Volumetric Registration-Based Cleft Volume Estimation of Alveolar Cleft Grafting Procedures

This paper presents a method for automatic estimation of the bony alveolar cleft volume of cleft lips and palates (CLP) patients from cone-beam computed tomography (CBCT) images via a fully convolutional neural network. The core of this method is the partial nonrigid registration of the CLP CBCT image with the incomplete maxilla and the template with the complete maxilla. We build our model on the 3D U-Net and parameterize the nonlinear mapping from the one-channel intensity CBCT image to six-channel inverse deformation vector fields (DVF). We enforce the partial maxillary registration using an adaptive irregular mask regarding the cleft in the registration process. When given inverse DVFs, the deformed template combined with volumetric Boolean operators are used to compute the cleft volume. To avoid the rough and inaccurate reconstructed cleft surface, we introduce an additional cleft shape constraint to fine-tune the parameters of the registration neural networks. The proposed method is applied to clinically-obtained CBCT images of CLP patients. The qualitative and quantitative experiments demonstrate the effectiveness and efficiency of our method in the volume completion and the bony cleft volume estimation compared with the state-of-the-art.