Van de Casteele Elke, Perilli Egon, Van Aarle Wim, Reynolds Karen J, Sijbers Jan
iMinds, VisionLab, Department of Physics, University of Antwerp (CDE), Universiteitsplein 1, Building N, 2610, Antwerp, Belgium.
Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, GPO Box 2100, Adelaide, SA, 5001, Australia.
J Bone Miner Metab. 2018 Jan;36(1):40-53. doi: 10.1007/s00774-017-0815-x. Epub 2017 Feb 27.
This study aimed at assessing the feasibility of a discrete algebraic reconstruction technique (DART) to be used in in vivo small animal bone studies. The advantage of discrete tomography is the possibility to reduce the amount of X-ray projection images, which makes scans faster and implies also a significant reduction of radiation dose, without compromising the reconstruction results. Bone studies are ideal for being performed with discrete tomography, due to the relatively small number of attenuation coefficients contained in the image [namely three: background (air), soft tissue and bone]. In this paper, a validation is made by comparing trabecular bone morphometric parameters calculated from images obtained by using DART and the commonly used standard filtered back-projection (FBP). Female rats were divided into an ovariectomized (OVX) and a sham-operated group. In vivo micro-CT scanning of the tibia was done at baseline and at 2, 4, 8 and 12 weeks after surgery. The cross-section images were reconstructed using first the full set of projection images and afterwards reducing them in number to a quarter and one-sixth (248, 62, 42 projection images, respectively). For both reconstruction methods, similar changes in morphometric parameters were observed over time: bone loss for OVX and bone growth for sham-operated rats, although for DART the actual values were systematically higher (bone volume fraction) or lower (structure model index) compared to FBP, depending on the morphometric parameter. The DART algorithm was, however, more robust when using fewer projection images, where the standard FBP reconstruction was more prone to noise, showing a significantly bigger deviation from the morphometric parameters obtained using all projection images. This study supports the use of DART as a potential alternative method to FBP in X-ray micro-CT animal studies, in particular, when the number of projections has to be drastically minimized, which directly reduces scanning time and dose.
本研究旨在评估离散代数重建技术（DART）用于体内小动物骨骼研究的可行性。离散断层扫描的优势在于有可能减少X射线投影图像的数量，这使得扫描速度更快，同时也意味着辐射剂量的显著降低，且不影响重建结果。由于图像中包含的衰减系数相对较少（即三种：背景（空气）、软组织和骨骼），骨骼研究非常适合采用离散断层扫描。本文通过比较使用DART和常用的标准滤波反投影（FBP）获得的图像计算得到的小梁骨形态计量学参数进行了验证。将雌性大鼠分为去卵巢（OVX）组和假手术组。在基线以及术后2、4、8和12周对胫骨进行体内微型CT扫描。首先使用全套投影图像重建横截面图像，然后将其数量减少到四分之一和六分之一（分别为248、62、42幅投影图像）。对于两种重建方法，随着时间的推移观察到形态计量学参数有相似的变化：OVX大鼠出现骨质流失，假手术大鼠出现骨质生长，尽管对于DART，根据形态计量学参数的不同，其实际值与FBP相比系统地更高（骨体积分数）或更低（结构模型指数）。然而，当使用较少投影图像时，DART算法更稳健，而标准FBP重建更容易受到噪声影响，与使用所有投影图像获得的形态计量学参数相比，偏差明显更大。本研究支持在X射线微型CT动物研究中，将DART作为FBP的一种潜在替代方法，特别是当投影数量必须大幅减少时，这直接减少了扫描时间和剂量。
