University of Cambridge, Department of Engineering, Trumpington Street, Cambridge, UK.
Med Image Anal. 2012 Jul;16(5):952-65. doi: 10.1016/j.media.2012.02.008. Epub 2012 Feb 28.
There is growing evidence that focal thinning of cortical bone in the proximal femur may predispose a hip to fracture. Detecting such defects in clinical CT is challenging, since cortices may be significantly thinner than the imaging system's point spread function. We recently proposed a model-fitting technique to measure sub-millimetre cortices, an ill-posed problem which was regularized by assuming a specific, fixed value for the cortical density. In this paper, we develop the work further by proposing and evaluating a more rigorous method for estimating the constant cortical density, and extend the paradigm to encompass the mapping of cortical mass (mineral mg/cm(2)) in addition to thickness. Density, thickness and mass estimates are evaluated on sixteen cadaveric femurs, with high resolution measurements from a micro-CT scanner providing the gold standard. The results demonstrate robust, accurate measurement of peak cortical density and cortical mass. Cortical thickness errors are confined to regions of thin cortex and are bounded by the extent to which the local density deviates from the peak, averaging 20% for 0.5mm cortex.
越来越多的证据表明，股骨近端皮质骨的局灶性变薄可能使髋关节容易发生骨折。在临床 CT 中检测到这种缺陷具有挑战性，因为皮质可能比成像系统的点扩散函数薄得多。我们最近提出了一种模型拟合技术来测量亚毫米皮质，这是一个不适定的问题，通过假设皮质密度的特定固定值来正则化。在本文中，我们通过提出和评估一种更严格的方法来估计固定皮质密度来进一步开展这项工作，并将范例扩展到除厚度之外还包括皮质质量（mg/cm^2 矿物质）的映射。使用高分辨率的微 CT 扫描仪进行的十六具尸体股骨的测量对密度、厚度和质量估计值进行了评估，为金标准提供了参考。结果表明，皮质的峰值密度和皮质质量的测量是稳健和准确的。皮质厚度的误差局限于皮质较薄的区域，并且受到局部密度偏离峰值的程度的限制，平均为 0.5mm 皮质的 20%。
