  Abstract. Purpose: This paper presents a scheme for generating virtual
intraoperative CT scans in order to improve surgical completeness in Endoscopic
Sinus Surgeries (ESS). Approach: The work presents three methods, the tip
motion-based, the tip trajectory-based, and the instrument based, along with
non-parametric smoothing and Gaussian Process Regression, for virtual
intraoperative CT generation. Results: The proposed methods studied and
compared on ESS performed on cadavers. Surgical results show all three methods
improve the Dice Similarity Coefficients > 86%, with F-score > 92% and
precision > 89.91%. The tip trajectory-based method was found to have best
performance and reached 96.87% precision in surgical completeness evaluation.
Conclusions: This work demonstrated that virtual intraoperative CT scans
improves the consistency between the actual surgical scene and the reference
model, and improves surgical completeness in ESS. Comparing with actual
intraoperative CT scans, the proposed scheme has no impact on existing surgical
protocols, does not require extra hardware other than the one is already
available in most ESS overcome the high costs, the repeated radiation, and the
elongated anesthesia caused by actual intraoperative CTs, and is practical in
ESS.
