positive finding with 358 elevation of the both lower legs c absence of ankle jerk d sensory loss in the s1 dermatome and e positive finding of low back pain on lateral bending of the right leg these findings were indicative of lumbar hivd on both sides at l5 s1 with greater severity on the right side two transverse sections for resolving l5 s1 were obtained and segmented as disc substance boundaries as illustrated in fig8 a and b in the two analyzed ct transverse sections black lines are boundaries of the disc substance and white points are the centers of disc boundaries while white lines are interpolated boundaries approximate normal boundaries of the disc substances for the herniation features and solid arrows are extrusion features at the boundary of the superior section necking was seen at both sides of the herniation hollow arrows in fig8 a therefore the 2d feature can be classified as an extrusion at the boundary of the inferior section although no clear necking was seen on both sides of the herniation fig8 b the 2d feature should be classified as an extrusion the largest herniation ratio was large enough and the herniation radius changed rapidly at both sides of the herniation to become necking thus this l5 s1 space was classified as a disc extrusion based on the combined information in the two sections in addition the two sections both revealed that the hivd was right lateral however because the herniation radii of the angular positions near the cord and the left root were relatively large total laminectomy.