages of bone repair in osteocytes and osteoblasts under autoradiography.Conclusion:During the repair of femoral injury,^99mTc-MDP was concentrated in the stage of osteogenesis inactivit,in SPECT/CT imaging the mechanism of imaging agent entering bone tissue in addition to the chemisorption of hydroxyapatite,there are other pathways.