目的对MRI-UTE序列图像中的牙齿进行有效的分割。方法建立分层约束的二次分割算法流程。首先用水平集方法从用户在参考层中选定的区域内分割出牙齿边界；然后将已分割区域的信息作为下一层分割的约束，用水平集方法将边界向牙冠和牙根两个方向逐层演化；最后将相邻两层的分割结果作为约束，以重叠指数作为演化方程中的参数逐层进行二次分割以矫正结果。结果首次分割平均准确率为86.98%，二次分割后的准确率显著提高至88.35%，与其他两种方法相比改善效果具有统计学意义(P<0.05)。结论上述算法流程能有效应用于牙齿MRI-UTE序列图像的分割，在准确性上有了较大的改进。%Objective To introduce algorithms for effective segmentation of teeth MRI-UTE image. Methods To contruct second-segmentation algorithm process based on layer-dependent multi-constrained method. Firstly, a level set method was used to segment the initial boundary from the region determined by user in the reference slice. Secondly, both crown and root of the tooth were segmented by the improved level set method which took the information of the former layer's result as constraint conditions. Final y, the improved level set based on the information of the former and later layer’s results was executed for the second time to improve the accuracy of segmentation, in which, the parameter of the overlapping ratio was considered. Results The accuracy was 86.98% for the first-segmentation and was increased to 88.35% for the second-segmentation. Compared to the two other methods, the accuracy of the algorithms provided was improved significantly (P<0.05). Conclusions The proposed algorithms can effectively achieve the segmentation of teeth MRI-UTE image and has a great improvement on accuracy.
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