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

骨质疏松症是指骨的组成和分解之间平衡的病理变化，其导致骨质量逐渐丧失，直至增加骨折的易感性。早期诊断骨质疏松性疾病是困难的，因为骨组织的变化开始时没有迹象，通常会发现在目前的骨折。个体和交叉方面，如骨负荷和预防性激素替代疗法可能会影响骨质疏松症的起源和进展。在所述方面，研究人体组织变化的个体进展的分析技术是有限的。通过体内微型计算机断层扫描（体内µCT），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。该项目的目的是通过延时体内µCT研究骨质疏松大鼠模型中胫骨与周围组织的变化。将通过叠加连续3D图像实现小骨变化的可视化和分析。该动物模型中的时间依赖性变化将与动物的年龄、个体运动和激素治疗有关。为了监测动物在笼舍饲养期间的运动，将研究新的实验装置。因此，无线微型计步器将被固定在动物身上，以实时测量它们的运动。将旋转控制的转向轮放置在选定动物组的笼中，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展有关。因此，将在使用造影剂的体内µCT期间分析胫骨的三维血管生成。对于组织外植体，将对造影剂进行测试和分析，造影剂可改善µCT的软组织可视化。此外，与重建µCT图像内低吸收组织的对比度增强相关，将研究不同的sinogramm滤波器算法，目的是全面改善软组织值的信噪比。

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.