Study On The Method Of Orbital Volume Measurement

Orbit is two bone cavity positioned on both sides of maxillofacial perpendicular bisector and accommodates the eyeballs and accessory structures and it is a complex structure of small, irregular shape and has an important role in protecting the eyes. Orbital trauma and orbital tumor are likely to change the orbital volume. Usually, the surgeon judges and roughly estimates the location and quantity of implants based on the preoperative imaging check result and their clinical experience. Due to the complexity of the orbital structure, it is difficult to achieve the desired effect after the surgery. Therefore, the accurate measurement of orbital volume has important guiding significance in the estimation of filler after an orbital tumors removal and the repair of end ophthalmos caused by orbital bone resection.At present, the two main method of orbital volume measurement are physical filling measurement and spiral CT measurement. In this paper, the advantages and disadvantages of the two measurement methods was studied and analyzed. Besides, the author has established a convenient, fast, high repeatable, high precise orbital measurement method. The main method is to scan the orbital region by64slice spiral CT to obtain the raw CT data and to use Mimics10.01software for image filtering, segmentation and reconstruction to obtain the3D orbital image. On this basis, we combine with the reverse engineering software Geomagic Studiol2.0to mark the orbital feature points, extract the inner surface of orbit and fill it, finally establish the projection plane to realize the orbital volume measurement. In our paper, we choice10adult cadaveric heads,6males,4females, aged19～43years old, average age30.5years old,and carry on5times of repeated measurement on left and right orbit of5cadaveric heads and then calculate variance to prove the method of Repeatability. We use the physical filling method to measure20orbits, and the results are served as a control group, we calculate the error and precision of measuring results to verify the accuracy of the new method we prosed and spiral CT measurement.Based on the experiment, the variances of left and right orbit of5cadaveric heads are in the range of0.0018～0.0031. Comparing the physical filling measurement group, the spiral CT measurement of result error of measurement is-3.16%～3.60%, and accuracy of measurement is1.31%～3.60%,the new method of result error of measurement is-0.83%～2.58%, accuracy of measurement is0.09%～2.58%.According to the experimental results, the method proposed in this paper has the characteristics of the repeatability and high precision.