Université de Lyon, Université Lyon 1, INSA-Lyon, France.
Med Phys. 2012 Apr;39(4):2229-38. doi: 10.1118/1.3697525.
The fundamental role of the osteocyte cell network in regulating the bone remodeling has become evident in the last years. This has raised the necessity to explore this complex three-dimensional interconnected structure, but the existing investigation methods cannot provide an adequate assessment. The authors propose to use parallel beam synchrotron radiation computed tomography at the nanoscale to image in three dimensions the osteocyte lacunocanalicular network. To this aim, the authors study the feasibility of this technique and present an optimized imaging protocol suited for the bone cell network. Moreover, they demonstrate the multifaceted information provided by this method.
The high brilliance of synchrotron radiation combined with state of art detectors permits reaching nanoscale spatial resolution. With a nominal pixel size of 280 nm, the parallel beam computed tomography setup at the ID19 experimental station of the ESRF is capable of imaging the bone lacunocanalicular network, considering that the reported diameter of canaliculi is in the range 300-600 nm. However, the actual resolution is limited by the detector and by the radiation dose causing sample damage during the scan. The authors sought to overcome these limitations by optimizing the imaging setup and the acquisition parameters in order to minimize the necessary radiation dose to create the images and to improve the spatial resolution of the detector.
The authors achieved imaging of the osteocyte cell network in human bone. Due to the optimization of the imaging setup and acquisition parameters, they obtained simultaneously a radiation dose reduction and an increase of the signal to noise ratio in the images. This permitted the authors to generate the first three-dimensional images of the lacunocanalicular network in an area covering several osteons, the fundamental functional units in the bone cortex. The method enables assessment of both architectural parameters of the microporosity and of mineralization degree in the bone matrix. The authors found that the cell network is dense and connected inside osteonal tissue. Conversely, the cell lacunae are sparse, unorganized, and disconnected in interstitial tissue.
The authors show that synchrotron radiation computed tomography is a feasible technique to assess the lacunocanalicular network in three dimensions. This is possible due to an optimal imaging setup in which the detector plays an important role. The authors could establish two valid setups, based on two different insertion devices. These results give access to new information on the bone cell network architecture, covering a number of cells two orders of magnitude greater than existing techniques. This enables biomedical studies on series of samples, paving the way to better understanding of bone fragility and to new treatments for bone diseases.
近年来，骨细胞网络在调节骨重塑中的基本作用已经显而易见。这就需要探索这种复杂的三维相互连接的结构，但现有的研究方法无法提供充分的评估。作者提出使用纳米级同步加速器微束辐射计算机断层扫描技术对骨细胞陷窝管网进行三维成像。为此，作者研究了该技术的可行性，并提出了一种适合骨细胞网络的优化成像方案。此外，他们还展示了该方法提供的多方面信息。
同步加速器辐射的高亮度与最先进的探测器相结合，可实现纳米级空间分辨率。在 ESRF 的 ID19 实验站的平行束计算机断层扫描装置中，名义像素尺寸为 280nm，能够对骨陷窝管网进行成像，因为报道的小管直径在 300-600nm 范围内。然而，实际分辨率受到探测器和扫描过程中引起样本损坏的辐射剂量的限制。作者通过优化成像装置和采集参数来克服这些限制，以最小化创建图像所需的辐射剂量，并提高探测器的空间分辨率。
作者成功地对人骨中的骨细胞网络进行了成像。由于成像装置和采集参数的优化，他们在获得图像的辐射剂量降低和信噪比提高的同时，获得了图像。这使得作者能够在覆盖几个骨单位的区域中生成第一个骨陷窝管网的三维图像，骨单位是骨皮质中基本的功能单位。该方法能够评估骨基质中微孔的结构参数和矿化程度。作者发现，细胞网络在骨单位组织内密集且相互连接。相反，细胞陷窝在间质组织中稀疏、无组织且不连接。
作者表明，同步加速器微束辐射计算机断层扫描是一种可行的三维评估陷窝管网的技术。这是由于成像装置的优化，探测器在其中起着重要作用。作者可以基于两种不同的插入装置，建立两种有效的装置。这些结果为骨细胞网络结构的新信息提供了访问途径，涵盖了比现有技术多两个数量级的细胞数量。这使人们能够对一系列样本进行生物医学研究，为更好地理解骨脆弱性和治疗骨疾病铺平道路。
