A Novel Mobile C-Arm Fluoroscopic Imaging of the Foramen Ovale and Its Anatomical Principles

Accurate localization of the foramen ovale (FO) is essential for percutaneous balloon compression, radiofrequency thermocoagulation, and glycerol injection in the treatment of trigeminal neuralgia. The mobile C-arm X-ray system is widely used due to its accessibility and low radiation exposure, but achieving optimal positioning to visualize the FO remains challenging. We propose a novel approach using facial surface landmarks to guide rapid and accurate C-arm positioning for FO fluoroscopy.

Patients were placed in the supine position, and three anatomical reference points were identified: Point A (subnasale), marked with a metal marker, and Points B and C (the intersections of the lateral orbital margins and the superior extensions of the zygomatic arches bilaterally), marked with surgical ink. With the X-ray tube of the C-arm centered above the face, the device was rotated along the transverse axis toward the foot end until Points A, B, and C appeared collinear from the tube's eye view. Fluoroscopy was then used to confirm alignment of Point A with the line connecting the outermost points of the bilateral infraorbital margins. Finally, the tube was tilted 20-25° toward the puncture side along its curved rail to visualize the FO. This method was validated through virtual simulation, intraoperative fluoroscopy, and 3D anatomical modeling.

Clear FO images were obtained without additional adjustment in 170 of 200 simulated cases (85.0%) and in 28 of 30 intraoperative cases (93.3%). Simulated imaging showed excellent agreement with the actual osseous FO (Kappa = 0.96, p < 0.001; sensitivity = 0.99; specificity = 1.00), and intraoperative imaging demonstrated perfect agreement with the simulation (Kappa = 1.00, p < 0.001).

This technique provides reliable and accurate FO visualization, with excellent agreement between simulated, osseous, and intraoperative imaging. By simplifying the fluoroscopic process, this approach reduces the number of X-ray exposures required, thereby decreasing patient radiation exposure and shortening procedural time.