ABSTRACT
Objective To evaluate MR relaxometry techniques and dual-energy X-ray absorptiometry (DXA) for the diagnosis of osteoporotic diseases in rats. Methods Thirty 3-month-old female rats were randomly divided (using completely randomized grouping method) into two groups (each contained 15 rats). Animals in group A without osteoporotic castration were included as normal controls, whereas osteoporotic castration was created in each animal in group B. Three parameters (BMC, BMD, Hbmdl)was measured for both groups by DXA at two time points, one immediately before the castration and another at the 12 th week after the castration. Then animals from the control group and the osteoporotic group went through the following three diagnostic procedures using a 1.5 T MR system: (1) A fast multi echo gradient echo (MEGRE) pulse train sequence with different inter-echo intervals (1000, 500, 400, 300, 200, 100) to obtain the T_2~* value. (2) A multi-echo fast spin echo sequence to obtain the T_2map. (3) A conventional spin-echo (CSE) sequence to obtain the T_1map. The statistical difference between group A and group B was tested by t-test to analyze parameters. And, the most significant parameter for diagnosis ofosteoporotic diseases was picked out from all parameters by Fisher Sequential diseriminant analysis. At the end of experiments, animals were killed and histopathological examination was performed on the femurs of animals from both control and osteoporotic groups. Results (1) Histopathological examination confirmed the presence of osteoperosis in all animals in group B. (2) BMD was picked out from 3 DXA parameters (BMC,BMD,Hbmdl) by fisher stepwise discriminant analysis, and its discriminant rates was 87.6%. (3) All 2-sample t-test results(t=6.20, 4.79, 5.18, 5.22, 5.59, 4.37, 6.14, 5.12, 5.09, 4.99, 5.57, 4.84, 4.07, 2.98, 6.75 individually) for MR relaxometry parameters(T_2~* 1000,R_2~* 1000,T_2~* 500,R-2~* 500,T_2~* 400,R_2~* 400,T_2~* 300,R_2~* 300,T_2~* 200, R_2~* 200, T_2~* 100, R_2~* 100, T_2map, R_2map, T_1map) showed statistically significant differences between groups A and B (P=0.01 for T_2~* map, P=0.00 for all other parameters) except the R_2map(P=0.07). (4) Using fisher stepwise discriminafion method in the analysis of 14 parameters of MR relaxometry techniques and 3 parameters of dual X-ray absorptiometry(T_2~* 1000,T_2~* 500,T_2~* 400,T_2~* 300,T_2~* 200,T_2~* 100,T_2map, R_2~* 1000, R_2~* 500, R_2~* 400, R_2~* 300, R_2~* 2OO, R_2~* 100,T_1map,BMC,BMD,Hbmdl), we found that the most significant difference was from the T_2map and T_1map. Conclusions The MR relaxometry parameter-T_2map in the present study is shown to be appropriate parameter for the diagnosis of osteoperotie diseases, and stability of magnetic field plays an important role in this process. It would be the optimal method to make a diagnosis of osteoporotic diseases with both MR relaxometry and DXA technological means.
ABSTRACT
Objective To study the correlation of the bone mineral density (BMD) and the body composition components of body mass index (BMI), FAT and LEAN in Chinese obesity. Methods There were 150 cases in obesity group diagnosed by BMI, including 75 males[ median age 46 years, mean weight (89. 64±8. 33) kg] and 75 females[ median age 45 years, mean weight (77.23±6. 85) kg]. There were 150 persons with normal BMI in the control group, including 75 males [ ( median age 47 years, mean weight (62. 34±5.72) kg] and 75 females [ median age 45 years, mean weight (50. 16±5.06) kg]. The body height and weight of 300 persons in two groups were measured respectively and, simultaneously calculated the BMI. These data and the body composition parameters measured by the dual energy X-ray absorptiometry (DEXA) in these two groups were compared and analyzed. The data obtained used two-sample t-test analysis, bi-variable correlation used Pearson linear correlation analysis and multi-variable correlation used multiple linear regression analysis. Results FAT of arms, legs, trunk and total body of male cases in obesity group was (2.90±0.57), (7.48±1.46), ( 15.67±3.05 ), ( 30.92±5.94 ) kg respectively, FAT% was ( 30.9±5.1 ) %, ( 30.6±5.8 ) %, ( 37. 3±4.7 ) %, ( 35.1±4.4 ) % respectively, it was significantly higher than that in control group [ FAT was ( 1.12±0. 64 ), (3.27±1.22), (6. 71±3. 29 ), ( 11.61± 5. 16) kg respectively,FAT% was( 15.4±4. 8)%, ( 16. 5±5.0)%, (21.8±5.8)%, ( 18.6±5. 3)% respectively] ,P <0. 01 ;LEAN of trunk and total body of male cases in obesity group was (27.65±4. 08), (57. 09±7.08 ) kg respectively ; BMD was ( 0. 99±0. 09 ), ( 1.22±0. 09 ) g/cm2 respectively, it was significantly higher than that in control group [ LEAN was ( 22. 89±1.68 ), (48.89 s 3.72 ) kg respectively, BMD was( 0. 89±0. 07 ), ( 1.15±0. 06 ) g/em2 respectively ], P < 0. 01 ; LEAN of arms and legs of male cases in obesity group was(6.22±0.92), (17.31±2.65) kg respectively; BMD was(0.92±0. 04), (1.31±0. 09)g/cm2 respectively,and there were no statistical significance compared with those in control group [ LEAN was ( 5.99±0. 72 ), ( 16. 83±1.67 ) kg respectively, BMD was ( 0. 90±0. 08 ), ( 1.29± 0.09) g/cm2 respectively]. FAT of arms, legs, trunk and total body of females in obesity group was (3.78±1.53), ( 12. 61±3.72), ( 17. 56±2. 59), (33.71±6. 96) kg respectively, FAT% was (33.8± 4.0)%,(40. 1±6.9)%,(43.9±4.9)%, (43.5±4.2)% respectively, LEAN was(7.28±0.94), ( 14. 40 ±2. 05 ), ( 20. 71±3.08 ), ( 43.43±5.69 ) kg respectively, BMD was ( 0. 86±0. 08 ), ( 1.27± 0. 12),(0.95±0. 14), (1.19±0.09)g/cm2 respectively, they were significantly higher than those in control group [ FAT was(2. 04±0. 79), (3.79±0. 94), (6. 89±2. 56), ( 14. 68±3.57) kg respectively, FAT% was (27. 2±4. 5 ) %, ( 29. 6±3.9 ) %, ( 31.0±3.8 ) %, ( 25.9±4. 9 ) % respectively, LEAN was (5. 25±0. 63), ( 10. 65±1.44), ( 16. 65±1.50), (33. 10±3.22) kg respectively, BMD was (0. 78± 0. 04), ( 1.11±0. 09), ( 0. 82±0. 07 ), ( 1.05±0. 07 ) g/cm2 respectively ], P < 0. 01. Conclusion The significantly increasing of fat tissue in all parts of body is a major cause of change of body composition components in obesity. FAT in the trunk increases more obviously than that in other parts of the body in both males and females. The change of distribution of FAT and LEAN can obviously influence BMD.