Quatitative And Functional MRI Of Osteoporosis In Ovariectomized Rabbits: Comparison With Bone Mineral Density And Pathohistology

Partâ… Establishment of osteoporosis model in ovariectomized rabbitsand quantitative study with MR T₂^* relaxation timeObjective To establish a primary osteoporosis rabbit model by ovariectomy(OVX)and measure lumbar spine T₂^* and R₂^* MR relaxation parameters in osteoporosis rabbit andcompare them with bone mineral density(BMD)and histomorphology.Material and methods:22 New Zealand white rabbits were randomly divided into 2groups,including experimental group(n=12)and control group(n=10).Bilateralovariectomies were applized in experimental group.MRI,DEXA and pathohistology examwere respectively performed both groups in 3,5,7 moths after OVX.T₂^*,R₂^* and BMD oflumber spine were obtained.Results:BMD of lumber spine in OVX group in postoperative 7m was obviouslydecreased compared to control group(P＜0.05).In postoperative 3m lumber spine T₂^* andR₂^* value had no difference both groups;but the significant difference were found inpostoperative 5m(P＜0.05)and 7m(P＜0.001),T₂^* was significantly increased and R₂^* wasobviously decreased.Histomorphological characteristics showed the trabecular bone werethinner,interrupted and trabecular spaces enlarged and trabecular number lessened in OVXgroup.Lumber spine T₂^* value was significant inverse correlation with BMD in OVXgroup(r=-0.599,P＜0.001),and R₂^* was positive association with BMD(r=0.746,P＜0.001). Conclusion:OVX can succeed to induce rabbit model of osteoporosis in postoperative7m.T₂^* and R₂^* MR relaxation time can sensitively detect trabecular bonemicro-architecture changes in osteoporosis rabbit and are significant correlation with BMD.Combination with T₂^*,R₂^* and BMD can better reflect bone strength and bong qualityvariation in early OP.Partâ…¡Lumbar spine bone marrow perfusion in osteoporosis rabbit withdynamic contrast enhancement MRI:correlation with BMD and MVDObjective:To use dynamic contrast enhancement(DCE-MRI)to assess lumbar spinebone marrow blood perfusion in osteoporosis rabbit and correlate perfusion with bonemineral density(BMD)and microvessel density(MVD).Material and methods:22 New Zealand white rabbits were randomly divided into 2groups,including experimental group(n=12)and control group(n=10).Bilateralovariectomies were applized in experimental group.DCE-MRI,DEXA andimmunohistochemistry exam were respectively performed both groups in 3,5,7 mothsafter OVX.Vertebral maximum percentage of enhancement(Emax),enhancement slope(ES),BMD and MVD were measured from them.Results:BMD of lumber spine in OVX group in postoperative 7m was obviouslydecreased compared to control group(P＜0.05).In postoperative 3 and 5m lumber spinebone marrow Emax and ES had no difference both groups(P＞0.05),however the significantdifference were found in postoperative 7m(P＜0.05),Emax and ES were significantlydecreased in OVX group.MVD of vertebral marrow was 67.58±11.6 in control group and39.32±9.54 in OVX group,which were significant difference between them (P＜0.05).Vertebral marrow Emax and ES were significant positive correlation with BMDand MVD in 7m OVX group(r=0.714,0.820,0.866 and 0.771,P＜0.05).Conclusion:Lumbar spine bone marrow perfusion is significantly decreased inosteoporosis rabbit,similarly vertebral MVD obviously reduce too.DCE-MRI can providemore information about osteoporosis blood perfusion.Emax and ES are significant.correlation with BMD and MVD.This result may suggest a vascular component in thepathogenesis of OP and is helpful to diagnosis and treatment of OP.Partâ…¢Vertebral marrow fat content in osteoporosis rabbit with MRspectroscopy:compare with perfusion,BMD and pathohistologyObjective:To use hydrogen 1(¹H)MR spectroscopy to assess vertebral marrow fatcontent in osteoporosis rabbit and correlate with vertebral perfusion,bone mineral density(BMD)and pathohistology.Material and methods:22 New Zealand white rabbits were randomly divided into 2groups,including experimental group(n=12)and control group(n=10).Bilateralovariectomies were applized in experimental group.¹H MRS,DCE-MRI,DEXA andpathohistologic exam were respectively performed both groups in 3,5,7 moths after OVX.Lumbar spine marrow lipid water ratio(LWR),fat content(FC),vertebral maximumpercentage of enhancement(Emax),enhancement slope(ES)and BMD were measuredfrom the exams.Results:BMD of lumber spine in OVX group in postoperative 7m was obviouslydecreased compared to control group(P＜0.05).In postoperative 3 and 5m lumber spinebone marrow LWR and FC had no difference both groups(P＞0.05),however the significant difference were found in postoperative 7m(P＜0.001),LWR and FC were significantlyincreased in OVX group.Pathohistologic characteristics showed trabechular boneobviously reduced and adipocyte hyperplasia in enlarged trabecular space.In control groupvertebral marrow LWR and FC were significantly increased follow with rabbit age(P＜0.05),meanwhile OVX rabbit LWR and FC were increased more significantly thancontrol group(P＜0.001).Vertebral Emax and ES were significantly decreased inpostoperative 7m of OVX group(P＜0.05).Vertebral marrow LWR and FC were significantinverse correlation with Emax,ES and BMD in 7m OVX group.Conclusion:¹H MRS potentially may be applied to the noninvasive assessment ofmarrow lipids in osteoporosis and help establish the role of lipid in the pathgenesis ofosteoporosis.The increase in vertebral marrow fat content in osteoporosis is correspondingto reduction in perfusion and decrease in BMD.There is clear relationship between marrowfat and perfusion and BMD.