Calculation of skull thickness from brain MRI data

This thesis study includes three different methods that can automatically calculate the skull bone thickness map from 3-D MRI data regardless of age and gender. These methods are thermal heat, vertical ray and vertical ray based geodesic curve methods. The thermal heat method is based on the principle of diffusion of heat on the body. Accordingly, the inner surface of the skull is adjusted to 0°C and the heat is propagated. After the propagation, the amount of temperature on the outer surface of the skull is measured and the internal-external temperature difference is proportional to the bone thickness value. In determining this ratio, calibration is performed using reference points of known thickness. The vertical ray method is based on the principle of propagation of light. First, the skull is converted into a large mesh structure consisting of triangles. Since the computational cost will be high in this mesh with millions of nodes, the number of nodes is reduced by fusing techniques. The vertical vectors descending from each node to the skull are calculated and the ray is sent in the opposite direction. The distance between the first point where the light comes out of the bone and the starting point gives the bone thickness. Finally, a vertical ray based geodesic curve approach is proposed to reduce the computational cost of the vertical ray method. In this method, 23 landmarks are placed at certain points of the skull. In the next step, the geodesic curves connecting the markers are calculated. The thickness of the points on the curves is calculated by the vertical ray method. In the last stage, the thickness values of other points are calculated with the regression technique. Scientific works are produced from bone thickness calculation methods developed by using MRI data obtained from Fırat University Hospital, Department of Neurosurgery.