QCT骨密度测量的准确性试验方法和意义  

Methods and significance of accuracy fest of bone densitometry by QCT

作　　者：李大成[1] 姜维平[1] 黎本丰 罗刚[1] 周维彬[1] 尚家芸[2] 鄢青[2] 

机构地区：[1]四川省简阳市人民医院影像中心,简阳641400 [2]四川大学华西附属第四医院

出　　处：《中国骨质疏松杂志》2003年第3期217-219,256,共4页Chinese Journal of Osteoporosis

摘　　要：目的　目前国内尚未对QCT(定量CT法 )骨密度测量作准确性误差校正 ,笔者介绍了QCT准确度试验方法和为什么必须校正准确性误差。方法　用东芝CT机自带参考骨体模 (称东芝体模 )和软件为测量工具 ,对四川大学华西骨质疏松研究中心等研制的QCT骨体模 (称四川体模 )进行骨密度测量。将四川体模模拟被测人腰椎 ,置于 1 5cm深水浴中 ,东芝体模置于水浴和扫描台之间作参考标准。按照对人的腰 2、3、4椎骨扫描测量的条件 ,东芝QCT骨密度测量的方法进行操作 ,直至测量出骨密度值和显现出QCT图像为止。由于四川QCT体模内 3管羟磷灰石实际密度值为 50mg/cm3、1 0 0mg/cm3和 2 0 0mg/cm3,因而可以求出每管骨体模的测量值偏离实际值的 %大小。测量值大于实际值误差为正 ,反之为负。由于四川体模内有由大到小 3管骨密度呈线性分布 ,可以求得回归方程 ,用回归方程校正准确性误差较好。结果　测量四川体模从小到大 3管骨密度分别的准确性误差为 1 3 0 %、 5 2 6 %和 +3 85 % ,其分别的校正系数为 1 1 4 9、1 0 55和 0 963 ,相关系数r=0 998,回归方程为Y =1 2 0 75 +0 90 7X(X为测量骨密度 ,Y为校正后骨密度 )。在准确性试验期间CT机更换球管一支 ,更换球管后 ,四川体模从小到大 3管骨密度的准确性误差变为 30Objective The correction of accuracy errors in bone desitometry by QCT has not been carried out yet at present in China This article introduces the methods of QCT accuracy test and the reasons of accuracy error correction Methods A referential bone phantom (named Toshiba phantom) with software contained in a Toshiba CT machine was used as measuring tools to measure the BMD of the QCT bone phantom made by West China Osteoporosis Study Center of Sichuan University(named Sichuan phantom) The Sichuan phantom(mimicking human vertebrae) was put in a water bath 15cm deep while the Toshiba phantom was placed between the water bath and the scan table as a referential criterion Then the machine was operated according to the measuring conditions of scanning human lumbar vertebrae2,3,4 and the methods of Toshiba QCT densitometry until it measured out BMD values and obtaihed QCT images Because the real densities of the three sections of hydroxyapatite in Sichuan QCT phantom are 50mg/cm 3,100mg/cm 3,and 200mg/cm 3,respectively, the measured value of each section's deviating from its real value can be calculated, and the accuracy error in precentage is acquired The measured value larger than the real one is positive, aad the contrary is negative Also because the BMD of the three sections in the Sichuan phantom are distributed linearly from large to small, a regression equation can be calculated Then the regression equation was used to correct the accuracy errors Results The accuracy errors of the three sections measured from large to small in the Sichuan phantom were 13 0%, 5 26% and +3 85%,respectively; their correction coefficients were 1 149, 1 055 and 0 963,respectively, and the relative coefficient R was 0 998; the regression equation was Y=12 075+0 907X (X is the measured BMD, and Y the corrected one) During the test, one X ray tube of the CT machine was replaced After the replacement, the errors of Sichuan phantom from large to small changed to 30 54%, 9 97% and 0 0

关 键 词：QCT 骨密度 测量 准确性 试验方法 质量控制 骨质疏松 

分 类 号：R681[医药卫生—骨科学]