用于QCT的新型脊椎骨矿密度体模的研制

Development of a new type of vertebral bone mineral density phantoms for QCT

为改进QCT在检测脊椎骨矿密度中与体模标准样品的比较精度,研制新型的QCT五标样体模。采用聚乙烯塑料同适量的碳酸钙及氧化镁混合,并用数控塑料造粒机加工成软组织的辐射等效颗粒材料(称软组织材料)。接着用颗粒材料同适量的羟磷酸钙混合,然后用数控塑料注射机加工成骨组织的辐射等效材料(称骨材料)。将骨材料机械加工成含5种羟磷酸钙密度的骨标准样品(称骨标样),将骨标准样品嵌入软组织材料块中,加工成五标样新型体模。通过对CP体模进行性能测试,并与国内外体模作对比,结果表明:新型体模的5个骨标样的羟磷酸钙密度分别为0,50,100,150,200 mg/cm^3,各骨标样的羟磷酸钙密度与相应的CT数呈线性相关,其相关系数r≥0.999 96,用于QCT检测脊椎骨矿密度测量有利于提高线性拟合精度。

In order to improve the accuracy of QCT in the detection of vertebral bone mineral density compared with standard sample of phantoms,a new QCT 5 standard phantoms were developed.It was first mixed with a proper amount of calcium carbonate and magnesium oxide with polyethylene plastic and processed into a radiation equivalent granular material(hereinafter called soft tissue material)in soft tissue with a numerical control plastic granulator.The granular material was mixed with the appropriate amount of calcium hydroxyphosphate and then processed into a radiation equivalent material(hereinafter called bone material)of bone tissue with a numerically controlled plastic injection machine.The bone material was machined into a standard bone sample containing 5 kinds of calcium hydroxyl phosphate(hereinafter called bone standard)and inserted into a soft tissue block to form a new type of phantom with 5 standard samples.Through the performance test of CP phantom used by CT machine and compared with domestic and abroad phantoms,the results show that the density of 5 bone standard calcium hydroxyapatite obtained from the new phantom was 0,50,100,150,200 mg/cm^3 respectively.The content of hydroxyapatite in each bone sample was linearly correlated with the corresponding CT number,and the correlation coefficient was more than 0.999 96.It is helpful to improve the accuracy of linear fitting for measuring vertebral mineral density by QCT.