Quantitative Evaluation Of Lumber Vertebra Osteoporosis With MRI T2* Mapping

Objective:To explore the clinical value of MRI T2*mapping technique for quantitative evaluation of the lumbar vertebrae osteoporosis in women.Method:A total 87 women(aged from 23 to 78 years old)participated in the study.All the patients underwent the routine lumbar MRI scan(including T1WI and T2WI),T2*mapping scan in 3.0T MR scanner and quantitative computer tomography(QCT)were performed simultaneously to obtain lumbar vertebrae bone mineral density(BMD).Pseudo-color imaging(T2*colour graph)of T2*mapping sequence automatically generated Bone mineral density of lumber vertebrae 2-4(L2-4)were measured and divided into 3groups according to the QCT results.Using BMD as the gold standard,the measured vertebrae were divided into three groups:osteoporosis group,osteopenia group and normal group.The T2*values of L2-4 vertebrae were measured respectively in the T2*colour graph.Using ANOVA if T2*and BMD values of the three groups obey normal distribution and the variance analysis is homogeneous,and Student-Newman-Keuls test is used for two-to-two comparison.Using Kruskal-Wallis test if the normal distribution is not obeyed,and BMD and T2*values of the three groups were compared by one-way ANOVA(F test).The SNK-q method was used to compare between every two groups.Spearman correlation analysis was performed on the measured T2*and BMD values.At last,T2*pseudo-color imaging was observed by two senior doctors.The sensitivity and specificity of T2*values in diagnosis of lumbar osteoporosis and osteopenia were analyzed by receiver operating characteristic curve(ROC).The consistency of measurement results between two observers and within observers was determined by intraclass correlation coefficients(ICC).Result:The total number of the vertebral bodies was 261 of 87volunteers recruited,including 115 normal vertebral bones,78 osteopenia vertebral bones,68 osteoporosis vertebral bones.The normal group average BMD value(mg/cm~3)was 145.021±18.941,the average T2*value was8.390±4.171,the osteopenia group average BMD value was 97.903±16.182,the average T2*value was 12.252±3.361,the osteoporosis group average BMD value was 59.093±18.705,and the average T2*value was 15.543±4.896.There were a significant negative correlation between BMD value and T2*value of the normal vertebral bone group,the same is true of the osteopenia group and osteoporosis group(the r values were-0.47,-0.52,-0.57 respectively,P<0.05).The area under ROC curve for diagnosing osteopenia and osteoporosis were 0.76 and 0.79,respectively.The ROC curve showed that when the cut-off T2*value was 12.48,the sensitivity and specificity for diagnosis of osteoporosis were 0.82 and 0.59 respectively.The cut-off T2*value was 17.13,the sensitivity and specificity were 0.87 and 0.56 respectively.Conclusion:The women BMD value of lumber vertebrae decreased and the corresponding T2*value increased.There was a significant negative correlation between T2*value and BMD.The T2*mapping sequence has the clinical application in quantitatively measure the bone mineral density of the lumber vertebrae and evaluate osteoporosis without invasiveness.