The SSD technique begins by choosing a threshold value, and then geometric primitives are automatically fit to the high-contrast contours in the volume that match the threshold. Cells whose values are all above the chosen threshold(cell is inside) or all below the threshold(cell is outside) are discarded and have no effect on the final image. Rendering just the cells falling on the threshold is sometimes useful, but can cause overestimation or underestimation in the examination of RAS. Theoretically, the MIP technique will be less affected by reduced CT density in vessels because it does not use a lower threshold to exclude structures from the reconstructed image. However, MIP technique still suffers from several problems. For these reasons, 3D texture mapping, in which it is not necessary to choose a threshold, and which retains complete volume data, could be the answer for these problems.