■确定骨密度作为骨质量替代参数的金标准是通过双能X射线吸收法(DXA)测量骨矿物质密度(BMD),最常见于腰椎(L1-L4)。计算机断层扫描(CT)数据通常可用于脊柱手术前的手术计划,但是目前这些信息还没有标准化的骨质量评估。此外,在生物力学研究的背景下,测量Hounsfield单位(HU)也非常重要。这项体外研究旨在基于诊断CT扫描比较DXA和HU的BMD。此外,提出了量化骨骼内局部密度变化的方法。
■研究了来自44名身体捐献者(年龄84.0±8.7岁)的一百七十六个椎骨(L1-L4)。在整个椎骨上进行DXA测量以确定BMD,以及厚度为1毫米的轴向CT扫描。使用MimicsInnovationSuite图像处理软件(MaterialiseNV,鲁汶,比利时),两卷(整个椎骨与每个椎骨都形成了海绵骨),它们又在它们的左右两侧分开。从总共六卷中,确定各自的平均HU。将整个椎骨的HU和刚毛的HU与相应椎骨的BMD进行比较。侧特异性差异计算为相对值。
■全骨和海绵状HU与BMD显着相关(P>0.001;α=0.01)。发现呈正线性相关,全骨HU(R=0.72)比海绵HU(R=0.62)更明显。当比较每个椎骨的左右两侧时,发现一侧的HU平均比另一侧大10%。在某些情况下,左右海绵骨的差异可达170%。海绵状HU的侧面比较倾向于大于整个椎骨。
■从临床CT扫描中确定HU是评估骨骼质量的重要工具,主要通过在计算HU时包括皮质部分。不像BMD,HU可用于精确区分各个区域。HU的一些非常大的侧特异性梯度表明术前患者特定计划的巨大应用潜力。
UNASSIGNED: Gold standard for determining bone density as a surrogate parameter of bone quality is measurement of bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA), most commonly performed on the lumbar spine (L1-L4). Computed tomography (CT) data are often available for surgical planning prior to spine procedures, but currently this information is not standardized for bone quality assessment. Besides, measuring the Hounsfield-Units (HU) is also of great importance in the context of biomechanical studies. This in vitro study aims in comparing BMD from DXA and HU based on diagnostic CT scans. In addition, methods are presented to quantify local density variations within bones.
UNASSIGNED: One hundred and seventy-six vertebrae (L1-L4) from 44 body donors (age 84.0±8.7 years) were studied. DXA measurements were obtained on the complete vertebrae to determine BMD, as well as axial CT scans with a slice thickness of 1 mm. Using Mimics Innovation Suite image processing software (Materialise NV, Leuven, Belgium), two volumes (whole vertebra vs. spongious bone) were formed for each vertebra, which in turn were divided in their left and right sides. From these total of six volumes, the respective mean HU was determined. HU of the whole vertebra and just spongious HU were compared with the BMD of the corresponding vertebrae. Side specific differences were calculated as relative values.
UNASSIGNED: Whole bone and spongious HU correlated significantly (P>0.001; α=0.01) with BMD. A positive linear correlation was found, which was more pronounced for whole bone HU (R=0.72) than for spongious HU (R=0.62). When comparing the left and right sides within each vertebra, the HU was found to be 10% larger on average on one side compared to the opposite side. In some cases, the difference of left and right spongious bone can be up to 170%. There is a tendency for the side comparison to be larger for the spongious HU than for the whole vertebra.
UNASSIGNED: Determination of HU from clinical CT scans is an important tool for assessing bone quality, primarily by including the cortical portion in the calculation of HU. Unlike BMD, HU can be used to distinguish precisely between individual regions. Some of the very large side-specific gradients of the HU indicate an enormous application potential for preoperative patient-specific planning.