Two and three dimensional measurements of the skull base bone using high-resolution volumetric CT

Fifty-two normal human subjects (male 26, female 26) were examined with a HITACHI W-3000 volumetric CT scanner. CT was performed with a slice width of 2 mm, a sliding speed of 2 mm/sec and a scanning time of 30 sec. The subjects were scanned in an axial plane parallel to the OM (orbitomeatal) line from the foramen magnum to the rostrum [60 mm]. These date were reconstructed using 59 slices of the bone-window level 2D-CT image (WW3400, WL240) every 1 mm of pitch and measured distances of important landmarks and angles (foramen ovale, carotid canal, lateral semicircular canal, optic canal). 3D-CT displays were derived from the 2D-CT image information using a threshold of 180 H.U.. And measurements of the distances of important landmarks (anterior clinoid process, pterion, internal acoustic meatus, posterior zygomatic process). The 2D-CT measurements of distance were extremely close to the reported anatomical measurements. On the other hand, the 3D-CT measurements were a little larger over all than those measurements. Statistically, the left side diameter of the carotid canal was greater than the right (p<0.05). And the right side length of the foramen ovale was longer than the left (p<0.001). In addition, the length of the cranial bone was correlated with its height (r=0.56, p<0.0001). Similarly, the distance from the sigmoid sinus to the acoustic meatus was correlated with the distance from the sigmoid sinus to the posterior semicircular canal (r=0.75, p<0.0001). The present studies revealed that the skull base measurements obtained with high-resolution volumetric CT were accurate. In addition, this method was easy, rapid, unrestricted and capable of continuous and repeated examination of an object. Therefore measurements made by such this efficient CT technique can be aid to skull base surgery. (H.O.). 57 refs