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首页> 外文期刊>Bone >Use of co-registered high-resolution computed tomography scans before and after screw insertion as a novel technique for bone mineral density determination along screw trajectory.
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Use of co-registered high-resolution computed tomography scans before and after screw insertion as a novel technique for bone mineral density determination along screw trajectory.

机译：在螺丝钉插入之前和之后使用共同注册的高分辨率计算机断层扫描作为确定沿着螺丝钉轨迹的骨矿物质密度的新技术。

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INTRODUCTION: Bone mineral density (BMD) is an important factor in the examination of the performance of bone instrumentation both in and ex vivo, and until now, there has not existed a reliable technique for determining BMD at the precise location of such hardware. This paper describes such a technique, using cadaveric human sacra as a model. METHODS: Nine fresh-frozen sacra had solid and hollow titanium screws placed into the S1 pedicles from a posterior approach. High-resolution micro-computed tomography (CT) was performed on each specimen before and after screw placement. All images were reconstructed with an isotropic spatial resolution of 308 mum, reoriented, and the pre-screw and post-screw scans were registered and transformed using a six-degree rigid-body transformation matrix. Once registered, two points, corresponding to the center of the screw at the cortex and at the screw tip, were determined in each scan. These points were used to generate cylindrical regions of interest (ROI) with the same trajectory and dimensions as the screw. BMD measurements were obtained within each of the ROI in the pre-screw scan. To examine the effect of artefact on BMD measurements around the titanium screws, annular ROI of 1 mm thickness were created expanding from the surface of the screws, and BMD was measured within each in both the pre- and post-screw scans. RESULTS: The registration process was accurate to 190 mum, with a precision of 189 mum and error in BMD measurement of +/-2% in repeated scans. BMD values in the cylindrical ROI corresponding to screw trajectories were not statistically different from side to side of each specimen (p=0.23). Metal artefact created significant differences in BMD values (p=0.001) and followed an exponential decay curve as distance from the screws increased, approaching a low value of approximately 20 mg HA cm(-3), but not disappearing completely. SUMMARY: CT in the presence of metal creates artefact, making measured BMD values near implants unreliable. This technique is accurate for determination of BMD, non-destructive, and eliminates the problem of this metal artefact through the use of co-registered scans. This technique has applications both in vitro and in vivo.
机译：简介：骨矿物质密度（BMD）是检查体内和体外骨器械性能的重要因素，迄今为止，还没有一种可靠的技术可以在此类硬件的精确位置确定BMD。本文以尸体人类sa骨为模型来描述这种技术。方法：九个新鲜冷冻的cra骨从后入路进入S1椎弓根，将实心和空心钛螺钉置入。在放置螺钉之前和之后，对每个样本进行了高分辨率的微型计算机断层扫描（CT）。所有图像均以308 mm的各向同性空间分辨率重建，并重新定向，并使用六度刚体转换矩阵对前扫描和后扫描进行记录和转换。一旦记录，在每次扫描中确定两个点，分别对应于皮质和螺钉顶端的螺钉中心。这些点用于生成具有与螺钉相同的轨迹和尺寸的圆柱感兴趣区域（ROI）。 BMD测量是在预扫描中在每个ROI内获得的。为了检查伪影对钛螺钉周围BMD测量的影响，从螺钉表面扩展了1 mm厚的环形ROI，并在螺钉前后扫描中分别测量了BMD。结果：配准过程精确到190微米，精度为189微米，重复扫描的BMD测量误差为+/- 2％。圆柱体ROI中与螺杆轨迹相对应的BMD值在每个样本的左右两侧均无统计学差异（p = 0.23）。金属假象在BMD值上产生了显着差异（p = 0.001），并且随着距螺钉的距离增加，遵循指数衰减曲线，接近约20 mg HA cm（-3）的低值，但并未完全消失。摘要：存在金属时，CT会产生假象，从而使植入物附近的BMD测量值不可靠。该技术对于确定BMD（非破坏性）是准确的，并且通过使用共配准扫描消除了这种金属伪像的问题。该技术在体内和体外都有应用。

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