体内^(99)Tc^m和^(131)I本底对双能X线骨密度测定的影响

A study of the effects of different levels of ^(131)I and^(99)Tc^m background in the body on dual energy X-ray bone density measurement

目的 探讨体内1 31 I、99Tcm 放射性本底对双能X线吸收法 (DXA)骨密度 (BMD)测定的影响。方法 采用Sophos XRA骨密度仪 ,通过自身对比法 ,测定 35例受检者前臂远端、第 2～ 4腰椎(L2～ 4 )、右股骨颈及股骨颈三角 (Ward’s)区BMD为本底对照。在口服1 31 I370kBq 3h、静脉注射99TcmO-4185MBq后 3及 2 4h的不同放射性本底时 ,分别测定BMD ,结果进行比较。结果 与对照组比较 ,99Tcm3h组L2 、L3、Ward’s区BMD分别偏高 13.2 %、6 .2 %、10 .7% (P <0 .0 5 ) ,股骨区本底增高与BMD变化呈正相关 (r =0 .870 ,P <0 .0 1) ,其影响BMD测定的骨部位顺序为L2 、Ward’s、L3;股骨颈、L4 、前臂BMD差异无显著性 (P >0 .0 5 )。99Tcm 2 4h、1 31 I 3h本底组各部位骨BMD结果差异无显著性 (P >0 0 5 )。结论 99Tcm 甲状腺显像 3h本底影响DXABMD测定结果准确性 ,常规甲状腺功能测定1 31

Objective To investigate the effects of the different levels of 131 I and 99 Tc m background in the body on bone mineral density (BMD) measurement in dual energy X ray absorptiometry (DXA). Methods To compare the BMDs before and 3 h after oral 131 I 370 kBq and 3, 24 h after intravenous injection of 99 Tc mO - 4 185 MBq. The BMDs of the forearm, lumbar vertebrae 2～4 (L 2～4 ), right femoral neck, Ward's triangle of 35 subjects were measured four times (before and after the administration of the two radioactive tracers using in thyroid imaging) by Sophos XRA instrument made in France. The results were defined as 131 I 3 h, 99 Tc m 3, 24 h group and control group. Results As compared with the control group, the BMD of L 2～3 , Ward's triangle in 99 Tc m 3 h group were significantly increased by 13.2%, 6.2%, 10.7% ( P <0.05). The increase of BMD of Ward's triangle was positively correlated with the counts of background ( r=0.870, P <0.01). The order of the increases of BMDs was L 2, Ward's triangle, L 3. There was no significant difference among the BMDs of forearm, neck and L 4 in 99 Tc m 3 h group and all BMDs in 99 Tc m 24 h? 131 I 3 h group and control group ( P >0.05). Conclusion The accuracy of BMD in DXA is effected by 99 Tc m for thyroid imaging, but not by 131 I for routine thyroid uptake test.