Accuracy and reproducibility of automatic versus manual registration using a cone-beam CT image guidance system

Intraoperative imaging reveals morphologic changes and resolves anatomic uncertainties during surgery. The automatic registration (AR) approach provides registered intraoperative images for real-time tracking within seconds of acquisition.

(1) To design an AR device for clinical use integrated with cone-beam computed tomography, (2) to compare the accuracy and reproducibility of manual and automatic registration, and (3) to evaluate the robustness of the AR system.

An AR device consisting of an acrylic face shield with fiducials mounted on an adjustable arm was designed. Eight surface and five internal divot markers were placed with bony fixation to a cadaveric head. Internal markers were localized on the image representing the "true" location. This was compared to the positions localized using a navigational system when both manual registration and AR were applied. A series of surgical tasks and variation of the AR device height above the surgical field was performed, and target registration error (TRE) was measured.

The mean fiducial registration error (FRE) for manual and automatic registration was 0.72 mm ± 0.03 and 0.41 mm ± 0.01, respectively. The mean TRE for manual and automatic registration was 0.89 mm ± 0.26 and 0.91 mm ± 0.25, respectively.

AR offers a more accurate and reproducible FRE and a TRE equally comparable to that of manual registration. This system also demonstrates robustness with comparable accuracy and reproducibility throughout different surgical tasks and variation of AR device height up to 9 cm above the surgical field. This system is currently being translated into clinical trials.