Investigation of spatio-temporal tissue changes in an osteoporotic rat model related to activity and hormone replacement therapy with in vivo micro computed tomography using 4D-imaging

骨质疏松症被描述为骨骼组成和分解之间平衡的病理改变，导致骨质量逐渐下降，增加骨折的易感性。骨质疏松症的早期诊断是困难的，因为骨组织的变化开始时没有迹象，通常会在目前的骨折中发现。个体和交叉联系的方面，如骨负荷和预防性激素替代治疗的妇女可能会影响骨质疏松症的起源和进展。在上述方面研究人体组织变化的个体进展的分析技术是有限的。使用体内微计算机断层扫描（in vivoµCT），可以使用中等照射时间以高空间分辨率可视化矿化骨组织。本项目目的是利用延时体内微CT研究骨质疏松大鼠模型胫骨骨与周围组织的变化。小骨变化的可视化和分析将通过连续3D图像的叠加来实现。该动物模型内的时间依赖性变化与动物的年龄、个体运动和激素治疗有关。为了监测笼中动物的运动，将研究一种新的实验装置。因此，无线微型计步器将被固定在动物身上，用于实时测量它们的运动。转动控制转向架轮子将被放置在选定动物群体的笼子中，以研究运动刺激的影响。周围软组织的状况和胫骨的血管化也可能与骨质疏松症的发生有关。因此，在使用造影剂的体内微CT中，将分析胫骨的三维血管生成。对于组织外植体，将测试和分析提高微CT软组织可视化的造影剂。此外，在重建的微CT图像中，与低吸收组织的对比度增强相关的是，不同的正弦图滤波算法将被研究，目的是全面提高软组织值的信噪比。

Osteoporosis is described as a pathological change of the balance between composition and decomposition of bone, which lead to a gradual lose of bone quality up to an increased susceptibility for fractures. An early diagnosis of an osteoporotic disease is difficult, as the bone tissue changes start without indications and will usually be found during a present fracture. Individual and cross-linked aspects like bone loading and a precautionary hormone replacement therapy for women may influence the origin and the progress of the osteoporosis. The analytical techniques to investigate the individual progress of tissue changes under the described aspects in man are limited.With in vivo micro-computed tomography (in vivo µCT) mineralised bone tissue can be visualised with high spatial resolution using moderate irradiation times. Aim of the project is the investigation of tibia bone changes with the surrounding tissue in an osteoporotic rat model with time-lapse in vivo µCT. The visualisation and analysis of small bone changes will be realised with the overlay of sequential 3D images. The time dependant changes within this animal model will be relate to age, individual movement and hormone therapy of the animals. To monitor the movement of the animals during cage housing a new experimental set-up will be investigated. Therefore wireless miniature pedometers will be fixed on the animals for real-time measurement of their movement. Rotation controlled bogie wheels will be placed in the cages of selected animal groups to study the influence of a movement stimulation.The condition of the surrounded soft tissue and the vascularisation of the tibia could also be related to the development of osteoporosis. Therefore the three-dimensional angiogenesis of the tibia will be analysed during the in vivo µCT with the use of contrast agents. For tissue explants contrast agents, which improve the soft tissue visualisation for µCT, will be tested and analysed. Also related to the contrast enhancement of lower absorbing tissue within reconstructed µCT images different sinogramm filter algorithms will be investigated with the aim of an overall improvement of the signal-to-noise ratio for soft tissue values.