An Approach to Extraction Midsagittal Plane of Skull From Brain CT Images for Oral and Maxillofacial Surgery

To prepare for the oral and maxillofacial surgery for the facial symmetry of patients, midsagittal plane of skull in brain computed tomography (CT) images is calculated with points manually chosen from skull by doctor. But the extracted midsagittal plane of the skull is different by different doctor. Even the extracted midsagittal plane of the same patient is also different by the same doctor in different times. The manually extracting operation usually takes a long time to increase the doctor's workload. Aimed at this problem, a semi-automatic extracting method for midsagittal plane of skull is proposed in this paper. First, the brain tissue is extracted by region growing method and the oriented bounding box (OBB) of the brain tissue is built. Second, the middle symmetry plane of the OBB of brain tissue is extracted as the initial midsagittal plane, which is updated by the mathematical translation and rotation method. Finally, the symmetrical characteristic of the brain tissue based on the updated symmetry plane is calculated by the mutual information method. This procedure is executed iteratively until the symmetrical characteristic of the brain tissue based on the new symmetry plane is no more different from the previous result. The final extracted symmetry plane is the midsagittal plane of skull in brain CT images of the patient. The midsagittal plane which is extracted manually by doctor is used to compare and evaluate the accuracy of this semi-automatic extracting symmetry plane method. The experimental results from both qualitative and quantitative analyses showed that the method can reach or approach the accuracy of manual extracted, but the stable level of this method is significantly higher than the manual method and this method can shorten the operate time to reduce the doctor's workload.