Quality evaluation of spiral CT-directed skull base coordinate assignment using the Leibinger 'Z-D' frame and 'STP' software

We employed a phantom model to evaluate the accuracy and precision of spiral CT-directed intracranial skull base coordinate assignment using the Leibinger 'ZD' frame and 'stp' stereotactic software. Whilst the difference between the true and computed coordinates was in the perimillimeter range for anteroposterior, lateral and vertical measurements in a 1-mm slice thickness series of scans, errors of greater than 4 mm were encountered in 60% of vertical measurements in a 2-mm slice thickness series. Potential explanations for this clinically significant observation are discussed.