关节置换术中计算机导航图像注册与图像漂移的实验研究

An experimental research on image registration and image shift in computer-navigated total hip arthroplasty

目的探讨计算机导航全髋关节置换术中图像注册精确度对图像漂移的影响。方法基于CT图像的计算机导航方式，采取配对点进行图像注册，应用偏离配对点10mm注册的形式来模拟实际应用中图像漂移的发生；通过面重建一即应用带有红外线反射球的指示器对真性骨盆臼窝表面均匀的描画，使红外线摄像器持续捕捉指示器触头运动轨迹信号，从而重构出髋臼窝的真实对应影像，以此真实对应影像为标准来评估漂移像于臼窝处的漂移程度。结果髋臼窝表面110个观察点，漂移距离值为-7．50～22．86mm，点漂移距离小于5mm者，占32．7％；大于5mm而小于10mm者，占20．9％；漂移像与以面成像的髋臼窝表面重叠面积仅43．7％。结论在配对点图像注册的方式中，即使配对点注册标定时偏离轻微，也会导致髋臼窝处图像的明显漂移，对臼杯置入的定位造成较大的影响。为提高定位的精确性可考虑结合臼窝面重建的方式来获取骨床的空间信息。

Objective To explore the influence of image registration on image shift in computernavigated total hip arthroplasty. Methods In CT image-based navigation, image registration was carried out by using point matching system. In our research, the image shift was simulated in application through a 10mm deviating matched-point registration. The indicator with an infrared reflector pictured the surface of true acetabulum equably so that the infrared cameras of navigation can continuously captured the signals of the movement track of the contactor and reconstruct the associated image of the true acetabulum which is called surface-reconstructed image. This surface-reconstructed image is used as standard for evaluating the extent of image shift. Results The deviation values of 110 watch points on the acetabular surface range from -7.50 mm to 22. 86 mm, with 32. 7% of the values lesser than 5 mm, 20. 9% greater than 5mm but lesser than 10mm; The overlap area percentage of shifting image and surface-reconstructed area is merely 43.7%. Conclusions In point matching registration, a slight point departure will lead to evident image shift which significantly affects the implantation of acetabular cup. Therefore, to improve the accuracy of cup implantation, it is recommended to use surface-reconstructed image to obtain the data of aeetabulum.